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HomeMy WebLinkAboutRevised SWM Report dated 2026-04-30 Stormwater Management Report for Homes at Centerville Cove 195 Phinney’s Lane Centerville, Massachusetts Prepared for: Great Marsh Development LLC 116 Flanders Road, Suite 3000 Westborough, MA 01581 April 30, 2026 BAXTER NYE ENGINEERING & SURVEYING Registered Professional Engineers, Land Surveyors & Scientists 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 1 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com PROJECT STATEMENT PROJECT: Homes at Centerville Cove LOCATION: 195 Phinney’s Lane, Centerville, MA BN JOB NUMBER: 2020-015 CLIENT: Great Marsh Development LLC . SUBJECT: Stormwater Management & Drainage Calculations OBJECTIVES: 1) Meet the objectives of the Barnstable Zoning Ordinance & MA DEP SWM Policy (a) Evaluate the pre-development conditions and calculate the peak rate of runoff. (b) Evaluate the post-development conditions and provide stormwater management and treatment to prevent any increase in the 2, 10, 25 and 100 year storms, from the pre-development conditions peak discharge at the site study point. (c) Safely pass the 100 year storm event without causing any downstream detrimental impact. (d) Provide for Water Quality Treatment for the first flush 1” of rainfall (in Critical Area – Zone II Recharge Area) in accordance with MDEP SWM Policy and Barnstable Zoning Ordinance SWM Regulations. (e) Provide for Groundwater Recharge in accordance with MDEP SWM Policy. CALCULATION METHODS & DESIGN STORMS: 1) Soil information was taken from the SCS Soil Survey of Barnstable County. Field analysis of the soils was performed as identified herein. 2) Subcatchment areas, flow paths, and design points were delineated using standard engineering practice. 3) The existing and proposed conditions were modeled using HydroCAD, which incorporates the methodologies of SCS TR-55 and TR-20. 4) The proposed stormwater management system was designed to control the 2, 10, and 25-year storm event using the SCS TR-20 Method. The 100-year storm event will pass safely through the system with no detrimental impact to downstream areas. 5) Private closed storm drain systems shall be sized for the 10 year storm event. Inlets and curb openings shall be analyzed for the 10 year storm event. All storm drain calculations will use the rational method. 6) Ditch and channel flow shall be analyzed for the 10 year storm event. Ditch and channel flow around buildings shall be analyzed for the 100 year event. Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 2 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com PROJECT NARRATIVE The subject site area for the proposed construction of 36 single-family homes is located at 195 Phinney’s Lane in Centerville, MA, consisting of 6.76 acres of predominantly wooded land. The majo0irty of the site lies in Zoning District RC, with a small area located in Zoning District RD-1, and a minor area lies within Zoning District HO. The existing use of the parcel is largely undeveloped wooded land, with two small houses proposed to be demolished, and one small single-family house to remain. The proposed project will consist of subdividing the property into 36 single-family home lots, and the construction of approximately 1,430 linear feet of roadway tp service the 35 new subdivided lots. One existing house, addressed as 40 Richardson Road, will remain, with it’s access off of Richardson Road. There are no wetlands nor buffer zones to wetlands on the site, nor any land subject to flooding. There are also no estimated or priority habitats of rare species, as mapped by National Heritage Endangered Speicies Program. The proposed stormwater management systems (SMS) will be installed to control stormwater runoff for water quality and quantity in accordance with MDEP SWM Policy. The SMS will also have a significant net benefit to the property over the existing conditions. Since, under the existing conditions, no SMS exists, and therefore, there has been no control of water quality and quantity being discharged from the site. Under the proposed conditions, both stormwater quantity and quality are controlled. The post-development peak storm discharges are reduced to zero for the 2, 10, 25 and 100 year storm events. The post- development water quality is enhanced through the SMS which provides an 89% total suspended solid (TSS) removal rate (see SWM Narrative for additional information). The water recharge of the site be affected positively, as it will receive the same volume of runoff, but at attenuated peaks. Thereby, reducing velocities and erosion. Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts i | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com TABLE OF CONTENTS INTRODUCTION ........................................................................................................................................... 1 METHODOLOGY & ANALYSIS .................................................................................................................... 1 Hydrology and Hydraulics.......................................................................................................................... 1 Assumptions .............................................................................................................................................. 2 DRAINAGE DESIGN CONDITIONS ............................................................................................................. 4 Pre-Development Conditions:.................................................................................................................... 4 Post-Development Conditions: .................................................................................................................. 4 Proposed Drainage Facilities..................................................................................................................... 4 SUMMARY .................................................................................................................................................... 6 TABLE 1: PEAK DISCHARGE AND VOLUME RELEASE ...................................................................... 7 LIST OF FIGURES FIGURE 1 Site Location: U.S. Geological Quadrangle and Street Atlas FIGURE 2 Pre Development Drainage Areas Plan FIGURE 3 Post Development Drainage Areas Plan SOIL SURVEY MAPS AND MAP UNITS CLASSIFICATION AND DESCRIPTION OF SOILS ON SITE TEST PIT SOIL LOGS APPENDIX B: HYDROLOGIC INFORMATION RAINFALL DATA MAPS APPENDIX C: PRE-DEVELOPMENT WATERSHED RUNOFF & ROUTING APPENDIX D: POST- DEVELOPMENT WATERSHED RUNOFF & ROUTING APPENDIX E: GROUNDWATER RECHARGE & WATER QUALITY GROUNDWATER RECHARGE VOLUME CALCULATIONS WATER QUALITY TREATMENT VOLUME CALCULATIONS TSS REMOVAL CALCULATION WORKSHEET Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 1 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com INTRODUCTION Baxter Nye Engineering & Surveying (BN) performed a Stormwater Management (SWM) analysis of the subject site to evaluate the post-development impacts associated with the proposed development. The hydrology for both the pre and post development drainage areas was analyzed to determine the impact of development. SCS TR-55 and HydroCAD Stormwater Modeling System were used to model the site for existing and proposed conditions and the associated runoffs. HydroCAD utilizes the SCS TR20 Method to determine peak rates of runoff, which were computed and compared to the existing conditions. BN designed a system for storm runoff collection and management using BMP’s (Best Management Practices) as defined by MDEP. The collection and conveyance system is comprised of Cape Cod berms on road edges to direct stormwater to hooded sump catch basins and water quality inlets. The stormwater collection systems discharge to sediment forebays or water quality inlet, and stormwater is then conveyed to retention areas or leaching basins which infiltrate stormwater into the ground surface. METHODOLOGY & ANALYSIS Hydrology and Hydraulics Drainage calculations are performed to demonstrate that there is no increase in the rate of runoff (and therefore, no increase in downstream flooding) from the subject site due to the proposed improvements. The rate of runoff is compared at a common point referred to as the design point of interest, for both the pre and post development conditions.. The hydrologic and hydraulic model created to analyze the pre and post development condition was developed using the Soil Conservation Service (SCS) Technical Release No. 20 (TR 20, SCS unit hydrograph procedures), SCS Technical Release No. 55 (TR 55, Time of Concentration (Tc) and Curve Number (CN)), NOAA Atlas 14 Point Precipitation Frequency Estimates (for rainfall intensity), and the stormwater retention facilities were modeled using the SCS Storage Indication Method. Time of Concentration (Tc) is the time required for stormwater runoff to travel from the most hydraulically distant point in a drainage area or subcatchment to the design point. The Tc is calculated based upon Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 2 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com slope, distance, surface cover and type of flow. A longer time of concentration will generally result in a smaller rate of runoff. The Curve Number (CN) represents the amount of runoff expected from a particular segment of the drainage area. A higher curve number represents a more impervious surface and hence will have a larger rate of runoff. The CN is based upon three characteristics: (1) The Hydrologic Soil Group (HSG) A, B, C, or D; A is the most infiltratable and has the lowest runoff potential, D is the least infiltratable and has the highest runoff potential; (2) The soil cover (vegetated, developed, farmland or impervious); impervious cover obviously having the highest runoff potential. The final factor is the condition of the surface cover, being classified as good, fair or poor; surface cover in good condition has the lowest runoff potential. The soil types for the drainage areas were determined from the Soil Conservation Service Soil Survey for the appropriate area where the project is located. The soil survey contains maps, which delineate the extent of the various soil types and their characteristics. Soil mapping for this site shows Carver loamy coarse sands and east chop loamy fine sands. To assist in the analysis, software entitled HydroCAD, (developed by Applied Microcomputer Systems) was utilized. The HydroCAD program calculates the runoff based on rainfall and watershed characteristics and produces a runoff hydrograph (a runoff rate versus time curve). Then the stage-storage-discharge curves for a specific SWM facility are calculated. The stage-storage-discharge curves are a set of curves for a specific SWM facility that depict the outflow from the outlet control structure versus the volume of runoff stored in the facility. The stage-storage-discharge curves are used to compute an outflow hydrograph by hydraulically routing an inflow hydrograph through the detention facility. The peak rates of runoff, at the design points, were calculated for the pre and post development conditions for the design storm events with Type III – 24 hour rainfall distribution. The peak rate of runoff was compared for each required design storm event to confirm that there was no increase from the pre to post development conditions for the required storm events. Volumes were analyzed as well for comparison of pre to post-development levels. The “Discarded” number represented in the HydroCad/TR-20 Outputs represents the rate and volume of runoff, which is infiltrated into the ground through the bottom of the basin. Assumptions 1) Shallow concentrated flow occurs at a maximum of 300 feet. If the slope is greater than two percent (2%), shallow concentrated flow occurs at a maximum of 200 feet. This is based on an assumed drainage area of several hundred acres. Smaller drainage areas should have their shallow concentrated flow occurrence adjusted to a lesser distance accordingly. Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 3 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com 2) The minimum time of concentration (tc) value used shall be five (5) minutes. 3) Rainfall distribution is even over the drainage areas to be analyzed for a given storm event. 4) Base flow contribution has a negligible affect on the peak discharge. 5) Flows are steady, turbulent, and uniform. 6) Fluids are incompressible. Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 4 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com DRAINAGE DESIGN CONDITIONS The runoff for the pre-development condition was calculated for the 2, 10, 25 and 100-year storm events. The runoffs for post development conditions, routed through the stormwater management facilities, were calculated for the 2, 10, 25 and 100-year storm events. The pre and post development rates of runoff were compared for each storm event. The SWM facilities were designed to control the post-development rates of runoff at the point of study to equal to or less than their pre-development levels for the required storms. Pre-Development Conditions: The subject site area for the proposed construction of the subdivision roadways is located at 195 Phinney’s Lane, in Centerville, MA, consisting of 6.76 acres. The existing use of the parcel is mostly undeveloped wooded land, with three existing small single-family homes. The parcels are currently occupied by three houses, two of which are proposed to be demolished. The SCS Soil Surveys Soil Map Units from the Barnstable County Soil Survey for the site area, indicate that the predominant soils on site where development is to occur are Carver loamy coarse sand, and East Chop loamy fine sand. Test pits performed on March 31, 2017 revealed sand and gravel, and stratified medium coarse sand soils existing at the site. Groundwater was approximately 10 feet below the surface. The soil materials are classified as a Hydrologic Soil Group A, and suitable for infiltration. The existing ground cover on the subject site is mainly woods, with scrub pine and scrub oak the predominant tree types. impervious surfaces at the site are minimal, consisting solely of the roofs of 3 small houses and their associated driveways. The existing and proposed drainage areas were compiled from an existing topographic survey completed by this office. Drainage at the site currently flows to several low points throughout the site that act as ponds with no outlets. Post-Development Conditions: The proposed project will consist of the construction of approximately 1430 linear feet of paved roadway, 20 feet wide with Cape Cod berms of each side of the roadway to direct water to site catch basins. The roadway right of ways will be finished with grass shoulders and sideslopes. Proposed Drainage Facilities Baxter Nye Engineering designed systems for storm runoff collection and management using BMP’s (Best Management Practices) as defined by MDEP. The collection and conveyance system is comprised of Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 5 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com hooded deep sump catch basins, corrugated plastic pipe, water quality inlet or sediment forebays, and surface retention basins or underground infiltration basins. The catch basins, water quality inlet, and sediment forebays will separate gas, oil and heavy particulates from the runoff. The sediment forebays will attenuate runoff, assist in removing suspended solids and allow for nitrogen uptake through the vegetation. The stormwater collection systems discharge to two open-air retention basins, or two underground infiltration systems consisting of leach basins with stone surround. The drainage facilities are sized to retain the runoff for the 2, 10, 25 and 100-year storm events. Therefore, there is no flooding impact to downstream areas. The proposed stormwater management system (SMS) will be installed to control stormwater runoff for water quality and quantity in accordance with MDEP SWM Policy. The SMS will also have a significant net benefit to the property over the existing conditions. Since, under the existing conditions, no SMS exists, and therefore, there has been no control of water quality and quantity being discharged from the site. The rate of infiltration used in the analysis of these facilities is 2.41 inches per hour for the grass surface retention basins, and 8.27 inches per hour for underground infiltration structures set in good sand soils. These rates are entered into HydroCad in the format of velocity (in/hour) or flow rate (cfs – which is obtained by applying the velocity – or infiltration rate - over the infiltratable area of the SWM facility). Each single-family house proposed will have a leaching basin adjacent to the building to handle all roof runoff from the 100-year storm event. All the runoff from the roof (impervious area) is captured and conveyed directly to the underground leaching basin, where the water infiltrates into the surrounding ground. Under the proposed conditions, both stormwater quantity and quality are controlled. The post-development peak storm discharges are reduced to zero for the 2, 10, 25 and 100 year storm events. The Water Quality Volume (see Appendix F) is treated through multiple in line BMP’s. Hooded Sump Catch Basins, with a sump of 4 ft. are provided for pretreatment. The runoff is then conveyed through a water quality inlet or sediment forebay prior to entering the swm retention facility. The swm retention systems are designed with a sediment forebay or StormFilter 330 water quality inlet to further enhance pollutant removal. All the runoff from the impervious roadway areas passes through these facilities. The combined BMP treatments are designed in accordance with the MDEP sizing requirements. This combination of BMP’s results in the removal of 89% of the initial TSS loading. This exceeds the MDEP requirement of 80%. The Groundwater Recharge Volume required is 0.60 inches of runoff times the impervious area, as the soils are of the HSG A. Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts 6 | P a g e BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com SUMMARY Based on the analysis performed for the 2, 10, 25 and 100-year storm events, the stormwater management facilities are adequately sized to mitigate potential increases in the peak rate of runoff and volume from the site. The post development peak runoff rates and volumes for the entire contributing drainage areas (both “on- site” area and “off-site” area) demonstrates that there is no runoff released from the developed site in the post development condition for the 2, 10, 25, and 100-year storm events This well exceeds the requirements of the Barnstable Zoning Ordinance, which requires control through the 25-year design storm for the on-site runoff. The “Discarded” flows shown within the HydroCAD analysis represent flows and volumes infiltrated directly into the ground through the SWM structures and are not discharged or released over land. Table 1 is a summary of expected release rates based on total contributing drainage areas (both on-site and off-site areas). This table shows the expected post development runoff rates and volumes are reduced to zero from the pre-development levels for the 2, 10, 25 and 100 year storms. The control of the post- development volume to zero mitigates any downstream flooding impacts and provides for significant groundwater recharge. The benefit to the groundwater recharge is greatly enhanced, as shown by the reduction of volume runoff from the site for the 2, 10, 25 and 100-year storm events. Therefore, this demonstrates there is no detrimental impact to downstream areas from the proposed redevelopment of the site. BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com TABLE 1: PEAK DISCHARGE AND VOLUME RELEASE STORM (YEAR) STUDY POINT PRE-DEVELOPMENT STUDY POINT POST DEVELOPMENT PEAK DISCHARGE (cfs) VOLUME (ac-ft) PEAK DISCHARGE (cfs) VOLUME (ac-ft) 2 Low Areas 1, 2, 3, 9 0.00 0.000 SWM 1 0.00 0.000 Low Areas 4, 5, 6, 10 0.00 0.000 SWM 2 0.00 0.000 Low Area 7 Low Area 9 0.00 0.00 0.000 0.000 SWM 3 SWM 4 0.00 0.00 0.000 0.000 SP 8 0.00 0.000 N/A 0.00 0.000 10 Low Areas 1,2,3,9 0.00 0.000 SWM 1 0.00 0.000 Low Areas 4, 5, 6, 10 0.00 0.000 SWM 2 0.00 0.000 Low Area 7 Low Area 9 SP8 0.00 0.00 0.00 0.000 0.000 0.000 SWM 3 SWM 4 N/A 0.00 0.00 0.00 0.000 0.000 0.000 25 Low Areas 1, 2, 3, 9 Low Areas 4, 5, 6, 10 Low Area 7 Low Area 9 SP 8 0.00 0.00 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.001 SWM 1 SWM 2 SWM 3 SWM 4 N/A 0.00 0.00 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com 100 Low Areas 1, 2, 3, 9 Low Areas 4, 5, 6, 10 Low Area 7 Low Area 9 SP 8 0.00 0.00 0.00 0.00 0.01 0.000 0.000 0.000 0.000 0.003 SWM 1 SWM 2 SWM 3 SWM 4 N/A 0.00 0.00 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 Pre-Development drainage areas drain to nine different low areas existing at the site, modeled as ponds, which contain all runoff up to the 100-year storm, with no discharges. A small area of the existing site drains northward to Great Marsh Road and is modeled as Study Point 8. With the installation of the roadways and drainage systems, it is not appropriate to compare these low areas for pre and post-development conditions. Post-Development drainage areas drain to four drainage systems which contain all post-development runoff through the 100-year storm, with no releases from the drainage systems. With the grading of Road 1 to the south from Great Marsh Road right of way line, all the area previously draining to Study Point 8 flows to SWM System #3, so there is no discharge to Great Marsh Road to the north at Study Point #8, therefore those discharges are shown as 0.00 cfs for all storm events. 2020-015 Summary Table.docx Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com FIGURE 1 Site Location: U.S. Geological Quadrangle and Street Atlas Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com FIGURE 2 Pre Development Drainage Plan PHINNEY'S LANE FALMOUTH ROAD / ROUTE 28 GREAT MARSH ROADJUNIPER RDSHEET TITLEDATE:CHECKED BY:JOB NO:DRAWN BY:DESCRIPTIONBYDATEPREPARED FOR:PROJECT TITLESHEET NOSCALE:BAXTER NYEENGINEERING &SURVEYINGGreat Marsh Development, LLC116 Flanders Road, Suite 3000Westborough, MA 01581STAMPCONSULTANTNOFILE:Homes at Centerville Cove195 Phinney's Lane39, 51, 61, & 75 Great Marsh Rd40 Richarson RoadCenterville, MA 02632CONSULTANTSTAMPDA1.0Pre-DevelopmentDrainage Areas PlanO:\2020\2020-015\CIVIL\PLOT\2020-015 DA-PRE.dwg, 4/30/2026 10:14:32 AM, jlavelle, DWG To PDF.pc3, 1:1 Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com FIGURE 3 Post Development Drainage Plan PHINNEY'S LANE FALMOUTH ROAD / ROUTE 28 GREAT MARSH ROADJUNIPER RDSHEET TITLEDATE:CHECKED BY:JOB NO:DRAWN BY:DESCRIPTIONBYDATEPREPARED FOR:PROJECT TITLESHEET NOSCALE:BAXTER NYEENGINEERING &SURVEYINGGreat Marsh Development, LLC116 Flanders Road, Suite 3000Westborough, MA 01581STAMPCONSULTANTNOFILE:Homes at Centerville Cove195 Phinney's Lane39, 51, 61, & 75 Great Marsh Rd40 Richarson RoadCenterville, MA 02632CONSULTANTSTAMPDA2.0Post-DevelopmentDrainage Areas PlanO:\2020\2020-015\CIVIL\PLOT\2020-015 DA-POST.dwg, 4/30/2026 10:13:04 AM, jlavelle, DWG To PDF.pc3, 1:1 Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com APPENDIX A SITE SOIL INFORMATION • SOIL SURVEY MAPS AND MAP UNITS • CLASSIFICATION AND DESCRIPTION OF SOILS ON SITE • TEST PIT SOIL LOGS • HIGH GROUNDWATER LEVEL COMPUTATION Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com SOILS DATA The following Soil Map Units were located on Map Sheet #xx of the ‘WHAT’ County Soil Survey. Based on these map units, a matching soil profile and description were determined. The SCS Soil Survey for the analysis area indicates that the predominant soils are: • Carver loamy coarse cand • Eastchop loamy fine sand See following pages for the soil map and soil description. Soil Map—Barnstable County, Massachusetts (Soil Map-Great Marsh Rd-Phinney's Ln. Centerville) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2025 Page 1 of 3461264046126804612720461276046128004612840461288046129204612960461264046126804612720461276046128004612840461288046129204612960388260388300388340388380388420388460388500 388260 388300 388340 388380 388420 388460 388500 41° 39' 38'' N 70° 20' 31'' W41° 39' 38'' N70° 20' 20'' W41° 39' 27'' N 70° 20' 31'' W41° 39' 27'' N 70° 20' 20'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 19N WGS84 0 50 100 200 300 Feet 0 20 40 80 120 Meters Map Scale: 1:1,640 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:25,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Barnstable County, Massachusetts Survey Area Data: Version 24, Sep 5, 2025 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 10, 2022—Jun 30, 2022 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Barnstable County, Massachusetts (Soil Map-Great Marsh Rd-Phinney's Ln. Centerville) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2025 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 264A Eastchop loamy fine sand, 0 to 3 percent slopes 6.2 100.0% Totals for Area of Interest 6.2 100.0% Soil Map—Barnstable County, Massachusetts Soil Map-Great Marsh Rd-Phinney's Ln. Centerville Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2025 Page 3 of 3 Barnstable County, Massachusetts 264A—Eastchop loamy fine sand, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 98qp Elevation: 0 to 1,000 feet Mean annual precipitation: 40 to 50 inches Mean annual air temperature: 45 to 55 degrees F Frost-free period: 140 to 240 days Farmland classification: Farmland of statewide importance Map Unit Composition Eastchop and similar soils:75 percent Minor components:25 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Eastchop Setting Landform:Outwash plains Landform position (two-dimensional):Summit Landform position (three-dimensional):Tread Down-slope shape:Convex Across-slope shape:Convex Parent material:Sandy glaciofluvial deposits; loose sandy glaciofluvial deposits Typical profile H1 - 0 to 6 inches: loamy fine sand H2 - 6 to 10 inches: loamy fine sand H3 - 10 to 25 inches: very fine sand H4 - 25 to 64 inches: very fine sand Properties and qualities Slope:0 to 3 percent Depth to restrictive feature:More than 80 inches Drainage class:Excessively drained Runoff class: Negligible Capacity of the most limiting layer to transmit water (Ksat):High to very high (6.00 to 20.00 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 4.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3s Hydrologic Soil Group: A Ecological site: F149BY005MA - Dry Outwash Map Unit Description: Eastchop loamy fine sand, 0 to 3 percent slopes---Barnstable County, Massachusetts Soil Description 264A-Great Marsh Rd-Phinney's Ln. Centerville Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2025 Page 1 of 2 Hydric soil rating: No Minor Components Hinckley Percent of map unit:8 percent Hydric soil rating: No Merrimac Percent of map unit:7 percent Hydric soil rating: No Enfield Percent of map unit:5 percent Hydric soil rating: No Carver Percent of map unit:5 percent Hydric soil rating: No Data Source Information Soil Survey Area: Barnstable County, Massachusetts Survey Area Data: Version 24, Sep 5, 2025 Map Unit Description: Eastchop loamy fine sand, 0 to 3 percent slopes---Barnstable County, Massachusetts Soil Description 264A-Great Marsh Rd-Phinney's Ln. Centerville Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2025 Page 2 of 2 Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com APPENDIX B HYDROLOGIC INFORMATION • RAINFALL DATA MAPS Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com APPENDIX C PRE-DEVELOPMENT WATERSHED RUNOFF & ROUTING 1 by Phinney's Lane 2 by Phinney's Lane 3 along western property line 4 by nursing home 5 western subcatchment 6 central subcatchment 7 existing house lot 8 north corner of site To Great Marsh Road 9 along Great Marsh Rd 10 north west part of site SP8 SP8 1P Low Area 2P Low Point 3P Southeast PL Low Area 4P By Nursing Home 5P Low Point 6P Low Point 7P Low Area 8P Low Point 10P Low Area Routing Diagram for 2020-015 EXISTING Prepared by Baxter-Nye Engineering & Survey, Printed 5/1/2026 HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcat Reach Pond Link 195 Great Marsh Road, Centerville, MA 2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 2HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Rainfall Events Listing Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 2 YR ATLAS 14 Type III 24-hr Default 24.00 1 3.40 2 2 10 YR ATLAS 14 Type III 24-hr Default 24.00 1 4.95 2 3 25 YR ATLAS 14 Type III 24-hr Default 24.00 1 5.92 2 4 100 YR ATLAS 14 Type III 24-hr Default 24.00 1 7.42 2 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 3HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: by Phinney's Lane Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 1P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.659 30 Woods, Good, HSG A 0.090 39 >75% Grass cover, Good, HSG A 0.749 31 Weighted Average 0.749 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 2: by Phinney's Lane Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 2P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.934 30 Woods, Good, HSG A 0.934 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 3: along western property line Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 3P : Southeast PL Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.476 30 Woods, Good, HSG A 0.476 100.00% Pervious Area 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 4HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 4: by nursing home Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 4P : By Nursing Home Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.160 30 Woods, Good, HSG A 0.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 5: western subcatchment Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 5P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 1.160 30 Woods, Good, HSG A 1.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 6: central subcatchment Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 6P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 5HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Area (ac) CN Adj Description 0.772 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 0.853 32 31 Weighted Average, UI Adjusted 0.841 98.59% Pervious Area 0.012 1.41% Impervious Area 0.012 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 7: existing house lot Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 7P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Adj Description 0.411 30 Woods, Good, HSG A 0.092 98 Unconnected pavement, HSG A 0.115 39 Pasture/grassland/range, Good, HSG A 0.618 42 37 Weighted Average, UI Adjusted 0.526 85.11% Pervious Area 0.092 14.89% Impervious Area 0.092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 8: north corner of site To Great Marsh Road Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Reach SP8 : SP8 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Adj Description 0.053 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.060 38 34 Weighted Average, UI Adjusted 0.053 88.33% Pervious Area 0.007 11.67% Impervious Area 0.007 100.00% Unconnected 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 6HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 9: along Great Marsh Rd Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 8P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Adj Description 0.960 30 Woods, Good, HSG A 0.043 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 1.072 33 32 Weighted Average, UI Adjusted 1.029 95.99% Pervious Area 0.043 4.01% Impervious Area 0.043 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 10: north west part of site Runoff = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 10P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.502 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.100 39 Pasture/grassland/range, Good, HSG A 0.609 32 Weighted Average 0.602 98.85% Pervious Area 0.007 1.15% Impervious Area 0.007 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 7HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Reach SP8: SP8 Inflow Area = 0.060 ac, 11.67% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Summary for Pond 1P: Low Area Inflow Area = 0.749 ac, 0.00% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.58' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 36.58' 5,129 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.58 1 0 0 1 37.00 3,178 453 453 3,178 37.75 9,914 4,676 5,129 9,917 Device Routing Invert Outlet Devices #1 Discarded 36.58'2.410 in/hr Exfiltration over Wetted area above 36.50' Excluded Wetted area = 0 sf Phase-In= 37.75' #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.58' (Free Discharge) 1=Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.58' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 2P: Low Point Inflow Area = 0.934 ac, 0.00% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 8HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 35.50' 22,258 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 819 141 141 819 37.00 5,621 2,862 3,003 5,625 38.00 37,605 19,255 22,258 37,612 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 37.50' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 3P: Southeast PL Low Area Inflow Area = 0.476 ac, 0.00% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 35.50' 20,353 cf Custom Stage Data (Conic) Listed below (Recalc) 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 9HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 274 49 49 274 37.00 4,476 1,952 2,001 4,479 38.00 37,605 18,352 20,353 37,611 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 38.00' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 4P: By Nursing Home Inflow Area = 0.160 ac, 0.00% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 39.50' 8,542 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.50 1 0 0 1 40.00 905 156 156 905 41.00 20,000 8,386 8,542 20,003 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.40' - 41.00' Excluded Wetted area = 0 sf #2 Primary 40.90'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 10HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 5P: Low Point Inflow Area = 1.160 ac, 0.00% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 36.50' 34,789 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.50 1 0 0 1 37.00 799 138 138 799 38.00 6,766 3,297 3,435 6,770 39.00 14,814 10,531 13,965 14,826 40.00 27,481 20,824 34,789 27,503 Device Routing Invert Outlet Devices #1 Discarded 36.50'2.410 in/hr Exfiltration over Wetted area from 36.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 11HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 6P: Low Point Inflow Area = 0.853 ac, 1.41% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 37.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 37.50' 11,513 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 37.50 1 0 0 1 38.00 2,103 358 358 2,103 39.00 3,409 2,730 3,088 3,422 40.00 14,769 8,425 11,513 14,787 Device Routing Invert Outlet Devices #1 Discarded 37.50'2.410 in/hr Exfiltration over Wetted area from 37.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=37.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=37.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 7P: Low Area Inflow Area = 0.618 ac, 14.89% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 12HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 39.50' 5,280 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 2,451 613 613 41.00 6,882 4,667 5,280 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 40.60' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 8P: Low Point Inflow Area = 1.072 ac, 4.01% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 39.50' 20,024 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 8,087 2,022 2,022 41.00 27,916 18,002 20,024 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 41.00' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 13HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 10P: Low Area Inflow Area = 0.609 ac, 1.15% Impervious, Inflow Depth = 0.00" for 2 YR ATLAS 14 event Inflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Discarded = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 41.50' @ 5.00 hrs Surf.Area= 1 sf Storage= 0 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no inflow) Volume Invert Avail.Storage Storage Description #1 41.50' 6,473 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 41.50 1 0 0 42.00 4,186 1,047 1,047 42.50 17,519 5,426 6,473 Device Routing Invert Outlet Devices #1 Discarded 41.50'2.410 in/hr Exfiltration over Surface area from 41.40' - 42.50' Excluded Surface area = 0 sf #2 Primary 42.40'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.00 cfs @ 5.00 hrs HW=41.50' (Free Discharge) 1=Exfiltration (Passes 0.00 cfs of 0.00 cfs potential flow) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=41.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 14HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: by Phinney's Lane Runoff = 0.00 cfs @ 22.65 hrs, Volume= 0.001 af, Depth= 0.01" Routed to Pond 1P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.659 30 Woods, Good, HSG A 0.090 39 >75% Grass cover, Good, HSG A 0.749 31 Weighted Average 0.749 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 2: by Phinney's Lane Runoff = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 2P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.934 30 Woods, Good, HSG A 0.934 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 3: along western property line Runoff = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 3P : Southeast PL Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.476 30 Woods, Good, HSG A 0.476 100.00% Pervious Area 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 15HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 4: by nursing home Runoff = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 4P : By Nursing Home Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.160 30 Woods, Good, HSG A 0.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 5: western subcatchment Runoff = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af, Depth= 0.00" Routed to Pond 5P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 1.160 30 Woods, Good, HSG A 1.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 6: central subcatchment Runoff = 0.00 cfs @ 22.65 hrs, Volume= 0.001 af, Depth= 0.01" Routed to Pond 6P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 16HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Area (ac) CN Adj Description 0.772 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 0.853 32 31 Weighted Average, UI Adjusted 0.841 98.59% Pervious Area 0.012 1.41% Impervious Area 0.012 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 7: existing house lot Runoff = 0.01 cfs @ 14.64 hrs, Volume= 0.007 af, Depth= 0.13" Routed to Pond 7P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Adj Description 0.411 30 Woods, Good, HSG A 0.092 98 Unconnected pavement, HSG A 0.115 39 Pasture/grassland/range, Good, HSG A 0.618 42 37 Weighted Average, UI Adjusted 0.526 85.11% Pervious Area 0.092 14.89% Impervious Area 0.092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 8: north corner of site To Great Marsh Road Runoff = 0.00 cfs @ 15.55 hrs, Volume= 0.000 af, Depth= 0.06" Routed to Reach SP8 : SP8 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Adj Description 0.053 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.060 38 34 Weighted Average, UI Adjusted 0.053 88.33% Pervious Area 0.007 11.67% Impervious Area 0.007 100.00% Unconnected 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 17HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 9: along Great Marsh Rd Runoff = 0.00 cfs @ 21.35 hrs, Volume= 0.002 af, Depth= 0.02" Routed to Pond 8P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Adj Description 0.960 30 Woods, Good, HSG A 0.043 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 1.072 33 32 Weighted Average, UI Adjusted 1.029 95.99% Pervious Area 0.043 4.01% Impervious Area 0.043 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 10: north west part of site Runoff = 0.00 cfs @ 21.35 hrs, Volume= 0.001 af, Depth= 0.02" Routed to Pond 10P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.502 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.100 39 Pasture/grassland/range, Good, HSG A 0.609 32 Weighted Average 0.602 98.85% Pervious Area 0.007 1.15% Impervious Area 0.007 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 18HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Reach SP8: SP8 Inflow Area = 0.060 ac, 11.67% Impervious, Inflow Depth = 0.06" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 15.55 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 15.55 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Summary for Pond 1P: Low Area Inflow Area = 0.749 ac, 0.00% Impervious, Inflow Depth = 0.01" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 22.65 hrs, Volume= 0.001 af Outflow = 0.00 cfs @ 24.13 hrs, Volume= 0.000 af, Atten= 92%, Lag= 88.7 min Discarded = 0.00 cfs @ 24.13 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.74' @ 24.13 hrs Surf.Area= 500 sf Storage= 28 cf Plug-Flow detention time= 692.6 min calculated for 0.000 af (25% of inflow) Center-of-Mass det. time= 537.7 min ( 1,797.7 - 1,260.0 ) Volume Invert Avail.Storage Storage Description #1 36.58' 5,129 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.58 1 0 0 1 37.00 3,178 453 453 3,178 37.75 9,914 4,676 5,129 9,917 Device Routing Invert Outlet Devices #1 Discarded 36.58'2.410 in/hr Exfiltration over Wetted area above 36.50' Excluded Wetted area = 0 sf Phase-In= 37.75' #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 24.13 hrs HW=36.74' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.58' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 2P: Low Point Inflow Area = 0.934 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 24.02 hrs, Volume= 0.000 af, Atten= 1%, Lag= 0.9 min Discarded = 0.00 cfs @ 24.02 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 19HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.56' @ 24.02 hrs Surf.Area= 16 sf Storage= 0 cf Plug-Flow detention time= 6.5 min calculated for 0.000 af (100% of inflow) Center-of-Mass det. time= 6.5 min ( 1,336.6 - 1,330.1 ) Volume Invert Avail.Storage Storage Description #1 35.50' 22,258 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 819 141 141 819 37.00 5,621 2,862 3,003 5,625 38.00 37,605 19,255 22,258 37,612 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 37.50' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 24.02 hrs HW=35.56' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 3P: Southeast PL Low Area Inflow Area = 0.476 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 24.02 hrs, Volume= 0.000 af, Atten= 1%, Lag= 0.9 min Discarded = 0.00 cfs @ 24.02 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.56' @ 24.02 hrs Surf.Area= 8 sf Storage= 0 cf Plug-Flow detention time= 7.9 min calculated for 0.000 af (100% of inflow) Center-of-Mass det. time= 7.9 min ( 1,338.0 - 1,330.1 ) Volume Invert Avail.Storage Storage Description #1 35.50' 20,353 cf Custom Stage Data (Conic) Listed below (Recalc) 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 20HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 274 49 49 274 37.00 4,476 1,952 2,001 4,479 38.00 37,605 18,352 20,353 37,611 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 38.00' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 24.02 hrs HW=35.56' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 4P: By Nursing Home Inflow Area = 0.160 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 24.01 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.4 min Discarded = 0.00 cfs @ 24.01 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.51' @ 24.01 hrs Surf.Area= 3 sf Storage= 0 cf Plug-Flow detention time= 2.7 min calculated for 0.000 af (100% of inflow) Center-of-Mass det. time= 2.7 min ( 1,332.8 - 1,330.1 ) Volume Invert Avail.Storage Storage Description #1 39.50' 8,542 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.50 1 0 0 1 40.00 905 156 156 905 41.00 20,000 8,386 8,542 20,003 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.40' - 41.00' Excluded Wetted area = 0 sf #2 Primary 40.90'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 21HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.00 cfs @ 24.01 hrs HW=39.51' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 5P: Low Point Inflow Area = 1.160 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 24.00 hrs, Volume= 0.000 af Outflow = 0.00 cfs @ 24.01 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.8 min Discarded = 0.00 cfs @ 24.01 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.56' @ 24.01 hrs Surf.Area= 20 sf Storage= 1 cf Plug-Flow detention time= 7.6 min calculated for 0.000 af (100% of inflow) Center-of-Mass det. time= 7.6 min ( 1,337.7 - 1,330.1 ) Volume Invert Avail.Storage Storage Description #1 36.50' 34,789 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.50 1 0 0 1 37.00 799 138 138 799 38.00 6,766 3,297 3,435 6,770 39.00 14,814 10,531 13,965 14,826 40.00 27,481 20,824 34,789 27,503 Device Routing Invert Outlet Devices #1 Discarded 36.50'2.410 in/hr Exfiltration over Wetted area from 36.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 24.01 hrs HW=36.56' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 22HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 6P: Low Point Inflow Area = 0.853 ac, 1.41% Impervious, Inflow Depth = 0.01" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 22.65 hrs, Volume= 0.001 af Outflow = 0.00 cfs @ 22.79 hrs, Volume= 0.001 af, Atten= 0%, Lag= 8.3 min Discarded = 0.00 cfs @ 22.79 hrs, Volume= 0.001 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 37.55' @ 22.79 hrs Surf.Area= 29 sf Storage= 1 cf Plug-Flow detention time= 5.6 min calculated for 0.001 af (100% of inflow) Center-of-Mass det. time= 5.6 min ( 1,265.6 - 1,260.0 ) Volume Invert Avail.Storage Storage Description #1 37.50' 11,513 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 37.50 1 0 0 1 38.00 2,103 358 358 2,103 39.00 3,409 2,730 3,088 3,422 40.00 14,769 8,425 11,513 14,787 Device Routing Invert Outlet Devices #1 Discarded 37.50'2.410 in/hr Exfiltration over Wetted area from 37.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.00 cfs @ 22.79 hrs HW=37.55' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=37.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 7P: Low Area Inflow Area = 0.618 ac, 14.89% Impervious, Inflow Depth = 0.13" for 10 YR ATLAS 14 event Inflow = 0.01 cfs @ 14.64 hrs, Volume= 0.007 af Outflow = 0.01 cfs @ 14.80 hrs, Volume= 0.007 af, Atten= 0%, Lag= 9.7 min Discarded = 0.01 cfs @ 14.80 hrs, Volume= 0.007 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.54' @ 14.80 hrs Surf.Area= 190 sf Storage= 4 cf Plug-Flow detention time= 4.4 min calculated for 0.007 af (100% of inflow) Center-of-Mass det. time= 4.4 min ( 1,052.3 - 1,047.9 ) 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 23HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 39.50' 5,280 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 2,451 613 613 41.00 6,882 4,667 5,280 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 40.60' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.01 cfs @ 14.80 hrs HW=39.54' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 8P: Low Point Inflow Area = 1.072 ac, 4.01% Impervious, Inflow Depth = 0.02" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 21.35 hrs, Volume= 0.002 af Outflow = 0.00 cfs @ 21.37 hrs, Volume= 0.002 af, Atten= 0%, Lag= 1.5 min Discarded = 0.00 cfs @ 21.37 hrs, Volume= 0.002 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.50' @ 21.37 hrs Surf.Area= 57 sf Storage= 0 cf Plug-Flow detention time= 2.2 min calculated for 0.002 af (100% of inflow) Center-of-Mass det. time= 2.2 min ( 1,206.7 - 1,204.4 ) Volume Invert Avail.Storage Storage Description #1 39.50' 20,024 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 8,087 2,022 2,022 41.00 27,916 18,002 20,024 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 41.00' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 24HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.00 cfs @ 21.37 hrs HW=39.50' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 10P: Low Area Inflow Area = 0.609 ac, 1.15% Impervious, Inflow Depth = 0.02" for 10 YR ATLAS 14 event Inflow = 0.00 cfs @ 21.35 hrs, Volume= 0.001 af Outflow = 0.00 cfs @ 21.37 hrs, Volume= 0.001 af, Atten= 0%, Lag= 1.1 min Discarded = 0.00 cfs @ 21.37 hrs, Volume= 0.001 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 41.50' @ 21.37 hrs Surf.Area= 33 sf Storage= 0 cf Plug-Flow detention time= 1.5 min calculated for 0.001 af (100% of inflow) Center-of-Mass det. time= 1.5 min ( 1,206.0 - 1,204.4 ) Volume Invert Avail.Storage Storage Description #1 41.50' 6,473 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 41.50 1 0 0 42.00 4,186 1,047 1,047 42.50 17,519 5,426 6,473 Device Routing Invert Outlet Devices #1 Discarded 41.50'2.410 in/hr Exfiltration over Surface area from 41.40' - 42.50' Excluded Surface area = 0 sf #2 Primary 42.40'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.00 cfs @ 21.37 hrs HW=41.50' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=41.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 25HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: by Phinney's Lane Runoff = 0.01 cfs @ 15.23 hrs, Volume= 0.006 af, Depth= 0.09" Routed to Pond 1P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.659 30 Woods, Good, HSG A 0.090 39 >75% Grass cover, Good, HSG A 0.749 31 Weighted Average 0.749 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 2: by Phinney's Lane Runoff = 0.01 cfs @ 15.59 hrs, Volume= 0.005 af, Depth= 0.06" Routed to Pond 2P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.934 30 Woods, Good, HSG A 0.934 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 3: along western property line Runoff = 0.00 cfs @ 15.59 hrs, Volume= 0.003 af, Depth= 0.06" Routed to Pond 3P : Southeast PL Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.476 30 Woods, Good, HSG A 0.476 100.00% Pervious Area 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 26HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 4: by nursing home Runoff = 0.00 cfs @ 15.59 hrs, Volume= 0.001 af, Depth= 0.06" Routed to Pond 4P : By Nursing Home Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.160 30 Woods, Good, HSG A 0.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 5: western subcatchment Runoff = 0.01 cfs @ 15.59 hrs, Volume= 0.006 af, Depth= 0.06" Routed to Pond 5P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 1.160 30 Woods, Good, HSG A 1.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 6: central subcatchment Runoff = 0.01 cfs @ 15.23 hrs, Volume= 0.006 af, Depth= 0.09" Routed to Pond 6P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 27HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Area (ac) CN Adj Description 0.772 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 0.853 32 31 Weighted Average, UI Adjusted 0.841 98.59% Pervious Area 0.012 1.41% Impervious Area 0.012 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 7: existing house lot Runoff = 0.06 cfs @ 12.39 hrs, Volume= 0.017 af, Depth= 0.32" Routed to Pond 7P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Adj Description 0.411 30 Woods, Good, HSG A 0.092 98 Unconnected pavement, HSG A 0.115 39 Pasture/grassland/range, Good, HSG A 0.618 42 37 Weighted Average, UI Adjusted 0.526 85.11% Pervious Area 0.092 14.89% Impervious Area 0.092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 8: north corner of site To Great Marsh Road Runoff = 0.00 cfs @ 13.68 hrs, Volume= 0.001 af, Depth= 0.19" Routed to Reach SP8 : SP8 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Adj Description 0.053 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.060 38 34 Weighted Average, UI Adjusted 0.053 88.33% Pervious Area 0.007 11.67% Impervious Area 0.007 100.00% Unconnected 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 28HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 9: along Great Marsh Rd Runoff = 0.02 cfs @ 14.88 hrs, Volume= 0.011 af, Depth= 0.12" Routed to Pond 8P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Adj Description 0.960 30 Woods, Good, HSG A 0.043 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 1.072 33 32 Weighted Average, UI Adjusted 1.029 95.99% Pervious Area 0.043 4.01% Impervious Area 0.043 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 10: north west part of site Runoff = 0.01 cfs @ 14.88 hrs, Volume= 0.006 af, Depth= 0.12" Routed to Pond 10P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.502 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.100 39 Pasture/grassland/range, Good, HSG A 0.609 32 Weighted Average 0.602 98.85% Pervious Area 0.007 1.15% Impervious Area 0.007 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 29HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Reach SP8: SP8 Inflow Area = 0.060 ac, 11.67% Impervious, Inflow Depth = 0.19" for 25 YR ATLAS 14 event Inflow = 0.00 cfs @ 13.68 hrs, Volume= 0.001 af Outflow = 0.00 cfs @ 13.68 hrs, Volume= 0.001 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Summary for Pond 1P: Low Area Inflow Area = 0.749 ac, 0.00% Impervious, Inflow Depth = 0.09" for 25 YR ATLAS 14 event Inflow = 0.01 cfs @ 15.23 hrs, Volume= 0.006 af Outflow = 0.00 cfs @ 24.10 hrs, Volume= 0.002 af, Atten= 89%, Lag= 532.3 min Discarded = 0.00 cfs @ 24.10 hrs, Volume= 0.002 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.91' @ 24.10 hrs Surf.Area= 1,997 sf Storage= 226 cf Plug-Flow detention time= 813.3 min calculated for 0.002 af (29% of inflow) Center-of-Mass det. time= 603.4 min ( 1,699.5 - 1,096.0 ) Volume Invert Avail.Storage Storage Description #1 36.58' 5,129 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.58 1 0 0 1 37.00 3,178 453 453 3,178 37.75 9,914 4,676 5,129 9,917 Device Routing Invert Outlet Devices #1 Discarded 36.58'2.410 in/hr Exfiltration over Wetted area above 36.50' Excluded Wetted area = 0 sf Phase-In= 37.75' #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 24.10 hrs HW=36.91' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.58' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 2P: Low Point Inflow Area = 0.934 ac, 0.00% Impervious, Inflow Depth = 0.06" for 25 YR ATLAS 14 event Inflow = 0.01 cfs @ 15.59 hrs, Volume= 0.005 af Outflow = 0.01 cfs @ 16.80 hrs, Volume= 0.005 af, Atten= 4%, Lag= 72.7 min Discarded = 0.01 cfs @ 16.80 hrs, Volume= 0.005 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 30HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.68' @ 16.80 hrs Surf.Area= 125 sf Storage= 8 cf Plug-Flow detention time= 18.5 min calculated for 0.005 af (100% of inflow) Center-of-Mass det. time= 18.5 min ( 1,146.7 - 1,128.2 ) Volume Invert Avail.Storage Storage Description #1 35.50' 22,258 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 819 141 141 819 37.00 5,621 2,862 3,003 5,625 38.00 37,605 19,255 22,258 37,612 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 37.50' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.01 cfs @ 16.80 hrs HW=35.68' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 3P: Southeast PL Low Area Inflow Area = 0.476 ac, 0.00% Impervious, Inflow Depth = 0.06" for 25 YR ATLAS 14 event Inflow = 0.00 cfs @ 15.59 hrs, Volume= 0.003 af Outflow = 0.00 cfs @ 16.93 hrs, Volume= 0.003 af, Atten= 4%, Lag= 80.8 min Discarded = 0.00 cfs @ 16.93 hrs, Volume= 0.003 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.72' @ 16.93 hrs Surf.Area= 63 sf Storage= 5 cf Plug-Flow detention time= 23.2 min calculated for 0.003 af (100% of inflow) Center-of-Mass det. time= 23.2 min ( 1,151.4 - 1,128.2 ) Volume Invert Avail.Storage Storage Description #1 35.50' 20,353 cf Custom Stage Data (Conic) Listed below (Recalc) 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 31HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 274 49 49 274 37.00 4,476 1,952 2,001 4,479 38.00 37,605 18,352 20,353 37,611 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 38.00' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 16.93 hrs HW=35.72' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 4P: By Nursing Home Inflow Area = 0.160 ac, 0.00% Impervious, Inflow Depth = 0.06" for 25 YR ATLAS 14 event Inflow = 0.00 cfs @ 15.59 hrs, Volume= 0.001 af Outflow = 0.00 cfs @ 15.81 hrs, Volume= 0.001 af, Atten= 1%, Lag= 13.2 min Discarded = 0.00 cfs @ 15.81 hrs, Volume= 0.001 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.56' @ 15.81 hrs Surf.Area= 22 sf Storage= 1 cf Plug-Flow detention time= 7.3 min calculated for 0.001 af (100% of inflow) Center-of-Mass det. time= 7.3 min ( 1,135.4 - 1,128.2 ) Volume Invert Avail.Storage Storage Description #1 39.50' 8,542 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.50 1 0 0 1 40.00 905 156 156 905 41.00 20,000 8,386 8,542 20,003 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.40' - 41.00' Excluded Wetted area = 0 sf #2 Primary 40.90'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 32HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.00 cfs @ 15.81 hrs HW=39.56' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 5P: Low Point Inflow Area = 1.160 ac, 0.00% Impervious, Inflow Depth = 0.06" for 25 YR ATLAS 14 event Inflow = 0.01 cfs @ 15.59 hrs, Volume= 0.006 af Outflow = 0.01 cfs @ 16.85 hrs, Volume= 0.006 af, Atten= 4%, Lag= 75.8 min Discarded = 0.01 cfs @ 16.85 hrs, Volume= 0.006 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.71' @ 16.85 hrs Surf.Area= 155 sf Storage= 12 cf Plug-Flow detention time= 20.9 min calculated for 0.006 af (100% of inflow) Center-of-Mass det. time= 20.9 min ( 1,149.0 - 1,128.2 ) Volume Invert Avail.Storage Storage Description #1 36.50' 34,789 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.50 1 0 0 1 37.00 799 138 138 799 38.00 6,766 3,297 3,435 6,770 39.00 14,814 10,531 13,965 14,826 40.00 27,481 20,824 34,789 27,503 Device Routing Invert Outlet Devices #1 Discarded 36.50'2.410 in/hr Exfiltration over Wetted area from 36.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.01 cfs @ 16.85 hrs HW=36.71' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 33HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 6P: Low Point Inflow Area = 0.853 ac, 1.41% Impervious, Inflow Depth = 0.09" for 25 YR ATLAS 14 event Inflow = 0.01 cfs @ 15.23 hrs, Volume= 0.006 af Outflow = 0.01 cfs @ 15.59 hrs, Volume= 0.006 af, Atten= 2%, Lag= 21.6 min Discarded = 0.01 cfs @ 15.59 hrs, Volume= 0.006 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 37.64' @ 15.59 hrs Surf.Area= 174 sf Storage= 9 cf Plug-Flow detention time= 12.8 min calculated for 0.006 af (100% of inflow) Center-of-Mass det. time= 12.8 min ( 1,108.9 - 1,096.0 ) Volume Invert Avail.Storage Storage Description #1 37.50' 11,513 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 37.50 1 0 0 1 38.00 2,103 358 358 2,103 39.00 3,409 2,730 3,088 3,422 40.00 14,769 8,425 11,513 14,787 Device Routing Invert Outlet Devices #1 Discarded 37.50'2.410 in/hr Exfiltration over Wetted area from 37.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.01 cfs @ 15.59 hrs HW=37.64' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=37.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 7P: Low Area Inflow Area = 0.618 ac, 14.89% Impervious, Inflow Depth = 0.32" for 25 YR ATLAS 14 event Inflow = 0.06 cfs @ 12.39 hrs, Volume= 0.017 af Outflow = 0.03 cfs @ 12.86 hrs, Volume= 0.017 af, Atten= 43%, Lag= 28.4 min Discarded = 0.03 cfs @ 12.86 hrs, Volume= 0.017 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.63' @ 12.86 hrs Surf.Area= 617 sf Storage= 39 cf Plug-Flow detention time= 11.6 min calculated for 0.017 af (100% of inflow) Center-of-Mass det. time= 11.6 min ( 994.6 - 983.0 ) 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 34HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 39.50' 5,280 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 2,451 613 613 41.00 6,882 4,667 5,280 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 40.60' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.03 cfs @ 12.86 hrs HW=39.63' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 8P: Low Point Inflow Area = 1.072 ac, 4.01% Impervious, Inflow Depth = 0.12" for 25 YR ATLAS 14 event Inflow = 0.02 cfs @ 14.88 hrs, Volume= 0.011 af Outflow = 0.02 cfs @ 15.01 hrs, Volume= 0.011 af, Atten= 0%, Lag= 7.6 min Discarded = 0.02 cfs @ 15.01 hrs, Volume= 0.011 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.52' @ 15.01 hrs Surf.Area= 310 sf Storage= 3 cf Plug-Flow detention time= 2.5 min calculated for 0.011 af (100% of inflow) Center-of-Mass det. time= 2.5 min ( 1,071.7 - 1,069.2 ) Volume Invert Avail.Storage Storage Description #1 39.50' 20,024 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 8,087 2,022 2,022 41.00 27,916 18,002 20,024 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 41.00' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 35HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.02 cfs @ 15.01 hrs HW=39.52' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.02 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 10P: Low Area Inflow Area = 0.609 ac, 1.15% Impervious, Inflow Depth = 0.12" for 25 YR ATLAS 14 event Inflow = 0.01 cfs @ 14.88 hrs, Volume= 0.006 af Outflow = 0.01 cfs @ 15.02 hrs, Volume= 0.006 af, Atten= 0%, Lag= 8.3 min Discarded = 0.01 cfs @ 15.02 hrs, Volume= 0.006 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 41.52' @ 15.02 hrs Surf.Area= 176 sf Storage= 2 cf Plug-Flow detention time= 2.4 min calculated for 0.006 af (100% of inflow) Center-of-Mass det. time= 2.4 min ( 1,071.6 - 1,069.2 ) Volume Invert Avail.Storage Storage Description #1 41.50' 6,473 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 41.50 1 0 0 42.00 4,186 1,047 1,047 42.50 17,519 5,426 6,473 Device Routing Invert Outlet Devices #1 Discarded 41.50'2.410 in/hr Exfiltration over Surface area from 41.40' - 42.50' Excluded Surface area = 0 sf #2 Primary 42.40'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.01 cfs @ 15.02 hrs HW=41.52' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=41.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 36HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: by Phinney's Lane Runoff = 0.07 cfs @ 12.42 hrs, Volume= 0.022 af, Depth= 0.35" Routed to Pond 1P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.659 30 Woods, Good, HSG A 0.090 39 >75% Grass cover, Good, HSG A 0.749 31 Weighted Average 0.749 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 2: by Phinney's Lane Runoff = 0.05 cfs @ 12.47 hrs, Volume= 0.023 af, Depth= 0.29" Routed to Pond 2P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.934 30 Woods, Good, HSG A 0.934 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 3: along western property line Runoff = 0.03 cfs @ 12.47 hrs, Volume= 0.012 af, Depth= 0.29" Routed to Pond 3P : Southeast PL Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.476 30 Woods, Good, HSG A 0.476 100.00% Pervious Area 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 37HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 4: by nursing home Runoff = 0.01 cfs @ 12.47 hrs, Volume= 0.004 af, Depth= 0.29" Routed to Pond 4P : By Nursing Home Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.160 30 Woods, Good, HSG A 0.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 5: western subcatchment Runoff = 0.06 cfs @ 12.47 hrs, Volume= 0.028 af, Depth= 0.29" Routed to Pond 5P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 1.160 30 Woods, Good, HSG A 1.160 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 6: central subcatchment Runoff = 0.07 cfs @ 12.42 hrs, Volume= 0.025 af, Depth= 0.35" Routed to Pond 6P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 38HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Area (ac) CN Adj Description 0.772 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 0.853 32 31 Weighted Average, UI Adjusted 0.841 98.59% Pervious Area 0.012 1.41% Impervious Area 0.012 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 7: existing house lot Runoff = 0.25 cfs @ 12.13 hrs, Volume= 0.039 af, Depth= 0.77" Routed to Pond 7P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Adj Description 0.411 30 Woods, Good, HSG A 0.092 98 Unconnected pavement, HSG A 0.115 39 Pasture/grassland/range, Good, HSG A 0.618 42 37 Weighted Average, UI Adjusted 0.526 85.11% Pervious Area 0.092 14.89% Impervious Area 0.092 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 8: north corner of site To Great Marsh Road Runoff = 0.01 cfs @ 12.33 hrs, Volume= 0.003 af, Depth= 0.55" Routed to Reach SP8 : SP8 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Adj Description 0.053 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.060 38 34 Weighted Average, UI Adjusted 0.053 88.33% Pervious Area 0.007 11.67% Impervious Area 0.007 100.00% Unconnected 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 39HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 9: along Great Marsh Rd Runoff = 0.14 cfs @ 12.39 hrs, Volume= 0.037 af, Depth= 0.41" Routed to Pond 8P : Low Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Adj Description 0.960 30 Woods, Good, HSG A 0.043 98 Unconnected pavement, HSG A 0.069 39 Pasture/grassland/range, Good, HSG A 1.072 33 32 Weighted Average, UI Adjusted 1.029 95.99% Pervious Area 0.043 4.01% Impervious Area 0.043 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Summary for Subcatchment 10: north west part of site Runoff = 0.08 cfs @ 12.39 hrs, Volume= 0.021 af, Depth= 0.41" Routed to Pond 10P : Low Area Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.502 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.100 39 Pasture/grassland/range, Good, HSG A 0.609 32 Weighted Average 0.602 98.85% Pervious Area 0.007 1.15% Impervious Area 0.007 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 40HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Reach SP8: SP8 Inflow Area = 0.060 ac, 11.67% Impervious, Inflow Depth = 0.55" for 100 YR ATLAS 14 event Inflow = 0.01 cfs @ 12.33 hrs, Volume= 0.003 af Outflow = 0.01 cfs @ 12.33 hrs, Volume= 0.003 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Summary for Pond 1P: Low Area Inflow Area = 0.749 ac, 0.00% Impervious, Inflow Depth = 0.35" for 100 YR ATLAS 14 event Inflow = 0.07 cfs @ 12.42 hrs, Volume= 0.022 af Outflow = 0.00 cfs @ 24.09 hrs, Volume= 0.006 af, Atten= 95%, Lag= 700.0 min Discarded = 0.00 cfs @ 24.09 hrs, Volume= 0.006 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 37.11' @ 24.09 hrs Surf.Area= 3,955 sf Storage= 856 cf Plug-Flow detention time= 857.6 min calculated for 0.006 af (27% of inflow) Center-of-Mass det. time= 642.9 min ( 1,638.4 - 995.5 ) Volume Invert Avail.Storage Storage Description #1 36.58' 5,129 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.58 1 0 0 1 37.00 3,178 453 453 3,178 37.75 9,914 4,676 5,129 9,917 Device Routing Invert Outlet Devices #1 Discarded 36.58'2.410 in/hr Exfiltration over Wetted area above 36.50' Excluded Wetted area = 0 sf Phase-In= 37.75' #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.00 cfs @ 24.09 hrs HW=37.11' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.58' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 2P: Low Point Inflow Area = 0.934 ac, 0.00% Impervious, Inflow Depth = 0.29" for 100 YR ATLAS 14 event Inflow = 0.05 cfs @ 12.47 hrs, Volume= 0.023 af Outflow = 0.03 cfs @ 14.89 hrs, Volume= 0.023 af, Atten= 29%, Lag= 145.3 min Discarded = 0.03 cfs @ 14.89 hrs, Volume= 0.023 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 41HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.93' @ 14.89 hrs Surf.Area= 623 sf Storage= 94 cf Plug-Flow detention time= 37.6 min calculated for 0.023 af (100% of inflow) Center-of-Mass det. time= 37.6 min ( 1,048.9 - 1,011.3 ) Volume Invert Avail.Storage Storage Description #1 35.50' 22,258 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 819 141 141 819 37.00 5,621 2,862 3,003 5,625 38.00 37,605 19,255 22,258 37,612 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 37.50' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.03 cfs @ 14.89 hrs HW=35.93' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 3P: Southeast PL Low Area Inflow Area = 0.476 ac, 0.00% Impervious, Inflow Depth = 0.29" for 100 YR ATLAS 14 event Inflow = 0.03 cfs @ 12.47 hrs, Volume= 0.012 af Outflow = 0.02 cfs @ 14.94 hrs, Volume= 0.012 af, Atten= 30%, Lag= 148.7 min Discarded = 0.02 cfs @ 14.94 hrs, Volume= 0.012 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.02' @ 14.94 hrs Surf.Area= 315 sf Storage= 56 cf Plug-Flow detention time= 46.2 min calculated for 0.012 af (100% of inflow) Center-of-Mass det. time= 46.2 min ( 1,057.5 - 1,011.3 ) Volume Invert Avail.Storage Storage Description #1 35.50' 20,353 cf Custom Stage Data (Conic) Listed below (Recalc) 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 42HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.50 1 0 0 1 36.00 274 49 49 274 37.00 4,476 1,952 2,001 4,479 38.00 37,605 18,352 20,353 37,611 Device Routing Invert Outlet Devices #1 Discarded 35.50'2.410 in/hr Exfiltration over Wetted area from 35.40' - 38.00' Excluded Wetted area = 0 sf #2 Primary 37.50'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.02 cfs @ 14.94 hrs HW=36.02' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.02 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=35.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 4P: By Nursing Home Inflow Area = 0.160 ac, 0.00% Impervious, Inflow Depth = 0.29" for 100 YR ATLAS 14 event Inflow = 0.01 cfs @ 12.47 hrs, Volume= 0.004 af Outflow = 0.01 cfs @ 13.86 hrs, Volume= 0.004 af, Atten= 23%, Lag= 83.6 min Discarded = 0.01 cfs @ 13.86 hrs, Volume= 0.004 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.67' @ 13.86 hrs Surf.Area= 117 sf Storage= 7 cf Plug-Flow detention time= 15.1 min calculated for 0.004 af (100% of inflow) Center-of-Mass det. time= 15.1 min ( 1,026.4 - 1,011.3 ) Volume Invert Avail.Storage Storage Description #1 39.50' 8,542 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.50 1 0 0 1 40.00 905 156 156 905 41.00 20,000 8,386 8,542 20,003 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.40' - 41.00' Excluded Wetted area = 0 sf #2 Primary 40.90'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 43HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.01 cfs @ 13.86 hrs HW=39.67' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 5P: Low Point Inflow Area = 1.160 ac, 0.00% Impervious, Inflow Depth = 0.29" for 100 YR ATLAS 14 event Inflow = 0.06 cfs @ 12.47 hrs, Volume= 0.028 af Outflow = 0.04 cfs @ 15.00 hrs, Volume= 0.028 af, Atten= 31%, Lag= 152.3 min Discarded = 0.04 cfs @ 15.00 hrs, Volume= 0.028 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.99' @ 15.00 hrs Surf.Area= 762 sf Storage= 128 cf Plug-Flow detention time= 42.2 min calculated for 0.028 af (100% of inflow) Center-of-Mass det. time= 42.2 min ( 1,053.5 - 1,011.3 ) Volume Invert Avail.Storage Storage Description #1 36.50' 34,789 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 36.50 1 0 0 1 37.00 799 138 138 799 38.00 6,766 3,297 3,435 6,770 39.00 14,814 10,531 13,965 14,826 40.00 27,481 20,824 34,789 27,503 Device Routing Invert Outlet Devices #1 Discarded 36.50'2.410 in/hr Exfiltration over Wetted area from 36.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.04 cfs @ 15.00 hrs HW=36.99' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.04 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=36.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 44HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 6P: Low Point Inflow Area = 0.853 ac, 1.41% Impervious, Inflow Depth = 0.35" for 100 YR ATLAS 14 event Inflow = 0.07 cfs @ 12.42 hrs, Volume= 0.025 af Outflow = 0.04 cfs @ 13.81 hrs, Volume= 0.025 af, Atten= 43%, Lag= 83.0 min Discarded = 0.04 cfs @ 13.81 hrs, Volume= 0.025 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 37.80' @ 13.81 hrs Surf.Area= 757 sf Storage= 77 cf Plug-Flow detention time= 24.9 min calculated for 0.025 af (100% of inflow) Center-of-Mass det. time= 24.9 min ( 1,020.4 - 995.5 ) Volume Invert Avail.Storage Storage Description #1 37.50' 11,513 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 37.50 1 0 0 1 38.00 2,103 358 358 2,103 39.00 3,409 2,730 3,088 3,422 40.00 14,769 8,425 11,513 14,787 Device Routing Invert Outlet Devices #1 Discarded 37.50'2.410 in/hr Exfiltration over Wetted area from 37.40' - 40.00' Excluded Wetted area = 0 sf #2 Primary 39.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.04 cfs @ 13.81 hrs HW=37.80' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.04 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=37.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 7P: Low Area Inflow Area = 0.618 ac, 14.89% Impervious, Inflow Depth = 0.77" for 100 YR ATLAS 14 event Inflow = 0.25 cfs @ 12.13 hrs, Volume= 0.039 af Outflow = 0.09 cfs @ 12.80 hrs, Volume= 0.039 af, Atten= 64%, Lag= 40.3 min Discarded = 0.09 cfs @ 12.80 hrs, Volume= 0.039 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.83' @ 12.80 hrs Surf.Area= 1,612 sf Storage= 265 cf Plug-Flow detention time= 30.3 min calculated for 0.039 af (100% of inflow) Center-of-Mass det. time= 30.3 min ( 964.5 - 934.2 ) 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 45HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 39.50' 5,280 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 2,451 613 613 41.00 6,882 4,667 5,280 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 40.60' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height Discarded OutFlow Max=0.09 cfs @ 12.80 hrs HW=39.83' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.09 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 8P: Low Point Inflow Area = 1.072 ac, 4.01% Impervious, Inflow Depth = 0.41" for 100 YR ATLAS 14 event Inflow = 0.14 cfs @ 12.39 hrs, Volume= 0.037 af Outflow = 0.08 cfs @ 12.59 hrs, Volume= 0.037 af, Atten= 37%, Lag= 12.3 min Discarded = 0.08 cfs @ 12.59 hrs, Volume= 0.037 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.59' @ 12.59 hrs Surf.Area= 1,523 sf Storage= 72 cf Plug-Flow detention time= 8.0 min calculated for 0.037 af (100% of inflow) Center-of-Mass det. time= 8.0 min ( 989.9 - 981.8 ) Volume Invert Avail.Storage Storage Description #1 39.50' 20,024 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 39.50 1 0 0 40.00 8,087 2,022 2,022 41.00 27,916 18,002 20,024 Device Routing Invert Outlet Devices #1 Discarded 39.50'2.410 in/hr Exfiltration over Surface area from 39.40' - 41.00' Excluded Surface area = 0 sf #2 Primary 40.50'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 1.0' Crest Height 195 Great Marsh Road, Centerville, MA Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 EXISTING Printed 5/1/2026Prepared by Baxter-Nye Engineering & Survey Page 46HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.08 cfs @ 12.59 hrs HW=39.59' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.08 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=39.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Pond 10P: Low Area Inflow Area = 0.609 ac, 1.15% Impervious, Inflow Depth = 0.41" for 100 YR ATLAS 14 event Inflow = 0.08 cfs @ 12.39 hrs, Volume= 0.021 af Outflow = 0.05 cfs @ 12.61 hrs, Volume= 0.021 af, Atten= 39%, Lag= 13.6 min Discarded = 0.05 cfs @ 12.61 hrs, Volume= 0.021 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 41.60' @ 12.61 hrs Surf.Area= 844 sf Storage= 43 cf Plug-Flow detention time= 8.7 min calculated for 0.021 af (100% of inflow) Center-of-Mass det. time= 8.7 min ( 990.5 - 981.8 ) Volume Invert Avail.Storage Storage Description #1 41.50' 6,473 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 41.50 1 0 0 42.00 4,186 1,047 1,047 42.50 17,519 5,426 6,473 Device Routing Invert Outlet Devices #1 Discarded 41.50'2.410 in/hr Exfiltration over Surface area from 41.40' - 42.50' Excluded Surface area = 0 sf #2 Primary 42.40'10.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.05 cfs @ 12.61 hrs HW=41.60' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=41.50' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com APPENDIX D POST- DEVELOPMENT WATERSHED RUNOFF & ROUTING 1 Area to Forebay by South Corner 2 Area to West Forebay 3 Area to Forebay at Great Marsh Road 4 Area to Storm Filter Roof House Roof 1210 sf 1P SWM 1 Forebay w Retention Pond and LB's 2P SWM 2 Forebay w Retention Pond 3P SWM 3 Forebay w Leach Pits 4P LB's from StormFilterDW Typical Roof Dry Well Routing Diagram for 2020-015 PROPOSEDw Ret Ponds Prepared by Baxter-Nye Engineering & Survey, Printed 5/1/2026 HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcat Reach Pond Link 2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 2HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Rainfall Events Listing Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 2 YR ATLAS 14 Type III 24-hr Default 24.00 1 3.40 2 2 10 YR ATLAS 14 Type III 24-hr Default 24.00 1 4.95 2 3 25 YR ATLAS 14 Type III 24-hr Default 24.00 1 5.92 2 4 100 YR ATLAS 14 Type III 24-hr Default 24.00 1 7.42 2 2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 3HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 3.064 39 >75% Grass cover, Good, HSG A (1, 2, 3, 4) 0.468 98 Paved parking, HSG A (1, 2, 4) 0.765 98 Paved roads w/curbs & sewers, HSG A (1, 2, 3, 4) 0.028 98 Roofs, HSG A (Roof) 0.079 98 Unconnected pavement, HSG A (1, 2, 3, 4) 0.756 30 Woods, Good, HSG A (1, 2, 3, 4) 5.160 53 TOTAL AREA 2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 4HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 3.064 0.000 0.000 0.000 0.000 3.064 >75% Grass cover, Good 1, 2, 3, 4 0.468 0.000 0.000 0.000 0.000 0.468 Paved parking 1, 2, 4 0.765 0.000 0.000 0.000 0.000 0.765 Paved roads w/curbs & sewers 1, 2, 3, 4 0.028 0.000 0.000 0.000 0.000 0.028 Roofs Ro of 0.079 0.000 0.000 0.000 0.000 0.079 Unconnected pavement 1, 2, 3, 4 0.756 0.000 0.000 0.000 0.000 0.756 Woods, Good 1, 2, 3, 4 5.160 0.000 0.000 0.000 0.000 5.160 TOTAL AREA Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 5HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Time span=5.00-40.00 hrs, dt=0.01 hrs, 3501 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Runoff Area=2.576 ac 26.98% Impervious Runoff Depth=0.25"Subcatchment 1: Area to Forebay by South Flow Length=643' Tc=13.0 min CN=53 Runoff=0.24 cfs 0.054 af Runoff Area=1.740 ac 22.93% Impervious Runoff Depth=0.20"Subcatchment 2: Area to West Forebay Flow Length=327' Tc=10.3 min CN=51 Runoff=0.10 cfs 0.029 af Runoff Area=0.279 ac 28.67% Impervious Runoff Depth=0.28"Subcatchment 3: Area to Forebay at Great Tc=5.0 min UI Adjusted CN=54 Runoff=0.03 cfs 0.007 af Runoff Area=0.537 ac 25.70% Impervious Runoff Depth=0.25"Subcatchment 4: Area to Storm Filter Flow Length=204' Tc=5.5 min CN=53 Runoff=0.05 cfs 0.011 af Runoff Area=0.028 ac 100.00% Impervious Runoff Depth>3.10"Subcatchment Roof: House Roof 1210 sf Tc=5.0 min CN=98 Runoff=0.10 cfs 0.007 af Peak Elev=33.40' Storage=174 cf Inflow=0.24 cfs 0.054 afPond 1P: SWM 1 Forebay w Retention Pond Discarded=0.13 cfs 0.054 af Primary=0.00 cfs 0.000 af Outflow=0.13 cfs 0.054 af Peak Elev=34.51' Storage=133 cf Inflow=0.10 cfs 0.029 afPond 2P: SWM 2 Forebay w Retention Pond Discarded=0.05 cfs 0.029 af Primary=0.00 cfs 0.000 af Outflow=0.05 cfs 0.029 af Peak Elev=34.28' Storage=10 cf Inflow=0.03 cfs 0.007 afPond 3P: SWM 3 Forebay w Leach Pits Discarded=0.03 cfs 0.007 af Primary=0.00 cfs 0.000 af Outflow=0.03 cfs 0.007 af Peak Elev=32.81' Storage=10 cf Inflow=0.05 cfs 0.011 afPond 4P: LB's from StormFilter Discarded=0.05 cfs 0.011 af Primary=0.00 cfs 0.000 af Outflow=0.05 cfs 0.011 af Peak Elev=30.93' Storage=0.002 af Inflow=0.10 cfs 0.007 afPond DW: Typical Roof Dry Well Outflow=0.02 cfs 0.007 af Total Runoff Area = 5.160 ac Runoff Volume = 0.108 af Average Runoff Depth = 0.25" 74.03% Pervious = 3.820 ac 25.97% Impervious = 1.340 ac Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 6HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: Area to Forebay by South Corner Runoff = 0.24 cfs @ 12.46 hrs, Volume= 0.054 af, Depth= 0.25" Routed to Pond 1P : SWM 1 Forebay w Retention Pond and LB's Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.453 30 Woods, Good, HSG A 1.428 39 >75% Grass cover, Good, HSG A 0.419 98 Paved roads w/curbs & sewers, HSG A 0.234 98 Paved parking, HSG A 0.042 98 Unconnected pavement, HSG A 2.576 53 Weighted Average 1.881 73.02% Pervious Area 0.695 26.98% Impervious Area 0.042 6.04% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 75 0.0160 0.15 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 1.1 45 0.0100 0.70 Shallow Concentrated Flow, B Short Grass Pasture Kv= 7.0 fps 1.7 222 0.0118 2.21 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 1.9 301 0.0030 2.69 2.11 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 Corrugated PP, smooth interior 13.0 643 Total Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 7HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 1: Area to Forebay by South Corner Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Runoff Area=2.576 ac Runoff Volume=0.054 af Runoff Depth=0.25" Flow Length=643' Tc=13.0 min CN=53 0.24 cfs @ 12.46 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 8HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 2: Area to West Forebay Runoff = 0.10 cfs @ 12.46 hrs, Volume= 0.029 af, Depth= 0.20" Routed to Pond 2P : SWM 2 Forebay w Retention Pond Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 1.102 39 >75% Grass cover, Good, HSG A 0.216 98 Paved roads w/curbs & sewers, HSG A 0.165 98 Paved parking, HSG A 0.239 30 Woods, Good, HSG A 0.018 98 Unconnected pavement, HSG A 1.740 51 Weighted Average 1.341 77.07% Pervious Area 0.399 22.93% Impervious Area 0.018 4.51% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 60 0.0100 0.12 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 37 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 1.4 193 0.0130 2.31 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 37 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 10.3 327 Total Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 9HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 2: Area to West Forebay Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.115 0.11 0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Runoff Area=1.740 ac Runoff Volume=0.029 af Runoff Depth=0.20" Flow Length=327' Tc=10.3 min CN=51 0.10 cfs @ 12.46 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 10HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 3: Area to Forebay at Great Marsh Road Runoff = 0.03 cfs @ 12.30 hrs, Volume= 0.007 af, Depth= 0.28" Routed to Pond 3P : SWM 3 Forebay w Leach Pits Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Adj Description 0.180 39 >75% Grass cover, Good, HSG A 0.068 98 Paved roads w/curbs & sewers, HSG A 0.000 98 Paved parking, HSG A 0.019 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.279 55 54 Weighted Average, UI Adjusted 0.199 71.33% Pervious Area 0.080 28.67% Impervious Area 0.012 15.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment 3: Area to Forebay at Great Marsh Road Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.038 0.036 0.034 0.032 0.03 0.028 0.026 0.024 0.022 0.02 0.018 0.016 0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Runoff Area=0.279 ac Runoff Volume=0.007 af Runoff Depth=0.28" Tc=5.0 min UI Adjusted CN=54 0.03 cfs @ 12.30 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 11HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 4: Area to Storm Filter Runoff = 0.05 cfs @ 12.34 hrs, Volume= 0.011 af, Depth= 0.25" Routed to Pond 4P : LB's from StormFilter Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.354 39 >75% Grass cover, Good, HSG A 0.062 98 Paved roads w/curbs & sewers, HSG A 0.069 98 Paved parking, HSG A 0.045 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.537 53 Weighted Average 0.399 74.30% Pervious Area 0.138 25.70% Impervious Area 0.007 5.07% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.7 70 0.0570 0.25 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 40 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 0.2 54 0.0380 3.96 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 40 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 5.5 204 Total Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 12HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 4: Area to Storm Filter Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Runoff Area=0.537 ac Runoff Volume=0.011 af Runoff Depth=0.25" Flow Length=204' Tc=5.5 min CN=53 0.05 cfs @ 12.34 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 13HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment Roof: House Roof 1210 sf Runoff = 0.10 cfs @ 12.07 hrs, Volume= 0.007 af, Depth> 3.10" Routed to Pond DW : Typical Roof Dry Well Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Area (ac) CN Description 0.028 98 Roofs, HSG A 0.028 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment Roof: House Roof 1210 sf Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40" Runoff Area=0.028 ac Runoff Volume=0.007 af Runoff Depth>3.10" Tc=5.0 min CN=98 0.10 cfs @ 12.07 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 14HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Area = 2.576 ac, 26.98% Impervious, Inflow Depth = 0.25" for 2 YR ATLAS 14 event Inflow = 0.24 cfs @ 12.46 hrs, Volume= 0.054 af Outflow = 0.13 cfs @ 12.83 hrs, Volume= 0.054 af, Atten= 45%, Lag= 22.1 min Discarded = 0.13 cfs @ 12.83 hrs, Volume= 0.054 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 33.40' @ 12.83 hrs Surf.Area= 605 sf Storage= 174 cf Plug-Flow detention time= 9.1 min calculated for 0.054 af (100% of inflow) Center-of-Mass det. time= 9.1 min ( 975.2 - 966.2 ) Volume Invert Avail.Storage Storage Description #1 33.00' 12,247 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 166 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 4 640 cf Overall - 226 cf Embedded = 414 cf x 40.0% Voids #3 33.25' 226 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 4 Inside #2 12,639 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 33.00 143 0 0 143 34.00 816 434 434 820 35.00 1,367 1,080 1,513 1,383 36.00 1,816 1,586 3,099 1,854 36.50 2,064 969 4,069 2,114 37.00 2,998 1,258 5,327 3,052 38.00 11,812 6,920 12,247 11,871 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #2 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.00' Excluded Wetted area = 2,267 sf #3 Primary 37.65'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.13 cfs @ 12.83 hrs HW=33.40' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.13 cfs) 2=Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 15HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=2.576 ac Peak Elev=33.40' Storage=174 cf 0.24 cfs @ 12.46 hrs 0.13 cfs @ 12.83 hrs 0.13 cfs @ 12.83 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 16HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 2P: SWM 2 Forebay w Retention Pond Inflow Area = 1.740 ac, 22.93% Impervious, Inflow Depth = 0.20" for 2 YR ATLAS 14 event Inflow = 0.10 cfs @ 12.46 hrs, Volume= 0.029 af Outflow = 0.05 cfs @ 14.07 hrs, Volume= 0.029 af, Atten= 56%, Lag= 96.7 min Discarded = 0.05 cfs @ 14.07 hrs, Volume= 0.029 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 34.51' @ 14.07 hrs Surf.Area= 128 sf Storage= 133 cf Plug-Flow detention time= 27.7 min calculated for 0.029 af (100% of inflow) Center-of-Mass det. time= 27.6 min ( 1,010.8 - 983.1 ) Volume Invert Avail.Storage Storage Description #1 35.00' 10,731 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 83 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 2 320 cf Overall - 113 cf Embedded = 207 cf x 40.0% Voids #3 33.25' 113 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 2 Inside #2 10,927 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.00 471 0 0 471 36.00 1,366 880 880 1,372 37.00 2,237 1,784 2,663 2,256 38.00 3,710 2,943 5,606 3,741 39.00 6,685 5,125 10,731 6,727 Device Routing Invert Outlet Devices #1 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.75' Excluded Wetted area = 1,311 sf #2 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #3 Primary 38.75'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.05 cfs @ 14.07 hrs HW=34.51' (Free Discharge) 1=Exfiltration ( Controls 0.00 cfs) 2=Exfiltration (Exfiltration Controls 0.05 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 17HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 2P: SWM 2 Forebay w Retention Pond Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.115 0.11 0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Inflow Area=1.740 ac Peak Elev=34.51' Storage=133 cf 0.10 cfs @ 12.46 hrs 0.05 cfs @ 14.07 hrs 0.05 cfs @ 14.07 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 18HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 3P: SWM 3 Forebay w Leach Pits Inflow Area = 0.279 ac, 28.67% Impervious, Inflow Depth = 0.28" for 2 YR ATLAS 14 event Inflow = 0.03 cfs @ 12.30 hrs, Volume= 0.007 af Outflow = 0.03 cfs @ 12.47 hrs, Volume= 0.007 af, Atten= 21%, Lag= 9.7 min Discarded = 0.03 cfs @ 12.47 hrs, Volume= 0.007 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 34.28' @ 12.47 hrs Surf.Area= 128 sf Storage= 10 cf Plug-Flow detention time= 3.6 min calculated for 0.007 af (100% of inflow) Center-of-Mass det. time= 3.6 min ( 953.9 - 950.3 ) Volume Invert Avail.Storage Storage Description #1 34.08' 140 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 2 576 cf Overall - 226 cf Embedded = 350 cf x 40.0% Voids #2 34.58' 226 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 2 Inside #1 #3 39.60' 8,164 cf Custom Stage Data (Conic) Listed below (Recalc) 8,531 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.60 1 0 0 1 40.00 287 41 41 287 41.00 583 426 467 592 41.50 753 333 800 768 42.00 922 418 1,218 945 43.00 1,340 1,125 2,343 1,379 44.00 12,099 5,822 8,164 12,141 Device Routing Invert Outlet Devices #1 Discarded 34.08'8.270 in/hr Exfiltration over Wetted area from 34.07' - 39.50' Excluded Wetted area = 0 sf #2 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.50' - 43.50' Excluded Wetted area = 416 sf #3 Primary 43.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.03 cfs @ 12.47 hrs HW=34.28' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.03 cfs) 2=Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=34.08' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 19HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 3P: SWM 3 Forebay w Leach Pits Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.038 0.036 0.034 0.032 0.03 0.028 0.026 0.024 0.022 0.02 0.018 0.016 0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 Inflow Area=0.279 ac Peak Elev=34.28' Storage=10 cf 0.03 cfs @ 12.30 hrs 0.03 cfs @ 12.47 hrs 0.03 cfs @ 12.47 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 20HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 4P: LB's from StormFilter Inflow Area = 0.537 ac, 25.70% Impervious, Inflow Depth = 0.25" for 2 YR ATLAS 14 event Inflow = 0.05 cfs @ 12.34 hrs, Volume= 0.011 af Outflow = 0.05 cfs @ 12.39 hrs, Volume= 0.011 af, Atten= 3%, Lag= 3.2 min Discarded = 0.05 cfs @ 12.39 hrs, Volume= 0.011 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 32.81' @ 12.39 hrs Surf.Area= 384 sf Storage= 10 cf Plug-Flow detention time= 3.1 min calculated for 0.011 af (100% of inflow) Center-of-Mass det. time= 3.1 min ( 962.3 - 959.2 ) Volume Invert Avail.Storage Storage Description #1 32.75' 420 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 6 1,728 cf Overall - 679 cf Embedded = 1,049 cf x 40.0% Voids #2 33.25' 679 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 6 Inside #1 #3 39.80' 4,780 cf Custom Stage Data (Conic) Listed below (Recalc) 5,878 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.80 8 0 0 8 40.00 282 22 22 282 41.00 1,676 882 904 1,680 42.00 6,620 3,876 4,780 6,629 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 38.17' Excluded Wetted area = 0 sf #2 Primary 40.91'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.08 cfs @ 12.39 hrs HW=32.81' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.08 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 21HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 4P: LB's from StormFilter Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Inflow Area=0.537 ac Peak Elev=32.81' Storage=10 cf 0.05 cfs @ 12.34 hrs 0.05 cfs @ 12.39 hrs 0.05 cfs @ 12.39 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 2 YR ATLAS 14 Rainfall=3.40"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 22HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond DW: Typical Roof Dry Well Inflow Area = 0.028 ac,100.00% Impervious, Inflow Depth > 3.10" for 2 YR ATLAS 14 event Inflow = 0.10 cfs @ 12.07 hrs, Volume= 0.007 af Outflow = 0.02 cfs @ 11.71 hrs, Volume= 0.007 af, Atten= 80%, Lag= 0.0 min Discarded = 0.02 cfs @ 11.71 hrs, Volume= 0.007 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 30.93' @ 12.48 hrs Surf.Area= 0.002 ac Storage= 0.002 af Plug-Flow detention time= 19.7 min calculated for 0.007 af (100% of inflow) Center-of-Mass det. time= 19.6 min ( 784.5 - 764.9 ) Volume Invert Avail.Storage Storage Description #1 29.50' 0.003 af 10.00'W x 10.00'L x 4.50'H Prismatoid 0.010 af Overall - 0.003 af Embedded = 0.008 af x 40.0% Voids #2 30.00' 0.003 af 6.00'D x 4.00'H Vertical Cone/Cylinder Inside #1 0.006 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 29.50'8.270 in/hr Exfiltration over Surface area from 29.40' - 34.33' Excluded Surface area = 0.000 ac Discarded OutFlow Max=0.02 cfs @ 11.71 hrs HW=29.55' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.02 cfs) Pond DW: Typical Roof Dry Well Inflow Discarded Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Inflow Area=0.028 ac Peak Elev=30.93' Storage=0.002 af 0.10 cfs @ 12.07 hrs 0.02 cfs @ 11.71 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 23HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Time span=5.00-40.00 hrs, dt=0.01 hrs, 3501 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Runoff Area=2.576 ac 26.98% Impervious Runoff Depth=0.84"Subcatchment 1: Area to Forebay by South Flow Length=643' Tc=13.0 min CN=53 Runoff=1.46 cfs 0.180 af Runoff Area=1.740 ac 22.93% Impervious Runoff Depth=0.73"Subcatchment 2: Area to West Forebay Flow Length=327' Tc=10.3 min CN=51 Runoff=0.83 cfs 0.105 af Runoff Area=0.279 ac 28.67% Impervious Runoff Depth=0.90"Subcatchment 3: Area to Forebay at Great Tc=5.0 min UI Adjusted CN=54 Runoff=0.23 cfs 0.021 af Runoff Area=0.537 ac 25.70% Impervious Runoff Depth=0.84"Subcatchment 4: Area to Storm Filter Flow Length=204' Tc=5.5 min CN=53 Runoff=0.39 cfs 0.037 af Runoff Area=0.028 ac 100.00% Impervious Runoff Depth>4.59"Subcatchment Roof: House Roof 1210 sf Tc=5.0 min CN=98 Runoff=0.14 cfs 0.011 af Peak Elev=35.04' Storage=1,924 cf Inflow=1.46 cfs 0.180 afPond 1P: SWM 1 Forebay w Retention Pond Discarded=0.37 cfs 0.180 af Primary=0.00 cfs 0.000 af Outflow=0.37 cfs 0.180 af Peak Elev=35.87' Storage=905 cf Inflow=0.83 cfs 0.105 afPond 2P: SWM 2 Forebay w Retention Pond Discarded=0.26 cfs 0.105 af Primary=0.00 cfs 0.000 af Outflow=0.26 cfs 0.105 af Peak Elev=36.64' Storage=201 cf Inflow=0.23 cfs 0.021 afPond 3P: SWM 3 Forebay w Leach Pits Discarded=0.06 cfs 0.021 af Primary=0.00 cfs 0.000 af Outflow=0.06 cfs 0.021 af Peak Elev=34.09' Storage=291 cf Inflow=0.39 cfs 0.037 afPond 4P: LB's from StormFilter Discarded=0.12 cfs 0.037 af Primary=0.00 cfs 0.000 af Outflow=0.12 cfs 0.037 af Peak Elev=32.01' Storage=0.003 af Inflow=0.14 cfs 0.011 afPond DW: Typical Roof Dry Well Outflow=0.02 cfs 0.011 af Total Runoff Area = 5.160 ac Runoff Volume = 0.354 af Average Runoff Depth = 0.82" 74.03% Pervious = 3.820 ac 25.97% Impervious = 1.340 ac Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 24HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: Area to Forebay by South Corner Runoff = 1.46 cfs @ 12.23 hrs, Volume= 0.180 af, Depth= 0.84" Routed to Pond 1P : SWM 1 Forebay w Retention Pond and LB's Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.453 30 Woods, Good, HSG A 1.428 39 >75% Grass cover, Good, HSG A 0.419 98 Paved roads w/curbs & sewers, HSG A 0.234 98 Paved parking, HSG A 0.042 98 Unconnected pavement, HSG A 2.576 53 Weighted Average 1.881 73.02% Pervious Area 0.695 26.98% Impervious Area 0.042 6.04% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 75 0.0160 0.15 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 1.1 45 0.0100 0.70 Shallow Concentrated Flow, B Short Grass Pasture Kv= 7.0 fps 1.7 222 0.0118 2.21 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 1.9 301 0.0030 2.69 2.11 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 Corrugated PP, smooth interior 13.0 643 Total Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 25HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 1: Area to Forebay by South Corner Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)1 0 Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Runoff Area=2.576 ac Runoff Volume=0.180 af Runoff Depth=0.84" Flow Length=643' Tc=13.0 min CN=53 1.46 cfs @ 12.23 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 26HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 2: Area to West Forebay Runoff = 0.83 cfs @ 12.19 hrs, Volume= 0.105 af, Depth= 0.73" Routed to Pond 2P : SWM 2 Forebay w Retention Pond Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 1.102 39 >75% Grass cover, Good, HSG A 0.216 98 Paved roads w/curbs & sewers, HSG A 0.165 98 Paved parking, HSG A 0.239 30 Woods, Good, HSG A 0.018 98 Unconnected pavement, HSG A 1.740 51 Weighted Average 1.341 77.07% Pervious Area 0.399 22.93% Impervious Area 0.018 4.51% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 60 0.0100 0.12 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 37 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 1.4 193 0.0130 2.31 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 37 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 10.3 327 Total Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 27HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 2: Area to West Forebay Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Runoff Area=1.740 ac Runoff Volume=0.105 af Runoff Depth=0.73" Flow Length=327' Tc=10.3 min CN=51 0.83 cfs @ 12.19 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 28HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 3: Area to Forebay at Great Marsh Road Runoff = 0.23 cfs @ 12.10 hrs, Volume= 0.021 af, Depth= 0.90" Routed to Pond 3P : SWM 3 Forebay w Leach Pits Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Adj Description 0.180 39 >75% Grass cover, Good, HSG A 0.068 98 Paved roads w/curbs & sewers, HSG A 0.000 98 Paved parking, HSG A 0.019 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.279 55 54 Weighted Average, UI Adjusted 0.199 71.33% Pervious Area 0.080 28.67% Impervious Area 0.012 15.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment 3: Area to Forebay at Great Marsh Road Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.26 0.25 0.24 0.23 0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Runoff Area=0.279 ac Runoff Volume=0.021 af Runoff Depth=0.90" Tc=5.0 min UI Adjusted CN=54 0.23 cfs @ 12.10 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 29HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 4: Area to Storm Filter Runoff = 0.39 cfs @ 12.11 hrs, Volume= 0.037 af, Depth= 0.84" Routed to Pond 4P : LB's from StormFilter Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.354 39 >75% Grass cover, Good, HSG A 0.062 98 Paved roads w/curbs & sewers, HSG A 0.069 98 Paved parking, HSG A 0.045 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.537 53 Weighted Average 0.399 74.30% Pervious Area 0.138 25.70% Impervious Area 0.007 5.07% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.7 70 0.0570 0.25 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 40 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 0.2 54 0.0380 3.96 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 40 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 5.5 204 Total Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:38 AMPrepared by Baxter-Nye Engineering & Survey Page 30HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 4: Area to Storm Filter Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Runoff Area=0.537 ac Runoff Volume=0.037 af Runoff Depth=0.84" Flow Length=204' Tc=5.5 min CN=53 0.39 cfs @ 12.11 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 31HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment Roof: House Roof 1210 sf Runoff = 0.14 cfs @ 12.07 hrs, Volume= 0.011 af, Depth> 4.59" Routed to Pond DW : Typical Roof Dry Well Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Area (ac) CN Description 0.028 98 Roofs, HSG A 0.028 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment Roof: House Roof 1210 sf Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95" Runoff Area=0.028 ac Runoff Volume=0.011 af Runoff Depth>4.59" Tc=5.0 min CN=98 0.14 cfs @ 12.07 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 32HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Area = 2.576 ac, 26.98% Impervious, Inflow Depth = 0.84" for 10 YR ATLAS 14 event Inflow = 1.46 cfs @ 12.23 hrs, Volume= 0.180 af Outflow = 0.37 cfs @ 13.00 hrs, Volume= 0.180 af, Atten= 74%, Lag= 46.4 min Discarded = 0.37 cfs @ 13.00 hrs, Volume= 0.180 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.04' @ 13.00 hrs Surf.Area= 1,640 sf Storage= 1,924 cf Plug-Flow detention time= 52.7 min calculated for 0.180 af (100% of inflow) Center-of-Mass det. time= 52.7 min ( 961.1 - 908.4 ) Volume Invert Avail.Storage Storage Description #1 33.00' 12,247 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 166 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 4 640 cf Overall - 226 cf Embedded = 414 cf x 40.0% Voids #3 33.25' 226 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 4 Inside #2 12,639 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 33.00 143 0 0 143 34.00 816 434 434 820 35.00 1,367 1,080 1,513 1,383 36.00 1,816 1,586 3,099 1,854 36.50 2,064 969 4,069 2,114 37.00 2,998 1,258 5,327 3,052 38.00 11,812 6,920 12,247 11,871 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #2 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.00' Excluded Wetted area = 2,267 sf #3 Primary 37.65'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.37 cfs @ 13.00 hrs HW=35.04' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.37 cfs) 2=Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 33HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)1 0 Inflow Area=2.576 ac Peak Elev=35.04' Storage=1,924 cf 1.46 cfs @ 12.23 hrs 0.37 cfs @ 13.00 hrs 0.37 cfs @ 13.00 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 34HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 2P: SWM 2 Forebay w Retention Pond Inflow Area = 1.740 ac, 22.93% Impervious, Inflow Depth = 0.73" for 10 YR ATLAS 14 event Inflow = 0.83 cfs @ 12.19 hrs, Volume= 0.105 af Outflow = 0.26 cfs @ 12.77 hrs, Volume= 0.105 af, Atten= 68%, Lag= 34.6 min Discarded = 0.26 cfs @ 12.77 hrs, Volume= 0.105 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.87' @ 12.77 hrs Surf.Area= 1,350 sf Storage= 905 cf Plug-Flow detention time= 43.0 min calculated for 0.105 af (100% of inflow) Center-of-Mass det. time= 43.0 min ( 958.1 - 915.1 ) Volume Invert Avail.Storage Storage Description #1 35.00' 10,731 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 83 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 2 320 cf Overall - 113 cf Embedded = 207 cf x 40.0% Voids #3 33.25' 113 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 2 Inside #2 10,927 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.00 471 0 0 471 36.00 1,366 880 880 1,372 37.00 2,237 1,784 2,663 2,256 38.00 3,710 2,943 5,606 3,741 39.00 6,685 5,125 10,731 6,727 Device Routing Invert Outlet Devices #1 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.75' Excluded Wetted area = 1,311 sf #2 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #3 Primary 38.75'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.26 cfs @ 12.77 hrs HW=35.87' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) 2=Exfiltration (Exfiltration Controls 0.25 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 35HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 2P: SWM 2 Forebay w Retention Pond Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=1.740 ac Peak Elev=35.87' Storage=905 cf 0.83 cfs @ 12.19 hrs 0.26 cfs @ 12.77 hrs 0.26 cfs @ 12.77 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 36HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 3P: SWM 3 Forebay w Leach Pits Inflow Area = 0.279 ac, 28.67% Impervious, Inflow Depth = 0.90" for 10 YR ATLAS 14 event Inflow = 0.23 cfs @ 12.10 hrs, Volume= 0.021 af Outflow = 0.06 cfs @ 12.58 hrs, Volume= 0.021 af, Atten= 76%, Lag= 29.3 min Discarded = 0.06 cfs @ 12.58 hrs, Volume= 0.021 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.64' @ 12.58 hrs Surf.Area= 128 sf Storage= 201 cf Plug-Flow detention time= 30.9 min calculated for 0.021 af (100% of inflow) Center-of-Mass det. time= 30.9 min ( 927.6 - 896.7 ) Volume Invert Avail.Storage Storage Description #1 34.08' 140 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 2 576 cf Overall - 226 cf Embedded = 350 cf x 40.0% Voids #2 34.58' 226 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 2 Inside #1 #3 39.60' 8,164 cf Custom Stage Data (Conic) Listed below (Recalc) 8,531 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.60 1 0 0 1 40.00 287 41 41 287 41.00 583 426 467 592 41.50 753 333 800 768 42.00 922 418 1,218 945 43.00 1,340 1,125 2,343 1,379 44.00 12,099 5,822 8,164 12,141 Device Routing Invert Outlet Devices #1 Discarded 34.08'8.270 in/hr Exfiltration over Wetted area from 34.07' - 39.50' Excluded Wetted area = 0 sf #2 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.50' - 43.50' Excluded Wetted area = 416 sf #3 Primary 43.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.06 cfs @ 12.58 hrs HW=36.64' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.06 cfs) 2=Exfiltration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=34.08' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 37HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 3P: SWM 3 Forebay w Leach Pits Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.279 ac Peak Elev=36.64' Storage=201 cf 0.23 cfs @ 12.10 hrs 0.06 cfs @ 12.58 hrs 0.06 cfs @ 12.58 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 38HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 4P: LB's from StormFilter Inflow Area = 0.537 ac, 25.70% Impervious, Inflow Depth = 0.84" for 10 YR ATLAS 14 event Inflow = 0.39 cfs @ 12.11 hrs, Volume= 0.037 af Outflow = 0.12 cfs @ 12.54 hrs, Volume= 0.037 af, Atten= 69%, Lag= 26.2 min Discarded = 0.12 cfs @ 12.54 hrs, Volume= 0.037 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 34.09' @ 12.54 hrs Surf.Area= 384 sf Storage= 291 cf Plug-Flow detention time= 16.0 min calculated for 0.037 af (100% of inflow) Center-of-Mass det. time= 16.0 min ( 917.4 - 901.4 ) Volume Invert Avail.Storage Storage Description #1 32.75' 420 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 6 1,728 cf Overall - 679 cf Embedded = 1,049 cf x 40.0% Voids #2 33.25' 679 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 6 Inside #1 #3 39.80' 4,780 cf Custom Stage Data (Conic) Listed below (Recalc) 5,878 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.80 8 0 0 8 40.00 282 22 22 282 41.00 1,676 882 904 1,680 42.00 6,620 3,876 4,780 6,629 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 38.17' Excluded Wetted area = 0 sf #2 Primary 40.91'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.12 cfs @ 12.54 hrs HW=34.09' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.12 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 39HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 4P: LB's from StormFilter Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.537 ac Peak Elev=34.09' Storage=291 cf 0.39 cfs @ 12.11 hrs 0.12 cfs @ 12.54 hrs 0.12 cfs @ 12.54 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 10 YR ATLAS 14 Rainfall=4.95"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 40HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond DW: Typical Roof Dry Well Inflow Area = 0.028 ac,100.00% Impervious, Inflow Depth > 4.59" for 10 YR ATLAS 14 event Inflow = 0.14 cfs @ 12.07 hrs, Volume= 0.011 af Outflow = 0.02 cfs @ 11.62 hrs, Volume= 0.011 af, Atten= 86%, Lag= 0.0 min Discarded = 0.02 cfs @ 11.62 hrs, Volume= 0.011 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 32.01' @ 12.56 hrs Surf.Area= 0.002 ac Storage= 0.003 af Plug-Flow detention time= 41.4 min calculated for 0.011 af (100% of inflow) Center-of-Mass det. time= 41.3 min ( 803.1 - 761.8 ) Volume Invert Avail.Storage Storage Description #1 29.50' 0.003 af 10.00'W x 10.00'L x 4.50'H Prismatoid 0.010 af Overall - 0.003 af Embedded = 0.008 af x 40.0% Voids #2 30.00' 0.003 af 6.00'D x 4.00'H Vertical Cone/Cylinder Inside #1 0.006 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 29.50'8.270 in/hr Exfiltration over Surface area from 29.40' - 34.33' Excluded Surface area = 0.000 ac Discarded OutFlow Max=0.02 cfs @ 11.62 hrs HW=29.55' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.02 cfs) Pond DW: Typical Roof Dry Well Inflow Discarded Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Inflow Area=0.028 ac Peak Elev=32.01' Storage=0.003 af 0.14 cfs @ 12.07 hrs 0.02 cfs @ 11.62 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 41HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Time span=5.00-40.00 hrs, dt=0.01 hrs, 3501 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Runoff Area=2.576 ac 26.98% Impervious Runoff Depth=1.32"Subcatchment 1: Area to Forebay by South Flow Length=643' Tc=13.0 min CN=53 Runoff=2.67 cfs 0.284 af Runoff Area=1.740 ac 22.93% Impervious Runoff Depth=1.18"Subcatchment 2: Area to West Forebay Flow Length=327' Tc=10.3 min CN=51 Runoff=1.65 cfs 0.170 af Runoff Area=0.279 ac 28.67% Impervious Runoff Depth=1.40"Subcatchment 3: Area to Forebay at Great Tc=5.0 min UI Adjusted CN=54 Runoff=0.41 cfs 0.032 af Runoff Area=0.537 ac 25.70% Impervious Runoff Depth=1.32"Subcatchment 4: Area to Storm Filter Flow Length=204' Tc=5.5 min CN=53 Runoff=0.72 cfs 0.059 af Runoff Area=0.028 ac 100.00% Impervious Runoff Depth>5.51"Subcatchment Roof: House Roof 1210 sf Tc=5.0 min CN=98 Runoff=0.17 cfs 0.013 af Peak Elev=36.26' Storage=3,975 cf Inflow=2.67 cfs 0.284 afPond 1P: SWM 1 Forebay w Retention Pond Discarded=0.45 cfs 0.284 af Primary=0.00 cfs 0.000 af Outflow=0.45 cfs 0.284 af Peak Elev=36.66' Storage=2,145 cf Inflow=1.65 cfs 0.170 afPond 2P: SWM 2 Forebay w Retention Pond Discarded=0.30 cfs 0.170 af Primary=0.00 cfs 0.000 af Outflow=0.30 cfs 0.170 af Peak Elev=39.88' Storage=382 cf Inflow=0.41 cfs 0.032 afPond 3P: SWM 3 Forebay w Leach Pits Discarded=0.09 cfs 0.032 af Primary=0.00 cfs 0.000 af Outflow=0.09 cfs 0.032 af Peak Elev=35.37' Storage=618 cf Inflow=0.72 cfs 0.059 afPond 4P: LB's from StormFilter Discarded=0.17 cfs 0.059 af Primary=0.00 cfs 0.000 af Outflow=0.17 cfs 0.059 af Peak Elev=32.72' Storage=0.004 af Inflow=0.17 cfs 0.013 afPond DW: Typical Roof Dry Well Outflow=0.02 cfs 0.013 af Total Runoff Area = 5.160 ac Runoff Volume = 0.558 af Average Runoff Depth = 1.30" 74.03% Pervious = 3.820 ac 25.97% Impervious = 1.340 ac Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 42HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: Area to Forebay by South Corner Runoff = 2.67 cfs @ 12.21 hrs, Volume= 0.284 af, Depth= 1.32" Routed to Pond 1P : SWM 1 Forebay w Retention Pond and LB's Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.453 30 Woods, Good, HSG A 1.428 39 >75% Grass cover, Good, HSG A 0.419 98 Paved roads w/curbs & sewers, HSG A 0.234 98 Paved parking, HSG A 0.042 98 Unconnected pavement, HSG A 2.576 53 Weighted Average 1.881 73.02% Pervious Area 0.695 26.98% Impervious Area 0.042 6.04% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 75 0.0160 0.15 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 1.1 45 0.0100 0.70 Shallow Concentrated Flow, B Short Grass Pasture Kv= 7.0 fps 1.7 222 0.0118 2.21 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 1.9 301 0.0030 2.69 2.11 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 Corrugated PP, smooth interior 13.0 643 Total Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 43HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 1: Area to Forebay by South Corner Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)2 1 0 Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Runoff Area=2.576 ac Runoff Volume=0.284 af Runoff Depth=1.32" Flow Length=643' Tc=13.0 min CN=53 2.67 cfs @ 12.21 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 44HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 2: Area to West Forebay Runoff = 1.65 cfs @ 12.17 hrs, Volume= 0.170 af, Depth= 1.18" Routed to Pond 2P : SWM 2 Forebay w Retention Pond Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 1.102 39 >75% Grass cover, Good, HSG A 0.216 98 Paved roads w/curbs & sewers, HSG A 0.165 98 Paved parking, HSG A 0.239 30 Woods, Good, HSG A 0.018 98 Unconnected pavement, HSG A 1.740 51 Weighted Average 1.341 77.07% Pervious Area 0.399 22.93% Impervious Area 0.018 4.51% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 60 0.0100 0.12 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 37 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 1.4 193 0.0130 2.31 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 37 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 10.3 327 Total Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 45HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 2: Area to West Forebay Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)1 0 Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Runoff Area=1.740 ac Runoff Volume=0.170 af Runoff Depth=1.18" Flow Length=327' Tc=10.3 min CN=51 1.65 cfs @ 12.17 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 46HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 3: Area to Forebay at Great Marsh Road Runoff = 0.41 cfs @ 12.09 hrs, Volume= 0.032 af, Depth= 1.40" Routed to Pond 3P : SWM 3 Forebay w Leach Pits Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Adj Description 0.180 39 >75% Grass cover, Good, HSG A 0.068 98 Paved roads w/curbs & sewers, HSG A 0.000 98 Paved parking, HSG A 0.019 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.279 55 54 Weighted Average, UI Adjusted 0.199 71.33% Pervious Area 0.080 28.67% Impervious Area 0.012 15.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment 3: Area to Forebay at Great Marsh Road Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Runoff Area=0.279 ac Runoff Volume=0.032 af Runoff Depth=1.40" Tc=5.0 min UI Adjusted CN=54 0.41 cfs @ 12.09 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 47HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 4: Area to Storm Filter Runoff = 0.72 cfs @ 12.10 hrs, Volume= 0.059 af, Depth= 1.32" Routed to Pond 4P : LB's from StormFilter Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.354 39 >75% Grass cover, Good, HSG A 0.062 98 Paved roads w/curbs & sewers, HSG A 0.069 98 Paved parking, HSG A 0.045 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.537 53 Weighted Average 0.399 74.30% Pervious Area 0.138 25.70% Impervious Area 0.007 5.07% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.7 70 0.0570 0.25 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 40 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 0.2 54 0.0380 3.96 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 40 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 5.5 204 Total Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 48HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 4: Area to Storm Filter Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Runoff Area=0.537 ac Runoff Volume=0.059 af Runoff Depth=1.32" Flow Length=204' Tc=5.5 min CN=53 0.72 cfs @ 12.10 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 49HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment Roof: House Roof 1210 sf Runoff = 0.17 cfs @ 12.07 hrs, Volume= 0.013 af, Depth> 5.51" Routed to Pond DW : Typical Roof Dry Well Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Area (ac) CN Description 0.028 98 Roofs, HSG A 0.028 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment Roof: House Roof 1210 sf Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92" Runoff Area=0.028 ac Runoff Volume=0.013 af Runoff Depth>5.51" Tc=5.0 min CN=98 0.17 cfs @ 12.07 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 50HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Area = 2.576 ac, 26.98% Impervious, Inflow Depth = 1.32" for 25 YR ATLAS 14 event Inflow = 2.67 cfs @ 12.21 hrs, Volume= 0.284 af Outflow = 0.45 cfs @ 13.32 hrs, Volume= 0.284 af, Atten= 83%, Lag= 66.7 min Discarded = 0.45 cfs @ 13.32 hrs, Volume= 0.284 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.26' @ 13.32 hrs Surf.Area= 2,198 sf Storage= 3,975 cf Plug-Flow detention time= 93.4 min calculated for 0.284 af (100% of inflow) Center-of-Mass det. time= 93.3 min ( 984.5 - 891.2 ) Volume Invert Avail.Storage Storage Description #1 33.00' 12,247 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 166 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 4 640 cf Overall - 226 cf Embedded = 414 cf x 40.0% Voids #3 33.25' 226 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 4 Inside #2 12,639 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 33.00 143 0 0 143 34.00 816 434 434 820 35.00 1,367 1,080 1,513 1,383 36.00 1,816 1,586 3,099 1,854 36.50 2,064 969 4,069 2,114 37.00 2,998 1,258 5,327 3,052 38.00 11,812 6,920 12,247 11,871 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #2 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.00' Excluded Wetted area = 2,267 sf #3 Primary 37.65'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.45 cfs @ 13.32 hrs HW=36.26' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.43 cfs) 2=Exfiltration (Exfiltration Controls 0.02 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 51HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)2 1 0 Inflow Area=2.576 ac Peak Elev=36.26' Storage=3,975 cf 2.67 cfs @ 12.21 hrs 0.45 cfs @ 13.32 hrs 0.45 cfs @ 13.32 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 52HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 2P: SWM 2 Forebay w Retention Pond Inflow Area = 1.740 ac, 22.93% Impervious, Inflow Depth = 1.18" for 25 YR ATLAS 14 event Inflow = 1.65 cfs @ 12.17 hrs, Volume= 0.170 af Outflow = 0.30 cfs @ 13.10 hrs, Volume= 0.170 af, Atten= 82%, Lag= 56.0 min Discarded = 0.30 cfs @ 13.10 hrs, Volume= 0.170 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 36.66' @ 13.10 hrs Surf.Area= 2,041 sf Storage= 2,145 cf Plug-Flow detention time= 76.0 min calculated for 0.170 af (100% of inflow) Center-of-Mass det. time= 76.0 min ( 971.9 - 895.9 ) Volume Invert Avail.Storage Storage Description #1 35.00' 10,731 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 83 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 2 320 cf Overall - 113 cf Embedded = 207 cf x 40.0% Voids #3 33.25' 113 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 2 Inside #2 10,927 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.00 471 0 0 471 36.00 1,366 880 880 1,372 37.00 2,237 1,784 2,663 2,256 38.00 3,710 2,943 5,606 3,741 39.00 6,685 5,125 10,731 6,727 Device Routing Invert Outlet Devices #1 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.75' Excluded Wetted area = 1,311 sf #2 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #3 Primary 38.75'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.30 cfs @ 13.10 hrs HW=36.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.05 cfs) 2=Exfiltration (Exfiltration Controls 0.25 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:39 AMPrepared by Baxter-Nye Engineering & Survey Page 53HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 2P: SWM 2 Forebay w Retention Pond Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)1 0 Inflow Area=1.740 ac Peak Elev=36.66' Storage=2,145 cf 1.65 cfs @ 12.17 hrs 0.30 cfs @ 13.10 hrs 0.30 cfs @ 13.10 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 54HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 3P: SWM 3 Forebay w Leach Pits Inflow Area = 0.279 ac, 28.67% Impervious, Inflow Depth = 1.40" for 25 YR ATLAS 14 event Inflow = 0.41 cfs @ 12.09 hrs, Volume= 0.032 af Outflow = 0.09 cfs @ 12.57 hrs, Volume= 0.032 af, Atten= 78%, Lag= 28.9 min Discarded = 0.09 cfs @ 12.57 hrs, Volume= 0.032 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 39.88' @ 12.57 hrs Surf.Area= 280 sf Storage= 382 cf Plug-Flow detention time= 46.9 min calculated for 0.032 af (100% of inflow) Center-of-Mass det. time= 46.9 min ( 927.3 - 880.4 ) Volume Invert Avail.Storage Storage Description #1 34.08' 140 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 2 576 cf Overall - 226 cf Embedded = 350 cf x 40.0% Voids #2 34.58' 226 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 2 Inside #1 #3 39.60' 8,164 cf Custom Stage Data (Conic) Listed below (Recalc) 8,531 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.60 1 0 0 1 40.00 287 41 41 287 41.00 583 426 467 592 41.50 753 333 800 768 42.00 922 418 1,218 945 43.00 1,340 1,125 2,343 1,379 44.00 12,099 5,822 8,164 12,141 Device Routing Invert Outlet Devices #1 Discarded 34.08'8.270 in/hr Exfiltration over Wetted area from 34.07' - 39.50' Excluded Wetted area = 0 sf #2 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.50' - 43.50' Excluded Wetted area = 416 sf #3 Primary 43.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.09 cfs @ 12.57 hrs HW=39.88' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.08 cfs) 2=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=34.08' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 55HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 3P: SWM 3 Forebay w Leach Pits Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=0.279 ac Peak Elev=39.88' Storage=382 cf 0.41 cfs @ 12.09 hrs 0.09 cfs @ 12.57 hrs 0.09 cfs @ 12.57 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 56HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 4P: LB's from StormFilter Inflow Area = 0.537 ac, 25.70% Impervious, Inflow Depth = 1.32" for 25 YR ATLAS 14 event Inflow = 0.72 cfs @ 12.10 hrs, Volume= 0.059 af Outflow = 0.17 cfs @ 12.57 hrs, Volume= 0.059 af, Atten= 76%, Lag= 28.2 min Discarded = 0.17 cfs @ 12.57 hrs, Volume= 0.059 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 35.37' @ 12.57 hrs Surf.Area= 384 sf Storage= 618 cf Plug-Flow detention time= 30.8 min calculated for 0.059 af (100% of inflow) Center-of-Mass det. time= 30.8 min ( 915.0 - 884.2 ) Volume Invert Avail.Storage Storage Description #1 32.75' 420 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 6 1,728 cf Overall - 679 cf Embedded = 1,049 cf x 40.0% Voids #2 33.25' 679 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 6 Inside #1 #3 39.80' 4,780 cf Custom Stage Data (Conic) Listed below (Recalc) 5,878 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.80 8 0 0 8 40.00 282 22 22 282 41.00 1,676 882 904 1,680 42.00 6,620 3,876 4,780 6,629 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 38.17' Excluded Wetted area = 0 sf #2 Primary 40.91'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.17 cfs @ 12.57 hrs HW=35.37' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.17 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 57HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 4P: LB's from StormFilter Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=0.537 ac Peak Elev=35.37' Storage=618 cf 0.72 cfs @ 12.10 hrs 0.17 cfs @ 12.57 hrs 0.17 cfs @ 12.57 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 25 YR ATLAS 14 Rainfall=5.92"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 58HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond DW: Typical Roof Dry Well Inflow Area = 0.028 ac,100.00% Impervious, Inflow Depth > 5.51" for 25 YR ATLAS 14 event Inflow = 0.17 cfs @ 12.07 hrs, Volume= 0.013 af Outflow = 0.02 cfs @ 11.56 hrs, Volume= 0.013 af, Atten= 89%, Lag= 0.0 min Discarded = 0.02 cfs @ 11.56 hrs, Volume= 0.013 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 32.72' @ 12.64 hrs Surf.Area= 0.002 ac Storage= 0.004 af Plug-Flow detention time= 57.6 min calculated for 0.013 af (100% of inflow) Center-of-Mass det. time= 57.5 min ( 818.3 - 760.8 ) Volume Invert Avail.Storage Storage Description #1 29.50' 0.003 af 10.00'W x 10.00'L x 4.50'H Prismatoid 0.010 af Overall - 0.003 af Embedded = 0.008 af x 40.0% Voids #2 30.00' 0.003 af 6.00'D x 4.00'H Vertical Cone/Cylinder Inside #1 0.006 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 29.50'8.270 in/hr Exfiltration over Surface area from 29.40' - 34.33' Excluded Surface area = 0.000 ac Discarded OutFlow Max=0.02 cfs @ 11.56 hrs HW=29.55' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.02 cfs) Pond DW: Typical Roof Dry Well Inflow Discarded Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Inflow Area=0.028 ac Peak Elev=32.72' Storage=0.004 af 0.17 cfs @ 12.07 hrs 0.02 cfs @ 11.56 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 59HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Time span=5.00-40.00 hrs, dt=0.01 hrs, 3501 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Runoff Area=2.576 ac 26.98% Impervious Runoff Depth=2.20"Subcatchment 1: Area to Forebay by South Flow Length=643' Tc=13.0 min CN=53 Runoff=4.87 cfs 0.472 af Runoff Area=1.740 ac 22.93% Impervious Runoff Depth=2.00"Subcatchment 2: Area to West Forebay Flow Length=327' Tc=10.3 min CN=51 Runoff=3.17 cfs 0.290 af Runoff Area=0.279 ac 28.67% Impervious Runoff Depth=2.30"Subcatchment 3: Area to Forebay at Great Tc=5.0 min UI Adjusted CN=54 Runoff=0.73 cfs 0.053 af Runoff Area=0.537 ac 25.70% Impervious Runoff Depth=2.20"Subcatchment 4: Area to Storm Filter Flow Length=204' Tc=5.5 min CN=53 Runoff=1.31 cfs 0.098 af Runoff Area=0.028 ac 100.00% Impervious Runoff Depth>6.94"Subcatchment Roof: House Roof 1210 sf Tc=5.0 min CN=98 Runoff=0.21 cfs 0.016 af Peak Elev=37.47' Storage=7,851 cf Inflow=4.87 cfs 0.472 afPond 1P: SWM 1 Forebay w Retention Pond Discarded=0.70 cfs 0.472 af Primary=0.00 cfs 0.000 af Outflow=0.70 cfs 0.472 af Peak Elev=37.72' Storage=4,842 cf Inflow=3.17 cfs 0.290 afPond 2P: SWM 2 Forebay w Retention Pond Discarded=0.38 cfs 0.290 af Primary=0.00 cfs 0.000 af Outflow=0.38 cfs 0.290 af Peak Elev=40.87' Storage=761 cf Inflow=0.73 cfs 0.053 afPond 3P: SWM 3 Forebay w Leach Pits Discarded=0.11 cfs 0.053 af Primary=0.00 cfs 0.000 af Outflow=0.11 cfs 0.053 af Peak Elev=40.34' Storage=1,272 cf Inflow=1.31 cfs 0.098 afPond 4P: LB's from StormFilter Discarded=0.24 cfs 0.098 af Primary=0.00 cfs 0.000 af Outflow=0.24 cfs 0.098 af Peak Elev=33.91' Storage=0.006 af Inflow=0.21 cfs 0.016 afPond DW: Typical Roof Dry Well Outflow=0.02 cfs 0.016 af Total Runoff Area = 5.160 ac Runoff Volume = 0.930 af Average Runoff Depth = 2.16" 74.03% Pervious = 3.820 ac 25.97% Impervious = 1.340 ac Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 60HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1: Area to Forebay by South Corner Runoff = 4.87 cfs @ 12.20 hrs, Volume= 0.472 af, Depth= 2.20" Routed to Pond 1P : SWM 1 Forebay w Retention Pond and LB's Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.453 30 Woods, Good, HSG A 1.428 39 >75% Grass cover, Good, HSG A 0.419 98 Paved roads w/curbs & sewers, HSG A 0.234 98 Paved parking, HSG A 0.042 98 Unconnected pavement, HSG A 2.576 53 Weighted Average 1.881 73.02% Pervious Area 0.695 26.98% Impervious Area 0.042 6.04% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 75 0.0160 0.15 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 1.1 45 0.0100 0.70 Shallow Concentrated Flow, B Short Grass Pasture Kv= 7.0 fps 1.7 222 0.0118 2.21 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 1.9 301 0.0030 2.69 2.11 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 Corrugated PP, smooth interior 13.0 643 Total Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 61HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 1: Area to Forebay by South Corner Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)5 4 3 2 1 0 Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Runoff Area=2.576 ac Runoff Volume=0.472 af Runoff Depth=2.20" Flow Length=643' Tc=13.0 min CN=53 4.87 cfs @ 12.20 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 62HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 2: Area to West Forebay Runoff = 3.17 cfs @ 12.16 hrs, Volume= 0.290 af, Depth= 2.00" Routed to Pond 2P : SWM 2 Forebay w Retention Pond Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 1.102 39 >75% Grass cover, Good, HSG A 0.216 98 Paved roads w/curbs & sewers, HSG A 0.165 98 Paved parking, HSG A 0.239 30 Woods, Good, HSG A 0.018 98 Unconnected pavement, HSG A 1.740 51 Weighted Average 1.341 77.07% Pervious Area 0.399 22.93% Impervious Area 0.018 4.51% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.3 60 0.0100 0.12 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 37 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 1.4 193 0.0130 2.31 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 37 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 10.3 327 Total Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 63HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 2: Area to West Forebay Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)3 2 1 0 Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Runoff Area=1.740 ac Runoff Volume=0.290 af Runoff Depth=2.00" Flow Length=327' Tc=10.3 min CN=51 3.17 cfs @ 12.16 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 64HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 3: Area to Forebay at Great Marsh Road Runoff = 0.73 cfs @ 12.08 hrs, Volume= 0.053 af, Depth= 2.30" Routed to Pond 3P : SWM 3 Forebay w Leach Pits Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Adj Description 0.180 39 >75% Grass cover, Good, HSG A 0.068 98 Paved roads w/curbs & sewers, HSG A 0.000 98 Paved parking, HSG A 0.019 30 Woods, Good, HSG A 0.012 98 Unconnected pavement, HSG A 0.279 55 54 Weighted Average, UI Adjusted 0.199 71.33% Pervious Area 0.080 28.67% Impervious Area 0.012 15.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment 3: Area to Forebay at Great Marsh Road Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Runoff Area=0.279 ac Runoff Volume=0.053 af Runoff Depth=2.30" Tc=5.0 min UI Adjusted CN=54 0.73 cfs @ 12.08 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 65HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 4: Area to Storm Filter Runoff = 1.31 cfs @ 12.09 hrs, Volume= 0.098 af, Depth= 2.20" Routed to Pond 4P : LB's from StormFilter Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.354 39 >75% Grass cover, Good, HSG A 0.062 98 Paved roads w/curbs & sewers, HSG A 0.069 98 Paved parking, HSG A 0.045 30 Woods, Good, HSG A 0.007 98 Unconnected pavement, HSG A 0.537 53 Weighted Average 0.399 74.30% Pervious Area 0.138 25.70% Impervious Area 0.007 5.07% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.7 70 0.0570 0.25 Sheet Flow, A Grass: Short n= 0.150 P2= 3.40" 0.4 40 0.0100 1.50 Shallow Concentrated Flow, B Grassed Waterway Kv= 15.0 fps 0.2 54 0.0380 3.96 Shallow Concentrated Flow, C Paved Kv= 20.3 fps 0.2 40 0.0050 3.47 2.73 Pipe Channel, D 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.012 5.5 204 Total Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 66HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Subcatchment 4: Area to Storm Filter Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)1 0 Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Runoff Area=0.537 ac Runoff Volume=0.098 af Runoff Depth=2.20" Flow Length=204' Tc=5.5 min CN=53 1.31 cfs @ 12.09 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 67HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment Roof: House Roof 1210 sf Runoff = 0.21 cfs @ 12.07 hrs, Volume= 0.016 af, Depth> 6.94" Routed to Pond DW : Typical Roof Dry Well Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Area (ac) CN Description 0.028 98 Roofs, HSG A 0.028 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Minimum Subcatchment Roof: House Roof 1210 sf Runoff Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.23 0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42" Runoff Area=0.028 ac Runoff Volume=0.016 af Runoff Depth>6.94" Tc=5.0 min CN=98 0.21 cfs @ 12.07 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 68HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Area = 2.576 ac, 26.98% Impervious, Inflow Depth = 2.20" for 100 YR ATLAS 14 event Inflow = 4.87 cfs @ 12.20 hrs, Volume= 0.472 af Outflow = 0.70 cfs @ 13.33 hrs, Volume= 0.472 af, Atten= 86%, Lag= 68.0 min Discarded = 0.70 cfs @ 13.33 hrs, Volume= 0.472 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 37.47' @ 13.33 hrs Surf.Area= 6,632 sf Storage= 7,851 cf Plug-Flow detention time= 145.3 min calculated for 0.471 af (100% of inflow) Center-of-Mass det. time= 145.3 min ( 1,019.4 - 874.1 ) Volume Invert Avail.Storage Storage Description #1 33.00' 12,247 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 166 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 4 640 cf Overall - 226 cf Embedded = 414 cf x 40.0% Voids #3 33.25' 226 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 4 Inside #2 12,639 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 33.00 143 0 0 143 34.00 816 434 434 820 35.00 1,367 1,080 1,513 1,383 36.00 1,816 1,586 3,099 1,854 36.50 2,064 969 4,069 2,114 37.00 2,998 1,258 5,327 3,052 38.00 11,812 6,920 12,247 11,871 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #2 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.00' Excluded Wetted area = 2,267 sf #3 Primary 37.65'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.70 cfs @ 13.33 hrs HW=37.47' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.43 cfs) 2=Exfiltration (Exfiltration Controls 0.26 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 69HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 1P: SWM 1 Forebay w Retention Pond and LB's Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)5 4 3 2 1 0 Inflow Area=2.576 ac Peak Elev=37.47' Storage=7,851 cf 4.87 cfs @ 12.20 hrs 0.70 cfs @ 13.33 hrs 0.70 cfs @ 13.33 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 70HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 2P: SWM 2 Forebay w Retention Pond Inflow Area = 1.740 ac, 22.93% Impervious, Inflow Depth = 2.00" for 100 YR ATLAS 14 event Inflow = 3.17 cfs @ 12.16 hrs, Volume= 0.290 af Outflow = 0.38 cfs @ 13.77 hrs, Volume= 0.290 af, Atten= 88%, Lag= 96.6 min Discarded = 0.38 cfs @ 13.77 hrs, Volume= 0.290 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 37.72' @ 13.77 hrs Surf.Area= 3,395 sf Storage= 4,842 cf Plug-Flow detention time= 145.5 min calculated for 0.290 af (100% of inflow) Center-of-Mass det. time= 145.5 min ( 1,022.7 - 877.2 ) Volume Invert Avail.Storage Storage Description #1 35.00' 10,731 cf Custom Stage Data (Conic) Listed below (Recalc) #2 32.75' 83 cf 8.00'W x 8.00'L x 2.50'H Prismatoid x 2 320 cf Overall - 113 cf Embedded = 207 cf x 40.0% Voids #3 33.25' 113 cf 6.00'D x 2.00'H Vertical Cone/Cylinder x 2 Inside #2 10,927 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 35.00 471 0 0 471 36.00 1,366 880 880 1,372 37.00 2,237 1,784 2,663 2,256 38.00 3,710 2,943 5,606 3,741 39.00 6,685 5,125 10,731 6,727 Device Routing Invert Outlet Devices #1 Discarded 35.67'2.410 in/hr Exfiltration over Wetted area from 35.67' - 38.75' Excluded Wetted area = 1,311 sf #2 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 35.67' Excluded Wetted area = 0 sf #3 Primary 38.75'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.38 cfs @ 13.77 hrs HW=37.72' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.13 cfs) 2=Exfiltration (Exfiltration Controls 0.25 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 71HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 2P: SWM 2 Forebay w Retention Pond Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)3 2 1 0 Inflow Area=1.740 ac Peak Elev=37.72' Storage=4,842 cf 3.17 cfs @ 12.16 hrs 0.38 cfs @ 13.77 hrs 0.38 cfs @ 13.77 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 72HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 3P: SWM 3 Forebay w Leach Pits Inflow Area = 0.279 ac, 28.67% Impervious, Inflow Depth = 2.30" for 100 YR ATLAS 14 event Inflow = 0.73 cfs @ 12.08 hrs, Volume= 0.053 af Outflow = 0.11 cfs @ 12.74 hrs, Volume= 0.053 af, Atten= 85%, Lag= 39.7 min Discarded = 0.11 cfs @ 12.74 hrs, Volume= 0.053 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 40.87' @ 12.74 hrs Surf.Area= 667 sf Storage= 761 cf Plug-Flow detention time= 70.3 min calculated for 0.053 af (100% of inflow) Center-of-Mass det. time= 70.3 min ( 934.3 - 864.0 ) Volume Invert Avail.Storage Storage Description #1 34.08' 140 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 2 576 cf Overall - 226 cf Embedded = 350 cf x 40.0% Voids #2 34.58' 226 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 2 Inside #1 #3 39.60' 8,164 cf Custom Stage Data (Conic) Listed below (Recalc) 8,531 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.60 1 0 0 1 40.00 287 41 41 287 41.00 583 426 467 592 41.50 753 333 800 768 42.00 922 418 1,218 945 43.00 1,340 1,125 2,343 1,379 44.00 12,099 5,822 8,164 12,141 Device Routing Invert Outlet Devices #1 Discarded 34.08'8.270 in/hr Exfiltration over Wetted area from 34.07' - 39.50' Excluded Wetted area = 0 sf #2 Discarded 39.50'2.410 in/hr Exfiltration over Wetted area from 39.50' - 43.50' Excluded Wetted area = 416 sf #3 Primary 43.50'30.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.11 cfs @ 12.74 hrs HW=40.87' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.08 cfs) 2=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=34.08' (Free Discharge) 3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 73HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 3P: SWM 3 Forebay w Leach Pits Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=0.279 ac Peak Elev=40.87' Storage=761 cf 0.73 cfs @ 12.08 hrs 0.11 cfs @ 12.74 hrs 0.11 cfs @ 12.74 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 74HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond 4P: LB's from StormFilter Inflow Area = 0.537 ac, 25.70% Impervious, Inflow Depth = 2.20" for 100 YR ATLAS 14 event Inflow = 1.31 cfs @ 12.09 hrs, Volume= 0.098 af Outflow = 0.24 cfs @ 12.34 hrs, Volume= 0.098 af, Atten= 82%, Lag= 15.0 min Discarded = 0.24 cfs @ 12.34 hrs, Volume= 0.098 af Primary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 40.34' @ 12.61 hrs Surf.Area= 1,011 sf Storage= 1,272 cf Plug-Flow detention time= 50.2 min calculated for 0.098 af (100% of inflow) Center-of-Mass det. time= 50.2 min ( 917.4 - 867.2 ) Volume Invert Avail.Storage Storage Description #1 32.75' 420 cf 8.00'W x 8.00'L x 4.50'H Prismatoid x 6 1,728 cf Overall - 679 cf Embedded = 1,049 cf x 40.0% Voids #2 33.25' 679 cf 6.00'D x 4.00'H Vertical Cone/Cylinder x 6 Inside #1 #3 39.80' 4,780 cf Custom Stage Data (Conic) Listed below (Recalc) 5,878 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 39.80 8 0 0 8 40.00 282 22 22 282 41.00 1,676 882 904 1,680 42.00 6,620 3,876 4,780 6,629 Device Routing Invert Outlet Devices #1 Discarded 32.75'8.270 in/hr Exfiltration over Wetted area from 32.74' - 38.17' Excluded Wetted area = 0 sf #2 Primary 40.91'20.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) 0.5' Crest Height Discarded OutFlow Max=0.24 cfs @ 12.34 hrs HW=39.95' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.24 cfs) Primary OutFlow Max=0.00 cfs @ 5.00 hrs HW=32.75' (Free Discharge) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 75HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Pond 4P: LB's from StormFilter Inflow Outflow Discarded Primary Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)1 0 Inflow Area=0.537 ac Peak Elev=40.34' Storage=1,272 cf 1.31 cfs @ 12.09 hrs 0.24 cfs @ 12.34 hrs 0.24 cfs @ 12.34 hrs 0.00 cfs @ 5.00 hrs Type III 24-hr 100 YR ATLAS 14 Rainfall=7.42"2020-015 PROPOSEDw Ret Ponds Printed 5/1/2026 10:59:40 AMPrepared by Baxter-Nye Engineering & Survey Page 76HydroCAD® 10.20-6a s/n 04803 © 2024 HydroCAD Software Solutions LLC Summary for Pond DW: Typical Roof Dry Well Inflow Area = 0.028 ac,100.00% Impervious, Inflow Depth > 6.94" for 100 YR ATLAS 14 event Inflow = 0.21 cfs @ 12.07 hrs, Volume= 0.016 af Outflow = 0.02 cfs @ 11.32 hrs, Volume= 0.016 af, Atten= 91%, Lag= 0.0 min Discarded = 0.02 cfs @ 11.32 hrs, Volume= 0.016 af Routing by Stor-Ind method, Time Span= 5.00-40.00 hrs, dt= 0.01 hrs Peak Elev= 33.91' @ 12.88 hrs Surf.Area= 0.002 ac Storage= 0.006 af Plug-Flow detention time= 86.8 min calculated for 0.016 af (100% of inflow) Center-of-Mass det. time= 86.7 min ( 846.5 - 759.9 ) Volume Invert Avail.Storage Storage Description #1 29.50' 0.003 af 10.00'W x 10.00'L x 4.50'H Prismatoid 0.010 af Overall - 0.003 af Embedded = 0.008 af x 40.0% Voids #2 30.00' 0.003 af 6.00'D x 4.00'H Vertical Cone/Cylinder Inside #1 0.006 af Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 29.50'8.270 in/hr Exfiltration over Surface area from 29.40' - 34.33' Excluded Surface area = 0.000 ac Discarded OutFlow Max=0.02 cfs @ 11.32 hrs HW=29.55' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.02 cfs) Pond DW: Typical Roof Dry Well Inflow Discarded Hydrograph Time (hours) 4039383736353433323130292827262524232221201918171615141312111098765Flow (cfs)0.23 0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Inflow Area=0.028 ac Peak Elev=33.91' Storage=0.006 af 0.21 cfs @ 12.07 hrs 0.02 cfs @ 11.32 hrs Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com APPENDIX E GROUNDWATER RECHARGE & WATER QUALITY • GROUNDWATER RECHARGE VOLUME CALCULATIONS • WATER QUALITY TREATMENT VOLUME CALCULATIONS • TSS REMOVAL CALCULATION WORKSHEET Stormwater Management Report Homes at Centerville Cove April 30, 2026 Centerville, Massachusetts BAXTER NYE ENGINEERING & SURVEYING 1597 Falmouth Road, Suite 1 ■ Centerville, MA 02632 Tel: 508-771-7502 ■ www.baxter-nye.com GROUNDWATER RECHARGE VOLUME CALCULATIONS (MADEP Standard 3) All site soils within area of proposed impervious cover are HSG A. Therefore, the recharge rate is: = 0.6” x total impervious area = 0.6” x 1.233 ac. = 0.7398 ac-in. = 0.0617 ac.ft. = 2,688 cf The underground Infiltration SWM Facilities are used for recharge and quantity control for post-development site runoff. 1) SWM Facility #1: Infiltration Storage Volume Provided up to Outlet Invert =7,851 cf 2) SWM Facility #2: Infiltration Storage Volume Provided up to Outlet Invert = 4,842 cf 3) SWM Facility #3: Infiltration Storage Volume Provided up to Outlet Invert = 761 cf 4) SWM Facility #4: Infiltration Storage Volume Provided up to Outlet Invert = 1,272 cf Therefore, total Volume of Recharge provided: = 14,726 cf > 2,688 cf required, therefore, design requirement is met.. The Volume of Recharge provided well exceeds the required amount of recharge. The combined BMP treatments are designed in accordance with the MDEP sizing requirements and provide the Water Quality Volume requirements. BAXTER NYE ENGINEERING AND SURVEYING 78 North St. - 3rd Floor, Hyannis, MA - Phone: 508-771-7502Great Marsh RoadCenterville, MA2020-0154/28/2026JKLElevationArea (square feet) Average Area Height (ft)Volume (Cubic Feet)Cumulative Volume (Cubic Feet)WQVolume to Forebay 134 487 244 0.0 0 035 782 635 1.0 635 63536 1,150 966 1.0 966 1,60137 2,998 2,074 1.0 2,074 3,675WQV Required: Impervious areas x 1.0 inch in APDRoadways: 18262 sfDriveways: 10200 sfSidewalk: 2228 SFTotal: 30690 sfWQV Required= 30690 sf x 1.0" = 2,557 cfVolumeO:\2020\2020-015\ADMIN\REPORTS\SWM\2020-015 WQVolume Calc.xlsx1 of 1 BAXTER NYE ENGINEERING AND SURVEYING 78 North St. - 3rd Floor, Hyannis, MA - Phone: 508-771-7502Great Marsh RoadCenterville, MA2020-0153/18/2026JKLElevationArea (square feet) Average Area Height (ft)Volume (Cubic Feet)Cumulative Volume (Cubic Feet)WQVolume to Forebay 235 471 036 769 620 1.0 620 62037 2,237 1,503 1.0 1,503 2,12338 3,710 2,974 1.0 2,974 5,097WQV Required: Impervious areas x 1.0 inch in APDRoadways: 8801 sfDriveways: 6480 sfSidewalk: 108 sfTotal: 15389 sfWQV Required= 15389 sf x 1.0" = 1,282 cfVolumeO:\2020\2020-015\ADMIN\REPORTS\SWM\2020-015 WQVolume Calc.xlsx1 of 1 BAXTER NYE ENGINEERING AND SURVEYING 78 North St. - 3rd Floor, Hyannis, MA - Phone: 508-771-7502Great Marsh RoadCenterville, MA2020-0153/20/2026JKLElevationArea (square feet) Average Area Height (ft)Volume (Cubic Feet)Cumulative Volume (Cubic Feet)WQVolume to Forebay 339.6 1 040 287 144 0.4 58 5841 583 435 1.0 435 49341.5 753 668 0.5 334 82742 954 854 0.5 427 1,25343 1,340 1,047 1.0 1,047 1,873 WQV Required: Impervious areas x 1.0 inch in APDRoadways: 5701 sfDriveways: 3000 sfSidewalk: 468 sfTotal: 9169 sfWQV Required= 9637 sf x 1.0" = 803 cfVolumeO:\2020\2020-015\ADMIN\REPORTS\SWM\2020-015 WQVolume Calc.xlsx1 of 1 Centerville Cove195 Great Marsh Road, Centerville, MAProject # 2020-015Date 4/30/26TSS REMOVAL CALCULATION WORKSHEETA B C D EBMP TSS Removal Rate Starting TSS Load * Amount Removed Remaining Load(BxC)(C-D)Sediment Forebay or StormFilter 25% 1.00 0.25 0.75Deep Sump Catch Basin 25% 0.75 0.19 0.56Retention Basin or Leaching Basins80% 0.56 0.45 0.11Total TSS Removed = 0.89Baxter Nye Engineering 2020-015 TSS Removal Spreadsheet.xls