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Stormwater Narrative - LLA - 27 Silver Circle Stormwater Management Narrative 27 Silver Circle Lot Line Adjustment 27 Silver Circle Town of Queensbury Warren County, New York Applicant: JP Gross Properties LLC 27 Silver Circle Queensbury, NY 12804 August 2022 Prepared By: The Environmental Design Partnership, LLP 900 Route 146 Clifton Park, NY 12065 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 2 TABLE OF CONTENTS Contents 1.0 Introduction ...................................................................................................................................... 3 2.0 Existing Conditions ............................................................................................................................ 3 2.1 Soil and Groundwater Conditions ................................................................................................. 3 3.0 Predevelopment Stormwater Analysis ............................................................................................. 4 4.0 Stormwater Management Planning and Practice Selection ............................................................. 5 5.0 Post-Development Stormwater Analysis .......................................................................................... 5 5.1 Stormwater Management Area #1 ..................................................................................................... 6 5.3 NYS Unified Stormwater Sizing Criteria ........................................................................................ 6 5.3.1 Water Quality (WQv) ............................................................................................................. 7 5.3.2 Runoff Reduction Volume (RRv) ............................................................................................ 7 5.3.3 Channel Protection (Cpv) ....................................................................................................... 9 5.3.4 Overbank Flood (Qp) ............................................................................................................ 10 5.3.5 Extreme Storm (Qf) .............................................................................................................. 11 6.0 Summary ............................................................................................................................................... 11 Figures Figure 1 – Site Location Map Figure 2 – Pre-development Drainage Map Figure 3 – Post-development Drainage Map Attachments Attachment A – WQv Calculations Attachment B – Stormwater Modeling Calculations 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 3 1.0 Introduction JP Gross Properties LLC is proposing a Lot Line Adjustment and expansion on an existing parcel of land totaling approximately 13.41 acres located off Silver Circle in the Town of Queensbury, New York. The proposed site development includes the construction of a 142,500 SF gravel storage and laydown area. The total area of proposed disturbance is approximately 4.60 acres and 3.27 acres of new impervious area will be added to the site. A stormwater management system has been designed to provide pollutant removal, reduce channel erosion, prevent overbank flooding, and safely control extreme flood events in accordance with the NYS Stormwater Management Design Manual (Design Manual). The proposed stormwater management system for the project will include an infiltration basin, which will provide a total storage volume of approximately 1.18 acre-feet. This narrative presents a review of the design concepts and parameters of the stormwater management system for the proposed development. The purpose of the stormwater management narrative is to assure that changes in the surface runoff characteristics, as a result of the proposed construction, will not adversely impact adjacent or downstream properties. On-site stormwater management will be implemented in accordance with the NYS Stormwater Management Design Manual to accommodate both additional stormwater runoff and to provide water quality treatment according to the green infrastructure standards. 2.0 Existing Conditions The existing project site (Figure 1) consists of a wooded area, and an upstream contributing area that was observed to be dirt surface, previous disturbed soil. The topography of the site is very flat with slopes less than 1% to 5%. Based on site investigation the majority of runoff flows to the adjacent parcel and infiltrates into the ground, with no runoff leaving the overall area. 2.1 Soil and Groundwater Conditions The USDA Soil Survey database, identifies one primary soil group, OaA – Oakville loamy fine sand 0 to 3 percent slopes. The Oakville loamy fine sand generally consists of very deep excessively drained soil with a high infiltration rate. The Soil Survey identifies the Oakville series as Hydrologic Soil Group (HSG) "A". Soil investigation in the form of test pits will be performed on the project site in the vicinity of the stormwater management area prior to construction. Test pits have been performed on the adjacent parcels for various previous site development and the soil observed was consistent with the USDA soil mapper, well drained sand with no signs of seasonal high ground water or any other limiting factors were observed. Infiltration tests were also performed on the adjacent neighboring parcels through previous development and the testes yielded very high infiltration rates in excess of 100 inches per hour in most locations. A conservative infiltration rate of 8 inches per hour was used for design purposes. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 4 3.0 Predevelopment Stormwater Analysis The existing hydrologic conditions, in the area to be disturbed as a result of the proposed construction, were analyzed using Applied Microcomputer Systems’ “HydroCAD” computer modeling program. The HydroCAD stormwater modeling program employs the United States Department of Agriculture’s Soil Conservation Service (SCS) Technical Release 20 (TR-20) method for stormwater analysis. Using this modeling technique, the site is divided into “subcatchments” that represent specific areas contributing stormwater runoff to an existing, or proposed drainage feature. The subcatchments typically flow through “reaches” (i.e., swales, channels, or pipes) that convey the stormwater to storm basins or discharge areas. A hydrologic model of the existing site was prepared using the Hydrocad program. One (1) subcatchments were used to represent the existing drainage condition, see Figure 2. The existing parameters of topography, vegetation, slope and soil type are all incorporated into the predevelopment model. Table 1 presents a summary of the pre-development stormwater peak discharge for the 1 year, 10 year and 100-year design storm events at the respective Design Points. As will be discussed in subsequent sections, the post development stormwater discharge rate has been limited to the predevelopment discharge rate for the 1-year, 10-year, and 100-year storm events. Table 1: Pre-Development Runoff Rates Storm Event Design Point Peak Discharge (cfs) Total Peak Discharge offsite (cfs) OFF1 TOTAL 1-Year (2.20") 0.00 0.00 10-Year (4.00") 0.00 0.00 50-Year (5.25”) 0.03 0.03 100-Year (6.50") 0.21 0.21 The pre-development Curve Number (CN) for the wooded land and dirt surfaces was established as 30 and 72, respectively. The HydroCAD model results for the pre-development conditions are included within Attachment B. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 5 4.0 Stormwater Management Planning and Practice Selection The site layout and stormwater design for this project was completed while taking into consideration the potential impacts on the existing site and downstream hydrology. The existing site predominately infiltrates stormwater runoff; therefore, the proposed system in this portion will rely on infiltration practices. Runoff flows across the site and infiltrates into the ground, with very minimal runoff leaving the project site. Various measures were taken to help ensure that the post-development hydrology of the site will closely resemble the pre- development hydrology. Soil restoration has been called for throughout the site in accordance with Chapter 5 of the NYSDEC Stormwater Management Design Manual. The soils on the site are classified as HSG A and need aeration and topsoil in areas of cut or fill. In high traffic areas that are to remain pervious, the soils shall be fully restored by tilling compost into the sub-soils prior to applying topsoil and vegetating. By applying these methods to the soils on the site, the original properties and porosity of the soils will be recovered, which will allow for an improvement in the soil infiltration as well as lawn and landscaping sustainability. Stormwater management on the site is designed to incorporate infiltration practices through infiltration basins. Infiltration practices are considered a standard SMP with RRv Capacity by the NYSDEC Stormwater Management Design Manual. By using infiltration practices that are located relatively close to the source of runoff, the post-development hydrology will more closely match the pre-development hydrology. 5.0 Post-Development Stormwater Analysis The post-development conditions, in the area to be disturbed as a result of the proposed construction, were analyzed using Applied Microcomputer Systems’ “HydroCAD” computer modeling program. A hydrologic model of the area to be disturbed as a result of the proposed development, was analyzed using the HydroCAD program. One (1) subcatchment was used to represent the post development drainage conditions of the site. Site improvements to the property will consist of a 142,500 SF gravel storage and laydown area. Stormwater management practices have been designed to provide storage, infiltration, and attenuation of stormwater runoff from the proposed impervious surfaces on the site. Stormwater runoff from the site will be managed with ibe (1) infiltration basin. The contributing area to the infiltration basins will include the entire proposed development including the impervious gravel area. A post-development Curve Number (CN) of 98 was assigned to all impervious surface within the proposed site. A post-development CN of 39 was assigned to all new grassed areas directly 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 6 contributing to the proposed stormwater devices. The weighted CN for the post-development conditions for the site is 78. The HydroCAD model results for the post-development conditions are included within Attachment B. 5.1 Stormwater Management Area #1 Stormwater Management Area #1 is designed as an infiltration basin in order to attenuate and infiltrate the runoff from the proposed gravel laydown area. Stormwater runoff from the gravel surface will be routed via sheet flow and shallow concentrated flow to a vegetated swale surrounding the development area. The vegetated swale will provide pretreatment of the runoff from the impervious gravel surface. The runoff will then travel through the swale and ultimately to the infiltration basin. The total area contributing to the infiltration basin SMA #1 is on the order of 4.99 acres with approximately 3.27 acres of impervious area. 100 Year Storm Runoff Volume contributing to SMA #1: 1.673 Acre-Feet Infiltration Rate: 8 Inches/Hour SMA #1 Bottom Surface Area (Taken from CAD): 7,274 ft2 Drainage Time = 1.673 Acre-Feet * 43,560 ft2/ac = 72,876 ft3 72,876 ft3/7,274 ft2 = 10 ft 10 ft * 12 in/1 ft = 120 in. 120 in/8 in/hr = ~15 Hours to drain The infiltration rate used in the HydroCAD model for the infiltration basin was a conservative 8.0 in/hr. This infiltration rate is much smaller than the rates observed on the site during infiltration testing. The infiltration basin has been designed to fully infiltrate the runoff from storm events up to and including the 100 year storm event without any discharge offsite. 5.3 NYS Unified Stormwater Sizing Criteria The proposed post-development site conditions were analyzed using Applied Microcomputer Systems’ “HydroCAD” computer modeling program, the results have been included with this report. A technical description of the HydroCAD stormwater modeling program was provided in a previous section. The area to be disturbed as a result of the proposed development was modeled under the post- development conditions using one (1) subcatchment area (Figure 3) routed into the stormwater management areas. The contributing area of each stormwater management area is identified on Figure 3. The post-development stormwater management system has been designed based on the Unified Stormwater Sizing Criteria as described in the following sections. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 7 5.3.1 Water Quality (WQv) In general, small storm events and the initial runoff from larger storm events are an environmental concern as this stormwater runoff typically contains roadway pollutants and thermal energy stored by the asphalt. In accordance with the NYS Stormwater Management Design Manual, this initial runoff is designated as the Water Quality Volume (WQv) and special attention is given to this volume of runoff to meet water quality objectives. The NYS Stormwater Management Design Manual identifies several standard practices, such as the proposed infiltration basins and shallow grassy depression which are acceptable for water quality treatment. These acceptable Stormwater Management Practices (SMPs) can capture and treat the full water quality volume (WQv), are capable of 80% TSS removal and 40% TP removal, have acceptable longevity in the field, and have pretreatment mechanism. The water quality storage volume, WQv, is calculated as follows: 12 ARPWQv v ××= Where: WQv = water quality volume (acre-feet) P = 90% rainfall event number Rv = 0.05+0.009(I), where I is percent impervious cover A = site area (acres), impervious area used with I = 100% Table 2: Required Water Quality Volume SMA # P Rv A (ac) Required WQv (cf) Provided WQv (cf) 1 1.1 0.64 4.99 12,753 31,020 TOTAL 12,753 31,020 5.3.2 Runoff Reduction Volume (RRv) The NYSSMDM specifies that the runoff shall be reduced by 100% of the site WQv using green infrastructure techniques and standard SMPs with RRv capacity unless, due to existing site constraints, the 100% reduction is not possible. Based on existing topography, and soil conditions the 100% reduction of the WQv was possible and was achieved through stormwater infiltration practices. Infiltration practices are considered a standard SMP with RRv Capacity by the NYSDEC Stormwater Management Design Manual. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 8 5.3.2.1 Stormwater Management Practices The NYSDEC stormwater management design manual recognizes the use of infiltration practices as acceptable for runoff reduction. The proposed infiltration basin will collect the stormwater runoff from the proposed impervious area and infiltrate 100% of the contributing WQv. The total runoff reduction from the infiltration practices will be on the order of 12,753 cf. Table 4: Runoff Reduction Volume Summary Runoff Reduction Technique RRv (cf) SMA#1 (Infiltration Basin) 12,753 Total Site Runoff Reduction 12,753 Required Water Quality Volume 12,753 Many of the green infrastructure practices recommended in the NYS Stormwater Management Design Manual were not applied to the stormwater management design on this site due to either site restrictions or the use of more feasible green infrastructure of standard SMP techniques in place of more restrictive and/or maintenance intensive practices. The following table discusses why the unused green infrastructure practices were not feasible. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 9 Table 5: Non-Feasible Green Infrastructure Practices Green Infrastructure Practice Reason use is not feasible Conservation of Natural Areas Existing natural areas on site will be conserved to the greatest extend possible, however the contribution to the RRV reduction is minimal. Porous Pavement Proposed practices require less maintenance and are more economically feasible when compared to porous pavement. Most drainage areas suitable for porous pavement on the project site are already conveyed to infiltration devices. Vegetated Swale Vegetated swale is proposed on the project site however contribution to the overall runoff reduction is minimal. Sheet flow to Riparian Buffers or Filter Strips No Riparian areas exist on the site or in the site perimeter. Tree Planting/Tree Pit Trees will be saved on the site as possible to conserve the natural areas. Trees will also be planted to maintain a buffer from the roadway to the proposed site, and surrounding properties though the resulting runoff reduction value for adding additional trees is minimal. Stream Daylighting No culverted/piped streams exist on the site or in the site perimeter. Rain Gardens Rain gardens are not recommended for commercial applications. Green Roofs Proposed practices require less maintenance and are more economically feasible when compared to green roofs. Stormwater Planters Proposed practices were deemed more economically feasible and effective as opposed to stormwater planters. Additionally, they require less maintenance. Rain Barrels/Cisterns Rain Barrels/Cisterns would require the ability to use the water between storm events which is not feasible for this project type. 5.3.3 Channel Protection (Cpv) In accordance with the NYS Stormwater Management Design Manual, stream channel protection, designed to protect stream channels from erosion, is accomplished by providing 24- hour extended detention of the one-year, 24-hour storm event. The Cpv requirement is typically satisfied by providing additional storage above the water quality (WQv) volume. The one-year storm event was analyzed using the HydroCAD stormwater modeling program (TR-20) under the post development drainage conditions shown on Figure 3. Using a one-year, 24-hour design storm of 2.20 inches the required Cpv was calculated as presented in Table 6. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 10 Table 6: Channel Protection Volume Summary 1-Year Design Storm (in) Cpv (ft3) Cpv (provided) (ft3) SMA#1 2.20 10,890 18,267 Total 10,890 18,267 5.3.4 Overbank Flood (Qp) Overbank Flood Control Criteria has been established to limit the frequency and magnitude of out-of-bank flooding generated through changes in runoff characteristics as a result of increased impervious surface area. In accordance with the NYS Stormwater Management Design Manual, providing sufficient storage volume to attenuate the post development 10- year, 24-hour peak discharge rate to the equivalent pre-development discharge rate controls overbank flooding. The 10-year design storm event was analyzed using the HydroCAD stormwater modeling program (TR-20) under the post-development drainage conditions shown on Figure 3. Using a 10-year, 24-hour design storm of 4.00 inches, the stormwater management areas were designed with sufficient storage volume to limit the post-development 10-year, 24-hour peak discharge rate to the pre-development discharge rate. The following table presents the pre- and post-development discharge rates for the offsite discharge. As indicated, the post- development discharge rate is equal to the pre-development rate as required. Table 7: Overbank Flow Runoff Summary Design Point 10-year (4.00”) runoff rate (cfs) Predevelopment Post-Development OFF1 0.00 0.00 TOTAL 0.00 0.00 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 11 5.3.5 Extreme Storm (Qf) In accordance with the NYS Stormwater Management Design Manual, the stormwater management system must attenuate the post development 100-year, 24-hour peak discharge rate to the predevelopment rate while providing safe passage of this storm event. The 100-year storm event was analyzed using the HydroCAD stormwater modeling program (TR-20) under the post-development drainage conditions shown in Figure 3. Using a 100-year, 24-hour design storm of 6.50 inches, the stormwater management areas were designed with sufficient storage volume to limit the post-development 100-year, 24-hour peak discharge rate to the predevelopment discharge rate. The following table presents the pre and post- development discharge rates for the offsite discharge. As indicated, the post-development discharge rate is less than the predevelopment rate as required. Table 8: Extreme Storm Runoff Summary Design Point 100-year (6.50”) runoff rate (cfs) Predevelopment Post-Development OFF1 0.21 0.05 TOTAL 0.21 0.05 6.0 Summary Development of the proposed property will change the stormwater drainage characteristics of the site; impervious area will be added and the site will be re-graded to support the proposed improvements. Changes to the stormwater drainage characteristics of the site have been evaluated in accordance with the NYS Stormwater Management Design Manual. The proposed stormwater management system has been designed to comply with the recommendations in the Design Manual related to water quality, runoff reduction, channel protection, overbank flood control and extreme flood control for new development projects. The proposed stormwater management system has been designed to attenuate and treat the stormwater runoff generated from the contributing areas for storm events up to and including the 100-year design storm event. The proposed stormwater management design includes the use of infiltration basins and pocket pond ponds. Extended detention storage will be provided above the required water quality volume to meet detention (Qp) requirements. Stormwater modeling results, based on the proposed site layout, indicate the ability to reduce the overall post-development discharge rate from the site as summarized in Table 10. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 12 Table 10: Post Development Stormwater Peak Discharge Rates Peak Discharge Rates in cfs 1-Year Storm 10-Year Storm 50-Year Storm 100-Year Storm Pre-Development 0.00 0.00 0.03 0.21 Post-Development 0.00 0.00 0.00 0.05 Overall Reduction (cfs) 0.00 0.00 0.03 0.16 Through the implementation of acceptable stormwater management practices, recommended by the NYS Stormwater Management Design Manual, the proposed project will not adversely affect adjacent or downstream properties. Prepared by: The Environmental Design Partnership, LLP Nicholas Zeglen, P.E. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 13 REFERENCES HydroCAD version 8.50, Applied Microcomputer Systems, Chocura, New Hampshire. NYSDEC, 1990. “Technical and Operational Guidance Series (5.1.8) Stormwater Management Guidelines for New Development”, New York State Department of Environmental Conservation, Division of Water. NYSDEC, 1992. “Reducing the Impacts of Stormwater Runoff from New Development”, New York State Department of Environmental Conservation, Division of Water. NYSDEC, 2015. “New York State Stormwater Management Design Manual”, Center for Watershed Protection, Ellicott City, MD. Rawls, W.J., Brakensiek, D.L., and Saxton, K. E., 1982. “Estimation of Soil Properties”, Transactions of the American Society of Agricultural Engineers, Vol. 25, No. J, pp. 1316-1320. S.C.S., 1982. “TR-20 Project Formulation-Hydrology, Technical Release No. 20”, U.S. Department of Agriculture, Soil Conservation Service, Hydrology Unit Division of Engineering. United States Department of Agriculture, Web Soil Survey. Retrieved from https://websoilsurvey.sc.egov.usda.gov 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 14 Figures 1. Site Location map 2. Site Soils Data 3. Pre-Development Drainage Map 4. Post-Development Drainage Map 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 15 Figure 1: Site Location Map SITE LOCATION Hydrologic Soil Group—Warren County, New York Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2022 Page 1 of 44793730479376047937904793820479385047938804793730479376047937904793820479385047938804793910606400606430606460606490606520606550606580606610606640606670 606400 606430 606460 606490 606520 606550 606580 606610 606640 606670 43° 17' 25'' N 73° 41' 18'' W43° 17' 25'' N73° 41' 5'' W43° 17' 19'' N 73° 41' 18'' W43° 17' 19'' N 73° 41' 5'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 0 50 100 200 300 Feet 0 15 30 60 90 Meters Map Scale: 1:1,310 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available 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 1:15,800. 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: Warren County, New York Survey Area Data: Version 21, Sep 1, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 1, 2020—Oct 1, 2020 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. Hydrologic Soil Group—Warren County, New York Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2022 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI OaA Oakville loamy fine sand, 0 to 3 percent slopes A 2.6 51.4% OaB Oakville loamy fine sand, 3 to 8 percent slopes A 2.4 48.6% Totals for Area of Interest 5.0 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—Warren County, New York Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8/12/2022 Page 3 of 4 Satelite dishCIRFIPFCIRF1" = 100'PREDEVELOPMENTANALYSIS1 of 2STORMWATER ANALYSIS FOR SILVER CIRCLE ROAD TOWN OF QUEENSBURY JULY 29, 2021 27 SILVER CIRCLE WARREN COUNTY, NEW YORK 900 Route 146 Clifton Park, New York 12065 edpllp.com(518) 371-7621 E N V I R O N M E N T A L D E S I G N P A R T N E R S H I P, L L P. Satelite dishCIRFIPFCIRF1" = 100'POSTDEVELOPMENTANALYSIS2 of 2STORMWATER ANALYSIS FOR SILVER CIRCLE ROAD TOWN OF QUEENSBURY JULY 29, 2021 27 SILVER CIRCLE WARREN COUNTY, NEW YORK 900 Route 146 Clifton Park, New York 12065 edpllp.com(518) 371-7621 E N V I R O N M E N T A L D E S I G N P A R T N E R S H I P, L L P. 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 16 Attachment A Water Quality Calculation Runoff Reduction Calculation Water Quality Volume (WQv) Calculations Project: Date: SMA I.D. AREA (SF) I (SF) I (%) Rv WQv (cu-ft) WQv Provided (cu-ft) SMA 1 217,350 142,511 66% 0.64 12,753 31,020 Totals 217,350 142,511 12,753 31,020 27 Silver Circle LLA 8/12/2022ENVIRONMENTAL DESIGN PARTNERSHIP, LLP 900 Route 146 Clifton Park, New York 12065 Phone:(518) 371-7621 FAX:(518) 371-9540 WQv calcs Page 1 Runoff Reduction Volume (RRv) Calculations Project: Date: 4.99 acres P = 1.1 in I= 66 % WQv = 12,753 cf Rv = 0.64 I.D. SMA#1 12,753 cf 0 cf 12,753 cf 100% Reduction from GI = Reduction from Standard SMPs = Total Overall RRv = % Min. Reduction= 27 Silver Circle LLA 8/12/2022 Total Site Area = % Reduction Max Reduction (cf) (Contributing WQv) 12,753 Reduction (cf) Stormwater Management Practices Infiltration WQv Provided (cf) 31,020 100 12,753 ENVIRONMENTAL DESIGN PARTNERSHIP, LLP 900 Route 146 Clifton Park, New York 12065 Phone:(518) 371-7621 FAX:(518) 371-9540 R:\WARREN\QUEENSBURY\Silver Circle\27-Gross\06-Engineering\LLA - Stormwater\RRv-Calcs LLA.xls 8/12/2022 900 Route 146, Clifton Park, New York 12065 phone (518) 371-7621 e-mail: info@edpllp.com 17 Attachment B Stormwater Modeling Calculations 1S OFF1 TOTAL TOTAL PREDEVELOPMENT RUNOFF Routing Diagram for STORMWATER PREDEVELOPMENT_GROSS SILVER CIRCLE Prepared by EDP, Printed 8/12/2022 HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link STORMWATER PREDEVELOPMENT_GROSS SILVER CIRCLE Printed 8/12/2022Prepared by EDP Page 2HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Rainfall Events Listing Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 1 YEAR Type II 24-hr Default 24.00 1 2.20 2 2 10 YEAR Type II 24-hr Default 24.00 1 4.00 2 3 50 YEAR Type II 24-hr Default 24.00 1 5.25 2 4 100 YEAR Type II 24-hr Default 24.00 1 6.50 2 STORMWATER PREDEVELOPMENT_GROSS SILVER CIRCLE Printed 8/12/2022Prepared by EDP Page 3HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 0.303 72 Dirt roads, HSG A (1S) 4.687 30 Woods, Good, HSG A (1S) 4.990 33 TOTAL AREA STORMWATER PREDEVELOPMENT_GROSS SILVER CIRCLE Printed 8/12/2022Prepared by EDP Page 4HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Soil Listing (all nodes) Area (acres) Soil Group Subcatchment Numbers 4.990 HSG A 1S 0.000 HSG B 0.000 HSG C 0.000 HSG D 0.000 Other 4.990 TOTAL AREA Type II 24-hr 1 YEAR Rainfall=2.20"STORMWATER PREDEVELOPMENT_GROSS SILVER Printed 8/12/2022Prepared by EDP Page 5HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 1 YEAR Rainfall=2.20" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 204,148 30 Woods, Good, HSG A 217,350 33 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 1 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 1 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=4.00"STORMWATER PREDEVELOPMENT_GROSS SILVER Printed 8/12/2022Prepared by EDP Page 6HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=4.00" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 204,148 30 Woods, Good, HSG A 217,350 33 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 50 YEAR Rainfall=5.25"STORMWATER PREDEVELOPMENT_GROSS SILVER Printed 8/12/2022Prepared by EDP Page 7HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 0.03 cfs @ 17.92 hrs, Volume= 0.027 af, Depth= 0.07" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 50 YEAR Rainfall=5.25" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 204,148 30 Woods, Good, HSG A 217,350 33 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.07" for 50 YEAR event Inflow = 0.03 cfs @ 17.92 hrs, Volume= 0.027 af Primary = 0.03 cfs @ 17.92 hrs, Volume= 0.027 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.07" for 50 YEAR event Inflow = 0.03 cfs @ 17.92 hrs, Volume= 0.027 af Primary = 0.03 cfs @ 17.92 hrs, Volume= 0.027 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 100 YEAR Rainfall=6.50"STORMWATER PREDEVELOPMENT_GROSS SILVE Printed 8/12/2022Prepared by EDP Page 8HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 0.21 cfs @ 12.71 hrs, Volume= 0.109 af, Depth= 0.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 100 YEAR Rainfall=6.50" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 204,148 30 Woods, Good, HSG A 217,350 33 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.26" for 100 YEAR event Inflow = 0.21 cfs @ 12.71 hrs, Volume= 0.109 af Primary = 0.21 cfs @ 12.71 hrs, Volume= 0.109 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.26" for 100 YEAR event Inflow = 0.21 cfs @ 12.71 hrs, Volume= 0.109 af Primary = 0.21 cfs @ 12.71 hrs, Volume= 0.109 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs 1S 1P SMA#1 OFF1 TOTAL TOTAL PREDEVELOPMENT RUNOFF Routing Diagram for STORMWATER POSTDEVELOPMENT_GROSS SILVER CIRCLE Prepared by EDP, Printed 8/12/2022 HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Subcat Reach Pond Link STORMWATER POSTDEVELOPMENT_GROSS SILVER CIRCLE Printed 8/12/2022Prepared by EDP Page 2HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Rainfall Events Listing Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 1 YEAR Type II 24-hr Default 24.00 1 2.20 2 2 10 YEAR Type II 24-hr Default 24.00 1 4.00 2 3 50 YEAR Type II 24-hr Default 24.00 1 5.25 2 4 100 YEAR Type II 24-hr Default 24.00 1 6.50 2 STORMWATER POSTDEVELOPMENT_GROSS SILVER CIRCLE Printed 8/12/2022Prepared by EDP Page 3HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 1.415 39 >75% Grass cover, Good, HSG A (1S) 0.303 72 Dirt roads, HSG A (1S) 3.272 96 Gravel surface, HSG A (1S) 4.990 78 TOTAL AREA STORMWATER POSTDEVELOPMENT_GROSS SILVER CIRCLE Printed 8/12/2022Prepared by EDP Page 4HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Soil Listing (all nodes) Area (acres) Soil Group Subcatchment Numbers 4.990 HSG A 1S 0.000 HSG B 0.000 HSG C 0.000 HSG D 0.000 Other 4.990 TOTAL AREA Type II 24-hr 1 YEAR Rainfall=2.20"STORMWATER POSTDEVELOPMENT_GROSS SILVER Printed 8/12/2022Prepared by EDP Page 5HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 2.48 cfs @ 12.23 hrs, Volume= 0.250 af, Depth= 0.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 1 YEAR Rainfall=2.20" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 142,511 96 Gravel surface, HSG A 61,637 39 >75% Grass cover, Good, HSG A 217,350 78 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Pond 1P: SMA#1 Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.60" for 1 YEAR event Inflow = 2.48 cfs @ 12.23 hrs, Volume= 0.250 af Outflow = 1.39 cfs @ 12.50 hrs, Volume= 0.250 af, Atten= 44%, Lag= 15.9 min Discarded = 1.39 cfs @ 12.50 hrs, Volume= 0.250 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Peak Elev= 376.18' @ 12.50 hrs Surf.Area= 7,488 sf Storage= 1,323 cf Plug-Flow detention time= 7.0 min calculated for 0.250 af (100% of inflow) Center-of-Mass det. time= 7.0 min ( 895.7 - 888.7 ) Volume Invert Avail.Storage Storage Description #1 376.00' 51,420 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 376.00 7,274 0 0 377.00 8,465 7,870 7,870 378.00 9,712 9,089 16,958 379.00 11,858 10,785 27,743 379.25 14,354 3,277 31,020 380.50 18,287 20,401 51,420 Type II 24-hr 1 YEAR Rainfall=2.20"STORMWATER POSTDEVELOPMENT_GROSS SILVER Printed 8/12/2022Prepared by EDP Page 6HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Device Routing Invert Outlet Devices #1 Discarded 376.00'8.000 in/hr Exfiltration over Surface area #2 Primary 379.25'10.0' long x 10.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64 Discarded OutFlow Max=1.39 cfs @ 12.50 hrs HW=376.18' (Free Discharge) 1=Exfiltration (Exfiltration Controls 1.39 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=376.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 1 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 1 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=4.00"STORMWATER POSTDEVELOPMENT_GROSS SILVE Printed 8/12/2022Prepared by EDP Page 7HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 8.65 cfs @ 12.21 hrs, Volume= 0.785 af, Depth= 1.89" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YEAR Rainfall=4.00" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 142,511 96 Gravel surface, HSG A 61,637 39 >75% Grass cover, Good, HSG A 217,350 78 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Pond 1P: SMA#1 Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 1.89" for 10 YEAR event Inflow = 8.65 cfs @ 12.21 hrs, Volume= 0.785 af Outflow = 1.67 cfs @ 12.89 hrs, Volume= 0.785 af, Atten= 81%, Lag= 40.9 min Discarded = 1.67 cfs @ 12.89 hrs, Volume= 0.785 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Peak Elev= 377.46' @ 12.89 hrs Surf.Area= 9,040 sf Storage= 11,908 cf Plug-Flow detention time= 56.3 min calculated for 0.784 af (100% of inflow) Center-of-Mass det. time= 56.3 min ( 910.1 - 853.8 ) Volume Invert Avail.Storage Storage Description #1 376.00' 51,420 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 376.00 7,274 0 0 377.00 8,465 7,870 7,870 378.00 9,712 9,089 16,958 379.00 11,858 10,785 27,743 379.25 14,354 3,277 31,020 380.50 18,287 20,401 51,420 Type II 24-hr 10 YEAR Rainfall=4.00"STORMWATER POSTDEVELOPMENT_GROSS SILVE Printed 8/12/2022Prepared by EDP Page 8HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Device Routing Invert Outlet Devices #1 Discarded 376.00'8.000 in/hr Exfiltration over Surface area #2 Primary 379.25'10.0' long x 10.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64 Discarded OutFlow Max=1.67 cfs @ 12.89 hrs HW=377.46' (Free Discharge) 1=Exfiltration (Exfiltration Controls 1.67 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=376.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 10 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 50 YEAR Rainfall=5.25"STORMWATER POSTDEVELOPMENT_GROSS SILVE Printed 8/12/2022Prepared by EDP Page 9HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 13.53 cfs @ 12.21 hrs, Volume= 1.216 af, Depth= 2.93" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 50 YEAR Rainfall=5.25" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 142,511 96 Gravel surface, HSG A 61,637 39 >75% Grass cover, Good, HSG A 217,350 78 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Pond 1P: SMA#1 Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 2.93" for 50 YEAR event Inflow = 13.53 cfs @ 12.21 hrs, Volume= 1.216 af Outflow = 1.98 cfs @ 13.04 hrs, Volume= 1.216 af, Atten= 85%, Lag= 50.0 min Discarded = 1.98 cfs @ 13.04 hrs, Volume= 1.216 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Peak Elev= 378.44' @ 13.04 hrs Surf.Area= 10,666 sf Storage= 21,487 cf Plug-Flow detention time= 97.8 min calculated for 1.216 af (100% of inflow) Center-of-Mass det. time= 97.8 min ( 939.0 - 841.2 ) Volume Invert Avail.Storage Storage Description #1 376.00' 51,420 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 376.00 7,274 0 0 377.00 8,465 7,870 7,870 378.00 9,712 9,089 16,958 379.00 11,858 10,785 27,743 379.25 14,354 3,277 31,020 380.50 18,287 20,401 51,420 Type II 24-hr 50 YEAR Rainfall=5.25"STORMWATER POSTDEVELOPMENT_GROSS SILVE Printed 8/12/2022Prepared by EDP Page 10HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Device Routing Invert Outlet Devices #1 Discarded 376.00'8.000 in/hr Exfiltration over Surface area #2 Primary 379.25'10.0' long x 10.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64 Discarded OutFlow Max=1.98 cfs @ 13.04 hrs HW=378.44' (Free Discharge) 1=Exfiltration (Exfiltration Controls 1.98 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=376.00' (Free Discharge) 2=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 50 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 50 YEAR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 100 YEAR Rainfall=6.50"STORMWATER POSTDEVELOPMENT_GROSS SILV Printed 8/12/2022Prepared by EDP Page 11HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Runoff = 18.61 cfs @ 12.20 hrs, Volume= 1.673 af, Depth= 4.02" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Type II 24-hr 100 YEAR Rainfall=6.50" Area (sf) CN Description 13,202 72 Dirt roads, HSG A 142,511 96 Gravel surface, HSG A 61,637 39 >75% Grass cover, Good, HSG A 217,350 78 Weighted Average 217,350 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.2 100 0.0150 0.32 Sheet Flow, SHEET Fallow n= 0.050 P2= 2.50" 4.3 260 0.0100 1.00 Shallow Concentrated Flow, Nearly Bare & Untilled Kv= 10.0 fps 17.4 740 0.0200 0.71 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 26.9 1,100 Total Summary for Pond 1P: SMA#1 Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 4.02" for 100 YEAR event Inflow = 18.61 cfs @ 12.20 hrs, Volume= 1.673 af Outflow = 2.72 cfs @ 13.01 hrs, Volume= 1.673 af, Atten= 85%, Lag= 48.5 min Discarded = 2.66 cfs @ 13.01 hrs, Volume= 1.672 af Primary = 0.05 cfs @ 13.01 hrs, Volume= 0.001 af Routing by Stor-Ind method, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Peak Elev= 379.26' @ 13.01 hrs Surf.Area= 14,391 sf Storage= 31,187 cf Plug-Flow detention time= 126.3 min calculated for 1.673 af (100% of inflow) Center-of-Mass det. time= 126.3 min ( 958.4 - 832.1 ) Volume Invert Avail.Storage Storage Description #1 376.00' 51,420 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 376.00 7,274 0 0 377.00 8,465 7,870 7,870 378.00 9,712 9,089 16,958 379.00 11,858 10,785 27,743 379.25 14,354 3,277 31,020 380.50 18,287 20,401 51,420 Type II 24-hr 100 YEAR Rainfall=6.50"STORMWATER POSTDEVELOPMENT_GROSS SILV Printed 8/12/2022Prepared by EDP Page 12HydroCAD® 10.10-3a s/n 11387 © 2020 HydroCAD Software Solutions LLC Device Routing Invert Outlet Devices #1 Discarded 376.00'8.000 in/hr Exfiltration over Surface area #2 Primary 379.25'10.0' long x 10.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64 Discarded OutFlow Max=2.66 cfs @ 13.01 hrs HW=379.26' (Free Discharge) 1=Exfiltration (Exfiltration Controls 2.66 cfs) Primary OutFlow Max=0.03 cfs @ 13.01 hrs HW=379.26' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 0.03 cfs @ 0.27 fps) Summary for Link OFF1: Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 100 YEAR event Inflow = 0.05 cfs @ 13.01 hrs, Volume= 0.001 af Primary = 0.05 cfs @ 13.01 hrs, Volume= 0.001 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs Summary for Link TOTAL: TOTAL PREDEVELOPMENT RUNOFF Inflow Area = 4.990 ac, 0.00% Impervious, Inflow Depth = 0.00" for 100 YEAR event Inflow = 0.05 cfs @ 13.01 hrs, Volume= 0.001 af Primary = 0.05 cfs @ 13.01 hrs, Volume= 0.001 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-200.00 hrs, dt= 0.05 hrs