Loading...
HomeMy WebLinkAbout20170321 Stormwater Report 1160 GREAT POND ROAD Perf Arts Ctr STORMWATERANALYSIS For Center for the Arts at Brooks School 1160 Great Pond Road North Andover, MA January 13, 2017 SITE Prepared for: Brooks School 1160 Great Pond Road North Andover, MA, 01845 Prepared by: Whitman & Bingham Associates, LLC 510 Mechanic Street Leominster, MA 01453 Tel. 978-537-5296Fax. 978-537-1423 TABLE OF CONTENTS 1.0)Drainage Narrative 1.1)Introduction 1.2)Method of Analysis 1.3)Soils 1.4)Runoff Curve Numbers 1.5)Design Criteria 1.6)Hydrologic Descriptions 1.6.1)Pre-Development Conditions 1.6.2)Post-Development Conditions 1.7)Conclusions 2.0)Hydrological Calculations Pre-Development Post –Development 3.0)Soil Map Figures Figure 1 -Pre-development Watershed Delineation Figure 2 -Post-development Watershed Delineation Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 1.0 STORMWATERNARRATIVE Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 1.0 NARRATIVE 1.1INTRODUCTION As part of the design of redevelopment of the area of Brooks School Center for the Arts in North Andover,Whitman & Bingham Associates, LLC, has prepared this StormwaterAnalysis, relative to the reconstructionof existing developed areas. The purpose of this report is to compare the pre-construction drainage conditions to the post-construction drainage conditions relative to increases in runoff generally associated with the increase of impervious surfaces. The subject site is located on the westside of Great Pond Road and contains the existing main campus of Brooks School.The existing subject site isdeveloped with existing buildings, walkways,recreation areas,parkingand driveways.The applicant proposes to redevelop portions of the site consistingof the removal and reconstruction of buildings, pedestrian and vehicular access ways, parking and landscape area.A complete description of the project is shown on plans, entitled “Brooks School Center forthe Arts”,prepared byAnnBeha Architects, A.T. Leonard and Associates and Whitman and Bingham Associates. 1.2 METHOD OF ANALYSIS The enclosed hydrologic calculations utilize the runoff estimating techniques developed by the USDA Soil Conservation Service (SCS). The following publications were used in the preparation of this report: 1 1. “Urban Hydrology for Small Watersheds” 2 2. “National Engineering Handbook, Hydrology, Section 4” (NEH-4) 3. “Atlas of Precipitation Extremes for the Northeastern United States and Southeastern 3 Canada” Using SCS publications and other texts on surface water hydrology, in conjunction with drainage 4 software “HydroCAD” developed by Applied Microcomputer Systems, Whitman & Bingham Associates, LLC has calculated peak rates of runoff relative to the subject site. The drainage software program “HydroCAD” calculates peak rates of runoff similarly to the computer program known as “Computer Programs for Project Formulations Hydrology, Technical Release Number 20” (TR-20), developed by SCS. Times of concentration are computed by using the “Upland Method” which calculates times of concentrations utilizing land use and slope in conjunction with other land use variables. Time of concentration is the time requiredfor a droplet of water to travel from the most hydraulically distant point of the subwatershed to the design point. It is computed by summing the times it takes the water to travel through the different components of the subwatershed drainage system. Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis As a result of urbanization of an area (increase of impervious area), time of concentration will be decreased since velocity of overland flow will be increased. Therefore, as time of concentration is decreased, the hydrographic peak will be increased forthat particular subwatershed. The time of concentration (Tc) is a major hydrograph shape parameter. The hydrograph peak for a subwatershed area is attenuated and shifted to the right with an increase in Tc. The "upland method" translates to more accurate Tc’s than other general methods. 1.3 SOILS Generally, soils are classified from A through D, with A being very pervious (i.e. gravels, etc.) and D being very impervious (i.e. clays, muck, peat, etc.). The four (4) soil classifications as defined by SCS are: Group AGenerally have low runoff potential and have high infiltration rates. This group includes mainly sands and gravels consisting of deep, well to excessively drained media (sand, loamy sand, or sandy loam). Group BSoils in this classification have moderate infiltration rates and contain well-drained soils with moderately fine to moderately coarse textures (silt loam or loam). Group CThese soils have low infiltration rates and generally consist of a soil layer that prevents downward movement of water to the water table (sandy, clay, loam). Group DSoils under this group have high runoff potential since they are chiefly clay soils with high expansive capability. High water table, clay layers, nearly impervious material are all associated with this classification (clay loam, silty clay loam, sand clay, silty clay, or clay). Soils throughout the subject site were classified by the Soil Conservation Service (SCS) as the following 5 soil groups: Soil GroupHydrologic Runoff Class Charlton, SuttonB Paxton, LeicesterC Whitman, Freetown muckD The soil groups have been hydrological classified as B, Cand D, which have moderate to highrunoff potential. These soils are described by the Soil Conservation Service in the preceding paragraph. Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 1.4 RUNOFF CURVE NUMBERS There are several major factors affecting the amount of runoff that can be expected from a particular land use. They include treatment, cover type, hydrologic condition, and antecedent runoff condition. Hydraulic condition represents the effects of cover type and treatment on infiltration and runoff. Density of plant cover and forest litter heavily influences this condition. Good hydraulic condition indicates a low run-off potential due to heavy ground cover while poor hydraulic condition indicates poor cover (i.e. bare soil, etc.) and is indicative of high runoff potential. As the curve number increases the amount of expected runoff is also increased. A curve number of 30 indicates a low potential for runoff while a number of 90 indicates a high potential. Curve numbers were selected for the various soil types and land uses found on the site in accordance with the following table. Weighted curve numbers for each subwatershed were determined by land area of the different soil types. The SCS runoff curve numbers used in all watershed modeling contained in this report are based upon the following Hydrologic Soil Group and their following land uses: SURFACE TYPEHYDROLOGICAL SOIL GROUP A B C D CURVE NUMBERS Pavement98989898 Grass/Lawn-Good39617480 Grass/Lawn-Fair49697984 Grass/Lawn-Poor68798689 Wooded-Good30557077 Wooded-Fair36607379 Wooded-Poor45667783 Meadow-Fair30587178 Dirt Roads72828789 Gravel Road76858991 Residential 1 Acre Zoning51687984 Residential 1/3 Acre Zoning57728186 Residential 1/2 Acre Zoning54708085 Residential 2 Acre Zoning46657782 Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 1.5 DESIGN CRITERIA This drainage analysis was developed utilizing a Type III, 24-hour tropical storm as developed by SCS. Type III represents Gulf of Mexico and Atlantic Coastal areas where tropical storms yield large 24-hour rainfall amounts. The storm frequencies and thecorresponding rainfall depths were compiled from the North Andover Stormwater Management Regulations: Storm Frequency (years)Rainfall Depth (inches) 1008.6 256.0 104.8 23.2 The maximum overall hydrologic impact of development was evaluated using the 100-year storm as recommended by various engineering publications in designing detention basins. The stormwater pipes have been designed to handle the 25-year storm. Calculations relative to the 2, 10,25, and 100-year storms are provided in section 2.0 herein 1.6 HYDROLOGICAL DESCRIPTIONS The stormwater run-off of the project area is tributary to a wetland system and low lying detention area at the northeast portion of the property(Design Point 1)and to a wetland system in the northwest portion of the property(Design Point 2).These wetland and detention areas are located along the west side of Great Pond Road. The stormwater analysiswas limited to theseportionsof the campus. The main focus of the assessment was to analyze the flow ratesto these stormwater collection areasand also the water levels associated with the existing northeast wetland system and detention area. This wetland system and existing detention area ultimately discharge to Lake Cochichewick via a closed pipe network whereas the northwest wetland system flows away from the lake. The stormwater of the campus is routed to the existing collection areasby overland flow and a series of pipe networks.Additionally it appears as though land on the northeast side of Great Pond Road is hydraulically connected to the detention area by means of a culvert under the road. It is expected that some level of stormwater detaining occurs on the northeast side ofthe road but without further field surveying, this would not be accurately assessed. For the purpose of this assessment a detailed survey and analysis of all stormwater collection components was not performed. The existing condition, pre-development, calculations were based upon the campus conditions prior to that of the Chapel and Connector Drive Improvement Project that was approved and constructed in 2014. These improvements were included into the proposed condition, post-development, calculations. The analysis area was separated into four sub-watersheds where individual hydrographs were determined and combined at the appropriate points to compare the total flows at the design points mentioned. (See Figures 1 & 2 for delineation). Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis Subwatershed 1–Existing Detention Area This subwatershed encompasses the areas of the campus that flow to the existing detention area along Great Pond Road and on the north side of the southern entrance to the campus. The majority of this area is developed with areas of buildings, tennis courts, driveways, walkways, lawn and landscape areas. The topography of the area ranges from moderate (10% ±)within the Chapel area, to gentle (2% ±)within the detention area. The southern side of the proposed Arts Center reconstruction and the previous Chapel improvement project are within this watershed.There is a slight decrease in the total area of this watershed (0.2 acres) due to grading alterations along the western edge of the Arts project. The Arts Project and previous Chapel improvements result in an increase in impervious surface of approximately4,400 sq. ft. Although the detention area is over 1,000-ft away from Lake Cochichewick, its discharge is through a closed pipe network towards the Lake. Subwatershed 2–Existing Northeast Wetland Area This subwatershed encompasses the areas of the campus that flow to the existing wetland area along Great Pond Road, near the existing tennis courts. The majority of this area is developed with areas of buildings, tennis courts, driveways, walkways, lawn and landscape areas. The topography of the area ranges from moderate (10% ±) along the wetland area, to gentle (2% ±) along the existing play area. The easternside of the proposed Arts Center reconstructionand previous connector drive improvements arewithin this watershed. There is a slight decrease in the total area of this watershed (0.071acres) due to thenew building addition roof drain collection system which discharges to north of the addition. The Arts Project and previous Chapel improvementsresult in a decrease in impervioussurface of approximately 840sq. ft. Stormwater entering this area, in excess of the capacity of the wetland area, would then overflow into that of the adjacent detentionarea. Subwatershed 3–Northeast Side of Great Pond Road This subwatershed encompasses the areaon the northeast side of Great Pond Road, across from the Brooks School main campus.This area is hydraulically connected to the detention area by means of a culvert under the road. The majority of this area is undeveloped with mostly woods and some areas ofbuildings, road and lawn areas. The topography of the area ranges from steep (20%±) within the eastern woodlandarea, to gentle (2% ±) along the low area adjacent to Great Pond Road. Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis This area remains unchanged from the current Arts Center Project of the Chapel improvements. This watershed was included in the analysis to better assess the flows and elevationsof the existing detention area as it is connected through a culvert across Great Pond Road. Subwatershed 4–Existing NorthwestWetland Area This subwatershed encompasses the areas of the campus that flow to the existing wetland area along Great Pond Road, near the ice hockey arena. The majority of this area is developed with areas of buildings, recreation fields, driveways, parking, walkways, lawn and landscape areas. The topography of the area ranges from steep(33% ±) alongthe hockey arena, to gentle (2% ±) within the recreation field areas. The northernside of the proposed Arts Center reconstructionwith courtyard area and parking landscape improvementseast of the dining hall, are within this watershed. There is a slight increasein the total area of this watershed (0.278acres) due to the alterations of stormwater patterns of the new building addition roof and regrading mentioned in the other watersheds. The Arts Project and parking area landscapeimprovementsresult in an increase in impervious surface of approximately 3,800sq. ft. Although, this impervious surface increase is only due to slight shifting of stormwater pattern and not added impervious surface to the campus. The proposed improvements of the Arts Center project result in an approximate increase in impervious surface of 330 sq. ft. The previously approved Chapel/Connector Road project included approximately 8,670 sq.ft. of added impervious surface, with a combined total increaseof 9,000 sq. ft. of impervious surface. Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 1.7 CONCLUSIONS A summary of the existing and proposed stormwater flows are shown in the following tables: TABLE I Peak Flows ExitingExisting Detention Area Storm EventExisting Proposed Conditions Conditions (cfs)(cfs) 100 yr. storm6.286.27 25 yr. storm5.355.34 10-yr storm4.974.97 2 yr. storm4.384.38 Peak Flows Entering Northwest Wetland Area Storm EventExisting Proposed Conditions Conditions (cfs)(cfs) 100 yr. storm171.99173.22 25 yr. storm100.40101.11 10-yr storm68.9469.43 2 yr. storm30.7130.93 TABLE II Peak Water Elevation Existing Detention Area Storm EventExisting Proposed Conditions Conditions (ft)(ft) 100 yr. storm173.4173.4 25 yr. storm171.8171.7 10-yr storm171.2171.2 2 yr. storm170.3170.3 The actual peak flows and elevations associated with the detention area stormwater are expected to be lower than shown as the detention of stormwater on the northeast side of Great Pond Road was not accounted for. Although there are increases in impervious surface as part of the projectand slight shifting of drainage areas, the alterationsare minor in comparison to the tributary watershed areas, such that the post development rates are consistent with the existing. Also, the expected water height withinthe detention areawould be unchanged. Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis The Chapel Project included multiple bio-retention areas to provide for recharge and treatment of stormwater of the campus. The minimum total design volume of the bio-retention areasfor the increase in impervious surfacewere based upon the following: Combined Projects Net increase in Impervious Area = 9,000 sq. ft 6,645 impervious in “B” soil group 2,355 impervious in “C” soil group Target Depth Factor (F) –0.35 inches (B soil) Target Depth Factor (F) –0.25 inches (C soil) The minimum recharge volume is as follows (Static Method): Rv = F x impervious area Rv = (0.35 in/12 in/ft)(6,645)+ (0.25 in/12 in/ft)(2,355) = 243 cu. ft. The volume of run-off to be treated for water quality is based upon 1.0 inches of run-off times the total impervious area. V= (D/12 inches/foot) * (A) WQWQIMP V= (1.0 inch/12 inches/foot) * (9,000 sq. ft.) = 750 cu. ft. WQ The combined volume provided by the proposed bio-retentionareas of the Chapel Project was approximately 2,200 cu. ft. This volume isgreater than the required water quality or recharge volume for that of both the Chapel and Art Center Projects.At the time of the Chapel Project, the bio-retention areas had been sized to accommodate that project as well as future added impervious surfaces with an overall total increase of 26,400 sq. ft. of impervious. Additionally, to provide further treatment and recharge of existing impervious areas, a proposed landscape island, within the existing parking area behind the Dining Hall, is to be utilized as a bio- retention area.This area has an approximate storage volume of 300 cu. ft.This volume relates to the treatment of approximately 3,600sq. ft. of impervious surface. V= (D/12 inches/foot) * (A) WQWQIMP 300 cu. ft.= (1.0 inch/12 inches/foot) * (A) IMP (A) = 3,600 sq. ft. IMP Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 2.0 HYDROLOGICAL CALCULATIONS Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 2.1 PRE-CONDITIONS Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 4S2S1S3S Trib Area to northTrib Area to eastTrib Area to DetentionNE Side Great Pond Rd wetlands wetlands area 2R (new Reach) DP22P1P north wetlandsWetland AreaDetention area DP1 outlet pipe Drainage Diagram for brooks school pre-arts Reach SubcatPond Link Prepared by Whitman & Bingham Associates 1/16/2017 HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school pre-arts Page 2 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.977 ac Runoff Depth=0.93" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=10.10 cfs 1.005 af Runoff Area=7.257 ac Runoff Depth=1.27" Subcatchment 2S: Trib Area to east wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=9.39 cfs 0.770 af Runoff Area=25.120 ac Runoff Depth=0.52" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=7.58 cfs 1.087 af Runoff Area=38.926 ac Runoff Depth=1.04" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=30.71 cfs 3.366 af Inflow=16.48 cfs 2.093 af Reach 2R: (new Reach) Outflow=16.48 cfs 2.093 af Inflow=4.38 cfs 2.959 af Reach DP1: outlet pipe Outflow=4.38 cfs 2.959 af Inflow=30.71 cfs 3.366 af Reach DP2: north wetlands Outflow=30.71 cfs 3.366 af Peak Elev=170.33' Storage=20,741 cf Inflow=16.48 cfs 2.093 af Pond 1P: Detention area Discarded=0.25 cfs 0.101 af Primary=4.38 cfs 2.959 af Secondary=0.00 cfs 0.000 af Outflow=4.63 cfs 3.060 af Peak Elev=170.04' Storage=33,540 cf Inflow=9.39 cfs 0.770 af Pond 2P: Wetland Area Outflow=0.00 cfs 0.000 af Total Runoff Area = 84.280 ac Runoff Volume = 6.228 af Average Runoff Depth = 0.89" Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school pre-arts Page 3 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=10.10 cfs @ 12.21 hrs, Volume=1.005 af, Depth=0.93" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Area (ac)CNDescription 2.73698Paved parking & roofs 4.67861>75% Grass cover, Good, HSG B 3.73474>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.60055Woods, Good, HSG B 0.13670Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.97772Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to east wetlands Runoff=9.39 cfs @ 12.14 hrs, Volume=0.770 af, Depth=1.27" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Area (ac)CNDescription 1.50298Paved parking & roofs 0.24961>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.09055Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.25778Weighted Average Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school pre-arts Page 4 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=7.58 cfs @ 12.35 hrs, Volume=1.087 af, Depth=0.52" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=30.71 cfs @ 12.28 hrs, Volume=3.366 af, Depth=1.04" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school pre-arts Page 5 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.32598Paved parking & roofs 12.60661>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 38.92674Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =38.097 ac, Inflow Depth = 0.66" for 2 yr n andover event Inflow=16.48 cfs @ 12.26 hrs, Volume=2.093 af Outflow=16.48 cfs @ 12.31 hrs, Volume=2.093 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=4.38 cfs @ 13.05 hrs, Volume=2.959 af Outflow=4.38 cfs @ 13.10 hrs, Volume=2.959 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =38.926 ac, Inflow Depth = 1.04" for 2 yr n andover event Inflow=30.71 cfs @ 12.28 hrs, Volume=3.366 af Outflow=30.71 cfs @ 12.33 hrs, Volume=3.366 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school pre-arts Page 6 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=16.48 cfs @ 12.31 hrs, Volume=2.093 af Outflow=4.63 cfs @ 13.05 hrs, Volume=3.060 af, Atten= 72%, Lag= 43.9 min Discarded=0.25 cfs @ 13.05 hrs, Volume=0.101 af Primary=4.38 cfs @ 13.05 hrs, Volume=2.959 af Secondary=0.00 cfs @ 0.00 hrs, Volume=0.000 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 170.33' @ 13.05 hrs Surf.Area= 39,978 sf Storage= 20,741 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 118.9 min ( 1,018.9 - 899.9 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.25 cfs @ 13.05 hrs HW=170.33' (Free Discharge) (Exfiltration Controls 0.25 cfs) 3=Exfiltration Max=4.38 cfs @ 13.05 hrs HW=170.33' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 4.38 cfs @ 5.6 fps) 1=Culvert Max=0.00 cfs @ 0.00 hrs HW=169.50' TW=169.00' (Dynamic Tailwater) Secondary OutFlow ( Controls 0.00 cfs) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=9.39 cfs @ 12.14 hrs, Volume=0.770 af Outflow=0.00 cfs @ 0.00 hrs, Volume=0.000 af, Atten= 100%, Lag= 0.0 min Primary=0.00 cfs @ 0.00 hrs, Volume=0.000 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school pre-arts Page 7 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 170.04' @ 24.55 hrs Surf.Area= 47,149 sf Storage= 33,540 cf Plug-Flow detention time= (not calculated: initial storage excedes outflow) Center-of-Mass det. time= (not calculated: no outflow) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=0.00 cfs @ 0.00 hrs HW=169.00' TW=169.50' (Dynamic Tailwater) Primary OutFlow ( Controls 0.00 cfs) 1=Broad-Crested Rectangular Weir Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school pre-arts Page 8 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.977 ac Runoff Depth=2.05" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=23.81 cfs 2.212 af Runoff Area=7.257 ac Runoff Depth=2.54" Subcatchment 2S: Trib Area to east wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=19.14 cfs 1.538 af Runoff Area=25.120 ac Runoff Depth=1.38" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=25.67 cfs 2.897 af Runoff Area=38.926 ac Runoff Depth=2.21" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=68.94 cfs 7.155 af Inflow=47.52 cfs 5.108 af Reach 2R: (new Reach) Outflow=47.52 cfs 5.108 af Inflow=4.97 cfs 5.628 af Reach DP1: outlet pipe Outflow=4.97 cfs 5.628 af Inflow=68.94 cfs 7.155 af Reach DP2: north wetlands Outflow=68.94 cfs 7.155 af Peak Elev=171.16' Storage=69,157 cf Inflow=47.52 cfs 5.649 af Pond 1P: Detention area Discarded=0.46 cfs 0.342 af Primary=4.97 cfs 5.643 af Secondary=12.43 cfs 0.851 af Outflow=17.86 cfs 6.837 af Peak Elev=170.99' Storage=86,194 cf Inflow=19.14 cfs 2.389 af Pond 2P: Wetland Area Outflow=1.24 cfs 0.541 af Total Runoff Area = 84.280 ac Runoff Volume = 13.801 af Average Runoff Depth = 1.97" Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school pre-arts Page 9 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=23.81 cfs @ 12.20 hrs, Volume=2.212 af, Depth=2.05" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Area (ac)CNDescription 2.73698Paved parking & roofs 4.67861>75% Grass cover, Good, HSG B 3.73474>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.60055Woods, Good, HSG B 0.13670Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.97772Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to east wetlands Runoff=19.14 cfs @ 12.13 hrs, Volume=1.538 af, Depth=2.54" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Area (ac)CNDescription 1.50298Paved parking & roofs 0.24961>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.09055Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.25778Weighted Average Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school pre-arts Page 10 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=25.67 cfs @ 12.29 hrs, Volume=2.897 af, Depth=1.38" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=68.94 cfs @ 12.27 hrs, Volume=7.155 af, Depth=2.21" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school pre-arts Page 11 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.32598Paved parking & roofs 12.60661>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 38.92674Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =38.097 ac, Inflow Depth = 1.61" for 10 yr n andover event Inflow=47.52 cfs @ 12.24 hrs, Volume=5.108 af Outflow=47.52 cfs @ 12.29 hrs, Volume=5.108 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=4.97 cfs @ 12.77 hrs, Volume=5.628 af Outflow=4.97 cfs @ 12.82 hrs, Volume=5.628 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =38.926 ac, Inflow Depth = 2.21" for 10 yr n andover event Inflow=68.94 cfs @ 12.27 hrs, Volume=7.155 af Outflow=68.94 cfs @ 12.32 hrs, Volume=7.155 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school pre-arts Page 12 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=47.52 cfs @ 12.29 hrs, Volume=5.649 af Outflow=17.86 cfs @ 12.77 hrs, Volume=6.837 af, Atten= 62%, Lag= 28.8 min Discarded=0.46 cfs @ 12.77 hrs, Volume=0.342 af Primary=4.97 cfs @ 12.77 hrs, Volume=5.643 af Secondary=12.43 cfs @ 12.77 hrs, Volume=0.851 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 171.16' @ 12.77 hrs Surf.Area= 73,501 sf Storage= 69,157 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 176.2 min ( 1,069.3 - 893.1 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.46 cfs @ 12.77 hrs HW=171.16' (Free Discharge) (Exfiltration Controls 0.46 cfs) 3=Exfiltration Max=4.97 cfs @ 12.77 hrs HW=171.16' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 4.97 cfs @ 6.3 fps) 1=Culvert Max=12.36 cfs @ 12.77 hrs HW=171.16' TW=170.29' (Dynamic Tailwater) Secondary OutFlow (Weir Controls 12.36 cfs @ 1.4 fps) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=19.14 cfs @ 12.13 hrs, Volume=2.389 af Outflow=1.24 cfs @ 16.45 hrs, Volume=0.541 af, Atten= 93%, Lag= 259.3 min Primary=1.24 cfs @ 16.45 hrs, Volume=0.541 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school pre-arts Page 13 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 170.99' @ 15.36 hrs Surf.Area= 63,176 sf Storage= 86,194 cf Plug-Flow detention time= 391.8 min calculated for 0.540 af (23% of inflow) Center-of-Mass det. time= 282.2 min ( 1,097.8 - 815.6 ) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=1.31 cfs @ 16.45 hrs HW=170.97' TW=170.95' (Dynamic Tailwater) Primary OutFlow (Weir Controls 1.31 cfs @ 0.5 fps) 1=Broad-Crested Rectangular Weir Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school pre-arts Page 14 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.977 ac Runoff Depth=2.99" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=35.29 cfs 3.237 af Runoff Area=7.257 ac Runoff Depth=3.58" Subcatchment 2S: Trib Area to east wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=26.91 cfs 2.164 af Runoff Area=25.120 ac Runoff Depth=2.18" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=42.37 cfs 4.556 af Runoff Area=38.926 ac Runoff Depth=3.18" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=100.40 cfs 10.331 af Inflow=74.98 cfs 7.793 af Reach 2R: (new Reach) Outflow=74.98 cfs 7.793 af Inflow=5.35 cfs 7.860 af Reach DP1: outlet pipe Outflow=5.35 cfs 7.860 af Inflow=100.40 cfs 10.331 af Reach DP2: north wetlands Outflow=100.40 cfs 10.331 af Peak Elev=171.76' Storage=117,131 cf Inflow=74.98 cfs 18.492 af Pond 1P: Detention area Discarded=0.55 cfs 0.662 af Primary=5.35 cfs 7.860 af Secondary=37.79 cfs 10.386 af Outflow=43.45 cfs 18.908 af Peak Elev=171.77' Storage=140,441 cf Inflow=43.79 cfs 12.551 af Pond 2P: Wetland Area Outflow=38.07 cfs 10.699 af Total Runoff Area = 84.280 ac Runoff Volume = 20.288 af Average Runoff Depth = 2.89" Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school pre-arts Page 15 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=35.29 cfs @ 12.20 hrs, Volume=3.237 af, Depth=2.99" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Area (ac)CNDescription 2.73698Paved parking & roofs 4.67861>75% Grass cover, Good, HSG B 3.73474>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.60055Woods, Good, HSG B 0.13670Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.97772Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to east wetlands Runoff=26.91 cfs @ 12.13 hrs, Volume=2.164 af, Depth=3.58" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Area (ac)CNDescription 1.50298Paved parking & roofs 0.24961>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.09055Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.25778Weighted Average Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school pre-arts Page 16 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=42.37 cfs @ 12.28 hrs, Volume=4.556 af, Depth=2.18" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=100.40 cfs @ 12.26 hrs, Volume=10.331 af, Depth=3.18" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school pre-arts Page 17 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.32598Paved parking & roofs 12.60661>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 38.92674Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =38.097 ac, Inflow Depth = 2.45" for 25 yr n andover event Inflow=74.98 cfs @ 12.24 hrs, Volume=7.793 af Outflow=74.98 cfs @ 12.29 hrs, Volume=7.793 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=5.35 cfs @ 16.00 hrs, Volume=7.860 af Outflow=5.35 cfs @ 16.05 hrs, Volume=7.860 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =38.926 ac, Inflow Depth = 3.18" for 25 yr n andover event Inflow=100.40 cfs @ 12.26 hrs, Volume=10.331 af Outflow=100.40 cfs @ 12.31 hrs, Volume=10.331 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school pre-arts Page 18 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=74.98 cfs @ 12.29 hrs, Volume=18.492 af Outflow=43.45 cfs @ 12.61 hrs, Volume=18.908 af, Atten= 42%, Lag= 19.4 min Discarded=0.55 cfs @ 16.00 hrs, Volume=0.662 af Primary=5.35 cfs @ 16.00 hrs, Volume=7.860 af Secondary=37.79 cfs @ 12.61 hrs, Volume=10.386 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 171.76' @ 16.00 hrs Surf.Area= 87,269 sf Storage= 117,131 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 97.3 min ( 1,078.4 - 981.2 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.55 cfs @ 16.00 hrs HW=171.75' (Free Discharge) (Exfiltration Controls 0.55 cfs) 3=Exfiltration Max=5.35 cfs @ 16.00 hrs HW=171.75' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 5.35 cfs @ 6.8 fps) 1=Culvert Max=37.68 cfs @ 12.61 hrs HW=171.44' TW=170.85' (Dynamic Tailwater) Secondary OutFlow (Weir Controls 37.68 cfs @ 2.0 fps) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=43.79 cfs @ 12.57 hrs, Volume=12.551 af Outflow=38.07 cfs @ 15.92 hrs, Volume=10.699 af, Atten= 13%, Lag= 200.9 min Primary=38.07 cfs @ 15.92 hrs, Volume=10.699 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school pre-arts Page 19 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 171.77' @ 16.10 hrs Surf.Area= 75,895 sf Storage= 140,441 cf Plug-Flow detention time= 157.6 min calculated for 10.682 af (85% of inflow) Center-of-Mass det. time= 105.1 min ( 1,070.1 - 965.1 ) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=35.72 cfs @ 15.92 hrs HW=171.74' TW=171.65' (Dynamic Tailwater) Primary OutFlow (Weir Controls 35.72 cfs @ 1.2 fps) 1=Broad-Crested Rectangular Weir Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school pre-arts Page 20 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.977 ac Runoff Depth=5.22" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=61.72 cfs 5.650 af Runoff Area=7.257 ac Runoff Depth=5.95" Subcatchment 2S: Trib Area to east wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=44.19 cfs 3.597 af Runoff Area=25.120 ac Runoff Depth=4.15" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=83.75 cfs 8.679 af Runoff Area=38.926 ac Runoff Depth=5.47" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=171.99 cfs 17.730 af Inflow=140.84 cfs 14.329 af Reach 2R: (new Reach) Outflow=140.84 cfs 14.329 af Inflow=6.28 cfs 9.912 af Reach DP1: outlet pipe Outflow=6.28 cfs 9.912 af Inflow=171.99 cfs 17.730 af Reach DP2: north wetlands Outflow=171.99 cfs 17.730 af Peak Elev=173.40' Storage=284,720 cf Inflow=216.23 cfs 114.203 af Pond 1P: Detention area Discarded=0.72 cfs 1.012 af Primary=6.28 cfs 9.935 af Secondary=202.02 cfs 100.405 af Outflow=208.99 cfs 111.353 af Peak Elev=173.44' Storage=290,889 cf Inflow=203.28 cfs 103.765 af Pond 2P: Wetland Area Outflow=210.41 cfs 99.873 af Total Runoff Area = 84.280 ac Runoff Volume = 35.656 af Average Runoff Depth = 5.08" Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school pre-arts Page 21 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=61.72 cfs @ 12.19 hrs, Volume=5.650 af, Depth=5.22" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Area (ac)CNDescription 2.73698Paved parking & roofs 4.67861>75% Grass cover, Good, HSG B 3.73474>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.60055Woods, Good, HSG B 0.13670Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.97772Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to east wetlands Runoff=44.19 cfs @ 12.13 hrs, Volume=3.597 af, Depth=5.95" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Area (ac)CNDescription 1.50298Paved parking & roofs 0.24961>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.09055Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.25778Weighted Average Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school pre-arts Page 22 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=83.75 cfs @ 12.27 hrs, Volume=8.679 af, Depth=4.15" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=171.99 cfs @ 12.26 hrs, Volume=17.730 af, Depth=5.47" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school pre-arts Page 23 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.32598Paved parking & roofs 12.60661>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 38.92674Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =38.097 ac, Inflow Depth = 4.51" for 100 yr n andover event Inflow=140.84 cfs @ 12.23 hrs, Volume=14.329 af Outflow=140.84 cfs @ 12.28 hrs, Volume=14.329 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=6.28 cfs @ 17.35 hrs, Volume=9.912 af Outflow=6.28 cfs @ 17.40 hrs, Volume=9.912 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =38.926 ac, Inflow Depth = 5.47" for 100 yr n andover event Inflow=171.99 cfs @ 12.26 hrs, Volume=17.730 af Outflow=171.99 cfs @ 12.31 hrs, Volume=17.730 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school pre-arts Page 24 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=216.23 cfs @ 17.07 hrs, Volume=114.203 af Outflow=208.99 cfs @ 17.17 hrs, Volume=111.353 af, Atten= 3%, Lag= 6.2 min Discarded=0.72 cfs @ 17.35 hrs, Volume=1.012 af Primary=6.28 cfs @ 17.35 hrs, Volume=9.935 af Secondary=202.02 cfs @ 17.17 hrs, Volume=100.405 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 173.40' @ 17.35 hrs Surf.Area= 114,514 sf Storage= 284,720 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 28.8 min ( 1,208.9 - 1,180.1 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.71 cfs @ 17.35 hrs HW=173.38' (Free Discharge) (Exfiltration Controls 0.71 cfs) 3=Exfiltration Max=6.28 cfs @ 17.35 hrs HW=173.38' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 6.28 cfs @ 8.0 fps) 1=Culvert Max=187.27 cfs @ 17.17 hrs HW=173.29' TW=172.94' (Dynamic Tailwater) Secondary OutFlow (Weir Controls 187.27 cfs @ 2.2 fps) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=203.28 cfs @ 16.97 hrs, Volume=103.765 af Outflow=210.41 cfs @ 17.27 hrs, Volume=99.873 af, Atten= 0%, Lag= 17.8 min Primary=210.41 cfs @ 17.27 hrs, Volume=99.873 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school pre-arts Page 25 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 173.44' @ 17.25 hrs Surf.Area= 105,005 sf Storage= 290,889 cf Plug-Flow detention time= 54.6 min calculated for 99.873 af (96% of inflow) Center-of-Mass det. time= 33.0 min ( 1,228.7 - 1,195.7 ) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=200.24 cfs @ 17.27 hrs HW=173.33' TW=172.93' (Dynamic Tailwater) Primary OutFlow (Weir Controls 200.24 cfs @ 2.4 fps) 1=Broad-Crested Rectangular Weir 2.2 POST-CONDITIONS Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 4S2S1S3S Trib Area to northTrib Area to wetlandsTrib Area to DetentionNE Side Great Pond Rd wetlands area 2R (new Reach) DP22P1P north wetlandsWetland AreaDetention area DP1 outlet pipe Drainage Diagram for brooks school art center post cd Reach SubcatPond Link Prepared by Whitman & Bingham Associates 1/16/2017 HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school art center post cd Page 2 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.770 ac Runoff Depth=0.93" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=9.94 cfs 0.989 af Runoff Area=7.186 ac Runoff Depth=1.27" Subcatchment 2S: Trib Area to wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=9.29 cfs 0.763 af Runoff Area=25.120 ac Runoff Depth=0.52" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=7.58 cfs 1.087 af Runoff Area=39.204 ac Runoff Depth=1.04" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=30.93 cfs 3.390 af Inflow=16.33 cfs 2.077 af Reach 2R: (new Reach) Outflow=16.33 cfs 2.077 af Inflow=4.38 cfs 2.956 af Reach DP1: outlet pipe Outflow=4.38 cfs 2.956 af Inflow=30.93 cfs 3.390 af Reach DP2: north wetlands Outflow=30.93 cfs 3.390 af Peak Elev=170.32' Storage=20,451 cf Inflow=16.33 cfs 2.077 af Pond 1P: Detention area Discarded=0.25 cfs 0.100 af Primary=4.38 cfs 2.956 af Secondary=0.00 cfs 0.000 af Outflow=4.62 cfs 3.056 af Peak Elev=170.03' Storage=33,211 cf Inflow=9.29 cfs 0.763 af Pond 2P: Wetland Area Outflow=0.00 cfs 0.000 af Total Runoff Area = 84.280 ac Runoff Volume = 6.229 af Average Runoff Depth = 0.89" Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school art center post cd Page 3 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=9.94 cfs @ 12.21 hrs, Volume=0.989 af, Depth=0.93" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Area (ac)CNDescription 2.83898Paved parking & roofs 4.46161>75% Grass cover, Good, HSG B 3.68974>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.56255Woods, Good, HSG B 0.12770Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.77072Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to wetlands Runoff=9.29 cfs @ 12.14 hrs, Volume=0.763 af, Depth=1.27" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Area (ac)CNDescription 1.52198Paved parking & roofs 0.17661>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.07355Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.18678Weighted Average Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school art center post cd Page 4 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=7.58 cfs @ 12.35 hrs, Volume=1.087 af, Depth=0.52" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=30.93 cfs @ 12.28 hrs, Volume=3.390 af, Depth=1.04" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school art center post cd Page 5 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.41098Paved parking & roofs 12.79961>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 39.20474Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =37.890 ac, Inflow Depth = 0.66" for 2 yr n andover event Inflow=16.33 cfs @ 12.27 hrs, Volume=2.077 af Outflow=16.33 cfs @ 12.32 hrs, Volume=2.077 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=4.38 cfs @ 13.04 hrs, Volume=2.956 af Outflow=4.38 cfs @ 13.09 hrs, Volume=2.956 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =39.204 ac, Inflow Depth = 1.04" for 2 yr n andover event Inflow=30.93 cfs @ 12.28 hrs, Volume=3.390 af Outflow=30.93 cfs @ 12.33 hrs, Volume=3.390 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school art center post cd Page 6 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=16.33 cfs @ 12.32 hrs, Volume=2.077 af Outflow=4.62 cfs @ 13.04 hrs, Volume=3.056 af, Atten= 72%, Lag= 43.6 min Discarded=0.25 cfs @ 13.04 hrs, Volume=0.100 af Primary=4.38 cfs @ 13.04 hrs, Volume=2.956 af Secondary=0.00 cfs @ 0.00 hrs, Volume=0.000 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 170.32' @ 13.04 hrs Surf.Area= 39,655 sf Storage= 20,451 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 120.3 min ( 1,020.4 - 900.1 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.25 cfs @ 13.04 hrs HW=170.32' (Free Discharge) (Exfiltration Controls 0.25 cfs) 3=Exfiltration Max=4.38 cfs @ 13.04 hrs HW=170.32' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 4.38 cfs @ 5.6 fps) 1=Culvert Max=0.00 cfs @ 0.00 hrs HW=169.50' TW=169.00' (Dynamic Tailwater) Secondary OutFlow ( Controls 0.00 cfs) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=9.29 cfs @ 12.14 hrs, Volume=0.763 af Outflow=0.00 cfs @ 0.00 hrs, Volume=0.000 af, Atten= 100%, Lag= 0.0 min Primary=0.00 cfs @ 0.00 hrs, Volume=0.000 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 2 yr n andover Rainfall=3.20" brooks school art center post cd Page 7 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 170.03' @ 24.55 hrs Surf.Area= 47,032 sf Storage= 33,211 cf Plug-Flow detention time= (not calculated: initial storage excedes outflow) Center-of-Mass det. time= (not calculated: no outflow) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=0.00 cfs @ 0.00 hrs HW=169.00' TW=169.50' (Dynamic Tailwater) Primary OutFlow ( Controls 0.00 cfs) 1=Broad-Crested Rectangular Weir Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school art center post cd Page 8 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.770 ac Runoff Depth=2.05" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=23.43 cfs 2.176 af Runoff Area=7.186 ac Runoff Depth=2.54" Subcatchment 2S: Trib Area to wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=18.95 cfs 1.523 af Runoff Area=25.120 ac Runoff Depth=1.38" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=25.67 cfs 2.897 af Runoff Area=39.204 ac Runoff Depth=2.21" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=69.43 cfs 7.206 af Inflow=47.16 cfs 5.073 af Reach 2R: (new Reach) Outflow=47.16 cfs 5.073 af Inflow=4.97 cfs 5.596 af Reach DP1: outlet pipe Outflow=4.97 cfs 5.596 af Inflow=69.43 cfs 7.206 af Reach DP2: north wetlands Outflow=69.43 cfs 7.206 af Peak Elev=171.15' Storage=68,810 cf Inflow=47.16 cfs 5.588 af Pond 1P: Detention area Discarded=0.46 cfs 0.336 af Primary=4.97 cfs 5.596 af Secondary=12.09 cfs 0.841 af Outflow=17.52 cfs 6.773 af Peak Elev=170.98' Storage=85,524 cf Inflow=18.95 cfs 2.363 af Pond 2P: Wetland Area Outflow=1.18 cfs 0.515 af Total Runoff Area = 84.280 ac Runoff Volume = 13.802 af Average Runoff Depth = 1.97" Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school art center post cd Page 9 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=23.43 cfs @ 12.20 hrs, Volume=2.176 af, Depth=2.05" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Area (ac)CNDescription 2.83898Paved parking & roofs 4.46161>75% Grass cover, Good, HSG B 3.68974>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.56255Woods, Good, HSG B 0.12770Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.77072Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to wetlands Runoff=18.95 cfs @ 12.13 hrs, Volume=1.523 af, Depth=2.54" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Area (ac)CNDescription 1.52198Paved parking & roofs 0.17661>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.07355Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.18678Weighted Average Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school art center post cd Page 10 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=25.67 cfs @ 12.29 hrs, Volume=2.897 af, Depth=1.38" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=69.43 cfs @ 12.27 hrs, Volume=7.206 af, Depth=2.21" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school art center post cd Page 11 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.41098Paved parking & roofs 12.79961>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 39.20474Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =37.890 ac, Inflow Depth = 1.61" for 10 yr n andover event Inflow=47.16 cfs @ 12.24 hrs, Volume=5.073 af Outflow=47.16 cfs @ 12.29 hrs, Volume=5.073 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=4.97 cfs @ 12.78 hrs, Volume=5.596 af Outflow=4.97 cfs @ 12.83 hrs, Volume=5.596 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =39.204 ac, Inflow Depth = 2.21" for 10 yr n andover event Inflow=69.43 cfs @ 12.27 hrs, Volume=7.206 af Outflow=69.43 cfs @ 12.32 hrs, Volume=7.206 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school art center post cd Page 12 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=47.16 cfs @ 12.29 hrs, Volume=5.588 af Outflow=17.52 cfs @ 12.78 hrs, Volume=6.773 af, Atten= 63%, Lag= 29.0 min Discarded=0.46 cfs @ 12.78 hrs, Volume=0.336 af Primary=4.97 cfs @ 12.78 hrs, Volume=5.596 af Secondary=12.09 cfs @ 12.78 hrs, Volume=0.841 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 171.15' @ 12.78 hrs Surf.Area= 73,392 sf Storage= 68,810 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 174.8 min ( 1,067.6 - 892.8 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.46 cfs @ 12.78 hrs HW=171.15' (Free Discharge) (Exfiltration Controls 0.46 cfs) 3=Exfiltration Max=4.97 cfs @ 12.78 hrs HW=171.15' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 4.97 cfs @ 6.3 fps) 1=Culvert Max=12.04 cfs @ 12.78 hrs HW=171.15' TW=170.28' (Dynamic Tailwater) Secondary OutFlow (Weir Controls 12.04 cfs @ 1.4 fps) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=18.95 cfs @ 12.13 hrs, Volume=2.363 af Outflow=1.18 cfs @ 16.37 hrs, Volume=0.515 af, Atten= 94%, Lag= 254.1 min Primary=1.18 cfs @ 16.37 hrs, Volume=0.515 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 10 yr n andover Rainfall=4.80" brooks school art center post cd Page 13 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 170.98' @ 15.36 hrs Surf.Area= 62,997 sf Storage= 85,524 cf Plug-Flow detention time= 398.7 min calculated for 0.515 af (22% of inflow) Center-of-Mass det. time= 286.6 min ( 1,102.5 - 815.9 ) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=1.23 cfs @ 16.37 hrs HW=170.97' TW=170.94' (Dynamic Tailwater) Primary OutFlow (Weir Controls 1.23 cfs @ 0.5 fps) 1=Broad-Crested Rectangular Weir Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school art center post cd Page 14 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.770 ac Runoff Depth=2.99" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=34.73 cfs 3.185 af Runoff Area=7.186 ac Runoff Depth=3.58" Subcatchment 2S: Trib Area to wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=26.65 cfs 2.143 af Runoff Area=25.120 ac Runoff Depth=2.18" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=42.37 cfs 4.556 af Runoff Area=39.204 ac Runoff Depth=3.18" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=101.11 cfs 10.405 af Inflow=74.45 cfs 7.741 af Reach 2R: (new Reach) Outflow=74.45 cfs 7.741 af Inflow=5.34 cfs 7.806 af Reach DP1: outlet pipe Outflow=5.34 cfs 7.806 af Inflow=101.11 cfs 10.405 af Reach DP2: north wetlands Outflow=101.11 cfs 10.405 af Peak Elev=171.74' Storage=115,707 cf Inflow=74.45 cfs 17.998 af Pond 1P: Detention area Discarded=0.54 cfs 0.655 af Primary=5.34 cfs 7.821 af Secondary=37.32 cfs 9.964 af Outflow=42.97 cfs 18.441 af Peak Elev=171.76' Storage=139,179 cf Inflow=43.19 cfs 12.107 af Pond 2P: Wetland Area Outflow=36.93 cfs 10.256 af Total Runoff Area = 84.280 ac Runoff Volume = 20.289 af Average Runoff Depth = 2.89" Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school art center post cd Page 15 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=34.73 cfs @ 12.20 hrs, Volume=3.185 af, Depth=2.99" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Area (ac)CNDescription 2.83898Paved parking & roofs 4.46161>75% Grass cover, Good, HSG B 3.68974>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.56255Woods, Good, HSG B 0.12770Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.77072Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to wetlands Runoff=26.65 cfs @ 12.13 hrs, Volume=2.143 af, Depth=3.58" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Area (ac)CNDescription 1.52198Paved parking & roofs 0.17661>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.07355Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.18678Weighted Average Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school art center post cd Page 16 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=42.37 cfs @ 12.28 hrs, Volume=4.556 af, Depth=2.18" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=101.11 cfs @ 12.26 hrs, Volume=10.405 af, Depth=3.18" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school art center post cd Page 17 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.41098Paved parking & roofs 12.79961>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 39.20474Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =37.890 ac, Inflow Depth = 2.45" for 25 yr n andover event Inflow=74.45 cfs @ 12.24 hrs, Volume=7.741 af Outflow=74.45 cfs @ 12.29 hrs, Volume=7.741 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=5.34 cfs @ 16.00 hrs, Volume=7.806 af Outflow=5.34 cfs @ 16.05 hrs, Volume=7.806 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =39.204 ac, Inflow Depth = 3.18" for 25 yr n andover event Inflow=101.11 cfs @ 12.26 hrs, Volume=10.405 af Outflow=101.11 cfs @ 12.31 hrs, Volume=10.405 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school art center post cd Page 18 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=74.45 cfs @ 12.29 hrs, Volume=17.998 af Outflow=42.97 cfs @ 12.61 hrs, Volume=18.441 af, Atten= 42%, Lag= 19.5 min Discarded=0.54 cfs @ 16.00 hrs, Volume=0.655 af Primary=5.34 cfs @ 16.00 hrs, Volume=7.821 af Secondary=37.32 cfs @ 12.61 hrs, Volume=9.964 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 171.74' @ 16.00 hrs Surf.Area= 86,892 sf Storage= 115,707 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 99.1 min ( 1,076.8 - 977.7 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.54 cfs @ 16.00 hrs HW=171.74' (Free Discharge) (Exfiltration Controls 0.54 cfs) 3=Exfiltration Max=5.34 cfs @ 16.00 hrs HW=171.74' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 5.34 cfs @ 6.8 fps) 1=Culvert Max=37.18 cfs @ 12.61 hrs HW=171.44' TW=170.83' (Dynamic Tailwater) Secondary OutFlow (Weir Controls 37.18 cfs @ 2.0 fps) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=43.19 cfs @ 12.57 hrs, Volume=12.107 af Outflow=36.93 cfs @ 15.92 hrs, Volume=10.256 af, Atten= 14%, Lag= 200.8 min Primary=36.93 cfs @ 15.92 hrs, Volume=10.256 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 25 yr n andover Rainfall=6.00" brooks school art center post cd Page 19 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 171.76' @ 15.90 hrs Surf.Area= 75,623 sf Storage= 139,179 cf Plug-Flow detention time= 161.0 min calculated for 10.256 af (85% of inflow) Center-of-Mass det. time= 106.7 min ( 1,067.2 - 960.5 ) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=34.61 cfs @ 15.92 hrs HW=171.73' TW=171.64' (Dynamic Tailwater) Primary OutFlow (Weir Controls 34.61 cfs @ 1.2 fps) 1=Broad-Crested Rectangular Weir Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school art center post cd Page 20 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Time span=0.00-30.00 hrs, dt=0.05 hrs, 601 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Sim-Route method - Pond routing by Sim-Route method Runoff Area=12.770 ac Runoff Depth=5.22" Subcatchment 1S: Trib Area to Detention area Flow Length=525' Tc=13.7 min CN=72 Runoff=60.73 cfs 5.560 af Runoff Area=7.186 ac Runoff Depth=5.95" Subcatchment 2S: Trib Area to wetlands Flow Length=270' Tc=9.0 min CN=78 Runoff=43.76 cfs 3.562 af Runoff Area=25.120 ac Runoff Depth=4.15" Subcatchment 3S: NE Side Great Pond Rd Flow Length=1,170' Tc=18.8 min CN=63 Runoff=83.75 cfs 8.679 af Runoff Area=39.204 ac Runoff Depth=5.47" Subcatchment 4S: Trib Area to north wetlands Flow Length=622' Tc=18.7 min CN=74 Runoff=173.22 cfs 17.856 af Inflow=139.90 cfs 14.239 af Reach 2R: (new Reach) Outflow=139.90 cfs 14.239 af Inflow=6.27 cfs 9.894 af Reach DP1: outlet pipe Outflow=6.27 cfs 9.894 af Inflow=173.22 cfs 17.856 af Reach DP2: north wetlands Outflow=173.22 cfs 17.856 af Peak Elev=173.37' Storage=281,930 cf Inflow=213.04 cfs 112.488 af Pond 1P: Detention area Discarded=0.71 cfs 1.009 af Primary=6.27 cfs 9.917 af Secondary=198.91 cfs 98.519 af Outflow=205.87 cfs 109.445 af Peak Elev=173.42' Storage=288,336 cf Inflow=200.15 cfs 101.826 af Pond 2P: Wetland Area Outflow=207.25 cfs 98.249 af Total Runoff Area = 84.280 ac Runoff Volume = 35.657 af Average Runoff Depth = 5.08" Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school art center post cd Page 21 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Subcatchment 1S: Trib Area to Detention area Runoff=60.73 cfs @ 12.19 hrs, Volume=5.560 af, Depth=5.22" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Area (ac)CNDescription 2.83898Paved parking & roofs 4.46161>75% Grass cover, Good, HSG B 3.68974>75% Grass cover, Good, HSG C 0.02180>75% Grass cover, Good, HSG D 1.56255Woods, Good, HSG B 0.12770Woods, Good, HSG C 0.07277Woods, Good, HSG D 12.77072Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 8.9500.01700.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.63350.04801.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.21400.07902.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 13.7525Total Subcatchment 2S: Trib Area to wetlands Runoff=43.76 cfs @ 12.13 hrs, Volume=3.562 af, Depth=5.95" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Area (ac)CNDescription 1.52198Paved parking & roofs 0.17661>75% Grass cover, Good, HSG B 2.74574>75% Grass cover, Good, HSG C 0.33980>75% Grass cover, Good, HSG D 0.07355Woods, Good, HSG B 0.79670Woods, Good, HSG C 0.36877Woods, Good, HSG D 1.16873Brush, Good, HSG D 7.18678Weighted Average Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school art center post cd Page 22 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.4500.06000.2 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.31600.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3600.06703.9 Shallow Concentrated Flow, Grassed Waterway Kv= 15.0 fps 9.0270Total Subcatchment 3S: NE Side Great Pond Rd Runoff=83.75 cfs @ 12.27 hrs, Volume=8.679 af, Depth=4.15" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Area (ac)CNDescription 0.75098Paved parking & roofs 14.24055Woods, Good, HSG B 0.75061>75% Grass cover, Good, HSG B 4.96070Woods, Good, HSG C 3.23074>75% Grass cover, Good, HSG C 0.47077Woods, Good, HSG D 0.72080>75% Grass cover, Good, HSG D 25.12063Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 5.0500.20000.2 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 3.54700.20002.2Shallow Concentrated Flow, Woodland Kv= 5.0 fps 1.91500.07001.3Shallow Concentrated Flow, Woodland Kv= 5.0 fps 8.45000.02001.0Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.81,170Total Subcatchment 4S: Trib Area to north wetlands Runoff=173.22 cfs @ 12.26 hrs, Volume=17.856 af, Depth=5.47" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school art center post cd Page 23 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Area (ac)CNDescription 8.41098Paved parking & roofs 12.79961>75% Grass cover, Good, HSG B 9.32074>75% Grass cover, Good, HSG C 5.35170Woods, Good, HSG C 3.32473Brush, Good, HSG D 39.20474Weighted Average TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 11.0500.01000.1 Sheet Flow, Grass: Dense n= 0.240 P2= 3.10" 3.02800.05001.6 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.3500.20003.1 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 4.22000.01300.8 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 0.2420.18003.0 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 18.7622Total Reach 2R: (new Reach) Inflow Area =37.890 ac, Inflow Depth = 4.51" for 100 yr n andover event Inflow=139.90 cfs @ 12.23 hrs, Volume=14.239 af Outflow=139.90 cfs @ 12.28 hrs, Volume=14.239 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP1: outlet pipe Inflow=6.27 cfs @ 17.20 hrs, Volume=9.894 af Outflow=6.27 cfs @ 17.25 hrs, Volume=9.894 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Reach DP2: north wetlands Inflow Area =39.204 ac, Inflow Depth = 5.47" for 100 yr n andover event Inflow=173.22 cfs @ 12.26 hrs, Volume=17.856 af Outflow=173.22 cfs @ 12.31 hrs, Volume=17.856 af, Atten= 0%, Lag= 3.0 min Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school art center post cd Page 24 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Pond 1P: Detention area Inflow=213.04 cfs @ 16.92 hrs, Volume=112.488 af Outflow=205.87 cfs @ 17.02 hrs, Volume=109.445 af, Atten= 3%, Lag= 6.2 min Discarded=0.71 cfs @ 17.20 hrs, Volume=1.009 af Primary=6.27 cfs @ 17.20 hrs, Volume=9.917 af Secondary=198.91 cfs @ 17.02 hrs, Volume=98.519 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 173.37' @ 17.20 hrs Surf.Area= 114,184 sf Storage= 281,930 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 27.7 min ( 1,206.8 - 1,179.2 ) VolumeInvertAvail.StorageStorage Description #1169.50'355,960 cfCustom Stage Data (Prismatic) Listed below (Recalc) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.5014,69000 170.0025,52010,05310,053 171.0069,82047,67057,723 172.0092,89081,355139,078 173.00109,125101,008240,085 174.00122,625115,875355,960 DeviceRoutingInvertOutlet Devices #1Primary166.60' 12.0" x 243.0' long Culvert CPP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 166.42' S= 0.0007 '/' Cc= 0.900 n= 0.010 #2Secondary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 #3Discarded0.00'0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.71 cfs @ 17.20 hrs HW=173.36' (Free Discharge) (Exfiltration Controls 0.71 cfs) 3=Exfiltration Max=6.26 cfs @ 17.20 hrs HW=173.36' TW=0.00' (Dynamic Tailwater) Primary OutFlow (Barrel Controls 6.26 cfs @ 8.0 fps) 1=Culvert Max=184.28 cfs @ 17.02 hrs HW=173.26' TW=172.92' (Dynamic Tailwater) Secondary OutFlow (Weir Controls 184.28 cfs @ 2.2 fps) 2=Broad-Crested Rectangular Weir Pond 2P: Wetland Area Inflow=200.15 cfs @ 17.02 hrs, Volume=101.826 af Outflow=207.25 cfs @ 17.32 hrs, Volume=98.249 af, Atten= 0%, Lag= 17.8 min Primary=207.25 cfs @ 17.32 hrs, Volume=98.249 af Routing by Sim-Route method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type III 24-hr 100 yr n andover Rainfall=8.60" brooks school art center post cd Page 25 Prepared by Whitman & Bingham Associates HydroCAD® 7.10 s/n 000655 © 2005 HydroCAD Software Solutions LLC 1/16/2017 Peak Elev= 173.42' @ 17.30 hrs Surf.Area= 104,568 sf Storage= 288,336 cf Plug-Flow detention time= 55.0 min calculated for 98.249 af (96% of inflow) Center-of-Mass det. time= 34.9 min ( 1,228.1 - 1,193.2 ) VolumeInvertAvail.StorageStorage Description #1169.00'352,490 cf Listed below (Recalc) Custom Stage Data (Prismatic) ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 169.0016,96000 170.0046,50031,73031,730 171.0063,29054,89586,625 172.0079,59071,440158,065 173.0097,10088,345246,410 174.00115,060106,080352,490 DeviceRoutingInvertOutlet Devices #1Primary170.90' 35.0' long x 100.0' 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) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Max=197.25 cfs @ 17.32 hrs HW=173.31' TW=172.91' (Dynamic Tailwater) Primary OutFlow (Weir Controls 197.25 cfs @ 2.3 fps) 1=Broad-Crested Rectangular Weir 3.0 SOIL MAP Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis FIGURE 1 PRE-DEVELOPMENT WATERSHED DELINEATION Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis FIGURE 2 POST-DEVELOPMENT WATERSHED DELINEATION Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis 1 “Urban Hydrology for Small Watersheds (Technical Release Number 55); Engineering Division, United StatesDept. of Agriculture, Soil Conservation Service (Jan. 1975). 2 “National Engineering Handbook Section 4-Hydrology”; United States Dept. of Agriculture, Soil Conservation Service (March 1985) 3 “Atlas of Precipitation Extremes for the Northeastern United States and Southeastern Canada”, Daniel S. Wilks & Richard P. Cember, Northeast Regional Climate Center Research Series, Publication No. RR 93-5, September 1993. 4 “HydroCAD” Drainage software developed by Hydrocad Software Solutions, LLC,P.O. Box 477, Chocorua, NH; Tel. (603)323- 8666Copyrights 2005. (version 7.10) Whitman & Bingham Associates, LLCBrooks Center for the Arts Registered Engineers & LandSurveyors StormwaterAnalysis