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Stormwater Management Report
STORMWATER MANAGEMENT REPORT Prepared for: 1454 State Route 9, LLC Site Modifications State Route 9 Tax Map # 288.12-1-21 Town of Queensbury Warren County, New York Prepared by: Hutchins Engineering 169 Haviland Road Queensbury, NY 12804 April 15, 2018 TABLE OF CONTENTS 1.0 PROJECT DESCRIPTION .............................................................................. 1 2.0 EXISTING SITE CONDITIONS ........................................................................ 1 3.0 PROPOSED DEVELOPMENT ......................................................................... 2 4.0 PROPOSED STORMWATER MANAGEMENT ................................................... 2 5.0 TOWN OF QUEENSBURY REQUIREMENTS .......................................................... 3 6.0 CONSTRUCTION PHASE EROSION PRACTICES ................................................... 3 7.0 TEMPORARY EROSION & SEDIMENT CONTROL MEASURES ................................. 3 8.0 CONTROL OF LITTER, CONSTRUCTION DEBRIS & CONSTRUCTION CHEMICALS .... 4 9.0 SEQUENCE OF CONSTRUCTION ........................................................................ 4 10.0 MAINTENANCE OF TEMPORARY EROSION & SEDIMENT CONTROL DEVICES 4 11.0 OPERATION & MAINTENANCE PLAN ................................................................... 4 12.0 PERMANENT EROSION CONTROL ...................................................................... 4 ATTACHMENTS a Location Map ■ Soils Map • Subcatchment Map— Existing Model 4 HydroCAD — Existing ■ Subcatchment Map — Proposed Model HydroCAD — Proposed HYDROCAD Existing & Proposed Conditions: Type-ll 24 hr Rainfall = 4.8" (50-year) I 1.0 PROJECT DESCRIPTION The project consists of a removal of an existing 10,067-SF footprint building which includes a restaurant and part of a hotel, and subsequent construction of a new 12,600-SF footprint retail building on the site of the existing Clarion Hotel at 1454 State Route 9. Parking in the area of work will be reconfigured and conditions in the unaffected areas of the site will remain as existing. Also associated with the project are construction, landscaping, and stormwater management facilities. Project disturbance totals 0.95 acres. The project site is located at 1454 State Route 9 in the Town of Queensbury, Warren County, New York. 2.0 EXISTING SITE CONDITIONS Presently, the project site consists of a Clarion Hotel and a restaurant building with a combined 159 parking spaces. Site soils over the site are mapped as Oakville Loamy Fine Sand, HSG-A. A copy of the USDA soils map is included in the appendix of this report. Site slopes over the majority of the site range from 1 to 4%. Runoff from the proposed new building is to be captured and infiltrated through precast concrete drywells. There is presently some runoff flowing onto adjacent properties to the north and south. Proposed stormwater work will provide a vast improvement to this condition. Work proposed for this project is located at the westerly portion of the site in the area of NYS Route 9. Existing Conditions Summary Total Project Site Area: 3.37 Acres Buildings Coverage: 36,714 SF Drives, Walks & Parking. 61,766 SF Total Impervious: 98,480 SF Drainage Design Points The site is broken into four drainage design points: 1 L— Runoff to Southwest 2L— Runoff to North 3L— Runoff to south 4L —Total Site Runoff Design Storm Events 50-year, 24hr, Type-ll distribution, 4.8" Existing Conditions Calculated Stormwater Runoff to Southwest— 1 L 50-year design storm (4.8") 1.80 CFS 0.017 acre-feet Existing Conditions Calculated Stormwater Runoff to North—2L 50-year design storm (4.8") 1.99 CFS 0.083 acre-feet Existing Conditions Calculated Stormwater Runoff to South —3L 50-year design storm (4.8") 3.22 CFS 0.164 acre-feet Existinq Conditions Calculated Stormwater Runoff from Site—4L 50-year design storm (4.8") 6.20 CFS 0.264 acre-feet 3.0 PROPOSED DEVELOPMENT Proposed Conditions Summary Total Project Site Area: 3.37 Acres Building Coverage: 39,297 SF Walks, Drives & Parking Areas: 62,489 SF Total Impervious: 101,786 SF Project Disturbance: 0.95 Acres 4.0 PROPOSED STORMWATER MANAGEMENT As this is a commercial project with soil disturbances not exceeding one acre, NYSDEC SPDES requirements for stormwater discharges from construction activities do not apply to the project. The Town of Queensbury requires that commercial projects implement stormwater management practices designed to manage the 50-year design storm event. Runoff from the new building roof will be captured through a roof drainage system and infiltrated through a system of two precast concrete drywells to be located just north of the proposed building. Four new deep sump catch basins discharging to three new precast concrete drywells will serve the reconfigured parking areas on the west and south parking and sidewalk areas. Runoff from the rear of the building will be captured and infiltrated in a 3-ft wide stone-filled eave trench. Runoff from the easterly remainder of the site, which is not involved in the project, will maintain existing drainage patterns. An infiltration rate of 20 inches per hour is utilized for the infiltration facilities. Runoff calculations have been prepared using SCS TR-20 methodology and HydroCAD analysis software for the 50- year Type-ll simulated rainfall distributions. Total area of stormwater model is 1.128 acres as portions of the property which are not to be disturbed are part of the model area. Criteria utilized in the analysis are summarized as follows: Design Storm Events 50-year, 24hr, Type-II distribution, 4.8" Proposed Conditions Calculated Stormwater Runoff to Southwest- 1 L 50-year design storm (4.8") 1.65 CFS 0.015 acre-feet Proposed Conditions Calculated Stormwater Runoff to North_-2L 50-year design storm (4.8") 0.39 CFS 0.016 acre-feet Proposed Conditions Calculated Stormwater Runoff to South-3L 50-year design storm (4.8") 0.0 CFS 0.0 acre-feet Proposed Conditions Calculated Stormwater Runoff from Site-4L 50-year design storm (4.8") 1.88 CFS 0.032 acre-feet The developed site has been modeled as a series of subcatchments (drainage areas) and ponds, as shown on the HydroCAD drainage diagram. Full results of stormwater runoff computations are attached to this report. 2 5.0 TOWN OF QUEENSBURY REQUIREMENTS The Town of Queensbury requires that for commercial projects, the 50-year design storm event be evaluated. Existing 50-year peak storm volume: 0.264 AF Developed 50-year peak storm volume: 0.032 AF Existing 50-year peak storm discharge: 6.20 CFS Developed 50-year peak storm discharge: 1.88 CFS The 50-year storm calculations show that the Town's requirements for commercial projects are met. 6.0 CONSTRUCTION PHASE EROSION PRACTICES Practices to be implemented during construction for erosion and sediment control include silt fencing and temporary sediment traps in various portions of the total disturbed area. Silt fencing will be placed across slopes (on the contour) in all areas downgrade of disturbed areas. Temporary sediment traps will be utilized in areas where construction phase runoff concentrates. 7.0 TEMPORARY EROSION & SEDIMENT CONTROL MEASURES Erosion and sediment control measures will be incorporated into the construction of the project. These practices will comply with the New York State Department of Environmental Conservation publication entitled"New York Guidelines for Urban and Sediment Control"(the blue book). Separate erosion and sediment controls will be installed for each phase of construction. The following temporary erosion and sediment control devices are to be utilized: 1. Sediment Control Fence Silt Fence shall be used to control erosion from sheet flow on slopes not to exceed 1-on-3. Concentrated flows shall not be directed toward the silt fence. The silt fence must be installed parallel to the contour lines to eliminate drainage along the fence. 2. Drywell Inlet Protection Fabric inlet protection is to be installed immediately after drywell and grate installation and is to be maintained until final surrounding vegetation areas are established with dense vegetation. 3. Temporary Diversion Swales Temporary diversion swales shall be constructed either to divert clean stormwater runoff from newly graded areas or to direct sediment laden runoff to a sediment trapping device. 4. Dust Control Measures for dust control during construction shall be implemented as needed. Daily water sprays will be used during dry conditions. In addition to water sprays, temporary mulching, temporary seeding and covering stockpiles with tarps shall be implemented when necessary. 5. Erosion Control Blanket Fabricated straw or biodegradable mesh blankets shall be utilized to protect and temporarily stabilize slopes of 1:3 or greater and shall be applied to graded, topsoiled, and seeded slopes. Blankets will be attached with staples or stakes in accordance with manufacturer's 3 recommendations. Blankets on cut slopes and vegetated ditchlines will be maintained in place permanently and allowed to biodegrade. 8.0 CONTROL OF LITTER, CONSTRUCTION DEBRIS & CONSTRUCTION CHEMICALS During the course of construction, the site shall be kept clear of debris and litter which could be transported by water or wind. This material shall be picked up daily and shall be stored in waste debris containers where it will be securely held. All petroleum products or other waste contaminants which are water soluble, or could be dispersed and transported by stormwater, shall be stored in covered containers and shall be regularly removed from the site and properly and legally disposed of. All petroleum or other hazardous materials shall be stored and handled in conformance with NYSDEC spill prevention and containment requirements. 9.0 SEQUENCE OF CONSTRUCTION Prior to the start of construction, the contractor shall install the sediment control fence along the low side of each area to be disturbed in order to contain runoff from the construction site. Concurrently, the stabilized construction entrance is to be installed. Following the completion of all planting and the establishment of all grass areas, any collected sediment and sediment control fencing shall be removed. Any debris from the perimeter of the site shall be removed and dispose of all waste material shall be disposed of in a legal manner. 10.0 MAINTENANCE OF TEMPORARY EROSION & SEDIMENT CONTROL DEVICES The contractor shall inspect the sediment control fence weekly and after every rain event and remove trapped sediment and maintain the devices such that they are in good working order. 11.0 OPERATION & MAINTENANCE PLAN The parcel owner is to provide the maintenance needed in order to ensure continuous and effective operation of the stormwater control practices. Sediment removal should be performed annually or semi-annually in the vegetated pretreatment/lawn areas and drywells. Any eroded areas shall be immediately repaired, retopsoiled, revegetated and covered with erosion control blankets. 12.0 PERMANENT EROSION CONTROL All pervious areas shall be graded, topsoil installed and seeded or planted as soon as practical, but in no case shall finish graded soils be exposed for more than seven days. Seeded areas on slopes over 1:3 shall be stabilized with erosion control blankets as specified on the plans. 4 ATTACHMENTS ■ Location Map ■ Soils Map • Subcatchment Map— Existing Model HydroCAD— Existing • Subcatchment Map— Proposed Model HydroCAD— Proposed HYDROCAD Existing & Proposed Conditions: Type-II 24 hr Rainfall = 4.8" (50-year) 5 � CL L) '90.40 111,44 ID LO CL hyarth`ley ED ()Oc k3cy, EJ ID to ID baa 13y1 rrt B Soil Map—Warren County,New York 3: H (1454 State Route 9,LLC) S w a 2" axaeo 035 z7 B7�a1 urrm aww acv mseec 43°22 2'N 43.27rN r e ,T f4.i1n sill ,I 43.21-WN f I � F� 43°21'SM1•N E8^riBD GDm GOMBd ODW able= B[65e0 SSK40 'R9q arer3 am 3 ; H y Map Sole:1:11800 r pHnted on A landsmpe(11"x 8,61 diet N n a:. � IA _ r� d Y] 100 ;9: 30U MOP Mijedim:web Mermbor fomamordlrt7tes:WGW Edge tts:UTM Zone 18N WGS94 USDA Natural Resources Web Soil Survey 4/16/2016 Conservation Service National Cooperative Soil Survey Page 1 of 3 f Soil Map—Warren County,New York 1454 State Route 9,LLC Map Unit Legend k EMap Unit Symbol Map Unit Name Acres In AOI Percent of AOI OaA Oakville loamy fine sand,0 to 5.2 30.0% 3 percent slopes OaB Oakville loamy fine sand,3 to 12.1 70.0% 8 percent slopes J Totals for Area of Interest 17.3 100.0% I USDA Natural Resources Web Soil Survey 4/16/2018 Conservation Service National Cooperative Soil Survey Page 3 of 3 Existing Conditions N L U- 4r a 00 U y O 0 Lo 6 Lo ten^ as i t I \ 1 r of � mm CO uj .- 4 rr^^ p 1 1 � � D Sry4.l, 4 f'l, �S 2S 35 SW BUILD NG & PKG NW BUILDI G & PKG SOUTH ENTRAL ROOF & PKG CB 3P EXIST CB 1 2L NORTH R NOFF 11V 1 8'x8' D RYW E L 41 1L K SW RUNOFF OU RUNOFF 4L SITE RUNOFF Subcat Reach on Link Drainage Diagram for EXISTING CONDITIONS-JOB AREA Prepared by Hutchins Engineering, Printed 4/16/2018 HydroCAD®9.10 s/n 02373 ©2010 HydroCAD Software Solutions LLC EXISTING CONDITIONS-JOB AREA Type 11 24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCADO 9.10 s/n 02373 0 2010 H droCAD Software Solutions LLC Page 2 Summary for Subcatchment 1S: SW BUILDING & PKG Runoff = 1.95 cfs @ 11.94 hrs, Volume= 0.095 af, Depth= 4.00" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type II 24-hr 50-YR Rainfall=4.80" Area (sf) CN Description 1,572 98 BLDG ROOFS 9,751 98 DRIVES & ROADWAYS 1,051 39 >75% Grass cover, Good, HSG A 12,374 93 Weighted Average 1,051 8.49% Pervious Area 11,323 91.51% Impervious Area Tc Length Slope Velocity Capacity Description (min) feet ft/ft ft/sec cfs 2.3 300 0.0500 2.14 Sheet Flow, Smooth surfaces n= 0.011 P2= 2.40" 1.1 300 0.0500 4.54 Shallow Concentrated Flow, Paved Kv= 20.3 fps 3.4 600 Total Summary for Subcatchment 2S: NW BUILDING & PKG Runoff = 1.99 cfs @ 11.89 hrs, Volume= 0.083 af, Depth= 2.81" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type II 24-hr 50-YR Rainfall=4.80" Area (sf) CN Description 4,109 98 ROOF 4,481 39 >75% Grass cover, Good, HSG A 6.770 98 Paved parking, HSG A 15,360 81 Weighted Average 4,481 29.17% Pervious Area 10,879 70.83% Impervious Area Summary for Subcatchment 3S: SOUTH CENTRAL ROOFS & PKG Runoff = 3.22 cfs @ 11.95 hrs, Volume= 0.164 af, Depth= 4.00" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type 11 24-hr 50-YR Rainfall=4.80" EXISTING CONDITIONS-JOB AREA Type 1124-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCAD®9.10 s/n 02373 ©2010 H droCAD Software Solutions LLC Page 3 Area sf CN Description 2,766 98 Roofs, HSG A 16,728 98 Paved parking, HSG A _ 1,923 39 >75% Grass cover, Good. HSG A _ 21,417 93 Weighted Average 1,923 8.98% Pervious Area 19,494 91.02% Impervious Area Tc Length Slope Velocity Capacity Description __(min)_ _(feet) (ft/ft) (ft/sec) (cfs) _ 5.0 Direct Entry, Summary for Pond 3P: EXIST CB-E1 Inflow Area = 0.284 ac, 91.51% Impervious, Inflow Depth = 4.00" for 50-YR event Inflow = 1.95 cfs @ 11.94 hrs, Volume= 0.095 of Outflow = 1.95 cfs @ 11.94 hrs, Volume= 0.095 af, Atten= 0%, Lag= 0.0 min Primary = 1.95 cfs @ 11.94 hrs, Volume= 0.095 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 515.77' @ 11.94 hrs Device Routina Invert Outlet Devices #1 Primary 515.00' 12.0" Round Culvert L= 20.0' CPP, square edge headwall, Ke= 0.500 Inlet/ Outlet Invert= 515.00'/ 514.50' S= 0.0250 T Cc= 0.900 n= 0.009 Corrugated PE, smooth interior Primary OutFlow Max=1.87 cfs @ 11.94 hrs HW=515.75' (Free Discharge) t1»Culvert (Inlet Controls 1.87 cfs @ 2.95 fps) Summary for Pond DW1: 8'x8' DRYWELL Inflow Area = 0.284 ac, 91.51% Impervious, Inflow Depth = 4.00" for 50-YR event Inflow = 1.95 cfs @ 11.94 hrs, Volume= 0.095 of Outflow = 2.03 cfs @ 11.96 hrs, Volume= 0.095 af, Atten= 0%, Lag= 1.7 min Discarded = 0.24 cfs @ 11.96 hrs, Volume= 0.077 of Primary = 1.80 cfs @ 11.96 hrs, Volume= 0.017 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 516.76' @ 11.96 hrs Surf.Area= 512 sf Storage= 999 cf Plug-Flow detention time= 28.4 min calculated for 0.095 of(100% of inflow) Center-of-Mass det. time= 28.3 min ( 802.0 - 773.7 ) Volume Invert Avail.Storaae Storage Description #1 509.00' 1,173 cf 10.00'D x 10.00'H STONE ENVELOPE Z=1.0 3,403 cf Overall - 472 cf Embedded = 2,931 cf x 40.0% Voids #2 510.00' 402 cf 8.00'D x 8.00'H DRYWELL BARREL Inside#1 472 cf Overall -4.0" Wall Thickness =402 cf EXISTING CONDITIONS-JOB AREA Type 11 24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCADO 9.10 s/n 02373 ©2010 H droCAD Software Solutions LLC Page 4 1,575 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 509.00' 20.000 in/hr Exfiltration over Surface area #2 Primary 516.00' 12.0" Round OUTLET PIPE L= 20.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 516.00'/515.70' S= 0.0150 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior Qiscarded OutFlow Max=0.23 cfs @ 11.96 hrs HW=516.70' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.23 cfs) j PrimaryOutFlow Max=1.61 cfs @ 11.96 hrs HW=516.70' (Free Discharge) t-2=OUTLET PIPE (Barrel Controls 1.61 cfs @ 3.82 fps) Summary for Link 1 L: SW RUNOFF Inflow Area = 0.284 ac, 91.51% Impervious, Inflow Depth = 0.74" for 50-YR event Inflow = 1.80 cfs @ 11.96 hrs, Volume= 0.017 of Primary = 1.80 cfs @ 11.96 hrs, Volume= 0.017 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Summary for Link 2L: NORTH RUNOFF Inflow Area = 0.353 ac, 70.83% Impervious, Inflow Depth = 2.81" for 50-YR event Inflow = 1.99 cfs @ 11.89 hrs, Volume= 0.083 of Primary = 1.99 cfs @ 11.89 hrs, Volume= 0.083 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Summary for Link 3L: SOUTH RUNOFF Inflow Area = 0.492 ac, 91.02% Impervious, Inflow Depth = 4.00" for 50-YR event Inflow = 3.22 cfs @ 11.95 hrs, Volume= 0.164 of Primary = 3.22 cfs @ 11.95 hrs, Volume= 0.164 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Summary for Link 4L: SITE RUNOFF Inflow Area = 1.128 ac, 84.83% Impervious, Inflow Depth = 2.81" for 50-YR event Inflow = 6.20 cfs @ 11.95 hrs, Volume= 0.264 of Primary = 6.20 cfs @ 11.95 hrs, Volume= 0.264 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs p N t Li co 0 Ln En r r f i m 1 - - - - - - - - - c LU � 1 = w W ciSR W y - � ~ • 1\ Lu 0 ! I IS Ali S'� -� Proposed Conditions 'IS 4S 2S 2AS 35 SW PA KING NEW BLDG NW FR NT PKG NORTH O NEW BLDG SOUTH MENTRAL ROOF & PKG CB 41 CB2,3.4 CT cB CB-2.3&4 CBE 1 W 7-2 CB-E1 (2) 8X8 ❑R WELLS W-3 W4- 8x8 DRY LL DRYWELLS W-E1 8'x8' DRYWEL 2L 3L 1 L NORTH RUNOFF S UTH RUNOFF SW RUNOFF 4L SITE RUNOFF Su�cat Reach an Link) Drai Prepared ra for PROPns OSED CCONDITIONS JOB AREA ' HydroCADO 9.10 s/n 02373 ©2010 HydroCAD Software Solutions LLC PROPOSED CONDITIONS - JOB AREA Type 11 24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCADO 9.10 s/n 02373 ©2010 H droCAD Software Solutions LLC Page 2 Summary for Subcatchment 1S: SW PARKING Runoff = 1.83 cfs @ 11.93 hrs, Volume= 0.093 af, Depth= 4.33" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type II 24-hr 50-YR Rainfall=4.80" Area (sf) CN Description 0 98 BLDG ROOFS 10,844 98 DRIVES & ROADWAYS 348 39 >75% Grass cover. Good. HSG A 11,192 96 Weighted Average 348 3.11% Pervious Area 10,844 96.89% Impervious Area Tc Length Slope Velocity Capacity Description (min) feet ft/ftft/sec cfs 2.3 300 0.0500 2.14 Sheet Flow, Smooth surfaces n= 0.011 P2= 2.40" 1.1 300 0.0500 4.54 Shallow Concentrated Flow, Paved Kv= 20.3 fps 3.4 600 Total Summary for Subcatchment 2AS: NORTH OF NEW BLDG Runoff = 0.39 cfs @ 11.90 hrs, Volume= 0.016 af, Depth= 1.19" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type II 24-hr 50-YR Rainfall=4.80" Area (sf) CN Description 2,512 98 Paved parking, HSG A 4.607 39 >75% Grass cover, Good, HSG A 7,119 60 Weighted Average 4,607 64.71% Pervious Area 2,512 35.29% Impervious Area Summary for Subcatchment 2S: NW FRONT PKG Runoff = 0.94 cfs @ 11.89 hrs, Volume= 0.042 af, Depth= 3.79" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type 11 24-hr 50-YR Rainfall=4.80" PROPOSED CONDITIONS -JOB AREA Type //24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCADO 9.10 s/n 02373 ©2010 H droCAD Software Solutions LLC Page 3 Area (sf) CN Description 0 98 ROOF 687 39 >75% Grass cover, Good, HSG A 5,075 98 Paved parking. HSG A _ 5,762 91 Weighted Average 687 11.92% Pervious Area 5,075 88.08% Impervious Area Summary for Subcatchment 3S: SOUTH CENTRAL ROOFS & PKG Runoff - 1.74 cfs @ 11.95 hrs, Volume= 0.085 af, Depth= 3.58" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type II 24-hr 50-YR Rainfall=4.80" Area (sf) CN Description 0 98 Roofs, HSG A 10,480 98 Paved parking, HSG A 1,930 39 >75% Grass cover, Good, HSG A 12,410 89 Weighted Average 1,930 15.55% Pervious Area 10,480 84.45% Impervious Area Tc Length Slope Velocity Capacity Description _(min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 4S: NEW BLDG Runoff = 2.00 cfs @ 11.95 hrs, Volume= 0.110 af, Depth= 4.56" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Type II 24-hr 50-YR Rainfall=4.80" Area(sf) CN Description 12.650 98 Roofs, HSG A 12,650 100.00% Impervious Area Tc Length Slope Velocity Capacity Description min)_ (feet) (ft/ft) (ft/sec) (cfs) _ 5.0 Direct Entry, Summary for Pond CB-1: CB-1 Inflow Area = 0.132 ac, 88.08% Impervious, Inflow Depth = 3.79" for 50-YR event Inflow = 0.94 cfs @ 11.89 hrs, Volume= 0.042 of Outflow = 0.94 cfs @ 11.89 hrs, Volume= 0.042 af, Atten= 0%, Lag= 0.0 min Primary = 0.94 cfs @ 11.89 hrs, Volume= 0.042 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs PROPOSED CONDITIONS - JOB AREA Type //24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCADO 9.10 s/n 02373 ©2010 HvdroCAD Software Solutions LLC Page 4 Peak Elev= 522.50' @ 11.89 hrs Device Routing Invert Outlet Devices #1 Primary 522.00' 12.0" Round Culvert L= 15.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 522.00'/521.50' S= 0.0333 '/' Cc= 0.900 n= 0.009 Corrugated PE, smooth interior Primary OutFlow Max=0.89 cfs @ 11.89 hrs HW=522.48' (Free Discharge) L1=Culvert (Inlet Controls 0.89 cfs @ 2.37 fps) Summary for Pond CB-E1: CB-E1 Inflow Area = 0.257 ac, 96.89% Impervious, Inflow Depth = 4.33" for 50-YR event Inflow = 1.83 cfs @ 11.93 hrs, Volume= 0.093 of Outflow = 1.83 cfs @ 11.93 hrs, Volume= 0.093 af, Atten= 0%, Lag= 0.0 min Primary = 1.83 cfs @ 11.93 hrs, Volume= 0.093 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 515.74' @ 11.93 hrs Device Routing Invert Outlet Devices #1 Primary 515.00' 12.0" Round Culvert L= 20.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 515.00'/514.50' S= 0.0250 '/' Cc= 0.900 n= 0.009 Corrugated PE, smooth interior Primary OutFlow Max=1.75 cfs @ 11.93 hrs HW=515.72' (Free Discharge) 't--1=Culvert (Inlet Controls 1.75 cfs @ 2.89 fps) Summary for Pond CB2,3,4: CB-2,3&4 Inflow Area = 0.285 ac, 84.45% Impervious, Inflow Depth = 3.58" for 50-YR event Inflow = 1.74 cfs @ 11.95 hrs, Volume= 0.085 of Outflow = 1.74 cfs @ 11.95 hrs, Volume= 0.085 af, Atten= 0%, Lag= 0.0 min Primary = 1.74 cfs @ 11.95 hrs, Volume= 0.085 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 522.48' @ 11.95 hrs Device Routing Invert Outlet Devices #1 Primary 522.00' 12.0" Round Culvert L= 15.0' CPP, square edge headwall, Ke= 0.500 Inlet/ Outlet Invert= 522.00'/521.50' S= 0.0333 '/' Cc= 0.900 n= 0.009 Corrugated PE, smooth interior #2 Primary 522.00' 12.0" Round Culvert L= 10.0' CPP, square edge headwall, Ke= 0.500 Inlet/ Outlet Invert= 522.00'/521.50' S= 0.0500 '/' Cc= 0.900 n= 0.009 Corrugated PE, smooth interior PROPOSED CONDITIONS - JOB AREA Type //24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 HvdroCAD®9.10 s/n 02373 ©2010 HydroCAD Software Solutions LLC Page 5 Primary OutFlow Max=1.72 cfs @ 11.95 hrs HW=522.47' (Free Discharge) � 1=Culvert (Inlet Controls 0.86 cfs @ 2.34 fps) __2=Culvert (Inlet Controls 0.86 cfs @ 2.34 fps) Summary for Pond DW-3: 8x8 DRYWELL Inflow Area = 0.132 ac, 88.08% Impervious, Inflow Depth = 3.79" for 50-YR event Inflow = 0.94 cfs @ 11.89 hrs, Volume= 0.042 of Outflow = 0.24 cfs @ 12.00 hrs, Volume= 0.042 af, Atten= 74%, Lag= 6.9 min Discarded = 0.24 cfs @ 12.00 hrs, Volume= 0.042 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 511.49' @ 12.00 hrs Surf.Area= 528 sf Storage= 489 cf Plug-Flow detention time= 12.3 min calculated for 0.042 of(100% of inflow) Center-of-Mass det. time= 12.3 min ( 791.7 - 779.4 ) Volume Invert Avail.Storaae Storage Description #1 509.00' 2,725 cf 10.00'D x 9.00'H STONE ENVELOPE Z=1.0 x 3 8,228 cf Overall - 1,416 cf Embedded = 6,812 cf x 40.0% Voids #2 510.00' 1,206 cf 8.00'D x 8.00'H DRYWELL BARREL x 3 Inside#1 1,416 cf Overall -4.0" Wall Thickness = 1,206 cf 3,931 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 509.00' 20.000 in/hr Exfiltration over Surface area #2 Primary 521.00' 12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Qiscarded OutFlow Max=0.24 cfs @ 12.00 hrs HW=511.48' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.24 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=509.00' (Free Discharge) L2=Orifice/Grate ( Controls 0.00 cfs) Summary for Pond DW-E1: 8'x8' DRYWELL Inflow Area = 0.257 ac, 96.89% Impervious, Inflow Depth = 4.33" for 50-YR event Inflow = 1.83 cfs @ 11.93 hrs, Volume= 0.093 of Outflow = 1.89 cfs @ 11.96 hrs, Volume= 0.093 af, Atten= 0%, Lag= 1.8 min Discarded = 0.24 cfs @ 11.97 hrs, Volume= 0.077 of Primary = 1.65 cfs @ 11.96 hrs, Volume= 0.015 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 516.73' @ 11.97 hrs Surf.Area= 509 sf Storage= 991 cf Plug-Flow detention time= 27.9 min calculated for 0.093 of(100% of inflow) Center-of-Mass det. time= 27.9 min ( 785.1 - 757.2 ) PROPOSED CONDITIONS -JOB AREA Type 11 24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCAD@ 9.10 s/n 02373 ©2010 H droCAD Software Solutions LLC Page 6 Volume Invert Avail.Storage Storage Description #1 509.00' 1,173 cf 10.00'D x 10.00'H STONE ENVELOPE Z=1.0 3,403 cf Overall -472 cf Embedded = 2,931 cf x 40.0% Voids #2 510.00' 402 cf 8.00'D x 8.00'H DRYWELL BARREL Inside#1 472 cf Overall -4.0" Wall Thickness = 402 cf 1,575 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 509.00' 20.000 in/hr Exfiltration over Surface area #2 Primary 516.00' 12.0" Round OUTLET PIPE L= 20.0' CPP, square edge headwall, Ke= 0.500 Inlet/ Outlet Invert= 516.00' / 515.70' S= 0.0150 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior discarded OutFlow Max-70.23 cfs @ 11.97 hrs HW=516.66' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.23 cfs) rirnary OutFlow Max=1.46 cfs @ 11.96 hrs HW=516.66' (Free Discharge) 2=OUTLET PIPE (Barrel Controls 1.46 cfs @ 3.75 fps) Summary for Pond DW1-2: (2) 8X8 DRYWELLS Inflow Area = 0.290 ac,100.00% Impervious, Inflow Depth = 4.56" for 50-YR event Inflow = 2.00 cfs @ 11.95 hrs, Volume= 0.110 of Outflow = 0.57 cfs @ 12.09 hrs, Volume= 0.110 af, Atten= 72%, Lag= 8.4 min Discarded = 0.57 cfs @ 12.09 hrs, Volume= 0.110 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 511.85' @ 12.09 hrs Surf.Area= 1,222 sf Storage= 1,219 cf Plug-Flow detention time= 13.1 min calculated for 0.110 of(100% of inflow) Center-of-Mass det. time= 13.1 min ( 756.8 - 743.7 ) Volume Invert Avail.Stora a Storage Description #1 509.00' 2,725 cf 10.00'D x 9.00'H STONE ENVELOPE Z=1.0 x 3 8,228 cf Overall - 1,416 cf Embedded = 6,812 cf x 40.0% Voids #2 510.00' 1,206 cf 8.00'D x 8.00'H DRYWELL BARREL x 3 Inside#1 1,416 cf Overall -4.0" Wall Thickness = 1,206 cf #3 511.00' 33 cf 3.00'W x 10.001 x 3.00'H CONNECTOR TRENCH 90 cf Overall - 8 cf Embedded = 82 cf x 40.0% Voids #4 512.00' 8 cf 12.0" D x 10.0'L CONNECTOR PIPE Inside#3 3,972 cf x 2.00 = 7,944 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 509.00' 20.000 in/hr Exfiltration over Surface area #2 Primary 521.00' 12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads PROPOSED CONDITIONS - JOB AREA Type // 24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 HvdroCADO 9.10 s/n 02373 ©2010 H droCAD Software Solutions LLC Page 7 Discarded OutFlow Max=0.56 cfs @ 12.09 hrs HW=511.84' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.56 cfs) rimary OutFlow Max=0.00 cfs @ 0.00 hrs HW=509.00' (Free Discharge) Z=Orifice/Grate ( Controls 0.00 cfs) Summary for Pond DW4-5: (2) 8'x8' DRYWELLS Inflow Area = 0.285 ac, 84.45% Impervious, Inflow Depth = 3.58" for 50-YR event Inflow = 1.74 cfs @ 11.95 hrs, Volume= 0.085 of Outflow = 0.42 cfs @ 12.11 hrs, Volume= 0.085 af, Atten= 76%, Lag= 9.2 min Discarded = 0.42 cfs @ 12.11 hrs, Volume= 0.085 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Peak Elev= 512.53' @ 12.11 hrs Surf.Area= 914 sf Storage= 1,100 cf Plug-Flow detention time= 18.3 min calculated for 0.085 of(100% of inflow) Center-of-Mass det. time= 18.3 min ( 810.0 - 791.7 ) Volume Invert Avail.Stora a Storage Description #1 509.00' 1,817 cf 10.00'D x 9.00'H STONE ENVELOPE Z=1.0 x 2 5,485 cf Overall - 944 cf Embedded = 4,541 cf x 40.0% Voids #2 510.00' 804 cf 8.00'D x 8.00'H DRYWELL BARREL x 2 Inside#1 944 cf Overall -4.0" Wall Thickness = 804 cf #3 515.00' 33 cf 3.00'W x 10.001 x 3.00'H CONNECTOR TRENCH 90 cf Overall - 8 cf Embedded = 82 cf x 40.0% Voids #4 516.00' 8 cf 12.0" D x 10.0'L CONNECTOR PIPE Inside #3 2,661 cf x 2.00 = 5,323 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 509.00' 20.000 in/hr Exfiltration over Surface area #2 Primary 521.00' 12.0"Vert. Orifice/Grate C= 0.600 Piscarded OutFlow Max=0.42 cfs @ 12.11 hrs HW=512.52' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.42 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=509.00' (Free Discharge) '-2=Orifice/Grate ( Controls 0.00 cfs) Summary for Link 1 L: SW RUNOFF Inflow Area = 0.547 ac, 98.54% Impervious, Inflow Depth = 0.34" for 50-YR event Inflow = 1.65 cfs @ 11.96 hrs, Volume= 0.015 of Primary = 1.65 cfs @ 11.96 hrs, Volume= 0.015 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs PROPOSED CONDITIONS -JOB AREA Type // 24-hr 50-YR Rainfall=4.80" Prepared by Hutchins Engineering Printed 4/16/2018 H droCAD®9.10 s/n 02373 ©2010 H droCAD Software Solutions LLC Page 8 Summary for Link 2L: NORTH RUNOFF Inflow Area = 0.296 ac, 58.90% Impervious, Inflow Depth = 0.66" for 50-YR event Inflow = 0.39 cfs @ 11.90 hrs, Volume= 0.016 of Primary = 0.39 cfs @ 11.90 hrs, Volume= 0.016 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Summary for Link 3L: SOUTH RUNOFF Inflow Area = 0.285 ac, 84.45% Impervious, Inflow Depth = 0.00" for 50-YR event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs Summary for Link 4L: SITE RUNOFF Inflow Area = 1.128 ac, 84.59% Impervious, Inflow Depth = 0.34" for 50-YR event Inflow = 1.88 cfs @ 11.96 hrs, Volume= 0.032 of Primary = 1.88 cfs @ 11.96 hrs, Volume= 0.032 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-26.00 hrs, dt= 0.05 hrs