Revised Stormwater Management Report. Self-Storage Development. Wheeler Road Burlington, Massachusetts

Transcription

1 An Employee-Owned Company Revised Stormwater Management Report For the Proposed: Self-Storage Development Located at: Wheeler Road Burlington, Massachusetts Prepared for Submission to: Town of Burlington, MA October 23, 201 Revised: January 19, 201 February 1, 201 Prepared for: Jumbo Self Storage, LLC 1900 Crown Colony Drive, 4 th Floor Quincy, MA 0219 Prepared by: BL Companies 3 Research Parkway Meriden, Connecticut 040 Phone: (203) Fax: (203) BL Project Number: 1D323

2 An Employee-Owned Company Stormwater Management Report Contents Executive Summary... 1 Existing Site Conditions and Hydrologic Conditions... 2 Developed Site Conditions and Hydrologic Conditions... 4 Stormwater Management... Summary... Appendix A: Aerial Map NRCS Soil Report FEMA Flood Insurance Rate Map NOAA Atlas 14 Storm Data Appendix B: Pre-development Hydrology (2-, 10-, 2-, and 100-year storms) Appendix C: Post-development Hydrology (2-, 10-, 2-, and 100-year storms) Appendix D: Water Quality Calculations (Massachusetts Stormwater Handbook Calculations) Appendix E: Drainage Maps Appendix F: Stormwater System Operations and Maintenance Plan Appendix G: Geotechnical Report Note: Only revised appendices have been included in this revised report. Refer to 10/23/1 and 1/19/1 reports for appendix A, B, F and G.

3 An Employee-Owned Company Stormwater Management Report Executive Summary This report has been prepared in support of an application by Jumbo Self Storage LLC for a detailed site development plan application to the Town of Burlington for the proposed development at the corner of Wheeler Road and Blanchard Road. The property is approximately 11 acres in size and is currently undeveloped in the existing condition. The parcel is bounded by Wheeler Road to the south, Blanchard Road to the to the east, Rounder Way (A.K.A Commonwealth Executive Drive) to the north, a commercial hotel development to the west. The proposed development will provide one new -story, 119,033 s.f. self-storage building on the eastern portion of the site. The proposed structure will have a finished first floor above the 100-year FEMA floodplain and will not have a basement. The proposed development is subject to the Massachusetts Wetlands Protection Act (M.G.L. Chapter 131, Section 40), and the implementing regulations (310 CMR 10.00) because the new development is located on a site within the 200-foot Riverfront Area and on bordering land subject to flooding. The project is subject to the DEP Stormwater Policy for new development. Although the existing site is undeveloped, it has historically been disturbed, is lacking topsoil in many areas, and has become an abandoned dumping ground for construction equipment and debris. The site is not located within or adjacent to an Area of Critical Environmental Concern and according to the 200 NHESP rare species database and the 2003 certified vernal pool database on MASGIS, no known state-listed species of special concern, core habitat for rare species or vernal pools occur on or in the immediate vicinity of the Site. Existing topography across the eastern portion of the site generally slopes from the east to west portion toward the existing creek. Elevations vary from 14 feet to 134 feet across the site. The eastern portion of the property discharges directly to a small unnamed tributary to Vine Brook that runs through the center of the site. The unnamed tributary converges with Vine Brook west of the site. Vine Brook runs north under Rte. 9 and past the Burlington Mall and ultimately discharges into the Shawsheen River in Bedford which then in turn, empties into the Merrimack River in Lawrence. The Merrimack river then empties into the Atlantic Ocean in Newburyport. The proposed stormwater management system is designed to follow the Massachusetts Stormwater Handbook, the Massachusetts Wetlands Protection Act regulations (310 CMR 10.00), and the 2003 Massachusetts Erosion and Sediment Control Guidelines for Urban and Suburban Areas to the maximum extent practical. The State of Massachusetts requires that the peak flows of stormwater runoff from the proposed development for all intensities and durations of rainfall up to the 100-year storm event shall not 3 Research Parkway Meriden, CT 040 T (203) F (203)

4 An Employee-Owned Company Stormwater Management Report exceed the existing condition peak flows of stormwater runoff. A HydroCad model, using TR- methodology (HydroCAD Release 10.0), was developed to evaluate the existing and proposed drainage conditions of the property. The results of the analysis demonstrate that there will be a decrease in peak stormwater runoff rates for the 2-, 10-, 2-, and 100-year storm events under the developed site conditions. The reduction in runoff rates is attributed to the storage volume generated by the proposed underground detention/recharge system. The proposed drainage design will also provide water quality improvements where currently none exist. Numerous water quality best management practices (BMPs) have been incorporated into the project design and include a rain garden, catch basins, a hydrodynamic separator and an underground detention system with infiltration. The proposed treatment train as designed is expected to remove and exceed the required 44% of TSS removal prior to discharge into the infiltration system and then to the discharge point. Calculations can be found in Appendix D. Existing Site Conditions and Hydrologic Conditions General Site Information The subject property is an undeveloped wooded lot. However, historically it has been disturbed with filling activities and by storage of construction material in various areas on site and based on the geotechnical report, much of the site is lacking a layer of topsoil. A creek, an unnamed tributary of Vine Brook, traverses through the center of the site. The banks of the creek are vegetated with trees and undergrowth. The topography of the eastern portion of the site generally slopes from the corner of Wheeler Road and Blanchard Road toward the creek. There are currently no existing drainage facilities onsite and all stormwater sheet flows untreated from the site into the creek. Likewise, there are no stormwater management systems or water quality measures present onsite to treat the existing runoff. Surrounding properties also contribute stormwater overland to this creek. The site is located in the 100-year floodplain. Per the FEMA Flood Insurance Rate Map Number 201C0402E for Middlesex County, Massachusetts, map effective date: June 4, 2010, the site resides inside FEMA designated flood areas Zone AE (special flood hazard areas subject to inundation by the 100-year annual chance flood with base flood elevation determined). The base flood elevation is Elev. 140 feet (NGVD) across the length of the site. Based on this elevation of the floodplain, floodwaters extend across most of the site during large storm events. According to FEMA floodplain mapping, the site also has areas classified as Zone X (areas determined to be outside the 0.2% annual chance floodplain), Zone XEA (shaded) and a Floodway associated with this creek. Copies of the FEMA Flood Insurance Rate Maps are included in Appendix A for reference. 3 Research Parkway Meriden, CT 040 T (203) F (203)

5 An Employee-Owned Company Stormwater Management Report There are isolated wetlands on site. There are no vernal pools, or endangered species on the property. The site soil in the proposed development area is identified by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) as Udorthents-Urban Land. The hydrologic soil group is identified as D. A copy of the USDA NRCS Hydrologic Soil Group Map is included in Appendix A for reference. Existing Hydrologic Conditions Only the site area to the east of the existing creek has been analyzed as the area to the west of the creek is unaffected by the project. The existing site drainage area that was analyzed totals 3.- acres and is approximately.4% impervious with 13,939 s.f. of impervious surface. Stormwater runoff from the property flows to one distinct point onsite. Below is a description of this individual point. The following is a brief analysis of the existing design point as shown on the enclosed Existing Drainage Area Map (ED-1), in Appendix E; Existing Drainage Area 1 (ED-1): The existing drainage area 1 collects stormwater from a 3.- acre portion of the site with a time of concentration of 43.2 minutes. The ED-1 is approximately.4% impervious with 0.32 ac of impervious surface. This drainage area consists of the eastern portion of the site along Wheeler and Blanchard Roads. This portion of the site consists of existing wooded areas and a small portion of existing parking lot area associated with the abutting property to the north. The existing survey indicates that this portion of this site currently drains to the onsite creek. The creek then flows under Rounder Way via two 30 RCP culverts. Table 1 Pre-Development (Existing Conditions) Drainage Characteristics. Area Composite Impervious (acres) Curve Number Cover (%) Drainage Area / Design Point Time of Concentration (minutes) ED-1: Direct Offsite Table 2 Pre-Development Conditions Peak Flows Peak Flow (cfs) Analysis Point 2-yr 10-yr 2-yr 100-yr Discharge Point Research Parkway Meriden, CT 040 T (203) F (203)

6 An Employee-Owned Company Stormwater Management Report Developed Site Conditions and Hydrologic Conditions General Site Information The proposed development will provide one new -story, 119,033 s.f. self-storage building. The first floor is approximately 9,33 s.f. with a second through fifth floor is approximately 2,30 s.f. each. The second floor cantilevers over the loading and 3 car parking area. An office space will be provided at the front of the building facing Wheeler Road and loading area along the western building façade. A full access driveway is proposed onto Wheeler Road. There are 12 proposed parking spaces, which will provide adequate parking for the use. Only 9 of the 12 spaces will be placed out side and exposed to the elements. The remaining three are located under the portion of the building that is cantilevered with columns. The proposed slab-on-grade structure will have a finished first floor above the 100-year FEMA floodplain elevation. The loading area and main portion of the building will have the finished floors set at elevation and FEMA mapping has determined an elevation of for the 100-year floodplain at the proposed building. The office portion of the building will be set higher, at elevation 14.1, in order to meet grades along Wheeler Road. Internal ramps will accommodate this change in elevation. Compensatory storage will be provided on the site in order to mitigate the impacts of the proposed development. The proposed site grading plan is providing for and overall 1:1 compensatory storage to help mitigate the flooding impacts of existing creek. This calculation excludes any stormwater storage area provided by the underground detention. Proposed Hydrologic Conditions The eastern portion of the proposed site drainage area totals 3.-acres and is approximately 30.3% impervious with 1.11 acres of impervious surface. This is an increase in impervious surface of 0.9 acres from the existing to proposed conditions. The intent of the proposed site drainage system is to mimic existing drainage patterns and rates as much as possible. The site stormwater system will provide rate control with detention/infiltration system as well as water quality improvements through the installation of a rain garden and hydrodynamic separator. The post development site stormwater modeling retained the same Design Point as the existing conditions model. The following drainage areas were developed to model the proposed site 3 Research Parkway Meriden, CT 040 T (203) F (203)

7 An Employee-Owned Company Stormwater Management Report improvements. The proposed design point is shown on the enclosed Post-development Drainage Area Map (PD-1), in Appendix E. Proposed Drainage Area 1 (PD-1): The proposed drainage area 1 collects water from a 2.1-acre portion of the site with a time of concentration of 41. minutes. PD-1 is approximately 11.% impervious with 0.32 of impervious surface. This drainage area consists of the western portion of the developed site east of the creek. As in the existing condition, this portion of this site will drain overland to the existing creek that bisects the site. A portion of this area is being regraded to allow for compensatory flood water storage. Proposed Drainage Area 2A (PDA-2A): The proposed drainage area PD-2A collects water from a 0.4-acre portion of the site with a time of concentration of.0 minutes. PD-2A is 100% impervious. This drainage area consists of the proposed building roof. The outlet control structure for the system will be a manhole structure with various orifices and a weir to control the outflow. Proposed Drainage Area 2B (PDA-2B): The proposed drainage area PD-2B collects water from a 0.31-acre portion of the site with a time of concentration of. minutes. PD-2B is approximately 4.3% impervious with 0.1 acres of impervious surface. This drainage area consists of the parking area to the southeast of the building. The stormwater runoff from the uncovered parking area will first sheet flow into a rain garden which will discharge through a hydrodynamic separator prior to being conveyed to the underground detention/infiltration system. The outlet control structure for the system will be a manhole structure with various orifices and a weir to control the outflow. Table 3 Post Development Drainage Characteristics. Drainage Area / Design Point Area (acres) Composite Curve Number Impervious Cover (%) Time of Concentration (minutes) PD PD-2A PD-2B Table 4 Post-Development Conditions Peak Flows Peak Flow (cfs) Analysis Point 2-yr 10-yr 2-yr 100-yr Discharge Point Research Parkway Meriden, CT 040 T (203) F (203)

8 An Employee-Owned Company Stormwater Management Report Table Existing vs Proposed Peak Rates of Runoff Peak Flow Rate in Cubic Feet per Second (cfs) Drainage Area 2-yr 10-yr 2-yr 100-yr Discharge Pt. 1 Existing Proposed Percent Change -12.4% -11.4% -9.% -.% Stormwater Management Hydrologic Modeling of the Entire Site The hydrologic analysis to determine peak stormwater discharge rates was performed using the HydroCAD stormwater modeling system computer program, version developed by HydroCAD Software Solutions, LLC. Hydrographs for each watershed were developed using the SCS Synthetic Unit Hydrograph Method with a Type III rainfall distribution with Antecedent Moisture Condition II. Rainfall depths per the NOAA Atlas 14 for Burlington, Mass were used for the calculation of peak flow rates and are listed in Table. The drainage areas, or subcatchments as labeled by the program, are depicted by hexagons on the attached drainage diagrams. Pre-development HydroCAD output can be found in Appendix B and Post-development HydroCAD output can be found in Appendix C. Proposed Storm Water Quality Table Rainfall Depths per NOAA Atlas 14 Appendix B - 24-hour Rainfall Data Return Period 24-hour Rainfall Depth 2-year year.1 2-year year.1 Along with the reduction of peak storm water discharge rates, an important element of the proposed drainage system is to improve the quality of stormwater runoff leaving the property. To do this, Best Management Practices (BMP s) have been implemented in this design. 3 Research Parkway Meriden, CT 040 T (203) F (203)

9 An Employee-Owned Company Stormwater Management Report A Rain Garden, Hydrodynamic Separator and a Detention/infiltration system will be installed to provide the water quality storage volume, as well as recharge and infiltrate runoff to the maximum extent practical. Summary The stormwater management system has been designed to safely collect, treat, convey, and improve the quality of the runoff being discharged from the site. Computer modeling of the proposed systems have demonstrated a reduction in post-development peak rates of runoff to below pre-development levels. With proper annual maintenance the stormwater conveyance system, catch basins, manholes, rain garden and water quality structure should operate as anticipated for years to come. The proposed development will decrease the proposed 2-year, 10-year, 2-year, and 100-year storm event peak flows generated by the site and will reduce total runoff volume due to the infiltration system. The proposed drainage network will safely convey the runoff from the site during the storm events as required per Commonwealth of Massachusetts regulations. The drainage system will infiltrate the runoff to the maximum extent practical while adhering to site constraints. This report has been prepared to compliment the submitted project plans as well as to represent the technical basis for the designs presented herein. In consideration of the overall project, we conclude that all technical concerns and design parameters set forth by the Town of Burlington and Commonwealth of Massachusetts have been met to the maximum extent practical. 3 Research Parkway Meriden, CT 040 T (203) F (203)

10 An Employee-Owned Company Stormwater Management Report APPENDIX C POST-DEVELOPMENT HYDROLOGY 3 Research Parkway Meriden, CT 040 T (203) F (203)

11 PD1 Drainage Area #1 PD2A Roof Area 2P Design Point 1 1P Detention System 4P Rain Garden PD2B Developed Area Subcat Reach Pond Link Routing Diagram for 1D323-ProposedHydrology ,

12 Page 2 Area (acres) CN Description (subcatchment-numbers) Area Listing (all nodes) >% Grass cover, Good, HSG D (PD1, PD2B) Paved parking, HSG D EXIST (PD1) Paved parking, HSG D NEW (PD2B) Roofs, HSG D NEW ROOF (PD2A) Woods, Fair, HSG D (PD1, PD2B) 3.0 TOTAL AREA

13 Page 3 Area (acres) Soil Group Subcatchment Numbers HSG A HSG B HSG C 3.0 HSG D PD1, PD2A, PD2B Other 3.0 TOTAL AREA Soil Listing (all nodes)

14 Page 4 HSG-A (acres) HSG-B (acres) HSG-C (acres) Ground Covers (all nodes) HSG-D (acres) Other (acres) Total (acres) Ground Cover >% Grass cover, Good PD1, PD2B Paved parking PD1, PD2B Roofs PD2A Woods, Fair PD1, PD2B TOTAL AREA Subcatchment Numbers

15 Page Line# Node Number In-Invert (feet) Out-Invert (feet) Pipe Listing (all nodes) Length (feet) Slope (ft/ft) n Diam/Width (inches) Height (inches) Inside-Fill (inches) 1 1P

16 Type II 24-hr 2-year Rainfall=3.2" Page Time span= hrs, dt=0.0 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment PD1: Drainage Area #1 Subcatchment PD2A: Roof Area Subcatchment PD2B: Developed Area Runoff Area=2.10 ac 11.1% Impervious Runoff Depth>1.3" Flow Length=10' Tc=41. min CN=1 Runoff=2.2 cfs af Runoff Area=0.40 ac % Impervious Runoff Depth>2.0" Tc=.0 min CN=9 Runoff=2.9 cfs af Runoff Area=0.310 ac 4.39% Impervious Runoff Depth>1.91" Flow Length=14' Tc=. min CN= Runoff=1.00 cfs af Pond 1P: Detention System Peak Elev=13.31' Storage=2,3 cf Inflow=2.9 cfs af Discarded=0.14 cfs af Primary=0.4 cfs af Outflow=0.1 cfs af Pond 2P: Design Point 1 Inflow=3.22 cfs af Primary=3.22 cfs af Pond 4P: Rain Garden Peak Elev=143.22' Storage=1,11 cf Inflow=1.00 cfs af Discarded=0.0 cfs 0.03 af Primary=0.00 cfs af Outflow=0.0 cfs 0.03 af Total Runoff Area = 3.0 ac Runoff Volume = 0.0 af Average Runoff Depth = 1." 9.% Pervious = 2.0 ac 30.33% Impervious = ac

17 Type II 24-hr 2-year Rainfall=3.2" Page Summary for Subcatchment PD1: Drainage Area #1 Runoff = hrs, Volume= af, Depth> 1.3" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 2-year Rainfall=3.2" Area (ac) CN Description * Paved parking, HSG D EXIST Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall con2 Woodland Kv=.0 fps Shallow Concentrated Flow, shall to DP1 Woodland Kv=.0 fps Total Subcatchment PD1: Drainage Area #1 Hydrograph Flow (cfs) cfs Type II 24-hr 2-year Rainfall=3.2" Runoff Area=2.10 ac Runoff Volume=0.310 af Runoff Depth>1.3" Flow Length=10' Tc=41. min CN=1 Runoff Time (hours)

18 Type II 24-hr 2-year Rainfall=3.2" Page Summary for Subcatchment PD2A: Roof Area Runoff = hrs, Volume= af, Depth> 2.0" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 2-year Rainfall=3.2" Area (ac) CN Description * Roofs, HSG D NEW ROOF % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs).0 Direct Entry, Subcatchment PD2A: Roof Area Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 2-year Rainfall=3.2" Runoff Area=0.40 ac Runoff Volume=0.149 af Runoff Depth>2.0" Tc=.0 min CN= Time (hours)

19 Type II 24-hr 2-year Rainfall=3.2" Page 9 Summary for Subcatchment PD2B: Developed Area Runoff = hrs, Volume= af, Depth> 1.91" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 2-year Rainfall=3.2" Area (ac) CN Description * Paved parking, HSG D NEW Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall conc Paved Kv= 20.3 fps Shallow Concentrated Flow, Short Grass Pasture Kv=.0 fps. 14 Total Subcatchment PD2B: Developed Area Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 2-year Rainfall=3.2" Runoff Area=0.310 ac Runoff Volume=0.049 af Runoff Depth>1.91" Flow Length=14' Tc=. min CN= Time (hours)

20 Type II 24-hr 2-year Rainfall=3.2" Page 10 Summary for Pond 1P: Detention System Inflow Area = 0.90 ac, 3.1% Impervious, Inflow Depth > 1.9" for 2-year event Inflow = hrs, Volume= af Outflow = hrs, Volume= af, Atten= 0%, Lag= 10.0 min Discarded = hrs, Volume= af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Peak Elev= hrs Surf.Area= 2,99 sf Storage= 2,3 cf Plug-Flow detention time= 4.0 min calculated for 0.14 af (99% of inflow) Center-of-Mass det. time= 2.2 min ( ) Volume Invert Avail.Storage Storage Description # ' 3,0 cf 3.0" Round CMP_Round 3" x Inside #2 L=.0' #2 13.0' 2,13 cf Custom Stage Data (Prismatic)Listed below (Recalc) 10,0 cf Overall - 3,0 cf Embedded =,2 cf x 30.0% Voids # ' 393 cf.00'd x.00'h Vertical Cone/Cylinder x 4,10 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , ,20 10,0 10,0 Device Routing Invert Outlet Devices #1 Primary 13.0' 1.0" Round Culvert L= 0.0' RCP, sq.cut end projecting, Ke= 0.00 Inlet / Outlet Invert= 13.0' / 13.02' S= '/' Cc= n= Corrugated PE, smooth interior, Flow Area= 1. sf #2 Device '.0" Vert. Orifice/Grate C= 0.00 #3 Device 1 13.'.0" Vert. Orifice/Grate C= 0.00 #4 Device '.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) # Discarded 13.0' 1.00 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 131.0' Discarded OutFlow Max= hrs HW=13.30' (Free Discharge) =Exfiltration ( Controls 0.14 cfs) Primary OutFlow Max= hrs HW=13.30' (Free Discharge) 1=Culvert (Passes 0.4 cfs of 2.0 cfs potential flow) 2=Orifice/Grate (Orifice Controls fps) 3=Orifice/Grate ( Controls 0.00 cfs) 4=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)

21 Type II 24-hr 2-year Rainfall=3.2" Page 11 Pond 1P: Detention System Hydrograph cfs Inflow Area=0.90 ac Peak Elev=13.31' Storage=2,3 cf Inflow Outflow Discarded Primary Flow (cfs) cfs 0.4 cfs 0.14 cfs Time (hours)

22 Type II 24-hr 2-year Rainfall=3.2" Page 12 Summary for Pond 2P: Design Point 1 Inflow Area = 3.0 ac, 30.33% Impervious, Inflow Depth > 1.14" for 2-year event Inflow = hrs, Volume= af Primary = hrs, Volume= af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Pond 2P: Design Point 1 Hydrograph 3.22 cfs 3.22 cfs Inflow Area=3.0 ac Inflow Primary 3 Flow (cfs) Time (hours)

23 Type II 24-hr 2-year Rainfall=3.2" Page 13 Summary for Pond 4P: Rain Garden Inflow Area = ac, 4.39% Impervious, Inflow Depth > 1.91" for 2-year event Inflow = hrs, Volume= af Outflow = hrs, Volume= 0.03 af, Atten= 9%, Lag=.1 min Discarded = hrs, Volume= 0.03 af Primary = 0.00 hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Peak Elev= hrs Surf.Area= 99 sf Storage= 1,11 cf Plug-Flow detention time= min calculated for 0.03 af (% of inflow) Center-of-Mass det. time= min ( ) Volume Invert Avail.Storage Storage Description # ' 1, cf Custom Stage Data (Prismatic)Listed below (Recalc) Inside #2 # ' 4 cf Custom Stage Data (Prismatic)Listed below (Recalc) 4,0 cf Overall - 1, cf Embedded = 3,119 cf x 1.0% Voids 2,0 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , ,00 2 1, Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) ,41 4, ,00 2 4,0 Device Routing Invert Outlet Devices #1 Primary ' 24.0" x 3.0" Horiz. Orifice/Grate C= 0.00 Limited to weir flow at low heads #2 Discarded 139.0' 1.00 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = ' Discarded OutFlow Max= hrs HW=143.22' (Free Discharge) 2=Exfiltration ( Controls 0.0 cfs) Primary OutFlow Max=0.00 hrs HW=139.0' (Free Discharge) 1=Orifice/Grate ( Controls 0.00 cfs)

24 Type II 24-hr 2-year Rainfall=3.2" Page 14 Pond 4P: Rain Garden Hydrograph cfs Inflow Area=0.310 ac Peak Elev=143.22' Storage=1,11 cf Inflow Outflow Discarded Primary Flow (cfs) 0.0 cfs 0.0 cfs 0.00 cfs Time (hours)

25 Type II 24-hr 10-year Rainfall=.1" Page 1 Time span= hrs, dt=0.0 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment PD1: Drainage Area #1 Subcatchment PD2A: Roof Area Subcatchment PD2B: Developed Area Runoff Area=2.10 ac 11.1% Impervious Runoff Depth>2." Flow Length=10' Tc=41. min CN=1 Runoff=.9 cfs 0.4 af Runoff Area=0.40 ac % Impervious Runoff Depth>4.0" Tc=.0 min CN=9 Runoff=4.4 cfs af Runoff Area=0.310 ac 4.39% Impervious Runoff Depth>3." Flow Length=14' Tc=. min CN= Runoff=1.1 cfs af Pond 1P: Detention System Peak Elev=13.09' Storage=4,19 cf Inflow=4.4 cfs 0.24 af Discarded=0.1 cfs af Primary=1.39 cfs af Outflow=1. cfs af Pond 2P: Design Point 1 Inflow=.4 cfs 0.0 af Primary=.4 cfs 0.0 af Pond 4P: Rain Garden Peak Elev=144.0' Storage=1, cf Inflow=1.1 cfs af Discarded=0.0 cfs 0.04 af Primary=0.2 cfs af Outflow=0. cfs 0.00 af Total Runoff Area = 3.0 ac Runoff Volume = 0.9 af Average Runoff Depth = 3.21" 9.% Pervious = 2.0 ac 30.33% Impervious = ac

26 Type II 24-hr 10-year Rainfall=.1" Page 1 Summary for Subcatchment PD1: Drainage Area #1 Runoff = hrs, Volume= 0.4 af, Depth> 2." Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 10-year Rainfall=.1" Area (ac) CN Description * Paved parking, HSG D EXIST Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall con2 Woodland Kv=.0 fps Shallow Concentrated Flow, shall to DP1 Woodland Kv=.0 fps Total Subcatchment PD1: Drainage Area #1 Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 10-year Rainfall=.1" Runoff Area=2.10 ac Runoff Volume=0.4 af Runoff Depth>2." Flow Length=10' Tc=41. min CN= Time (hours)

27 Type II 24-hr 10-year Rainfall=.1" Page 1 Summary for Subcatchment PD2A: Roof Area Runoff = hrs, Volume= af, Depth> 4.0" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 10-year Rainfall=.1" Area (ac) CN Description * Roofs, HSG D NEW ROOF % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs).0 Direct Entry, Subcatchment PD2A: Roof Area Hydrograph Flow (cfs) cfs Type II 24-hr 10-year Rainfall=.1" Runoff Area=0.40 ac Runoff Volume=0.240 af Runoff Depth>4.0" Tc=.0 min CN=9 Runoff Time (hours)

28 Type II 24-hr 10-year Rainfall=.1" Page 1 Summary for Subcatchment PD2B: Developed Area Runoff = hrs, Volume= af, Depth> 3." Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 10-year Rainfall=.1" Area (ac) CN Description * Paved parking, HSG D NEW Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall conc Paved Kv= 20.3 fps Shallow Concentrated Flow, Short Grass Pasture Kv=.0 fps. 14 Total Subcatchment PD2B: Developed Area Hydrograph 2 Runoff Flow (cfs) cfs Type II 24-hr 10-year Rainfall=.1" Runoff Area=0.310 ac Runoff Volume=0.092 af Runoff Depth>3." Flow Length=14' Tc=. min CN= Time (hours)

29 Type II 24-hr 10-year Rainfall=.1" Page 19 Summary for Pond 1P: Detention System Inflow Area = 0.90 ac, 3.1% Impervious, Inflow Depth > 3.21" for 10-year event Inflow = hrs, Volume= 0.24 af Outflow = hrs, Volume= af, Atten= %, Lag=. min Discarded = hrs, Volume= af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Peak Elev= 12.0 hrs Surf.Area= 2,99 sf Storage= 4,19 cf Plug-Flow detention time=.0 min calculated for af (9% of inflow) Center-of-Mass det. time=.1 min ( ) Volume Invert Avail.Storage Storage Description # ' 3,0 cf 3.0" Round CMP_Round 3" x Inside #2 L=.0' #2 13.0' 2,13 cf Custom Stage Data (Prismatic)Listed below (Recalc) 10,0 cf Overall - 3,0 cf Embedded =,2 cf x 30.0% Voids # ' 393 cf.00'd x.00'h Vertical Cone/Cylinder x 4,10 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , ,20 10,0 10,0 Device Routing Invert Outlet Devices #1 Primary 13.0' 1.0" Round Culvert L= 0.0' RCP, sq.cut end projecting, Ke= 0.00 Inlet / Outlet Invert= 13.0' / 13.02' S= '/' Cc= n= Corrugated PE, smooth interior, Flow Area= 1. sf #2 Device '.0" Vert. Orifice/Grate C= 0.00 #3 Device 1 13.'.0" Vert. Orifice/Grate C= 0.00 #4 Device '.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) # Discarded 13.0' 1.00 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 131.0' Discarded OutFlow Max= hrs HW=13.09' (Free Discharge) =Exfiltration ( Controls 0.1 cfs) Primary OutFlow Max= hrs HW=13.09' (Free Discharge) 1=Culvert (Passes 1.3 cfs of.9 cfs potential flow) 2=Orifice/Grate (Orifice Controls 0.4 fps) 3=Orifice/Grate (Orifice Controls fps) 4=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)

30 Type II 24-hr 10-year Rainfall=.1" Page 20 Pond 1P: Detention System Hydrograph cfs Inflow Area=0.90 ac Peak Elev=13.09' Storage=4,19 cf Inflow Outflow Discarded Primary Flow (cfs) cfs 1.39 cfs cfs Time (hours)

31 Type II 24-hr 10-year Rainfall=.1" Page 21 Summary for Pond 2P: Design Point 1 Inflow Area = 3.0 ac, 30.33% Impervious, Inflow Depth > 2.49" for 10-year event Inflow = hrs, Volume= 0.0 af Primary = hrs, Volume= 0.0 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Pond 2P: Design Point 1 Hydrograph.4 cfs.4 cfs Inflow Area=3.0 ac Inflow Primary Flow (cfs) Time (hours)

32 Type II 24-hr 10-year Rainfall=.1" Page 22 Summary for Pond 4P: Rain Garden Inflow Area = ac, 4.39% Impervious, Inflow Depth > 3." for 10-year event Inflow = hrs, Volume= af Outflow = hrs, Volume= 0.00 af, Atten= %, Lag= 10. min Discarded = hrs, Volume= 0.04 af Primary = hrs, Volume= af Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Peak Elev= 12.1 hrs Surf.Area= 1,00 sf Storage= 1, cf Plug-Flow detention time= 10.3 min calculated for 0.00 af (% of inflow) Center-of-Mass det. time= 1.9 min ( ) Volume Invert Avail.Storage Storage Description # ' 1, cf Custom Stage Data (Prismatic)Listed below (Recalc) Inside #2 # ' 4 cf Custom Stage Data (Prismatic)Listed below (Recalc) 4,0 cf Overall - 1, cf Embedded = 3,119 cf x 1.0% Voids 2,0 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , ,00 2 1, Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) ,41 4, ,00 2 4,0 Device Routing Invert Outlet Devices #1 Primary ' 24.0" x 3.0" Horiz. Orifice/Grate C= 0.00 Limited to weir flow at low heads #2 Discarded 139.0' 1.00 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = ' Discarded OutFlow Max= hrs HW=144.0' (Free Discharge) 2=Exfiltration ( Controls 0.0 cfs) Primary OutFlow Max= hrs HW=144.0' (Free Discharge) 1=Orifice/Grate (Weir Controls fps)

33 Type II 24-hr 10-year Rainfall=.1" Page 23 Pond 4P: Rain Garden Hydrograph cfs Inflow Area=0.310 ac Peak Elev=144.0' Storage=1, cf Inflow Outflow Discarded Primary Flow (cfs) 1 0. cfs 0.2 cfs 0.0 cfs Time (hours)

34 Type II 24-hr 2-year Rainfall=.33" Page 24 Time span= hrs, dt=0.0 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment PD1: Drainage Area #1 Subcatchment PD2A: Roof Area Subcatchment PD2B: Developed Area Runoff Area=2.10 ac 11.1% Impervious Runoff Depth>3." Flow Length=10' Tc=41. min CN=1 Runoff=.9 cfs 0.1 af Runoff Area=0.40 ac % Impervious Runoff Depth>." Tc=.0 min CN=9 Runoff=.4 cfs 0.29 af Runoff Area=0.310 ac 4.39% Impervious Runoff Depth>4.3" Flow Length=14' Tc=. min CN= Runoff=2.31 cfs af Pond 1P: Detention System Peak Elev=13.3' Storage=,09 cf Inflow=.4 cfs af Discarded=0.1 cfs 0.13 af Primary=3. cfs 0.1 af Outflow=3. cfs 0.31 af Pond 2P: Design Point 1 Inflow=9.3 cfs 1.00 af Primary=9.3 cfs 1.00 af Pond 4P: Rain Garden Peak Elev=144.1' Storage=1,9 cf Inflow=2.31 cfs af Discarded=0.0 cfs af Primary=2.00 cfs 0.03 af Outflow=2.0 cfs 0.04 af Total Runoff Area = 3.0 ac Runoff Volume = 1.2 af Average Runoff Depth = 4.22" 9.% Pervious = 2.0 ac 30.33% Impervious = ac

35 Type II 24-hr 2-year Rainfall=.33" Page 2 Summary for Subcatchment PD1: Drainage Area #1 Runoff = hrs, Volume= 0.1 af, Depth> 3." Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 2-year Rainfall=.33" Area (ac) CN Description * Paved parking, HSG D EXIST Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall con2 Woodland Kv=.0 fps Shallow Concentrated Flow, shall to DP1 Woodland Kv=.0 fps Total Subcatchment PD1: Drainage Area #1 Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 2-year Rainfall=.33" Runoff Area=2.10 ac Runoff Volume=0.1 af Runoff Depth>3." Flow Length=10' Tc=41. min CN= Time (hours)

36 Type II 24-hr 2-year Rainfall=.33" Page 2 Summary for Subcatchment PD2A: Roof Area Runoff = hrs, Volume= 0.29 af, Depth>." Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 2-year Rainfall=.33" Area (ac) CN Description * Roofs, HSG D NEW ROOF % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs).0 Direct Entry, Subcatchment PD2A: Roof Area Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 2-year Rainfall=.33" Runoff Area=0.40 ac Runoff Volume=0.29 af Runoff Depth>." Tc=.0 min CN= Time (hours)

37 Type II 24-hr 2-year Rainfall=.33" Page 2 Summary for Subcatchment PD2B: Developed Area Runoff = hrs, Volume= af, Depth> 4.3" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 2-year Rainfall=.33" Area (ac) CN Description * Paved parking, HSG D NEW Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall conc Paved Kv= 20.3 fps Shallow Concentrated Flow, Short Grass Pasture Kv=.0 fps. 14 Total Subcatchment PD2B: Developed Area Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 2-year Rainfall=.33" Runoff Area=0.310 ac Runoff Volume=0.120 af Runoff Depth>4.3" Flow Length=14' Tc=. min CN= Time (hours)

38 Type II 24-hr 2-year Rainfall=.33" Page 2 Summary for Pond 1P: Detention System Inflow Area = 0.90 ac, 3.1% Impervious, Inflow Depth > 4.20" for 2-year event Inflow = hrs, Volume= af Outflow = hrs, Volume= 0.31 af, Atten= 34%, Lag=.4 min Discarded = hrs, Volume= 0.13 af Primary = hrs, Volume= 0.1 af Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Peak Elev= 12.0 hrs Surf.Area= 2,99 sf Storage=,09 cf Plug-Flow detention time=.1 min calculated for 0.31 af (9% of inflow) Center-of-Mass det. time= 4.9 min ( ) Volume Invert Avail.Storage Storage Description # ' 3,0 cf 3.0" Round CMP_Round 3" x Inside #2 L=.0' #2 13.0' 2,13 cf Custom Stage Data (Prismatic)Listed below (Recalc) 10,0 cf Overall - 3,0 cf Embedded =,2 cf x 30.0% Voids # ' 393 cf.00'd x.00'h Vertical Cone/Cylinder x 4,10 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , ,20 10,0 10,0 Device Routing Invert Outlet Devices #1 Primary 13.0' 1.0" Round Culvert L= 0.0' RCP, sq.cut end projecting, Ke= 0.00 Inlet / Outlet Invert= 13.0' / 13.02' S= '/' Cc= n= Corrugated PE, smooth interior, Flow Area= 1. sf #2 Device '.0" Vert. Orifice/Grate C= 0.00 #3 Device 1 13.'.0" Vert. Orifice/Grate C= 0.00 #4 Device '.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) # Discarded 13.0' 1.00 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 131.0' Discarded OutFlow Max= hrs HW=13.0' (Free Discharge) =Exfiltration ( Controls 0.1 cfs) Primary OutFlow Max= hrs HW=13.0' (Free Discharge) 1=Culvert (Passes 3.4 cfs of. cfs potential flow) 2=Orifice/Grate (Orifice Controls 0. fps) 3=Orifice/Grate (Orifice Controls fps) 4=Sharp-Crested Rectangular Weir (Weir Controls fps)

39 Type II 24-hr 2-year Rainfall=.33" Page 29 Pond 1P: Detention System Hydrograph.4 cfs 3. cfs Inflow Area=0.90 ac Peak Elev=13.3' Storage=,09 cf Inflow Outflow Discarded Primary Flow (cfs) cfs cfs Time (hours)

40 Type II 24-hr 2-year Rainfall=.33" Page 30 Summary for Pond 2P: Design Point 1 Inflow Area = 3.0 ac, 30.33% Impervious, Inflow Depth > 3.44" for 2-year event Inflow = hrs, Volume= 1.00 af Primary = hrs, Volume= 1.00 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Pond 2P: Design Point 1 Hydrograph cfs 9.3 cfs Inflow Area=3.0 ac Inflow Primary Flow (cfs) Time (hours)

41 Type II 24-hr 2-year Rainfall=.33" Page 31 Summary for Pond 4P: Rain Garden Inflow Area = ac, 4.39% Impervious, Inflow Depth > 4.3" for 2-year event Inflow = hrs, Volume= af Outflow = hrs, Volume= 0.04 af, Atten= 11%, Lag= 4.2 min Discarded = hrs, Volume= af Primary = hrs, Volume= 0.03 af Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Peak Elev= 12.0 hrs Surf.Area= 1,03 sf Storage= 1,9 cf Plug-Flow detention time= 11. min calculated for 0.04 af (0% of inflow) Center-of-Mass det. time= 0. min ( ) Volume Invert Avail.Storage Storage Description # ' 1, cf Custom Stage Data (Prismatic)Listed below (Recalc) Inside #2 # ' 4 cf Custom Stage Data (Prismatic)Listed below (Recalc) 4,0 cf Overall - 1, cf Embedded = 3,119 cf x 1.0% Voids 2,0 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , ,00 2 1, Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) ,41 4, ,00 2 4,0 Device Routing Invert Outlet Devices #1 Primary ' 24.0" x 3.0" Horiz. Orifice/Grate C= 0.00 Limited to weir flow at low heads #2 Discarded 139.0' 1.00 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = ' Discarded OutFlow Max= hrs HW=144.14' (Free Discharge) 2=Exfiltration ( Controls 0.0 cfs) Primary OutFlow Max= hrs HW=144.14' (Free Discharge) 1=Orifice/Grate (Weir Controls fps)

42 Type II 24-hr 2-year Rainfall=.33" Page 32 Pond 4P: Rain Garden Hydrograph cfs 2.31 cfs 2.0 cfs Inflow Area=0.310 ac Peak Elev=144.1' Storage=1,9 cf Inflow Outflow Discarded Primary Flow (cfs) cfs Time (hours)

43 Type II 24-hr 100-year Rainfall=.1" Page 33 Time span= hrs, dt=0.0 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment PD1: Drainage Area #1 Subcatchment PD2A: Roof Area Subcatchment PD2B: Developed Area Runoff Area=2.10 ac 11.1% Impervious Runoff Depth>.4" Flow Length=10' Tc=41. min CN=1 Runoff=11.02 cfs af Runoff Area=0.40 ac % Impervious Runoff Depth>.20" Tc=.0 min CN=9 Runoff=.3 cfs 0.34 af Runoff Area=0.310 ac 4.39% Impervious Runoff Depth>.29" Flow Length=14' Tc=. min CN= Runoff=3.0 cfs 0.13 af Pond 1P: Detention System Peak Elev=13.9' Storage=,92 cf Inflow=9. cfs 0.4 af Discarded=0.1 cfs 0.14 af Primary=9.29 cfs 0.2 af Outflow=9.4 cfs af Pond 2P: Design Point 1 Inflow=13.3 cfs 1.1 af Primary=13.3 cfs 1.1 af Pond 4P: Rain Garden Peak Elev=144.22' Storage=2,023 cf Inflow=3.0 cfs 0.13 af Discarded=0.0 cfs 0.03 af Primary=3.34 cfs 0.01 af Outflow=3.39 cfs af Total Runoff Area = 3.0 ac Runoff Volume = 1. af Average Runoff Depth =.3" 9.% Pervious = 2.0 ac 30.33% Impervious = ac

44 Type II 24-hr 100-year Rainfall=.1" Page 34 Summary for Subcatchment PD1: Drainage Area #1 Runoff = hrs, Volume= af, Depth>.4" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 100-year Rainfall=.1" Area (ac) CN Description * Paved parking, HSG D EXIST Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall con2 Woodland Kv=.0 fps Shallow Concentrated Flow, shall to DP1 Woodland Kv=.0 fps Total Subcatchment PD1: Drainage Area #1 Hydrograph 12 Runoff Flow (cfs) cfs Type II 24-hr 100-year Rainfall=.1" Runoff Area=2.10 ac Runoff Volume=1.231 af Runoff Depth>.4" Flow Length=10' Tc=41. min CN= Time (hours)

45 Type II 24-hr 100-year Rainfall=.1" Page 3 Summary for Subcatchment PD2A: Roof Area Runoff = hrs, Volume= 0.34 af, Depth>.20" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 100-year Rainfall=.1" Area (ac) CN Description * Roofs, HSG D NEW ROOF % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs).0 Direct Entry, Subcatchment PD2A: Roof Area Hydrograph Flow (cfs) cfs Type II 24-hr 100-year Rainfall=.1" Runoff Area=0.40 ac Runoff Volume=0.34 af Runoff Depth>.20" Tc=.0 min CN=9 Runoff Time (hours)

46 Type II 24-hr 100-year Rainfall=.1" Page 3 Summary for Subcatchment PD2B: Developed Area Runoff = hrs, Volume= 0.13 af, Depth>.29" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= hrs, dt= 0.0 hrs Type II 24-hr 100-year Rainfall=.1" Area (ac) CN Description * Paved parking, HSG D NEW Woods, Fair, HSG D >% Grass cover, Good, HSG D Weighted Average % Pervious Area % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Sheet Flow, Sheet Flow Woods: Light underbrush n= P2= 3.2" Shallow Concentrated Flow, shall conc Paved Kv= 20.3 fps Shallow Concentrated Flow, Short Grass Pasture Kv=.0 fps. 14 Total Subcatchment PD2B: Developed Area Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 100-year Rainfall=.1" Runoff Area=0.310 ac Runoff Volume=0.13 af Runoff Depth>.29" Flow Length=14' Tc=. min CN= Time (hours)

47 Type II 24-hr 100-year Rainfall=.1" Page 3 Summary for Pond 1P: Detention System Inflow Area = 0.90 ac, 3.1% Impervious, Inflow Depth >.4" for 100-year event Inflow = hrs, Volume= 0.4 af Outflow = hrs, Volume= af, Atten= 3%, Lag= 1. min Discarded = hrs, Volume= 0.14 af Primary = hrs, Volume= 0.2 af Routing by Stor-Ind method, Time Span= hrs, dt= 0.0 hrs Peak Elev= hrs Surf.Area= 2,99 sf Storage=,92 cf Plug-Flow detention time=.3 min calculated for af (94% of inflow) Center-of-Mass det. time= 3.3 min ( ) Volume Invert Avail.Storage Storage Description # ' 3,0 cf 3.0" Round CMP_Round 3" x Inside #2 L=.0' #2 13.0' 2,13 cf Custom Stage Data (Prismatic)Listed below (Recalc) 10,0 cf Overall - 3,0 cf Embedded =,2 cf x 30.0% Voids # ' 393 cf.00'd x.00'h Vertical Cone/Cylinder x 4,10 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) , ,20 10,0 10,0 Device Routing Invert Outlet Devices #1 Primary 13.0' 1.0" Round Culvert L= 0.0' RCP, sq.cut end projecting, Ke= 0.00 Inlet / Outlet Invert= 13.0' / 13.02' S= '/' Cc= n= Corrugated PE, smooth interior, Flow Area= 1. sf #2 Device '.0" Vert. Orifice/Grate C= 0.00 #3 Device 1 13.'.0" Vert. Orifice/Grate C= 0.00 #4 Device '.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) # Discarded 13.0' 1.00 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 131.0' Discarded OutFlow Max= hrs HW=13.94' (Free Discharge) =Exfiltration ( Controls 0.1 cfs) Primary OutFlow Max= hrs HW=13.94' (Free Discharge) 1=Culvert (Passes. cfs of 9.2 cfs potential flow) 2=Orifice/Grate (Orifice Controls 0.9 fps) 3=Orifice/Grate (Orifice Controls 1.3 fps) 4=Sharp-Crested Rectangular Weir (Weir Controls fps)