Drainage and Detention Report. for. Charity Auto Sales. located at: East 116 th Street North Collinsville, OK Revised August 22, 2016

Transcription

1 Drainage and Detention Report for Charity Auto Sales located at: 9 East 6 th Street North Collinsville, OK 742 Revised August 22, 26 Olsson Associates, Inc. 9 N. Birch Street, Suite 2 Owasso, OK 74 (98) Fax (98) Oklahoma Certificate of Authorization No. 2483

2 LETTER AGREEMENT FOR PROFESSIONAL SERVICES City of Owasso, Public Works Department 3 W. 2 nd Avenue Owasso, OK 74 8/2/26 Re: Submittal of Revised Drainage and Detention Report Charity Auto Sales 9 E. 6 th Street N. On behalf of Charity Auto Sales, Impact Engineering and Planning, PLC hereby submits this revised drainage report for permitting of the proposed facility located at 9 E. 6 th Street N. in Owasso, OK. It is the intent of Charity Auto Sales to construct a new facility on the property for use as a used car dealership. It is our goal to show that the proposed improvements will not adversely affect the stormwater flows in the Blackjack Creek basin and the Brookfield Crossing subdivision. We have evaluated the existing and proposed system for the -, 2-, -, -, 2-, -, - and -year storm events. It was our intent to model the existing system using methodologies acceptable to the City of Owasso. The stormwater flows are at or below the existing conditions for the -, -, 2-, -, - and -year events. The proposed flows do exceed the existing flows for the - and 2-year events. We would like to request a variance from the City of Owasso Stormwater Drainage Criteria to allow for the increases in the low instance events since no downstream impacts would be evident. Please feel free to call with any questions or comments. Sincerely, Kevin Vanover, P.E., LEED AP I hereby certify that this drainage and detention report was prepared by me in accordance with local drainage design criteria. Kevin Vanover, P.E. Registered Professional Engineer State of Oklahoma No Page of

3 Index Cover Letter... General Location and Description... 3 Drainage Design Criteria... Detention Summary... 8 Project Hydraulic Summary... 9 References... Appendices Proposed Grading Plans... 3 Existing Drainage Area Map (Fold-out)... 4 Existing Hydrology/Hydraulic Data... Area Map (Fold-out) Proposed Hydrology/Hydraulic Data Tables Table Detention Summary... 8 Table 2 Runoff Summary (Combined Flows at Existing 36 Pipe)... Table 3 Runoff Summary (Flows on to Lots 36 and 37, Block 2)... 2

4 General Location and Description Location The legal description of the project site is: A Parcel of land commencing at a point in the southwest corner of Section, Township 2 North, Range 4 East, Tulsa County, State of Oklahoma; thence N E a distance of 88. feet to the Point of Beginning; thence N E a distance of 37. feet; thence N 8 4 W a distance of 22. feet; thence S W a distance of 37. feet; thence S 8 4 E a distance of 22. feet to the point of beginning. Less the south 6. feet. Said Parcel containing.9 Acres (22,6. S.F.) more or less. Description of Property The proposed Charity Auto Sales sits on approximately.2 acres of land 82 feet east of N. Garnett Road on E. 6 th Street N. on the north side of 6th in the City of Owasso, OK. The site is bordered on the north and east by a residential subdivision (Brookfield Crossing) on the west by Agriculturally zoned undeveloped land (Owasso Land Use Masterplan identifies as Commercial) and on the south by an arterial road (E. 6 th Street N). The site drains to the north and west into an open cut ditch that runs to the west then to the north into a 36 pipe that directs the stormwater flow to the stormwater detention facility for Brookfield Crossing. The current topography of the site slopes from the southeast to the northwest. The grades are gradual (% to 3% maximum). Stormwater Detention Objects Watershed: Detention: The Charity Auto Sales project lies within the Blackjack Creek watershed and will require facilities to regulate the stormwater runoff from the site to mitigate the downstream impacts to the Blackjack Creek basin. The overall drainage patterns will remain unchanged. It is the intent of the design to mitigate the impacts of the increased stormwater flows using a parking lot detention facility. The design of the detention facility is detailed in the construction plans included in the appendix of this report. The pond is controlled using a series of 3

5 curb openings along with an extended curb measuring -7 /4 at its tallest. The top of the curb is set as a broad-crested weir with an elevation of 698.8, containing the stormwater storage volume within the proposed parking lot. The detention basin provides storage and a control structure slowing the rate of flow through the facility off-setting the increased flows created by the site development for the all storm events. 4

6 Drainage Design Criteria Regulations: Owasso Stormwater Drainage Criteria methods approved and recommended by local design criteria were applied in the hydrologic and hydraulic design of the Charity Auto Sales project drainage facilities. Hydrologic Methodology: The SCS hydrologic method requires basic data similar to the Rational Method: drainage area, a runoff factor, time of concentration, and rainfall. However, the SCS approach is more sophisticated in that it also considers the time distribution of the rainfall, the initial rainfall losses due to interception and depression storage, and an infiltration rate that decreases during the course of a storm. A typical application of the SCS method includes the following basic steps:. Determination of curve numbers that represent different land uses within the drainage area; 2. Calculation of time of concentration to the study point; 3. Use of the SCS Type II rainfall distribution in this area (per Owasso Drainage Design Criteria Section.2.F); and 4. Use of the unit hydrograph approach to develop the hydrograph of direct runoff from the drainage basin. The SCS method can be used for both the estimation of stormwater runoff peak rates and the generation of hydrographs for the routing of stormwater flows. The SCS method can be used for most design applications, including storage facilities and outlet structures, storm drain systems, culverts, small drainage ditches and open channels, and energy dissipaters. The principal physical watershed characteristics affecting the relationship between rainfall and runoff are land use, land treatment, soil types, and land slope. The SCS method uses a combination of soil conditions and land uses (ground cover) to assign a runoff factor to an area. These runoff factors, called runoff curve numbers (CN), indicate the runoff potential of an area. The higher the CN, the higher the runoff potential. Soil properties influence the relationship between runoff and rainfall since soils have differing rates of infiltration. Based on infiltration rates, the SCS has divided soils into four hydrologic soil groups (HSG). Group A Soils having a low runoff potential due to high infiltration rates. These soils consist primarily of deep, well-drained sands and gravels.

7 Group B Soils having a moderately low runoff potential due to moderate infiltration rates. These soils consist primarily of moderately deep to deep, moderately well to well drained soils with moderately fine to moderately coarse textures. Group C Soils having a moderately high runoff potential due to slow infiltration rates. These soils consist primarily of soils in which a layer exists near the surface that impedes the downward movement of water or soils with moderately fine to fine texture. Group D Soils having a high runoff potential due to very slow infiltration rates. These soils consist primarily of clays with high swelling potential, soils with permanently high water tables, soils with a claypan or clay layer at or near the surface, and shallow soils over nearly impervious parent material. Data obtained from the soil borings performed on the site and from the U.S. Department of Agriculture, Natural Resources Conservation Service, Web Soil Survey site, indicated that the soil group to be used for this project is Group C. The corresponding Curve Numbers are shown in tabular form for each drainage area on the Existing and Area Maps. The Rainfall used for the SCS method was derived directly from the City of Owasso Engineering Design Criteria (Section 4.2) is based on a storm event that has a Type II time distribution. This distribution is used to distribute the 24-hour volume of rainfall for the different storm frequencies. Detention Discharge and Storage Calculation Method (when required): The Dynamic-Storage-Indication method was the technique used for sequential pond routing due to the presence of a dynamic tailwater at the pond s discharge. The Dynamic-Storage-Indications methods uses the same calculations as the static Storage-Indication method, except that the stagedischarge and storage-indication curves are re-evaluated at each time step, based on the current elevation of any downstream nodes. This allows the routing to respond to ongoing tailwater changes, rather than assuming static tailwater conditions. A simplified description of this procedure follows. ) The pond's stage-discharge relationship is calculated based on the specified outlet devices. This curve typically covers the entire elevation range over which storage and/or outlet devices have been specified. 2) Using the specified storage information, a stage-storage relationship is determined over the same elevation range. 6

8 3) The stage-discharge and stage-storage curves are used to create a storage-indication curve, defined by the equation: where SI = S dt O 2 SI=Storage Indication value S=Pond Storage O=Pond Outflow dt=time increment 4) Routing is performed using the specified time span and time increment. At each point in time, a storage-indication value is calculated based on the equation: O I+I2 SI = S - -- dt dt 2 2 where S=Storage at start of time step O=Outflow at start of time step I/I2=Inflow at start/end of time step ) The original storage-indication curve is consulted to determine the elevation that corresponds to the new storage-indication value. 6) Using the new elevation, the stage-storage and stage-discharge curves are consulted to determine the new storage and discharge values. 7) This process is repeated for all points in the inflow hydrograph. If the pond has multiple outlets, the routing is performed based on the total discharge, and is then split according to the characteristics of the individual outlets. Design Storm Recurrence Intervals 24-hour design storms were developed for the -, 2-, -, -, 2-, -, - and -year storms. The -year flood is the standard for design of most drainage structures. 7

9 Detention Summary The proposed development will have a detention facility working to maintain the pre-developed flows. The pond detailed is located in the parking lot on the west side of the project. Table, shown below, summarizes the developed flow rates from the proposed detention facility. As shown, the proposed detention facility controls flow from the site for the -, 2-, -, -, 2-, -, - and -year events. The hydrographs for each sub basin (-year event only) are included in the appendix of this report for both the existing and the proposed conditions. Table. Detention Summary (Parking Lot Detention Facility) Storm Event Inflow (Q) Outflow (Q) Max. Depth* W.S. Elev. -year.63 cfs.84 cfs.93 ft year 2.3 cfs.3 cfs.6 ft year 3.6 cfs.39 cfs.26 ft year 3.4 cfs.63 cfs.3 ft year 4.28 cfs 2. cfs.46 ft year 4.79 cfs 2.2 cfs.3 ft year.42 cfs 2.6 cfs.6 ft year 6.67 cfs.42 cfs.68 ft * Maximum Depth of detained flow occurs at curb opening. Bottom elevation of curb opening is

10 Project Hydraulic Summary The pre-developed site consists of a two (2) basins. Existing Drainage Areas E and Area E2 (as shown on the Existing Drainage Map included in the appendix) are the existing conditions of the development site. Area E drains the western portion of the existing site to the north and west and into a system that directs the flow into the Brookfield Crossing detention facility. Area E2 consists of the eastern portion of the site that flows overland to lots 36 and 37, Block 2 of Brookfield Crossing. The existing flow hydrographs are included with the Existing Drainage Data in Appendix A. The SCS model indicates that the peak flow for a -year storm in Area E of.66 cfs occurring at 2. hours (723. minutes) during the modeled Type II 24-hour storm. This flow will establish the baseline to be used in comparing the effects of the pre- and post-development impacts. The proposed system consists of three basins as shown on the Map included in the appendix. Basin P drains to the proposed detention facility located on the west side of the proposed development. The discharge from the detention facility combines with the discharge from area P2 in a ditch to the south of the southern boundary of Block 2 of the Brookfield Crossing subdivision. The existing 36 stormwater pipe is located in the southwest corner of Lot 34, Block 2. Once it enters the Brookfield Crossing system it is carried directly into a detention facility. The detention facility discharges into an unnamed tributary of Blackjack Creek. Blackjack Creek carries the flow north to Horsepen Creek and eventually into the Caney River near 6 st Street N. and U.S. 69. Drainage Basin P2 consists of the street yard along 6 th Street along with the undeveloped land to the west of the project site. The area analyzed drains from a high point in the right-of-way to the west and then north where it joins the discharge from area P at the Brookfield Crossing inlet pipe. Drainage Basin P3 consists of the slim section of the site that consists of back yards to the east and the northern yard of the site along with the northern half of the proposed building. This area is mostly maintained grasses, as well as the northern portion of the proposed building, and it directed to the northwest and into the yards to the north of the project site. This drainage basin is a remnant of the existing area E2. The majority of area E2 was diverted to the detention basin. Drainage Basins P and P2 were combined at the northwest corner of the site for the purpose of this analysis. The Data is included in Appendix A. The SCS model indicates that the peak flow for a -year storm of 6.27 cfs occurs at.9 hours (77. minutes) during the modeled Type II 24-hour storm. When the reduction of stormwater flows that were directed to the lots north of the proposed facility during the existing conditions are taken into account, since they combine in the street directly north of the project location, a net reduction of all storm events with the exception of the - and 2- year events occurs. 9

11 The hydrographs for each sub basin are included in the appendix of this report for both the existing and the proposed conditions and the drainage data is shown on the following tables. Table 2. Runoff Summary (Combined Flows at Existing 36 Pipe) Storm Existing Site Proposed Site Existing Proposed Event Outflow Outflow Velocity* Velocity* -year.97 cfs.4 cfs 2. fps 2.6 fps 2-year. cfs.97 cfs 2.3 fps 2.4 fps -year 2.62 cfs 3. cfs 2.73 fps 2.7 fps -year 3.22 cfs 3.72 cfs 2.9 fps 2.89 fps 2-year 4.7 cfs 4.69 cfs 3. fps 3.8 fps -year 4.83 cfs.39 cfs 3.3 fps 3.9 fps -year.66 cfs 6.27 cfs 3.46 fps 3.33 fps -year 7.32 cfs 8.7 cfs 3.7 fps 3.6 fps * The existing and proposed velocities are determined in the ditch along the northwest corner of the proposed site after the point of the combined flows. Table 3. Runoff Summary (Flows on to Lots 36 and 37, Block 2) Storm Existing Site Proposed Site Existing Proposed Event Outflow Outflow Velocity Velocity -year.49 cfs.26 cfs 2.6 fps.88 fps 2-year.78 cfs.38 cfs 2.6 fps.88 fps -year.39 cfs.64 cfs 2.6 fps.88 fps -year.72 cfs.77 cfs 2.6 fps.88 fps 2-year 2.2 cfs.98 cfs 2.6 fps.88 fps -year 2.62 cfs.3 cfs 2.6 fps.88 fps -year 3.9 cfs.32 cfs 2.6 fps.88 fps -year 4.2 cfs.68 cfs 2.6 fps.88 fps

12 References. HydroCAD Software Solutions, LLC. Internet web site ( / Program About information. Version 9., Copyright U.S. Department of Agriculture, Natural Resources Conservation Service, Web Soil Survey internet web site ( 3. City of Owasso Engineering Design Criteria, May 8, 2

13 Appendices 2

14 R N LEGEND Know what's 8/2/26 % CONSTRUCTION DOCUMENTS drawn by: KGV checked by: KGV approved by: QA/QC by: project no.: drawing no.: date: //26 SHEET C-2 GRADING PLAN CHARITY AUTO SALES NEW FACILITY REV. NO. DATE REVISIONS DESCRIPTION 8/2/26 R 9 EAST 6TH STREET NORTH OWASSO, OK REVISIONS 9 N. Birch St., Suite 2 Owasso, OK 74 TEL FAX

15 Know what's R E HOGWIRE FENCE 6' WOOD FENCE E HOME WOOD -STORY E2 E2 6' WOOD FENCE N LEGEND E 8/2/26 % CONSTRUCTION DOCUMENTS drawn by: KGV checked by: KGV approved by: QA/QC by: project no.: drawing no.: date: //26 SHEET C-3 EXISTING DRAINAGE PLAN CHARITY AUTO SALES NEW FACILITY REV. NO. DATE REVISIONS DESCRIPTION 8/2/26 R 9 EAST 6TH STREET NORTH OWASSO, OK REVISIONS 9 N. Birch St., Suite 2 Owasso, OK 74 TEL FAX

16 7S 8S Area E Area E2 9R (new Reach) Subcat Reach Pond Link Drainage Diagram for Existing Drainage, Printed 8/24/26

17 Existing Drainage Existing Data - August 26 Printed 8/24/26 Page 2 Area (acres) CN.2 74 (7S, 8S) (7S, 8S) Description (subcatchment-numbers) Area Listing (all nodes)

18 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=3." Printed 8/24/26 Page 3 Time span=.-2. hrs, dt=. hrs, 3 points Runoff by SCS TR-2 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Area E Subcatchment 8S: Area E2 Reach 9R: (new Reach) Runoff Area=3,33 sf 7.79% Impervious Runoff Depth>.9" Flow Length=42' Tc=3. min CN=76 Runoff=.97 cfs. af Runoff Area=6,8 sf.9% Impervious Runoff Depth>.82" Flow Length=272' Tc=. min CN=74 Runoff=.49 cfs.2 af Avg. Flow Depth=.7' Max Vel=2. fps Inflow=.97 cfs. af n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Outflow=.94 cfs. af

19 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=3." Printed 8/24/26 Page 4 Summary for Subcatchment 7S: Area E Runoff = hrs, Volume=. af, Depth>.9" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr -Year Rainfall=3." Area (sf) CN Description * 2, * 28, ,33 76 Weighted Average 28, % Pervious Area 2, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps Total Subcatchment 7S: Area E Hydrograph Runoff Flow (cfs).97 cfs Type II 24-hr -Year Rainfall=3." Runoff Area=3,33 sf Runoff Volume=. af Runoff Depth>.9" Flow Length=42' Tc=3. min CN= Time (hours)

20 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=3." Printed 8/24/26 Page Summary for Subcatchment 8S: Area E2 Runoff = hrs, Volume=.2 af, Depth>.82" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr -Year Rainfall=3." Area (sf) CN Description * *, ,8 74 Weighted Average, % Pervious Area 37.9% Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps. 272 Total Subcatchment 8S: Area E2 Hydrograph Runoff Flow (cfs) cfs Type II 24-hr -Year Rainfall=3." Runoff Area=6,8 sf Runoff Volume=.2 af Runoff Depth>.82" Flow Length=272' Tc=. min CN= Time (hours)

21 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=3." Printed 8/24/26 Page 6 Summary for Reach 9R: (new Reach) Inflow Area =.79 ac, 7.79% Impervious, Inflow Depth >.9" for -Year event Inflow = hrs, Volume=. af Outflow = hrs, Volume=. af, Atten= 4%, Lag= 2.4 min Routing by Stor-Ind+Trans method, Time Span=.-2. hrs, dt=. hrs Max. Velocity= 2. fps, Min. Travel Time=.3 min Avg. Velocity =.79 fps, Avg. Travel Time= 3.3 min Peak Storage= hrs Average Depth at Peak Storage=.7' Bank-Full Depth=.', Capacity at Bank-Full= 42.8 cfs.' x.' deep Parabolic Channel, n=.24 Length= 7.' Slope=.9 '/' Inlet Invert= 696.', Outlet Invert= 693.' Reach 9R: (new Reach) Hydrograph Flow (cfs).97 cfs.94 cfs Inflow Area=.79 ac Avg. Flow Depth=.7' Max Vel=2. fps n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Inflow Outflow Time (hours)

22 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=3." Printed 8/24/26 Page 7 Reach 9R: (new Reach) Stage-Discharge Primary Depth 2 2 Discharge (cfs) Reach 9R: (new Reach) Stage-Storage Storage Depth Storage (cubic-feet) 7 8 9,

23 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=3." Printed 8/24/26 Page 8 Stage-Discharge for Reach 9R: (new Reach) Velocity (ft/sec) Discharge (cfs) Velocity (ft/sec) Discharge (cfs)

24 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=3." Printed 8/24/26 Page 9 Stage-Area-Storage for Reach 9R: (new Reach) End-Area (sq-ft) Storage (cubic-feet) End-Area (sq-ft) Storage (cubic-feet) , , , ,47

25 Existing Drainage Existing Data - August 26 Type II 24-hr 2-Year Rainfall=3.7" Printed 8/24/26 Page Time span=.-2. hrs, dt=. hrs, 3 points Runoff by SCS TR-2 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Area E Subcatchment 8S: Area E2 Reach 9R: (new Reach) Runoff Area=3,33 sf 7.79% Impervious Runoff Depth>.4" Flow Length=42' Tc=3. min CN=76 Runoff=.2 cfs.84 af Runoff Area=6,8 sf.9% Impervious Runoff Depth>.28" Flow Length=272' Tc=. min CN=74 Runoff=.78 cfs.39 af Avg. Flow Depth=.2' Max Vel=2.3 fps Inflow=.2 cfs.84 af n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Outflow=.47 cfs.84 af

26 Existing Drainage Existing Data - August 26 Type II 24-hr 2-Year Rainfall=3.7" Printed 8/24/26 Page Summary for Subcatchment 7S: Area E Runoff =.2 2. hrs, Volume=.84 af, Depth>.4" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr 2-Year Rainfall=3.7" Area (sf) CN Description * 2, * 28, ,33 76 Weighted Average 28, % Pervious Area 2, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps Total Subcatchment 7S: Area E Hydrograph Runoff Flow (cfs).2 cfs Type II 24-hr 2-Year Rainfall=3.7" Runoff Area=3,33 sf Runoff Volume=.84 af Runoff Depth>.4" Flow Length=42' Tc=3. min CN= Time (hours)

27 Existing Drainage Existing Data - August 26 Type II 24-hr 2-Year Rainfall=3.7" Printed 8/24/26 Page 2 Summary for Subcatchment 8S: Area E2 Runoff = hrs, Volume=.39 af, Depth>.28" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr 2-Year Rainfall=3.7" Area (sf) CN Description * *, ,8 74 Weighted Average, % Pervious Area 37.9% Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps. 272 Total Subcatchment 8S: Area E2 Hydrograph Flow (cfs) cfs Type II 24-hr 2-Year Rainfall=3.7" Runoff Area=6,8 sf Runoff Volume=.39 af Runoff Depth>.28" Flow Length=272' Tc=. min CN=74 Runoff Time (hours)

28 Existing Drainage Existing Data - August 26 Type II 24-hr 2-Year Rainfall=3.7" Printed 8/24/26 Page 3 Summary for Reach 9R: (new Reach) Inflow Area =.79 ac, 7.79% Impervious, Inflow Depth >.4" for 2-Year event Inflow =.2 2. hrs, Volume=.84 af Outflow = hrs, Volume=.84 af, Atten= 4%, Lag= 2. min Routing by Stor-Ind+Trans method, Time Span=.-2. hrs, dt=. hrs Max. Velocity= 2.3 fps, Min. Travel Time=. min Avg. Velocity =.8 fps, Avg. Travel Time= 3. min Peak Storage= hrs Average Depth at Peak Storage=.2' Bank-Full Depth=.', Capacity at Bank-Full= 42.8 cfs.' x.' deep Parabolic Channel, n=.24 Length= 7.' Slope=.9 '/' Inlet Invert= 696.', Outlet Invert= 693.' Reach 9R: (new Reach) Hydrograph Flow (cfs).2 cfs.47 cfs Inflow Area=.79 ac Avg. Flow Depth=.2' Max Vel=2.3 fps n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Inflow Outflow Time (hours)

29 Existing Drainage Existing Data - August 26 Type II 24-hr 2-Year Rainfall=3.7" Printed 8/24/26 Page 4 Reach 9R: (new Reach) Stage-Discharge Primary Depth 2 2 Discharge (cfs) Reach 9R: (new Reach) Stage-Storage Storage Depth Storage (cubic-feet) 7 8 9,

30 Existing Drainage Existing Data - August 26 Type II 24-hr 2-Year Rainfall=3.7" Printed 8/24/26 Page Stage-Discharge for Reach 9R: (new Reach) Velocity (ft/sec) Discharge (cfs) Velocity (ft/sec) Discharge (cfs)

31 Existing Drainage Existing Data - August 26 Type II 24-hr 2-Year Rainfall=3.7" Printed 8/24/26 Page 6 Stage-Area-Storage for Reach 9R: (new Reach) End-Area (sq-ft) Storage (cubic-feet) End-Area (sq-ft) Storage (cubic-feet) , , , ,47

32 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=." Printed 8/24/26 Page 7 Time span=.-2. hrs, dt=. hrs, 3 points Runoff by SCS TR-2 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Area E Subcatchment 8S: Area E2 Reach 9R: (new Reach) Runoff Area=3,33 sf 7.79% Impervious Runoff Depth>2.4" Flow Length=42' Tc=3. min CN=76 Runoff=2.63 cfs.46 af Runoff Area=6,8 sf.9% Impervious Runoff Depth>2.28" Flow Length=272' Tc=. min CN=74 Runoff=.39 cfs.7 af Avg. Flow Depth=.27' Max Vel=2.73 fps Inflow=2.63 cfs.46 af n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Outflow=2.4 cfs.46 af

33 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=." Printed 8/24/26 Page 8 Summary for Subcatchment 7S: Area E Runoff = hrs, Volume=.46 af, Depth> 2.4" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr -Year Rainfall=." Area (sf) CN Description * 2, * 28, ,33 76 Weighted Average 28, % Pervious Area 2, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps Total Subcatchment 7S: Area E Hydrograph Runoff Flow (cfs) cfs Type II 24-hr -Year Rainfall=." Runoff Area=3,33 sf Runoff Volume=.46 af Runoff Depth>2.4" Flow Length=42' Tc=3. min CN= Time (hours)

34 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=." Printed 8/24/26 Page 9 Summary for Subcatchment 8S: Area E2 Runoff = hrs, Volume=.7 af, Depth> 2.28" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr -Year Rainfall=." Area (sf) CN Description * *, ,8 74 Weighted Average, % Pervious Area 37.9% Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps. 272 Total Subcatchment 8S: Area E2 Hydrograph Runoff Flow (cfs).39 cfs Type II 24-hr -Year Rainfall=." Runoff Area=6,8 sf Runoff Volume=.7 af Runoff Depth>2.28" Flow Length=272' Tc=. min CN= Time (hours)

35 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=." Printed 8/24/26 Page 2 Summary for Reach 9R: (new Reach) Inflow Area =.79 ac, 7.79% Impervious, Inflow Depth > 2.4" for -Year event Inflow = hrs, Volume=.46 af Outflow = hrs, Volume=.46 af, Atten= 3%, Lag=.7 min Routing by Stor-Ind+Trans method, Time Span=.-2. hrs, dt=. hrs Max. Velocity= 2.73 fps, Min. Travel Time=. min Avg. Velocity =.94 fps, Avg. Travel Time= 2.8 min Peak Storage= 2.6 hrs Average Depth at Peak Storage=.27' Bank-Full Depth=.', Capacity at Bank-Full= 42.8 cfs.' x.' deep Parabolic Channel, n=.24 Length= 7.' Slope=.9 '/' Inlet Invert= 696.', Outlet Invert= 693.' Reach 9R: (new Reach) Hydrograph Flow (cfs) cfs 2.4 cfs Inflow Area=.79 ac Avg. Flow Depth=.27' Max Vel=2.73 fps n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Inflow Outflow Time (hours)

36 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=." Printed 8/24/26 Page 2 Reach 9R: (new Reach) Stage-Discharge Primary Depth 2 2 Discharge (cfs) Reach 9R: (new Reach) Stage-Storage Storage Depth Storage (cubic-feet) 7 8 9,

37 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=." Printed 8/24/26 Page 22 Stage-Discharge for Reach 9R: (new Reach) Velocity (ft/sec) Discharge (cfs) Velocity (ft/sec) Discharge (cfs)

38 Existing Drainage Existing Data - August 26 Type II 24-hr -Year Rainfall=." Printed 8/24/26 Page 23 Stage-Area-Storage for Reach 9R: (new Reach) End-Area (sq-ft) Storage (cubic-feet) End-Area (sq-ft) Storage (cubic-feet) , , , ,47

39 Existing Data - August 26 Existing Drainage Type II 24-hr -Year Rainfall=.88" Printed 8/24/26 Page 24 Time span=.-2. hrs, dt=. hrs, 3 points Runoff by SCS TR-2 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Area E Subcatchment 8S: Area E2 Reach 9R: (new Reach) Runoff Area=3,33 sf 7.79% Impervious Runoff Depth>3.2" Flow Length=42' Tc=3. min CN=76 Runoff=3.23 cfs.8 af Runoff Area=6,8 sf.9% Impervious Runoff Depth>2.84" Flow Length=272' Tc=. min CN=74 Runoff=.72 cfs.87 af Avg. Flow Depth=.3' Max Vel=2.9 fps Inflow=3.23 cfs.8 af n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Outflow=3.3 cfs.8 af

40 Existing Data - August 26 Existing Drainage Type II 24-hr -Year Rainfall=.88" Printed 8/24/26 Page 2 Summary for Subcatchment 7S: Area E Runoff = hrs, Volume=.8 af, Depth> 3.2" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr -Year Rainfall=.88" Area (sf) CN Description * 2, * 28, ,33 76 Weighted Average 28, % Pervious Area 2, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps Total Subcatchment 7S: Area E Hydrograph Runoff Flow (cfs) cfs Type II 24-hr -Year Rainfall=.88" Runoff Area=3,33 sf Runoff Volume=.8 af Runoff Depth>3.2" Flow Length=42' Tc=3. min CN= Time (hours)

41 Existing Data - August 26 Existing Drainage Type II 24-hr -Year Rainfall=.88" Printed 8/24/26 Page 26 Summary for Subcatchment 8S: Area E2 Runoff = hrs, Volume=.87 af, Depth> 2.84" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr -Year Rainfall=.88" Area (sf) CN Description * *, ,8 74 Weighted Average, % Pervious Area 37.9% Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps. 272 Total Subcatchment 8S: Area E2 Hydrograph Runoff Flow (cfs).72 cfs Type II 24-hr -Year Rainfall=.88" Runoff Area=6,8 sf Runoff Volume=.87 af Runoff Depth>2.84" Flow Length=272' Tc=. min CN= Time (hours)

42 Existing Data - August 26 Existing Drainage Type II 24-hr -Year Rainfall=.88" Printed 8/24/26 Page 27 Summary for Reach 9R: (new Reach) Inflow Area =.79 ac, 7.79% Impervious, Inflow Depth > 3.2" for -Year event Inflow = hrs, Volume=.8 af Outflow = hrs, Volume=.8 af, Atten= 3%, Lag=. min Routing by Stor-Ind+Trans method, Time Span=.-2. hrs, dt=. hrs Max. Velocity= 2.9 fps, Min. Travel Time=.9 min Avg. Velocity =.98 fps, Avg. Travel Time= 2.7 min Peak Storage= hrs Average Depth at Peak Storage=.3' Bank-Full Depth=.', Capacity at Bank-Full= 42.8 cfs.' x.' deep Parabolic Channel, n=.24 Length= 7.' Slope=.9 '/' Inlet Invert= 696.', Outlet Invert= 693.' Reach 9R: (new Reach) Hydrograph Flow (cfs) cfs 3.3 cfs Inflow Area=.79 ac Avg. Flow Depth=.3' Max Vel=2.9 fps n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Inflow Outflow Time (hours)

43 Existing Data - August 26 Existing Drainage Type II 24-hr -Year Rainfall=.88" Printed 8/24/26 Page 28 Reach 9R: (new Reach) Stage-Discharge Primary Depth 2 2 Discharge (cfs) Reach 9R: (new Reach) Stage-Storage Storage Depth Storage (cubic-feet) 7 8 9,

44 Existing Data - August 26 Existing Drainage Type II 24-hr -Year Rainfall=.88" Printed 8/24/26 Page 29 Stage-Discharge for Reach 9R: (new Reach) Velocity (ft/sec) Discharge (cfs) Velocity (ft/sec) Discharge (cfs)

45 Existing Data - August 26 Existing Drainage Type II 24-hr -Year Rainfall=.88" Printed 8/24/26 Page 3 Stage-Area-Storage for Reach 9R: (new Reach) End-Area (sq-ft) Storage (cubic-feet) End-Area (sq-ft) Storage (cubic-feet) , , , ,47

46 Existing Data - August 26 Existing Drainage Type II 24-hr 2-Year Rainfall=7." Printed 8/24/26 Page 3 Time span=.-2. hrs, dt=. hrs, 3 points Runoff by SCS TR-2 method, UH=SCS Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 7S: Area E Subcatchment 8S: Area E2 Reach 9R: (new Reach) Runoff Area=3,33 sf 7.79% Impervious Runoff Depth>3.9" Flow Length=42' Tc=3. min CN=76 Runoff=4.8 cfs.236 af Runoff Area=6,8 sf.9% Impervious Runoff Depth>3.74" Flow Length=272' Tc=. min CN=74 Runoff=2.2 cfs. af Avg. Flow Depth=.34' Max Vel=3.6 fps Inflow=4.8 cfs.236 af n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Outflow=4.6 cfs.236 af

47 Existing Data - August 26 Existing Drainage Type II 24-hr 2-Year Rainfall=7." Printed 8/24/26 Page 32 Summary for Subcatchment 7S: Area E Runoff = hrs, Volume=.236 af, Depth> 3.9" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr 2-Year Rainfall=7." Area (sf) CN Description * 2, * 28, ,33 76 Weighted Average 28, % Pervious Area 2, % Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps Total Subcatchment 7S: Area E Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 2-Year Rainfall=7." Runoff Area=3,33 sf Runoff Volume=.236 af Runoff Depth>3.9" Flow Length=42' Tc=3. min CN= Time (hours)

48 Existing Data - August 26 Existing Drainage Type II 24-hr 2-Year Rainfall=7." Printed 8/24/26 Page 33 Summary for Subcatchment 8S: Area E2 Runoff = hrs, Volume=. af, Depth> 3.74" Runoff by SCS TR-2 method, UH=SCS, Time Span=.-2. hrs, dt=. hrs Type II 24-hr 2-Year Rainfall=7." Area (sf) CN Description * *, ,8 74 Weighted Average, % Pervious Area 37.9% Impervious Area Tc Length Slope Velocity Capacity Description (min) (ft/ft) (ft/sec) (cfs) Sheet Flow, Grass: Short n=. P2= 3.7" Shallow Concentrated Flow, Grassed Waterway Kv=. fps. 272 Total Subcatchment 8S: Area E2 Hydrograph Runoff Flow (cfs) cfs Type II 24-hr 2-Year Rainfall=7." Runoff Area=6,8 sf Runoff Volume=. af Runoff Depth>3.74" Flow Length=272' Tc=. min CN= Time (hours)

49 Existing Data - August 26 Existing Drainage Type II 24-hr 2-Year Rainfall=7." Printed 8/24/26 Page 34 Summary for Reach 9R: (new Reach) Inflow Area =.79 ac, 7.79% Impervious, Inflow Depth > 3.9" for 2-Year event Inflow = hrs, Volume=.236 af Outflow = hrs, Volume=.236 af, Atten= 3%, Lag=.4 min Routing by Stor-Ind+Trans method, Time Span=.-2. hrs, dt=. hrs Max. Velocity= 3.6 fps, Min. Travel Time=.8 min Avg. Velocity =.3 fps, Avg. Travel Time= 2. min Peak Storage= hrs Average Depth at Peak Storage=.34' Bank-Full Depth=.', Capacity at Bank-Full= 42.8 cfs.' x.' deep Parabolic Channel, n=.24 Length= 7.' Slope=.9 '/' Inlet Invert= 696.', Outlet Invert= 693.' Reach 9R: (new Reach) Hydrograph Flow (cfs) cfs 4.6 cfs Inflow Area=.79 ac Avg. Flow Depth=.34' Max Vel=3.6 fps n=.24 L=7.' S=.9 '/' Capacity=42.8 cfs Inflow Outflow Time (hours)

50 Existing Data - August 26 Existing Drainage Type II 24-hr 2-Year Rainfall=7." Printed 8/24/26 Page 3 Reach 9R: (new Reach) Stage-Discharge Primary Depth 2 2 Discharge (cfs) Reach 9R: (new Reach) Stage-Storage Storage Depth Storage (cubic-feet) 7 8 9,

51 Existing Data - August 26 Existing Drainage Type II 24-hr 2-Year Rainfall=7." Printed 8/24/26 Page 36 Stage-Discharge for Reach 9R: (new Reach) Velocity (ft/sec) Discharge (cfs) Velocity (ft/sec) Discharge (cfs)

52 Existing Data - August 26 Existing Drainage Type II 24-hr 2-Year Rainfall=7." Printed 8/24/26 Page 37 Stage-Area-Storage for Reach 9R: (new Reach) End-Area (sq-ft) Storage (cubic-feet) End-Area (sq-ft) Storage (cubic-feet) , , , ,47