Loading...
HomeMy WebLinkAboutApplication Materials ADJUSTMENT REVIEW www.eugene-or.gov/planning Planning & Development Updated: January 2025 Planning Division 99 W. 10TH Avenue Suite 290, Eugene, OR 97401 Phone: 541.682.5377 or E-mail: planning@ci.eugene.or.us Page 1 of 3 Please complete the following application checklist. Note that additional information may be required upon further review to adequately address the applicable criteria for approval. If you have any questions about filling out this application, please contact Planning staff at the Permit and Information Center, phone (541) 682-5377, 99 West 10th Avenue, Eugene. List all Assessor’s Map and Tax Lot numbers of the property included in the request. Proposals are required to include all property under contiguous ownership of the applicant. Assessor’s Map Tax Lot Existing Zoning Code Sections Proposed for Adjustment Review List specific code sections for which adjustment review is proposed. Check if the Adjustment Review is for any of the following: Large commercial facility Large multi-tenant commercial facility, or Multiple-family housing Does adjustment request affect at least 2 of the following: Yes No (If yes, this application will be processed as a major adjustment review.) (a) Maximum front yard setbacks (b) Building orientation (c) Building entrances (d) On-site pedestrian circulation (e) Block requirements or street layout Does adjustment request include stormwater drainage facilities: Yes No (If request includes Pollution Reduction/Flow Control, submit approved alternative design. If request includes Source Control, submit DAR form.) Does request include an adjustment of internal vehicle stacking at Eugene Code Section 9.6703(3)(a): Yes No If yes, submit an Alternative Traffic Safety Study (ATSS). Associated pending Land Use Application or Building Permit numbers: www.eugene-or.gov/planning Planning & Development Updated: January 2025 Planning Division 99 W. 10TH Avenue Suite 290, Eugene, OR 97401 Phone: 541.682.5377 or E-mail: planning@ci.eugene.or.us Page 2 of 3 Filing Fee A filing fee must accompany all applications. The fee varies depending upon the type of application and is adjusted periodically by the City Manager. Check with Planning staff at the Permit and Information Center to determine the required fee or check website at www.eugeneplanning.org Submittal Requirements: Provide 2 paper copies and one digital copy (CD, USB Drive, or Other) of all application materials (i.e. written statement, site plans, etc.). Digital files must be in PDF file format. Please note that it is the applicant’s responsibility to make sure that the digital and paper copies are identical. Following completeness review, an updated digital and paper copies may be required. All paper site plans must be folded to a size equal or less than 11” x 17”. Written Statement Submit a detailed written statement describing how this request is consistent with all applicable criteria beginning at Eugene Code Section 9.8030. Please note: it is the applicant’s responsibility to provide adequate information demonstrating how the project satisfies the applicable approval criteria. Failure to provide such information may result in denial of your application. Submit an Alternative Traffic Safety Study (ATSS) if an adjustment is requested to required internal vehicle stacking at EC 9.6703(3)(a). Demonstrate that access to the development site is located in accordance with EC 7.420. Site Plan Requirements Show date, north arrow, and standard engineer’s or architect’s scale. Show the Assessor’s Map and Tax Lot numbers. Show a vicinity map on the plan. (Vicinity map does not need to be drawn to scale.) Show the dimensions of the site plan boundary. Show the location of all existing structures and indicate whether they will remain or be removed. Show any site features necessary to illustrate the basis for the proposed adjustment. Show access to the development site. Site Plan must be prepared, stamped and signed by one of the following: Oregon Licensed architect, Oregon licensed civil engineer, Oregon licensed landscape architect, a member of the American Institute of Certified Planners, or an Oregon licensed land surveyor. www.eugene-or.gov/planning Planning & Development Updated: January 2025 Planning Division 99 W. 10TH Avenue Suite 290, Eugene, OR 97401 Phone: 541.682.5377 or E-mail: planning@ci.eugene.or.us Page 3 of 3 By signing, the undersigned certifies that he/she has read and understood the submittal requirements outlined, and that he/she understands that omission of any listed item may cause delay in processing the application. I (We), the undersigned, acknowledge that the information supplied in this application is complete and accurate to the best of my (our) k nowledge. OWNER (Also the Applicant? Yes / No): Name (print): ____________________________________________ Phone: ___________________________________________ Address: ___________________________________________________________________________________________________ City/State/Zip: _______________________________________________________________________________________________ Signature: ___________________________________________________________________________________________________ APPLICANT / APPLICANT’S REPRESENTATIVE (Check one): Name (print): ________________________________________________________________________________________________ Company/Organization: _______________________________________________________________________________________ Address: ____________________________________________________________________________________________________ City/State/Zip: ___________________________________________ E-mail (if applicable): ________________________________ Phone: _________________________________________________ Fax: ______________________________________________ Signature: ___________________________________________________________________________________________________ APPLICANT’S REPRESENTATIVE / DESIGNATED CONTACT PERSON (Check all that apply): Name (print): ________________________________________________________________________________________________ Company/Organization: _______________________________________________________________________________________ Address: ____________________________________________________________________________________________________ City/State/Zip: ___________________________________________ E-mail (if applicable): ________________________________ Phone: _________________________________________________ Fax: ______________________________________________ Signature: ___________________________________________________________________________________________________ Note: This is not a complete list of requirements. Additional information may be required after further review in order to adequately address the applicable approval criteria. Emily Estates Subdivision – Tentative EC 9.8030 Adjustment Review – Approval Criteria. (24) Stormwater Quality, Flow Control, Oil Control and Source Control Standards Adjustment. (Adjustments under this subsection are not permitted within the /CL Clear Lake Overlay Zone.) (b) The requirement in EC 9.6792(3)(a) and EC 9.3155(17)(c)5 that all stormwater quality facilities be selected from and sited, designed, and constructed according to the Stormwater Management Manual may be adjusted upon finding that all of the following requirements are met: 1. The proposed alternative design will achieve equal, or superior, results for function (reducing pollution), maintainability and safety, and the proposed siting does not adversely affect structures or other properties. The proposed alternative design closely matches an approved stormwater facility in the 2025 Eugene Stormwater Management Manual, a Stormwater Planter. The only proposed variance is for the ponding depth to exceed 12 inches. A Pond facility described in the 2025 ESMM does allow for ponding depths above 12 inches, and therefore, the proposed alternative would be considered a “hybrid” facility between a Stormwater Planter and a Dry Detention Pond. Given the limited design variance requested, the proposed alternative design will achieve equal results of a Stormwater Planter in the following ways: • Function (reducing pollution): The hydraulic modeling shows that all runoff within the planter during a Pollution Reduction storm models to filtrate through the growing medium and leave through the underdrain piping. This functions exactly as required for a traditional Stormwater Planter. The ponding depth above 12” only comes into consideration during storms larger than the Pollution Reduction event. The increased ponding depth is needed to meet Flow Control requirements in releasing the runoff at or below pre- construction peak flowrates. The increased ponding depth provides needed storage within the facility rather than increasing the horizontal footprint and impacting the development. • Maintainability: A gravel ramp or similar is proposed into the facility to allow for maintenance crews to access the facility. Otherwise, it is proposed to follow the standard maintenance plan for Stormwater Planters from the 2025 ESMM. With the provided access, the proposed alternative design will provide equal ability to maintain as a standard Stormwater Planter. • Safety: Since the depth of facility will exceed 30 inches, fall protection fencing is proposed around the facility to address safety concerns. With the proposed fencing, equal results for safety are achieved as a standard Stormwater Planter. • Due to the increased ponding depth during large storm events, specific plantings are required that can tolerate that condition for short periods of time. The planting plan will be designed with plants that are on the City of Eugene approved list and can tolerate being temporarily submerged in large storm events. The drawdown time models to be less than 30 hours during a Flood Control design storm, in compliance with the 2025 ESMM. 2. The applicant’s written description of the proposed alternative design has been reviewed and approved by the City Engineer. The description of the proposed design submitted for review must include all of the following information for each component of the proposed alternative design: a. Size, technical description, capacity, capital cost, design life, construction process and costs, consequences of improper construction, operation and maintenance requirements and costs; Size: The current proposed size is approximately 1,600 SF, the shape is not completely rectangular, so the width and length vary. The current proposed depth is 33” with an approximate ponding depth of 30.” See the stormwater report prepared by A & O Engineering, LLC and associated storm design plans for more information. Technical Description: Will function exactly like a Stormwater Planter in the 2025 ESMM, only with a deeper ponding depth. Capacity: See stormwater report for information. Emily Estates Subdivision – Tentative Capital Cost: This will be a privately owned and maintained facility. Cost very similar to standard Stormwater Planter. Design Life: Will be very similar to standard Stormwater Planter. Construction process and costs: Will be very similar to standard Stormwater Planter. Consequences of Improper Construction: The consequences would be the same as a standard Stormwater Planter. O&M: Will be the same as a standard Stormwater Planter, with the addition of adding a ramp into the facility which will also need to be maintained. b. Data on the effectiveness of proposed alternative technologies, if available, including data from laboratory testing and pilot/full-scale operations, and information regarding the operations of any full-scale installations; N/A. c. Any other available information about the proposed design, including peer review articles, scientific or engineering journals, and approvals from other jurisdictions. Preliminary correspondence with City Engineering staff indicated proposed alternative design would be approvable. This is a standard hybrid design that is acceptable in other jurisdictions with the addition of specific plantings that can survive a higher ponding depth. 3. The applicant has submitted a method and schedule for monitoring the effectiveness of the proposed design once constructed, and a schedule for its maintenance. The O&M will match the standard forms for a Stormwater Planter as provided in the 2025 ESMM. 4. The applicant has submitted a signed statement that the applicant will replace the alternative stormwater quality facility if the facility does not function as proposed. (e) The requirements in EC 9.6793(3)(d) that all flow control facilities be selected from and sited, designed, and constructed according to the flow control provisions and the facility design requirements set forth in the Stormwater Management Manual may be adjusted upon finding that all of the following requirements are met: 1. The proposed alternative design will achieve equal, or superior, results for function (maintaining flow or restricting flow or both), maintainability and safety, and the proposed siting does not adversely affect structures or other properties; See above. Proposed design will achieve equal superior results for flow control, with additional water storage within the facility. See stormwater report and plans for more information. 2. The applicant’s written description of the proposed alternative design has been reviewed and approved by the City Engineer. The description of the proposed design submitted for review must include all of the following information for each component of the proposed alternative design: a. Size, technical description, capacity, capital cost, design life, construction process and costs, consequences of improper construction, operation and maintenance requirements and costs; See above. b. Data on the effectiveness of proposed alternative design, if available, including data from laboratory testing and pilot/full-scale operations, and information regarding the operations of any full-scale installations; N/A. Emily Estates Subdivision – Tentative c. Any other available information about the proposed design, including peer review articles, scientific or engineering journals, and approvals from other jurisdictions. See above. 3. The applicant has submitted a method and schedule for monitoring the effectiveness of the proposed design once constructed, and a schedule for its maintenance; See above. 4. The applicant has submitted a signed statement that the applicant will replace the alternative flow control facility if the facility does not function as proposed. Once provided by the city, the applicant will sign a statement stating that the applicant will replace the alternative flow control facility if the facility does not function as proposed.  Page 2 Curve Number: 82 Land Description: Woods/Grass Combination, Fair Condition, HSG D Time of Concentration: Combination of Sheet Flow and Shallow Concentrated Flow, total of 11.1 minutes The existing site naturally drains to the west to Hawkins Lane at approximate slopes exceeding 15%. Stormwater Calculation Parameters The City of Eugene standards were followed for performing stormwater calculations. HydroCAD software was utilized to perform hydraulic calculations. Below are the parameters used for the stormwater calculations taken from the Eugene Stormwater Management Manual 2025 unless otherwise noted: Water Quality Storm: 1.40 inches for 24 hours 2-Year Storm: 3.12 inches for 24 hours 5-Year Storm: 3.60 inches for 24 hours 10-year Storm: 4.46 inches for 24 hours Flood Control Design Storm: 10-Year Storm per Appendix K-1 of the 2025 ESMM Storm Distribution Type: IA – 24-hour (NRCS SCS Rainfall Distributions) Runoff Method: Santa Barbara Urban Hydrograph Method (SBUH) Time of Concentration: 5 Minutes for Post Construction Runoff Design Calculations Hydraulic calculations were performed to ensure stormwater facilities were sized to adequately to convey stormwater off the property without increasing the risk of damage to surrounding infrastructure or impacting local water quality. The stormwater facility is sized to meet treatment and detention requirements set by the City of Eugene. Storage within the proposed filtration stormwater planter is adequate for detention requirements with HydroCAD models simulating the 10-year storm. The proposed development will generate lower peak runoff rates under post-development conditions than the modeled rates from the existing conditions. Water quality requirements are satisfied by routing the total runoff volume from the new impervious surfaces for a Pollution Reduction event for Eugene through the soil media of stormwater facilities HydroCAD software was utilized to determine the runoff volume directed into the proposed facility. Peak flow rates were determined using times of concentration described in the appendix for existing conditions, and a time of concentration of 5 minutes for post-construction conditions. Time of  Page 3 concentration was calculated using HydroCAD software with site characteristics including surface elevations, soil type, and surface conditions. Storm Design and Hydraulic Calculations The applicant is proposing to construct a shared filtration stormwater planter for the private development. Due to grading constrains, less than 500 square feet of impervious private street at the entrance from Hawkins Lane is proposed to direct sheet drain into the Hawkins Lane right-of-way. Treated and detained runoff from the filtration stormwater planter is proposed to be piped into a public curb inlet just south of the property within Hawkins Lane as shown on the plans. See the table below for storm facility physical characteristics: Table 1: Filtration Stormwater Planter Physical Characteristics Open Storage Bottom Elev. [Ft] Open Storage Top Elev. [Ft] Area [SF] Depth [Ft] 753.05 755.80 1,613 2.75 In addition to the open storage shown above, the planter will have a 12” deep rock chamber and a 12” thick growing medium below the open storage. The rock chamber will have a perforated pipe to serve as an underdrain. The table below summarizes the pertinent planter elevations including outlet elevations and Hydraulic Grade Line Elevations: Table 2: Planter Outlet Elevations and HGLs 2" Orifice [Ft] 3" Orifice [Ft] 8" Overflow [Ft] Pollution Reduction HGL [Ft] 10-Year HGL [Ft] 754.05 755.05 755.55 753.50 755.50 The data in Table 2 above shows compliance with City of Eugene requirements in a couple of important points: 1. The peak water level during the Pollution Reduction storm event is below any orifice, thus modeling that all stormwater will filtrate through the growing medium, and leave through the underdrain piping. This shows compliance with stormwater treatment requirements of the City of Eugene. 2. The 10-Year storm peak water level is 3” below the Open Storage Top Elevation, thus meeting Eugene’s requirements of 2” of freeboard. Additionally, to be in compliance with Flow Control requirements, pre-construction peak flowrates from the site were analyzed and compared with the modeled post-construction peak flowrates. The table below summarizes the peak flowrates:  Page 4 Table 3: Detention/Peak Flowrate Analysis Storm Event Pre-Construction Peak Flowrate [cfs] Post-Construction Peak Flowrate [cfs] 2-Year 0.36 0.26 5-Year 0.48 0.34 10-Year 0.69 0.62 The data in table 3 show that post-construction peak flowrates are detained with the filtration stormwater planter to be equal to or below pre-construction peak flowrates up to the Flood Control Design Storm, thus Eugene requirements for detention are met. Stormwater Facility Variance Due to multiple factors including site topography (on-site slopes that exceed 15%) and available space, it is proposed to construct a filtration stormwater planter with a ponding depth that exceeds 12 inches as required in the 2025 ESMM. With the constraints, a pond is not feasible for this project. The proposal is to construct a stormwater planter with walls around the perimeter, but allow for a ponding depth exceeding 12” as allowed inside of a pond. The proposed planter with an increased ponding depth will still meet stormwater treatment requirements by providing filtration. It also will meet flow control requirements. Therefore, the proposed variance will provide equal results for function as a stormwater planter. Since the depth will exceed 30”, a fall protection fencing will be installed for safety. Also, a ramp entrance will be provided for maintenance crew access to the facility. Conclusion The proposed stormwater drainage plan detailed in this report meets city requirements and will adequately serve the new development. The peak water elevations within the storm facility during the water quality storm do not reach the lowest orifices and thus receive sufficient treatment prior to discharging into the public system. The peak water elevations within the storm facilities during the 10- year design storm models to not exceed the top of the facility and will not cause any damage to the proposed development or surrounding infrastructure. Peak post construction discharge rates from the site are shown to be limited to- or below existing condition peak discharge rates and thus will not increase the burden on any existing City stormwater infrastructure. Appendix • HydroCAD Calculations for Hawkins Ln Subdivision  Page 5 • Stormwater Drainage Basin Map • Core GeoEngineering Preliminary Geologic Hazard Assessment & Geotechnical Engineering Report 1S Existing Conditions (Pre-Construction) 5S Lot Impervious Areas 6S Impervious Private Street Area 8S Driveway Direct Drain to Hawkins Lane 9R Discharge to Public Curb Inlet 70416 in Hawkins Lane 7P Filtration Storm Planter (Overflow 30" Above Flowline) Routing Diagram for Hawkins Subdivision HydroCAD 7-6-2026 Prepared by A&O Engineering LLC, Printed 9/22/2026 HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Subcat Reach Pond Link Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 2HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Rainfall Events Listing (selected events) Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 01-Pollution Reduction Type IA 24-hr Default 24.00 1 1.40 2 2 02 Year Type IA 24-hr Default 24.00 1 3.12 2 3 05 Year Type IA 24-hr Default 24.00 1 3.60 2 4 10 Year Type IA 24-hr Default 24.00 1 4.46 2 Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 3HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 0.011 98 Impervious Driveway (8S) 0.849 98 Impervious Lot Areas (5S) 0.310 98 Impervious Surface (6S) 1.171 82 Woods/grass comb., Fair, HSG D (1S) 2.342 90 TOTAL AREA Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 4HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 0.000 HSG B 0.000 HSG C 1.171 HSG D 1S 1.171 Other 5S, 6S, 8S 2.342 TOTAL AREA Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 5HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 0.000 0.000 0.000 0.011 0.011 Impervious Driveway 8S 0.000 0.000 0.000 0.000 0.849 0.849 Impervious Lot Areas 5S 0.000 0.000 0.000 0.000 0.310 0.310 Impervious Surface 6S 0.000 0.000 0.000 1.171 0.000 1.171 Woods/grass comb., Fair 1S 0.000 0.000 0.000 1.171 1.171 2.342 TOTAL AREA Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 6HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Time span=0.00-32.00 hrs, dt=0.05 hrs, 641 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=1.171 ac 0.00% Impervious Runoff Depth=0.29"Subcatchment 1S: Existing Conditions Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 Runoff=0.03 cfs 0.029 af Runoff Area=37,000 sf 100.00% Impervious Runoff Depth=1.18"Subcatchment 5S: Lot Impervious Areas Tc=5.0 min CN=0/98 Runoff=0.26 cfs 0.084 af Runoff Area=13,522 sf 100.00% Impervious Runoff Depth=1.18"Subcatchment 6S: Impervious Private Tc=5.0 min CN=0/98 Runoff=0.09 cfs 0.031 af Runoff Area=500 sf 100.00% Impervious Runoff Depth=1.18"Subcatchment 8S: Driveway Direct Drain to Tc=0.0 min CN=0/98 Runoff=0.00 cfs 0.001 af Inflow=0.10 cfs 0.115 afReach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Outflow=0.10 cfs 0.115 af Peak Elev=753.50' Storage=731 cf Inflow=0.35 cfs 0.114 afPond 7P: Filtration Storm Planter (Overflow Outflow=0.09 cfs 0.114 af Total Runoff Area = 2.342 ac Runoff Volume = 0.144 af Average Runoff Depth = 0.74" 49.99% Pervious = 1.171 ac 50.01% Impervious = 1.171 ac Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 7HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff = 0.03 cfs @ 8.08 hrs, Volume= 0.029 af, Depth= 0.29" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Area (ac) CN Description 1.171 82 Woods/grass comb., Fair, HSG D 1.171 82 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.5 112 0.2000 0.20 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.12" Using McCuen-Spiess flow length 1.6 218 0.2000 2.24 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 11.1 330 Total Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.036 0.034 0.032 0.03 0.028 0.026 0.024 0.022 0.02 0.018 0.016 0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Runoff Area=1.171 ac Runoff Volume=0.029 af Runoff Depth=0.29" Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 0.03 cfs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 8HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Lot Impervious Areas Runoff = 0.26 cfs @ 7.91 hrs, Volume= 0.084 af, Depth= 1.18" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Area (sf) CN Description * 37,000 98 Impervious Lot Areas 37,000 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 5S: Lot Impervious Areas Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Runoff Area=37,000 sf Runoff Volume=0.084 af Runoff Depth=1.18" Tc=5.0 min CN=0/98 0.26 cfs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 9HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Impervious Private Street Area Runoff = 0.09 cfs @ 7.91 hrs, Volume= 0.031 af, Depth= 1.18" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Area (sf) CN Description * 13,522 98 Impervious Surface 13,522 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: Impervious Private Street Area Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Runoff Area=13,522 sf Runoff Volume=0.031 af Runoff Depth=1.18" Tc=5.0 min CN=0/98 0.09 cfs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 10HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff = 0.00 cfs @ 7.82 hrs, Volume= 0.001 af, Depth= 1.18" Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Area (sf) CN Description * 500 98 Impervious Driveway 500 98 100.00% Impervious Area Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.004 0.004 0.003 0.003 0.003 0.003 0.003 0.002 0.002 0.002 0.002 0.002 0.001 0.001 0.001 0.001 0.001 0.000 0.000 0 Type IA 24-hr 01-Pollution Reduction Rainfall=1.40" Runoff Area=500 sf Runoff Volume=0.001 af Runoff Depth=1.18" Tc=0.0 min CN=0/98 0.00 cfs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 11HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Area = 1.171 ac,100.00% Impervious, Inflow Depth = 1.18" for 01-Pollution Reduction event Inflow = 0.10 cfs @ 7.82 hrs, Volume= 0.115 af Outflow = 0.10 cfs @ 7.82 hrs, Volume= 0.115 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Outflow Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Inflow Area=1.171 ac 0.10 cfs 0.10 cfs Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 12HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Area = 1.160 ac,100.00% Impervious, Inflow Depth = 1.18" for 01-Pollution Reduction event Inflow = 0.35 cfs @ 7.91 hrs, Volume= 0.114 af Outflow = 0.09 cfs @ 7.20 hrs, Volume= 0.114 af, Atten= 74%, Lag= 0.0 min Primary = 0.09 cfs @ 7.20 hrs, Volume= 0.114 af Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Routing by Stor-Ind method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Peak Elev= 753.50' @ 9.34 hrs Surf.Area= 1,613 sf Storage= 731 cf Flood Elev= 755.80' Surf.Area= 1,613 sf Storage= 4,436 cf Plug-Flow detention time= 50.3 min calculated for 0.114 af (100% of inflow) Center-of-Mass det. time= 50.3 min ( 746.9 - 696.6 ) Volume Invert Avail.Storage Storage Description #1 753.05' 4,436 cf Open Storage (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 753.05 1,613 0 0 755.80 1,613 4,436 4,436 Device Routing Invert Outlet Devices #1 Primary 753.05'2.500 in/hr Exfiltration over Surface area #2 Primary 755.55'8.0" Horiz. 8" Overflow C= 0.600 Limited to weir flow at low heads #3 Primary 754.05'2.0" Vert. 2" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads #4 Primary 755.05'3.0" Vert. 3" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=0.09 cfs @ 7.20 hrs HW=753.08' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.09 cfs) 2=8" Overflow ( Controls 0.00 cfs) 3=2" Orifices ( Controls 0.00 cfs) 4=3" Orifices ( Controls 0.00 cfs) Type IA 24-hr 01-Pollution Reduction Rainfall=1.40"Hawkins Subdivision HydroCAD 7-6-202 Printed 9/22/2026Prepared by A&O Engineering LLC Page 13HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Primary Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=1.160 ac Peak Elev=753.50' Storage=731 cf 0.35 cfs 0.09 cfs Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 14HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Time span=0.00-32.00 hrs, dt=0.05 hrs, 641 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=1.171 ac 0.00% Impervious Runoff Depth=1.47"Subcatchment 1S: Existing Conditions Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 Runoff=0.36 cfs 0.144 af Runoff Area=37,000 sf 100.00% Impervious Runoff Depth=2.89"Subcatchment 5S: Lot Impervious Areas Tc=5.0 min CN=0/98 Runoff=0.62 cfs 0.204 af Runoff Area=13,522 sf 100.00% Impervious Runoff Depth=2.89"Subcatchment 6S: Impervious Private Tc=5.0 min CN=0/98 Runoff=0.23 cfs 0.075 af Runoff Area=500 sf 100.00% Impervious Runoff Depth=2.89"Subcatchment 8S: Driveway Direct Drain to Tc=0.0 min CN=0/98 Runoff=0.01 cfs 0.003 af Inflow=0.26 cfs 0.282 afReach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Outflow=0.26 cfs 0.282 af Peak Elev=754.77' Storage=2,777 cf Inflow=0.84 cfs 0.279 afPond 7P: Filtration Storm Planter (Overflow Outflow=0.26 cfs 0.279 af Total Runoff Area = 2.342 ac Runoff Volume = 0.426 af Average Runoff Depth = 2.18" 49.99% Pervious = 1.171 ac 50.01% Impervious = 1.171 ac Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 15HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff = 0.36 cfs @ 8.01 hrs, Volume= 0.144 af, Depth= 1.47" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 02 Year Rainfall=3.12" Area (ac) CN Description 1.171 82 Woods/grass comb., Fair, HSG D 1.171 82 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.5 112 0.2000 0.20 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.12" Using McCuen-Spiess flow length 1.6 218 0.2000 2.24 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 11.1 330 Total Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type IA 24-hr 02 Year Rainfall=3.12" Runoff Area=1.171 ac Runoff Volume=0.144 af Runoff Depth=1.47" Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 0.36 cfs Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 16HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Lot Impervious Areas Runoff = 0.62 cfs @ 7.90 hrs, Volume= 0.204 af, Depth= 2.89" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 02 Year Rainfall=3.12" Area (sf) CN Description * 37,000 98 Impervious Lot Areas 37,000 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 5S: Lot Impervious Areas Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type IA 24-hr 02 Year Rainfall=3.12" Runoff Area=37,000 sf Runoff Volume=0.204 af Runoff Depth=2.89" Tc=5.0 min CN=0/98 0.62 cfs Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 17HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Impervious Private Street Area Runoff = 0.23 cfs @ 7.90 hrs, Volume= 0.075 af, Depth= 2.89" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 02 Year Rainfall=3.12" Area (sf) CN Description * 13,522 98 Impervious Surface 13,522 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: Impervious Private Street Area Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.25 0.24 0.23 0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type IA 24-hr 02 Year Rainfall=3.12" Runoff Area=13,522 sf Runoff Volume=0.075 af Runoff Depth=2.89" Tc=5.0 min CN=0/98 0.23 cfs Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 18HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff = 0.01 cfs @ 7.81 hrs, Volume= 0.003 af, Depth= 2.89" Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 02 Year Rainfall=3.12" Area (sf) CN Description * 500 98 Impervious Driveway 500 98 100.00% Impervious Area Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.009 0.009 0.008 0.008 0.007 0.007 0.006 0.006 0.005 0.005 0.004 0.004 0.003 0.003 0.002 0.002 0.001 0.001 0.000 0 Type IA 24-hr 02 Year Rainfall=3.12" Runoff Area=500 sf Runoff Volume=0.003 af Runoff Depth=2.89" Tc=0.0 min CN=0/98 0.01 cfs Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 19HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Area = 1.171 ac,100.00% Impervious, Inflow Depth = 2.89" for 02 Year event Inflow = 0.26 cfs @ 8.98 hrs, Volume= 0.282 af Outflow = 0.26 cfs @ 8.98 hrs, Volume= 0.282 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Outflow Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=1.171 ac 0.26 cfs 0.26 cfs Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 20HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Area = 1.160 ac,100.00% Impervious, Inflow Depth = 2.89" for 02 Year event Inflow = 0.84 cfs @ 7.90 hrs, Volume= 0.279 af Outflow = 0.26 cfs @ 9.01 hrs, Volume= 0.279 af, Atten= 69%, Lag= 66.7 min Primary = 0.26 cfs @ 9.01 hrs, Volume= 0.279 af Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Routing by Stor-Ind method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Peak Elev= 754.77' @ 9.01 hrs Surf.Area= 1,613 sf Storage= 2,777 cf Flood Elev= 755.80' Surf.Area= 1,613 sf Storage= 4,436 cf Plug-Flow detention time= 181.2 min calculated for 0.279 af (100% of inflow) Center-of-Mass det. time= 181.3 min ( 848.4 - 667.1 ) Volume Invert Avail.Storage Storage Description #1 753.05' 4,436 cf Open Storage (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 753.05 1,613 0 0 755.80 1,613 4,436 4,436 Device Routing Invert Outlet Devices #1 Primary 753.05'2.500 in/hr Exfiltration over Surface area #2 Primary 755.55'8.0" Horiz. 8" Overflow C= 0.600 Limited to weir flow at low heads #3 Primary 754.05'2.0" Vert. 2" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads #4 Primary 755.05'3.0" Vert. 3" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=0.26 cfs @ 9.01 hrs HW=754.77' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.09 cfs) 2=8" Overflow ( Controls 0.00 cfs) 3=2" Orifices (Orifice Controls 0.17 cfs @ 3.85 fps) 4=3" Orifices ( Controls 0.00 cfs) Type IA 24-hr 02 Year Rainfall=3.12"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 21HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Primary Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=1.160 ac Peak Elev=754.77' Storage=2,777 cf 0.84 cfs 0.26 cfs Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 22HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Time span=0.00-32.00 hrs, dt=0.05 hrs, 641 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=1.171 ac 0.00% Impervious Runoff Depth=1.87"Subcatchment 1S: Existing Conditions Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 Runoff=0.48 cfs 0.182 af Runoff Area=37,000 sf 100.00% Impervious Runoff Depth=3.37"Subcatchment 5S: Lot Impervious Areas Tc=5.0 min CN=0/98 Runoff=0.72 cfs 0.238 af Runoff Area=13,522 sf 100.00% Impervious Runoff Depth=3.37"Subcatchment 6S: Impervious Private Tc=5.0 min CN=0/98 Runoff=0.26 cfs 0.087 af Runoff Area=500 sf 100.00% Impervious Runoff Depth=3.37"Subcatchment 8S: Driveway Direct Drain to Tc=0.0 min CN=0/98 Runoff=0.01 cfs 0.003 af Inflow=0.34 cfs 0.329 afReach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Outflow=0.34 cfs 0.329 af Peak Elev=755.14' Storage=3,365 cf Inflow=0.98 cfs 0.325 afPond 7P: Filtration Storm Planter (Overflow Outflow=0.33 cfs 0.325 af Total Runoff Area = 2.342 ac Runoff Volume = 0.511 af Average Runoff Depth = 2.62" 49.99% Pervious = 1.171 ac 50.01% Impervious = 1.171 ac Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 23HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff = 0.48 cfs @ 8.00 hrs, Volume= 0.182 af, Depth= 1.87" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 05 Year Rainfall=3.60" Area (ac) CN Description 1.171 82 Woods/grass comb., Fair, HSG D 1.171 82 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.5 112 0.2000 0.20 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.12" Using McCuen-Spiess flow length 1.6 218 0.2000 2.24 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 11.1 330 Total Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type IA 24-hr 05 Year Rainfall=3.60" Runoff Area=1.171 ac Runoff Volume=0.182 af Runoff Depth=1.87" Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 0.48 cfs Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 24HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Lot Impervious Areas Runoff = 0.72 cfs @ 7.90 hrs, Volume= 0.238 af, Depth= 3.37" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 05 Year Rainfall=3.60" Area (sf) CN Description * 37,000 98 Impervious Lot Areas 37,000 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 5S: Lot Impervious Areas Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type IA 24-hr 05 Year Rainfall=3.60" Runoff Area=37,000 sf Runoff Volume=0.238 af Runoff Depth=3.37" Tc=5.0 min CN=0/98 0.72 cfs Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 25HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Impervious Private Street Area Runoff = 0.26 cfs @ 7.90 hrs, Volume= 0.087 af, Depth= 3.37" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 05 Year Rainfall=3.60" Area (sf) CN Description * 13,522 98 Impervious Surface 13,522 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: Impervious Private Street Area Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type IA 24-hr 05 Year Rainfall=3.60" Runoff Area=13,522 sf Runoff Volume=0.087 af Runoff Depth=3.37" Tc=5.0 min CN=0/98 0.26 cfs Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 26HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff = 0.01 cfs @ 7.80 hrs, Volume= 0.003 af, Depth= 3.37" Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 05 Year Rainfall=3.60" Area (sf) CN Description * 500 98 Impervious Driveway 500 98 100.00% Impervious Area Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.011 0.01 0.01 0.009 0.009 0.008 0.008 0.007 0.007 0.006 0.006 0.005 0.005 0.004 0.004 0.003 0.003 0.002 0.002 0.001 0.001 0.000 0 Type IA 24-hr 05 Year Rainfall=3.60" Runoff Area=500 sf Runoff Volume=0.003 af Runoff Depth=3.37" Tc=0.0 min CN=0/98 0.01 cfs Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 27HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Area = 1.171 ac,100.00% Impervious, Inflow Depth = 3.37" for 05 Year event Inflow = 0.34 cfs @ 8.84 hrs, Volume= 0.329 af Outflow = 0.34 cfs @ 8.84 hrs, Volume= 0.329 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Outflow Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Inflow Area=1.171 ac 0.34 cfs 0.34 cfs Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 28HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Area = 1.160 ac,100.00% Impervious, Inflow Depth = 3.37" for 05 Year event Inflow = 0.98 cfs @ 7.90 hrs, Volume= 0.325 af Outflow = 0.33 cfs @ 8.85 hrs, Volume= 0.325 af, Atten= 66%, Lag= 57.0 min Primary = 0.33 cfs @ 8.85 hrs, Volume= 0.325 af Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Routing by Stor-Ind method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Peak Elev= 755.14' @ 8.85 hrs Surf.Area= 1,613 sf Storage= 3,365 cf Flood Elev= 755.80' Surf.Area= 1,613 sf Storage= 4,436 cf Plug-Flow detention time= 179.0 min calculated for 0.325 af (100% of inflow) Center-of-Mass det. time= 179.2 min ( 842.5 - 663.3 ) Volume Invert Avail.Storage Storage Description #1 753.05' 4,436 cf Open Storage (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 753.05 1,613 0 0 755.80 1,613 4,436 4,436 Device Routing Invert Outlet Devices #1 Primary 753.05'2.500 in/hr Exfiltration over Surface area #2 Primary 755.55'8.0" Horiz. 8" Overflow C= 0.600 Limited to weir flow at low heads #3 Primary 754.05'2.0" Vert. 2" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads #4 Primary 755.05'3.0" Vert. 3" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=0.33 cfs @ 8.85 hrs HW=755.14' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.09 cfs) 2=8" Overflow ( Controls 0.00 cfs) 3=2" Orifices (Orifice Controls 0.21 cfs @ 4.82 fps) 4=3" Orifices (Orifice Controls 0.03 cfs @ 1.00 fps) Type IA 24-hr 05 Year Rainfall=3.60"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 29HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Primary Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=1.160 ac Peak Elev=755.14' Storage=3,365 cf 0.98 cfs 0.33 cfs Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 30HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Time span=0.00-32.00 hrs, dt=0.05 hrs, 641 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=1.171 ac 0.00% Impervious Runoff Depth=2.60"Subcatchment 1S: Existing Conditions Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 Runoff=0.69 cfs 0.254 af Runoff Area=37,000 sf 100.00% Impervious Runoff Depth=4.22"Subcatchment 5S: Lot Impervious Areas Tc=5.0 min CN=0/98 Runoff=0.89 cfs 0.299 af Runoff Area=13,522 sf 100.00% Impervious Runoff Depth=4.22"Subcatchment 6S: Impervious Private Tc=5.0 min CN=0/98 Runoff=0.33 cfs 0.109 af Runoff Area=500 sf 100.00% Impervious Runoff Depth=4.22"Subcatchment 8S: Driveway Direct Drain to Tc=0.0 min CN=0/98 Runoff=0.01 cfs 0.004 af Inflow=0.62 cfs 0.412 afReach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Outflow=0.62 cfs 0.412 af Peak Elev=755.50' Storage=3,959 cf Inflow=1.22 cfs 0.408 afPond 7P: Filtration Storm Planter (Overflow Outflow=0.61 cfs 0.408 af Total Runoff Area = 2.342 ac Runoff Volume = 0.666 af Average Runoff Depth = 3.41" 49.99% Pervious = 1.171 ac 50.01% Impervious = 1.171 ac Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 31HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff = 0.69 cfs @ 8.00 hrs, Volume= 0.254 af, Depth= 2.60" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 10 Year Rainfall=4.46" Area (ac) CN Description 1.171 82 Woods/grass comb., Fair, HSG D 1.171 82 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.5 112 0.2000 0.20 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.12" Using McCuen-Spiess flow length 1.6 218 0.2000 2.24 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 11.1 330 Total Subcatchment 1S: Existing Conditions (Pre-Construction) Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type IA 24-hr 10 Year Rainfall=4.46" Runoff Area=1.171 ac Runoff Volume=0.254 af Runoff Depth=2.60" Flow Length=330' Slope=0.2000 '/' Tc=11.1 min CN=82/0 0.69 cfs Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 32HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Lot Impervious Areas Runoff = 0.89 cfs @ 7.90 hrs, Volume= 0.299 af, Depth= 4.22" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 10 Year Rainfall=4.46" Area (sf) CN Description * 37,000 98 Impervious Lot Areas 37,000 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 5S: Lot Impervious Areas Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Type IA 24-hr 10 Year Rainfall=4.46" Runoff Area=37,000 sf Runoff Volume=0.299 af Runoff Depth=4.22" Tc=5.0 min CN=0/98 0.89 cfs Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 33HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: Impervious Private Street Area Runoff = 0.33 cfs @ 7.90 hrs, Volume= 0.109 af, Depth= 4.22" Routed to Pond 7P : Filtration Storm Planter (Overflow 30" Above Flowline) Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 10 Year Rainfall=4.46" Area (sf) CN Description * 13,522 98 Impervious Surface 13,522 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: Impervious Private Street Area Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type IA 24-hr 10 Year Rainfall=4.46" Runoff Area=13,522 sf Runoff Volume=0.109 af Runoff Depth=4.22" Tc=5.0 min CN=0/98 0.33 cfs Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 34HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff = 0.01 cfs @ 7.80 hrs, Volume= 0.004 af, Depth= 4.22" Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24-hr 10 Year Rainfall=4.46" Area (sf) CN Description * 500 98 Impervious Driveway 500 98 100.00% Impervious Area Subcatchment 8S: Driveway Direct Drain to Hawkins Lane Runoff Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.013 0.012 0.011 0.01 0.009 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001 0 Type IA 24-hr 10 Year Rainfall=4.46" Runoff Area=500 sf Runoff Volume=0.004 af Runoff Depth=4.22" Tc=0.0 min CN=0/98 0.01 cfs Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 35HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Area = 1.171 ac,100.00% Impervious, Inflow Depth = 4.22" for 10 Year event Inflow = 0.62 cfs @ 8.30 hrs, Volume= 0.412 af Outflow = 0.62 cfs @ 8.30 hrs, Volume= 0.412 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Reach 9R: Discharge to Public Curb Inlet 70416 in Hawkins Lane Inflow Outflow Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Inflow Area=1.171 ac 0.62 cfs 0.62 cfs Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 36HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Summary for Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Area = 1.160 ac,100.00% Impervious, Inflow Depth = 4.22" for 10 Year event Inflow = 1.22 cfs @ 7.90 hrs, Volume= 0.408 af Outflow = 0.61 cfs @ 8.31 hrs, Volume= 0.408 af, Atten= 50%, Lag= 24.6 min Primary = 0.61 cfs @ 8.31 hrs, Volume= 0.408 af Routed to Reach 9R : Discharge to Public Curb Inlet 70416 in Hawkins Lane Routing by Stor-Ind method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Peak Elev= 755.50' @ 8.31 hrs Surf.Area= 1,613 sf Storage= 3,959 cf Flood Elev= 755.80' Surf.Area= 1,613 sf Storage= 4,436 cf Plug-Flow detention time= 165.5 min calculated for 0.408 af (100% of inflow) Center-of-Mass det. time= 165.7 min ( 824.0 - 658.3 ) Volume Invert Avail.Storage Storage Description #1 753.05' 4,436 cf Open Storage (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 753.05 1,613 0 0 755.80 1,613 4,436 4,436 Device Routing Invert Outlet Devices #1 Primary 753.05'2.500 in/hr Exfiltration over Surface area #2 Primary 755.55'8.0" Horiz. 8" Overflow C= 0.600 Limited to weir flow at low heads #3 Primary 754.05'2.0" Vert. 2" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads #4 Primary 755.05'3.0" Vert. 3" Orifices X 2.00 C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=0.61 cfs @ 8.31 hrs HW=755.50' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.09 cfs) 2=8" Overflow ( Controls 0.00 cfs) 3=2" Orifices (Orifice Controls 0.25 cfs @ 5.64 fps) 4=3" Orifices (Orifice Controls 0.27 cfs @ 2.76 fps) Type IA 24-hr 10 Year Rainfall=4.46"Hawkins Subdivision HydroCAD 7-6-2026 Printed 9/22/2026Prepared by A&O Engineering LLC Page 37HydroCAD® 10.20-9a s/n 04993 © 2026 HydroCAD Software Solutions LLC Pond 7P: Filtration Storm Planter (Overflow 30" Above Flowline) Inflow Primary Hydrograph Time (hours) 32313029282726252423222120191817161514131211109876543210Flow (cfs)1 0 Inflow Area=1.160 ac Peak Elev=755.50' Storage=3,959 cf 1.22 cfs 0.61 cfs WL WL WLWLWLWL WL WL WL WL WL WL WL WL WLWLWLWLWLWL WL WL WL WL WL WL WL WL WL WL WLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWW WW WW WW WW WW WW WW WW WW WWSTSTWW WW WW WLST STSTST STSTST STSTSTST STSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTST STSTST STSTSTSTSTST STSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTST STSTSTSTSTST STSTST STSTSTST STSTST STSTST STST STSTST STSTST STSTST STSTSTST STSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTST TTTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTST STSTSTSTSTSTSTSTSTSTST STSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLWLTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTSTWLWL PROJECT No: HORIZ: VERT: DRAWN BY: SCALE: DATE:REVISIONS: DESIGNED BY: REVIEWED BY: SUBMITTALS:A & O Engineering L.L.C. 380 Q ST. SUITE 200 SPRINGFIELD, OR. 97477 PHONE: (541) 302-9790 info@ao-engr.com CIVIL ENGINEERING & SITE DEVELOPMENT CONSULTING EXPIRES 12/26 P R E L I M I N A R Y Drainage BasinsDRIVEWAY DIRECTDRAIN TO HAWKINS LANE500 SFIMPERVIOUS PRIVATE STREET AREA13,522 SFASSUMED 4,000 SF OFIMPERVIOUS SURFACEASSUMED 4,000 SF OFIMPERVIOUS SURFACEASSUMED 4,000 SF OFIMPERVIOUS SURFACEASSUMED 4,000 SF OFIMPERVIOUS SURFACEASSUMED 3,000 SF OFIMPERVIOUS SURFACEASSUMED 3,000 SF OFIMPERVIOUS SURFACEASSUMED 3,000 SF OFIMPERVIOUS SURFACEASSUMED 4,000 SF OFIMPERVIOUS SURFACEASSUMED 4,000 SF OFIMPERVIOUS SURFACEASSUMED 4,000 SF OFIMPERVIOUS SURFACETOTAL ASSUMED LOTIMPERVIOUS SURFACE = 37,000 SFNOTES:1. SHOWN IMPERVIOUS AREAS ARE PRELIMINARY, AND ARESUBJECT TO CHANGE DURING THE PERMITTING PROCESS. AREASSHOWN WERE FOR PRELIINARY MODELING OF THE SHOWNFILTRATION STORMWATER PLANTER. IF IMPERVIOUS AREASCHANGE FROM THIS MAP, SIZING OF THE PROPOSEDSTORMWATER SYSTEM WILL NEED TO BE REVISITED TO ENSUREPROPER SIZING.2. PERVIOUS SURFACES WERE NOT CONSIDERED IN THESTORMWATER ANALYSIS.