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Home My WebLink AboutSW1180402_Response to Comments & Additional Docs_20180522 May 22nd, 2018 Mr. Corey Anen North Carolina Department of Environmental Quality Division of Energy, Mineral and Land Resources Stormwater Group 1612 Mail Service Center Raleigh, NC 27699-1612 RE: Request for Additional Information - SW1180402 Stormwater Management Permit Application Jo Ellen Ammons Fieldhouse for Mars Hill University Madison County, North Carolina Dear Mr. Anen: Please find below responses to the comments in the Request for Additional Information in regard to Stormwater Permit No. SW1180402. 1. Please submit an SWU-101 – State Stormwater Permit Application Form. This form can be found at: https://deq.nc.gov/about/divisions/energy-mineral-land-resources/energy-mineral- land-rules/stormwater-program/post-construction. A: The complete Storm-EZ tool has been submitted as a part of these responses. The executed sheets in the tool should contain the required information and amount to a completed SWU- 101. 2. Please use the Discrete NRCS Curve Number Method or Simple Method for calculating the water quality volume. Using a composite CN yields an artificially lower volume. General MDC 1 requires the SCM to be sufficiently sized to handle the treatment volume. A: The selected calculation method for computing stormwater runoff volume within t he Storm- EZ tool was the Discrete NRCS Curve Number Method. Per the tool the bioretention cell with internal water storage at the site is sufficiently sized to handle the treatment volume. 3. Please provide a plan view of the bioretention system on the stormwater plan that labels inlets, outlets, erosion protection, underdrain pipes, cleanouts, and other significant features of the system. A: Please review sheets C-103 and C-104 for plan views showing the requested information. 4. The drainage area maps should identify pervious and impervious areas in both the proposed and existing conditions. A: Please review sheet EX-2 and EX-3 that have been added to the plan set for information about pervious/impervious areas at the project site. 5. Please specify on the plans that the vegetation in the bioretention cell should consist of non - clumping, deep-rooted species. A: Please see sheet C-504 note 1 regarding bioretention cell vegetation. 6. Please specify on the plans that the P-index of the media must be less than 50. A: Please see sheet C-504 note 2 regarding the P-index. 7. General MDC 6 requires that SCMs have a method to drawn down any standing water to facilitate maintenance and inspection. A: Please see sheet C-504 note 7 regarding drawdown method. This note shall also be included in the facilities management plan when it is drafted. 8. Revise the plans to show a maintenance access and easement that extend to the nearest right - of-way. The maintenance access must be at least 10’ wide and have side slopes no steeper than 3:1 (horizontal to vertical). The easement must contain the entire maintenance access and SCM. A: Please review sheet C-101 for the location of the access easement. 9. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other documents. Pdfs must be uploaded using the form at: https://edocs.deq.nc.gov/Forms/SW_Project_Submittal A: Noted Based on your letter, dated May 11th, 2018, hard copies and PDFs of the revised plans and calculations will be provided. Please feel free to contact us if you have any questions or need any additional information. Sincerely, McGILL ASSOCIATES, P.A. Brad Johnson, P.E. Project Manager I:\Projects\2016\16.00164\Misc\Stormwater\May 2018 Response to NCDEQ Comments Type of application: Initials 1 2 3 4 Only complete application packages will be accepted and reviewed. A complete package includes all of the items in the checklist below. Add any comments, and indicate the page or plan sheet number where the following information can be found. Please indicate that you have provided the following required information by initialing in the space provided next to each item. Item 6 5 i. Drainage area boundaries (included in the main set of plans, not as a separate document). j. Existing and proposed maintenance access routes, utility easements, drainage easements, public rights-of-way etc. c. Dimensioned property/project boundary with bearings & distances. f. Site layout showing all built-upon areas, drainage features, stormwater collection systems (inlets, outlets, swales, pipe elevations, slopes and diameters), and SCMs at ultimate build-out. g. Existing contours, proposed contours, spot elevations, and finished floor elevations. h. Existing drainage (including off-site), drainage easements, pipe sizes, runoff calculations. c. A table of elevations, incremental volumes and accumulated volumes (if applicable). a. Dimensions, side slopes, length to width ratios and elevations with a benchmark for clean-out if appropriate. b. All applicable conveyance devices, including: bypass structure, pretreatment area, flow distribution device, underdrains, outlet device, outlet dissipater and level spreader. Two sets of sealed, signed, & dated full-sized plan details of each SCM (or typical if appropriate) in both plan view and cross-section at a scale of 1" = 30' or larger, including: k. A construction sequence that shows how the SCMs will be protected from sediment until the entire drainage area is stabilized. d. Specifications for applicable materials, such as planting media, aggregate, sod, underdrains, outlet devices, etc. Two sets of sealed, signed, & dated full-sized plans of the entire site at a readable scale, including: Brad Johnson, PE, McGill Associates Part I: Submittal Checklist Application New Permit Notes / Comments Original and one copy of this application form (all worksheets) and the permit application fee. For applications submitted to the DEMLR regular permitting program, the fee is $505 payable to NCDENR. For Express Review, click on the link below for information and fee schedule. Contact the appropriate regional office Express Review Coordinator to schedule the required pre-application meeting. A USGS map identifying the site location. If the receiving stream is reported as class SA or the receiving stream drains to and is within 1/2 mile of SA waters, then include the 1/2 mile radius on the map. Jo Ellen Ammons Fieldhouse for Mars Hill University Mars Hill, NC MADISON County A copy of the most current property deed. Two copies of additional calculations (as needed). Sealed, signed and dated. Click here for Express Permitting info d. The boundaries of all surface waters, regulatory flood zones, and protected riparian buffers or a note on the plans that none exist. b. Location map with street names and SR numbers, legend, north arrow, scale. a. Project name, engineer and firm, revision number and dates. e. The boundaries of all vegetated or protected riparian buffers. STORM-EZ Version 1.4 Application 5/16/2018 Page 1 of 13 8 9 10 11 12 d. A one-time fertilizer specification to establish plants if necessary. A copy of the proposed deed restrictions protecting the SCMs and limiting the built-upon area so that it does not exceed the capacity of the SCM(s) or the high density threshold (as applicable). Two sealed, signed, & dated planting plans for each SCM (or typical) at a scale of 1" = 20' or larger, as applicable, including: a. The locations of each species and a planting detail. b. A table summarizing the size, spacing and total quantity of each plant species that should be used. A copy of the lease agreement or pending sales agreement if applicable. NC Dept. of the Secretary of State A soils report based on field evaluation indicating the SHWT elevations within the footprints of the proposed SCM(s). Provide a map of the boring locations with the existing elevations and boring logs. For infiltration SCMs, the report shall include the soil type, infiltration rate and method for determining the infiltration rate. Soils information shall be signed and sealed by a licensed soil scientist. A copy of the signed and notarized operation and maintenance (O & M) agreement. 7 For corporations and limited liability corporations (LLC): Documentation from the NC Secretary of State or other official documentation, which supports the titles and positions held by the persons listed in the Contact Information section. The corporation or LLC must be listed as an active corporation in good standing with the NC Secretary of State, otherwise the application will be returned. NCDENR Deed Restriction Forms c. The source nursery for the plants. STORM-EZ Version 1.4 Application 5/16/2018 Page 2 of 13 1.00 1.39 1.88 2.22 2.66 3.79 4.48 5.03 5.58 Highlighted Storm is Design Storm 32.50 acres 1.04 acres 0.00 acres 59% 0.00 acres Complete the breakdown of impervious area for the project No NOTE: Please use the Storm-EZ calculation sheets to document the stormwater design and create the O&M Agreement. Discrete SCS Method, Pre - PostCalculation Method Entire Site Impervious Surface Area Offsite Drainage Area (sf) Stream Index Number Stream Class Receiving Stream name Basin Information Future (sf) Off-site (sf) Existing BUA (sf) 45,264Total 3,817 Other On-Site (sf) 17,535 12,197 0 On-Site Parking (sf) On-Site Sidewalks (sf) On-Site Buildings/Lots (sf) On-Site Streets (sf) 11,715 0 Proposed Impervious Area (sf) % Impervious Area (total) 0 45,264 59% Total Drainage Area On-Site Drainage Area (sf) 6-96-12 76,835 76,835 Gabriel Creek C Use Worksheet Data? Total Property Area Total Coastal Wetlands Area Total Surface Water Area Depth (inches) First Flush / WQV First Flush / WQV P90 P95 50-yr, 24-hr Design Storm: Asheville 1-yr, 24-hr Jo Ellen Ammons Fieldhouse for Mars Hill University Mars Hill, NC MADISON County French Broad River Basin RAINFALL & CALCULATION DATA Rainfall Source: Project County: Project City: MADISON Mars Hill Asheville 100-yr, 24-hr PROJECT INFORMATION Total Impervious Area Project % impervious area ALL AREAS ARE IN SQUARE FEET 0 0 Entire Site 2-yr, 24-hr Storm Event 10-yr, 24-hr 25-yr, 24-hr(Minimum Design Storm = P90 for non-SA, 1-yr, 24-hr for SA) Loaded Rainfall: STORM-EZ Version 1.4 Project Data 5/16/2018 Page 5 of 13 1 of 1 Pre-Development Land Use: HSG CN % A 39 75.72% A 98 24.28% Note: Enter BUA Draining to Permeable Pavement Below HSG 0.00 0.00% 1.76 24.28% Existing Permeable Pavement (Infiltration): Pavement Area Additional BUA Soil Infiltratio n Rate Gravel Void Space Total Gravel Depth Orifice Dia. Orifice Height (sf) (sf) (in/hr) (%) (in) (in) (in) 100 DSD PAW Dgr (in) (%) (in) (sf) (acres) 150 1.00 0.00 1.76 acres 0.00 acres 0.00 acres 0.00 acres 0.00 acres 1.76 acres Pre-Development SCMs: Imp. Open (sf) (sf) (cf) HSG 18657 58178 200 Rainfall Volume =1.76 cf Natural Infiltration & ET =-1.43 cf Disconnected Impervious Surfaces =0.00 cf SCM Infiltration =0.00 cf Permeable Pavement Infiltration =0.00 cf Green Roof ET =0.00 cf Post Filtration Discharge =0.00 cf Total Runoff Reduction =-1.43 cf Treated SCM Outflow =0.00 cf Untreated Surface Runoff =0.34 cf D.S. BMP SCM Type Has Synthetic Liner? Permeable Pavement + Additional BUA: Green Roofs : 0 Existing Green Roofs: HSG SCM # Area DS SCM # 0 Downstream SCM Description Total Site Area: Land Use Summary: Description Preserved Coastal Wetlands : Notes Drainage Area 76,835 1.76 % Imp Area (sf.) WQ Volume Provided Area (ac.)Area (sf.) Subtotal: User Defined Drainage Areas:Comp. CNDescription Area 1.34Pasture or Open Space 58,178 18,657 Mars Hill, NC MADISON County French Broad River Basin PRE-DEVELOPMENT LAND USE CALCULATIONS Drainage Area # (sf)Land-use (acres) 0.43Impervious Jo Ellen Ammons Fieldhouse for Mars Hill University Subtotal: 76,835 acre-inches = Design Storm Runoff Fate Summary: Runoff Reduction Components: acre-inches = 6,403acre-inches = SCM # SCM # From Land Use Tables: 76,835 Preserved Surface Waters & Non-Coastal Wetlands : BUA % acre-inches = acre-inches = acre-inches = acre-inches = acre-inches = acre-inches = SCM Treatment: acre-inches =1,230 The Pre-Development project area contains 18657 sf of built upon area, resulting in an overall density of 24.28%. 0 0 0 -5,173 -5,173 0 0 0 76,835 STORM-EZ Version 1.4 Pre-Development 5/16/2018 Page 6 of 13 1 of 1 Permeable Pavement: Infiltration Rate Void Space Total Gravel Depth Orifice Dia. Orifice Height (sf) (acres) (sf) (acres) (in/hr) (%) (in) (in) (in) 500 0.00 0.00 No DSD PAW Dgr (in) (%) (in) (sf) (acres) 600 1.00 0.00 No Residential Lot CN Calculator (Excluding R/W and dedicated open spaces): Max Imp / Lot Woods / Lot (ac.) (sf) (sf) 0.00 Remaining Land Use: HSG CN (sf) (acres) % A 39.0 31,571 0.72 41.09% A 98.0 45,264 1.04 58.91% N/A 0 0.00 0.00% N/A 0 0.00 0.00% 76,835 1.76 100.00% Land Excluded, or Partially Excluded, from Volume Calculations:(sf.) (ac.) 00.00 00.00 76,835 1.76 Rainfall Volume =1.76 cf Natural Infiltration & ET =-0.94 cf Disconnected Impervious Surfaces =0.00 cf SCM Infiltration =-0.53 cf Permeable Pavement Infiltration =0.00 cf Green Roof ET =0.00 cf Post Filtration Discharge =0.00 cf Total Runoff Reduction =-1.47 cf Treated SCM Outflow =0.00 cf Untreated Surface Runoff =0.29 cf Pre-Development Runoff =0.34 cf Difference =-0.05 cf Area Open Space / Lot (sf) 6,403 acre-inches = acre-inches =-175 acre-inches =1,230 The Post-Development project area contains 45264 sf of built upon area, resulting in an overall density of 58.91%. acre-inches = 0 acre-inches =0 acre-inches = 0 SCM Treatment: 1,055 acre-inches = acre-inches = acre-inches = acre-inches = -3,420 acre-inches = 0 Area Runoff Reduction Components: Design Storm Runoff Fate Summary: Jo Ellen Ammons Fieldhouse for Mars Hill University Mars Hill, NC MADISON County French Broad River Basin Detention Check Has Synthetic Liner? Infiltration Check POST-DEVELOPMENT LAND USE CALCULATIONS Pvmt Type SCM # -1,929 0 -5,348 acre-inches = Total Site Area: Surface Waters & Non-Coastal Wetlands : Green Roofs : Coastal Wetlands : Lot Area Open Space (Managed Open Space) Green Roofs: # of Lots Land-Use Impervious Permeable Pavement + BUA: Sub-Total: HSG Avg Lot Size Pavement Area % Imp.(sf.) Down- stream SCM Additional BUA SCM # Downstream SCM # Drainage Area # Retrofit? Comments STORM-EZ Version 1.4 Post Development 5/16/2018 Page 7 of 13 1 of 1 Impervious (sf) 45,264 (cf) (cf) (cf) (cf) (cf) (cf) 700 Bio. Cell Bioretention w/ IWS A 32,345 71% 77%1015 2132 2132 1929 0 0 111% Rainfall Volume =1.76 acre-inches =cf Natural Infiltration & ET =-0.94 acre-inches = cf Disconnected Impervious Area =0.00 acre-inches = cf SCM Infiltration =-0.53 acre-inches = cf Permeable Pavement Infiltration =0.00 acre-inches = cf Green Roof ET =0.00 acre-inches = cf Post Filtration Discharge =0.00 acre-inches = cf Total Runoff Reduction =-1.47 acre-inches =cf SCM Treatment: Treated SCM Outflow =0.00 acre-inches =cf Untreated Surface Runoff =0.29 acre-inches =cf 0.34 acre-inches =cf -0.05 acre-inches =cf Down- stream SCM # Drainage Area Inflow Volume -175 -5,348 -1,929 0 6,403 Pre-Development Runoff = 0 1,055 71% of total impervious area. 77% of total pervious area. Runoff Reduction Components: -3,420 32345 sf impervious area entered compared to 45264 sf total impervious. 1,230 Warnings: Design Storm Runoff Fate Summary: The Post-Development project area contains 45264 sf of built upon area, resulting in an overall density of 58.91%. 0 0 **VOLUME MATCHING ACHIEVED** Difference = 0 24283 sf open space entered compared to 31571 sf total open space. Pervious (sf) 31,571 Jo Ellen Ammons Fieldhouse for Mars Hill University Mars Hill, NC MADISON County French Broad River Basin Enter only runoff volume below that will be infiltrated or drawn down over 2 to 5 days. Additional volume provided in devices should not be entered in this worksheet. Drawdown time requirement applies to all storm events. Drainage Area # PROPOSED SIPs & STRUCTURAL RUNOFF VOLUME CONTROLS Offsite Impervious Area Treated Infiltration & ET 0 sf Total Inflow Volume 24,283 % of Total Impervious Area % of Total Pervious Area Storage Volume Name / Location Contributing Area HSG STORMWATER CONTROL MEASURES % of SCM Volume Utilized Post Filtration Outflow Treated Outflow Type of Device SCM # STORM-EZ Version 1.4 Stormwater Controls 5/16/2018 Page 8 of 13 1 of 1 First Flush Storm - Rainfall Depth = 1 inch The"Fate of Rainfall" charts display the hydrologic processes to which rainfall volumes are subjected based on the combinations of land use, soil type, and stormwater controls entered by the user. The charts are designed to display the stormwater plan in a form which illustrates changes to the hydrologic cycle which result from urbanization and various stormwater management strategies. Mars Hill, NC MADISON County French Broad River Basin First Flush Jo Ellen Ammons Fieldhouse for Mars Hill University Compliance Storm = First Flush Storm - Rainfall Depth = 1 inch Drainage Area # FATE OF RAINFALL Select Storm: VOLUME MATCHING SCALE Volume Matching Threshold Basic Treatment Threshold BASIC TREATMENT SCALE 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Infiltration and ET ‐ 5349 cf Treated Outflow from BMPs ‐ 0 cf Untreated Surface Runoff ‐ 1055 cf% of Total Rainfall VolumePost Development Fates Post Filtration Outflow ‐ 0 cf Other Infiltration by BMPs ‐ 1929 cf Permeable Pavement Infiltration ‐ 0 cf Disconnected Impervious Infiltration ‐ 0 cf Green Roof Evapotranspiration ‐ 0 cf Infiltration and ET ‐ 3420 cf 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Infiltration and ET ‐ 5173 cf Treated Outflow from BMPs ‐ 0 cf Untreated Surface Runoff ‐ 1230 cf% of Total Rainfall VolumePre Development Fates Post Filtration Outflow ‐ 0 cf Other Infiltration by BMPs ‐ 0 cf Permeable Pavement Infiltration ‐ 0 cf Disconnected Impervious Infiltration ‐ 0 cf Green Roof Evapotranspiration ‐ 0 cf Infiltration and ET ‐ 5173 cf FATE OF RAINFALL GRAPHS STORM-EZ Version 1.4 Rainfall Fate Graph 5/16/2018 Page 9 of 13 1 of 1 TIME OF CONCENTRATION CALCULATIONS: Pre-Development Length (ft) Slope (ft/ft)Tt (hrs) 400 0.015 0.06 Length (ft) Slope (ft/ft) n-value Flow Area (ft2)Tt (hrs) Channel Flow: Channel Flow: Pre-development Tc =5.00 min (Minimum 5 minutes) Post Development Length (ft) Slope (ft/ft)Tt (hrs) 60 0.015 0.02 Length (ft) Slope (ft/ft) n-value Flow Area (ft2)Tt (hrs) Channel Flow:380 0.01 0.012 1.5 0.01 Channel Flow: Post-development Tc =5.00 min (Minimum 5 minutes) ADJUSTED CURVE NUMBER CALCULATIONS: Pre-Development F.F. P90 P95 1-Yr 2-Yr 10-Yr 25-Yr 50-Yr 100-Yr Rainfall (in) = 1.00 1.39 1.88 2.22 2.66 3.79 4.48 5.03 5.58 Q*(in) =0.19 0.28 0.40 0.48 0.59 0.88 1.11 1.32 1.55 CNadj =86 82 78 75 71 65 62 60 59 Post Development F.F. P90 P95 1-Yr 2-Yr 10-Yr 25-Yr 50-Yr 100-Yr Rainfall (in) = 1.00 1.39 1.88 2.22 2.66 3.79 4.48 5.03 5.58 Q*(in) =0.16 0.39 0.67 0.87 1.13 1.80 2.24 2.61 2.98 CNadj =85 85 84 83 82 79 78 77 76 PEAK FLOW CALCULATIONS: F.F. P90 P95 1-Yr 2-Yr 10-Yr 25-Yr 50-Yr 100-Yr Pre-Development Q* (in) 0.19 0.28 0.40 0.48 0.59 0.88 1.11 1.32 1.55 qu (csm/in)809.52 931.69 931.69 931.69 931.69 931.69 931.69 931.69 931.69 Q (cfs) 0.43 0.73 1.03 1.24 1.52 2.27 2.86 3.39 3.98 Post Development Q* (in) 0.16 0.39 0.67 0.87 1.13 1.80 2.24 2.61 2.98 qu (csm/in)809.52 931.69 931.69 1165.98 1165.98 1165.98 1165.98 1165.98 1165.98 Q (cfs) 0.37 1.00 1.73 2.80 3.63 5.80 7.21 8.38 9.58 -14.0% 37.0% 68.0% 125.8% 139.7% 155.5% 152.5% 147.2% 141.0% Unpaved French Broad River Basin ADDITIONAL CALCULATIONS Jo Ellen Ammons Fieldhouse for Mars Hill University Mars Hill, NC MADISON County Shallow Flow: Drainage Area # Surface Cover Wetted Perimeter (ft) Sheet Flow: Paved or Bare Soil Surface Cover Analysis Area = 1.76 Acres (0.003 sq. miles) Wetted Perimeter (ft) 2.4 Sheet Flow: Shallow Flow: **Note: To decrease Post-development peak flows - increase storage volume being drawdown or infiltrated or lengthen post- development time of concentration. See LID HELP for more information. Analysis Area = 1.76 Acres (0.003 sq. miles) Sheet Flow: Shallow Flow: Sheet Flow: Shallow Flow: STORM-EZ Version 1.4 Peak Flow Calcs 5/16/2018 Page 10 of 13 BIORETENTION CELL1Drainage area numberEntire SiteTotal coastal wetlands area (sq ft)N/A - Parking / driveway (sq ft)17535 sfTotal surface water area (sq ft)N/A - Sidewalk (sq ft)12197 sfTotal drainage area (sq ft)76835 sf - Roof (sq ft)11715 sfBUA associated with existing development (sq ft) 18657 sf - Roadway (sq ft) sfProposed new BUA (sq ft)45264 sf - Other, please specify in the comment box below (sq ft) 3817 sfPercent BUA of drainage area59 percentTotal BUA (sq ft)45264 sfDesign rainfall depth (in)1.0 inMinimum volume required (cu ft) 1753 cf***Design volume of SCM (cu ft)1015 cf#1 Is the SCM sized to treat the SW from all surfaces at build-out? Yes#7 If applicable, with the SCM be cleaned out after construction?Yes#2 Is the SCM located on or near contaminated soils? No#8 Does the mainetenance access comply with General MDC (8)?Yes#3 What are the side slopes of the SCM (H:V)? 4:1#9 Does the drainage easement comply with General MDC (9)?No#3 Does the SCM have retaining walls, gabion walls or other engineered side slopes? No#10 If the SCM is on a single family lot, does the plat comply with General MDC (10)?#4 Are the inlets, outlets, and receiving stream protected from erosion (10-year storm)? Yes#11 Is there an O&M Agreement that complies with General MDC (11)?Yes#5 Is there a a bypass for flows in excess of the design flow?Yes#12 Is there an O&M Plan that complies with General MDC (12)?Yes#6 What is the method for dewatering the SCM for maintenance?Other#13 Was the SCM designed by an NC licensed professional?Yes#1 SHWT elevation (fmsl)< 2220.5 ft. #6 Percentage of medium to coarse washed sand by volume 75-85%#1 Bottom of the bioretention cell (fmsl) 2225.32 ft. #6 Percentage of fines (silt and clay) by volume 8-15%#1 Distance from bottom to SHWT (feet) > 2 ft. #6 Percentage of organic matter by volume 5-10%#2 Surface area of the bioretention cell (square feet) 1015 sf#6 Type of organic materialPine bark fines#2 Design volume of the bioretention cell (cubic feet) 1015 cf#7 Phosphorus Index (P-Index) of media (unitless) <50#2 Ponding depth of the design storm (inches) 12 in#8 Will compaction be avoided during construction?Yes#3 Is the bioretention cell used for peak attenuation? No#9 Will cell be maintained to a one inch/hour standard? Yes#3 Depth of peak attenuation over planting surface (in)12 in #10 Describe the planting plan:#3 Height of peak attenuation outlet above the planting surface (in)12 in#4 Infiltration rate of the in situ soil (inch/hour)See Note Below#4 Diameter of the underdrain pipes (if applicable)6 in#4 Does the design include Internal Water Storage (IWS)? Yes #11 Depth of mulch, if applicable (inches) N/A#4 if so, elevation of the top of the IWS (fmsl) 2227 ft #11 Type of mulch, if applicableN/A#4 Elevation of the planting surface (fmsl) 2228.5 ft #12 How many clean out pipes are being installed? 2#5 Will the cell contain trees and shrubs? No#12 Briefly describe the pretreatment that will be used:#5 Media depth (inches)30 inJo Ellen Ammons Fieldhouse at Mars Hill UniversityTHE DRAINAGE AREABIORETENTION CELL MDC FROM 02H .1052***Minimum volume required comes from Storm-EZ tool (2983 cf of runoff at postdevelopment conditions minus 1230 cf of runoff at predevelopment conditions). Per the USGS Soil Survey the in-situ soils are categorized as somewhat excessively drained and hydrologic soil group A.Break down of BUA in the drainage area (both new and existing):COMPLIANCE WITH THE APPLICABLE STORMWATER PROGRAMStormwater program(s) that apply (please specify):NCDEQ Phase II MSI or UA Post Construction StormwaterGENERAL MDC FROM 02H .1050ADDITIONAL INFORMATIONPlease use this space to provide any additional information about this bioretention cell that you think is relevant to the review:The bioretention cell will be soded with a non-clumping, deep rooted species that is NOT grown from a soil with an impenetrable layer (like clay).No pretreatment devices were designed as part of this bioretention cellBioretention11:39 PM 5/16/2018 2 inches per hour q = K * dH/L 2 = K = hydraulic conductivity of media (inch per hour) 3 = dH = change in head (height of water) (ft) q = 2.4 inch per hour per unit area 2.5 = L = thickness of soil layer (ft) Q = q * A/12 inches per foot/3600 seconds Q = flow rate (cfs) 1015 = A = surface area Q = 0.056389 D = 16 * (Q * n / (s^0.5))^(3/8) D = diameter of pipes (inches) D = 6.636722 0.563889 = Q = flow rate w/ 10x safety factor (cfs) 0.012 = n = manning coefficient 0.005 = s = slope of pipe (assume 0.5%) Number of 6" Pipes Required in the Underdrain per NCDEQ Stormwater Design Manual = 2 reference:http://www.bae.ncsu.edu/stormwater/PublicationFiles/DesigningRainGardens2001.pdf Infiltration Rate of Media (1‐6 inches per hour required, 1‐2 inches per hour preferred)