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Home My WebLink AboutSW5210304_Report (SW)_20210617V VELYjS S 7PDRIAG7 . Y 0 TjJ 7 E YOUNGSVNFLLE9 TRANK L�,N COUNTY, NORTH (C-AFO)LINDA STORMWATER MANAGEMENT PLAN DRAWING No. D- 1240 "%%jlllll1jj" CAR o S Sld j SEAL 387464�J- - Al- 14EN % J- DANTZLER WITHERS, P.E. MARCH 18 p 202 1; REV. MAY 24, 202 1; REV. JUNE 8, 202 1; REV. JUNE 16P 2021 DEVELOPER C4-YS, LLC DBA YOUNGSVILLE STORAGE 121 W TRADE STREET, STE. 2550 CHARLOTTE, NC 28202 91 4RKOOF CONSULTING GROUPPLLC 2755-B CHARLES BLVD GREENVILLE, NC 27858 (252) 558-0888 NCBELS LICENSE No. P- 1199 YOUNGSVILLE MINI STORAGE STORMWATER MANAGEMENT PLAN YOUNGSVILLE, FRANKLIN COUNTY, NORTH CAROLINA MARCH 2021 LOCATION: The proposed project is an expansion of the existing Youngsville Storage mini storage facility located between Hillsboro Street and North College Street in Youngsville, North Carolina. The expansion to the north and west will involve a recombination of adjacent parcels, resulting in a site with a total area of approximately 8.7 acres. The proposed development is not subject to a local stormwater program and will be permitted under the State's stormwater program. The project is roughly evenly divided between the Tar -Pamlico and Neuse River basins and is subject to the associated rules for those basins. DESCRIPTION: The limits of disturbance for this project are 7.6 acres. The property has historically been vacant land (mowed pasture) with a small residential component. The adjacent land to the north will remain vacant meadow, and the site will be bound on the east by residential and institutional uses and on the west by Park Avenue (NC-96, US-1A). Soils onsite consist of Cecil sandy loam (CaB and CaQ as shown on the Franklin County Soild Survey. PROPOSED PROJECT: The project includes construction of three new self -storage building and an outdoor gravel storage area. There are also appurtenant improvements, including construction of a new turn lane, utility improvements, and drive aisles. STORMWATER MANAGEMENT REQUIREMENTS: Although within the Town of Youngsville limits, a Phase 11 Post -Construction Stormwater area, the proposed system is subject to State permitting. The stormwater management has been designed in accordance with State requirements. Runoff volume match is provided by two infiltration basins. The site is also subject to Nitrogen and Phosphorus loading requirements set forth in the Tar -Pamlico and Neuse river basin rules. The project meets nutrient loading requirements under both basins' rules by virtue of achieving runoff volume match. The following sets of calculations and supporting information are included for demonstrating compliance with the pertinent regulations: 0 Runoff Volume Match Calculations for the portion of the site falling within the Neuse River Basin 0 Runoff Volume Match Calculations for the portion of the site falling within the Tar -Pamlico River Basin Calculations showing the treatment volume of each infiltration basin is drawn down within the required time Rip rap apron sizing calculations Reports of soils investigations performed for the project YOUNGSVILLE STORAGE YOUNGSVILLE, FRANKLIN COUNTY, NORTH CAROLINA STORMWATER MANAGEMENT PLAN DRAWING No. D- 1240 STORMWATER CONTROL MEASURE CALCULATIONS Ark Consulting Group, PLLC JOB 19006 - Youngsville Storage 2755-B Charles Boulevard DATE May-21 Greenville, NC 27858 CALCULATED By TG N/J DVV 252-558-0888 CHECKED BY J DVV Annual Runoff Volume Match (Neuse River Basin) GOAL: Compute the pre -development annual runoff volume and post -development annual runoff volume for the portion of the project that falls within the Neuse River Basin. The net increase shall be no more than 10% from the pre -development condition. Units Symbols & Governing Equation Drainage Basin Summary Total Site Area (Parcel+All New Impervious) 173319 sf kite Roof Impervious 64529 sf Aroof Transportation Impervious 53759 sf Atra- Total Impervious Area 118288 sf Amp—ious Percent Impervious 68 % (Amper,�ous / Asite)*l 00 Impervious Fraction 0.68 IA Constants Across Site P (Neuse Station, retrieved 5/6/21 from hftps://ncdenr.maps.arcgis.com/apps/webappviewer/ind Average Annual Precipitation 45.76 in ex.html?id=633ce7fOa6la44f9997ff257e25b9a8l) Fraction of All Storm Events that Produce Runoff 0.9 Pi Pre-DeveloDment Annual Runoff Volume Average Annual Precipitation 45.76 in P Pi 0.90 Pi Impervious Area 21222 sf Pervious Area 152097 sf Tota I Catch me nt Area 173319 sf A Impervious Fraction 0.12 la Runoff Coefficient 0.16 Rv=0.05+0-9*la Runoff Volume 95292 Gf V=Pj*Rv*A*(P/12) 10% normally; 5% allowable increase per SA waters Allowable Increase 1.10 requirements. Maximum Runoff Volume 104821 cf Post-DeveloDment Annual Runoff Volume Average Annual Precipitation 45.76 in P Pi 0.90 Pi Impervious Area 118288 sf Pervious Area 55031 sf Tota I Catch me nt Area 173319 sf A Impervious Fraction 0.68 la Runoff Coefficient 0.66 Rv=0.05+0-9*la Runoff Volume 395110 cf V=Pj*Rv*A*(P/12) Required Treatment Volume 290288 cf Ark Consulting Group, PLLC JOB 19006 - Youngsville Storage 2755-B Charles Boulevard DATE May-21 Greenville, NC 27858 CALCULATED By TG N/J DVV 252-558-0888 CHECKED BY J DVV Annual Runoff Volume Match (Neuse River Basin) Annual Runoff Volume Treated - Infiltration Basin #1 Average Annual Precipitation 45.76 in P pi 0.90 Pi Impervious Area 90693 sf Pervious Area 20074 sf Tota I Catch me nt Area 110767 sf A Impervious Fraction 0.82 la Runoff Coefficient 0.79 Rv=0.05+0-9*la 100% Design Volume 7264 cl' Treatment Volume Provided 14230 cl' TV, Minimum of 200% DV or Actual DV SCM Size 1.959 TV/100%DV Annual Runoff Volume to SCM 299140 cf V=Pj*Rv*A*(P/12) % Annual Runoff Treated 0.974 Y=0.2231x'3-1.141x'2+1.9953x-0.2332 Annual Runoff Volume Treated 291385 cf Ark Consulting Group, PLLC JOB 19006 - Youngsville Storage 2755-B Charles Boulevard DATE May-21 Greenville, NC 27858 CALCULATED By TG N/J DVV 252-558-0888 CHECKED BY J DVV Infiltration Basin 1 (Neuse River Basin) Infiltrating Stormwater Control Measures Drawdown Time GOAL: Compute the required surface area for an infiltration SCM. The SCM must infiltrate the design volume in less than 72 hours Units Symbols & Governing Equations Top Contour Area 11529 sf Top Contour Elevation 460.00 ft Bottom Contour Area 9552 sf Bottom Contour Elevation 458.65 ft Designed Storage Volume 14230 cu ft DV (calculated via average -end -area method) Desired Drawdown Time 72.0 hours T (<72 hours) Surface Area Safety Factor 2.0 FS, min. 2 recommended Hydraulic Conductivity of Soil 0.50 in/hr K Total Designed Surface Area 9552 sq ft SA Designed Drawdown Time 71.5 hours T = (FS�DW`12)/(K�SA) Notes: Boring 1-2 in 7/17/2020 soils report indicated infiltration rate of 0.5 in/hr. Ark Consulting Group, PLLC JOB 19006 - Youngsville Storage 2755-B Charles Boulevard DATE May-21 Greenville, NC 27858 CALCULATED By TG N/J DVV 252-558-0888 CHECKED BY J DVV Annual Runoff Volume Match (Tar -Pamlico River Basin) GOAL: Compute the pre -development annual runoff volume and post -development annual runoff volume for the portion of the project that falls within the Tar -Pamlico River Basin. The net increase shall be no more than 10% from the pre -development condition. Units Symbols & Governing Equation Drainage Basin Summary Total Site Area (Parcel+All New Impervious) 210476 sf kite Roof Impervious 8983 sf Aroof Transportation Impervious 107628 sf Atra- Total Impervious Area 116611 sf Amp—ious Percent Impervious 55 % (Amper,�ous / Asite)*l 00 Impervious Fraction 0.55 IA Constants Across Site P (Neuse Station, retrieved 5/6/21 from hftps://ncdenr.maps.arcgis.com/apps/webappviewer/ind Average Annual Precipitation 45.76 in ex.html?id=633ce7fOa6la44f9997ff257e25b9a8l) Fraction of All Storm Events that Produce Runoff 0.9 Pi Pre-DeveloDment Annual Runoff Volume Average Annual Precipitation 45.76 in P Pi 0.90 Pi Impervious Area 25673 sf Pervious Area 184803 sf Tota I Catch me nt Area 210476 sf A Impervious Fraction 0.12 la Runoff Coefficient 0.16 Rv=0.05+0-9*la Runoff Volume 115416 cf V=Pj*Rv*A*(P/12) 10% normally; 5% allowable increase per SA waters Allowable Increase 1.10 requirements. Maximum Runoff Volume 126958 cf Post-DeveloDment Annual Runoff Volume Average Annual Precipitation 45.76 in P Pi 0.90 Pi Impervious Area 116611 sf Pervious Area 93865 sf Tota I Catch me nt Area 210476 sf A Impervious Fraction 0.55 la Runoff Coefficient 0.55 Rv=0.05+0-9*la Runoff Volume 396306 cf V=Pj*Rv*A*(P/12) Required Treatment Volume 269348 cf Ark Consulting Group, PLLC JOB 19006 - Youngsville Storage 2755-B Charles Boulevard DATE May-21 Greenville, NC 27858 CALCULATED By TG N/J DVV 252-558-0888 CHECKED BY J DVV Annual Runoff Volume Match (Tar -Pamlico River Basin) Annual Runoff Volume Treated - Infiltration Basin #2 Average Annual Precipitation 45.76 in P pi 0.90 Pi Impervious Area 96107 sf Pervious Area 53707 sf Tota I Catch me nt Area 149814 sf A Impervious Fraction 0.64 la Runoff Coefficient 0.63 Rv=0.05+0-9*la 100% Design Volume 7832 cl' Treatment Volume Provided 8844 cl' TV, Minimum of 2x 100% DV or Actual DV SCM Size 1.129 TV/100%DV Annual Runoff Volume to SCM 322563 cf V=Pj*Rv*A*(P/12) % Annual Runoff Treated 0.886 Y=0.2231x'3-1.141x'2+1.9953x-0.2332 Annual Runoff Volume Treated 285864 cf Ark Consulting Group, PLLC JOB 19006 - Youngsville Storage 2755-B Charles Boulevard DATE May-21 Greenville, NC 27858 CALCULATED By TGN/J DVV 252-558-0888 CHECKED BY J DVV Infiltration Basin 2 (Tar -Pamlico River Basin) Infiltrating Stormwater Control Measures Drawdown Time GOAL: Compute the required surface area for an infiltration SCM. The SCM must infiltrate the design volume in less than 72 hours. Top Contour Area Top Contour Elevation Bottom Contour Area Bottom Contour Elevation Designed Storage Volume Desired Drawdown Time (<72 hours) Surface Area Safety Factor Hydraulic Conductivity of Soil Designed Surface Area - Infiltration Basin Designed Drawdown Time Units Symbols & Governing Equations 7721 sf 443.75 ft 6429 sf 442.5 ft 8844 cu ft DV (calculated via average -end -area method) 72.0 hours T 2.0 FS, min. 2 recommended 0.50 in/hr K 6429 sq ft SA 66 hours T = (FS-DV-12)/(KSA) Notes: Boring 1-1 in 2/24/2021 soils report indicated infiltration rate of 0.5 in/hr. YOUNGSVILLE STORAGE YOUNGSVILLE, FRANKLIN COUNTY, NORTH CAROLINA STORMWATER MANAGEMENT PLAN DRAWING No. D- 1240 EROSION CONTROL MEASURE CALCULATIONS 2 �L 0 o 7�� oq r� 't 't oq oq r� 4 4 o6 o6 o o o o o o o 2E u u u u u u u 0 0 m < u u E u