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Home My WebLink About20080851 Ver 1_More Info Received_20080708.. , Upton Engineering-Planning-Surveying May 8, 2008 Gaston County Natural Resource Department 1303 Cherryville Hwy Dallas, NC 28034 Re: Evergreen Landing Cox Road, Gaston County Erosion Control Plan Submission ?Y_ 9?51 JUL S 2008 DEW -WATER QUAUTY ft%*DS AND STOROATERORW-H Enclosed are the necessary materials for your review of the storm water management control plans for Evergreen Landing. To address the reasons for disapproval, please see below. After our discussion with obtaining the 85% TSS, we went back to the wet detention basin. Unfortunately, the size was not big enough to obtain 90%TSS and therefore the filter strip will remain. Also included this time is the Mosquito Control Plan and Landscape Plan as requested from the first submission. To address the Major Design Elements of wet detention basin: 1. C-factors have taken into account full build out to ensure proper size for the basin's lifetime. 2. All slopes are at most 3:1 3. Drainage Easements will be recorded with sufficient access down existing sewer easement. This has already been discussed with COG. 4. Basin is discharging across a filter strip over +30' long because it does not meet the 90%TSS. 5. Note 7 on erosion control plan states that the basin must be restored to original capacity upon completion of grading. 6. Calculations in the Permanent wet detention basin show that storage volumes began at 725 which is the top of the perm. pool elev. 7. Calculations in the Permanent wet detention basin show that the 1-inch storm is completely drawn down by the orifice in 2.3 days 8. The pool depth is 3' deep across the entire pond. 9. With a impervious area of 2.72 acres and a drainage area of 5.81, Percent Impervious cover is 46.8. Using table 10.1 with 3.0 average depth gives 2.06%. This requires a surface area of 5,213.52 Sq. Ft. Proposed pond has a surface area at 725 of 6,051.88 Sq. ft. 10. The inlet and outlet are on opposite ends to ensure that short circuit will not occur. 11 &17. A forebay has been added to the basin and contains 20% of permanent pool volume. 12. Side slopes shall be stabilized with vegetation as shown on landscape plans 13. All slopes in the basin are at most 3:1. 14. The basin has an additional foot of storage which is to be used for perm. sediment storage. 15. The BMPs location will not produce any adverse impacts on water levels in adjacent wetlands. 16. The basin has a 10:1 vegetated shelf with the center of the shelf being at elev. 725 making the outside edge 6 inches above normal pool depth and the inside edge 6 inches below. 18. Calculations in the Permanent wet detention basin show that freeboard on the 100-yr storm is 1.05 Ras Creek Pkwy, Suite 2B Winston-Salem, NC 27103 336-723-2459 Fax: 336-761-1425 E-mail jsbeck n Quptoncompanies.com Please review this submittal and all related attachments and feel free to contact me if you have any further questions. Sincerely, Joshua S Beck, El Enclosures: Permanent Pond Calculations Maintenance Manual (during and after construction) & Mosquito Control Plan 2 Sets of Plans 3s Creek Pkwy, Suite 213 Winston-Salem, NC 27103 336-723-2459 Fax: 336-761-1425 E-mail isbeckAguptoncompanies.com Upton Engineering-Planning-Surveying 2200 Silas Creek Pkwy. Suite 26 Winston-Salem, N.C. 27103 336-723-2459 Evergreen Landing Apartments Cox Rd Gastonia, NC BMP #1 PERMANENT WET DETENTION BASIN 7/1/2008 APPROVED WITH Developer Evergreen Development Co. LLC 2717 Honeywind Court Fort Mill, S.C. 29708 336-399-8154 7 I FICATIO S 7OD12 '?Ntd d b1 GUPTON & ASSOCIATES P.A. 2200 Silas Crk. Pkwy. Suite 2-B Winston-Salem, N.C. 27103 OUTLET STRUCTURE SCHEMATIC MAX STAGE ELEV.: 726.30 MAX STAGE ELEV.: 726.54 MAX STAGE ELEV.: 727.32 MAX FLOW CFS: 3.70 MAX FLOW CFS: 0.04 MAX FLOW CFS: 9.05 MAX STAGE ELEV.: 728.05 MAX FLOW CFS: 21.62 Top of Dam 1.0' Min. 729.10 1.05 1.30 727.80 100Yr 728.05 --------------- ---- M' 10 Yr 727.32 ------------------------------ 1 .50 2 Yr 726.54 727.00 1 Yr 726.30 4'x 4' Perm. Pool 725.00 ------ 0 10: 66.00 ft 4.00 Outlet 722.00 1 15 in. 1.00% 721.34 721.00 l / Toe of Dar 722.00 GUPTON & ASSOCIATES P.A. 2200 Silas Crk. Pkwy. Suite 2-B Winston-Salem, N.C. 27103 Evergreen Landing Apartments STORMWATER DETENTION POND SUMMARY REPORT CONTOUR CONTOUR CONTOUR INCR. ACCUM. ELEV. AREA AREA VOL. VOL STAGE ft s ft) (acres) (Cu ft (Cu ft) ft 725.0 6,052.00 0.14 0 0 0 726.0 8,499.00 0.20 7,276 7,276 1 727.0 9,723.00 0.22 9,111 16,387 2 728.0 11,008.00 0.25 10,366 26,753 3 729.0 12,353.00 0.28 11,681 38,434 4 POND ELEVATIONS: PRIMARY SPILLWAY: Top of Dam Elevation: 729.10 Ft. Barrel Length: 66 Ft. Top of Emergency Spillway Elev.: 729.10 Ft. Barrel Size: 15 In. Emergency Spillway Elevation: 727.80 Ft. Barrel Slope: 1.00 % Top of Riser Elevation: 727.00 Ft. Riser Size: 4'x 4' Ft. Invert of Riser Elevation: 722.00 Ft. Bottom of Pond Elevation: 721.00 Ft. EMERGENCY SPILLWAY Bottom Width: 20 Ft. SUBMERGED ORIFICE OUTLET: Submerged Orifice Outlet Piping Size: Design Head, h: 4.00 In. 25.0 In. Maximum Release Rate: 2 Days Minimum Release Rate: 5 Days Maximum Hole Size: 0.008166 1.22 In. Dia. Minimum Hole Size: 0.003266 0.77 In. Dia. Submerged Orifice Size: 1.13 In. Dia. ANTI-FLOATATION SUMMARY: Riser Height: 5 Ft. Riser Weight: 4655.0 Lbs. Volume of Riser: 45.0 Cu.Ft. Exposed Barrel Length: 10 Ft. Volume of Exposed Barrel: 12.3 Cu.Ft. Weight of Water Displaced: 3575.52 Lbs. Saftey Factor (10%): 3933.07 Lbs. Concrete Required: NO REQ. C.F. = 0.00 C.Y. Riser Base Size Min.: Thickness: 2.00 Ft. 0.00 X 0.00 Riser Base Size Used: Thickness: 2.00 Ft. 7.00 X 7.00 GUPTON & ASSOCIATES P.A. 2200 Silas Crk. Pkwy. Suite 2-B Winston-Salem, N.C. 27103 Evergreen Landing Apartments STORMWATER MANAGEMENT DETENTION STRUCTURE SITE CONDITIONS AND INPUT DATA BASIN #1 Pre-Developed Rational Formula Runoff Coefficient, "C" Soil Grou Description C* Area acres Product of C x Area B Woodlands 0.28 5.81 1.6268 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Totals Weighted "C" Runoff Coefficient = 5.81 1.63 Post-Developed Rational Formula Runoff Coefficient, "C" 0.28 Soil Grou Descri lion C* Area (acres) Product of C x Area B Impervious 0.9 1.72 1.548 B Grassed Areas 0.35 3.13 1.0955 B Roofs 0.8 0.96 0.768 0 0 0 0 0 0 0 0 0 0 0 0 i otais Weighted "C" Runoff Coefficient = 5.57 3.41 0.59 *See table 8.03a "Reference made to "Erosion and Sediment Control Planning and Design Manual" State of N.C. GUPTON & ASSOCIATES P.A. 2200 Silas Crk. Pkwy. Suite 2-B Winston-Salem, N.C. 27103 Evergreen Landing Apartments STORMWATER MANAGEMENT DETENTION STRUCTURE SITE CONDITIONS AND INPUT DATA BMP #1 Site Data Total Site Area: Total Disturbed Area: Total Drainage Area Into Structure: Proposed BUA/Impervious Area: Proposed BUA/Impervious Area: Off-Site Drainage Area: Maximum Off-Site BUA/Impervious Area: Total BUA/Impervious Area Into Structure: Total BUA/Impervious Area Into Structure: Design Data Hydraulic Length: Hydraulic Height: Volumetric Runoff Coefficient, Rv: Overland Flow Runoff Factor Pre-Developed Runoff Coefficient, " C Post-Developed Runoff Coefficient, " C SCS Weighted Curve Number: Precipitation Depth , 2 yr. 24 hr. Storm: Precipitation Depth , 10 yr. 24 hr. Storm: Precipitation Depth , 100 yr. 24 hr. Storm: SCS Runoff Curve Number (CN) *See table 8.03a *See table 8.03a *See table 8.03b **See table **See table **See table 10.93 Acres 5.81 Acres 5.81 Acres 2.68 Acres 46.1 % 0 Acres 70 % 2.68 Acres 46.1 % 840 Feet 36 Feet 0.465 2 Factor 0.28 Factor 0.59 Factor 63 CN 3.32 Inches 4.79 Inches 7.08 Inches Soil Group Description CN Area (acres) Product of CN x Area B Impervious 98 1.72 168.56 B Grassed Areas 39 3.13 122.07 B Roofs 80 0.96 76.8 0 0 0 0 0 0 0 0 0 0 0 0 Weighted SCS Curve Number (CN) = 5.51 367.43 Totals 63.24 Evergreen Landing Apartments STORMWATER MANAGEMENT DETENTION STRUCTURE COMPUTED DESIGN DATA BMP #1 COMPUTED 1-YR. WATER QUALITY DATA Water Quality Volume (1-Inch Storm), WQv: 9,806.99 Cu.Ft. Water Quality Runoff Volume, Qa: 0.47 Inches Water Quality CN (using Qa): 93 CN Intial Abstraction, la: = 0.151 la/P(1") = 0.151 Qu (TR-55)= 875.00 csm/in Water Quality Peak Discharge, Qp: 3.7 cfs COMPUTED 2-YR. DATA Time of Concentration, Tc Intensity for 2 yr. Storm, I Peak Rate of Runoff, Tp Pre-Development Peak Flow, Qpre: Post-Development Peak Flow, Qpost : Soil Storage Volume, S Runoff Depth, Q* : COMPUTED 10-YR. DATA 5.87 Inches 0.57 Inches Time of Concentration, Tc 9.38 Min. Intensity for 10 yr. Storm, 1 5.93 In./hr. Peak Rate of Runoff, Tp : 17.29 Min. Pre-Development Peak Flow, Qpre: 9.65 cfs Post-Development Peak Flow, Qpost : 20.33 cfs Soil Storage Volume, S 5.81 Inches Runoff Depth, Q* : 1.39 Inches COMPUTED 100-YR. DATA Time of Concentration, Tc : 9.38 Min. Intensity for 100 yr. Storm, 1 8.30 In./hr. Peak Rate of Runoff, Tp 26.31 Min. Peak Runoff, Qp : 28.45 cfs Soil Storage Volume, S 5.87 Inches Runoff Depth, Q* : 2.96 Inches COMPUTED STORAGE REQUIREMENTS 3' Perm. Pool Permanent Water Quality Pool Surface Area to Drainage Area Ratio: 2.06 Ratio Permanent Water Quality Required Surface Area: (SA / DA) 5,213.52 S.F. Required Surface Area: (A =435 x 10-yr. Qp) 8,843.55 S. F. Required Storage Volume (1800 C.F. x Disturbed Ac): 10,458.00 Cu.Ft. Storage Estimate Before Cleanout Interval, Vc: 7,102.69 Cu.Ft. Cleanout Interval: 90 Days 9.38 Min. 4.57 In./hr. 9.20 Min. 7.43 cfs 15.67 cfs *Reference made to "Erosion and Sediment Control Planning and Design Manual" State of N.C. -Reference made to NOAA ATLAS 14, Volume 2, Version 2 NOAA Website, National Weather Service, Silver Springs, MD Evergreen Landing Apartments STORMWATER MANAGEMENT DETENTION STRUCTURE BASIN CONFIGURATION AND DESIGN Basin #1 BASIN CONFIGURATION Proposed Basin Dimensions at Permanent Pool Elevation: Proposed Permanent Pool Elevation: Basin Side Slopes: Submerged Orifice Outlet: Design Head, h: Maximum Release Rate: Minimum Release Rate: Maximum Hole Size: Minimum Hole Size: Conduit Pipe Size: Orifice Size Used: Orifice Sized Used Release Rates: Temporary Pool Depth: Water Quality Depth: Pond Bottom to Top of Riser: Width Length Surface Area 38 X 178 6,764.00 S.F. F 725.0 Ft. 3 : 1 0.008 S.F 0.003 S. F 0.007 SY 0.0503 CFS 25.0 In. 2 Days 5 Days 1.21 In. Dia. 0.74 In. Dia. 4.0 In. Dia. 1.13 In. Dia. 2.3 Days 2.60 Ft. 3.00 Ft. 6.80 Ft. Gupton Engineering-Planning-Surveying 2200 Silas Creek Pkwy. Suite 2B Winston-Salem, N.C. 27103 336-723-2459 PROJ: Gastonia DATE JOB # 12375 BY: STORM: 10-YR 7/1/2008 JSB DRAINAGE STRUCTURE DATA STRUCTURE NO. STATION TYPE INLET DRAINAGE AREA (AC) Q-1 0y AT INLET (CFS) RIM/INLET TOP OF CURB PIPE NO. IN INVERT IN INVERT OUT GRATE TYPE 1 CB 0.26 1.48 768.02 763.77 F 2 2+57.69 CB 0.37 1.24 755.37 751.12 F 3 YI 0.10 0.34 761.85 752.10 GRATE 4 3+38.74 CB 0.25 0.84 751.45 2 747.20 747.00 F 3 747.20 5 YI 0.23 0.77 751.50 748.20 GRATE 6 2+81.09 CB 0.20 0.67 754.20 5 747.64 747.44 G 7 0+46.76 CB 0.13 0.44 752.00 6 746.85 746.65 E 8 1+35.38 CB 0.10 0.34 757.72 753.47 F 9 0+59.80 CB 0.14 0.47 752.61 7 746.00 745.80 G 8 748.36 10 4+22.14 CB 0.28 0.94 749.41 4 745.15 744.74 F 9 744.94 11 5+75.11 CB 0.30 1.01 746.64 10 741.78 740.61 F 12 7+28.11 CB 0.41 1.38 745.08 11 739.08 738.88 F 13 1+52.32 CB 0.19 0.64 748.68 744.43 G 14 1+52.32 CB 0.15 0.50 748.68 13 743.83 743.63 F 15 0+35.32 CB 0.22 0.74 745.76 14 741.29 739.75 F 16 YI 0.32 1.08 737.67 734.42 GRATE Page 1 DRAINAGE STRUCTURE DATA STRUCTURE NO. STATION TYPE INLET DRAINAGE AREA (AC) Q-1 0y AT INLET (CFS) RIM/INLET TOP OF CURB PIPE NO. IN INVERT IN INVERT OUT GRATE TYPE 17 YI 0.08 0.27 738.54 16 733.48 733.28 GRATE 18 9+80.69 CB 0.22 0.74 745.36 17 732.18 731.98 G 19 8+39.93 TI 0.92 3.09 743.78 12 737.77 730.37 15 737.05 18 730.57 20 MH 0.34 1.14 733.40 19 729.31 729.11 21 TI 1.70 5.72 751.23 743.44 22 8+76.92 MH 0.00 0.00 745.05 21 741.00 740.80 23 TI 1.48 4.98 754.57 747.78 24 4+55.50 MH 0.00 0.00 749.40 22 736.59 736.39 23 745.15 Page 2 DRAINAGE STRUCTURE DATA Gupton Engineering-Planning-Surveying 2200 Silas Creek Pkwy. Suite 2B Winston-Salem, N.C. 27103 336-723-2459 PROJ: Gastonia DATE: 7/1/2008 JOB # 12375 BY: JSB STORM: 10-YR STORM PIPE DATA PIPE NO. FROM INLET NO. TO INLET NO. INLET AREA (ACRE) TOTAL AREA (ACRE) C COEFF. 1 INTEN. (IN/HR) INLET FLOW (CFS) PIPE FLOW (CFS) PIPE SLOPE (FT/FT) PIPE LENGTH (FT) REQ'D DIA. (IN) USED DIA. (IN) PIPE CAPAC. (CFS) PIPE VELOC. (FPS) 1 1 EX. CB 0.26 0.26 0.98 5.80 1.48 1.48 0.0100 67.92 8.6 15 6.48 3.65 2 2 4 0.37 0.37 0.58 5.80 1.24 1.24 0.0100 90.02 8.1 15 6.48 3.49 3 3 4 0.10 0.10 0.58 5.80 0.34 0.34 0.0100 98.37 4.9 15 6.48 2.52 4 4 11 0.25 0.72 0.58 5.80 0.84 2.42 0.0100 90.32 10.4 15 6.48 4.13 5 5 6 0.23 0.23 0.58 5.80 0.77 0.77 0.0100 56.18 6.8 15 6.48 3.10 6 6 7 0.20 0.43 0.58 5.80 0.67 1.45 0.0100 58.92 8.6 15 6.48 3.63 7 7 10 0.13 0.56 0.58 5.80 0.44 1.88 0.0100 64.46 9.4 15 6.48 3.88 8 8 9 0.10 0.10 0.58 5.80 0.34 0.34 0.0100 84.59 4.9 15 6.48 2.52 9 9 10 0.14 0.80 0.58 5.80 0.47 2.69 0.0100 85.59 10.8 15 6.48 4.24 10 10 11 0.28 1.80 0.58 5.80 0.94 6.06 0.0100 153.78 14.6 18 10.53 5.19 11 11 12 0.30 2.10 0.58 5.80 1.01 7.06 0.0100 153.00 15.5 18 10.53 5.39 12 12 19 0.41 2.51 0.58 5.80 1.38 8.44 0.0100 111.29 16.6 18 10.53 5.64 13 13 14 0.19 0.19 0.58 5.80 0.64 0.64 0.0100 60.02 6.3 15 6.48 2.96 14 14 15 0.15 0.34 0.58 5.80 0.50 1.14 0.0100 117.00 7.8 15 6.48 3.42 15 15 19 0.22 0.56 0.58 5.80 0.74 1.88 0.0412 89.99 7.2 15 13.15 6.59 16 16 17 0.32 0.32 0.58 5.80 1.08 1.08 0.0100 85.30 7.7 15 6.48 3.37 17 17 18 0.08 0.40 0.58 5.80 0.27 _ 1.35 0.0100 118.04 8.3 15 6.48 3.56 Page 1 STORM PIPE DATA PIPE NO. FROM INLET NO. TO INLET NO. INLET AREA (ACRE) TOTAL AREA L(ACRE) C COEFF. I INTEN. (IN/HR) INLET FLOW (CFS) PIPE FLOW (CFS) PIPE SLOPE (FT/FT) PIPE LENGTH (FT) REQ'D DIA. (IN) USED DIA. (IN) PIPE CAPAC. (CFS) PIPE VELOC. (FPS) 18 18 19 0.22 0.62 0.58 5.80 0.74 2.09 0.0100 140.69 9.8 15 6.48 3.98 19 19 20 0.92 4.61 0.58 5.80 3.09 15.51 0.0100 106.03 20.8 24 22.68 6.56 20 20 OUTLET 0.34 4.95 0.58 5.80 1.14 16.65 0.0100 51.58 21.4 24 22.68 6.68 21 21 22 1.70 1.70 0.58 5.80 5.72 5.72 0.0100 24.42 14.3 15 6.48 5.12 22 22 24 0.00 1.70 0.58 5.80 0.00 5.72 0.0100 421.42 14.3 15 6.48 5.12 23 23 24 1.48 1.48 0.58 5.80 4.98 4.98 0.0100 26.25 13.6 15 6.48 4.94 24 24 OUTLET 0.00 2.30 0.58 5.80 0.00 7.74 0.0100 74.37 16.0 18 10.53 5.52 Page 2 STORM PIPE DATA