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HomeMy WebLinkAboutSW5210702_Plansheet - Misc. Detail_20210708 (2)STORMWATER NARRATIVE: LOUISBURG ANNEX Prepared for GFD MANAGEMENT INC. 6350 Quadrangle Drive Suite 205 Chapel Hill, NC 27517 Bohler Project #: NCR211056 1st Submittal: July 2, 2021 t SEAL - 485 Charlie Yowell, PE H LER// BOHLER ENGINEERING NC, PLLC 4130 Parklake Avenue, Suite 130, Raleigh, NC 27612 NCBELS # P-1132 I P: 919-578-9000 1 F: 919-703-2665 www.bohlerengineering.com TABLE OF CONTENTS 1. DESCRIPTION............................................................................................................................1 1.1 General Project Description.....................................................................................................1 1.2 Stormwater Summary..............................................................................................................1 1.3 Erosion Control Summary........................................................................................................2 APPENDIX A SUPPORTING DOCUMENTS APPENDIX B STORMWATER NETWORK DESIGN APPENDIX C PRE/POST DEVELOPMENT DRAINAGE MAPS BOHLER BOHLER ENGINEERING NC, PLLC 1. DESCRIPTION 1.1 General Project Description GFD Management Inc. is proposing to develop a commercial back office building on a pad ready graded site located at in the Louisburg Plaza, in Louisburg, NC. The new development proposes to construct one commercial back office building with associated utility, stormwater, fine grading, and landscaping improvements to support the development. The site will utilize an existing offsite stormwater network and SCM wetpond. The site is cleared and has been previous disturbed as part of the Louisburg Plaza master plan. I Figure 1: Aerial View of Site 1.2 Stormwater Summary Drainage flows from the North to South and the post -development drainage pattern closely matches the existing drainage area and discharge locations. The proposed development will have 1.18 acres of impervious area over the 2.29-acre site for a BUA of 51.5%. The existing stormwater network and wetpond have been sized to handle 2.08 acres, which is above what this development is proposing. Runoff from the building, parking lots, and driveways will be collected by storm inlets and piped to the existing storm network in the access road. Stormwater runoff will be from commercial uses. The development will not adversely impact the existing network, wetpond, nor the adjacent properties. Refer to Appendix D for additional information. BOHLERI BOHLER ENGINEERING NC, PLLC Page I 1 1.3 Erosion Control Summary The site is subject to NCDEQ erosion control standard and specifications as the project is above 1 acre of disturbance. This project will have a 2-stage erosion control sequence. Stage 1 will propose silt fence, silt fence outlets, and inlet protection for fine grading activities. Stage 2 will consist of installation of storm drainage and utilities, paving operations, and the construction of the building. BOHLERI BOHLER ENGINEERING NC, PLLC Page 1 2 APPENDIX A ISUPPORTING DOCUMENTS BOHLERI BOHLER ENGINEERING NC, PLLC Hydrologic Soil Group —Franklin County, North Carolina (Louisburg Annex Soils Map) 741330 741350 741370 741390 741410 741430 741450 36o 4' 57" N I I * I I I I " 36o 4' 57" N r 4 1 rr F •5 M ' aD of 36o 4' 51" N Soil MaN may not he valiel at this scale. 36o 4' 51" N 741330 741350 741370 741390 741410 741430 741450 741470 Map Scale: 1:957 if printed on A portrait (8.5" x 11") sheet. En 01 Meters o N 0 10 20 40 60 Feet 0 45 90 1� 270 Map projection: Web Mercator Conermordinates: WGS84 Edge tics: lfrM Zone 17N WGS84 USDA Natural Resources Web Soil Survey 7/2/2021 0111111111111111 Conservation Service National Cooperative Soil Survey Pagel of 4 Hydrologic Soil Group —Franklin County, North Carolina (Louisburg Annex Soils Map) MAP LEGEND Area of Interest (AOI) 0 Area of Interest (AOI) Soils Soil Rating Polygons 0 A 0 A/D 0 B 0 B/D 0 C 0 C/D 0 D 0 Not rated or not available Soil Rating Lines r 0 A r 0 A/D B r B/D N 0 C r 0 C/D r 0 D r 0 Not rated or not available Soil Rating Points 0 A 0 A/D 0 B 0 B/D ❑ C 0 C/D 0 D ❑ Not rated or not available Water Features Streams and Canals Transportation — Rails ­0 Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography MAP INFORMATION The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Franklin County, North Carolina Survey Area Data: Version 23, Jun 4, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: May 25, 2016—Nov 17, 2017 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. USDA Natural Resources Web Soil Survey 7/2/2021 Conservation Service National Cooperative Soil Survey Page 2 of 4 Hydrologic Soil Group —Franklin County, North Carolina Louisburg Annex Soils Map Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI WbD Wake-Wateree- B 0.1 2.8% Wedowee complex, 8 to 15 percent slopes, rocky WeB Wedowee sandy loam, 2 B 1.8 87.6% to 6 percent slopes WeC Wedowee sandy loam, 6 B 0.2 9.6% to 10 percent slopes Totals for Area of Interest 2.0 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long -duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. USDA Natural Resources Web Soil Survey 7/2/2021 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group —Franklin County, North Carolina Louisburg Annex Soils Map Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff.- None Specified Tie -break Rule: Higher USDA Natural Resources Web Soil Survey 7/2/2021 Conservation Service National Cooperative Soil Survey Page 4 of 4 NORiA AROUNA Quami Aru1 LE LOCATIOM 1 KittreU 1 2 3 2ingleside 3 Gold Sand 4 5 4 Franklinton 5 Justice G Rolesrille 6 7 8 7 Bunn West 8 Bunn East ADJORIM QUADRARGLE5 ROAD CLASSIFICATION Expressway I Local Connector Secondary Hwy Local Road Ramp 4WD ■ Interstate Route C3 US Route O State Route LOUISBURG, NC 2019 Precipitation Frequency Data Server Page 1 of 4 NOAA Atlas 14, Volume 2, Version 3 Location name: Louisburg, North Carolina, USA" Latitude: 36.0827°, Longitude:-78.3189° Elevation: 306.39 ft- * source: ESRI Maps 'ate ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)' Average recurrence interval (years) Duration ��� 10 25 50 100 200 500 1000 4.90 5.68 6.42 7.26 8.08 8.76 9.36 9.90 10.5 11.1 5-min (4.49-5.36) 1 (5.21-6.19) 1 (5.88-7.00) 1 (6.65-7.92) 1 (7.36-8.81) 1 (7.93-9.55) (8.42-10.2) 1 (8.86-10.8) 1 (9.32-11.5) 1 (9.73-12.1) 10-min 3.91 4.54 5.14 5.81 6.44 6.98 7.44 7.85 8.30 8.71 (3.59-4.28) (4.16-4.95) (4.71-5.60) (5.31-6.33) (5.86-7.01) (6.32-7.61) (6.70-8.10) (7.02-8.57) (7.37-9.08) (7.67-9.55) 3.26 3.80 4.34 4.90 5.44 5.89 6.27 6.60 6.96 7.29 15-min (2.99-3.57) (3.49-4.15) (3.97-4.73) (4.48-5.34) (4.95-5.93) (5.33-6.42) (5.64-6.83) (5.90-7.21) (6.18-7.62) (6.42-7.99) 30-min 2.24 2.63 3.08 3.55 4.03 4.43 4.80 5.14 5.54 5.90 (2.05-2.45) (2.41-2.87) (2.82-3.36) (3.25-3.87) (3.67-4.39) (4.02-4.84) (4.32-5.23) (4.60-5.61) (4.92-6.06) (5.19-6.47) 1.39 1.65 1.97 2.31 2.68 3.00 3.31 3.60 3.98 4.31 60-min (1.28-1.53) (1.51-1.80) (1.81-2.15) (2.11-2.52) (2.44-2.92) (2.72-3.28) (2.98-3.60) (3.22-3.93) (3.53-4.35) 0.822 0.974 1.18 1.40 1.65 1.87 2.09 2.32 2.61 2.88 2-hr (0.748-0.904) (0.888-1.07) (1.07-1.29) (1.27-1.53) (1.48-1.80) (1.68-2.05) (1.86-2.28) (2.05-2.53) (2.29-2.85) (2.50-3.16) 0.582 IF 0.691 IF 0.838 IF 1.00 1.19 1.37 1.54 1.72 1.97 2.20 3-hr (0.528-0.645) (0.629-0.763) (0.762-0.927) (0.905-1.10) 1 (1.07-1.31) 1 (1.22-1.50) 1 (1.36-1.69) 1 (1.51-1.89) 1 (1.71-2.16) 1 (1.89-2.42) 0.349 0.414 0.504 0.602 0.719 0.829 0.939 1.06 1.21 1.36 6-hr (0.317-0.387) (0.377-0.458) (0.457-0.557) (0.545-0.664) (0.647-0.791) (0.741-0.911) (0.832-1.03) (0.926-1.16) 1 (1.05-1.33) 0.204 0.242 0.296 0.355 0.428 0.497 0.566 0.641 0.745 0.844 12-hr (0.187-0.225) (0.222-0.266) (0.270-0.326) (0.323-0.390) (0.387-0.469) (0.446-0.542) (0.503-0.617) (0.563-0.699) (0.644-0.812) (0.719-0.922) 0.121 0.146 0.184 0.214 0.255 0.289 0.323 0.360 0.411 0.452 24-hr (0.113-0.130) (0.137-0.157) (0.172-0.197) (0.199-0.229) (0.237-0.273) (0.267-0.310) (0.298-0.347) (0.330-0.387) (0.374-0.443) (0.409-0.489) 0.070 0.085 0.106 0.122 0.145 0.164 0.183 0.203 0.230 0.252 2-day (0.066-0.075) (0.080-0.090) (0.099-0.113) (0.114-0.131) (0.135-0.155) (0.152-0.175) (0.169-0.195) (0.186-0.217) (0.210-0.248) (0.229-0.273) 0.050 0.060 0.074 0.086 0.101 0.114 0.127 0.141 0.160 0.175 3-day (0.047-0.053) (0.056-0.064) (0.070-0.079) (0.080-0.091) (0.095-0.108) (0.106-0.122) (0.118-0.136) (0.130-0.151) (0.146-0.172) (0.159-0.188) 0.039 0.047 0.058 0.067 0.080 0.089 0.100 0.110 0.125 0.137 4-day (0.037-0.042) (0.044-0.050) (0.055-0.062) (0.063-0.071) (0.074-0.084) (0.083-0.095) (0.092-0.106) (0.101-0.117) (0.114-0.133) (0.124-0.146) 0.026 0.031 0.038 0.044 0.051 0.057 0.064 0.070 0.079 7 0.086 7-day (0.025-0.028) (0.029-0.033) (0.036-0.040) (0.041-0.046) (0.048-0.054) (0.053-0.061) (0.059-0.068) (0.065-0.075) (0.072-0.085) (0.078-0.093) 0.021 0.025 0.030 0.034 0.039 0.044 0.048 0.053 0.059 0.064 10-day (0.020-0.022) (0.023-0.026) (0.028-0.032) (0.032-0.036) (0.037-0.042) (0.041-0.046) (0.045-0.051) (0.049-0.056) (0.054-0.063) (0.058-0.068) 0.014 0.016 0.020 0.022 0.025 0.028 0.031 0.033 0.037 0.040 20-day (0.013-0.015) (0.016-0.017) (0.018-0.021) (0.021-0.023) (0.024-0.027) (0.026-0.030) (0.029-0.032) (0.031-0.035) (0.034-0.039) (0.037-0.043) 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.025 0.028 0.030 30-day (0.011-0.012) (0.013-0.014) (0.015-0.017) (0.017-0.019) (0.019-0.021) (0.020-0.023) (0.022-0.025) (0.024-0.027) (0.026-0.029) (0.028-0.032) 0.010 0.011 0.013 0.014 00-1 6-1 FOUR7 0.019 0.020 0.022 0.023 45-day (0.009-0.010) (0.011-0.012) (0.012-0.014) (0.014-0.015) (0.015-0.017) (0.017-0.018) (0.018-0.020) (0.019-0.021) (0.020-0.023) (0.022-0.024) 0.009 0.010 o--0-1 2-1 Fomfi3 0.014 0.015 0.016 0.017 0.018 0.019 60-day (0.008-0.009) (0.010-0.011) (0.011-0.012) (0.012-0.013) (0.013-0.015) (0.014-0.016) (0.015-0.017) (0.016-0.018) (0.017-0.019) (0.018-0.020) Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90 % confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=36.0827&lon=-78.3189&data... 7/1/2021 APPENDIX B ISTORMWATER NETWORK DESIGN BOHLERI BOHLER ENGINEERING NC, PLLC Start Node Stop Node Invert (Start) (ft) Invert (Stop) (ft) Length (Unified) (ft) Upstream Inlet C Upstream Inlet Area (acres) System Intensity (in/h) Flow (cfs) Capacity (Full Flow) (cfs) Velocity (ft/s) Slope (Calculated) (%) 110 EX-1 282.89 282 29.6 0.76 0.29 7.133 5.78 14.54 11.17 3 111 110 293.35 283.5 151.9 0.93 0.25 7.26 1.7 21.39 10.41 6.49 120 110 287.18 283.21 132.3 0.89 0.17 7.204 2.63 14.54 8.99 3 130 120 290 287.4 86.7 0.89 0.36 7.26 1.38 14.54 7.46 3 150 EX-2 293.79 293.45 67.2 0.58 0.26 7.073 1.74 5.94 4.21 0.5 160 150 294.51 293.89 125 0.55 0.17 7.26 0.68 5.94 3.22 0.5 c 0 m LU 295.00 290.00 285.00 280.00 Profile Report Engineering ProR/e - 01-130 (NCR211506 - Louisburg Annex stsw) 130 p: ,.,., . Or) A 1 1 w -0+50 0+00 0+50 1+00 1+50 2+00 2+50 3+00 Station (ft) StormCAD NCR211506 - Louisburg Annex.stsw Bentley Systems, Inc. Haestad Methods Solution Center [10.03.02.04] 7/2/2021 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203- Page 1 of 1 755-1666 Profile Report Engineering Profile ® 110 111 (NCR211506 ® Louisburg Annex. stsw) 300.00 295.00 f••1 11 285.00 f•:1 11 111 -0+50 0+00 0+50 1+00 1+50 2+00 Station (ft) StormCAD NCR211506 - Louisburg Annex.stsw Bentley Systems, Inc. Haestad Methods Solution Center [10.03.02.04] 7/2/2021 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203- Page 1 of 1 755-1666 W 300.00 295.00 290.00 DIX11 Profile Report Engineering Profile - ®Z - 160 (NCR211606 - Louisburg Annex stsw) [1II1Z11i EX-2 n:...,.. 1)nn nn h Mill] Station (ft) HKiIIIJ 1 +50 WON Rim: 298.24 ft Invert:294.51 fi N11111 StormCAD NCR211506 - Louisburg Annex.stsw Bentley Systems, Inc. Haestad Methods Solution Center [10.03.02.04] 7/2/2021 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203- Page 1 of 1 755-1666