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Stormwater Impact 5.21.21Stormwater Impact Analysis Wilmington CNG Station / PNG-20000 /April 2021 WILMINGTON CNG STATION – SUTTON STEAM PLANT ROAD WILMINGTON,NORTH CAROLINA STORMWATER IMPACT ANALYSIS CONSTRUCTION DRAWINGS CASE #:TBD PROJECT NUMBER:PNG-20000 DESIGNED BY:DANIEL WIEBKE,PE,CFM LAURYN KABRICH,EI TOMMY DABOLT DATE:APRIL 2021 2905 MERIDIAN PARKWAY DURHAM,NORTH CAROLINA 27713 NC LIC.#C-0293 NARRATIVE > PNG-20000 2905 Meridian Parkway, Durham, NC 27713 / 919. 361. 5000creatingexperiences through experience Wilmington CNG Station – Sutton Steam Plant Road Stormwater Narrative GENERAL DESCRIPTION Wilmington CNG Station – Sutton Steam Plant Road, is a fueling station that sits on a 3-acre piece of property on Sutton Steam Plant Road and US Highway 421 in Wilmington, NC. This analysis covers the development of the lot into a fueling station consisting of a driveway and pad with fueling equipment. The purpose of this analysis is to ensure the stormwater runoff will be adequately infiltrated into existing soils. According to the New Hanover County Stormwater Design Manual, infiltration facilities should be designed for the runoff of the 25-year storm event and checked for the 100-year storm event. CALCULATION METHODOLOGY §To determine the ultimate endpoints of runoff from the site, New Hanover County GIS topography was used. Water is assumed to infiltrate into existing soils at these locations. §On-site and off-site soils were determined using a combination of USDA Web Soil Survey and field-verified information from the geotechnical engineer. §Rainfall data for this area in the Wilmington, NC region is from NOAA Atlas 14. This data contains a depth- duration-frequency (DDF) table describing rainfall depth versus time for varying return periods in the area. These rainfall depths are input into the meteorological model within PondPack for peak flow rate calculations. Please reference the precipitation information within the Miscellaneous Site Information section of this report for additional information. §Soil Conservation Service Curve Numbers (SCS CN) were selected from Table 2 of the USDA TR-55 for the land use that is most similar to the zoning type or cover condition. §Per the Stormwater Soil Evaluation Report conducted by the geotechnical engineer (S&ME), the measured Ksat rate in the area of Sub-basin 1 is 30.0 in/hr and the measured Ksat rate in the area of Sub-basin 2 is 40.7 in/hr. Thus, these infiltration rates were used in the analysis that follows this narrative. DISCUSSION OF RESULTS PEAK RUNOFF CONTROL REQUIREMENTS As shown in the spreadsheet calculations, the criteria for infiltrating a 25-yr storm design was met and the 100-yr storm was checked. Shown below is a topo map taken from New Hanover County GIS, the two areas circled in blue are the ultimate endpoints of the runoff from the site. These areas both contain Kureb sand, which is a “Group A” Soil as obtained from the USDA Web Soil Survey tool. NARRATIVE > PNG-20000 creating experiences through experience 2of 2 CONCLUSION If the development on this tract is built as proposed within this report, then the requirements set forth in New Hanover County regulations will be met without additional stormwater control measures. However, modifications to the proposed development may require that this analysis be revised. Some modifications that would require this analysis to be revised include: 1.The proposed site impervious surface exceeds the amount accounted for in this report. 2.The post-development watershed breaks change significantly from those used to prepare this report. The above modifications may result in the assumptions within this report becoming invalid. The computations within this report will need to be revisited if any of the above conditions become apparent as development of the proposed site moves forward. 1 MISCELLANEOUS SITE INFORMATION 2 PRE-DEVELOPMENT HYDROLOGIC CALCULATIONS 5 SWALE CALCULATIONS 3 POST-DEVELOPMENT HYDROLOGIC CALCULATIONS 4 INFILTRATION CALCULATIONS Wilmington CNG Station – Sutton Steam Plant Road PNG-20000 MISCELLANEOUS SITE INFORMATION Copyright:© 2013 National Geographic Society, i-cubed 0 2,000 4,0001,000 Feet1 inch = 2,000 feet ¯WILMINGTON CNG STATION - SUTTON STEAM PLANT ROAD USGS TOPO MAPPROJECT #: PNG-20000WILMINGTON, NORTH CAROLINA NC DENR - DIVISON OF WATER RESOURCES Name of Stream Description Class Class Date Index No. 2B .0300 . 0311 CAPE FEAR RIVER BASIN Dock Creek C;Sw 09/01/74 18-74-60From source to Northeast Cape Fear River Northeast Cape Fear River SC;Sw 04/01/59 18-74-(61)From mouth of Ness Creek to Cape Fear River Ness Creek C;Sw 09/01/74 18-74-62From source to Northeast Cape Fear River Smith Creek C;Sw 09/01/74 18-74-63From source to Northeast Cape Fear River Spring Branch C;Sw 09/01/74 18-74-63-1From source to Smith Creek Burnt Mill Creek C;Sw 03/01/77 18-74-63-2From source to Smith Creek Mineral Springs Branch C;Sw 08/01/85 18-74-63-2-1From source to Burnt Mill Creek Alligator Creek SC;Sw 04/01/59 18-75From source to Cape Fear River Greenfield Creek SC;Sw 04/01/59 18-76From Greenfield Lake to Cape Fear River Greenfield Lake C;Sw 04/01/59 18-76-1Entire Lake Silver Stream Branch C;Sw 04/01/59 18-76-1-1From source to Greenfield Lake, Greenfield Creek Clay Bottom Branch C;Sw 04/01/59 18-76-1-2From source to Greenfield Lake, Greenfield Creek Jumping Run Branch C;Sw 04/01/59 18-76-1-3From source to Greenfield Lake, Greenfield Creek Squash Branch C;Sw 04/01/59 18-76-1-4From source to Greenfield Lake, Greenfield Creek Brunswick River SC 08/09/81 18-77From source to Cape Fear River Sturgeon Creek C;Sw 04/01/59 18-77-1From source to Burnswick River Mill Creek C;Sw 04/01/59 18-77-1-1From source to Sturgeon Creek Rowell Branch C;Sw 04/01/59 18-77-1-1-1From source to Mill Creek Banton Branch C;Sw 04/01/59 18-77-1-1-2From source to Mill Creek Redmond Creek SC;Sw 04/01/59 18-77-2From source to Brunswick River Jackeys Creek C;Sw 04/01/59 18-77-3From source to Brunswick River Piney Branch C;Sw 04/01/59 18-77-3-1From source to Jackeys Creek Mallory Creek C;Sw 04/01/59 18-78From source to Cape Fear River Little Mallory Creek (Beaverdam Branch) C;Sw 04/01/59 18-78-1From source to Mallory Creek Barnards Creek C;Sw 04/01/59 18-80From source to Cape Fear River Town Creek (Rattlesnake Branch) C;Sw 09/01/74 18-81From source to Cape Fear River Turkey Branch C;Sw 04/01/59 18-81-1From source to Town Creek Lewis Swamp C;Sw 09/01/74 18-81-2From source to Town Creek Tompkins Branch (Tomolin Branch) C;Sw 09/01/74 18-81-2-1From source to Lewis Swamp Lewis Branch C;Sw 09/01/74 18-81-2-2From source to Lewis Swamp Beaverdam Swamp C;Sw 09/01/74 18-81-3From source to Town Creek Rock Creek C;Sw 04/01/59 18-81-4From source to Town Creek Russells Creek C;Sw 09/01/74 18-81-5From source to Town Creek 47 Wilmington CNG Station – Sutton Steam Plant Road PNG-20000 PRE-DEVELOPMENT HYDROLOGIC CALCULATIONS Wilmington CNG Station PNG-20000 PRE-DEVELOPMENT HYDROLOGY Summary of Results L. Kabrich, EI 3/9/2021 HYDROLOGY INPUT SUMMARY Impervious Open Wooded Pond Total Impervious Open Wooded Pond Total 1 0.00 0.06 1.74 0.00 1.81 0.00 0.00 0.00 0.00 0.00 1.81 30 12.95 2 0.00 0.10 1.10 0.00 1.19 0.00 0.00 0.00 0.00 0.00 1.19 31 13.67 Totals =0.00 0.16 2.84 0.00 3.00 0.00 0.00 0.00 0.00 0.00 3.00 NUTRIENT INPUT SUMMARY ***Jordan/Falls Lake Stormwater Nutrient Load Accounting Tool Inputs Land Use Area (sf)Area (ac) Roadway Area 0 0.00 Driveway / Parking 0 0.00 Roof Area 0 0.00 Sidewalk / Patio 0 0.00 Open 0 0.00 Wooded 0 0.00 Pond 4,154 0.10 Total 4,154 0.10 Sub-basin ID Onsite Area [acres]Tc [min]Offsite Area [acres]Total Area [acres]SCS CN Wilmington CNG Station PNG-20000 PRE-DEVELOPMENT HYDROLOGY Subbasin 1 L. Kabrich, EI 3/9/2021 I. SCS CURVE NUMBERS Soils from WebSoilSurvey are only inclusive of indirectly connected areas HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. PRE-DEVELOPMENT A. Onsite Impervious Breakdown Contributing Area Area [sf]Area [ac] Roadway Area 0 0.00 Driveway / Parking Lot 0 0.00 Roof 0 0.00 Sidewalk / Patio 0 0.00 Other 0 0.00 Totals 0 0.00 B. Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 0 0.00 Onsite open 39 2,763 0.06 Onsite wooded 30 75,977 1.74 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total IC area =1.81 acres 78,740 sf Composite SCS CN =30 % Impervious =0.0% - Assume good condition Assume good condition - - Assume good condition Assume good condition Comments - Assume good condition Assume good condition Comments - Wilmington CNG Station PNG-20000 PRE-DEVELOPMENT HYDROLOGY Subbasin 1 L. Kabrich, EI 3/9/2021 III. TIME OF CONCENTRATION INFORMATION Time of concentration is calculated using the SCS Segmental Approach (TR-55). Segment 1: Overland Flow Segment 2: Concentrated Flow Length =100 ft Length =249 ft Top Elev =36.00 ft Top Elev =30.00 ft Bot Elev =30.00 ft Bot Elev =22.00 ft Height =6 ft Height =8 ft Slope =0.0601 ft/ft Slope =0.0321 ft/ft Manning's n =0.40 wooded-dense underbrush Paved ? =No P (2-year/24-hour) =4.61 inches (Wilmington, NC)Velocity =2.89 ft/sec Segment Time =11.52 minutes Segment Time =1.43 minutes Time of Concentration =12.95 minutes SCS Lag Time =7.77 minutes (SCS Lag = 0.6* Tc) Time Increment =2.25 minutes (= 0.29*SCS Lag) Wilmington CNG Station PNG-20000 PRE-DEVELOPMENT HYDROLOGY Subbasin 2 L. Kabrich, EI 3/9/2021 I. SCS CURVE NUMBERS Soils from WebSoilSurvey are only inclusive of indirectly connected areas HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. PRE-DEVELOPMENT A. Onsite Impervious Breakdown Contributing Area Area [sf]Area [ac] Roadway Area 0 0.00 Driveway / Parking Lot 0 0.00 Roof 0 0.00 Sidewalk / Patio 0 0.00 Other 0 0.00 Totals 0 0.00 B. Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 0 0.00 Onsite open 39 4,154 0.10 Onsite wooded 30 47,786 1.10 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =1.19 acres 51,940 sf Composite SCS CN =31 % Impervious =0.0% Assume good condition Assume good condition - Comments - Assume good condition Assume good condition Comments - Assume good condition Assume good condition - - Wilmington CNG Station PNG-20000 PRE-DEVELOPMENT HYDROLOGY Subbasin 2 L. Kabrich, EI 3/9/2021 III. TIME OF CONCENTRATION INFORMATION Time of concentration is calculated using the SCS Segmental Approach (TR-55). Segment 1: Overland Flow Segment 2: Concentrated Flow Length =100 ft Length =291 ft Top Elev =36.00 ft Top Elev =31.00 ft Bot Elev =31.00 ft Bot Elev =15.00 ft Height =5 ft Height =16 ft Slope =0.0501 ft/ft Slope =0.0550 ft/ft Manning's n =0.40 wooded-dense underbrush Paved ? =No P (2-year/24-hour) =4.61 inches (Wilmington, NC)Velocity =3.78 ft/sec Segment Time =12.39 minutes Segment Time =1.28 minutes Time of Concentration =13.67 minutes SCS Lag Time =8.20 minutes (SCS Lag = 0.6* Tc) Time Increment =2.38 minutes (= 0.29*SCS Lag) GRAPHIC SCALE 0 20 40 80 1 inch = 40 ft. PROJECT AREA = 3.00 ACRES IMPERVIOUS AREA = 0.00 ACRES PERCENT IMPERVIOUS = 0% The John R. McAdams Company, Inc. 2905 Meridian Parkway Durham, NC 27713 phone 919. 361. 5000 fax 919. 361. 2269 license number: C-0293, C-187 www.mcadamsco.com M: \ P r o j e c t s \ P i e d m o n t N G a s \ P N G - 2 0 0 0 0 \ 0 4 - P r o d u c t i o n \ W a t e r R e s o u r c e s \ P e r m i t t i n g \ C u r r e n t D r a w i n g s \ P N G 2 0 0 0 0 - P R E . d w g , 3/ 9 / 2 0 2 1 1 0 : 3 4 : 4 1 A M , Ka b r i c h , L a u r y n PIEDMONT NATURAL GAS SUBBASIN 1 AREA = 78,740 SF (1.81 AC) SUBBASIN 2 AREA = 51,940 SF (1.19 AC) TC P A T H S1 S2 TC PATH S1 S2 Subsection: Master Network Summary Catchments Summary Peak Flow (ft³/s) Time to Peak (min) Hydrograph Volume (ac-ft) Return Event (years) ScenarioLabel 0.000.000.0002Pre-Development 2-yrSub 2 0.08783.000.03610Pre-Development 10- yr Sub 2 0.44753.000.10125Pre-Development 25- yr Sub 2 1.81729.000.295100Pre-Development 100 -yr Sub 2 0.001,440.000.0002Pre-Development 2- yr Sub 1 0.08756.000.02910Pre-Development 10-yrSub 1 0.35753.000.07625Pre-Development 25- yr Sub 1 1.37729.000.211100Pre-Development 100 -yr Sub 1 Node Summary Peak Flow (ft³/s) Time to Peak (min) Hydrograph Volume (ac-ft) Return Event (years) ScenarioLabel 0.000.000.0002Pre-Development 2-yr POA 2 0.08783.000.03610Pre-Development 10- yr POA 2 0.44753.000.10125Pre-Development 25- yr POA 2 1.81729.000.295100Pre-Development 100 -yr POA 2 0.001,440.000.0002Pre-Development 2- yr POA 1 0.08756.000.02910Pre-Development 10- yr POA 1 0.35753.000.07625Pre-Development 25- yr POA 1 1.37729.000.211100Pre-Development 100 -yr POA 1 4/8/2021PNG-20000.ppc T. DaboltPNG-20000 FlexTable: Catchment Table (PNG-20000.ppc) Current Time: 0.00 min Time of Concentration(min) SCS CNArea (ft²) LabelNotes 13.673151,940Sub 1PRE 12.953078,740Sub 2PRE 3/9/2021PNG-20000.ppc T. DaboltPNG-20000 Wilmington CNG Station – Sutton Steam Plant Road PNG-20000 POST-DEVELOPMENT HYDROLOGIC CALCULATIONS Wilmington CNG Station PNG-20000 POST-DEVELOPMENT HYDROLOGY Summary of Results L. Kabrich, EI 3/9/2021 HYDROLOGY INPUT SUMMARY Impervious Open Wooded Pond Total Impervious Open Wooded Pond Total 1 0.44 0.82 0.79 0.00 2.05 0.00 0.00 0.00 0.00 0.00 2.05 48 11.24 2 0.26 0.26 0.43 0.00 0.95 0.00 0.00 0.00 0.00 0.00 0.95 51 12.31 Totals =0.70 1.08 1.22 0.00 3.00 0.00 0.00 0.00 0.00 0.00 3.00 Sub-basin ID Onsite Area [acres]Tc [min]Offsite Area [acres]Total Area [acres]SCS CN Wilmington CNG Station PNG-20000 POST-DEVELOPMENT HYDROLOGY Subbasin 1 L. Kabrich, EI 3/9/2021 I. SCS CURVE NUMBERS HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. POST-DEVELOPMENT A. Onsite Impervious Breakdown Contributing Area Area [sf]Area [ac] Roadway Area 19,111 0.44 Driveway / Parking Lot 0 0.00 Roof 0 0.00 Sidewalk / Patio 0 0.00 Other 0 0.00 Totals 19,111 0.44 B. Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 19,111 0.44 Onsite open 39 35,768 0.82 Onsite wooded 30 34,263 0.79 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =2.05 acres 89,142 sf Composite SCS CN =48 % Impervious =21.4% C. Time of Concentration Information Time of concentration is calculated using the SCS Segmental Approach (TR-55). Segment 1: Overland Flow Segment 3: Concentrated Flow Length =100 ft Length =249 ft Top Elev =31.00 ft Top Elev =28.00 ft Bot Elev =28.00 ft Bot Elev =15.00 ft Height =3 ft Height =13 ft Slope =0.0300 ft/ft Slope =0.0521 ft/ft Manning's n =0.24 dense grasses Paved ? =No P (2-year/24-hour) =4.61 inches (Wilmington, NC)Velocity =3.68 ft/sec Segment Time =10.11 minutes Segment Time =1.13 minutes Time of Concentration =11.24 minutes SCS Lag Time =6.74 minutes (SCS Lag = 0.6* Tc) Time Increment =1.96 minutes (= 0.29*SCS Lag) Assume good condition Assume good condition - Comments - Assume good condition Assume good condition Comments - Assume good condition Assume good condition - - Wilmington CNG Station PNG-20000 POST-DEVELOPMENT HYDROLOGY Subbasin 2 L. Kabrich, EI 3/9/2021 I. SCS CURVE NUMBERS HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. POST-DEVELOPMENT A. Onsite Impervious Breakdown Contributing Area Area [sf]Area [ac] Roadway Area 11,346 0.26 Driveway / Parking Lot 0 0.00 Roof 0 0.00 Sidewalk / Patio 0 0.00 Other 0 0.00 Totals 11,346 0.26 B. Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 11,346 0.26 Onsite open 39 11,452 0.26 Onsite wooded 30 18,740 0.43 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =0.95 acres 41,538 sf Composite SCS CN =51 % Impervious =27.3% C. Time of Concentration Information Time of concentration is calculated using the SCS Segmental Approach (TR-55). Segment 1: Overland Flow Segment 2: Concentrated Flow Length =100 ft Length =301 ft Top Elev =31.00 ft Top Elev =28.00 ft Bot Elev =28.00 ft Bot Elev =22.00 ft Height =3 ft Height =6 ft Slope =0.0300 ft/ft Slope =0.0199 ft/ft Manning's n =0.24 dense grasses Paved ? =No P (2-year/24-hour) =4.61 inches (Wilmington, NC)Velocity =2.28 ft/sec Segment Time =10.11 minutes Segment Time =2.20 minutes Time of Concentration =12.31 minutes SCS Lag Time =7.39 minutes (SCS Lag = 0.6* Tc) Time Increment =2.14 minutes (= 0.29*SCS Lag) - Comments - Assume good condition Assume good condition - - Comments - Assume good condition Assume good condition Assume good condition Assume good condition GRAPHIC SCALE 0 20 40 80 1 inch = 40 ft. PROJECT AREA = 3.00 ACRES IMPERVIOUS AREA = 0.70 ACRES PERCENT IMPERVIOUS = 23% The John R. McAdams Company, Inc. 2905 Meridian Parkway Durham, NC 27713 phone 919. 361. 5000 fax 919. 361. 2269 license number: C-0293, C-187 www.mcadamsco.com M: \ P r o j e c t s \ P i e d m o n t N G a s \ P N G - 2 0 0 0 0 \ 0 4 - P r o d u c t i o n \ W a t e r R e s o u r c e s \ P e r m i t t i n g \ C u r r e n t D r a w i n g s \ P N G 2 0 0 0 0 - P O S T . d w g , 3/ 9 / 2 0 2 1 1 0 : 4 1 : 3 8 A M , Ka b r i c h , L a u r y n PIEDMONT NATURAL GAS TC PATH S1 S2 SUBBASIN 1 AREA = 89,142 SF (2.05 AC) SUBBASIN 2 AREA = 41,538 SF (0.955 AC) TC PATH S1 S2 Subsection: Master Network Summary Catchments Summary Peak Flow (ft³/s) Time to Peak (min) Hydrograph Volume (ac-ft) Return Event (years) ScenarioLabel 0.40729.000.0462Post-Development 2-yrSub 2 1.60726.000.14610Post-Development 10 -yr Sub 2 2.56726.000.23825Post-Development 25 -yr Sub 2 4.24726.000.439100Post-Development 100-yr Sub 2 0.49729.000.0762Post-Development 2- yr Sub 1 2.87726.000.26710Post-Development 10-yrSub 1 4.87726.000.44925Post-Development 25 -yr Sub 1 8.45726.000.857100Post-Development 100-yr Sub 1 Node Summary Peak Flow (ft³/s) Time to Peak (min) Hydrograph Volume (ac-ft) Return Event (years) ScenarioLabel 0.40729.000.0462Post-Development 2-yr POA 2 1.60726.000.14610Post-Development 10 -yr POA 2 2.56726.000.23825Post-Development 25 -yr POA 2 4.24726.000.439100Post-Development 100-yr POA 2 0.49729.000.0762Post-Development 2- yr POA 1 2.87726.000.26710Post-Development 10 -yr POA 1 4.87726.000.44925Post-Development 25 -yr POA 1 8.45726.000.857100Post-Development 100-yr POA 1 4/8/2021PNG-20000.ppc T. DaboltPNG-20000 FlexTable: Catchment Table (PNG-20000.ppc) Current Time: 0.00 min Time of Concentration(min) SCS CNArea (ft²) LabelNotes 11.244889,142Sub 1POST 12.315141,538Sub 2POST 3/9/2021PNG-20000.ppc T. DaboltPNG-20000 Wilmington CNG Station – Sutton Steam Plant Road PNG-20000 INFILTRATION CALCULATIONS Wilmington CNG Station PNG-20000 POST-DEVELOPMENT INFILTRATION DATA T. Dabolt 2/16/2021 Sub-basin 1 Measured Soil Infiltration Rate=30.0 in/hr =6.944E-04 ft/s Sub-basin 2 Measured Soil Infiltration Rate=40.7 in/hr =9.421E-04 ft/s Sub-basin 1 Sub-basin 2 Infiltration Area =15,428 SF Infiltration Area =12,333 SF Runoff Flow =4.87 ac-ft Runoff Flow =2.56 ac-ft 212137 cf 111514 cf Infiltration Flow Rate =10.71 cfs Infiltration Flow Rate =11.62 cfs Infiltration Time =0.23 days Infiltration Time =0.11 days Sub-basin 1 Sub-basin 2 Infiltration Area =15,428 SF Infiltration Area =12,333 SF Runoff Flow =8.45 ac-ft Runoff Flow =4.24 ac-ft 368082 cf 184694 cf Infiltration Flow Rate =10.71 cfs Infiltration Flow Rate =11.62 cfs Infiltration Time =0.40 days Infiltration Time =0.18 days 25-yr Storm 100-yr Storm S&ME, Inc. | 3201 Spring Forest Road | Raleigh, NC 27616 | p 919.872.2660 | www.smeinc.com March 4, 2021 McAdams 2905 Meridian Parkway Durham, North Carolina 27713 Attention: Mr. Brandon Finch Reference: Stormwater Soil Evaluation Report PNG Natural Gas Station Site Sutton Steam Plant Road, Wilmington, New Hanover County, North Carolina S&ME Project No. 1306-20-008 Dear Mr. Finch: S&ME, Inc. (S&ME) has conducted a stormwater soil evaluation in general accordance with S&ME Proposal 43- 1900107 dated February 11, 2019. Our evaluation was conducted to provide information for the design of a Stormwater Control Measure (SCM) and a Stormwater Management Permit Application to the North Carolina Department of Environmental Quality (NCDEQ) – Division of Energy, Minerals, & Land Resources (DEMLR) and/or local municipality. A soil scientist evaluated the soil conditions on March 22, 2019.  Background Information The site is located southwest of the intersection of Sutton Steam Plant Road and NC Highway 17 in Wilmington, North Carolina. We understand that development will include a new fueling station with a canopy and compressor pad and associated concrete pavements. The resulting stormwater from impervious surfaces is proposed to be treated with an infiltration type SCM located at two areas as shown on the attached Figures 1 through 3. The enclosed Figures 1 and 2 depict the restaurant site, parcel boundary and stormwater soil evaluation locations on a US Department of Agriculture (USDA) Soil Conservation Service (SCS) New Hanover County soil survey exhibit, US Geologic Survey (USGS) topographic exhibit, respectively. According to Figure 1, the soils in the vicinity of the proposed infiltration SCM are mapped as the Kureb soil series. The Kureb series consists of very deep, excessively drained, gently sloping to moderately steep soils on Coastal Plain uplands and on side slopes along streams and bays. They have formed in marine, aeolian, or fluvial sands. The stormwater soil evaluation was performed at two locations (Ksat-1 and Ksat-2) as shown on the attached Stormwater Soil Evaluation Exhibit (Figure 3). Our evaluation consisted of identifying and recording the soil morphological conditions at these locations in order to develop soil profile descriptions, performing seasonal high water table (SHWT) estimations and measuring the observed water table (OWT) if applicable, and performing in- situ saturated hydraulic conductivity (Ksat) testing of the subsoil. Stormwater Soil Evaluation Report PNG Natural Gas Station Site Sutton Steam Plant Road, Wilmington, New Hanover County, North Carolina S&ME Project No. 1306-20-008 March 4, 2021 2  Findings SHWT Estimation and Depth to OWT S&ME estimated the SHWT by advancing hand auger borings at the two proposed locations shown on the attached Figure 3 and evaluating the soil for evidence of SHWT influence. This evaluation involved looking at the actual moisture content in the soil and observing the matrix and mottle colors. Depending on the soil texture, the soil color will indicate processes that are driven by SHWT fluctuations, such as iron reduction and oxidation and organic matter staining. In addition, S&ME recorded the depth that the OWT was encountered below existing ground surface (EGS) at each soil boring location if applicable. The OWT was measured as the static water level in each of the temporary hand auger boring locations. It should be noted that the static water level/OWT measured in the auger holes is a measurement of the water table at that moment and does not represent an average water level or the highest point at which the water table may rise to. Furthermore, it is expected that groundwater elevations in the study area will likely be influenced by factors such as precipitation and proximity to surface water discharge/recharge features. See Table 1 below and the attached soil profile descriptions on Figure 3 for the estimated SHWT depths and measured depth to the OWT. Table 1: SHWT Estimation and Depth to OWT HAND AUGER BORING LOCATION SEASONAL HIGH WATER TABLE (SHWT) DEPTH (inches/feet below EGS) OBSERVED WATER TABLE (OWT) DEPTH (inches/feet below EGS) Ksat-1 42 / 3.5 42 / 3.5 Ksat-2 >72 / >6.0 >72 / >6.0 EGS: Existing Ground Surface Permeability/Hydraulic Conductivity Estimation The soil profile descriptions included on the attached Figure 3 show the soil morphological conditions including soil texture, structure, color, estimated United States Department of Agriculture (USDA) permeability and estimated USDA hydraulic conductivity (Ksat) for the different soil horizons found on-site. Please refer to the enclosed map and soil profile descriptions on Figure 3 for more information. These estimates were obtained from one or more of the following: New Hanover County Soil Survey “Physical & Chemical Properties of the Soil - Permeability”; and/or USDA-NRCS (United States Department of Agriculture - Natural Resource Conservation Service) official series description, and/or “NRCS Field Book for Describing & Sampling Soils” the permeability estimates were converted to conductivity on the profile description tables. Stormwater Soil Evaluation Report PNG Natural Gas Station Site Sutton Steam Plant Road, Wilmington, New Hanover County, North Carolina S&ME Project No. 1306-20-008 March 4, 2021 3 In-situ Ksat Testing In addition to the USDA permeability and conductivity estimations mentioned above, S&ME performed in-situ Ksat testing at the three locations (Ksat-1 and Ksat-2) as shown on Figure 3. On March 2, 2021 in-situ Ksat measurements were conducted with an Amoozemeter® compact constant-head permeameter (CCHP). Specifically, the constant-head well permeameter technique (also known as shallow well pump-in technique and bore hole permeameter method) was used. This procedure is described in Methods of Soil Analysis, Part 1., Chapter 29 – Hydraulic Conductivity of Saturated Soils: Field Methods, 29 – 3.2 Shallow Well Pump In Method, pp. 758-763 and in the Soil Science Society of America Journal, Vol. 53, no. 5, Sept. – Oct. 1989, “A Constant-head Permeameter for Measuring Saturated Hydraulic Conductivity of the Vadose Zone” and “Comparison of the Glover Solution with the Simultaneous – Equations Approach for Measuring Hydraulic Conductivity.” In brief, this method involves allowing a measured volume of water to percolate through the soil until a steady rate of flow is achieved. This final rate was used to calculate the Ksat of the subsoil horizon by the Glover equation. The hand auger borings used for Ksat testing were advanced below the EGS using a hand auger equipped with a two inch diameter bucket. The water dissipating unit was lowered to the bottom of the hole and water was dispensed from the Amoozemeter®. The water was allowed to move through the unit until steady-state flow was achieved and completely drained for one or more cycles and on the final cycle flow rates were recorded. The reported measurements were averaged to achieve a representative Ksat values for each testing location. The Ksat values measured in-situ for locations Ksat-1 and Ksat-2 are summarized on Table 2 below. The Ksat testing results shown on Table 2 below are also shown on the attached Figure 3 along with the approximate testing locations. The individual Ksat test records are included in Appendix I. Table 2: Ksat Testing Results KSAT TEST LOCATION TEST HORIZON / SOIL TEXTURE IN-SITU TESTING DEPTH FROM EGS (inches / feet) MEASURED KSAT RATE (inches per hour) SW-1 A / Sand 6 / 0.50 30.0 SW-2 A / Sand 8 / 0.67 40.7 EGS: Existing Ground Surface  Limitations Data and conclusions presented herein are based on materials encountered at the hand auger boring and Ksat testing locations only. Conditions may vary between hand auger borings and Ksat testing locations and in other areas of the site. Stormwater Soil Evaluation Report PNG Natural Gas Station Site Sutton Steam Plant Road, Wilmington, New Hanover County, North Carolina S&ME Project No. 1306-20-008 March 4, 2021 4  Closing S&ME appreciates the opportunity to provide soil evaluation services for this project. If you have any questions please contact Walter Cole at 919-872-2660 or wcole@smeinc.com. Sincerely, S&ME, Inc. Walter Cole, LSS, REHS Thomas P. Raymond, PE Senior Project Manager Environmental Area Manager Enclosed: Figure 1: USDA-SCS New Hanover County Soil Survey Exhibit Figure 2: USGS Topographic Exhibit Figure 3: Stormwater Soil Evaluation Exhibit Appendix I: Ksat Test Records Figures !> !> Kr Ur Ksat-1 Ksat-2 !>Ksat Test Location Soil Map UnitInfiltration Areas SCALE: DATE: PROJECT NUMBER FIGURE NO. 11 " = 200 ' 3-3-21 1306-20-008SUTTON STEAM PLANT ROAD AND NC 17WILMINGTON, NEW HANOVER COUNTY, NORTH CAROLINA Drawing Path: T:\GEO\Projects\2020\1306-20-008 McAdams_PNG Natural Gas Fueling Station_Wilmington, NC\GIS\SHWT\SOILS.mxd plotted by abentz 03-03-2021 0 200 400(FEET) USDA-NRCS SOIL SURVEY EXHIBIT ³ REFERENCE:GIS BASE LAYERS WERE OBTAINED FROM THE USDA-NRCS SOIL SURVEY AREA NC129 ANDTHE 2020 NCONEMAP AERIAL ORTHOIMAGERY LAYER. THIS MAP IS FOR INFORMATIONALPURPOSES ONLY. ALL FEATURE LOCATIONS DISPLAYED ARE APPROXIMATED. THEY ARENOT BASED ON CIVIL SURVEY INFORMATION, UNLESS STATED OTHERWISE. SOILS:Kr: Kureb sand, 1-8% slopes Infiltration Areas SCALE: DATE: PROJECT NUMBER FIGURE NO. 21 " = 500 ' 3-3-21 1306-20-008SUTTON STEAM PLANT ROAD AND NC 17WILMINGTON, NEW HANOVER COUNTY, NORTH CAROLINA Drawing Path: T:\GEO\Projects\2020\1306-20-008 McAdams_PNG Natural Gas Fueling Station_Wilmington, NC\GIS\SHWT\USGS.mxd plotted by abentz 03-03-2021 0 500 1,000(FEET) USGS TOPOGRAPHIC EXHIBIT ³ REFERENCE:GIS BASE LAYERS WERE OBTAINED FROM THE USGS NATIONAL TOPO MAP VIEWER. THISMAP IS FOR INFORMATIONAL PURPOSES ONLY. ALL FEATURE LOCATIONS DISPLAYED AREAPPROXIMATED. THEY ARE NOT BASED ON CIVIL SURVEY INFORMATION, UNLESS STATEDOTHERWISE. !> !>Ksat-1 Ksat-2 NCCGIA, NC911 Board !>Ksat Test Location Infiltration Areas SCALE: DATE: PROJECT NUMBER FIGURE NO.3 1 " = 150 ' 3-3-21 1306-20-008 SUTTON STEAM PLANT ROAD AND NC 17 WILMINGTON, NEW HANOVER COUNTY, NORTH CAROLINA Drawing Path: T:\GEO\Projects\2020\1306-20-008 McAdams_PNG Natural Gas Fueling Station_Wilmington, NC\GIS\SHWT\STORMWATER.mxd plotted by abentz 03-03-2021 0 150 300 (FEET) STORMWATER SOIL EVALUATION EXHIBIT ³ REFERENCE:GIS BASE LAYERS WERE OBTAINED FROM THE 2020 NCONEMAP AERIAL ORTHOIMAGERYLAYER. THIS MAP IS FOR INFORMATIONAL PURPOSES ONLY. ALL FEATURE LOCATIONSDISPLAYED ARE APPROXIMATED. THEY ARE NOT BASED ON CIVIL SURVEY INFORMATION,UNLESS STATED OTHERWISE. Soil Profile DescriptionsBoring Ksat-1 S&ME Project Number: 1306-20-008 Boring Date: March 3, 2021 Landscape Position: Toeslope (Matrix)(Mottles) A 0-10 2.5Y 2.5/1 sand single grained loose 70% coated sand grains measured at 6 inches below EGS 30.0 C1 10-18 10YR 5/1 sand single grained loose 6 - 20 >14 C2 18-48+10YR 5/2 sand single grained loose saturated at 40 inches 6 - 20 >14Estimated SHWT depth from EGS:42 inches ( 3.5 feet )Measured OWT depth from EGS:42 inches ( 3.5 feet ) Boring Ksat-2 S&ME Project Number: 1306-20-008 Boring Date: March 3, 2021 Landscape Position: Toeslope (Matrix)(Mottles) A 0-10 2.5Y 5/1 sand single grained loose measured at 8 inches below EGS 40.7 E 10-24 10YR 6/1 sand single grained loose 6 - 20 >14 Bh 24-32 10YR 5/8 10YR 4/4 sand single grained loose w eak cemented nodules 6 - 20 >14 C1 32-60 10YR 6/6 sand single grained loose 6 - 20 >14 C2 60-72+10YR 7/4 sand single grained loose 6 - 20 >14Estimated SHWT depth from EGS:>72 inches ( >6.0 feet )Measured OWT depth from EGS:>72 inches ( >6.0 feet ) Moist Consistence Notes USDA Estimated Permeability (in/hr) USDA Estimated Conductivity (in/hr)Horizon Depth (in) Color Texture Grade Structure Moist Consistence Notes USDA Estimated Permeability (in/hr) USDA Estimated Conductivity (in/hr)Horizon Depth (in) Color Texture Grade Structure Appendix I: Ksat Test Records S&ME "IN-SITU" CONSTANT HEAD PERMEAMETER Date:3/2/2021 Hole Depth:0.50 Feet Location:Ksat-1 Hole Radius (r):0.08 Feet Horizon:A Horizon - 6 inches below EGS Bubble Tube to Surface:0.33 Feet Client:McAdams Reference Tube to Hole Bottom (D):0.83 Feet Project Name:PNG Natural Gas Filling Station Site Water Depth in Hole (H):0.50 Feet Project #:1306-20-008 CHT Tube(s) Setting (h1):0.33 Feet Chamber Used:2.00 Ft2 Ksat = CQ/(2PiH2)Initial Water in Hole:0.42 Feet Final Water in Hole:0.42 Feet C = sinh-1 (H/r) - [(r/H)2 + 1]1/2 + r/H sinh-1 = inverse hyperbolic sin of a number H = Height of water in hole (cm) r = radius of hole (cm) Q = Constant Flow Rate (Gal/day) = Cross Sectional Area of Reservior x Length of Drop in Water Column over Time Time Drop in Water Column (ft)Time (min) = r = 0.08 ft (ft)(cm)2 H = 0.42 ft 0-2 min.0.689 21.00 2-4 min.0.558 17.00 refill 4-6 min.0.000 0.00 6-8 min.0.656 20.00 C = 1.50 8-10 min.0.591 18.00 Q = 331.76 Gallons/Day refill 10-12 min.0.000 0.00 12-14 min.0.623 19.00 14-16 min.0.591 18.00 16-18 min.0.525 16.00 refill 18-20 min.0.000 0.00 20-22 min.0.591 18.00 22-24 min.0.558 17.00 24-26 min.0.558 17.00 Avg.0.569 Cross Sectional Area = 0.11 ft2 Length of Drop in Water Column = 392.39 ft/day Ksat = 449.06 Gallons/Day/ft2 Inches/Hour = 30.018 Note: Ksat calculations are based on average drop in Water Column (ft) after equilibrium is reached. T:\GEO\Projects\2020\1306-20-008 McAdams_PNG Natural Gas Fueling Station_Wilmington, NC\Ksats\KSAT 3/4/2021 S&ME "IN-SITU" CONSTANT HEAD PERMEAMETER Date:3/2/2021 Hole Depth:0.67 Feet Location:Ksat-2 Hole Radius (r):0.08 Feet Horizon:A Horizon - 8 inches below EGS Bubble Tube to Surface:0.33 Feet Client:McAdams Reference Tube to Hole Bottom (D):1.00 Feet Project Name:PNG Natural Gas Filling Station Site Water Depth in Hole (H):0.50 Feet Project #:1306-20-008 CHT Tube(s) Setting (h1):0.50 Feet Chamber Used:2.00 Ft2 Ksat = CQ/(2PiH2)Initial Water in Hole:0.33 Feet Final Water in Hole:0.33 Feet C = sinh-1 (H/r) - [(r/H)2 + 1]1/2 + r/H sinh-1 = inverse hyperbolic sin of a number H = Height of water in hole (cm) r = radius of hole (cm) Q = Constant Flow Rate (Gal/day) = Cross Sectional Area of Reservior x Length of Drop in Water Column over Time Time Drop in Water Column (ft)Time (min) = r = 0.08 ft (ft)(cm)1 H = 0.33 ft 0-1 min.0.558 17.00 1-2 min.0.230 7.00 2-3 min.0.230 7.00 3-4 min.0.230 7.00 C = 1.31 refill 4-5 min.0.000 0.00 Q = 319.00 Gallons/Day 5-6 min.0.394 12.00 6-7 min.0.262 8.00 7-8 min.0.262 8.00 8-9 min.0.230 7.00 9-10 min.0.000 0.00 10-11 min.0.262 8.00 11-12 min.0.295 9.00 12-13 min.0.262 8.00 13-14 min.0.262 8.00 Avg.0.273 Cross Sectional Area = 0.11 ft2 Length of Drop in Water Column = 377.30 ft/day Ksat = 609.37 Gallons/Day/ft2 Inches/Hour = 40.733 Note: Ksat calculations are based on average drop in Water Column (ft) after equilibrium is reached. T:\GEO\Projects\2020\1306-20-008 McAdams_PNG Natural Gas Fueling Station_Wilmington, NC\Ksats\KSAT 3/4/2021 Wilmington CNG Station – Sutton Steam Plant Road PNG-20000 SWALE CALCULATIONS Wilmington CNG Station PNG-20000 SWALE HYDROLOGY Swale 1 L. Kabrich, EI 4/8/2021 I. SCS CURVE NUMBERS HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. POST-DEVELOPMENT Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 12,170 0.28 Onsite open 39 7,726 0.18 Onsite wooded 30 259 0.01 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =0.46 acres 20,155 sf Composite SCS CN =75 % Impervious =60.4% Comments - Assume good condition Assume good condition - - Assume good condition Assume good condition - Comments - Assume good condition Assume good condition Wilmington CNG Station PNG-20000 SWALE HYDROLOGY Swale 2 L. Kabrich, EI 4/8/2021 I. SCS CURVE NUMBERS HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. POST-DEVELOPMENT Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 9,297 0.21 Onsite open 39 23,590 0.54 Onsite wooded 30 0 0.00 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =0.75 acres 32,887 sf Composite SCS CN =56 % Impervious =28.3% Comments - Assume good condition Assume good condition Assume good condition Assume good condition - Comments - Assume good condition Assume good condition - - Wilmington CNG Station PNG-20000 SWALE HYDROLOGY Swale 3 L. Kabrich, EI 4/8/2021 I. SCS CURVE NUMBERS HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. POST-DEVELOPMENT Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 4,796 0.11 Onsite open 39 6,669 0.15 Onsite wooded 30 328 0.01 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =0.27 acres 11,793 sf Composite SCS CN =63 % Impervious =40.7% Comments - Assume good condition Assume good condition Comments - - Assume good condition Assume good condition - - Assume good condition Assume good condition Wilmington CNG Station PNG-20000 SWALE HYDROLOGY Swale 4 L. Kabrich, EI 4/8/2021 I. SCS CURVE NUMBERS HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. POST-DEVELOPMENT Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 7,601 0.17 Onsite open 39 6,845 0.16 Onsite wooded 30 3,001 0.07 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =0.40 acres 17,447 sf Composite SCS CN =63 % Impervious =43.6% Comments - Assume good condition Assume good condition Comments - - Assume good condition Assume good condition - - Assume good condition Assume good condition Wilmington CNG Station PNG-20000 SWALE HYDROLOGY Swale 5 L. Kabrich, EI 4/8/2021 I. SCS CURVE NUMBERS HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 Assume:HSG 'A' =100.0% HSG 'B' =0.0% HSG 'C' =0.0% HSG 'D' =0.0% Cover Condition SCS CN Impervious 98 Open 39 Wooded 30 II. POST-DEVELOPMENT Watershed Land Use Breakdown Contributing Area SCS CN Area [sf]Area [acres] Onsite impervious 98 12,041 0.28 Onsite open 39 24,169 0.55 Onsite wooded 30 15,336 0.35 Onsite pond 100 0 0.00 Offsite impervious 98 0 0.00 Offsite open 39 0 0.00 Offsite wooded 30 0 0.00 Offsite pond 100 0 0.00 Total area =1.18 acres 51,546 sf Composite SCS CN =50 % Impervious =23.4% Comments - Assume good condition Assume good condition Comments - - Assume good condition Assume good condition - - Assume good condition Assume good condition Project Name:Wilmington CNG Station Date:4/8/2021 Project Number:PNG-20000 Calculated By:LK Channel Number:SW-1 I. FLOW CALCULATIONS Drainage Area =0.46 acres SCS CN =75 Rational C =0.49 TC =5.00 min I2 =7.44 in/hr Calculated values are for the Raleigh-Durham area. For other areas, values will have to be input manually. I10 =9.70 in/hr Q2 =1.69 cfs Q10 =2.20 cfs II. SWALE CALCULATIONS Proposed Channel Section Longitudinal Slope =1.00% Left Sideslope =4.00 H:V Right Sideslope =4.00 H:V Maximum Vel. =4.50 ft/s Bottom Width =0.00 ft 10-Year Storm Calculations (for Permanent Liner) Match Manning's "n" to Calculated "n" and adjust Depth until Capacity matches Flow (Q10). Depth Flow Area Wetted Perimeter Hydraulic Radius Velocity VR Flow (Q10)Capacity Shear Stress Liner Description/ Selection Calculated [ft][ft2][ft][ft][ft/sec][ft2/sec][cfs][cfs][lb/ft^2]"n" 0.090 1.00 4.00 8.25 0.49 1.02 0.49 2.20 4.08 0.62 Tall Fescue 0.090 0.032 0.75 2.25 6.18 0.36 2.39 n/a 2.20 5.38 0.47 ERONET P300 0.032 ------->NO PERMANENT LINER REQUIRED ------->VELOCITY IS OKAY ------->SHEAR STRESS IS OKAY T = Top; B = Bottom; M = Middle Allowable Partially Vegetated Shear Stress [lb/ft^2] 8.0 Matrix Netting 100% UV Stable Polypropylene Fiber - 0.7lb/sy T: UV-Stabilized Polypropylene - 5lb/1000sf B: UV-Stabilized Polypropylene - 3lb/1000sf Allowabe Partially Vegetated Velocity (f/s) 9.0 Manning's "n" EROSION CONTROL CHANNEL DESIGN Permanent Liner Specifications -ERONET P300 C = 0.020 x CN - 1.0 Conservative assumption For established grass lined channel Proposed conditions, HSG 'A' soils Project Name:Wilmington CNG Station Date:4/8/2021 Project Number:PNG-20000 Calculated By:LK Channel Number:SW-2 I. FLOW CALCULATIONS Drainage Area =0.75 acres SCS CN =56 Rational C =0.11 TC =5.00 min I2 =7.44 in/hr Calculated values are for the Raleigh-Durham area. For other areas, values will have to be input manually. I10 =9.70 in/hr Q2 =0.64 cfs Q10 =0.83 cfs II. SWALE CALCULATIONS Proposed Channel Section Longitudinal Slope =1.18% Left Sideslope =4.00 H:V Right Sideslope =4.00 H:V Maximum Vel. =4.50 ft/s Bottom Width =0.00 ft 10-Year Storm Calculations (for Permanent Liner) Match Manning's "n" to Calculated "n" and adjust Depth until Capacity matches Flow (Q10). Depth Flow Area Wetted Perimeter Hydraulic Radius Velocity VR Flow (Q10)Capacity Shear Stress Liner Description/ Selection Calculated [ft][ft2][ft][ft][ft/sec][ft2/sec][cfs][cfs][lb/ft^2]"n" 0.165 0.75 2.25 6.18 0.36 0.50 0.18 0.83 1.12 0.55 Tall Fescue 0.165 0.034 0.50 1.00 4.12 0.24 1.85 n/a 0.83 1.85 0.37 ERONET P300 0.034 ------->NO PERMANENT LINER REQUIRED ------->VELOCITY IS OKAY ------->SHEAR STRESS IS OKAY T = Top; B = Bottom; M = Middle 8.0 Permanent Liner Specifications -ERONET P300 Matrix Netting Allowabe Partially Vegetated Allowable Partially Vegetated Velocity (f/s)Shear Stress [lb/ft^2] 100% UV Stable Polypropylene Fiber - 0.7lb/sy T: UV-Stabilized Polypropylene - 5lb/1000sf B: UV-Stabilized Polypropylene - 3lb/1000sf 9.0 Manning's "n" EROSION CONTROL CHANNEL DESIGN Proposed conditions, HSG 'A' soils C = 0.020 x CN - 1.0 Conservative assumption For established grass lined channel Project Name:Wilmington CNG Station Date:4/8/2021 Project Number:PNG-20000 Calculated By:LK Channel Number:SW-3 I. FLOW CALCULATIONS Drainage Area =0.27 acres SCS CN =63 Rational C =0.25 TC =5.00 min I2 =7.44 in/hr Calculated values are for the Raleigh-Durham area. For other areas, values will have to be input manually. I10 =9.70 in/hr Q2 =0.51 cfs Q10 =0.67 cfs II. SWALE CALCULATIONS Proposed Channel Section Longitudinal Slope =1.95% Left Sideslope =3.00 H:V Right Sideslope =4.00 H:V Maximum Vel. =4.50 ft/s Bottom Width =0.00 ft 10-Year Storm Calculations (for Permanent Liner) Match Manning's "n" to Calculated "n" and adjust Depth until Capacity matches Flow (Q10). Depth Flow Area Wetted Perimeter Hydraulic Radius Velocity VR Flow (Q10)Capacity Shear Stress Liner Description/ Selection Calculated [ft][ft2][ft][ft][ft/sec][ft2/sec][cfs][cfs][lb/ft^2]"n" 0.110 0.75 1.97 5.46 0.36 0.96 0.34 0.67 1.88 0.91 Tall Fescue 0.110 0.032 0.50 0.88 3.64 0.24 2.51 n/a 0.67 2.19 0.61 ERONET P300 0.034 ------->NO PERMANENT LINER REQUIRED ------->VELOCITY IS OKAY ------->SHEAR STRESS IS OKAY T = Top; B = Bottom; M = Middle 8.0 Permanent Liner Specifications -ERONET P300 Matrix Netting Allowabe Partially Vegetated Allowable Partially Vegetated Velocity (f/s)Shear Stress [lb/ft^2] 100% UV Stable Polypropylene Fiber - 0.7lb/sy T: UV-Stabilized Polypropylene - 5lb/1000sf B: UV-Stabilized Polypropylene - 3lb/1000sf 9.0 Manning's "n" EROSION CONTROL CHANNEL DESIGN Proposed conditions, HSG 'A' soils C = 0.020 x CN - 1.0 Conservative assumption For established grass lined channel Project Name:Wilmington CNG Station Date:4/8/2021 Project Number:PNG-20000 Calculated By:LK Channel Number:SW-4 I. FLOW CALCULATIONS Drainage Area =0.40 acres SCS CN =63 Rational C =0.26 TC =5.00 min I2 =7.44 in/hr Calculated values are for the Raleigh-Durham area. For other areas, values will have to be input manually. I10 =9.70 in/hr Q2 =0.78 cfs Q10 =1.02 cfs II. SWALE CALCULATIONS Proposed Channel Section Longitudinal Slope =2.19% Left Sideslope =4.00 H:V Right Sideslope =3.00 H:V Maximum Vel. =4.50 ft/s Bottom Width =0.00 ft 10-Year Storm Calculations (for Permanent Liner) Match Manning's "n" to Calculated "n" and adjust Depth until Capacity matches Flow (Q10). Depth Flow Area Wetted Perimeter Hydraulic Radius Velocity VR Flow (Q10)Capacity Shear Stress Liner Description/ Selection Calculated [ft][ft2][ft][ft][ft/sec][ft2/sec][cfs][cfs][lb/ft^2]"n" 0.110 0.75 1.97 5.46 0.36 1.01 0.36 1.02 1.99 1.02 Tall Fescue 0.110 0.032 0.50 0.88 3.64 0.24 2.66 n/a 1.02 2.32 0.68 ERONET P300 0.034 ------->NO PERMANENT LINER REQUIRED ------->VELOCITY IS OKAY ------->SHEAR STRESS IS OKAY T = Top; B = Bottom; M = Middle Manning's "n" EROSION CONTROL CHANNEL DESIGN Proposed conditions, HSG 'A' soils C = 0.020 x CN - 1.0 Conservative assumption For established grass lined channel Permanent Liner Specifications -ERONET P300 Matrix Netting Allowabe Partially Vegetated Allowable Partially Vegetated Velocity (f/s)Shear Stress [lb/ft^2] 100% UV Stable Polypropylene Fiber - 0.7lb/sy T: UV-Stabilized Polypropylene - 5lb/1000sf B: UV-Stabilized Polypropylene - 3lb/1000sf 9.0 8.0 Project Name:Wilmington CNG Station Date:4/8/2021 Project Number:PNG-20000 Calculated By:LK Channel Number:SW-5 I. FLOW CALCULATIONS Drainage Area =1.18 acres SCS CN =50 Rational C =0.00 TC =5.00 min I2 =7.44 in/hr Calculated values are for the Raleigh-Durham area. For other areas, values will have to be input manually. I10 =9.70 in/hr Q2 =0.02 cfs Q10 =0.02 cfs II. SWALE CALCULATIONS Proposed Channel Section Longitudinal Slope =1.67% Left Sideslope =4.00 H:V Right Sideslope =4.00 H:V Maximum Vel. =4.50 ft/s Bottom Width =0.00 ft 10-Year Storm Calculations (for Permanent Liner) Match Manning's "n" to Calculated "n" and adjust Depth until Capacity matches Flow (Q10). Depth Flow Area Wetted Perimeter Hydraulic Radius Velocity VR Flow (Q10)Capacity Shear Stress Liner Description/ Selection Calculated [ft][ft2][ft][ft][ft/sec][ft2/sec][cfs][cfs][lb/ft^2]"n" 0.135 0.75 2.25 6.18 0.36 0.72 0.26 0.02 1.63 0.78 Tall Fescue 0.135 0.032 0.50 1.00 4.12 0.24 2.33 n/a 0.02 2.33 0.52 ERONET P300 0.034 ------->NO PERMANENT LINER REQUIRED ------->VELOCITY IS OKAY ------->SHEAR STRESS IS OKAY T = Top; B = Bottom; M = Middle Manning's "n" EROSION CONTROL CHANNEL DESIGN Proposed conditions, HSG 'A' soils C = 0.020 x CN - 1.0 Conservative assumption For established grass lined channel Permanent Liner Specifications -ERONET P300 Matrix Netting Allowabe Partially Vegetated Allowable Partially Vegetated Velocity (f/s)Shear Stress [lb/ft^2] 100% UV Stable Polypropylene Fiber - 0.7lb/sy T: UV-Stabilized Polypropylene - 5lb/1000sf B: UV-Stabilized Polypropylene - 3lb/1000sf 9.0 8.0 50' GAS EASEMENT D B 6 3 3 P G 1 3 1 15' GAS EASEMENT D B 5 7 7 4 P G 1 1 1 3 30' PERMANENT EASEMENT 30' PERMANENT EASEMENT The John R. McAdams Company, Inc. 2905 Meridian Parkway Durham, NC 27713 phone 919. 361. 5000 fax 919. 361. 2269 license number: C-0293, C-187 www.mcadamsco.com M: \ P r o j e c t s \ P i e d m o n t N G a s \ P N G - 2 0 0 0 0 \ 0 4 - P r o d u c t i o n \ W a t e r R e s o u r c e s \ S i t e P l a n \ C u r r e n t D r a w i n g s \ P N G 2 0 0 0 0 - S w a l e s . d w g , 4/ 8 / 2 0 2 1 7 : 4 0 : 0 3 P M , Ka b r i c h , L a u r y n PIEDMONT NATURAL GAS SWALE DRAINAGE AREA DELINEATION MAP GRAPHIC SCALE 0 20 40 80 1 inch = 40 ft. CONTRACTOR SHALL NOTIFY "NC811" (811) OR (1-800-632-4949) AT LEAST 3 FULL BUSINESS DAYS PRIOR TO BEGINNING CONSTRUCTION OR EXCAVATION TO HAVE EXISTING UTILITIES LOCATED. CONTRACTOR SHALL CONTACT ANY LOCAL UTILITIES THAT PROVIDE THEIR OWN LOCATOR SERVICES INDEPENDENT OF "NC811". REPORT ANY DISCREPANCIES TO THE ENGINEER IMMEDIATELY. R Project:Date:2/10/2021 Project Number:Calculated By: KAS Outlet Number: Outlet flowrate =4.69 cfs Pipe diameter = 18 inches Number of pipes = 1 Pipe separation = 0 feet Outlet Velocity = 3.18 ft/sec Zone from graph above =1 Outlet pipe diameter 18 in.Length =6.0 ft. Outlet flowrate 4.7 cfs Width =3.9 ft. Outlet velocity 3.2 ft/sec Stone diameter =3 in. Material =Class A Thickness =12 in. Zone Material Diameter Thickness Length Width 1 Class A 3 12 4 x D(o)3 x D(o) 2 Class B 6 18 6 x D(o)3 x D(o) 3 Class I 13 24 8 x D(o)3 x D(o) 4 Class I 13 24 8 x D(o)3 x D(o) 5 Class II 23 36 10 x D(o)3 x D(o) 6 Class II 23 36 10 x D(o)3 x D(o) 7 1. Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual 2. Outlet velocity based on full-flow velocity DESIGN OF RIPRAP OUTLET PROTECTION WORKSHEET PNG Wilmington PNG-20000 Culvert Special study required 3.2 ft/sec 0 5 10 15 20 25 0 1 2 3 4 5 6 7 8 9 10 Ve l o c i t y ( f t / s e c ) Pipe diameter (ft) Figure 8.06.b.1 Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7