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HomeMy WebLinkAboutSW6221008_Soils/Geotechnical Report_20221027Scott Cole, NCLSS 312 Copples Road Ext Asheboro, NC 27205 (336) 460-4554 Double D Engineering, PLLC Attn: Mr. Lee Humphrey 150 S. Page Street Southern Pines, NC 28387 April 29, 2022 Re: Seasonal High -Water Table Identification and Soil Infiltration Rates: "Stone Creek" Philippi Church Road, Raeford, NC; Hoke County NC parcel 494540001006 Soil conditions and infiltration rates were evaluated and measured on the above -referenced property within the proposed storm water BMP device. Work was conducted in accordance with Parts A-2 and C-I of the North Carolina Department of Environmental Quality Stormwater Design Manual. Soil samples were evaluated with a hand auger. SEASONAL HIGH WATER TABLE IDENTIFICATION Seasonal High Water Table depth is determined by field evaluation for soil wetness conditions which are indicated by the presence of redoximorphic (redox) features with chroma colors of 2 or less (in Munsell color notation) in mottles or the horizon matrix, and at times, saturated soil conditions and/or free water within the soil profile. Colors of chroma 2 or less due to relic minerals from parent material (underlying rock), anaerobic activity created by placement of fill material, or soil textural class transitions (perched water) are not considered as indicators for seasonal high water. Upon determination of SHWT depth, an additional 6" will be deducted from the observed depth to account for capillary fringe water movement above the SHWT. Stormwater infiltration trenches are designed to ensure the lowest point is at least two feet above the Seasonal High Water Table (SHWT). SATURATED HYDRAULIC CONDUCTIVITY (K,,t) Soils evaluated on this property are typical of those within the Blaney Soil series. These soils are moderately well drained soils with varying rates of permeability. Infiltration rates are measured to determine if soil conditions are suitable for the installation of stormwater infiltration devices. Infiltration rates are measured using a Johnson Constant Head Permeameter. Measurements are recorded at varying intervals until equilibrium was reached. The SHWT and Infiltration rates for the stormwater BMP devices are reuorted in the table below. BMP Device Site Test Location SHWT Munsell Color Ksat #1 Ksat #2 Ksat #3 (feet below Notation round surface 15' bgs 5Y 8/1 0-4' 4'-5' 5'-20' BMP Site l 2.5Y 7/1 Loamy Sand / Sandy Clay Mixed soils Elevation 173' Sandy Loam Loam with drainage 12" / hour 5" / hour mottles (Ksat value not measured Scott Cole, NCLSS 312 Copples Road Ext Asheboro, NC 27205 (336) 460-4554 CONCLUSION Field evaluation of hydraulic conductivity provides estimations of soil infiltration rates; however, methods used to measure these rates can influence the results. Side walls of the bore hole are "smeared" by the soil auger as the hole is prepared and loose soil in the bottom of the hole is placed in suspension when water is applied; both factors negatively influence water infiltration rates. To help overcome these issues, after excavation of each infiltration trench, it is recommended the trench bottom and sidewalls be raked and dusted with pulverized limestone. These are practices that have been in place within the on -site wastewater industry to help loosen the soil and aid in restoration of soil structure. I am pleased to be of service in this matter and can be contacted at your convenience should you have any questions concerning information within this report. Thank you, Scott Cole North Carolina Licensed Soil Scientist - NOTE. RDII OF BEAVER CREEK IS FII`E PROPER LIME. BEARINGANO OISTAtJC SH G4YN TAKING FROM AERIAL PHOTO. HEREO �.�Jt; fJGODEOAREAT 110 FIELD SO RVEYWADE THIS DATE REI:, AIfI NATURAL AID' j 164 „F USAC WE TL.':'i2 LINE r_t8�.._---- _.-._---- - - --- - -'-- f RE IAAHI NATURAL 'WOODED AREATO764 172 CF=N SPACE i 768 1� / Proposed Stormwater BMP PROPOSED 2 ,.aSER SHWT: 15' bgs SHWT Elevation: 173' o FH K -4' L ! L: sat 0 S S 12" ! h r ou - Ksat 4'-5' SCL: V ! hour Ksat 5'-20' mixed soils with drainage mottles: Not Measured PR E FIRE •A iV35F Hy RAII .� _ ORM WATER TREATMENT 276 L 4� ro i 2 N 1. 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