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HomeMy WebLinkAboutSW6221102_Soils Report (SHWT)_20221128Scott 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 July 27, 2022 Re: Seasonal High -Water Table Identification and Soil Infiltration Rates: Ashley Heights property, Aberdeen, NC; Hoke County NC parcels 584880001009 & 584980001002. 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-1 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�et) Soils evaluated on this property are typical of those within 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 reported for each proposed location in the tables below. BMP Device Site #1 Test Location SHWT Mansell Color Ksat #1 Ksat #2 Ksat #3 (feet below Notation round surface Not Observed 0-2.5' 2.5'-10' BMP Site 1 within 10' of N/A Loamy Sand Loamy Sand / N/A Elevation 410' surface 12" / hour Sandy Loam 8.5" / hour Scott Cole, NCLSS 312 Copples Road Ext Asheboro, NC 27205 (336) 460-4554 BMP Device Site #2 Test Location SHWT Munsell Color Ksat #1 Ksat #2 Ksat #3 (feet below Notation round surface Not Observed 0-3' 3'-9' 9'-12' BMP Site 2 within 12' of N/A Loamy Sand Loamy Sand / Sandy Clay Elevation 420' surface 12" / hour Sandy Loam Loam (heavy) 8.5" / hour 2.5" / hour BMP Device Site #3 Test Location SHWT Munsell Color Ksat #1 Ksat #2 Ksat #3 (feet below Notation round surface Not Observed 0-2' 2'-3' 3'-10' BMP Site 3 within 10' of N/A Sandy Loam Sandy Clay Loamy Sand / Elevation 444' surface 10" / hour 1.9" / hour Sandy Loam 8.5" / hour 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 of these 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 :0] Proposed Stormwater BMP Site 1 (Elevation 410') SHWT: Not observed within 10' of surface SHWT Elevatioin: -- Ksat 0-2.5' LS: 12" / hour Ksat 2.5' -10' LS/SL: 8.5" / hour Kll� v O o (.0 N v d, Q N O V Proposed Stormwater BMP Site 3 (Elevation 444') SHWT: Not observed within 10' of surface SHWT Elevatioin: -- Ksat 0-2' SL: 1/hour 1 Ksat 2'-3" SC: .9" /hour (/ Ksat X-10' LS/SL: 8.5" / hour Proposed Stormwater BMP Site 2 (Elevation 420') SHWT: Not observed within 12' of surface SHWT Elevatioin: -- Ksat 0-3' LS: 12" / hour Ksat 3'-9' LS/SL: 8.5" / hour Ksat 9'-12' SCL: 2.5" / hour I r %1 inch = 400 feet