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63 <br /> EnvirotacticS <br /> An Earth Systems Company <br /> 4.3 Hydrogeologic Framework <br /> 4.3.1 Hydrostratigraphy <br /> Within the Piedmont Plateau Physiographic Province and Site vicinity, two "major" aquifer systems are <br /> present. The surficial regolith forms an unconfined aquifer while the underlying bedrock forms an <br /> unconfined to semi-confined fractured bedrock aquifer. These aquifers are well-documented to interact, <br /> hydraulically, with one another. <br /> The water table aquifer at the Site occurs at an approximated range in depth of 25 to 35 feet bgs. No areally <br /> continuous stratification of the regolith is evident. The bedrock is expected to have a significant hydraulic <br /> conductivity based on the pump test performed for the Proposed Community Well. <br /> Nevertheless, the hydrologic behavior of the surface regolith and the fractured bedrock will be different <br /> because of their different structural compositions. <br /> 4.3.2 Groundwater Supply Wells <br /> Other than the Proposed Community Well, two (2) other groundwater supply wells were identified nearby, <br /> the Rigsbee Well, on site, and the Griffin Well on the adjacent property. <br /> As shown on its Orange County Existing Well/Septic System Authorization, the Rigsbee Well is 505 feet <br /> deep, with 35 feet deep well casing and a static water depth of 25 feet bgs. <br /> While no formal permit data were available for the Griffin Well (i.e., it appears to pre-date the Orange County <br /> Database/Permitting Requirement), the owner indicated that, to his knowledge, the Griffin Well depth is 75 <br /> feet, with the pump at 65 feet, and the static water depth at 35 feet. <br /> As shown in the Yadkin Well Company's report, the Proposed Community Well's depth is 665 feet, its static <br /> well level is 33 feet below the top of the casing, and the casing is 2 feet above the ground's surface. <br /> 4.3.3 Observed Water Levels <br /> Based on the existent water levels information for the area', a hydraulic gradient of approximately 0.04 <br /> feet/feet was estimated for both the surface regolith and in the bedrock. <br /> 4.3.4 Hydraulic Properties <br /> Geraghty & Miller (1996) and Arcadis (2005) conducted slug tests and pump tests in both the shallow <br /> (regolith) wells and the deep (bedrock) wells at a site nearby.The hydraulic conductivity from the slug and <br /> pump tests at that site nearby varied from 0.1 feet/day to 12 feet/day, and the storage coefficient varied <br /> from 0.00001 to 0.4. <br /> 'April 2005 Arcadis Groundwater Flow Model and Remedial System Design Report-UNC Chapel Hill,Airport Road Waste Disposal Area,Chapel Hill, <br /> North Carolina <br /> Envirotactics, LLC Page 13 of 20 Groundwater Modeling Report <br /> (732) 449-0077 Project No.6704 <br />