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EXPLORATION DRILLING <br /> Mobil <br /> Prior to any drilling activities <br /> Envirosbeen <br /> secured will verify that <br /> necessary drilling p <br /> . 11 be conducted so as not to <br /> disruptlacdv�ies at prol be jectts to ed and Endvirrilling s willlobtain and review available <br /> public data on subsurface eology and if warrantedthe location of wells <br /> , <br /> within a half-mile of the pgroject site will be identified. Drillers will be <br /> notified in advance so that drilling equipment can be inspected prior to <br /> performing work- <br /> Drilling <br /> The subsurface investigations are typically performed to assess the lateral <br /> and vertical extent of petroleum hydrocarbons present in soils and <br /> groundwater. Drilling methods will be selected to optimize field data <br /> requirements as well as be compatible with known or suspected subsurface <br /> geologic conditions. <br /> Monitoring wells are installed using a truck-mounted hollow-stem auger <br /> drill rig or mud-rotary drill rig. Typically,the hollow-stem rig is used for <br /> wells 0 f t d feet,if subtypically <br /> ace conditions are favorable.drilled using mud-rotary techniques. When <br /> ells greater <br /> than loo feet deep are typ Y <br /> mud rotary drilling is used, an electric log will be performed for additional <br /> lithological information. Also during mud rotary drilling,precautions will <br /> be taken to prevent mud from circulating contaminants by using a conductor <br /> casing to seal off contaminated zones. Samples will be collected for <br /> lithologic logging by continuous chip, and where needed by drive sample or <br /> core as specified by the supervising geologist. <br /> (`eoorobe Drillin¢ Methods <br /> The geoprobe system utilizes a percussion hammer and hydraulically- <br /> powered system to drive probes which are approximately 1.75-inches in <br /> diameter to the desired depth and retrieve soil and groundwater samples. <br />