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------ ----- - Wens WESTERN 618-ENGINEERS Decontariij n a ion Prior to well installation, all sard packs will be subjected to a fresh water wash and sorted Co avoid any contamination which might find its way into the wells. prior to installation, slotted casing or well screens will be steam cleaned. The hollow--stem augers will be steam cleaned between borings to liminate cross-contamination. Wcll Co: struction Log In .- Adition to the �nformition included in the lithol4-)g3.c logs kept for soil borings (i.e. , grain size, visible contaminants, "sniffer" readings, color changes, groundwater elevation, thickness of individual units) , a well construction log will be kept for the groundwater monitoring wells. it will include the diameter of the borehole, the size, , kind and depth of casing, the size, kind and depth of well screen or slotted casing, a grouting record (materials, intervals and placement methods) , the size and interval of thn gravel pack, the total depth of the well, type of the well, the date tested, static water level prior to the test, type of test pump or bailer, total time of the of pumping/bailing, the rate of pumpitig/bailing and the final water level. Groundwater Measurement and Sampling Following development, the water level in the wells will be allowed to equilibrate for a minimum of 48 hours. Before groundwater level Ali measurements are taken, each well will be surveyed from a reference point to the top of the well casing. A graduated tape will be used with a conductivity probe to measure the depth to water or free product that may be floating on the surface of the water. This type of probe will enable accurate measurement of the free product-water interface, if present, and will therefore indicate thickness of that floating product. As a standard practice, at least two measurements will be made. if two measurements of static water level made within a few minutes do not agree within 0.01 or 0.02 feet, measurements will be repeated until the reason for the lack of agreement is determined or until the results are shown to be reliable. Before sampling, the wells will be pumped or bailed to remove 5 casing volumes of water. Sampling of the groundwater beneath the free product layer and sampling the free product will then be accomplished by bailing the welll with a pre-cleaned bailer. Care will be taken to not contaminate the groundwater sample with surface water or free product. Water samples will be taken in triplicate. Duplicate samples will be forwarded to the primary laboratory and the third sample will be analyzed by WEGE portable lab (See Table I for types of analyses to be performed) .