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GEOMATRIX <br /> likely in the 20 to 30 foot bgs range, where the highest PHCs were found in the vicinity of the <br />' tanks) will be submitted for analysis of PHCs Groundwater samples will be collected from <br /> two discrete depths in each boring, one from about 20 feet bgs (depth of highest groundwater <br />' concentration in onsite borings), and one from the bottom of the boring These samples will <br /> also be submitted for laboratory analysis of PHCs <br /> 2.1.2 Monitoring Well <br /> The monitoring well location will be selected in consultation with PHS/EHD after evaluation of <br />' the data collected from the exploratory bonngs The location will be based on the highest <br /> concentrations of PHCs detected in the groundwater samples collected from the exploratory <br />' borings If none of the bonngs contains detectable PHC concentrations, the location will be <br /> based on the predominant direction of groundwater flow The pilot boring for the well will be <br />' drilled with a hollow-stem auger ng to a maximum depth of approximately 40 feet Soil <br /> samples will be collected every 10 feet for comparison with samples collected from the <br /> corresponding exploratory boring <br /> The monitoring well will be constructed of 2-inch diameter polyvinyl chloride (PVC) blank <br /> casing with machine-slotted PVC well screen Based on data collected from the initial <br /> monitoring well installations at this site, the slot size will be 0 02 inches and the filter pack will <br />' comprise No 3 Lonestar sand or equivalent The well screen will be 10 feet in length and the <br /> screen will be set across the zone of highest groundwater PHC concentration, as determined <br />' from the exploratory boring The filter pack will be installed through the augers in the annulus <br /> between the well casing and the formation, and will extend vertically from the bottom of the <br /> boring to about 3 feet above the top of the screened interval The augers will be withdrawn as <br />' the filter pack is emplaced A minimum of a 1-foot thick bentonite seal (pellets or chips) will <br /> be placed above the filter pack as a transition seal The remainder of the annulus, from the top <br />' of the bentonite seal to the surface, will be grouted with neat cement A steel well cover and <br /> locking cap will be set in the cement around the top of the well The well cover will be <br /> installed in a flush-mount, precast concrete valve box with a traffic-rated steel cover The <br /> surface will be sloped away from the valve box to discourage entry of surface runoff <br /> After installation is complete, the well will be developed using a bailer and/or a submersible <br /> pump During development, the electrical conductivity, pH, temperature, and clarity of the <br /> development water will be monitored Well development will proceed until the water is <br /> relatively colorless and free of sediment and the field water-quality parameters have stabilized <br /> Water generated during development and water sampling activities will be placed in temporary <br /> 1`MQJEC %6437 000/6437 Wk Pin Site 3 doc 5 <br /> I <br />