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ATC Associates Inc. <br /> MV <br /> 1117 Lone Palm Avenue, Suite B <br /> Modesto,California 95351 <br /> 209-579-2221 <br /> ASSOCI ATES t N c. fax: 209-579-2225 <br /> Groundwater Monitoring Well Installation <br /> Five groundwater monitoring wells will be installed to evaluate the horizontal extent of impacted <br /> groundwater. Historical laboratory analytical data indicate the groundwater plume extends <br /> beyond the subject site boundaries. Development of the areas immediately adjacent to the site, <br /> have significantly reduced the potential for ideal placement of off-site wells. One monitoring <br /> well will be installed in the median in the vicinity of SB 11 and one monitoring well will be <br /> installed adjacent to SB9 to evaluate the lateral extent of impacted groundwater upgradient with <br /> respect to the former location of the USTs. Two monitoring wells are proposed to be installed <br /> north of Harding Way at 1107 and 1119 Harding Way to evaluate the groundwater plume <br /> downgradient of the former location of the USTs to the northeast. A fifth monitoring well <br /> location is proposed along the eastern edge of the alley bordering the subject site to the east. This <br /> location will provide data in the downgradient of the former location of the USTs to the east. <br /> Historical data indicate the groundwater flow direction at the site is generally to the northeast <br /> and east,northeast. The proposed monitoring locations are shown on Figure 2. <br /> Four of the groundwater monitoring wells will be installed using a hollow stem auger equipped <br /> drilling rig. The monitoring well proposed to be installed along the eastern edge of the alley <br /> bordering the subject site to the east will be installed using a limited access drilling rig due to the <br /> concentration of utilities in this area. Drilling will be conducted by a State-licensed (C57) <br /> drilling company. A field geologist will be present to log the boreholes. Soil samples will be <br /> collected at five-foot intervals for logging purposes. These soil samples will also be field <br /> screened with a Photoionization Detection (PID) meter or similar instrument for the presence of <br /> organic vapors. Descriptions of soil types encountered will be recorded on well logs. Soil <br /> samples will not be collected for laboratory analyses unless field observations indicate potential <br /> petroleum hydrocarbon impact. Drill cuttings will be stored on site in 55-gallon drums, pending <br /> proper disposal. <br /> The monitoring wells will be constructed of 2-inch inside diameter schedule 40 PVC well screen <br /> and casing with approximately 20 feet of 0.010 inch slot screened PVC. The wells will be <br /> installed to a depth of approximately 57 feet below grade. A sand pack will be placed in the <br /> annulus of the well extending from the bottom of the well screen to approximately three feet <br /> above the top of the screen. Approximately two feet of bentonite will be placed on top of the <br /> sand pack and hydrated with potable water. The remaining annulus will be grouted to surface <br /> with cement grout. To protect the integrity of the wells, locking, watertight well plugs will be <br /> installed on each well and a watertight wellhead labeled "monitoring well" will be set in concrete <br /> over each well. <br /> sA22493\reports\Wkp1n_we11 inst2006.doc 4 <br />