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ENGEOGEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS <br /> I N C O R P O R A T E D MATERIALS TESTING <br /> D <br /> Project No. <br /> FEB 0 2 2005 6375.4.002.01 <br /> January 27, 2005 ENVIRONMENT HEALTH <br /> Ms. Wendy Wyels, Chief, Waste Discharge to Land Unit PERMIT/SERVICES <br /> Central Valley Regional Water Quality Control Board <br /> 11020 Sun Center Drive#200 <br /> Rancho Cordova, CA 95670-6114 <br /> Subject: Yosemite Avenue Properties <br /> South Lathrop Specific Plan Area <br /> Lathrop, California <br /> RESPONSE TO CONDITIONAL WORK PLAN APPROVAL FOR <br /> GROUNDWATER STUDY <br /> Dear Ms. Wyels: <br /> ENGEO Incorporated is pleased to present this letter in response to the conditional approval for a <br /> groundwater study of the subject property (Property), located in the Lathrop/Manteca Area of San <br /> Joaquin County, California (Figure 1). The conditional approval was provided in a letter dated <br /> January 12, 2005 by the Central Valley Regional Water Quality Control Board (CVRWQCB). <br /> The following is a clarification of the proposed workplan. <br /> MONITORING WELL CONSTRUCTION <br /> Each monitoring well will be constructed in compliance of the California Well Standards. <br /> Drilling of the five proposed 2-inch diameter monitoring wells will be completed by a California <br /> C-57 licensed well drilling company with a truck-mounted hollow stem auger drill rig equipped <br /> with 8-inch diameter augers. This will allow for an annular seal of three inches between the well <br /> casing and the edge of the borehole. <br /> The proposed screened interval for the monitoring wells is from five to ten feet below ground <br /> surface (bgs). We propose to install the annular seal with a minimum thickness of three feet, <br /> from zero to three feet bgs. The top of the final well screen may be placed deeper than five feet <br /> bgs depending on site conditions during drilling. This would increase the thickness of the <br /> annular seal greater than three feet. <br /> A two-inch bottom well cap will be threaded on the bottom of each well screen section. A <br /> typical well construction diagram is attached. <br /> Each well will be surged, following placement of the filter pack and prior to installation of the <br /> bentonite seal to obtain optimal filling of the annual space. At least 48 hours after completion of <br /> the well installations, each monitoring well will be developed through the use of purging and <br /> 631 Commerce Drive,Suite 100•Roseville,CA 95678•(916)786-8883•Fax(916)786-7891 <br /> w .engeo.com <br />