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mr—MP <br /> GEO GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS <br /> I N C O R P O R A T E D MATERIALS TESTING <br /> YEOProject No. <br /> FEB 1 5 2005 6375.4.002.01 <br /> February 11,2005 ENVIRONMENT <br /> HEALTH <br /> Ms. Wendy Wyels, Chief, Waste Discharge to Land Unit PERMlT/SERVI <br /> ES <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 presents this letter in response to comments contained in the conditional <br /> approval for a groundwater study of the subject property(Property), located in the Lathrop/Manteca <br /> Area of San Joaquin County, California (Figure 1). The conditional approval was provided in a <br /> letter dated January 12, 2005 by the Central Valley Regional Water Quality Control Board <br /> (CVRWQCB). The following information is a clarification of the proposed workplan based on <br /> the specific comments in the conditional approval letter. <br /> Comment #1: "As described, the annular seal may be as little as three feet. Based on the site <br /> constraints it may be possible to increase the depth of the annular seal, generally, it is not <br /> necessary to screen the water table to monitor land application areas. In addition, the auger <br /> size is not described so it is impossible to evaluate the well construction for compliance with <br /> the California Well Standards Bulletin 74-90 (Part II, Section C), which requires a minimum <br /> two-inch annular seal. Please submit a drawing of the proposed well construction." <br /> ENGEO has recorded the depth to the top of the shallowest aquifer at several other sites in the <br /> Lathrop area. The depth to the water surface was measured continuously using down-hole data <br /> loggers to monitor for seasonal fluctuations over several years of monitoring. The measured <br /> depths varied widely from approximately 4 to 19 feet below ground surface (bgs) in response to <br /> seasonal fluctuations and well location. The intent of the proposed well construction is to allow <br /> for groundwater monitoring throughout the anticipated wide ranges of depths to groundwater. <br /> However, certain construction details may change from the proposed design given site conditions <br /> observed during well installation. <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 /> 631 Commerce Drive,Suite 100•Roseville,CA 95678• (916)786-8883•Fax(916)786-7891 <br /> www.engeo.com <br />