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4 <br /> 1.0 INTRODUCTION <br /> Upgradient Environmental Consultants was retained by Mrs Marjorie Conrady in March, <br /> 1998 to provide site remediation and groundwater monitoring services at her property <br /> located at 1002 Yosemite Street in Stockton, California The property is the former location <br /> of a gasoline service station that was demolished about 1980, when the underground fuel <br /> storage tanks were removed Upgradient submitted a Corrective Action Plan in April, 1998, <br /> which was approved by Michael Infurna of the Environmental Health Division of San <br /> Joaquin County Public Health Services (PHS/EHD) in mid-April, and the corrective action <br /> was performed in late April The purpose of this report is to present the rest Its of <br /> monitoring activities since May The investigation is currently managed for Mrs Conrady <br /> by Mr James Dyke of Neumiller& Beardslee, Attorneys at Law <br /> 2.0 BACKGROUND <br /> The property is located on the northeast corner of Acacia and Yosemite street, in a <br /> predominantly residential area of west Stockton (Figure 1) The site is now vacant, but was <br /> operated as a gasoline service station from 1961 to 1978 The fuel storage tanks and <br /> dispenser islands were removed in 1980, and observers noted evidence of an unauthorized <br /> release of gasoline Investigation of the extent of contamination began in 1990, and was <br /> completed in 1997 <br /> Site remediation was begun in April 1998, when seven bonngs were drilled and a slurry of <br /> Oxygen Releasing Compound (ORC) was infected into each boring to provide oxy)'en to <br /> enhance natural bioremediation of the hydrocarbons Since that time, groundwater ha, been <br /> monitored on a regular basis to track changes in dissolved oxygen and hydrocarbon <br /> concentrations <br /> 3.0 MONITORING PROCEDURES AND RESULTS <br /> 3.1 Depth to Groundwater <br /> The depth to groundwater in each well was measured on September 24, and the depth, were <br /> recorded on the Well Monitor Report (Appendix A) Depths were measured with a Solinst <br /> water level sounder to an accuracy of 0 01 foot <br /> Water level and casing elevation data are tabulated in Table I and were used in constructing <br /> a groundwater gradient map (Figure 2) The map is similar in appearance to those for <br /> previous monitoring events, and all of the maps indicate that the water table has a natural <br /> slope to the northeast and a trough along the west (street) side of the site In Septemb,-r, the <br /> gradient was approximately 0 003 ft/ft, down from 0 006 ft/ft in July <br /> 2 <br />