ARCHIVED REPORTS_XR0007373 CASE 2

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AT&T—Lodi,Quarterly Groundwater Monitoring Report No 3 ATC Project No 75 75128 0001 October 4, 2001 concentration of 58 ug/L, 20 feet farther to the south No BTEX or MTBE were detected in grab groundwater samples collected from the bonngs, with the exception of total xylenes detected m the grab sample from one boring at 12 ug/L 3.0 PURPOSE AND SCOPE OF SERVICES The investigation outlined in this report was primarily designed as a limited program of sampling and ch arucal testing of groundwater samples at the above-mentioned site Mr Harlan Knoll of the San Joaquin County Environmental Health Department requested in May 1999 that this investigation be performed as a prerequisite to obtaining site closure The program was designed to help further assess the lateral and vertical extent of diesel fuel constituents its the groundwater onsite Specifically,these tasks included • Purging and sampling three groundwater morutorung wells, • Chemically testing groundwater samples by a California state-certified analytical laboratory,and • Preparing a report summarizing the subsurface mvestigation with findings, conclusions and recommendations ' 4.0 INVESTIGATION AND LABORATORY METHODS 4.1 FIELD PROCEDURES Site activities were conducted under the supervision of a State of Califorrra Registered Geologist having five or more years of professional experience in groundwater hydrology The field operations were supervised by a qualified Geologist designated by the supervising Registered Geologist Field operations personnel were trained in accordance with 29 CFR 1910 (40-hour OSHA health and safety training) Untrained field operations personnel or visitors were not allowed on the site during field operations. 4.2 GROUNDWATER MONITORING WELLS 4.2.1 WATER LEVEL MEASUREMENT Three monitoring wells were sampled during this quarterly monitoring and sampling round The locations of the monitoring wells are presented on Figure 2 The procedure for sampling the monitoring wells consisted of initially measuring the depth to the groundwater surface in each well ut hzi g a decontaminated Sohnst Model 101 flat tape electrical water-level meter Groundwater surface depth was determined to the nearest 0 01 foot and referenced to the top of casing for each well Groundwater elevations were determined from an arbitrary datum. of 37 feet, the approximate surface elevation of the site based on the U S Geological Survey Lodi North 7 5- minute Quadrangle map dated 1967 (photorevised 1980) Table 4-1 lists the date of the sounding and the groundwater surface elevations Before use and prior to subsequent measurements in each well, the measuring equipment was decontaminated ' 2