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GROUND ZERO ANALYSIS, INC. <br /> 1714 Main Street <br /> Escalon, California 95320 <br /> Telephone: (209) 838-9888 `' <br /> Facsimile: (209) 838-9883 ENVIRONMENTAL HEALTH DIVISIONf <br /> 304 E. Weber Ave. Third Floor <br /> October 12, 1999 P. O. Box 388, S ockton CA 95201-0388 <br /> Approved <br /> Denied E <br /> Mr. Harlin Knoll Conditions . Ff1 f> Dpi <br /> San Joaquin County Public Health Services (Q <br /> Environmental Health Division Date it z by AJ <br /> 304 East Weber Avenue, Third Floor - <br /> Stockton, CA 95202 <br /> Subject: Workplan for Additional Subsurface Investigation North of Well MW5 <br /> 1140 W. Hammer Lane, Stockton, California <br /> Dear Mr. Knoll: <br /> This letter report is submitted to present a proposed workplan to conduct additional subsurface <br /> investigation at the referenced site (Figure 1) in accordance with a written request by Mr. Harlin Knoll of <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) dated July 8, <br /> 1999. The general scope of work will consist of drilling and sampling one soil boring north of well MWS <br /> to investigate the vertical and lateral extent of residual soil contamination, installing, developing, and <br /> sampling a temporary groundwater monitoring well in the boring to investigate the northern extent of the <br /> dissolved contaminant plume, properly abandoning the temporary well and boring, and preparing a <br /> technical report that summarizes the methods and results of the investigation. <br /> Scope of Work <br /> Groundwater in the vicinity of well MW5 contains total petroleum hydrocarbons as gasoline (TPHG) at <br /> elevated levels. The lateral extent soil and groundwater contamination has been essentially defined to the <br /> east, south and west, but not to the north. The current depth to groundwater at the site is approximately 35 <br /> feet below the ground surface (bgs). The proposed boring/temporary well will be drilled to a depth of <br /> approximately 45-50 feet below ground surface (bgs) in the Hammer Lane right-of-way, approximately 50 <br /> feet north of well MW5 to filrther investigate the extent of subsurface contamination. The location of the <br /> proposed boring is shown on Figure 2. <br /> Spectrum Exploration (C57 #512268) will advance the boring using a drilling rig equipped with hollow <br /> stem augers. Soil samples will be collected for logging and identification at 5-foot depth intervals. <br /> Samples will be collected using a 2-inch diameter California Split Spoon sampler lined with brass tubes. <br /> The portion of the sample to be analyzed will be immediately capped and preserved in an iced cooler at a <br /> temperature of approximately 4° Centigrade. Up to three soil samples will be submitted for analysis of <br /> TPHG, and benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl tert butyl ether (MTBE) using <br /> EPA methods 8015m and 8020, respectively, to investigate the extent of residual gasoline contamination in <br /> soil. Selection of soil samples for laboratory analysis will be based on field evidence of gasoline <br /> hydrocarbon impaction, such as discoloration, odors, and FID readings, as well as lithologic changes. <br /> groundze\knowles.ham\reports\wp 1099.doc <br />