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GROUND ZERO ANALYSIS, INC. <br /> >> 2291 W. March Lane; Suite 127D ` `` '` 1., `i u ' <br /> ,. . F <br /> .Stockton, California 95207' <br /> Telephone: (209) 952-3481 <br /> Facsimile: (209) 952-9892 <br /> May 21, 1996 ,< <br /> Ms.'Linda Turkatte <br /> San Joaquin County-Public Health Services <br /> 4('"_ Environmental Health Division <br /> =` 445 North San Joaquin Street t <br /> PO Box 388 _ <br /> Stockton, CA 95201-0388 <br /> Subject: Second Quarter 1996 Groundwater Monitoring and Sampling Report <br /> Knowles/Roek Property, 102 South Wilson Way, Stockton, California <br /> Dear Ms. Turkatte: <br /> Ground Zero Analysis, Inc. (Ground Zero) has prepared this report for groundwater monitoring <br /> and sampling performed during the second quarter 1996 at the subject site (Figure 1). Activities <br /> during the second quarter of 1996 included monitoring groundwater elevations, purging and <br /> sampling groundwater, and analyzing samples for total petroleum hydrocarbons as gasoline <br /> (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl tert-butyl ether (MTBE). <br /> Groundwater monitoring was conducted on April 24, 1996. The depth to groundwater-.was <br /> J; measured in each well and subtracted from the wellhead elevation to determine groundwater <br /> elevation. Water levels in the wells rose an average of 3.04 feet.since last monitored on <br /> 4 February 8, 1996. Groundwater flow was generally easterly at gradients ranging from <br /> approximately 0.002 to 0.01 feet per foot. Two groundwater gradient maps were generated <br /> using the April 24, 1996 monitoring data. The gradient determined using wells shallower than <br /> 65 feet is shown on Figure 2, and the gradient using data from wells deeper than 65 feet is <br /> , L depicted on Figure 3. Recent groundwater monitoring data are summarized in Table 1. <br /> Monitoring logs are included in Attachment A. <br /> Groundwater samples were collected from wells MW1 through MW13 on April 24 and 25, <br /> 1996. At least three well casing volumes were purged from wells MW-1 through MW-13 prior <br /> to sampling, except for MW-3 which went dry after purging 21/2 gallons. Physical parameters <br /> (pH, conductivity, temperature) were monitored during purging and allowed to stabilize prior <br /> to sampling. Purged water was contained in 55-gallon drums approved by the Department of <br /> Transportation and remains on site pending analytical results. Purge logs are presented in <br /> Attachment A. <' <br /> 'At <br /> H..r groundzc\rock\2gm1996 <br />