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ENVIRONMENTAL
<br /> HEALTH DEPARTMENT
<br /> SAN JOAQVIN COUNTY Unit Supervisors
<br /> Donna K.Henan,R.E.H.S. Weber Avenue,Third Floor Carl Borgman,R.E.H.S.
<br /> 304 EastDirector Mike Huggins,R.E.H.S.,R.D.I.R.w.-, Al• Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S.
<br /> )468-3420 Margaret Lagorio,R.E. .
<br /> Program Manager Telephone: (209
<br /> Robert McClellon,R.E.H.S.
<br /> Laurie A.Cotulla,R.E.H.S. Fax: (209) 464-0138 Mark Barcellos,R.E.H.S,
<br /> Program Manager
<br /> JUN 17 200Z
<br /> PETER LENZ
<br /> 6465 PACIFIC AVE
<br /> STOCKTON CA 95207
<br /> RE: Howard Lenz Property SITE CODE: 2182
<br /> 1648 Shaw Road
<br /> Stockton CA 95215
<br /> San Joaquin County Environmental Health Department has reviewed the "Cone
<br /> Penetrometer Testing Report-January 2002" dated April 17, 2002, and the "Soil Vapor
<br /> Extraction Pilot Test Report"dated May 16, 2002, that were prepared on your behalf by
<br /> Advanced GeoEnvironmental, Inc. and has the following comments.
<br /> In January 2002, three twin cone penetrometer test (CPT) borings were advanced onsite.
<br /> The initial borings provided lithological data; the twin borings were used to collect discrete
<br /> groundwater samples from targeted zones. Specifically, one water sample was collected
<br /> from CPT-1 at a depth of 92-96 feet below surface grade (bsg), two samples were
<br /> collected from CPT-2 at depths of 76-80 feet bsg and 92-96 feet bsg, and two from CPT-3
<br /> at depths of 74-78 feet bsg and 92-96 feet bsg. In addition, one soil sample was collected
<br /> from CPT-1, at a depth of 31 feet bsg. Analytical results from this investigation indicate
<br /> that the groundwater contaminant impact appears to be mostly delineated. Total
<br /> petroleum hydrocarbons (TPH) as gasoline, TPH as diesel, toluene, ethylbenzene and
<br /> xylenes were detected in the water sample from CPT-1, near the source area, at
<br /> concentrations below the maximum contaminant levels (MCL). Groundwater from this
<br /> same unit, hydrologic unit-2 (HU-2), was not found to be impacted in the outlying borings,
<br /> CPT-A and CPT-3. A discretely screened monitoring well should be installed to sample
<br /> HU-2 near the CPT-1 location on a routine basis to show minimal contaminant
<br /> concentrations at that depth in the area of the release. If several quarters of monitoring
<br /> show the contaminant concentrations to continue to be below the MCL's, vertical definition
<br /> of the plume can be assumed to have been determined, and preparation of a Problem
<br /> Assessment Report.(PAR), as recommended in the CPT report, would be appropriate.
<br /> On January 14, 2002, a soil vapor extraction pilot test was conducted onsite. The test
<br /> was run on vapor well VW-2 for a duration of approximately 8 hours. Both similarly
<br /> screened vapor wells, VW-3 and VW-4, as well as monitoring wells MW-2, MW-4, MW-5,
<br /> MW-6 and MW-7, were used as observation points during the test. Based on the
<br /> measurements collected during the test from the similarly screened vapor wells, an
<br /> effective radius of influence was calculated as approximately 25 feet. However, the
<br /> monitoring wells, which are screened at a lower depth, all registered an influence greater
<br /> than 0.1 inches of water during the test. The report recommends that additional feasibility
<br /> testing be performed, and that a PAR be prepared. Feasibility studies to address
<br /> impacted soil and groundwater can proceed. At least two different remedial methods that
<br /> seem likely to remediate each impacted media should be evaluated.
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