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ENVIRONMENTAL HEALTH DEPARTMENT
<br /> SAN JOAQUIN COUNTY
<br /> Unit Supervisors
<br /> Donna K Heran,RE H S
<br /> Drrecror 304 East Weber Avenue, Third Floor Carl Borgman,R E H S
<br /> 1 _ Al Olsen,REX S. Stockton, California 95202-2708 Mike Huggins,R E H S,R D I
<br /> Pro ram Marra erDouglas W Wilson,R E H S
<br /> Laurie A CatttIIa,RE-H S Telephone (209) 468-3420 Margaret Lagono,R E H S
<br /> Program Manager Fax (209) 464-0138 Robert McClellon,R E H S
<br /> 1 F Mark Barcellos,R E_H S
<br /> I �
<br /> PETER LENZ JUN 17
<br /> 2902
<br /> 1 6465 PACIFIC AVE
<br /> STOCKTON CA 95207
<br /> 1 RE Howard Lenz Property SITE CODE. 2182
<br /> 1648 Shaw Road
<br /> 1 Stockton CA 95215
<br /> San Joaquin County Environmental Health Department has reviewed the "Cone
<br /> 1 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 GeoEnvironrnental, Inc and has the following comments
<br /> 1 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 /> 1• 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 /> 1 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 /> 1 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 /> 1 CPT-1 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 /> 1 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 /> 1 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 /> 1 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 /> 1 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 /> 1 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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