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San Joaquin County DIRECTOR
<br /> Donna Heran,REHS
<br /> .� Environmental Health Department
<br /> � _•�j. .p ASSISTANT DIRECTOR
<br /> Q y� 600 East Main Street Laurie Cotulla,REHS
<br /> Stockton, California 95202-3029 PROGRAM COORDINATORS
<br /> �..
<br /> _ Carl Borgman,RENS
<br /> Mike Huggins,REHS, RDI
<br /> Website: www.sjgov.org/ehd Margaret Lagorio,REHS
<br /> Phone: (209)468-3420 Robert McClellon,REHS
<br /> Fax: (209)464-0138 ,teff Carruesco, REHS,RDI
<br /> K
<br /> December 31,2008 asey Foley,REHS
<br /> John and Margaret Marci
<br /> 20 Mobile Lane
<br /> Crescent City, California 95531-8409
<br /> Subject: John and Margaret Marci Property
<br /> 2969 Loomis Road
<br /> Stockton, California 95205
<br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Work Plan -
<br /> Additional Dual Phase Extraction Pilot Test, dated October 30, 2008, prepared by Geological
<br /> Technics Inc. (GTI) on your behalf. The work plan was submitted in response to an EHD letter
<br /> dated October 17, 2008, recommending further pilot studies of soil vapor extraction (SVE) and/or
<br /> dual phase extraction (DPE) that include the assessment of total petroleum hydrocarbons (TPH)
<br /> quantified as gasoline (TPHg) and quantified as diesel (TPHd) in the total contaminant recovery
<br /> rate and sustainability.
<br /> In the work plan, GTI proposes three pilot tests using DPE involving high vacuum technology to
<br /> simultaneously extract groundwater and soil vapor first from monitoring well MW-5, then from
<br /> bioventing extraction wells EW-1 and EW-101. GTI proposes each DPE test to last five days at
<br /> each well tested with nine-day breaks between tests to allow equilibrium conditions to be
<br /> reestablished. During each pilot test, GTI proposes to collect three gas and three groundwater
<br /> samples to be analyzed for benzene, toluene, ethyl benzene, and total xylenes (BTEX); TPHg, and
<br /> TPHd. GTI will monitor vacuum influence using observation wells MW-4, MW-7, 1W-1, IW-101,
<br /> EW-1,EW-101, EW-2, EW-102,EW-3 and EW-103.
<br /> The EHD approves the work plan but has some reservations; the principal ones are concerning the
<br /> small screen intervals of some wells and the screen depths relative to the depth-to-water. During
<br /> the fourth quarter 2008 groundwater monitoring event on October 28, 2008, depth-to-groundwater
<br /> was measured at approximately fifty-three-and-a-half feet below surface grade (bsg). MW-5 and
<br /> MW-7 are screened between fifty-five and seventy feet bsg, and MW-4 is screened between
<br /> approximately sixty and eighty feet bsg. Thus there is a minimum of one-and-a-half feet of water
<br /> above the screened intervals of MW-5 and MW-7 and over six feet of water above the screened
<br /> interval of MW-4. Under these conditions, the DPE test design may not be practical. As noted
<br /> above, GTI proposes to use EW-1, screened between forty-two and forty-four feet bsg, and EW-
<br /> 101, screened between fifty-five and fifty-seven feet bsg, to perform the two other pilot tests. The
<br /> EHD is concerned that a two-foot screened interval may not be practical for performing DPE, and
<br /> that EW-101 does not have sufficient screen above the current depth-to-groundwater. Lastly, GTI
<br /> proposes to analyze gas samples for TPHd using Environmental Protection Agency (EPA) method
<br /> 8015M. Instead, gas samples should be analyzed for TPHd by EPA Compendium Method TO-17
<br /> using appropriate sorbent tubes tailored to target TPHd.
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