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San Joaquin County DIRECTOR
<br /> Her
<br /> . Donna
<br /> REHS
<br /> -Ar�� co� Environmental Health Department ASSISTANT DIRECTO
<br /> R
<br /> 600 East Main Street Laurie Cotulla, REHS
<br /> Stockton, California 95202-3029 PROGRAM COORDINATORS
<br /> Mike Huggins,REHS,RDI
<br /> Margaret Lagorio,REHS
<br /> /FORS Website: WWW.Sjgov.org/ehd Robert McCleon, REHS
<br /> Phone: (209) 468-3420 Jeff Carruesco,REHS, RDI
<br /> Fax: (209) 464-0138 Kasey Foley,REHS
<br /> June 29, 2009
<br /> Atlantic Richfield Company
<br /> Mr. Sergio Morescalchi
<br /> P.O. Box 1257
<br /> San Ramon, CA 94583 Revision of June 3, 2009 letter
<br /> Subject: ARCO #4932 RO#: 0671
<br /> 16 E. Harding Way APN: 139-020-01
<br /> Stockton, CA 95204 Global ID#: T0607700237
<br /> The San Joaquin County Environmental Health Department (EHD) has been notified by
<br /> your consultant, Stantec that an error was made in the EHD's June 3, 2009 letter that
<br /> modified the sampling and laboratory analyses and frequency of the monitoring events
<br /> for the above subject site. This letter corrects that error and also addresses Stantec's
<br /> request to further change the EHD's requirement for biennial (once every two years)
<br /> sampling of monitoring well DMW-10 to semi-annual.
<br /> Previously, eleven shallow and nine deep monitoring wells, seven ground water
<br /> extraction wells, and two soil vapor extraction wells were sampled and analyzed
<br /> quarterly for gasoline range organics (GRO), benzene, toluene, ethylbenzene, xylene
<br /> (BTEX), the fuel oxygenates (methyl tertiary-butyl ether [MtBE], tertiary-butyl alcohol
<br /> [TBA], tertiary-amyl methyl ether [TAME], ethyl tertiary-butyl ether [EtBE], di-isopropyl
<br /> ether [DIPE]), soluble lead, and the lead scavengers (1,2-dichloroethane [DCA] and
<br /> ethylene dibromide [EDB]).
<br /> The EHD inadvertently added wells DMW-11 through DMW-14 to ARCO's requirement
<br /> to sample and provide laboratory analyses. Since ARCO has no wells with this
<br /> designation, the EHD removes this requirement.
<br /> Following the requirement in the State Water Resources Control Board (SWRCB)
<br /> Resolution #2009-0042 dated May 19, 2009 to reduce quarterly sampling, the EHD
<br /> modifies the sampling requirements for the site as follows:
<br /> 1. Wells MW-4, MW-7, and EW-5 are to be sampled semi-annually and analyzed • 3
<br /> for GRO, BTEX, DCA, and MtBE starting in 2009.
<br /> 2. Monitoring well DMW-10 may be sampled semi-annually and analyzed for MtBE
<br /> during the third quarter in 2009 if technical justification is provided to support the
<br /> need for this additional data. Until the EHD accepts the technical justification,
<br /> DMW-10 is to be sampled biennially and analyzed for BTEX, MtBE, and DCA I
<br /> starting in 2011.
<br /> 3. Wells MW-1, MW-2, MW-5, EW-3, EW-6, DMW-5, DMW-6, and DMW-7 are to 9
<br /> be sampled annually and analyzed for GRO and MtBE, TBA, and DCA starting
<br /> in 2010.
<br /> 4. The remaining wells are to be sampled biennially for GRO, BTEX, the
<br /> oxygenates, and the lead scavengers, starting in 2011. 4o,�, 6,�gq dor nI i w/ a 3v�9 �5
<br /> £ S�r61�5J6�y /
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