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'a California Regional Water Quality Control Board
<br /> Central Valley Region 01.
<br /> Karl E.Langley,.ScD,P.E.,Chair
<br /> Linda S.Adams 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Arnold
<br /> Secretaryfor Phone(916)464-3291 •FAX(916)464-4645 Schwarzenegger
<br /> Environmental http://www.wateibowds.ca.gov/cenualvalley Governor
<br /> Protechon
<br /> 29 April 2009
<br /> IMr. Matt Gabris
<br /> Sara Lee Bakery Group, Inc
<br /> 3500 Lacey Rd.
<br /> Downers Grove, IL 60515
<br /> ' DOCUMENTS REVIEW, FORMER COLUMBO/TOSCANA BAKERIES, 1444 S. LINCOLN STREET,
<br /> STOCKTON, SAN JOAQUIN COUNTY(REGIONAL BOARD CASE#390825)
<br /> I reviewed the Sara Lee Bakery Group, Inc. (Sara Lee) Quarterly Groundwater Monitoring Report (First
<br /> Quarter—January 2009) (1Q2009 Report), the Biosparge Detailed Evaluation and Monitoring Well
<br /> Installation Plan (EvaluationMorkplan), and the Vapor Intrusion Survey- Soil Gas Sampling Report
<br /> _ .
<br /> respectively, from,yo _,su4taRt
<br /> PSC Environmental Services Inc (PSC) for your Site. The 1Q2009 provides the results of routine
<br /> quarterly groundwater monitoring conducted on 27 January 2009. The Evaluation was,submitted in
<br /> response to the Pilot Study Workplan requirement in my 23 December 2008 letter. The Workplan
<br /> proposes the installation of three monitoring wells in the B and C Zones of the shallow aquifer, to
<br /> provide vertical and lateral definition of the groundwater plume, and additional data for the Pilot Study
<br /> Workplan. The VIS Report provides the results.of a soil gas survey conducted on 30 January 2009, to
<br /> evaluate potential threats from vapor intrusion emanating from residual soil and groundwater
<br /> contamination.
<br /> 1 The 1Q2009 describes the approximate depths of four permeable water-bearing zones correlated
<br /> across the proposed commingled plume sites (Columbo/Toscanna, Texaco, Chevron, ARCO,
<br /> ' Transmission Store, and Dolly Madison) in-the shallow, unconfined aquifer as:
<br /> • Shallow zone, a perched water zone located 20' below ground surface (bgs) to 36' bgs;
<br /> • A zone, at 37' bgs to 57' bgs;
<br /> • B zone, at.70' bgs to 90' bgs; and
<br /> • C zone, at 102' bgs to 122' bgs.
<br /> 1 Depth to water in all wells (Shallow, A, B, and C zones) varied from 20' bgs to 21' bgs across the Site.
<br /> The groundwater gradient and flow direction in the A Zone were reported as 0.002 feet/feet towards
<br /> the south-southwest. Maximum groundwater concentrations were total petroleum hydrocarbons as
<br /> gasoline (TPHg), 130,000 micrograms per Liter (ug/L); benzene, 10,000 ug/L; toluene, 17,000 ug/L;
<br /> ethylbenzene, 3,900 ug/L; xylenes, 19,000 ug/L; methyl tert-butyl ether(MTBE) 1,400 ug/L; tertiary
<br /> butyl alcohol (TBA), 99 ug/L; 1,2-dichloroethane (1,2-DCA), 38 ug/L; di-isopropyl ether (DIPE),
<br /> ' 0.84 ug/L; and ethyl tertiary butyl ether(ETBE), 0.76 ug/L.
<br /> The Evaluation provides additional discussion of the BioSparging groundwater remediation proposal
<br /> chosen as the most technically feasible and cost effective remediation in the 2 December 2009
<br /> Feasibility Study and Remedial Evaluation (FS/RE). The Evaluation references the Transmission Store
<br /> (TS) at 515 W. Charter Way for a biosparging pilot study conducted in 2008, and states that the
<br /> geology at both sites is similar. The Evaluation states that the TS site conducted a second, longer
<br /> 1 Biosparging (also, Air Sparging and Ozone) pilot test that concluded 27 March 2009, since there were
<br /> California Environmental Protection Agency
<br /> ' �a Recycled Paper _
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