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*104 Californiz�egional Water Quality C�itrol Board
<br /> Central Valley Region f
<br /> g ECEI v. ��
<br /> Katherine Hart, Chair
<br /> Linda S. Adams 11020 Sun Center Drive#200, Rancho Cordova, California 95670-6114 t G.Brown Jr.
<br /> Acting Secretary for Phone(916)464-3291 •FAX(916)464-4645 TV;�'Y OLu overnor
<br /> Environmental Protection
<br /> http://www.waterboards.ca.gov/centraIvaIIey
<br /> EMARONMENTA,L HFAtTM
<br /> Ms. Janet Heikeld PERM1S/fg"VM 1
<br /> Olympian
<br /> 1300 Industrial Road, Ste. 2
<br /> San Carlos, CA 94070
<br /> DOCUMENT REVIEW, JIMCO TRUCK PLAZA, 1022 EAST FRONTAGE ROAD (AKA 22502 SOUTH
<br /> HIGHWAY 99), RIPON, SAN JOAQUIN COUNTY(REGIONAL BOARD CASE# 390718)
<br /> I reviewed the First Half 2011 Groundwater Monitoring Report (Report), received 28 April 2011 from
<br /> your consultant, Conestoga-Rovers and Associates. The Report documents semi-annual groundwater
<br /> monitoring conducted from 28 February 2011 to 2 March 2011. Maximum groundwater monitoring
<br /> results were total petroleum hydrocarbons as gasoline(TPHg), 140 micrograms per Liter (ug/L); TPH
<br /> as diesel (TPHd), 420 ug/L; and methyl tert butyl ether (MTBE), 250 ug/L. Groundwater flow direction
<br /> was towards the northwest at 0.0008 ft/ft. The Report recommended eliminating the following wells
<br /> from the monitoring program: MW-3, MW-14 (sic, MW-4), MW-5, MW-7, MW-11, MW-12, MW-13,
<br /> MW-14, MW-17, MW-18, MW-19, MW-20, and the Ripon Farm Service (RFS) MW-2, and RFS MW-3.
<br /> The proposal to continue semi-annual groundwater monitoring is conditionally approved as follows:
<br /> • Water levels will be measured for all wells (except DW-1, RFS MW-2, and RFS MW-3).
<br /> • Analyses for each sampled well will be limited to those constituents detected during 2010.
<br /> • DW-1 will be monitored for all constituents annually during the 1St quarter of each year.
<br /> • MW-3, MW-7 and MW-13 will remain on semi-annual monitoring. MW-3 reported TPHg, 120 ug/L
<br /> and benzene, 5.9 ug/L in July 2010. MW-7 reported TPHg, 170 ug/L and benzene, 5.4 ug/L in
<br /> July 2010. Both MW-3 and MW-7 had reported non-detects for all constituents for multiple
<br /> quarterly sampling events prior to July 2010, which may indicate plume instability.
<br /> MW-13 (TPHg, 69 ug/L) is located next to the Jimco Above-Ground Tanks (AGT) that
<br /> reported a piping leak in 2005. Continued sampling of MW-13 is necessary for the AGT case for
<br /> your Site and to help define the extent of the TPHd plume.
<br /> • If the second half 2011 monitoring report data support a request for closure, then revise the
<br /> monitoring report into a closure report written in accordance with the 16 April 2004 Regional Water
<br /> Quality Control Board- Central Valley Region-Appendix A — Reports Tri-Regional Board Staff
<br /> Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites.
<br /> Include soil and groundwater mass estimates, an evaluation of risk from soil and soil vapor, and
<br /> estimates of time to reach water quality goals in a closure report due 30 September 2011.
<br /> If you have any questions, please contact me at (916) 464-4615 or via e-mail at
<br /> jr-)-arton@waterboards.ca.gov
<br /> TA
<br /> `dames L.L. Barton, P. G.
<br /> Engineering Geologist
<br /> cc: Nuel Henderson, San Joaquin County Environmental Health Department, Stockton
<br /> Ron Scheele, Conestoga-Rovers & Associates, 5900 Hollis St., Ste. A, Emeryville, 94608
<br /> California Environmental Protection Agency
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