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California Regional Water Quali ' Control Board
<br /> Central Valley Region p;;4
<br /> Robert Schneider Chair
<br /> Terry Tamminen
<br /> EN��nUNNlt�u Arnold Schwarzenegger
<br /> Secretary for Sacramento Main Office v�CES
<br /> Environmental Internet Address: http://www.swrcb.ca.gov/rwgcb5 FERMMSER Governor
<br /> Protection 11020 Sun Center Drive#200 Rancho Cordova,CA 95670-6114
<br /> Phone(916)464-3291
<br /> 6 May 2004
<br /> Mr. Sheldon Heckman, c/o Kama E. Herrigfeld
<br /> Herum Crabtree Brown
<br /> 2291 W. March Lane, Ste.B-100
<br /> Stockton, CA 95207
<br /> WORKPLAN REVISION REQUEST,RIVER CITY PETROLEUM/FORMER CONNELL MOTOR LIFT
<br /> TRUCK, 2211 NORTH WILSON WAY, STOCKTON, SANJOAQUIN COUNTY
<br /> On 30 December 2004, I reviewed and approved the Interim Soil Vapor Extraction and Site Assessment Work
<br /> Plan (Workplan) dated 14 November 2003,prepared on your behalf by your consultant Advanced
<br /> GeoEnvironmental, Inc. (AGE). One task in the Workplan proposed installation of five multi-level (multiple well
<br /> screens per boring) groundwater monitoring wells (multi-level wells), with screened intervals at:
<br /> • first water, 90-100 feet below ground surface(bgs);
<br /> • a gravelly sand interval at 150 feet bgs, and
<br /> • another gravelly sand interval at 175-185 feet bgs.
<br /> The Workplan stated that 185 feet bgs may not be the vertical extent of the petroleum hydrocarbon and
<br /> 1,2-dichloethane groundwater contamination. In discussions with AGE staff, the analytical results (data) from
<br /> the March 2004 Cone Penetrometer Testing(CPT) investigation support that statement, although the entire report
<br /> has not been submitted to the Regional Board.
<br /> On 1 April 2004, in an email titled Interim—River City Data, AGE staff attached a table of analytical data(table)
<br /> from the March 2004 CPT investigations and the CPT boring logs. The table showed CPT grab groundwater data
<br /> taken at depth. At the maximum reported depth of sampling in the source area, 225 feet below ground surface
<br /> (bgs),the groundwater data showed total petroleum hydrocarbons as gasoline (TPH-g), 42,000 micrograms per
<br /> liter(µg/L); benzene, 2,600 gg/L; toluene, 3,700µg/L; ethylbenzene, 610 µg/L; xylene, 5,800 µg/L; all fuel
<br /> oxygenates, <50 to <500 µg/L, ethylene dibromide, 68 gg/L; and 1,2-dichloroethane (1,2-DAC), 68 gg/L.
<br /> TPH-g, B-E-T-X and 1,2-DCA were detected at much lower levels in groundwater at 200 feet bgs approximately
<br /> 50 feet downgradient from the source area.
<br /> On 15 April 2004 in another email titled Scope of Work RC Petro,AGE proposed modifications to the Workplan,
<br /> to target deeper zones identified by the March 2004 CPT data and grab groundwater samples, specifically a
<br /> gravelly sand unit identified from 195-200 feet bgs, and a reported continuation of the gravelly sand unit from
<br /> 245-250 feet bgs, with a potential maximum depth of 300 feet bgs for the multi-level wells. The email included
<br /> two geological cross sections showing the gravelly sand units and contaminant plumes at 150 feet bgs, and a
<br /> larger gravelly sand unit between 180 feet and 223.6 feet bgs, the maximum email-reported depth of the CPT
<br /> investigation. The email gave a"final week in April"time schedule for the new multi-level wells.
<br /> I appreciate your proactive response through AGE,to quickly modify the Workplan by increasing the targeted
<br /> depth of the investigation. After conducting a site inspection on 16 March 2004, and seeing the contaminated
<br /> sample retrieved by CPT from the 225-foot depth, I emailed AGE on 9 April 2004 to consider proposing an
<br /> additional deeper monitoring well(s) to verify the CPT data.
<br /> California Environmental Protection Agency
<br /> Ca Recycled Paper
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