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California Regional Water Quality Control Board <br /> Central Valley Region <br /> Earl E. Longley,ScD, P.E.,Chair <br /> Linda S. Adams Arnold <br /> s.ec�,c,r orl �o�, Sacramento Main Office Schwarzenegger <br /> E e(r elnme/ra/ 11020 Sun Center Drivc#200 Rancho Cordova_California 9567461 14 (;orern e <br /> NI roninolec on Phone(916)464-3291 •FAX(916)464-4645 <br /> hup./byxvw.waterboards.ca.eov/ccntralvallev <br /> 1 April 2008 IDI������� <br /> Mr. Donald Rodgers <br /> 11900 South Union Rd. APR — 3 2008 <br /> Manteca, CA 95336 ENVIRONMENT HEALTH <br /> PERMIT/SERVICES <br /> DOCUMENTS REVIEW, THE TRANSMISSION STORE, 515 WEST CHARTER WAY, <br /> STOCKTON, SAN JOAQUIN COUNTY(REGIONAL BOARD CASE # 390891) <br /> 1 reviewed the First Quarter 2008 Status Report (Report) and the Biosparge Pilot Test Work Plan <br /> (Workplan), received on 20 March 2008 from your consultant Shaw Environmental Inc. (Shaw). <br /> The Workplan is consistent with the Shaw recommended remedial option in the Feasibility Study, <br /> received 14 January 2008 and conditionally approved in my <br /> 23 January 2008 letter. The Report provides the results of the quarterly groundwater monitoring <br /> conducted on 4 February 2008. <br /> The Report states that the maximum groundwater concentrations in February 2008 were total <br /> petroleum hydrocarbons as gasoline, 97,000 micrograms per Liter (ug/L); benzene, <br /> 5,900 ug/L; ethylbenzene, 1 ,900 ug/L; toluene, 1,000 ug/L; and xylenes, 5,530 ug/L. Upgradient <br /> onsite well MW-2R could not be sampled due to a car parked over the well. <br /> The Workplan proposes the installation of one 1" or 2" diameter biosparge remediation well with a <br /> two-foot screen placed approximately 50 feet below ground surface (bgs) in a sand unit <br /> (enclosed Figures 3 and 5) near the highest reported concentration of petroleum hydrocarbons <br /> (enclosed Figure 4). The Figure 3 cross section shows two fine-grained sediment (silts) units exist <br /> above (32 feet bgs) and below (55 feet bgs) the target sand unit at the proposed well screen <br /> location. Depth to water has varied from approximately 18 to 21 feet bgs during the preceding <br /> three quarters of groundwater monitoring. <br /> The stated purposes for the biosparging pilot test are to determine.. <br /> • the oxygen injection radius of influence (ROI) for full scale treatment design, <br /> • the oxygen consumption rate by measuring oxygen and carbon dioxide gas levels in select <br /> well headspace(s), and <br /> • existing nutrient levels necessary to sustain aerobic degradation of petroleum <br /> hydrocarbons. <br /> During the biosparging pilot test, monitoring wells MW-4RS, MW-4RD, MW-7S, MW-81, <br /> MW-11 D and VW-2D will be observed for changes in water levels and dissolved oxygen (DO) in <br /> water every 15 minutes for the first hour and every 30 minutes during the second hour. Vapor <br /> concentrations of petroleum hydrocarbons will likewise be monitored using a photo ionization <br /> detector (PID) at the above listed temporal frequencies from vapor extraction wells VW-1 S, <br /> California Environmental Protection Agency <br /> p�� Rec_I(/ed paper <br />