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California Regronal Water Quality CMitrol Board f :�,: \� Central Valley Region ' M:. Robert Schneider,Chair Gray Davis Winston H.Hickox Sacramento Main OGovernor Secreraryfor Office Environmental Internet Address: http://www.swrcb.ca.gov/rwgcb5 Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 Phone(916)255-3000-FAX(916)255-3015 15 May 2002 Z G 1 A s a L 1 ` Tony Arnaiz Central Valley Construction PO Box 830 Lathrop, CA 95330 RF.VIEW OUARTERLYMONITORING AND ADDITIONAL CHARACTERIZATION REPORT, CENTRAL VALLEY CONSTRUCTION, 146 ALO ROAD,LATHROP,SANJOAOUIN COUNTY I reviewed the 20 April 2002 Quarterly Monitoring and Additional Characterization Report(Q1-2002 Report) submitted by John Cummings&Associates(JCA) on behalf of Central Valley Construction. The Q1-2002 Report presents monitoring and sampling data for three monitoring wells and one domestic well, a 2,000 foot well receptor survey, and the results of push probe soil sampling near the former above ground storage tank (AGT) area to define the extent of soil contamination. The three on-site monitoring wells and the on-site domestic well were sampled on 11 March 2002. The depth to water was approximately 12 feet below ground surface, and the groundwater flow direction was to the northwest at 0.002 feet/foot. The water samples were analyzed for total petroleum hydrocarbons as gasoline(TPHg) and diesel(TPHd),benzene,toluene, ethyl benzene,total xylenes(BTEX), and fuel oxygenates and fuel additives. In addition, all four water samples were also analyzed for lead by EPA Method 200.7, and a full suite of volatile organic compounds by EPA Method 8260B. This was the second sampling event for the on-site monitoring wells that were installed in November 2001. The on-site domestic well noted as"POT W"in JCA's Q 1-2002 Report was non-detect for all constituents, and only TPHd was identified in monitoring wells MW-1 and MW-2 at a maximum of 100 micrograms per liter(µg/l). Based on the results of the Q4-2001 and the Q1-2001 monitoring events,you may discontinue analyzing water samples for fuel oxygenates,lead, and volatile organic compounds. The results of the well receptor survey identified 23 water supply wells within 2,000 feet of the site. The wells are mostly domestic water supply for individual residences along Klo Road. The wells are completed with six to eight inch diameter PVC or steel casing with a total depth ranging from 80 to 233 feet. The depth of the sanitary well seals for each well was not available to JCA, and therefore,not reported. Besides the on-site domestic well, the nearest water supply well is approximately 150 feet north and down gradient of the former underground storage tank and AGT areas. On 11 March 2002,JCA completed five push probe soil borings near the former AGT area to define the lateral and vertical extent of soil contamination. (Previous soil samples collected in the AGT area during excavation activities identified TPHg at 1.5 milligrams per kilogram(mg/kg), and TPHd ranging from 3.9 to 450 mg/kg.) Starting at ten feet, soil samples were collected at five-foot intervals to a total depth of 30 feet. All soil samples were analyzed for TPHg,TPHd, and BTEX constituents, and all soil samples were non-detect for all constituents California Environmental Protection Agency �a Recycled Paper The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swrcb.ca.gov/rwgcb5