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California Regional Water Quality Control BoardC Central Valley Region Robert Schneider,Chair Alan C.l�loyd,l'h.D. - - ...._,.�._..,..� Arnold Agency Secretary Sacramento Main Office Schwarzenegger 11020 Sun Ccnter Drive#200,Rancho Cordova,California 95670.6114 Governor Phone(916)464-3291•FAX(916)464-4645 http://www.waterboards.ca.gov/centralvalley 9 March 2006 Ms. Lucy Thater 1313 E. Acampo Road P.O. Box 437 Acampo, California 95220 DOCUMENT REVIEW, FORMER TUCKER CONSTR UCTION, 336 EAST LOCUST STREET, LODI,SAN JOA QUIN COUNTY I reviewed the Quarterly Report—Fourth Quarter 2005(Report),received 28 February 2006, and prepared on your behalf by your consultant Advanced GeoEnvironmental,Inc. (AGE). The Report provides the analytical results of the groundwater monitoring of four monitoring wells (MW-1 through MW-4) for the investigation of petroleum hydrocarbon contamination in soil and groundwater at your property. While groundwater results from the three newer wells(MW-2 through MW-4) were non-detect, the maximum groundwater results reported from one older well (MW-1) were: Total Petroleum Hydrocarbons as gasoline (TPHg), 700 micrograms per Liter (gg/L); benzene, 2.6 gg/L; toluene,20 gg/L; ethylbenzene, 44 gg/L; and xylenes,255 µg2. To date, fuel oxygenates and lead scavengers have not been detected in soil or groundwater at this site. The Report states that the depth to groundwater was 50+0.8 feet (ft) below ground surface(bgs). The groundwater gradient(Figure 3A)varied across the property, from 0.01 ft/ft to the west in the upgradient, northeastern corner of the property ,to 0.005 ft/ft to the southwest in the downgradient direction of the property. The Report recommends continued groundwater monitoring. Comments: 1) Quarterly monitoring results reported during 2005 have shown that groundwater gradients and downgradient flow directions have been highly variable during each of the three consecutive quarters, which is not typical of most investigations. To date,there has been no attempt to provide a rationale for the discrepancy. Three quarters of groundwater monitoring water measurements are represented in the following table of the Quarter Sampled versus the Monitoring Well's Reported,Water Level in feet above mean sea level (famsl): Quarter Q Well MW-1 fainsl Well MW-2 faYnsl Well MW-3 famsl Well MW-4 famsl Second Q 2005 2.83 2.60 2.63 2.81 Third Q 2005 1.93 1.61 1.74 2.93 Fourth Q 2005 1.21 0.91 1.01 1.21 Also note (Figure 2, Enclosed)the location of the four monitoring wells. Wells MW-1 and MW-4 are in closer proximity (17 feet total distance)to each other than Wells MW-1,MW-2 and MW-3, (30 and 35 feet distance). Wells MW-1 and MW-4 reported equal shallow groundwater(water table) elevations California Environmental Protection Agency Ci Recycled Paper