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' Diamond Lumber Manteca Quarterly Groundwater Monaonng Page 8 solidified concrete grout generated during monitoring well installation,are currently stored under along the west side of the covered lumber storage building k c 8.0 PURGED GROUNDWATER DISPOSAL ' SRK requested permission from the City of Manteca, Public Works Department, to dispose of purged water generated during the sampling of monitoring wells SRK-MW1 and SRK-MW3 Authorization ' from the Public Works Department had not been received by SRK at the time of the time of sampling A copy of this correspondence is provided in Appendix H 9.0 REGISTERED WELLS LOCATED WITHIN 2,000 FEET ' Pursuant to the San Joaquin County PHS/EHD request (correspondence dated January 22, 1993),SRK performed a record search of registered wells (private, municipal,monitoring, irrigation) m d within 2,000-feet of the Diamond Lumber facility and identified 23 registered wells, composed aunicipal water wells, 14 monitoring wells A copy of this information is provided in Appendix I Current static water levels and surface elevations for these 23 registered wells were not available at the California ' Department of Water Resources Because of this, it is not currently known whether or not these wells support or dispute SRK gradient calculations s� 10.0 SUMMARY OF FINDINGS ' Monitoring wells BEI-MW4, BEI-MW5 and BEI-MW6 were sampled initially by BEI in 1989, and three times by SRK (October 1991, August 1992, and February 1993) Elevated levels of volatile ' hydrocarbons and the constituents of BTEX have been detected during each sampling event Analytical data obtained during SRK sampling events(presented in Table 2)indicates that contaminant levels have consistently been elevated in BEI-MW5 above concentration levels detected in BEI-MW4 ' or BEI-MW6 BEI-MW5 is located along the south property line adjacent to the Southern Pacific Railroad right-of-way (Figure 1) Lead was also detected in each of the three BEI monitoring wells ' Static water level elevations collected February 5, 1993 were approximately 4 feet higher than the previous sampling event (August 1992) but are comparable to static water levels recorded during April ' 6, 1992 A comparison of analytical data collected April 6, 1992 with data collected February 5, 1993 indicates a general reduction in contaminant levels in the SRK series monitoring wells Lead ' concentrations dropped in SRK-MW1 from 26 ppb (April 1992) to 3 ppb (February 1993), in SRK- _ MW3 from 57 ppb (April 1992) to 3 ppb (February 1993) Volatile hydrocarbon levels in SRK-MW2 dropped from 1,800 ppm (April 1992) to 3 ppb (February 1993) Monitoring wells SRK-MW1, SRK-MW2 and SRK-MW3 have been sampled during each quarterly sampling event (November 1991,April 1992,August 1992 and February 1993) Analytical results from the February 1993 sampling event indicate that trace amounts of BTEX were detected for the first time in SRK-MW1 and SRK-MW3 and not in SRK-MW2 Low levels of volatile hydrocarbons were only Deny w. Steffen Robertson and i4rsten