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� upw i .a '�'e»"" -� F`3 �, ':,� �A �.r� va•� � "'�� '�# �'�� ° �+ � ,�* a��a°C. Y* <br /> ya <br /> P. <br /> , <br /> Mr. Kyle Christie <br /> January 22, 1990 <br /> Page 3 <br /> t. Constituents in the groundwater sample from well PR-1 ase below detection limits with the <br /> exception of xylene. Xylene is present in the sample from well PR-1 at a concentration very <br /> ! close to the laboratory detection limit. BETX constituents are detectable in the samples from <br /> wells BHG-1, E-2, E-5, E-8, E-10, E-11, and E-12. In all samples except PR-1 the benzene <br /> concentration exceeds California Department of Health Services (DHS) Maximum Contaminant <br /> Levels (MCLS). <br /> Table 2 summarizes the benzene concentrations for the seven quarterly sampling events, May <br /> 1988 through December I989. This table shows that benzene concentrations have varied in <br /> each well over time. Benzene concentrations in wells E-2, E-11, and E-12 have increased <br /> since the summer quarter 1+89 (August 22, 23, and 24, 1989). Monitoring wells E-5, E-8, <br /> and E-10 have shown a dei':,ease in benzene concentrations since the summer quarter 1989. <br /> Benzene concentrations in well BHD-1 have not changed significantly sire, the spring quarter <br /> 1989. A contour map of December 4 and 5, 1989, benzene concentrations in groundwater <br /> is shown on Figure 1. <br /> Thi: concentration of ethylbenzene is above the DHS MCL in monitoring well BHD-1. The <br /> concentration of toluene is above the DHS Drinking Water Action Level in monitoring wells <br /> BHD-1 and E-10. The concentration of xylene is above DHS MCLS in monitoring well <br /> BHD-I and E-10. <br /> Groundwater 1'?.;,v <br /> W Water-level elevations at the site are being measured in each well on a biweekly basis using <br /> an electronic water level indicator. The levels are measured relative to top-of-casing elevations <br /> in order to determine groundwater elevations and monitor possible changes in flow direction. <br /> Since late April 1988, the groundwater flow direction has been influenced by the recovery <br /> system. Sometime in April 1989, the recovery pump stopped operating. The malfunction was <br /> detected in lune 1989, and the recovery system is currently being repaired. Figure 2 is a <br /> wat,r Ievel contour map for December 4, 1989. The figure shows that groundwater has almost <br /> returned to static conditions. During static conditions, groundwater flows to the northeast. <br /> - Conclusions <br /> Groundwater samples collected during tl:e fall quarte.. 1989 show that benzene concentra- <br /> tions have increased in wells E-2, E-11, and E-12 since the summer quarter I989. This <br /> increase could be the result of solubilization of product from the soil. Water levels at the site <br /> have increased approximately 3/10 of a foot since the summer quarter:989. These increased <br /> level, may have been sufficient to solubilize product from the soil, thus increasing the benzene <br /> concentrations in some of the wells. Groundwater samples collected during the fall quarter <br /> 1989 show that benzene concentrations have decreased in wells E•5, E-8, and E-10 since the <br /> sumirer quarter 1989. <br /> �r <br /> BROWN AND CALDWELL <br /> 723 55TREET SACRAMENTO CALIFORNIA 95&14.7092.1761444.0123 -- <br /> I <br />