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1 Royal Oak Savings & Loan Page 4 SION. Main Street, Manteca, California Quarterly Ground Water Sampling Report October, 1992 -January, 1993 Ground Water Grads'ent ' Ground water level measurements were carred out monthly during the quarter on October 24, November 24, and December 28, 1992, as well as durmg the the sampling event our ' January 27, 1993 The vapor exrractaon system installed on MW-2 prevented level measurements from this well during November and December The ground water elevation measurements are tabulated in Table 1 and gradients for the respective months ' are contoured on Figures 2, 3, 4 and 5 The ground water elevations in the monitoring wells on the Royal Oak site were virtually ' unchanged for the months of August through December, 1992 (Figures 2-4) Water measurements taken during the monitoring event on January 27, 1993, show*hat, not only did the water levels all of the wells rise, but also the gradient had reversed with the % ' table contours forming a southeastzrly-trCZIding trough(Figure 5) The ground water contours for this period form a westerly-trending trough, wvhenit ' reversed from an easterly-finding trough. hicoinplete infarmaUM suggests that the westerly-trending trough in the piezometric surface prevails in the late sumo= and through most of the winter months The pattern thea changes to an easterly-Wmdnng trough under the influence of recharge of the aquifer from winter rainfall Summary ofAnalyh'rcal Findings Monitoring wells 7 and 8 were sampled on November 4, 1992, and tested 'none detected" for all analytes Well 2 was not tested at that time as a soil vapor extractign system was installed on MW-2, and access was tempoianly restricted However, all three wells were sampled on �anuary 27, 1993, and were N D for,all analytes tested(see Table 2) I is worth noting that air samples tested from the soil vapor system at the start up showed T H moons of greater than 2,500 ppm The levels have declined rapidly and, as of December 25, 1992,the levels are "none detected" We have enclosed a summary of the air testing performed at the site since the soil vapor system was turned on(Table 4) tRecommendadons Wf IF recommends that the soil vapor extraction system be removed fi ani the site We also recommend that the site be considered for closure The San Joaquin County Envmmmental Health Department has condended that the contaminated soils left in place at the comer was the cause of the intermittent ground water contamination in wells 2 and 7 The soils are now clean, via the soil vapor adraction system, and ground water samples indicate that the ground water is no longer contaminated