ARCHIVED REPORTS XR0012673 - Laserfiche WebLink

Home Browse Search

r4IMLEM A55MMEN!REPOW INCLUDINO OUAMEnLY M=T0"N0"EP"'f 6- t399 East Yosemno Avenue,Manteca,CaII10(n a F-� 3.3 Soil Sam le Anal [cal Results A total of four soil samples from the monitoring well borings were submitted for chemical analysis. The selection of samples for analysis was based on PID screening, odor observation, soil classification and depth. All soil samples were analyzed for BTEX, EDC, EDB, and TPH, as gasoline, by EPA Method 8260 and CAL DHS Draft TPH (modified). Toluene was detected in the soil sample from 23.5 feet depth in MW-4 at a concentration of 0,006 ppEn (Table 2). Benzene, a#hylbenzene, xylenes, EDC EDB, and TPH, as gasoline, above detectable limits. No concentrations of chemicals above detectable were not found lfrom cross-sections!olresults hand limits werefoui ihownothe n Figure4 ad on Table previous investigations ss s 3.4 M1onitarin Weil instattation Groundwater data collected during previous investigations indicated that the approximate groundwater flow direction beneath the site was to the west. Monitoring wells MW-4 and MW-5 were located to determine the upgradient and ambient groundwater conditions. MW-4 and MW-5 were constructed as 4-inch groundwater monitoring wells. Monitoring well MW-1 B was constructed as a 6-inch-diameter recovery well by drilling out the existing 2-inch-diameter well MW-1A. The monitoring wells were installed, developed, and sampled according to the standard operating procedures in Appendix A. Monitoring well construction details are included in Appendix B. 3.5 Groundwater Level Measurements Groundwater level measurements were taken by Aegis on February 1, 1991, from the three existing on site wells (MW-1A, MW-2, and MW-3). Water level measurements were again taken on February 27,April 1,April 23; and May 28, 1991. All measurements were made from y referenced wellhead elevations and measured to the nearest 0.01 foot. As discussed in the previous sections, MW-1B, MW-4, and MW-5 were installed on June 20, 1991. On June 27, 1991, wellhead and casing elevations of the five on site wells (MW-1 B,MW-2,MW-3, MW-4, and MW-5)were surveyed and referenced to a City of Manteca datum by aCalifornia-licensed surveyor. Water level measurements taken on June 26 and July 22, 1991, were referenced to the newly surveyed elevations. Table 5 summarizes the groundwater elevations for the site for 198B through 1991. Groundwater elevations we - observed to range from 14.03 to 14.15 feet above MSL during the July 22, 1991, sampling :vent. The potentiometric surface of the groundwater at the site ` on July 22, 1991, is shown on Figure 5. The direction of groundwater flow beneath the site � is approximately toward the west-northwest, ft. Depth-to-groundwater dunhydraulic g g tabes sampling int for the July 22, 1991, data was approximately 0.002 ft/ft. event was approximately 26 to 27 feet below existing surface grade. �o-0eac.�PT