FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

i- Four exploratory borings (B-1., :B-2, B-3 an.d B-4) were drilled and sampled in April 2003 as the preliminary environmental assessment.(PEA) around the former underground tank pit at.the WWTP. The soil. samples collected in those borings, showed that contaminants were not detected. Groundwater samples showed very.:low levels of dissolved TPHD, with one relatively elevated level TP.HD of 33,000 micrograms perliter (ug/1) at B-2 in a downgradient location. BTEX, MTBE and related oxygenates were not revealed in any groundwater sample. On the basis of this data collected for this study,limited leakage from. the.former underground tank had occurred. The dissolved plume had migrated a short distance downgradient of the former tank pit to the north-northwest. 2.0 2000-foot Radius Well Survey and Sensitive Receptor Survey Wright performed a 2000-foot .radius search .for wells around the WWTP soil borings site. .The search used the available information from the:Department of Water Resources files and City of Tracy files to docurnent municipal, domestic, agricultural, industrial wells in the search radius. The information is compiled into a summary table together with a map showing the well locations (see Figure l and Table 1). The well locations are approximate and based upon the information on the individual well log; in. some cases the State Well. Completion. Reports well location, as well as logging and well construction information may .not be precise or may be incomplete. Groundwater monitoring wells installed for regulatory compliance issues are not plotted on this search No wells appear to be located on-site. The well search revealedindustrial andirrigation wells at Holly Sugar to the north and one City of. Tracy test well. in. the radius. Several domestic water wells are beyond the 2000-foot search radius and one domestic well has been destroyed. The nearest domestic wells occur to the northeast of the search radius and industrial waste ponds. Based on the available well screen. and',sealing information, the wells appear to be screened below the uppennost aquifer sampled for this study. On this basis of this data, Wright does not interpret that the on-site dissolved contaminant is a potential well sensitive.receptor threat. 3.0 Field Methods—Drilling and Sampling Exploratory Borings Exploratory borings were drilled at the'1:ocations shown on Figure 2. Drilling pen-nits were secured from SJC/EH.D, and underground-utility clearance 'were performed prior to doing the fieldwork and some borings were relocated :in consultation with WWTP personnel due to the presence of very large utilities. .The soil borings were advanced to a depth of about 25 feet at the following locations: • One boring(B-6)to resam.pie at the B-2 location. • One boring(B-7)approximately 30,feet northwest of the B-2 location. • One boring(B-5)north of the B-1 location. • One boring (B-8) south of the B-3 location. • One boring(B-9)east of the'B-4 location. Page 2 of 9