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T & T Trucking Page 2 <br /> 11396 Hwy 99 Frontage N, Lodi <br /> f <br /> n <br /> (2) Vertical and lateral impacted soil and groundwater delineation; <br /> Previous soil and groundwater investigative phases have not completely <br /> characterized the hydrogeological system of the site or delineated impacted soil <br /> or groundwater in'all directions. A better understanding of the preferential <br /> pathways that facilitate contaminant migration is needed. EHD recommends that <br /> Cone Penetrometer Testing (CPT) tool 30' bgs be conducted for this purpose.. <br /> Conclusions for vertical soil delineation should be supported by consecutive, f <br /> four-to five-foot vertically spaced samples that are non-detect for fuel <br /> constituents at acceptable detection limits. Groundwater samples that exceed <br /> allowable limits for contamination to remain in. place represent areas of the <br /> subsurface that are not vertically defined. Additionally, deeper-screened <br /> monitoring wells may need to be installed after the exploratory soil borings have <br /> characterized the deeper hydrological units. Soil and groundwater samples <br /> should be analyzed for TPHg by EPk Method 8015m, BTEX by EPA Method <br /> 8020, and 1,2-DCA, EDB, MtBE, and the LUFT Oxygenates by EPA Method <br /> 8260. Some laboratories are certified to analyze for all of these constituents by <br /> EPA Method 8260B. This is acceptable to EHD also. The results of the <br /> investigation should be reported in the context of a site conceptual model within <br /> 60 days of receiving the laboratory results. <br /> (3) EHD concerns regarding the `supply well'and the `unused'drinking water well <br /> at the site; <br /> Currently two domestic wells are present at this site. One is identified in reports <br /> as "unused" and the other as "supplywell". The wells are located approximately <br /> 120 feet and 180 feet down gradient of the suspected release point. The unused <br /> well is suspected to bottom at 150 feet below.ground surface (' bgs), but has <br /> been filling with sediment; the supply well is screened from 167' bgs to 247' tags. <br /> Groundwater samples from the `supply well' were recently analyzed and <br /> petroleum (TPHg, BTEX, and MtBE) constituents were not detected. Although <br /> there is no immediate danger of drinking contaminated groundwater, this well is <br /> still considered "threatened" and the elevated levels of MtBE in close.proximity to <br /> the well places this site in a high priority status that is constantly monitored by the <br /> State Water Resources Control Board (SWRCB) and is required to enter <br /> remediation within one year. Immediate steps must be taken to remain in <br /> compliance. The first step, already initiated, is quarterly sampling of the <br /> domestic wells (`unused' and `supply')to detect encroachment of impacted r <br /> groundwater. Consistent water sampling and testing of water from this well k <br /> should be conducted until the threat to your drinking water has been mitigated. <br /> In the event that petroleum contaminants are detected in the well before the site <br /> enters remediation, you should immediately stop drinking the water and secure <br /> 'bottled' water as your first action. As a slightly more efficient method, you could <br /> consider a manufactured wellhead treatment system until a more permanent <br /> solution is arranged. <br /> t <br />