WORK PLANS FILE 2 - Laserfiche WebLink

Home Browse Search

BACKGROUND SUMMARY The underground fuel tanks and associated fueling facilities for this Tracy site were removed in early 1990 along with the soil from the tank pit. Multiple investigative events were subsequently performed as it was clear a fuel release had occurred. These investigations covered both parts of the subject site (i.e., the front/south commercial part and the back/north mobile home park part) as well as the adjoining portions of the school property to the north (downgradient) and the Heinz property to the east. A northward trending area of soil and groundwater impact was defined, primarily lying between two large, N-S oriented buried pipelines, a 48-inch diameter irrigation water pipe and a 36-inch diameter sanitary sewer pipe. A network of nine groundwater monitoring wells was installed over time with regular testing events that continue today. In 2004 an extensive remediation program was undertaken involving the removal of approximately 900 cubic yards of the most heavily impacted accessible soil (see stippled areas between pipelines and north of original UST pit on Figures A and B), plus nearly 240,000 gallons of contaminated groundwater. Numerous physical constraints made additional excavating essentially impossible. Replacement monitoring wells in the core impact area have demonstrated a significant improvement in groundwater quality and the fuel leak case is now recognized as a justifiable candidate for no further action, subject to the outcome of the subject vapor study. PLANNED WORK The work tasks Wright currently plans for the subject soil vapor sampling program are as follows: 1. Mark the five planned sampling locations (see Figure B) after scanning the spots for live underground utilities with a private locator as warranted. We will also mark the street curb and/or sidewalk for Underground Service Alert and call them as required for all subsurface activities. Note that although sampling points SBS, SB8 and SB9 across the very north portion of the Site apparently exhibited elevated benzene in 1993, these findings have not been confirmed in subsequent exploration (PB-7 and MW-5) nor by subsequent groundwater monitoring (MW-1, MW-2 and MW-5). Accordingly, this strip is not considered a justified target area for the subject soil vapor study. 2. Advance the five planned sampling holes to a depth of five feet using pre-cleaned hand- auger equipment. It is envisioned that the resulting hole will be 2-3 inches in diameter and have side-walls that will not cave/slough. Representative soil will be retained from two of the holes in order to conduct physical property testing (see Task 6). Soil conditions at every hole will be logged by a Professional Geologist. Page 2 of 4