SITE INFORMATION AND CORRESPONDENCE

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Dolly Madi3on/Langendorf Rakery - 2 - 18 June 2008 1426 S. Lincoln St., Stocker PIER Addendum The PIER,4ddend includes the fieldwork and analytical results for repaired vapor extraction well VW-1 (now used as a monitoring well due to a rising water table) and a new monitoring well MW-3 (enclosed Figure 2), which was located in S. Lincoln St. The PIER Addend states soil vapor wells SGW-1 and SGW-2 were also installed and sampled, and all wells (old and new) were professionally surveyed to a common datum. The PIER Addend updates the PIER Hydrogeology section by adding site specific groundwater flow directions and gradients to the PIER evaluation of the hydrogeology at neighboring USTs sites. The PIER Addend also includes site specific groundwater elevation contour maps of the shallow, mini, and deep water bearing zones. Site geology consists of"...interfingered beds of permeable sands and gravels mixed with lesser permeable silts and low permeable clays..." (enclosed cross sectic,n Figure 4), which does not appear to retard contaminant transport from the shallow to the deeper aqu fer zones. In fact, while an argument has been proposed that groundwater pollution is the result of an off-site petroleum hydrocarbon source, the PIER Addend demonstrates that there is also evidence for a USTs release at the Site, which is several orders of magnitude greater in concentrations than any pctential offsite source. The PIER Addend concludes that petroleum hydrocarbons were not detected in soil samples collected for installation of MW-3. However, on 26 March 2008 (first quarter 2008) methyl tert-butyl ether (MTBE, 38 micrograms per Liter or ug/L) was detected in groundwater sampled from MW-3. By email received on 4 June 2008, Stratus informed me that the analytical results for the second quarter 2008 groundwater monitoring event reported MW-3 as non-detect for MTBE at a detection limit of 0.5 ug/L. The PIER Addend als:) stated that all soil gas sampling results did not exceed the San Francisco Bay Regional Board Environmental Screening Levels. Pilot Test/FS The Pilot Test section of the Pilot Test/FS provides the results of air sparging and soil vapor extraction (AS/SVE) tests conducted on 11/12 March 2008 using portable test equipment and remediation wells VW-2, VW-3, and AS-1. The effective radii of influence (ROI) for the SVE wells (VW-2 and VW-3) were calculated at approximately 15 feet. Dissolved oxygen content in groundwater also increased from 0.12 milligrams per Liter (mg/L) up to 4.0 mg/L during the AS portion of the test. Petroleum hydrocarbons detected by Photo-ionization Detector in the SVE air stream increased from 2 parts per million by volume (ppmv) at startup to 390 ppmv just prior to the end of the test. Total petroleum hydrocarbons as gasoline (TPHg) laboratory analytical results increased in extracted soil vapor from 640 milligrams per cubic centimeter (mg/m3) at startup of the SVE system to 3,200 mg/m3 approximately 30 minutes before the end of the test. Based on these results, Stratus calculated that TPHg removal would be approximately 2.5 pounds per day (ppd) from soil vapor extraction well VW-2 alone, and 14.5 ppd of TPHg from soil vapor extraction well VW-2 when combined with injecting air into air sparge well AS-1. Extracting soil vapor from VW-3 alone reported 96 ppd of TPHg removal, while combined use of VW-3 and AS-1 showed 17 ppd. Using just VW-2 and VW-3 resulted in removal of 24.5 ppd of TPHg; while use of all of the remediation wells, VW-2, VW-3, and AS-1, resulted in a calculated removal rate of 28.E ppd of TPHg.