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• QUARTERLY GROUNDWATER MONITORING REPORT MAY 1993 Bank of America/Security Pacific Property 300 S. state Street Ukiah, California 1. 0 INTRODUCTION In accordance with a request from Bank of America, personnel from Geological Audit Services, Inc. (GeoAudit) have performed quarterly groundwater monitoring procedures at 300 South State Street in Ukiah, California (the site) . The project background, procedures, findings and conclusions are presented in the following sections. The site location is presented in Figure 1. A plan of the site is presented in Figure 2 . 2 .0 BACKGROUND 2 .1 Site Assessment The site is located in a relatively flat commercial area of Ukiah (Figure 1) . Three 10, 000 gallon underground gasoline tanks were removed from the subject site in 1986. Hydrocarbon contamination in the soil and groundwater was discovered following the tank removal. Subsequent assessment activities included the installation of five on-site and four off-site groundwater monitoring wells (Figure 2) . A passive monitoring program was performed between the second quarter of 1990 and the first quarter of 1991. During the monitoring program, contamination levels showed considerable fluctuation. 2.2 Remediation Between August 1991 and August 1992 , active mitigation of soil contamination was performed. Soil in the vadose zone and capillary fringe was removed and bioremediated in an on-site remediation cell. A work plan and subsequent addendum for these activities were submitted to the Regional Water Quality Control Board - North Coast Region (RWQCB-NCR) on 31 May and 16 July 1991, respectively, and found adequate. To comply with current air quality regulations, a permit to bioremediate the contaminated soil was also secured from the Mendocino County - Air Pollution Control District (Permit No. A/C91-20) . Following completion of the bioremediation project, a report was submitted on 21 July 1992 to the RWQCB-NCR. 1