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CASE CLOSURE SUMMARY <br />Former Santa Ana City Yard, Santa Ana <br />UST No. 083000117 <br />V. ADDITIONAL UUMMtNIs,uAI <br />October 8, 1999 <br />Page 6 <br />The site operated as the City of Santa Ana's maintenance yard facility. The site included a paint pit area (used from <br />1973 — 1985), paint processing or mixing area (1973- 1985), nine USTs, and two clarifiers (used for clearing water <br />generated during equipment cleaning operations). <br />Investigations included: <br />• Observation well, OW -1 (or B -5) was installed in September 1995. <br />• The drilling of five borings (B -1 through B -5) and the installation of one piezometer (LA -1) in 1988 and January 1989, <br />respectively. <br />• In 1995, the installation of 40 geoprobe soil borings (G1 through G -40), four geoprobe groundwater samples (HP -1, <br />HP -2, HP -3, and HP -5), and two monitoring wells (MW -1 and MW -2). <br />• In 1997, the installation of wells MW -3 through MW -8. <br />In 1998, deeper borings 1 LA520 and 2LA50 were drilled near the undocumented well down to — 50 feet bgs). Also, <br />three geoprobes (GC1 through GC3) were drilled and sampled. <br />This site is considered a low -risk site based on the completion of the following items: <br />USTs /piping and other potential sources (paint area, clarifiers, etc.) were removed and the contaminated soil was <br />excavated and removed. Approximately 4,862 tons of contaminated soil excavated and removed from the site. <br />Soil and groundwater contamination plumes were fully defined. r <br />Several quarters of groundwater monitoring were completed for this site. The latest groundwater results revealed all <br />ND results except for The remaining levels of groundwater contamination slightly exceed the maximum contaminant <br />level (MCLs) or Action Levels (ALs) established for these compounds. Therefore, these remaining groundwater <br />contamination levels should not pose a threat to groundwater quality in this area. <br />A human health risk assessment (vapor risk) was conducted. The report was reviewed and approved by an <br />independent expert. The report concluded that the "excess lifetime cancer risk posed by residual gasoline <br />contamination was significantly below the risk level of 1 in one million excess lifetime cancer cases" (see attached <br />VI. LOCAL AGENCY /RWQCB REPRESENTATIVE DATA <br />RWQCB SIGNATURE: <br />TITLE: /Gv <br />DATE: , 70 <br />sanyarddo.rtf <br />