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THE SAN JOAQUIN COMPANY INc. 1 120 HOLLYWOOD AVENUE,SUITE 3, OAKLAND,CALIFORNIA 94602 San Joaquin County Environmental Health Department 600 E.Main Street �� Stockton, CA 95202 RP 2008 Date: March 31, 2008 ENVIRONMENT HEALTH Attn.: Mr. Nuel Henderson,PG PERMIT/SERVICES Our Reference: 9902.018 Your Reference: Site Code 1392 Subject: Navarra Property 7500 West Eleventh Street,Tracy, California Dear Mr. Henderson: This is a response to your letter dated February 15, 2008, addressed to our client, Mr. Carl Navarra, regarding the property at 7500 West Eleventh Street, Tracy, California. In your letter you requested that we address some safety and security issues presented by the proposed 15 ft. deep open trench, which was included as part of the Corrective Action Plan for Former Fueling Station, 7500 West Eleventh Street, Tracy, California (CAP) that was issued by the San Joaquin Company Inc. (SJC) in October 2007. You also requested an access agreement with the owner of 7501 West Eleventh Street. Safety and Security of Open Groundwater Extraction Trench SJC has extensive experience with extraction of light non-aqueous phase liquid (LNAPL) from trenches opened in the subsurface where groundwater is affected by high concentrations of fuel hydrocarbons. When LNAPL accumulates on the surface of groundwater in an extraction trench where the groundwater is affected by a mixture of gasoline and diesel, a layer of emulsified gasoline and diesel with suspended soil particles floats on the surface. The diesel is not flammable. The emulsified suspension has a significantly reduced flammability compared to that of raw gasoline. The emulsifying effect limits the emission of gasoline vapors at the air/water interface. However, a lower explosive limit (LEL) meter will be available on site to check the condition of the atmosphere in the trench. SJC has never experienced any ignition of LNAPL in an extraction trench despite the presence of operating heavy machinery. No LNAPL was present on the groundwater at the 7500 West Eleventh Street site when it was last measured on February 20, 2008. We also note that since December 2005, the maximum accumulation of LNAPL that has occurred over a six-month period has been 0.05 ft. Thus, if the LNAPL were to catch fire, the fire would be self-limiting because its fuel supply (i.e., the LNAPL floating on the surface of the groundwater) would be rapidly exhausted. The importance of adequate fire safety measures at sites involving subsurface accumulations of fuel hydrocarbons is addressed in SJC's Master Health and Safety Plan, a copy of which is on file with the SJCEHD and is incorporated by reference in the Project-specific Health and Safety Plan that is included as Appendix A of the CAP. TELEPHONE: OAKLAND,CALIFORNIA(51 0)336-9118 TRACY, CALIFORNIA(209)832-29 10