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1 <br /> 1 <br /> Langston 's Market <br />' 15615 Seventh Street, Lathrop, California <br /> Work Plan <br /> Phase II Lateral do Vertical Extent <br /> of Second Groundwater Aquifer, <br /> Revised <br /> I ' <br /> 1.0 Project Identification <br /> This project will involve lateral and vertical definition of the second aquifer with the installation of-hree <br /> (3) monitoring wells This work is associated with the former underground tank failure at Langston's <br /> IMarket, 15615 Seventh Street, Lathrop, California(Figure 1) <br /> 10 Site Description and History <br /> On June 7, 1990, Integrity Tank Testing Systems, Inc (ITTS) of Stockton, Caiifornia :;onducted <br /> a two part precision test using the Horner Ezy Chek H method The first test shawed a loss of <br /> 0 11 gallons per hour with a static pressure head of 3 4 psi at the tank bottom Th,- aec,)rd test <br /> ("cverclieck") showed a loss of 0 066 gallons per hour conducted at 3 0 pi at the tank bottom <br /> Based on the failed tank precision test, Mr Langston authorized ITTS to conduct a Helium Test <br /> on the tank That test was completed on June 14, 1990 The reason for the helium test was `o <br /> determine if a leak E-xistPd in the uppermost part of the tank system (e g the +a-.Lk openings or <br /> piping) <br /> On June 15, 1990, Mr Langston discovered approximately 1,200 gallons of unleaded gasoline <br /> was nussnng from the tank and unaccounted for Mr Langston could only conclude tliat <br /> potentially a mayor release had occurred Mr Langston treated the discovery of the missing <br /> gasoline as an emergency and immediately ordered the remaining gasoline pumped out of the tank <br /> and the environmental agency notified <br /> A preliminary environmental investigation of the property was completed by Murray & Associates <br /> at the request of Mr Langston in April 1992 This prelinunary investigation included the drilling <br /> Iof several exploratory soil borings by hand auger and rotary hammer in the vicinity of a failed <br /> 4,000 gallon underground gasoline tank (UST) <br /> The purpose of the preliminary investigation was to quickly and inexpensively evaluate the extent <br /> of soil contamination as a result of the UST failure and to determine the potential for groundwater <br /> contarrunation The investigation consisted of manually drilling eight 2-inch diameter soil borings <br /> to a depth of 17 feet Groundwater at the site is encountered at a depth of 17 5 to 18 feet The <br /> borings demonstrated that soil contamination in the viciruty of the former UST extended down to <br />