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i <br /> April 1999 Advanced Geo Environmental Inc (AGE) advanced 4 Geoprobe soil borings at the <br /> • site to collect soil and grab ground water samples, then perform a mass balance <br />' calculation of remaining petroleum hydrocarbons in the subsurface and prepare a <br /> Closure Summary Report B-1 was advanced to 50 feet,the remainder were advanced <br /> to 25 feet <br /> May 1999 SEMCO did not pay AGE money for work done, so AGE stopped all work on <br /> Langston Project <br /> IAug 1999 EHD wants additional well on property <br />' Apn12000 AGE submitted an Additional Site Assessment Report indicated that ground water <br /> contamination was detected in four soil borings (B-1 to B-4) from April 1999 and <br /> that further investigation was warranted, TPH-g, BTEX, and MTBE were detected <br />' in grab water samples from on- and off-site push points <br /> May 2000 EHD issued a letter informing the Langstons that additional work needed to be done <br />' to define vertical and lateral extent of the MTBE plume A sensitive receptor survey <br /> was also required AGE resumed active monitoring of the site <br />' June 2000 EHD approved AGE's Monitoring Well Installation Work Plan dated 23 June 2000 <br /> Sept 2000 AGE installed four additional monitoring wells to 30 feet bsg(MW-5 to 35 feet bsg) <br />'• at the site(MW-5 to 8) In December 2000 four additional monitoring wells (MW-5 <br /> to MW-8) were installed by AGE Since AGE began quarterly ground water <br />' monitoring at the site in March 1999, the inferred ground water gradient has <br /> consistently been toward the northwest <br />' Dec 2000 First monitoring event that includes the new wells Results of the monitoring event <br /> detected high concentrations of TPH-g and MTBE in sample MW-5 (from the <br /> original UST area) and above-California's MCL for benzene Ground water flow <br />' direction for the last four monitoring events is towards the northwest, AGE has no <br /> ground water monitoring wells down-gradient of MW-5 <br /> I <br />' 2001 May 24 EHD approved AGE's Work Plan Addendum dated 16 May 2001 for additional soil <br /> borings northwest and east and vertical at UST area to define vertical and lateral <br /> extent of contaminated ground water <br />' soil borings B5 B6 and B9 for collection of soil and ground <br /> Nov 2001 AGE advanced three b g { ) <br /> water samples No analytes of concern were detected in the analyzed soil samples <br /> collected from the three borings However, high concentrations petroleum <br /> hydrocarbons were detected in the ground water sample collected from boring B9, <br />' located east of the former UST location,target analytes were not detected in ground <br /> water samples collected from borings B5 and B6,located at the former UST location <br /> and northwest of the former UST location, respectively <br /> 1 <br />