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Mr. Joe Aldridge - 2 - 2 August 2006 <br /> (TAME), ethyl tertiary butyl ether (ETRE), diisopropyl alcohol (DIPE), and tertiary butyl alcohol <br /> (TBA) using EPA Method 826013; and Total Petroleum Hydrocarbons (TPH) as gasoline and <br /> diesel by the DHS LUFT Method. To evaluate natural attenuation conditions, the samples will <br /> be analyzed for methane by Method RSK-175M; alkalinity by EPA Method 310.0; total organic <br /> carbon by EPA Method SW9060/ 415.1; ammonia by EPA Method 350.3; orthophosphate by <br /> EPA Method 365.2; nitrate, nitrite, and sulfate by EPA Method 300.0; and iron and potassium <br /> by EPA Method 200.7. <br /> Installation of the proposed B-zone monitoring wells will occur in a separate work phase with <br /> procedures based on whether heaving sands are present or contaminant concentrations in the <br /> A-zone wells exceed 1 milligram per liter TPH gasoline or diesel or 100 micrograms per liter for <br /> individual BTEX or fuel oxygenate compounds as described above. The borings will be <br /> straight drilled to the bottom of the A-zone wells and continuously soil sampled below that <br /> depth. The wells are anticipated for completion between 40 and 55 feet bgs depending on <br /> subsurface Iithology. Well construction will be similar to the proposed A-zone wells although <br /> the well screens will not be placed across the water table. The wells will be developed, land <br /> surveyed, and sampled following installation. The suite of chemical analyses will be the same <br /> as for the A—zone well samples. <br /> A written report of findings will be prepared summarizing the investigation results. The wells <br /> will subsequently be incorporated into the existing quarterly reporting program. Testing for <br /> natural attenuation parameters will occur for four quarters at which time continuation of the <br /> testing program will be evaluated. <br /> Regional Water Board staff concurs with the activities proposed in the Work Plan. It should be <br /> noted that the laboratory detection limit given for MTBE of 0.005 milligrams per liter using EPA <br /> Method 8260B should be 0.0005 milligrams per liter corresponding to the detection limit <br /> utilized for previous analyses. According to the schedule provided in the Work Plan, <br /> coordination of the fieldwork can begin upon receipt of Regional Water Board approval. The <br /> well installations should be completed with two months and the report of findings submitted <br /> within two months of completion of the field activities. Based on this schedule, the report for <br /> the proposed scope of work is due to this office by 30 November 2006. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4719 or <br /> mclardy(@waterboards.ca.gov. <br /> Mark W. Clardy, P.G. <br /> Engineering Geologist <br /> Private Sites Cleanup Unit <br /> cc: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton <br /> Ms. Rita Koehnen, Port of Stockton, Stockton <br /> Mr. Jerry Stauffer, Valero, L.P., San Antonio, TX <br /> Ms. Amanda Spencer, Ash Creek Associates, Inc., Portland, OR <br /> MWC/W:\slic—dodWustinSlaf\Mark\Valero Stocktonl4-14-06Valero GW WP.doc <br />