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Lodi City Landfill November 16,2011 North of Awani Drive,Lodi,California Project No. 104690061 Their investigation included installation of four, 1/2-inch diameter steel pipe/probes (referred to as 'pipe wells')to depths of 9 feet,the bottom 2 feet were perforated every inch for air sampling,purg- ing the wells and collecting tedlar bag samples. They "field tested"the 'Pipe wells"and submitted the sample with the highest concentration for laboratory analysis of nitrogen, oxygen, carbon diox- ide, methane, halogenated hydrocarbons, vinyl chloride, and benzene. They also advanced 24 "barhole"sample locations(B-1 to B-24)to depths of approximately 4 feet bgs,at approximately 50-foot intervals around the site perimeter and conducted field monitoring for the potential presence of methane gas(the "barhole"sampling method was not described in detail in the report). Field monitoring of the four `pipe wells"(IA, 2B, 3C, and 4D) indicated methane at concentra- tions of 350 to 400 parts per million (ppm). The air sample collected from `pipe well" 4D contained 81% nitrogen, 1.26% oxygen, 2.14% methane, and 15.4% carbon dioxide. Benzene, vinyl chloride, and halogenated hydrocarbons were not detected at concentrations above their respective laboratory detection limits at that time. Field monitoring of methane gas concentra- tions from the 24 "barholes" indicated concentrations ranging from below the detection limit to 350 ppm. "Barhole"B-3 indicated an OR(out of range)concentration of methane. The report stated that methane production is occurring at the site and the test wells indicated the highest concentrations of methane are located in the northern portion of the site. It was stated that based on the "barhole"testing,it appeared surface migration is minimal. Mandeville & Associates indicated the evaluation of the site was based on several assumptions including "l) Based on the river elevation, the depth of the fill was estimated to be between 20 and 30 feet. 2) Based on the total of eleven pits excavated by "The Foundation Engineers Inc." and VH. Kleinfelder," there are no locations of highly concentrated organic materials. 3) Dur- ing the period the landfill was in operation, the preferred method for disposal of a large portion of organics was on site burning, and 4) Sketchy history of the site indicated the majority of the of disposed wastes would be materials such as tree limbs and stumps which decompose slowly and construction debris such as concrete, etc., which are non-gas producing." In October 1988,Kleinfelder prepared a report titled "City of Lodi Preliminary Site Assessment, Lodi California."The purpose of the site assessment was to assess whether the site was eligible for exemption from the SWAT program based on whether the landfill was leaking hazardous was or was likely to be "leaking hazardous waste." The report provided an executive summary that stated the landfill received wastes composed of lawn trimmings, leaves, tree stumps, and con- struction debris(concrete,asphalt,metallic slag, and rock) from approximately 1935 to 1955. Their investigation consisted of advancing four soil borings to a maximum depth of 29 feet bgs and converting one boring to a groundwater monitoring well. Samples of wastes, vadose zone soils, groundwater, and surface water samples from the Mokelumne River were collected for laboratory analysis. 104690061 R 8nAdm 7