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I Manteca Bean Facility, 229 Moffat Boulevard, Manteca, California February 9, 1993 Golden Grain Company I Page 3 state certified laboratory Laboratory analysis reports and corresponding chain-of-custody manifests for sampling events from September 14 through December 3, 1992, are included in Attachment 2 Results of system historical analyses are summarized in Table 3 During this quarter of system operation analyses of discharge water indicated that the TPH-as-gasoline, BTEX, and total lead concentrations have been below permit limitations Results of analysis for TPH-as-gasoline and BTEX have been non-detectable for each of the system effluent sampling events except the September 28, 1992 samples The results from this sampling indicated trace amounts of hydrocarbons in the system effluent water, below permit limdations Following review of the September 28 sampling results, the air stripper was cleaned during the next weekly regular scheduled maintenance visit These trace concentrations were probably caused by decreased air stripper efficiency from internal calcium buildup As indicated in the Treatment System Operations Summary, a air stepper was cleaned on October 1, 1992, and the next sampling event (10/5/92 - Table 3) of system effluent water was non-detectable for TPH-as-gasoline and BTEX During system operations for this quarter, 167 pounds of TPH-as-gasoline have been removed from groundwater pumped from beneath the site The vapor extraction system was monitored each week during this reporting period The influent and effluent vapor concentrations were measured for TPH-as-gasoline using a flame ionization detector (FID) In addition, air velocity readings were taken at the influent wells in order to calculate the mass of hydrocarbons removed from the soil Values measured during site visas are shown in Table 4 The average destruction efficiency calculated from weekly FID readings of the catalytic oxidizer effluent vapor stream is 98 2% This average efficiency is for the operational period of the treatment system, October 11 through December 29, 1992 Assuming an average vapor-extraction system flow of 2128 cfm, we can calculate the estimated amount of TPH-as-gasoline removed from soils at the site This average velocity is based on our knowledge of the system over its life and past data collected during operation Based on the values obtained and the average observed flow, It is calculated that approximately 616 27 pounds of TPH- as-gasoline were removed from the soil by the vapor extraction system during the quarter The cumulative amount of hydrocarbons removed by the VES since start-up Is calculated at 769 87 pounds ❑ GROUNDWATER inassay oa�s< TECHNOLOGY,INC