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CytoC"Imre International Inc. 249 Tewksbury Avenue, Pt Richmond, CA 94801 Lab 510-233-0102 Email lab@cytoculture com Brian Pierskalla Clearwater Group 229 Tewksbury Avenue Point Richmond, CA 94801 October 8, 2003 Assessment of Intrinsic Bioremediation Site Conditions at Barnes Trucking Facility 1817 S Fresno Avenue, Stockton, CA Clearwater Project 2B 178C P O No 00008894 Site Conditions The Barnes trucking facility site appears to have residual diesel fuel contamination in the vicinity of the former USTs(removed in 1992)that continues to leach petroleum hydrocarbons down-gradient The steady source of dissolved phase petroleum hydrocarbons is kept in check by the growth of bacteria along the peripheral boundaries of the plume In general, however, the TPH and BTEX concentrations have remained relatively stable within the confines of the plume as indicated from quarterly analytical data collected since the year 2000 Hence, the intrinsic bioremediation and other natural attenuation mechanisms appear to be keeping up with the source of hydrocarbons but the plume is not yet receding appreciably Nutrient Levels Concentrations of ammonia nitrogen(0 6 to 2 4 mg1L) and o-phosphate(0 1 to 2 8 mg/L) are relatively low in most of the wells and they are declining rapidly in monitoring wells MW-1, MW4 and MW-5B where hydrocarbon concentrations Tremain significant The nutrient depletion indicates biological activity (rates of metabolism) are now fast enough in these area that the utilization of these nutrients by bacteria may be overcoming the steady state recycling of the nitrogen and phosphorus within the biomass In other words, as air sparging and other site condition changes occur, the biological activity may contribute to the utilization or degradation of the available nutrients The pH of the groundwater was not measured Oxygen Levels Dissolved oxygen levels have vaned considerably from year to year, and from quarter to quarter, but in general they consistently indicate the groundwater is fairly aerobic DO concentrations measured in the laboratory do not always match those collected in the field, lab measurements consistently indicated DO concentrations in the range of 3 6 to 5 9 mg/L, where as field measurements (even for the same monitoring wells) ranged from 19 to 8 7 mg/L Field measurements should be lower(less atmospheric oxygen introduced)than lab measurements in general