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City of Stockton A68109.01B July 18, 1997 Page 9 The site specific parameters used in the leaching potential analysis are outlined as follows. 1 ' • Groundwater depth - 48 feet BSG E � 0 Subsurface fractures - none observed • Average annual precipitation - 10 to 25 inches 0 Man-made conduits - none observed jE • Unique site features - none observed 1, Soil sampling locations which sample analytical results indicated PPCs were selected for the leaching potential analyses. Copies of these analyses are presented in Appendix E. The 1 leaching potential analysis indicate that the soil beneath the former UST location does not pose a potential threat to groundwater quality. It has been our experience that concentrations of toluene and TPH-D as detected in the groundwater sample collected from soil probe location SP-1 generally do not warrant remedial action. :3 7.0 CONCLUSIONS • TPH-D was detected at concentrations of 310 mg/kg in a soil sample collected at 12 feet BSG beneath the former UST. Toluene, ethylbenzene, xylenes, and TPH-D were detected at a concentrations slightly above their respective detection limits in a soil sample collected at 16 feet BSG adjacent to the west side of the former UST; • Toluene and TPH-D were detected at small concentrations 0.7 and 410 L, { µg/ �I respectively) in a groundwater sample collected from beneath the former UST location. Soil and groundwater data does not suggest that free product is present on the groundwater surface; i Based on the results of a leaching potential analysis performed consistent with the LUFT Field Manual further investigation and/or remedial action for soil and groundwater does not appear to be warranted at this time.