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1 � • Limited Soil and Groundwater Report-05/24/99 Page 12 Western Oil&S readin Site Project No 024 98 110.0 CONCLUSIONS 1 Based on the accumulated site history data, the current htmted sod/groundwater investigation, and results Gallardo&Associates concludes the following • Soil sampling lin results collected from the five exploratory soil borings (B-1 through B-5) indicate that the soil located beneath the property at sod boring locations B-1, B-2, and 1 B-4 has been impacted by moderate concentrations of TPH-g, TPH-d, and TPH-k. • The Vertical extent of the impacted soil appears to end at approximately 34 %2 feet bgs at 1 boring B-2, and approximately 29 %feet bgs at boring B-4. However, vertical definition was not defined at boring B-1. The impacted sod extended below the 40 foot maximum ' depth of the investigation as defined in the approved workplan. • The horizontal went of the impacted sod appears to be restricted to the area surrounding the 20,000-gallon UST's No impacted soil was detected beneath sod boring B-5 located within the former diesel and gasoline UST's cavity. ' • The highest concentrations of impacted soil appear to be centered beneath borings B-1 (TPH-d at 3 0,000 ppm and TPH-k at 18,000 ppm) and B-2 (TPH-d at 13,000 ppm and TPH-k at 11,000 ppm) at an approximate depth of 29 %feet bgs. In addition, analytical results collected from sod boring B-4 indicate that concentrations of TPH-d at 1,800 ppm and TPH-k at 1,700 ppm exists at an approximate depth of 14 %feet bgs. • The depth to the true water table was not encountered during this investigation; however, a shallow perched water zone was detected at an approximate depth of 29 %feet bgs. ' • The shallow groundwater (perched) detected at soil boring B-4 has been impacted by concentrations TPH-d, TPH-k, TPH-g, and BTEX However, this shallow groundwater body was only detected in soil boring B-4. The extent of impact to this possibly perched ' groundwater could not be determined during this limited investigation. • The direction of groundwater flow could not be determined during this investigation. ' 410 RECOMMENDATIONS ' Based on the data presented, Gallardo &Associates supports the followmg recommendations ' • Since the surrounding groundwater has already been impacted by saline water emanating from the adjacent Hictor Sausage site currently under investigation by the Central Valley Regional Water Quality Control Board(CVRWQCB), and the fact that the impacted soil ' detected beneath the Western Oil& Spreading site property consists mainly of blebs of semi-viscous asphalt that are probably not likely to leach down into the deeper agroundwater zone suspected to be at a depth below 40 feet bgs, Gallardo c& Associates ' requests that San Joaquin County Environmental Health Division consider granting site closure.