WORK PLANS FILE 1 - Laserfiche WebLink

Home Browse Search

Site Background Information: West Clay Properties Page 3 of 10 October 1999-AGE advanced one soil boring(B-9)for collection of soil and ground water samples. Significant concentrations of petroleum hydrocarbons were detected in samples collected from the boring.Based on the findings from boring B-9,monitoring wells MW-9 and MW-10 were installed near the former UST excavation area. July 2000 - Nine pilot borings were advanced at the site for installation of monitoring wells MW-11AB through MW-13AB,air-sparging well AS-1 and ground water extraction wells EW-1 and EW-2.Petroleum hydrocarbons were detected in soil samples collected from pilot borings EW-1 and MW-13B. November 2002 - Four pilot borings were advanced at the site for installation of monitoring wells MW-14AB and MW-15AB. Target analytes were not detected above laboratory reporting limits in the soil samples submitted for analyses. December 2003 - Approximately 340 cubic yards of petroleum hydrocarbon-impacted soil was excavated from the former UST location. Soil was disposed of at Forward Landfill in Manteca, California. Based on the low to non-detect concentrations of petroleum hydrocarbons in the soil samples collected from the sidewalls and floor of the excavation, it appears that the major portion of the most significantly impacted soil was removed during over-excavation. Ground Water Monitoring- Based on analytical results of ground water samples collected during quarterly monitoring and site assessment activities, the most impacted ground water appears to be centered around EW-1 and MW-10. The vertical extent of the contamination plume, as well as the lateral extent east and south of the former UST cluster, is not well defined. ON-SITE CPT INVESTIGATION Between 0l and 04 June 2004,four CPT soil borings(CPT-01 through CPT-04)and 11 individually established soil borings for collection of ground water samples were advanced at the southern UST No. 3 location and the northern UST cluster area. CPT soil borings were advanced at the following locations - ground water samples were collected from dedicated borings at the following intervals: • CPT-01, CPT-02 and associated ground water sampling borings were advanced near the northern boundary of the former UST No. 3 location (Figures 2 and 3) to determine the vertical extent of petroleum hydrocarbon-impacted groundwater.CPT-01 and CPT-02 were co-located borings. CPT-01 was advanced to approximately 100 feet bsg; CPT-02 was advanced to approximately 170 feet bsg- CPT-01 was sampled between 77 and 81 feet bsg and between 93.5 and 97.5 feet bsg while later CPT-02 was sampled between 114 and 118 feet bsg and between 137 and 141 feet bsg; • CPT-03 and associated ground water sampling borings were advanced south-southwest of Advanced GeoEnviron mental,Inc.