ARCHIVED REPORTS XR0009934 - Laserfiche WebLink

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t Extended Investigation of Groundwater Quality - 152 East 11th Street, Tracy Page 4 Well Construction The new wells were installed on June 17th and 18th 1993 They were designated as NAV 5, NAV 6, NAV 7 and NAV 8 Their locations are shown on Figure 2, which also shows the locations of all previously installed wells at the 152 and 153 East 11th Street properties Those installed for the Navarras are NAV 1 through NAV 8 and those installed for Ultramar Inc are ULT 1 through ULT 9 The general locations of new wells NAV 5 through NAV 8 were selected to explore the lateral limits of the area of the subsurface that has been affected by hydrocarbons and to improve understanding of the local hydrogeology Theu specific locations were dictated by the presence of underground utilities and surface and overhead obstructions that limited access by the drilling rig Dnlhng and well construction was performed by Soils Exploration Services, Inc (C57 Licence No 582696) working under the direction of a California-licensed geotechnical engineer Boreings for the wells were sunk with 8m diameter hollow stem augers Each boring was drilled to a total depth of 25 ft and continuously logged The soils encountered in each of the four boremgs and details of the well construction are recorded on the monitoring well logs presented in Appendix A For convenience of reference, this appendix includes available logs of other wells installed at the 152 and 153 East 11th Street properties On July 18th 1993 the depth to static groundwater in each of the newly installed wells was measured using a conductivity probe These depths are recorded on the monitoring well logs in Appendix A The wells were then developed by pumping a minimum 10 well volumes from each or until the a clear flow of water was obtained, whichever was greater The development water and the drill cuttings were retained in clean, 50 gallon, steel drums Cuttings and development water from each well were kept segregated in separate marked drums The closed drums were stored on the 152 East 15th property until the results of analyses of soil and water samples are available As is documented below, none of the soil or water from the new wells were affected by any detectable concentrations of hydrocarbon components Accordingly, after the analytical data became available, the water was decanted into the municipal sewer and the cuttings were disposed off site as clean soil Soil Sampling and Analysis During drilling for installation of the new wells, the drill cuttings were continuously checked for visual and olfactory indicators of contamination by hydrocarbons None were detected