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• Well Installation and Soil Boring Report-Tosco(former Unocal) Service Station#6981,Stockton, CA November 15, 1999 ncountered to the boring down to 56 feet bgs, beyond the field evidence of hydrocarbon Impact was ethewas approximate historic groundwater low collected every 5 feet asia m mmuma in in h of advanced er,at the directon of Ms he borings GR to 71 feet bgs Soil samples were geologist prepared logs of all borings and collected soil samples for possible analysis soil from each sampled interval was screened in the field for the presence of volatile organic compounds Screening data are presented on the boring logs(App endix B)Upon completion,borings MW-14,MW-15,and VW-8(subsequently renamed MW-16)were completed as groundwater monitoring wells Boring VW-9 was backfilled to ground surface with neat cement containing approximately 5%bentonite powder Boring VW-7 was backfilled with neat cement to approximately 55 feet bgs After curing overnight,the boring was completed as a air sparging well Drill cuttings were placed on and covered with plastic sheeting and stored at the site pending disposal After completion of drilling,four samples for disposal characterization were collected from the drill cuttings and submitted to the laboratory for compositing and analysis Well Construction Groundwater monitoring wells were constructed in borings MW 14,MLones and MW 16 using 20 feet of 2-inch diameter,0 020-inch machine-slotted,Schedule 40 PVC screen Lonestaz#3 graded sand was placed • in each well across the entire screen interval and extended approximately 2 feet above the top of the screen Each well was then sealed with 2 feet of hydrated bentonite chips followed by neat cement grout Well construction details are presented on the boring logs in Appendix Sparge well VW-7 was constructed using 5 feet of 2-inch diameter,0 02-inch machine-slotted,Schedule 40 PVC screen Lonestar #3 raded was ire screen interval a extended approximately 3 feet above the op oft e c placed e reen The ll was then escaled with 2 feet of bentonite followed by neat cement Well Development and Sampling Groundwater monitoring wells MW-14, MW-15, and MW-16, along with sparging well VW-7, were developed and sampled on August 21, 1999 Prior to development GR measured depth to water in each of the wells Development was conducted using a vented surge block and hand bailing Groundwater samples were collected upon completion of well development Purged water was stored at the site in properly labeled drums pending disposal data mincluded i C able 2 Copies of GR's Well Development and Sampling Field Data Sheets are in Wellhead Survey Following installation of the wells to elevations ofthe wellheads were surveyed relative to Mean Sea Level byMorrow veyed copy of to uCalifornirvlicensed land surveyor(95161)eyor's report is included in Appendix D Horizontal Wellhead elevation inates of the wells ata are also surveyed A copy • summarized in Table 2 3 140124 05