ARCHIVED REPORTS_XR0012194 - Laserfiche WebLink

Home Browse Search

former Unocal Service Station#6981, Stockton, CA Well Installation and Soil Boring Report-Tosco { } November 15, 1999 field evidence of hydrocarbon impact was encountered in the boring down to 56 feet bgs, beyond the approximate historic groundwater low However,at the direction of Ms Lagorio,the boring was advanced to 71 feet bgs Soil samples were collected every 5 feet, as a minimum, in each of the borings A GR 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(Appendix 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,MW-15, and MW-16 using 20 feet of 2-inch diameter,0 020-inch machine-slotted,Schedule 40 PVC screen Lonestar#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 to Appendix B Sparge well VW-7 was constructed.using 5 feet of 2-inch diameter,0 02-inch machine-slotted,Schedule 40 PVC screen Lonestar #3 graded sand was placed across the entire screen interval and extended approximately 3 feet above the top of the screen The well was then sealed with 2 feet of bentonite followed by neat cement E 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 1� were collected upon completion of well development Purged water was stored at the site in properly labeled drums pending disposal Groundwater monitoring data are included in Table 2 Copies of GR's Well Development and Sampling Field Data Sheets are included in Appendix C Wellhead Survey Following installation of the wells the elevations of the wellheads were surveyed relative to Mean Sea Level by Morrow Surveying,a California licensed land surveyor(#5161) Horizontal coordinates of the wells were also surveyed A copy of the surveyor's report is included in Appendix D Wellhead elevation data are summarized in Table 2 140124 05 3