ARCHIVED REPORTS_XR0008769 - Laserfiche WebLink

Home Browse Search

Page 7 January 30, 1992 Job No 400511-SA intervals, soil samples from the shallow zones with no hydrocarbon odor were sent to the analytical lab on a two-day turnaround time basis The lab results showed that total petroleum hydrocarbons as gasoline were not detectable The new vapor extraction wells have been plumbed so that they can be ' incorporated into the existing vapor extraction system These wells were finished with traffic rated vault boxes set in concrete pads Extraction from the fourteen newly installed vapor wells began on December 6, 1991 ' 5.0 RESULTS AND DISCUSSION This section describes the results of the field investigation, including a description of the geology, ' hydrogeology, and extent of hydrocarbons at the site 5.1 Site Geology The site is underlain by interbedded silty clay, fine-grained sandy silt, poorly graded fine to coarse- gramed sand, and gravel The soil color varies between dark brown, brown, light brown, and gray- brown The soil densities are generally very dense or hard The subsurface geologic materials are reported in the soil boring logs, which are contained in Appendix B Geologic cross sections were prepared from the soil boring logs The cross section locations are shown in Figure 2, and the cross sections are presented in Figures 3 and 4 They illustrate the interbedded nature of the soils underlying the site Permeable sand occurs between 40 and 65 feet below grade and from approximately 81 feet below grade to the depth explored The soils underlying the site are likely Holocene and Pleistocene Age stream channel, lake, and flood plain sediments ' Stream drainage in the area of the site is generally from the east to the west toward the Delta area ' 5.2 Site Hydrogeology ' In the area of the site, groundwater recharge is from local infiltration of rainwater precipitation Free flowing groundwater was encountered beneath the site at a depth of approximately 815 feet during drilling of the monitoring wells Subsequent depth to water measurements in the newly installed wells showed the water level to range from about 81 feet to 82 feet below grade Depth to water measurements and the calculated groundwater elevations for all the wells are listed in Table B ' aoosnn f Rev 1 Du Pant Environmental Remediation Services Pnnted on Recycled Paper