ARCHIVED REPORTS XR0009746 - Laserfiche WebLink

Home Browse Search

' Bank of Stockton Page 6 BofS (Cuter) -Prehmtnary Soil and Groundwater Investigation Project No 102 2 April 8, 1997 1 3.0 FIELD & ANALYTIC DATA ' 3.1 Site Geology & Hydrology ' Regional Geology/Hydrology t The Central Valley is notable for the thick deposits described above which range in age from recent to Miocene and older and which may reach in excess of 20,000 feet thick In the Stockton area, the thickness of these sediments is about 5,000 to 7,000 feet The relatively ' unconsolidated, and transmissive deposits rest upon the granitic basement rocks of the Sierran batholithic complex and its associated metamorphic complex which is generally Permian to Jurassic in age ' The site is located on the gradually sloped floor of the San Joaquin Valley The geologic depositional environment of continental sedimentary deposits in this region is best ' characterized as alluvial and fluvial clastic deposits which have been derived from the gradual erosion of the Sierra Nevada Mountain Range located about 50 miles east of Stockton The USDA Soils Conservation Service Soil Survey of San Joaquin County California, October 1992, classifies the soil as Jacktone Clay The material is typically a very dark gray to dark gray clay, becoming calcareous at about 20 to 40 inches below the surface Permeability is fairly poor Deeper portions of the unit may grade to a yellowish loam Site Geology Observed ' The geology observed during the completion of the borings in the area can generally be characterized as medium to dark brownish gray clays and silts (see cross-section, Figure 6) ' The most common type is very clayey silt There are also thin, lenticular bed of sands In general, the soils are very fine grained and have a slightly plastic to moderately plastic deformation character It is apparent that the material is, in general, has low permeability and ' is very poorly transmissive These soil characteristics are suggestive of deposition in a low energy, fluvial, over-bank environment Specifics on individual borings and sampling intervals are described below Boring logs are attached in Appendix B ' Boring B_6 This boring was completed through pit of the former 1,000 gallon gasoline UST identified in ' the previously cited Geological Technics Inc report The tank pit is about 7 feet deep and below the level of the fill material, the soil exhibits petroleum staining and odor down to the groundwater Soil samples were clayey silt except the bottom (40 ft) sample which was sandy silt After the boring was drilled, a water sample was collected by using a disposable bailer conveyed down the inside of the hollow stem auger ' 2937 Veneman Ave,#B240 Geo-Phase Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0293