WORK PLANS - Laserfiche WebLink

Home Browse Search

swo, 15 March 2005 AGE-NC Project No. 04-1168 Page 2 of 9 fluvial,and alluvial environments with sediment sources being the mountain ranges surrounding the valley(Olmsted and Davis, 1961);the site itself is located on unconsolidated and.semi-consolidated alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and Geology, 1977).Rocks composing the basement complex of the Province have not been completely defined but are believed to be metamorphic and igneous in origin. The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin(Basin 5-22). The nearest surface water feature to the site is the Stockton Diverting Canal,located approximately 1,600 feet northeast of the site.Based upon ground water maps prepared by the San Joaquin County Flood Control and Water Conservation District and well information obtained from nearby sites, ground water flow direction tends to vary between northwest and west-southwest near the site. Ground water is currently estimated to occur at a depth between 55 and 65 feet below surface grade (bsg). Ground water depths and flow directions may be greatly modified by local recharge and discharge patterns. 2.2. UNDERGROUND STORAGE TANK REMOVAL According to records on file with the SJCEHD, four underground storage tanks (USTs) were formerly located on the property.Three of the USTs were located in a common excavation,west of the on-site building;a fourth UST,presumably used for waste oil,was located south(behind)of the on-site building. In 1998,the four USTs were removed by Paydirt Excavation.The USTs had been out of commission and empty at the time of removal. Soil samples were collected from the UST excavation, former piping areas and dispenser island area. Petroleum hydrocarbons were not detected in soil samples collected at the time of removal. 2.3. PREVIOUS INVESTIGATIONS On 19 July 2004, three soil probe borings (B 1 though 133) were advanced at the site as part of assessment activities(Figure 2)to determine if petroleum hydrocarbon impacted soil and/or ground water was present beneath'the site. Boring B 1 was advanced in the former tank pit to a depth of approximately 30 feet bsg,whereupon refusal was encountered as the result ofpea gravel falling into the boring from the overlying tank pit. Boring B2 was advanced as a continuation of B I-located 10 feet north of B 1 just outside the tank pit. Samples were collected in boring B2 starting at 35 feet bsg Advanced GeoEnvironmental,Inc.