ARCHIVED REPORTS_XR0012380 - Laserfiche WebLink

Home Browse Search

n !s ERI 205503 R02 Tosco 76 Service Station 5886,Stockton,California March 2, 1999 Soil cuttings generated during drilling were stockpiled on site and sampled for laboratory analyses, pending appropriate disposal by Tosco Based upon telephone conversations and field discussions between ERI representatives and Mr Rowe, soil borings HA4 through HA6 were not drilled during this phase of work Mr Rowe indicated that in his opinion, these soil borings (located in the vicinity of former dispenser area drams) would not provide pertinent data to the investigation Analytical Mh l SamplesR Selected soil samples collected from the bonngs were submitted under Chain of Custody Record to Kiff Analytical LLC(Kiff[California State Certification Number 2236]) in Davis, California The laboratory reports and Chain of Custody Records are provided in Attachment G Select soil samples were analyzed for TEPHd, TPPHg, BTEX, MTBE, DIPE, ETBE, TAME, tertiary butanol,methanol, and ethanol using the methods listed in Table 1 ERI also collected one composite soil sample (4 brass sleeves) from the drill cutting stockpile and submitted the sample under Chain of Custody Protocol to Kiff The composite sample was analyzed for TEPHd, TPPHg, BTEX, and total lead using the methods listed in Table 1 nA lalSAical Methods- Groundwater Samples Groundwater samples collected from borings B8 through B10 were submitted under Chain of Custody . Record to Kiff The laboratory reports and Chain of Custody Records are provided in Attachment G Groundwater samples were analyzed for TEPHd, TPPHg,BTEX, MTBE, DIPE, ETBE, TAME, tertiary butanol, methanol, and ethanol using the methods listed in Table 2 RESULTS OF INVESTIGATION Site Geology Sediments encountered in off-site borings B8 and B9, and in the upper portion of boring B 10 (to a depth of 20 feet bgs) typically consisted of heterogeneous mixtures of silt, clay, and fine- to medium-grained sand Flowing sand was encountered in borings B9 and B10 at approximately 20 feet bgs The sand filled the core sampler up to approximately 20 feet bgs in boring B10 Therefore in-situ samples were not collected or observed below 20 feet bgs in boring B10 Groundwater was initially encountered at approximately 8 to 10 feet bgs with saturated zones encountered at depths ranging from approximately 13 5 to 18 feet bgs, and 20 to 36 feet bgs These saturated zones typically consisted of sandy silt, sandy clay, and/or fine- to medium-grained sand and were separated by less heterogeneous and less permeable silty clay and clayey silt The contacts between the upper zones of variable permeability appeared gradational while the contact between the lower clay and deepest encountered sand layer was abrupt . 5