ARCHIVED REPORTS_SEPARATE PHASE HYDROCARBON INVESTIGATION UNOCAL EXTRACTION WELL PILOT STUDY 2011

Home Browse Search

Stantec Report of Findings for the Waterfront Towers Separate Phase Hydrocarbon Investigation and Unocal Extraction Well Pilot Study Waterfront Towers Parking Lot March 4, 2011 of lithology and estimation of SPH extent in the subsurface. Stantec's standard field procedures that were followed during this investigation are included in Appendix B. The boring log for DP- 22, computer generated CPT logs for DP-23 through DP-30, and computer generated UVOST plots for DP-23 through DP-30 are included in Appendix D. A brief description of each exploratory methodology is described below. 3.2.1 Borehole Clearance In order to minimize the risk of encountering underground utilities, on August 17, 2010, Stantec marked the proposed boring locations and met with a private utility locator (Cruz) to determine if any subsurface utilities or obstructions were located in the vicinity of the proposed wells. In addition, Stantec marked the boundaries of the proposed well locations and contacted Underground Service Alert (USA) prior to 48 hours before the initiation of field work to evaluate whether the proposed boring locations were clear of potential subsurface obstructions. Between August 23 and 25, 2010, all borehole locations were cleared to a depth of approximately eight feet bgs using an air lance and vacuum truck (air knife rig) and/or hand auger prior to commencement of mechanical direct push drilling. 3.2.2 DP-22 Verification Borehole-Continuous Core Direct push exploratory boring DP-22 was continuously cored to approximately 61 feet bgs. A Stantec geologist, under the direction of a California Professional Geologist and using the Unified Soil Classification System (USCS) and standard geologic techniques, logged the borehole for lithologic description. Soil samples were collected based on head space photo ionization detector (PID) screening for the highest concentrations. The general purpose of sampling DP-22 was to perform quality assurance and quality control (QA/QC) between in-situ field sampling and with the computer generated data (CPT and UVOST) obtained from adjacent borings. 3.2.2.1 Soil Sampling Analysis and Classification of DP-22 Based on PID readings and field observations, soil samples were collected from direct push rods deployed by the CPT rig. The samples were collected in two-inch diameter by six-inch long brass or stainless steel sleeves, capped at each end with Teflon® sheets and plastic caps, and were placed on ice in an insulated cooler until they were relinquished under chain-of- custody to a certified analytical laboratory. Samples were submitted under chain-of-custody protocol to Lancaster Laboratories and were analyzed for the following: • TPHd by Environmental Protection Agency (EPA) Method 8015M • TPHg; benzene, toluene, ethylbenzene, and total xylenes (BTEX compounds); and methyl tertiary-butyl ether (MtBE) by EPA Method 8260B 3.2