ARCHIVED REPORTS_SEPARATE PHASE HYDROCARBON INVESTIGATION UNOCAL EXTRACTION WELL PILOT STUDY 2011

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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 The total groundwater extracted from GWE-1 was 147.5 gallons, when averaged over time, this would be approximately <0.11 gpm. Groundwater extraction data can be viewed in Table 2. The total mass of TPHg removed during the pilot test from soil vapor was estimated using analytical results for TPHg as hexane, mass flow rates, and system runtime. The calculations are presented in Table 6. Similar calculations based on FID readings as hexane were not completed because of the scale of the difference between laboratory results and FID measurements. Other chemical constituents such as BTEX were not calculated individually because those laboratory results were all non-detect and are also assumed to be incorporated within the TPHg results as part of the applicable carbon range. During TPE on GWE-1, approximately 3.05 lbs of TPHg were removed by SVE. The removal rate was approximately 3.14 Ib/day. Calculations of mass removal by SVE are presented in Table 6. During TPE on GWE-2, the removal of chemical constituents is not directly calculated because groundwater analytical samples were not collected during TPE and also due to low groundwater production and flow rates. During the first half of the TPE test on GWE-2, the stinger tube orifice was lowered into the well casing approximately 13 feet bgs, which was approximately the level of the air/water interface inside the well. It was lowered to 17 feet bgs for the remainder of the test, but produced little groundwater. Despite lowering the stinger tube orifice to the bottom of the well little to no groundwater was produced following the deeper placement. Presentation of groundwater chemical constituent total removal and removal rates is reserved for the GWE test data and results sections below where the information collected is more viable and meaningful for such an analysis. 4.11 GWE-1 AND GWE-2 CONCLUSIONS The results of the GWE and TPE tests were evaluated with the following objective feasibility criteria: • Projected groundwater recovery rates • Projected SVE vapor flow rates • Projected GWE and SVE chemical mass removal rates • Projected information about GWE and SVE operational parameters • Conceptual design of GWE and SVE from GWE-1 and GWE-2 Groundwater extraction and treatment from GWE-1 and GWE-2 is considered a necessity because those activities may help to recover chemical mass from the UOU and maintain cleanliness of fill material placed there by the SRDA following excavation activities. GWE-1 (northernmost GWE well) and GWE-2 (the southernmost GWE well) are located in the GCT that was completed on the western boundary of the UOU excavation fill. The floor of the GCT slopes from north-to-south; thus when pumping from the GCT is initiated downstream, groundwater will tend to flow first through GWE-1 and then to GWE-2; this mimics the Site geology where, in general, groundwater has a tendency to flow from near Weber Avenue to the north through the 4.13