ARCHIVED REPORTS_WELL ABANDONMENT, SOIL AND GROUNDWATER INVESTIGATION REPORT 2009

Home Browse Search

' Monitoring Well Destruction and Soil and Groundwater Investigation Report US Can—Welty Road September 24,2009 detected in SB-38, SB-40 through SB-43, and the borings mentioned in the previous sentence. ' • The vertical extent of affected soil has been delineated by a soil sample collected from SB-26 at 83.5 feet bgs. • The lateral extent of affected soil in Area 1 has not been delineated west of SB-34, and the lateral extent of affected groundwater in Area 1 has not been delineated west of SB-34 or east of SB-19. ' • The lateral extent of affected soil and groundwater in Area 2 has not been delineated the west of that area. to • The lateral extent of affected soil in Area 3 has not been delineated to the east of SB-23 and SB-28. Groundwater has not been delineated to the east of SB-23 and SB-28, and northwest of SB-28 where SPH was observed in SB-38 through SB-41 and SB-43. • Further delineation of groundwater east of SB-23 and SB-28 would b e difficult due to the possible presence of other potential hydrocarbon sources in this area. Additional sources, ' if any, would complicate data interpretation and potentially provide misleading results. • SPH were observed in several borings that indicated affected soil, and also in several borings that did not indicate affected soil. The borings that contained SPH but no affected soil are in the northwest part of the investigation area. The lateral extent of SPH has not been delineated to the northwest. ' • The vertical extent of affected groundwater has been delineated by a sample collected from SB-26 at 82 feet bgs. • Results of General Minerals analyses indicate that the zone of first-encountered ' groundwater is unlikely to be used for drinking water purposes. SAIC proposes the following additional work (see Figure 4 for proposed boring locations): • Advance two borings west of Areas 1 and 2 to define the up-gradient extent of affected soil and groundwater. ' • Advance two borings within the northeast shoulder of Highway 33 to define the lateral extent of affected soil encountered in SB-23 and SB-28. Groundwater samples will not be collected from these borings, as it is likely they would exceed WQOs for one or more of the COPCs. • Advance contingency borings depending on field observations and laboratory analytical ' results. Due to access negotiations, contingency borings, if any, would be advanced in a separate mobilization. • Destroy monitoring wells MW-1 through MW-3. TPHd were reported below the WQO in MW-3 during the July 2009 split-sampling event. Groundwater from MW-1 and MW-2 is affected but groundwater samples collected from soil borings up gradient and down gradient of these wells provide sufficient delineation. Therefore, MW-1 through MW-3, installed between 1996 and 1998, are no longer required. 9 -"N AV From science to solutions