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    Prior to initiating the removal action in Building 90, 12 soil borings should be drilled inside the building around the north vat, near the suspected source vat, and in other portions of the building, to determine the contaminant mass underlying the building.  These borings would be completed as combination vapor monitoring points/subslab extraction wells for use as subslab ventilation and possibly as monitoring points during the planned SVE treatability study (outside Building 90).  All vapor extraction wells installed inside the building should include a valve and fitting to enable each point to be used as a vapor monitoring point.  Each well will include a riser to the ceiling, and will be manifolded to an extraction blower located on the east side of the building to enable ventilation (extraction) of the subslab fill material.  Drilling activities will need to be scheduled during the evenings or weekends to reduce potential exposures to CSSA employees working inside the building.  

       The removal action should be expanded to include the drainage ditch outside and west of Building 90.  This will require removal of asphalt and underlying soil in addition to soil in the ditch.  Soil samples will be collected along the ditch and from under the asphalt.  This sampling will be completed in conjunction with the installation and sampling of VEWs and VMPs inside Building 90.  Soil/rock sampling from the VEWs/VMPs will be used to estimate the volume of material that will need to be removed from the vat area.  The depths attained during this removal action will also be used to estimate the potential thickness of impacted materials underlying Building 90 in the vicinity of the suspected leaking vat.

       Asphalt uncovered during the removal action of the ditch will need to be replaced.  An engineering plan will be prepared so that drainage from the gutters will be diverted away from the ditch and Building 90 during future rainfall events.  The ditch will be backfilled to grade, and covered with asphalt.  

      A structural engineering evaluation and construction quality assurance (CQA) should be included for replacement of the building floor if removal actions inside Building 90 are warranted.  CSSA indicated the outer dock of Building 90 might need to be removed to facilitate better access to the excavation areas inside the building.  Repair of the dock would be required as directed by CSSA.

       Waste removal volumes estimated in the technical approach document and proposal (dated September 14, 2001) inside the building may need to be adjusted to account for greater excavation volumes than the volumes generated from the 2 foot depth estimated in the technical approach.  Under the vat, a maximum of 2 feet will be removed, but under other portions of the building floor, the thickness of excavated fill material may exceed 4-5 feet.  Soil borings designed to characterize waste underlying the building floor (described in a previous bullet) should provide better definition of the estimated waste volumes for the Environmental Cleanup Plan.

    The air permit for Building 90 will need to revisited with regard to the planned remediation efforts.  A standard exemption may need to be prepared for the subslab ventilation and for any removal actions requiring negative pressure engineering controls.  The standard exemptions will assume no off-gas treatment of the subslab treatment system, but CSSA requested that any extraction system in proximity to Building 90 be constructed with an off-gas treatment system.  CSSA suggested that any additional work (SVE or removal actions) should include responses to all air permitting issues associated with Building 90.  

    An evaluation of the potential effectiveness of a subslab SVE system will need to be completed as part of the removal action inside Building 90.  The SVE effectiveness testing would be completed prior to any removal action of contaminated fill material underlying the building so that volatile organics in soil gas could be ventilated prior to floor removal, and to determine whether subslab ventilation could effectively treat the contamination without having to disturb the building’s floor and operations.  

    Parsons Health and Safety Plan (HASP) will be expanded to address safety issues for all visitors to Building 90 during the removal action, including CSSA employees working in Building 90.  During any removal actions inside the building, temporary wood containment walls will be installed around the work area, and negative pressure airflow within this sealed portion of the building will be used to help reduce the potential for exposure to CSSA employees.

    Any removal action inside the building will concentrate on the existing citrus cleaner area currently used in the building and the underlying vat.  The subcontractor will be responsible for removing and re-installing the citrus cleaner after the floor has been rebuilt.  The subcontractor will not be required to re-build the vat after its removal.  Steel casing and screen, which may be used in subsequent SVE remedial efforts inside Building 90, will be installed within the excavation prior to backfilling and rebuilding the floor.  This casing will be plumbed with access along the western wall or through the wall to the exterior loading dock to enable ventilation (extraction) or injection of amendments to enhance contaminant removal from beneath the slab.

     Phase 1 – Electrical resistivity (expand by at least 1 week to existing technical approach) and add microgravity.  During the microgravity, Gary Cobb of Parsons indicated he would like to try another low-cost geophysical tool since the only cost to CSSA would be instrument rental (the testing could be performed in concert with microgravity testing).  CSSA and AFCEE suggested that this testing should be implemented immediately following the electrical resistivity testing.  

          Phase 2 – CSSA indicated that the Army might be interested in expanding resistivity and microgravity into other areas located to the south and west of Building 90, including off-post property to the west.  Work in this off-post area may require vegetative clearing and associated chipping (mostly cedars).  Ground Penetrating Radar is another geophysical testing technology that was recommended by CSSA and AFCEE for possible geophysical testing around Building 90.  Phase 2 geophysical testing also includes performing electrical resistivity under different conditions than the phase 1 testing over the same grid so that one test would be completed under saturated conditions and one test would be completed under dry conditions.  

          Phase 3 – Perform two-dimensional seismic testing over a broad area (at least 100 acres) and three-dimensional electrical resistivity over a small area (less than ½-acre), presumably in the vicinity of AOC 65.  The location of the three-dimensional array will be based on results of the two-dimensional resistivity testing performed in phases 1 and 2 described above.  If two-dimensional resistivity testing does not provide quality results, then the three-dimensional resistivity study may be waived.

          Phase 4 – The final phase of geophysical testing includes three-dimensional seismic and other borehole resistivity testing, such as cross-bore resistivity and borehole flow meter.  The three-dimensional seismic testing would be performed in a section of the two-dimensional seismic testing, and may involve shear-wave seismic testing.  Locations selected will be based on results of the two-dimensional seismic testing, but will likely by either near Building 90 or to the west toward Ralph Fair Road.  Given the high cost of three-dimensional seismic testing, utilization of three-dimensional testing will depend on the quality and usability of results from the two-dimensional seismic work.  Downhole geophysical testing technologies mentioned above will be evaluated and, if appropriate, planned in selected wells installed as part of the SVE treatability study.  These borehole geophysical technologies generally require saturated conditions, which may or not exist in the upper 150 feet during the duration of the treatability testing. 

          A weather station could be set up and continuously operated on the west side of Building 90 in the vicinity of up to six nested piezometers set to depths to 150 feet below grade.  

          The weather station would be fitted with a rain gauge, and each piezometer would be constructed with a downhole transducer.  A data recorder will be secured at the weather station and will record readings from both the rain gauge and each transducer to assess the affect of rainfall intensity on the migration of water into the various screened intervals.  The data recorder will be solar powered, and will be capable of transmitting real-time data to CSSA, either through telemetry or telephone lines. 

    Piezometers would be constructed with 25 feet of screen, and any piezometer below 100 feet below grade would be required to include surface casing similar to groundwater monitoring wells in the same area.  The screened intervals would be selected to provide complete coverage of the entire upper 150-foot profile of the unsaturated formation.  The piezometer casing inside diameter should be 2 inches.  Piezometers deeper than 100 feet would only be installed if the water table is deeper than 150 feet below grade during drilling to avoid the CSSA requirement for sampling saturated intervals to monitor for potential cross-contamination between intervals.  The completion method for piezometers may be revised in the future.  Parsons and CSSA will re-evaluate this decision at a later date.

          Groundwater will be sampled from the piezometers for analysis of volatile organic compounds following significant rainfall events.  A schedule for sampling the piezometers will be established in the treatability test plan, but it will entail sampling following major rainfall events (at least greater than 1.0 inch) on the day after the rainfall event, and periodically as the water levels in the wells drop.  These samples will be collected using dedicated bailers without purging or development.  The samples will considered “grab” samples and require minimal QA/QC.

         The current SOW from the September 14, 2001 technical approach only included one vapor extraction well (VEW) and three multi-depth vapor monitoring points (VMP).  Under the treatability study discussed at the meeting, six VEWs and six multi-depth VMPs would be installed for use in the SVE treatability study test.  The six VEWs would be installed on both sides of the building, with most installed on the west side near the building’s suspected vat and the associated drainage ditch.  The screened interval lengths of the VEWs would be limited to 25 feet, while the depths of the VEWs would extend to 30  feet, 50 feet, 75 feet, 100 feet, 125 feet, and 150 feet below grade.  The multi-depth VMPs would include up to four distinct screened intervals per boring and would extend to a maximum depth of 100 feet below grade.  Most of the VMPs would be located in the vicinity of Building 90 and the drainage ditch, with some VMPs located on the opposite side of the building from the main SVE VEW located closest to the suspected vat inside the building.  A summary table of the borehole completions is provided below.  These multi-depth monitoring points and VEWs should enable the treatability study to evaluate the depths where the highest levels of contamination appear to be present and the interconnectivity of the fractures between multiple well locations and depth intervals.  

          Locations of the VEWs and VMPs will be selected based on the geophysical testing results.  These wells will serve multiple purposes other than their use as a treatability test or monitoring well.  These wells will serve to validate findings from the geophysical testing, and will also provide additional data on contaminant and groundwater movement into the lower saturated zones of the formation.  The top of each VEW manifold will be constructed to enable collection of water level data or groundwater samples.  The frequency of collecting groundwater samples from these wells will be described in the Treatability Test Plan, but several rounds of data collection would be anticipated.  The VEWs will be designated: AOC65-VEW1-LGR, AOC65-VEW2-LGR, AOC65-VEW3-LGR, AOC65-VEW4-LGR, AOC65-VEW5-LGR, and AOC65-VEW6-LGR.  The VMPs will be designated AOC65-VMP1-LGR, AOC65-VMP2-LGR, AOC65-VMP3-LGR, AOC65-VMP4-LGR, AOC65-VMP5-LGR, and AOC65-VMP6-LGR.

         An air emissions standard exemption for the SVE system will be prepared assuming no off-gas treatment of the SVE treatability system, but CSSA requested that any extraction system in proximity to Building 90 be constructed with an off-gas treatment system.  CSSA suggested an activated carbon treatment system be used for both the treatability study blower and the subslab ventilation blower, given their relatively low levels of contaminants anticipated in the emission flow.

         Treatability testing should be performed over a longer period of time than indicated in the TO 0058 SOW to enable collection of data through several heavy rainfall events, and to assess effectiveness of pulsing extraction on the performance of the SVE system.  It may also be advantageous for CSSA and AFCEE to consider treatability testing of dual-phase extraction (liquid and air) pilot systems, such as vacuum enhanced pumping (VEP) so that its potential effectiveness of contaminant removal could be evaluated and compared to SVE.