Soils: Tarrant Association (gently undulating).

Known: Historically used as a landfill area, primarily for garbage disposal and burning trash. The landfill was filled in 1990-1991. The garbage disposal area was field verified and is approximately 1.2 acres in size.

Previous Investigations: Under Order 67, available records at CSSA were reviewed for an evaluation of groundwater contamination. Three geophysical anomalies were observed during an EM geophysical survey (1 February 1995). A GPR survey was completed on 15 March 1995.

Also under Order 67, seven soil borings were completed between 7 and 16 March 1995. Soil/rock samples were collected during drilling activities, and one groundwater sample was collected from SB1 on 9 March 1995. PCE, TCE, vinyl chloride, chromium, lead and nickel were all detected in the soil/rock samples above comparison criteria. PCE, cis-1,2-DCE, TCE and vinyl chloride were detected in the groundwater sample above MCLs. Soil and groundwater results are summarized in Table B3-1 and Table B3-2, respectively.

Two phases of soil gas surveys were completed during June and November/December 1995. PCE and TCE were observed at high concentrations; cis-1,2-DCE was detected in association with the PCE and TCE.

In February 1996, the Work Plan for the SVE Pilot Test System was submitted to the EPA and TNRCC. Between 19 and 23 February 1996, twelve soil borings were advanced and completed as six vapor extraction wells (VEWs) and six vapor monitoring points (VMPs) within the borings for a soil vapor extraction pilot test. A total of 15 soil samples were collected from 10 of the borings. TCE and cis-1,2-DCE concentrations exceeded RRS2 standards in most of the samples, as shown in Table B3-3.

On 4 and 5 March 1996, a blower was manifolded to the vapor extraction wells in preparation for the SVE pilot test. On 5 and 7 March 1996, initial soil gas samples were collected from the vapor extraction wells and monitoring points. The initial soil gas samples were sampled for oxygen, carbon dioxide and TVH using field instruments, and a small number of samples were collected in canisters for VOCs testing by an off-site laboratory. On 6 March 1996, an air permeability test was performed, extracting air from VEW-6 and monitoring pressure responses at test points. Between 7 and 13 March 1996, a second air permeability test was performed, extracting air from VEW-1 and monitoring pressure responses at test points. VOCs emissions from the blower exhaust were monitored and air samples were collected from the emissions to determine the mass removal of VOCs during the second permeability test. On 13 March 1996, multiple configuration testing was performed on the SVE system to identify the interconnections in the subsurface of the trench. The blower was shut off and 15-20 gallons of water were drained from the separator tank.

In April 1996, Parsons ES, on behalf of CSSA, filed a standard exemption with the TNRCC for SVE air emissions. The TNRCC approved the standard exemption in June 1996.

Under RL17, Parsons ES submitted the Addendum to SVE Test Work Plan for performing an SVE treatability study at SWMU B-3 to AFCEE, EPA and the TNRCC in December 1996. In addition, a notice of alteration to the standard exemption Registration No. 32405 for operating the SVE system from a different extraction configuration was submitted.

On 26 and 27 December 1997, four confirmation soil borings near MPA, MPD, VEW-1 and VEW-2 were advanced. Confirmation soil samples were collected from the borings. Between 26 and 30 December 1996 twelve additional soil borings were advanced and twelve vapor extraction wells were installed for a SVE treatability study test. Soil samples were collected from the borings and analyzed for metals and VOCs.

On 6 and 7 January 1997, the twelve newly installed VEWs were manifolded to the pilot test system. Pressure response testing was performed at all VEWs and VMPs that were not connected to the existing system. Air emission samples were collected from the blower exhaust and soil gas samples were collected from each VEW flow line for field screening and off-site laboratory testing. On 7 January 1997 the blower system was shut off and Parsons ES completed a hydrocarbon recovery test. Soil gas samples were collected throughout the test period and field screened for oxygen, TVH and carbon dioxide.

In February/March 1997, Parsons ES reconfigured the extraction well network, consisting of 6 VEWs, and restarted the blower system. Air emission samples were collected from the blower exhaust and monitored soil gas changes and pressure responses from non-extracting VEWs and VMPs for a 28-day multiple configuration test. Emission samples were collected for off-site laboratory analysis. In March, the system was reconfigured a second time and a second, fourteen day multiple configuration test was completed (13 through 27 March 1997). Emission samples were collected for off-site laboratory analysis. In April, the system was reconfigured a third time and a third multiple configuration test was completed. Emission samples were collected for off-site laboratory analysis.

In June 1997, Parsons ES designed and procured an automated timer for the moisture separatory drain attached to the blower system. Installation of the timer is pending.

In July 1997, Parsons ES submitted a draft technical report on the SVE expanded pilot study. Final submission of this report is pending resolution of the ITS Laboratory data issues.

Data Needs: Continued study of the SVE system is necessary. The SVE system will be operated for another 12 months under RL74 and RL83. The treatability study work plan is included in Volume 4.