Squaw Creek Truck Plaza
A Triad planning exercise for the Squaw Creek Truck Plaza, Mound City, Missouri.
Site Background
In September 2006, a systematic planning meeting was held in Jefferson City, Missouri, about the Squaw Creek Truck Plaza, Mound City, Missouri. Attendees included MDNR, the state contractor administering the PSTIF, a Squaw Creek Truck Plaza consultant, and EPA and Argonne representatives.
During the brief systematic planning session, MDNR elaborated on several goals to be achieved:
- Determination of the construction details for two water supply wells
- Site characterization:
- Vadose zone soil to nonresidential thresholds (MDNR 2004)
- Groundwater: the extent of free product and for dissolved-phase default target levels (DTLs)
- Utility investigation and characterization
- Performance of a risk assessment
- Development of a risk management plan (RMP)
- Implementation of RMP and monitoring for plume stability
Critical components of developing future decision logic were the need to:
- manage risks associated with the water supply wells,
- develop provisional Tier II site-specific target levels (SSTLs) to aid in the delineation of contamination in the vadose zone (MDNR 2004),
- anticipate remedial actions likely to be implemented for those projects determined to require remedial action, and
- devise approaches to determine the fate and extent of free product and dissolved-phase contaminants potentially moving northeast toward a steep slope and an intermittent tributary at the base of the embankment.
In this case, participants agreed that two-phase vapor extraction would be a likely remedial technology for the site. Participants were indefinite about how to best evaluate groundwater near the steep slope pending the results of a future groundwater monitoring effort and the creation of a base map to help refine the CSM.
Participants expressed a desire to use a collaborative on-line workspace QuickPlace Squaw Creek Web site as a resource for communicating, critiquing and strengthening planning documents during the plan development stage. Participants used the on-line workspace and multiple teleconferences led by EPA TII and PSTIF to discuss the results of newly generated data and to facilitate plan (investigation/remediation) development and approval.
Site Progress
A primary project document for site characterization and risk assessment was submitted to MDNR on August 22, 2007. The scope of work for the characterization and risk assessment involved the collection of analytical data from soil samples for the risk assessment and the installation of monitoring wells between the area of release and the downgradient monitoring wells to more accurately delineate the groundwater plume. The team developed a DWS for the advancement and logging of soil borings along pipe chases at the site(s) of releases and in former tank pits. The Squaw Creek team chose RTMS technologies (in this case, a MiniRae 2000 photoionization detector [PID]) to scan and identify select soil intervals from the sample borings for analyses in an off-site laboratory. The work plan also addressed the installation of monitoring wells, the assessment of water supply wells, and modeling of free phase product.
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