FAR-MAR-CO subsite - Hastings Groundwater Contamination Site - Hastings, Nebraska
SSP&A is providing ongoing services as the lead hydrogeological consultant for the groundwater operable unit of the FAR-MAR-CO subsite of the Hastings groundwater contamination site. SSP&A completed a remedial investigation of the FAR-MAR-CO subsite in 1993. Subsequently, SSP&A developed a Focused Feasibility Study (FFS), and Engineering Evaluation/Cost Analysis (EECA) Report that established plans for an innovative Interim Remedy for groundwater collection and treatment. Since implementation of that remedy (1996/1997), SSP&A has overseen collection and interpretation of monitoring data, and been the primary technical contact for USEPA's concerns. At the current time, the Final Remedy is being implemented.
Carbon tetrachloride (CT) and ethylene dibromide (EDB) were released to soil and groundwater at the FAR-MAR-CO subsite due to the use of grain fumigants from the 1950s to 1970s. The resultant plumes of groundwater contamination extend for more than two miles downgradient within an alluvial sole-source aquifer of the high plains. The CT and EDB commingle with other contaminants, primarily TCE, that originated from other subsites of the Hastings groundwater contamination site. The scarcity of water in Nebraska necessitated an interim remedy that maximized the water's value, while still providing an effective collection and treatment system. The solution promoted by SSP&A in the 1993 FFS and EECA was to utilize the cooling tower of an existing coal-fired power plant as an air-stripper for contaminated groundwater extracted from a newly installed remediation well. Since 1997, the plume has been contained through groundwater extraction, primarily at "Well D." After piping to the Whelan Energy Center, the contaminated water is used as non-contact cooling water, and then sent to the cooling tower for treatment and discharge to the atmosphere.
In 2007, SSP&A submitted to USEPA a Feasibility Study for the final subsite remedy. Incorporated into this FS are groundwater flow and contaminant transport models developed with MODFLOW and MT3D, respectively. Following the 2009 approval of the Final Remedy Record of Decision, SSP&A has been implementing its required elements. The primary treatment of the groundwater remedy remains pumping and treating through the Well D – Whelan Energy Center System. Additional elements have included a transect of direct-push groundwater sampling locations to further delineate vertical boundaries of the groundwater contamination and installation additional nested groundwater monitoring wells using sonic drilling methods. In addition, SSP&A has completed a Source Area Enhanced Bioremediation project that included subsurface injection of emulsified vegetable oil (EVO) to assist in degradation of CT and EDB in the source area.