Fort Riley CERCLA Solutions

Fort Riley CERCLA Solutions

Location: Fort Riley, Kan.

Client: U.S. Army Corps of Engineers — Kansas City District

Completion Date: Ongoing

Burns & McDonnell was contracted to assist Fort Riley in conducting its Environmental Restoration Program (ERP). Base operations through time have resulted in a number of environmental problems (CERCLA issues) related to landfills, pesticide storage and solvent use resulting in Fort Riley being added to the National Priority List (NPL) in 1991.

The major contaminants of concern are chlorinated solvents, metals and petroleum hydrocarbons. Burns & McDonnell has provided a wide range of services including site investigations; soil, groundwater and air monitoring, sampling, and data assessment; quality oversight; and remedial system installation and operation at multiple sites within the installation of Fort Riley for more than $12.7 million of total contract value.

  • More than 50 preliminary assessments/site investigations (PA/SIs)
  • Three remedial investigations (RIs) with baseline risk assessments (BLRAs)
  • Three feasibility studies (FSs)
  • Three proposed plans
  • Three records of decisions (RODs)
  • Three engineering evaluation and cost analysis reports (EE/CAs)
  • Five treatability studies, pilot tests and bench-scale tests

Site & Remedial Investigations

Investigations were conducted at multiple sites at Fort Riley to determine the nature and extent of contamination in soil and groundwater. Comprehensive sitewide documents, including a site health and safety plan, monitoring well installation plan, field sampling plan, and quality assurance project plan, were used to decrease plan preparation costs and ensure sitewide consistency and quality. The extensive use of a phased approach and the use of on-site analytical laboratories for site characterization saved Fort Riley both time and money. Comprehensive remedial investigations (RIs) were conducted for the former Fire Training Area Marshall Army Airfield (MAAF), former Building 354 Area Solvent Detections, and dry cleaning facilities area (DCFA) sites. More than 50 PA/SIs have been conducted at Fort Riley, with most resulting in no further investigation.

Much of the Fort Riley RI work has been performed within sensitive areas, including areas adjacent to the Kansas River, which has been designated as a critical wildlife habitat for bald eagles that winter at Fort Riley. The execution of fieldwork within this area required close coordination with the U.S. Fish and Wildlife Service and Fort Riley Conservation personnel. Burns & McDonnell has repeatedly performed field activities within this area with no adverse impacts to the seasonal bald eagle population.

Risk Assessments

Human and ecological risk assessments have been conducted for the MAAF, 354 and DCFA sites. At the MAAF site, the results of the sequential degradation model were used to determine no future risk. Cleanup levels in soil were calculated using site-specific data to provide a more favorable action level for soils in the source area. At the DCFA site, the human health and ecological risk assessments included evaluation of potentially impacted sediment pore water resulting from groundwater intercepting the Kansas River. The 354 and DCFA risk assessments showed no current or future risk from exposure to soil or groundwater. Wetlands and flood plains were identified as part of the ecological risk assessments for all three areas. The Fort Riley risk assessments were well-received and approved by the regulatory agencies with minimal revisions required.

Natural Attenuation Evaluation

Monitored natural attenuation (MNA) has been selected as the site remedy at the MAAF, 354 and DCFA sites. The decision to adopt MNA was based on a thorough documentation of site hydrogeological and hydrogeochemical conditions. Natural attenuation (NA) parameter data was collected during periodic groundwater sampling events and was evaluated in accordance with U.S. Environmental Protection Agency protocols. The re-evaluations of monitoring well networks to support MNA at the MAAF, 354 and DCFA sites have allowed for a reduction in the sampling intervals, monitoring wells and the number of analytes collected. These efforts have saved Fort Riley money and streamlined the execution of groundwater field events.

In addition, Burns & McDonnell designed a microcosm study and a tracer study to evaluate the feasibility of NA as a final remedy for chlorinated solvent contamination at the MAAF site. The microcosm study included a nine-month laboratory study constructed from site soil and groundwater to determine the degree of biodegradation occurring in the aquifer. The project objectives were to gain essential hydrogeologic data related to contaminant fate and transport and to facilitate evaluation of remedial technologies available for the site.

Feasibility Studies & EE/CA

FSs have been prepared for the MAAF, 354 and DCFA sites. Burns & McDonnell selected a variety of cutting-edge remedial technologies to evaluate as a part of the FS process. These included enhanced bioremediation, zero-valent iron permeable reactive barrier wall, in-situ redox manipulation, high pressure injection of a potassium permanganate slurry, vadose zone injection of sodium permanganate, vegetable oil injection, and bimetallic nanoscale particle injection. The evaluations included comparison of effectiveness, implementability and cost. An EE/CA was prepared for both the MAAF and 354 sites following CERCLA guidance. Burns & McDonnell evaluated a number of interim actions including a permeable reactive barrier, SVE, in-situ mixing with potassium permanganate, and pump and treat. At the MAAF, results of groundwater modeling were used to aid in the development of the remedial action objectives (RAOs) and preliminary remediation goals (PRGs).

Proposed Plans & Records of Decisions (ROD)

Burns & McDonnell has prepared proposed plans for the MAAF, 354 and DCFA sites. All proposed plans were well-received by both the regulatory and public communities. The ROD for MAAF was signed in July 2005, and the ROD for 354 in July 2006. Preparation of the ROD for DCFA is ongoing.

Remediation Pilot Studies

Burns & McDonnell applied an innovative in-situ mixing technology at the 354 site using potassium permanganate to treat an area of shallow soil contaminated with chlorinated solvent. This treatment method enabled the efficient mixing of a potassium permanganate oxidant with the soil, allowing for enhanced contact between the oxidant and contaminant. This treatment technology resulted in a significant drop in contaminant concentrations within the soil.

At DCFA, shallow contaminated soil at a defined source area was excavated and treated at a landfarm treatment cell constructed at the fort. The vadose zone, sanitary sewer line and an abandoned gas line located within a utility corridor at the source area were also treated by injecting a sodium permanganate slurry. Subsurface groundwater was treated with vegetable oil to enhance the NA capabilities in selected areas and with potassium permanganate slurry to aggressively address groundwater hot spots.