Ex-Situ Thermal Soil Remediation
Cold Bay, Alaska
A remediation technology firm located in Anchorage, Alaska, under Total Environmental Restoration Contract with the U.S. Army Engineer District, entered into an agreement with Midwest Soil Remediation, Inc. (MSR) in late February, 2006. This contract included MSR being responsible for handling and treatment of petroleum, oil, and lubricant contaminated soils from the Formerly Used Defense Site of Fort Randall. The site was located in the remote City of Cold Bay, about 30 miles from the west end of the Alaska Peninsula, and approximately 640 miles southwest of Anchorage. Cold Bay’s maritime climate is characterized by frequent light rains, cloudy, foggy conditions combined with 30 mph winds and gusts of around 50 mph, which presented MSR with some unique challenges.
MSR’s scope of work at Fort Randall included the following key elements:
- Produce an Alaska Department of Environmental Conservation (ADEC) approved site specific Operations Plan.
- Obtain an Air Permit from the State of Alaska.
- Supply a State Certified truck scale.
- Construct / manage / decommission containment areas.
- Provide third party confirmation sampling of treated soils.
- Transport and screen soils to <2”.
- Thermal soil treatment.
- Source testing of thermal unit.
- Site restoration.
Although MSR possesses the equipment, and employs personnel very experienced with excavating contaminated soils, the excavation and backfilling tasks at this site were performed under separate contract by an Alaskan excavating company. MSR also subcontracted third party sampling and the required source testing to Alaskan firms.
Since the only mode of transportation in or out of Cold Bay is by air or sea, MSR utilized a barge company with a port in Seattle, WA to transport its 525D thermal system and support equipment to Cold Bay. The barge was equipped with a heavy duty crane capable of lifting in excess of 85,000 lbs. in order to lift all of the equipment from the barge deck and set it onto the Cold Bay dock. On June 4th, 2006; nearly 2,000 miles and 12 days later, the equipment arrived in Cold Bay. This mobilization effort consisted of transporting the following equipment to the project:
- 525D Primary thermal desorption unit. (Rotary kiln and Baghouse)
- 525D Secondary thermal desorption unit. (Thermal oxidizer)
- (2) Caterpillar front end loaders.
- (2) 20 foot Connex boxes.
- 40 foot support trailer containing parts, supplies, office space, and continuous emissions monitoring system.
- 4,000 gallon poly tank mounted on a towable trailer.
- Service truck fully equipped for field maintenance.
- Portable truck scale system.
Once the equipment was brought off the dock and temporarily staged, site setup began with the collection of ground surface soil samples. These samples were collected from the work areas designated for the remediation effort in order to identify any baseline, or background soil contamination. Following this sampling event, MSR proceeded in accordance with the approved Operations Plan to construct separate contaminated soil, thermal treatment, and treated soil containment areas. The thermal unit and truck scale were then positioned on the treatment pad and constructed. While MSR performed mechanical and control systems check-out of the thermal unit, the State of Alaska Department of Transportation mobilized to the site to test and certify the truck scale. The thermal unit was then put into operation processing contaminated soil on June 20th, 2006.
In compliance with conditions set forth in the State of Alaska Air Quality Permit, a source test was performed on July 11-12, 2006. The testing consisted of measuring total particulate emissions in the exhaust gases, a relative accuracy test audit (RATA) of the units continuous emissions monitoring system, and Method 9 visual emissions observation. Particulate testing consisted of three 60-minute runs, and the RATA consisted of ten, 22-minute runs. Results of the particulate testing confirmed the unit was operating within the conditions of the permit, with emissions averaging less than 0.032 grains per standard cubic foot of exhaust gas at a soil processing rate of approximately 18 tons per hour. Carbon monoxide and oxygen continuous emission monitors tested to be well within the acceptable range of error limits dictated by 40 CFR 60, Appendix B. All Method 9 visual emission observations were 0.
Over the course of the project the thermal unit processed soils originating from 3 separate areas at Fort Randall, with excavation focusing on the most highly contaminated material down to a depth of approximately 15 feet below ground surface. Field screening was conducted to guide the limits of the excavation which targeted soils containing greater than 10,000 ppm Diesel Range Organics (DRO); leaving the lesser contaminated soils for future treatment utilizing alternative technologies. Site soil moisture ranged from 10% up to 68%, and the upper DRO concentrations approached 4% by weight.
With the exception of a 9 day operations delay due to a depleting fuel supply in the area, the system processed in excess of 8,000 tons in just over 30 operating days. The thermal treatment unit, treatment pad, contaminated soil pad, and all support equipment was demobilized from the work site 5 days following the completion of treatment. Following the removal of treated soils from the treated soil containment pad by the excavation subcontractor, MSR removed the remaining liners, and restored the work area.