Pinnacle Engineering was hired by a Class I railroad to direct emergency response efforts related to a crude oil train derailment, oil release and fire that occurred adjacent to a large wetland area in rural North Dakota.
Emergency response activities included transloading of residual oil from damaged cars, recovery of oil from the surface water and wetland, and limited excavation of impacted soils beneath the track bed and within the right of way. Because the rail line was active, impacted soils could not be completely removed without impacting the adjacent wetland and creating significant down time for the railroad. Flushing and recovery of oil from surface water and shallow groundwater continued from trenches until the recovery of oil waned.
Based on previous successful efforts using bioremediation at Bakken crude oil release sites and the recommendation provided by Pinnacle Engineering, North Dakota regulatory officials approved the use of bioremediation injection into the ballast to support additional reduction of oil.
Pinnacle repurposed existing infrastructure (containment trenches, sumps, water treatment system, and dewatering pumps) to complete a two-phased injection effort using a mixture of 2,000 gallons of water and 1,500 pounds of bioremediation amendment. First, Pinnacle applied the bioremediation mixture into a collection trench and sump area to artificially raise the groundwater and fully saturate the track bed. The rail bed ballast surface was then flushed with a high dose of the mixture to remove remaining crude oil. A series of piezometers were placed along the collection trench and rail bed slope to allow monitoring of oil reduction. The monitoring program consisted of measurement of oil thickness as well as analytical testing of a series of parameters to observe the degradation of the crude oil.
Initial results have indicated significant oil removal within the piezometer network. Free product thicknesses (initially almost eight inches) were reduced to dissolved phase contaminants below 10,000 parts per million of petroleum hydrocarbons over the first few months of monitoring prior to winter freeze up. Ongoing monitoring will verify whether the phased application addressed residual oil. If residual oil remains, a second application may be necessary to provide a final polish prior to closure of the site.