EPA’s clean-up contractor, Shaw E & I, is continuously conducting operation and maintenance (O & M) on the two oil recovery systems including repairing or replacing pumps, motors, belts, hoses, and computer software. They have also been backwashing the carbon vessels and replacing carbon as necessary within the groundwater treatment train; and collecting and disposing of contaminated boom, snare, and absorbent pads. In February and March, 2007, Shaw completed the construction of a dam which was placed to effectively cut off the tailrace from the Housatonic River. WestonSolutions, Inc., EPA’s Superfund Technical Assistance and Response Team (START) contractor, was used to provide design specifications for the dam. After minor excavation and grading of the tailrace floor, the dam was constructed with “supersacks” (large sandbags measuring approximately 3’ x 3’ when filled) placed in a pyramid configuration, smaller sandbags, polyethylene sheeting, geotextile fabric, and riprap. Upon completion of the dam, the sides of the raceway were stabilized with additional concrete blocks.
In March, 2007, a 5,000 gallon frac tank was added to the groundwater treatment train (Derby-2 system). This was done to settle out any oil inadvertently being pumped into the system with the groundwater and to reduce any iron precipitation that has been clogging the carbon vessels.
In April, 2007, a major New England storm raised the level of the Housatonic River significantly and completely submerged the facility tailrace. The two existing oil recovery systems were largely unaffected, although a pump being used to dewater the tailrace was damaged and needed to be replaced. In addition, a number of the existing on-site monitoring wells were gauged for oil thickness and compared to past readings.
At the request of the EPA OSC, the USCG NPFC raised the FPN ceiling by $1.7 million to a new total of $8,447,800. In May and June, 2007, a tube type oil skimmer was installed to retrieve oil from the surface water of the tailrace. The skimmer was placed on a pad above the race with an adjacent oil storage tank. The constantly moving tube hangs from the skimmer into the race and is directed through the race via guides and runners installed by Shaw. As the tube is drawn back up into the skimmer unit, it brings the oil up with it, which is scraped off of the tube and then flows into the storage tank. In addition, the tailrace was dewatered on a number of occasions and the walls and pipes within the race were pressure washed to remove years of oily buildup. The oil was picked up by the skimmer.
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