Scope of Work:
- Site preparation at the Allen Mills project required heavy equipment access from the top of the mill, located at the top of the river gorge, to the raceway itself. Portions of the roof were removed to provide overhead access and all supplies and equipment were lowered by crane.
- Prior to sediment removal, the entire raceway was dewatered using submersible pumps. The water was pumped up one story to interim holding tanks where bag filters removed the majority of the sediment. Secondary pumps transferred the water up to ground level and across the site to the Hudson Falls water treatment plant for final treatment. The total volume of water removed from the work area exceeded 9,000 gallons per day.
- Sediment and debris removal was performed using skid steers and a small excavator. As sediment was collected, it was stockpiled in a 40’ x 50’ staging area located within the raceway. Excess water was allowed to drain off to the sump area. The dewatering system then captured the runoff and transferred it up to the WWTP.
- Dewatered material was loaded into skip buckets and lifted out of the work area by crane. Dump trailers located at the top of the mill were directly loaded with the crane and shipped for off-site disposal.
- As sediment removal proceeded, fractures in the rock walls contributed additional oil and water to the work area. These fractures were sealed and grouted as necessary to minimize the influent.
- A total of 1,625 tons of TSCA regulated sediment was removed from the raceway. Due to the effective isolation of the raceway, and the dewatering operation, waste materials removed from the raceway did not need to be further solidified.
- Final cleaning of the work area included pressure washing of the walls and floor of the raceway. All decontamination fluids were pumped up to the WWTP.