Arconic will resume in-river construction this spring to continue implementing a remediation plan selected by the EPA for the lower Grasse River. The plan, which was selected in 2013, calls for dredging and capping of sediment contaminated with polychlorinated biphenyls (PCBs) in a 7.2-mile stretch of the lower Grasse River.
Work that is scheduled this year includes removing sediment from Snug Harbor and a downstream area. The EPA had announced last month that there would be some modifications to the original plan. It now calls for removal of an additional 90,000 cubic yards of sediment from an area of the river near Snug Harbor, instead of capping.
The modification is being made to accommodate a new, larger tugboat purchased by the St. Lawrence Seaway Development Corporation. The tugboat operates out of Snug Harbor, on the north shore of the Grasse River, about 1/3 mile from where it joins the St. Lawrence River.
EPA officials said the new tugboat has greater engine power and requires deeper navigational draft than the current tugboat. As a result, Snug Harbor and the channel leading to the harbor from the St. Lawrence River will need to be deepened, with capping as necessary to maintain the protectiveness of the cleanup remedy.
Other activities planned for the season include processing removed materials at the staging area, disposing of materials at the secure landfill on Arconic property, and capping between the Alcoa bridge and Route 131 bridge.
Work is scheduled to be done for 12 hours a day, six days a week. Some capping activities and staging area operations will need to be done 24 hours per day to preserve the work that was completed in 2019.
In 2019, about 100,000 cubic yards of sediment/soil had been removed from near shore areas within the river and floodplain areas. An upland area along the north shore of the river, just upstream from the Alcoa bridge, had been remediated.
In addition, contractors processed dredged material at the staging area and transported it to the secure landfill for disposal; remediated the mouth of a tributary which flows into the river downstream of the Route 131 bridge; placed clean cap material and backfill in the river; and restored the near shore and floodplain areas.
In-river work is expected to be completed in 2021 or 2022, with work starting in the spring and, weather permitting, continuing through November each year.
The purpose of the Grasse River remediation project was to find the best way to eliminate potential risks associated with the lower seven miles of the river that were caused by PCB use at Arconic’s Massena West facility, formerly part of Alcoa Massena West.
Arconic has been working out the details of how the dredging and capping will be carried out, under EPA oversight. The EPA selected a cleanup plan for the lower Grasse River in 2013, calling for the capping of 284 acres of river bottom in the main channel, removal of approximately 109,000 cubic yards of PCB-contaminated sediment from near-shore area, and backfilling of dredged areas with clean material.
Source: NNY 360