By Amena H. Saiyid
The National Park Service has joined environmental groups in urging the Environmental Protection Agency to require effluent limits for ballast water discharges for large ships built prior to January 2009 that ply the Great Lakes.
These groups and the park service say that if the ships are excluded from a requirement in a new vessel general permit to meet discharge limits they may spread invasive species from one part of the ecosystem in the lakes to other areas.
At issue are ships known as lakers, which are 79 feet and longer and only operate in the Great Lakes.
In comments on an EPA draft permit submitted Feb. 21, a coalition of 36 environmental groups acknowledged that lakers do not introduce non-indigenous invasive species. The groups said, however, that the vessels transport those species to portions of the ecosystem wider and faster than they would through the normal process of migration.
Under the five-year draft vessel permit, EPA is proposing to exempt lakers built prior to Jan. 1, 2009 from the requirement to meet technology-based effluent limits for ballast water discharges containing ship-borne pollutants and invasive species, such as the Asian carp and zebra mussels. Ballast water is carried aboard ships in tanks for stability.
Lakers built after that date, and all other ships that are at least 79 feet in length, weigh at least 300 gross tons, and have the capability to discharge at least eight cubic meters of ballast water will have to meet the limits, once the permit is finalized.
All vessels, including lakers, are required to conduct saltwater flushing of ballast water tanks 200 nautical miles from any shore before entering either U.S. waters, including the Great Lakes, or Canadian waters of the St. Lawrence Seaway System.
EPA proposed the draft vessel general permit Oct. 31 and took comments until Feb. 21 on a number of issues, including the exemption for Great Lakes vessels (231 DEN A-14, 12/1/11).
EPA granted the exemption because it said there are no available technologies for ballast water treatment systems to install on these lakers.
The agency estimates 58,602 ships would be covered by the draft permit, but it is unclear how many lakers are affected.
According to EPA, invasive species enter the Great Lakes at the rate of one new species every 28 weeks. The coalition of environmental groups, which include the Alliance for the Great Lakes, the Izaak Walton League of America, and Natural Resources Defense Council, cited a 2010 study in the Canadian Journal of Fish and Aquatic Science that found lakers play a significant role in spreading invasive species after the species have been introduced into the lakes.
The volume of ballast water moved by lakers is 20 times greater than the volume of local ballast transferred by ships plying the coastal waters and oceans combined, “likely rendering lakers the most important ballast-mediated pathway of secondary spread within the Great Lakes,” the study said.
In a Feb. 17 letter to EPA, Gary Rosenlieb, acting chief for the National Park Service's Water Resources Division, raised the possibility of accidental introduction of invasive species.
Rosenlieb said lakers should be required to perform some minimal level of treatment to ballast water to prevent accidental introductions. He noted that scientific literature has documented the transfers of interbasin species. Lakers are built to last 50-70 years, “which may allow for decades of inter basin transfers in the Great Lakes”, Rosenlieb said.
However, the Cleveland, Ohio-based Interlake SteamShip Co. supported EPA's decision to exempt newer lakers from the discharge limits. The company wrote in Feb. 21 comments that EPA based its decision on the conclusion of EPA's Science Advisory Board that the ballast water technologies used on ships plying oceans would not work in freshwater because they rely on salt water to work.
“Simply put, the primary intent of the ballast water related portions of the proposed permit is to stop the introduction of non-indigenous species into the U.S. waters,” Interlake Steamship President Mark Baker wrote. “Because lakers operate exclusively within the Great Lakes, it is impossible for a laker to introduce a non-indigenous species into the Great Lakes.”
Baker dismissed the concerns of the environmental groups that said the lakers are responsible for spreading the invasive species faster than the species would spread through the normal migration. Baker said that lakers have engaged in voluntary best management practices, but the invasive species, once introduced, will spread until they are stopped by a natural predator.
He said the potential benefit of slowing down the spread of invasive species must be weighed against the costs to install, maintain, and operate the systems.
Comments on EPA's draft vessel permit are available at http://www.regulations.gov by searching on Docket ID No. EPA-HQ-OW-2011-0141.
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