WASHINGTON — A pair of anti-nuclear groups filed suit Tuesday to block impending construction of a second munitions wharf at Naval Base Kitsap Bangor, a legal challenge they hope will help scrap the $715 million project altogether.

The lawsuit contends the Navy failed to conduct proper environmental reviews and to consider viable alternatives to building a six-acre weapons-handling wharf over the sensitive waters of Hood Canal.

The suit was filed in U.S. District Court in Tacoma by Ground Zero Center for Nonviolent Action, of Poulsbo, Kitsap County, and Washington Physicians for Social Responsibility, of Seattle. By bringing a procedural case under the National Environmental Policy Act (NEPA), the nonprofit groups are aiming to ultimately derail a project they consider a dangerous and unneeded Cold War relic.

Glen Milner, a Lake Forest Park resident and activist, is also a plaintiff. Milner took the Navy to the Supreme Court in another case involving a Freedom of Information request regarding the munitions depot on Indian Island in Jefferson County.

The Navy has said the existing 1970s-era wharf at Bangor lacks capacity to handle ongoing upgrade work on the Trident II D5 ballistic missiles carried aboard the base's eight nuclear submarines.

Leslie Yuenger,a spokeswoman at Bangor, said "the Navy does not comment on on-going litigation."

The second wharf has been chiefly championed in Congress by Rep. Norm Dicks, a Bremerton Democrat whose district includes the naval base. Last month, Dicks helped insert $280 million as second-installment funding in the House version of the 2013 defense-spending bill. That followed $78 million that Congress appropriated for the current fiscal year.

The Navy gave final approval for the project on May 4. Days later, it announced a $331 million construction contract to a joint venture composed of Skanska USA, American Bridge Co. and Nova Group.

The four-year construction is to begin as soon as the Army Corps of Engineers issues permits. The wharf would be south of and adjacent to the existing wharf.

Kathy George, an attorney with Harrison Benis & Spence in Seattle who is representing the plaintiffs, said a central requirement under NEPA is for federal agencies to issue an environmental-impact statement in order to publicly assess any potential harm and possible alternatives.

George, however, contends the Navy didn't seriously consider other options. For instance, the suit alleges, the Navy did not fully explore the possibility of locating the new wharf in Kings Bay, Ga., home of the remaining fleet of six Trident submarines, or operating the existing wharf at Bangor around the clock.

The Navy considered six alternatives to building the second wharf. Five of them dealt with design choices, such as the size of the piles or whether the access trestles should be combined or separated. The Navy dismissed the sixth alternative — making do with the current wharf — by saying that without another wharf it "would not have the required facilities to perform routine operations and upgrades."

Without rigorous assessment, the public and lawmakers "can't be sure the Navy is making the right decision," George said. "It is our contention that the (Navy) did not disclose some of the most critical information."

Bradley Karkkainen, an environmental-law expert at the University of Minnesota Law School, said even if the Navy were found to have violated NEPA, that wouldn't be enough to block the wharf. But the suit could slow down the project and possibly "create a different political climate that could make agencies reconsider."

The Navy's final environmental-impact statement says building the wharf could potentially harm fish and birds, some of which are protected under the Endangered Species Act. They include summer-run chum salmon, Puget Sound chinook salmon and Puget Sound steelhead.

Noise from driving the steel pipe piles, shading from the wharf and air pollution from construction could reduce habitat for eelgrass, interfere with migration of juvenile salmon and potentially injure other marine life.

The Navy has proposed ways to mitigate the impact, such as restricting pile driving to early mornings and late evenings in the breeding season for marbled murrelets.

Kyung Song: 202-662-7455 or ksong@seattletimes.com