The federal Environmental Protection Agency labeled Hilo Bay "impaired" in 1998. The state's largest watershed, or a land area that drains into a stream, is also one of the most troubled, with bacteria, sediment and nutrient levels exceeding standards.

"It's a hot issue. A lot of groups are expressing concern about the best uses for the bay," said Susan O'Neill, a spokeswoman for the Hilo Bay Watershed Advisory group. "The paddlers, surfers, fishermen, sailors, all use the bay."

Mayor Harry Kim asked the Army Corps of Engineers two years ago to help improve the water quality and circulation of Hilo Bay given concerns degradation was impairing its recreational use.

The corps is currently studying whether removing sections of the breakwater would freshen water flow, and how that might affect circulation and Hilo Bay's ability to function as a port.

The corps plans to examine data being gathered by University of Hawai'i at Hilo researchers before consulting with the state Department of Transportation and Hawaii County about what to do with the breakwater.

The corps stresses no decision about the bay will be made in a vacuum and that the public would be allowed to weigh in.

The Hilo Bay Watershed Advisory group — an organization made up of interested residents — has meanwhile spent more than four years working to understand the waterway and its troubles.

But the group's restoration and protection plan hasn't moved forward because it lacks concrete data to justify specific projects.

According to the group's draft plan finished in 2005, key threats to the bay include: cesspools, lava tube dumping, the breakwater's impact on water circulation, urbanization in flood zones, high rainfall and young geology.

Additional problems include lack of regulations and enforcement, invasive animals, and invasive plants rotting in waterways.

The group recommended restoring the Waiakea Pond wetland, managing invasive species and modifying the breakwater if doing so would improve water circulation.

The group also suggested eliminating cesspools in lava tubes near the Wailuku River and educating the public and government about the need for better sewage disposal.

But experts say so little is known about what's flowing into the bay that it's hard to recommend solutions.

"I have no idea, and neither does anyone with a scientific background, if the nutrients and the sediments in the bay are man-made or natural," said Jeff Zimpfer, a biologist with the Pacific Islands Fish and Wildlife Service, in an e-mail to the Hawaii Tribune-Herald.

He added the unique characteristics of the watershed, including its youth and how wet it is, complicate the analysis.

"It's conceivable even before humans arrived that the bay may not have met state water quality standards as they are written now. So there are no real answers at this point," Zimpfer added.

Steve Skipper, a 29-year veteran of the Natural Resource Conservation Service who advises the watershed group, said the watershed's youth may be playing a role in the bay's high sediment levels.

He said the bay's muddy color may be natural given the area's heavy rainfall and the possible washing down of volcanic dust from Mauna Kea.

Even so, he said surveys should be done to see if runoff from pig farms was flowing into rivers emptying into the bay and to otherwise determine where the dirty water is coming from.

———