Details Of Muddy Creek Study

Alliance To Present Details Of Muddy Creek Study Nov. 13

The idea of restoring an old dike to help reduce pollution in Muddy Creek has been on the table since the first analysis of nitrogen pollution along Pleasant Bay more than half a decade ago.

But exactly how converting the upper portion of Muddy Creek from salt to fresh water would impact the existing ecology of the tidal estuary, and whether changes would be worth the trade off of improved water quality, have been two big unknowns standing in the way of getting state regulators to consider the idea.

That will change early next month when a report is released detailing potential resource changes that could happen if the dike is restored. The Pleasant Bay Alliance, which sponsored the report, will hold a public meeting on the study Thursday, Nov. 13, at 7 p.m. at the Chatham Community Center.

“This is the first step, to see if [restoring the dike] has merit,” said Dr. Robert Duncanson, health and environment director in Chatham and head of the technical advisory committee overseeing the town’s wastewater management plan.

“We’re not presupposing a positive or negative here,” said Carole Ridley, coordinator for the Alliance. “We’re just trying to assess what likely changes would occur, if any, and to what extent, if the dike is reinstalled.”

The Massachusetts Estuaries Project concluded that to reach optimal nitrogen levels, 75 percent of the nitrogen load in upper Muddy Creek and 100 percent in lower Muddy Creek would have to be reduced. Muddy Creek runs along the Chatham-Harwich town line, with both town’s sharing the estuary’s watershed. Harwich contributes 75 percent, while Chatham’s share of the watershed is 25 percent. Reports have linked high nitrogen levels in the creek to excessive nitrogen from septic systems. Flushing of the creek is further limited by its long, narrow configuration and culverts beneath Route 28 that separate it from Pleasant Bay.

Chatham’s 2005 Estuaries Report suggests two alternatives for improving water quality in Muddy Creek: increasing the size of the culverts and converting the upper portion from salt to fresh water. The conversion seemed the most likely candidate for success; documents showed an old dike existed about a half mile west of Route 28, and freshwater systems are able to remove, or attenuate, nitrogen fairly efficiently. That would essentially create a freshwater pond in the upper reaches of the creek. The volume of water that flushes through the culverts would be reduced, thus increasing the flushing rate and further helping to mitigate nitrogen loading, Duncanson noted. The Estuaries Report states this could achieve a “significant reduction in total nitrogen in upper Muddy Creek.”

The state, however, places a higher value on marine wetlands than freshwater resources, said Duncanson, and therefore needed to know more details.

“That was part of the conversation we’ve been having with various state regulatory agencies for years,” he said. “They really need to know what’s there and what would happen if the dike is put back.”

With a $35,000 grant from the Cape Cod Water Protection Collaborative’s Shared Watersheds, Shared Responsibilities program, the Alliance hired the School for Marine Science and Technology (SMAST) at UMass-Dartmouth — the same organization that has been working with the state department of environmental protection on the Estuaries Project reports — to conduct the study.

Ridley said the study, which she just received in draft form last Friday, assesses and delineates existing wetlands resources around the creek, “information that did not previous exist in an updated form.” It also assess water quality and details organisms living in the creek and its sediment. That information “tells us what’s there now, what conditions and resources are present,” she said.

“There was a significant amount of field work that occurred over the summer for this,” Ridley said.

The report also evaluates changes in water quality, vegetation and other resources anticipated to occur if a dike is reinstalled.

Exactly when the dike was originally installed is not known. Ridley said licenses for the bike from the state board of harbor and land commissioners exist from 1889 and 1891. Although it’s theorized the dike was washed out in the hurricane of 1938, “we don’t have any definitive information when it was actually in or out,” she said.

Replacing the dike would not eliminate nitrogen loading in the creek, Duncanson said, but it would lower it enough to have a significant impact on how both Chatham and Harwich approach nitrogen reduction in the watershed. Nitrogen may be reduced enough, for instance, so that Chatham doesn’t have to sewer the area, but can instead depend on on-site nitrogen-reducing septic systems.

Because the wetland issues are so significant, from a regulatory point of view, they must be addressed first, he said.

“There are still many unanswered questions,” Duncanson added, including whether creating a freshwater wetland would led to problems with increased phosphorus.

Two key SMAST scientists, Director Dr. Brian Howes and David White, a wetlands scientists, will make the Nov. 13 presentation, Ridley said. It will also be video taped and shown on government cable channels in both Harwich and Chatham.

10/30/08