Muddy Creek Bridge Project Worked

When the narrow culvert connecting Muddy Creek was replaced with the current bridge in 2016, proponents said it was never about the bridge itself; it was about improving tidal flushing in the creek to boost water quality. Water sampling data now shows that the ambitious project achieved just what it set out to do.

 A preview of newly compiled water quality data was shown at last week’s annual meeting of the Friends of Chatham Waterways, showing information gathered by volunteer water watchers at two sampling stations on Muddy Creek. The data was presented as an index of eutrophication, the kind of water quality degradation that occurs when nutrients stimulate excessive plant growth. The prime cause of eutrophication locally is nitrogen from residential septic systems.

 “In 2016, maybe a little bit later, we see a dramatic improvement in water quality, which is very much tied to the Muddy Creek bridge project,” Natural Resources Director Greg Berman told the FCW meeting. 

 On May 5, 2016, state and town officials gathered for a ceremonial ribbon cutting for the new bridge. Prior to that, Route 28 was carried across the river by an earthen dike made from fill carved out of the Chatham hillside by a horse-drawn grader sometime between 1899 and 1903. Narrow culverts in the berm restricted tidal flow, allowing nutrients and other contaminants to accumulate in the creek.

The bridge was no small investment. The total project cost, around $6.47 million, was offset by significant grants secured by the Pleasant Bay Alliance and the towns of Chatham and Harwich, with the two towns’ taxpayers contributing $1.9 million. Dr. Robert Duncanson, then Chatham’s health and environment director — and one of the key architects of the bridge project — said that, over time, the increased tidal flushing under the bridge would wash away a thick layer of organic muck deposited over the better part of a century. Berman said the data validates that vision.

 “That’s something that helps everyone sleep at night. This project did actually improve the water quality in that area,” he said.

Despite the significant improvement, the pollution that took decades to accumulate in the creek hasn’t gone away overnight, said Carole Ridley, coordinator of the Pleasant Bay Alliance.

 “Muddy Creek is a long and winding water body, and water does not move upstream as freely. As a result, the data show a mixed picture in Upper Muddy Creek,” she said. 

That portion of the creek above a former tide gate experiences much less tidal flushing than the part visible from Route 28. Water samples from a station there hint that water quality may be improving, but the progress is not as consistent or significant as shown in the lower station, Ridley said.

 “It is hopefully anticipated that the upper reaches of Muddy Creek will continue to improve as flushing of sediments and transition of vegetation continues to occur,” Berman said.

The creek, inland of the bridge, is closed to shellfishing year-round, while the area near Jackknife Harbor is open for seasonal shellfish harvesting when water quality standards are met, Chatham Shellfish Constable Renee Gagne said. 

 “The measure for shellfish growing areas is fecal coliform, which may be influenced by natural sources such as birds and wildlife,” she said. “So despite water quality improvement, the areas west of the bridge may still not meet the national standard for reclassifying.” Without state water testing happening there, it’s impossible to know whether that part of the creek might be able to sustain shellfish that could be harvested, Gagne said.

But that doesn’t mean that the bridge project hasn’t paid dividends. In Harwich, the bridge project was a key part of the town’s wastewater management plan.

 “This had the effect of reducing the total area of sewering that is needed to meet water quality thresholds, as compared to conditions with the former dike in place,” Ridley said. In Chatham, which opted early on to sewer the entire town, the bridge still is expected to help the town meet its nitrogen-limiting requirements on time or possibly ahead of schedule, Berman said.

On Sept. 5, Duncanson will be the keynote speaker in an event sponsored by Pleasant Bay Community Boating and the Friends of Chatham Waterways. He is expected to review the results of nearly a quarter-century’s worth of water sampling data and what that data shows about water quality initiatives. For more information about the event, email curranj@pbcb.cc.