EAST PROVIDENCE — The United States Army Corps of Engineers, in conjunction with state and local officials as well as area non-profits, recently continued its long-running effort to assist herring migration on the Ten Mile River in city.

At the Corps’ request, Rhode Island Department of Environmental Management personnel along with members of the The Nature Conservancy Rhode Island Chapter and the Ten Mile River Watershed Council, last week, constructed temporary structures in the river using sand filled super sacks and sandbags to aide fish who still struggle to pass an exposed ledge below the ladder installed at Hunts Mills. The exercise is serving as a physical model to determine if the Corps’ computer simulation would actually be effective.

A special, long-arm excavator was used to put 30 sand-filled super sacks, weighing 3,400 pounds apiece, into position over two days in early August to help create four pools, each placed about six inches lower than the previous one.

According to the TNC, river herring are an important food source for ospreys, bluefish and striped bass. Engineers will use this physical model to design permanent weirs so fish can reach the ladder more efficiently. They will measure the resulting flow downstream and compare it to the swimming speed of river herring. Temporary weirs will be left in place through the spring 2021 herring run to see how fish interact with the new structures at Hunts Mills.

Spring flows on the Ten Mile River have to be just right for river herring to get by a natural obstruction at Hunts Mills. At high water, fish are pushed back; at low flows, a 3-foot bedrock ledge is exposed—too tall for the herring to swim over. The addition of stone or concrete weirs would create a series of pools to calm the river and submerge the outcrop, allowing fish to ascend a watery staircase. But the river’s rocky and irregular bottom is difficult to replicate in a computer model, so before pouring concrete the decision was made to conduct a test using the super sacks.

The project at Hunts Mills cost $53,000 and will enhance a $7.7 million investment in the Ten Mile River, led by the U.S. Army Corps of Engineers, RIDEM, the City of East Providence and Save The Bay. The original fish ladder was installed some 10 years ago.

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