Fish Passage on the Pawcatuck River
Chuck Horbert, a Rhode Island Blueways Alliance board member
Long, long ago, in a far-off land (South County), while attending college at the University of Rhode Island, I had an opportunity with fellow members of The Wildlife Society to do an overnight canoe trip down the Pawcatuck River. It was my first trip down this beautiful river, and two things about that experience stick in my mind.
First, I was astounded at the beauty and expanse of Worden Pond and the Great Swamp that make up the headwaters of the Pawcatuck. It was truly like canoeing in a wilderness, with very few signs of human intrusion.
Second, soon after exiting the swamp, was the reality of canoeing in Rhode Island as the world of man emphatically put its stamp on our journey. Starting in Kenyon, over the distance of a little more than a mile, we had to portage the canoes and all of our gear (and beer...it was college) around three separate dams.
First was the Kenyon Dam at Kenyon Mills, which we skirted on the left over a rocky, rooty path. A short distance downstream from there, as we entered the village of Shannock, we had to get around the Horseshoe Dam, also on the left. That walk was easier, but required a scamper across a road. Finally, a little further downstream, we exited river-right by the abandoned, crumbling buildings of Knowles Mill and walked down a road to get around Lower Shannock Falls...but not before seriously considering somehow just canoeing down it. Fortunately common sense prevailed.
It was a tough stretch of river, and our “fun” levels definitely took a hit, but if you think we had it hard, I’m sure you can just imagine how impossible it was for spawning fish to get UPstream. For close to a century, no upstream fish passage was possible above the Stillman Dam in Westerly, Gradually, with the collapse of Stillman, and the breach of a mill raceway that allowed the river to bypass White Rock Dam, and finally, the 1970’s-era construction of a couple fish ladders around two other dams, fish passage improved. But until just recently, the end of the line remained the Lower Shannock Dam.
Conditions on this stretch of the Pawcatuck River have changed dramatically since that long-ago college canoe trip. Starting in 2010 (right after the big floods, in fact), the Wood-Pawcatuck Watershed Association, together with the National Oceanic and Atmospheric Administration Restoration Center, and a whole host of other organizations, implemented three massive fish-passage improvement projects as part of a long-term effort to restore an anadromous fishery to Wordens Pond and many of the smaller tributary watersheds flowing into the Pawcatuck. Each of the dams had its own unique problems, requiring three distinct approaches to providing a means for fish to continue upstream past these obstacles.
Of the three dams, the Lower Shannock Dam was in the worst shape, and since the dam itself was not serving any useful purpose anymore the decision was made to simply remove it. This turned out to be more than a simple matter of removing the dam, however. The channel downstream of the dam had seen its share of alterations, and a series of weirs had to be constructed in it to provide not only enough water for fish to ascend the river during low flows, but also provide resting spots during high flows. A large ledge at the dam site also had to be removed to facilitate passage while still maintaining certain historical features of the former mill. As a result, this section of the river has been converted to a stretch of Class II rapids. These are boatable without any portaging, although a portage path is available, and it is recommended that you scout this tricky section before blasting down it the first time. And keep in mind that high flows could turn this rapid to a more difficult, Class III level rapid. Keep also in mind that as the river upstream of the former dam receded to pre-dam levels, other small drops were revealed. These are generally straightforward and easy to boat through.
Upstream from this project lies the horseshoe dam. For a number of reasons, removal of this dam was not feasible. A number of fish passage options were assessed, and it was decided that the only option that would have a good chance of restoring fish passage was construction of a Denil fish ladder on the river-left abutment. This required quite a bit of excavation of soil and bedrock, and construction of a large concrete structure to house a ladder that would be long enough to supply a gradual enough ramp for anadromous fish to ascend. An eel ladder was also included in the design for the catadromous American Eel.
This project was completed in 2011 and is functional. Of course, boaters still have to portage around the dam, including the same scramble across the road I had to do in college, so be sure to look both ways while carrying around to continue on your way.
Finally, in 2012, the focus was on the Kenyon Dam. Although removal of this dam would have been an ideal option for fish passage, this dam was still being used by Kenyon Industries, particularly for their fire suppression system. Also, removal of this dam would have other significant impacts upstream on many wetland areas, could affect shallow wells, and could induce scour problems on upstream bridges. Construction of a Denil fish ladder would have worked, but would have been difficult, with more complicated long-term maintenance issues.
The chosen alternative was to essentially modify the dam by extending its face downstream, essentially constructing an aquatic staircase downstream approximately 160 feet. A number of rock weirs were constructed across the river channel, with low points to allow of sufficient depth for fish passage during low flow conditions. As a result, what once was impassable to fish and had to be portaged around by boaters is now able to be traversed by both without ever leaving the river channel. If boating through it, scouting is recommended, especially in high water conditions. Under most conditions, it is fairly straightforward.
And more changes are underway now on the Pawcatuck River. In June 2015 a proposal for the removal of the White Rock Dam in Westerly, RI and Stonington, CT was approved by the environmental permitting agencies in Rhode Island and Connecticut and the work is underway now. Removal of this dam will restore river flow to the original channel instead of having most flows go through the former mill raceway. We are living in an age of unprecedented recovery of historical fisheries in this river, so enjoy the ride!