After the Rapidan Dam mess, a call for river restoration

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As we all watched news video of Rapidan Dam being rendered inoperable by recent torrential rains, we were left wondering: “So what should we do now?”

Much of the news has focused on the spectacle of the dam failing and the human story of the adjacent Dam Store and loss of a family’s history. But there is more to this story. The ongoing, long-term cost of this century-old dam on that river system, upstream and downstream, is much broader and greater than is often realized. Removal of the dam and restoration of the river has been formally evaluated since 1979. With the dam failed and obvious technical risks of a dam at this site, it is time to move forward with this alternative and restore important ecological functions of the Blue Earth River.

Dam removal has proven to be the most effective way to restore native fish and mussel communities across entire watersheds. Rapidan Dam blocked migrations of native fish and mussel species from 96 miles of the Blue Earth river and 1,200 miles of connected tributary streams in the Blue Earth Watershed resulting in substantial decrease in upstream biodiversity. Twenty-five species of fish found in the Blue Earth River are abruptly absent upstream of the dam. In the adjacent Cottonwood River, removal of the Flandrau Dam resulted in the upstream return of 26 of the 27 missing native fish species in the watershed. Only 10 of 24 native mussel species historically found upstream of the Rapidan Dam remain, with the rest only observed as dead shells. Removal of the Appleton Dam on the Pomme de Terre River allowed host fish to return, and several native mussel species recolonized the upstream river. Mussels improve water quality by filtering nutrients, removing harmful bacteria and stabilizing stream beds.

With the dam removed and the river restored, the Blue Earth watershed and its tributaries would be reconnected for migratory fish species, restoring the rapids that gave Rapidan its name and critical spawning habitat for sturgeon, walleye and other species. Up to seven miles of the river would be freed from sedimentation and backwater effects of the dam. Also, 368 acres of native plant communities would be re-established, and trails and access points could be developed providing opportunities for viewing, hiking, kayaking or canoeing in and along aesthetic rapids.

A removal option outlined in a 2000 report and again in 2021 would have stabilized or removed sediments to prevent their catastrophic release as has recently occurred. Since the dam has failed, and much of the stored sediment in the reservoir has already been washed out and the river is actively restoring the river channel, previous cost estimates for river restoration will decrease substantially. Current river restoration may be as simple as removing the dam structure, which in 2021 was estimated at $10 million.

In essence, there are only two active decisions to consider at this point: restore the river and the rapids that the dam inundated or rebuilding a dam that had lost its function and was expensive to maintain. Beginning in 1997, and again in 2000 and 2021, the river restoration option has been formally studied and presented to the owners.

Recently, the river cut a new channel around the dam and changed this narrative. The estimated cost of removal continues to go down as sediment gets flushed out and concerns about the upstream bridge pilings eroding now apply to each option. Meanwhile the initial cost of rebuilding the dam is rapidly going up as the gorge gets larger and as sediment and the embankment is swept downstream.

The weak sandstone has proven to be an unsafe foundation for a dam of this size. Careful examination of the breadth of facts and issues connected with this dam should dissuade additional expenditures for rebuilding Rapidan Dam. Removing the dam and restoring the river is a better long-term solution.

Ian Chisholm lives in St. Paul. Luther Aadland lives in Fergus Falls, Minn.