The abandoned plan for a dam and reservoir at Big Bottom has been discussed here before, but did you know that other major dams were once considered as possibilities on both the Clackamas and Collawash rivers? Potential projects were considered decades ago that could have resulted in dams at Big Cliff, Three Lynx and Austin Point. Smaller pumped-storage projects (with penstocks connecting them to reservoirs on the rivers below) were considered for sites on Lowe Creek, Pinhead Creek, Cottonwood Meadows and Elk Lake, as well as a high spot above Big Eddy. The locations of each of these is described in a 1980 USGS report "Appraisal of Waterpower Potential, Clackamas River Basin" https://pubs.usgs.gov/of/1980/1276/report.pdf
To satisfy my own curiosity about these proposals, I drew outlines of most of them on the map below. The lines are only roughly drawn approximations (based on the elevations given in the USGS report) but at least they give an idea of the extent of the inundation that could have occurred.
It's unlikely (I hope!) that any of these would be seriously considered these days. I am posting this information for historical interest, to show what might have happened if any or all of these projects had actually been built. It could have been a whole different world out there with big reservoirs, relocated roads, and more powerlines.
Here are larger-scale maps of individual projects:
South Fork dam and reservoir
Nowhere Creek dam and reservoir
Austin Point dam and reservoir
Smaller pumped-storage sites with penstocks connecting them to reservoirs on the river below:
Lowe Creek below Tarzan Springs
Pumped-storage projects were also considered at Elk Lake, which would have flooded the existing lake to create a larger reservoir and created a dam and reservoir on the Breitenbush River; on an unnamed tributary of Pinhead Creek; and at a site atop a hill above Big Eddy. I didn't map these, except to crudely estimate the Big Eddy site, because the descriptions were too vague.
Dodged that bullet, didn't we? Great article, maps and research. In a quick read of the USGS report I get that additional power generation is not needed for local use and the report is a sort of 'what if' analysis.
I'd actively join the protest should some agency be dumb enough to actually try to implement one of these dams.
These project failed long ago due to economics, not because of the environmental damage they would undoubtedly cause. When the Bonneville Power Administration began operating the big dams on the Columbia, they started selling power for less than these comparatively small Clackamas River projects needed to turn a profit - despite the fact that some of the work for them had already been done. Even if by some miracle that fact changes, these projects face environmental restrictions that likely would prevent them from moving forward. At the time of the initial proposals, no modern environmental law existed.
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