A little over two years ago I reported on some small but highly dramatic progress in dismantling the dam infrastructure of the United States. The Army Corps of Engineers, The Tennessee Valley Authority,The Department of Forestry, local electricity entrepreneurs and many others had thrown rock and concrete across the wilder rivers of the country often without adhering to existing laws and regulations to protect wild-life. A pulse-stopping 75,000 such projects have been carried out. On the Blob we've had a few examples of where man's hubris and/or chicanery in material quality have bought a disastrous bargain for people who were sleeping down-river of these engineering projects: Lynn Eigiau - Vajont - not to mention inconveniencing my Portuguese perambulations. At he end of that Dec 2014 piece, I urged you to check out the videos on "Elwha"; but I doubt if anyone obeyed orders so I'll give you a summary here because the river has spilled into Metafilter in the last tuthree days.
The Olympic Pensinsula is a squarish chunk of land about 100km x 100km across Puget Sound from Seattle, WA. It is a sparsely populated wilderness region that was once covered in temperate forest with a light sprinkling of Native North Americans. A little over 100 years ago in 1913, one of several salmon-spawning rivers called the Elwha was damned to provide hydro-electricity for a small town called Port Angeles, paper-pulp mills and a Navy Yard. The competing interests of the fish were 'sorted' by a promise to create a hatchery upriver, so that entrepreneurs didn't have to incorporate a fish-ladder into the dam design. By the time the hatchery conclusively failed to produce any fish, the dam was built and that battle was lost. The demand for electricity is insatiable once the stuff is available and tupenny-ha'penny hydro-plants rapidly get to look small and quaint and wholly inadequate to meet requirements. In 1978, after 65 years of diminishing effective returns, the aging Elwha dam failed a safety inspection. Failing a safety inspection implies the possibility of a catastrophic failure at some thoroughly inconvenient time - Teton Dam - Lynn Eigiau - Vajont anyone?. So something had to be done. Local interests wrestled with the problem all through the 1980s but in 1992 it was decided that the Elwha Dam and the Glines Canyon Dam on the same river should be removed. It took 20 further years to actually start the process ! and a further couple to complete it.
The transition is the most worrying time. The rocks and soil across the river catchment had endured 100 years of rainfall - it rains a lot in the Pacific North-West - frost-heave, glacier-grind, snow-melt and the occasional earthquake. The displaced matter used to wash out to sea, building coastal sand-bars and shoals which supported a particular set of marine wildlife - algae, plants, molluscs, worms and fish. With the fall of the river curtailed, this material had built up into 20 million cu.m. of sediment locked up behind the two dams. The nature of that sediment - % rocks, gravel, sand, mud % organic/inorganic - dictates the method and timescale for the removal of the artificial obstruction. Time-lapse of Glines Canyon piecemeal removal by back-hoe working from topside on a pontoon floating over the abyss <don't look down!>. A rather different more elaborate back-and-forth was deemed to be necessary for the Elwha Dam.
The Elwha restoration project cost a staggering $325million but now it's done and ecologists and fisheries people are documenting the change: counting spawning fish in the head-waters and the build up of beaches at the mouth are only the biggest and most obvious data. I hope humbler scientists are checking on the aerobic and anaerobic bacteria, the nitrogen fixers and the phosphate solublisers: the foundation on which the whole living ecosystem teeters upwards. There's a very nice colour supplement view of the current state of the river by Lynda V Mapes of the Seattle Times. One elegant bit of leverage was to shift the logs that had washed up along the reservoir shores and were now high and drying. Judiciously moving these into the middle of the old lake bed helped to re-create a diverse braided river ecosystem: limiting erosion, sheltering willows and other pioneer plants, shading the fish in the shallows. Tilting the conditions means that you never have to plant anything: create the habitat and the seeds will sprout. For me, it reads like a story of redemption, and I feel a little less ashamed to be a gallumphing human tromping through the world in enormous toxic wellington boots