Dear Editor, In ‘To dam or not to dam?’ (IWP&DC, July 2000) Kader Asmal, chairman of the World Commission on Dams, connected some news headlines to imply a dam removal trend in California.
I immediately recognised that ‘Bureau of Reclamation to undo US$1.5B multipurpose Auburn dam’, referred to proposed legislation to plug an open diversion tunnel 20 years after construction of the dam was stopped and that, ‘Ventura County, State and Federal governments jointly start what may be the largest removal project in history at the 58m Matilija dam’, referred to consideration of complete removal of an arch dam, cracked by alkali-silica reaction, that has periodically been notched for the last 40 years to improve its safety by reducing reservoir load and storage (see Civil Engineering, December 2000).
The rest of the headlines cited by Asmal dealt with removal of small dams. Small dam removal is but one of many actions being taken in the long term effort to restore and enhance our central valley fishery. The fishery has long been damaged by a wide variety of factors from acid mine waste and pesticide discharges to pumping up the 470cms from the Sacramento-San Joaquin rivers delta to over-fishing.
I did some research to try to put the removals in prospective. Information on dams in California is easy to find since the state has regulated dams for safety since 1929. Owners must file applications and receive approvals to construct, modify or remove dams that impound more than 18,000m3, impound 18,000-62,000m3 and are higher than 8m or impound more than 62,000m3 and are higher than 3m. Over 1200 dams are currently regulated. I found that 14 regulated dams had been removed in the last 33 years; the majority were industrial plant dams at operations that closed. None of nine cited by Asmal were listed, because they are too small to be regulated.
Attempting to project a dam removal trend by connecting proposed legislation to plug an unused diversion tunnel, and a study of continuing the removal of a dam and removal of dams that are too small to be regulated for safety is at best ‘bad science’. The result becomes absurd when one considers that southern California’s surface water storage capacity was almost doubled by the completion of the 1010M m3 Diamond Valley Lake (IWP&DC, June 1995) and the 168m high Seven Oaks dam completed on the Santa Ana river, in the previous year.
Donald H Babbitt Sacramento, CA, US