Removing WA's Condit dam, recap

A major dam removal project is underway on the White Salmon River in the state of Washington.  Video footage of its breach (made available by National Geographic) shows something few living humans have seen but which is already recur in the near future: the removal of a major dam and associated dewatering of its impoundment.

In 1913, the Northwestern Electric Company built the Condit Hydroelectric Project to provide electricity to a nearby paper company and even to feed Portland, Oregon.  The dam was rated at 14.7 MW of nameplate capacity - a far cry from the Hoover Dam (2080 MW) or Grand Coulee Dam (6809 MW), but nevertheless a major dam in terms of its power production and significance.

In 1996, increasing pressure on dam owner PacifiCorp to install fish ladders and perform modifications for environmental compliance led PacifiCorp to seek the dam's decommissioning and removal.  In 2010, the Federal Energy Regulatory Commission approved the removal of the Condit Dam.  In late 2011, contractors breached the dam, draining the upstream impoundment.

If you haven't seen a dam breach before, or if you are simply impressed by the immense power of moving water, you may appreciate the National Geographic video footage of the Condit Dam's breach and the resulting rush of water and sediment.

Now that the Condit Dam has been removed, remediation and restoration efforts are under way.  You can track those efforts on the Washington State Department of Ecology's website, as well as on PacifiCorp's website.

Maryland dam faces sedimentation threat

In September 2011, Tropical Storm Lee caused flooding in the mid-Atlantic region.  The Susquehanna River rose far above its banks, causing disruptive floods in Pennsylvania and Maryland.  Near the river’s mouth into Chesapeake Bay, massive flooding threatened to breach the 572-megawatt Conowingo Dam.

With its flood gates wide open, the dam survived the flooding.  At peak flows, about 7 million gallons flowed through the dam every minute.  That water transported millions of tons of sediment from the Susquehanna watershed out into the bay, along with large amounts of trash and debris.

The impacts of the flood are still being assessed.  Under typical operations, the dam builds up about 2 million tons of sediment every year, or about two-thirds of the Susquehanna River's total sediment burden.  (Compare the dams currently being removed from the Elwha River in Washington, which had trapped an estimated 24 million cubic yards of sediment.)  Overall, four dams on the Susquehanna might hold up to 280 million tons of sediment.

While Lee removed several years' worth of sediment from the Conowingo Dam, more sediment builds up every year.  The Army Corps is concerned that the Susquehanna River dams have nearly reached their full capacity to hold sediment, and is launching a project to study what could be done, such as sediment dredging or remediation.

February 28, 2011 - dam removal costs and values

Dam removal can bring environmental benefits, but comes with costs.  These costs can include not only the expense of physically breaching the dam and removing its remains, but also costs associated with sampling and remediating contaminated sediments trapped behind the dam.  Here's a quick look at two case studies, providing updates on stories I've noted before.

Last November, I looked at what's trapped behind dams on South Carolina's Twelve Mile Creek near Clemson.  Polychlorinated biphenyls (PCBs) and other chemical contaminants from electronics manufacturing operations have become trapped in sediments behind several dams slated for removal.  Removal of the dams is expected to allow cleaner sediments to flow down into Lake Hartwell where they are hoped to be able to cap the PCB-contaminated lake bottom.  Work on a sediment storage area is now ongoing along Twelve Mile Creek, funded through the $9 million settlement in the enforcement lawsuit against the manufacturer.

Just over a year ago, I noted that a settlement agreement would lead to the removal of four hydro-electric dams on the Klamath River in California and Oregon.  There, utility PacifiCorp has agreed to undertake the dam removal, which is projected to commence in 2020.  Overall, the Klamath Basin Restoration Agreement and Klamath Hydroelectric Settlement Agreement contemplate a dam removal cost of $450 million, with another $1 billion in environmental restoration activities.  How will dam removal be paid for?  At least part of the funds (albeit a relatively small share) will likely come from PacifiCorp's ratepayers.  A California administrative law judge has recommended that the California Public Utilities Commission approve a nine-year 2 percent rate increase to raise $13.8 million for dam removal.   Where the rest of the money will come from, as well as whether U.S. Secretary of the Interior Ken Salazar decides to support dam removal, remains to be seen.

February 15, 2011 - small non-hydro dam removal

From the dam removal department:

Picture a small dam stretching about 50 feet across a stream.  The Gravesleigh Dam on Sackett Brook in Pittsfield, Massachusetts was built in the 1930s by Merle Dixon Graves, a native of Bowdoinham, Maine who served in the Massachusetts House of Representatives from 1921-1924 and who owned Gravesleigh, an estate surrounding the brook just above its confluence with the Housatonic River.  Merle Graves had the dam built to create a small pond for his estate.  Over the years, the pond filled with silt, and much of the Gravesleigh estate became Massachusetts Audubon Society's Canoe Meadows Wildlife Sanctuary.

Now, Massachusetts Audubon is interested in removing the dam for reasons including improving water quality, restoring riparian wildlife habitat, and creating educational opportunities to learn about watershed health and science.  Moreover, as part of a deal to allow the Pittsfield Municipal Airport to expand, the dam site has been identified as able to offset some of the habitat lost at the airport as a condition for state water quality certification.  With the impoundment silted in, and no renewable power production at the site, these benefits may make the Gravesleigh Dam seem like a good candidate for dam removal.

The Housatonic Valley has a long history of industrial manufacturing, some of which resulted in PCB (polychlorinated biphenyl) contamination of the valley's soils and water.  According to EPA, "PCBs are probable human carcinogens and can also cause non-cancer health effects, such as reduced ability to fight infections, low birth weights, and learning problems."  If these chemical contaminants are trapped in the sediment impounded by the Gravesleigh Dam, the dam's removal could send the PCBs downriver into the Housatonic.  This is the same problem as found on Twelve Mile Creek in Clemson, South Carolina, where dam removal initiatives must be weighed against the risk of disturbing PCB-laden sediments.  In Pittsfield, dam removal could be paired with sediment remediation, but that would significantly add to the project's cost - already predicted to be $303,000 without sediment remediation.  This points to the importance of understanding what's trapped behind the dam.

Sampling of impounded sediments was undertaken last summer.  While most samples came back negative for PCB, one of the sediment samples did show PCB contamination.  This triggered another round of sediment testing last month.  The results of that testing have just come in, and suggest that sediment remediation will not be required for dam removal.

The Gravesleigh Dam's saga may soon be over.  In this case, chemical contaminants trapped behind the dam may not prove sufficient to prevent the dam's removal.   Each dam has its own story, and may have its own baggage that must be addressed if the dam is to be removed.  I'll keep you posted on the Sackett Brook story as it continues to flow.

January 10, 2011 - Ballville Dam removal; Lake Erie wind

As many dams in America are approaching their centenary years, dam owners face pressures to maintain or upgrade their infrastructure to comply with safety or environmental regulations - or else face dam removal.  Located outside Fremont, Ohio, the Ballville Dam now faces this choice.

Constructed in 1911, the Ballville Dam was built on the Sandusky River about a dozen miles upstream from Lake Erie to impound and direct water into a downstream hydroelectric station.  The dam is 34.4 feet high and over 300 feet long.  In 1946, the downstream hydroelectric facility ceased generation.  In 1959, the city of Fremont bought the Ballville dam for water supply.  In the ensuing 50 years, issues including upkeep and maintenance costs for the dam led the city to create an alternative reservoir to replace the dam.  The dam has been implicated in fish passage problems, and its removal is anticipated to open up over 22 miles of habitat to gamefish like walleye.  The dam has also been implicated in problems with ice jams above Fremont.  All this, without a revenue stream from the dam, has led Fremont to work towards dam removal.  Fremont has since won approximately $6 million dollars in grant funding to support dam removal, which is slated for summer 2011.


If the dam is removed, large amounts of backed up sediment - including a contaminant burden of heavy metals and polyaromatic hydrocarbons - will either come with it or be swept downstream into Lake Erie.  A report suggests 350,000 cubic meters of sediment may need to be removed to establish the channel of the Sandusky River through the impoundment.  However, the report suggests that the sediment pollutant concentrations are less than or equal to those in existing Lake Erie sediment, and thus that mixing with the lake would dilute any effects.

Interestingly, the Ballville Dam has faced trouble before.  Two years after its construction, the dam failed due to poor anchoring into the sediment, causing serious flooding in Fremont.  Today's dam was rebuilt using a stronger foundation. In 1913, the dam served a useful purpose: supporting the nearby hydroelectric station.  In 2011, without that support for hydroelectric generation, will the Ballville Dam be removed?

Meanwhile, on Lake Erie, the Lake Erie Energy Development Corporation continues to make progress toward the nation's first inland offshore wind development: five wind turbines in state waters about 7 miles off Cleveland.  Great Lakes wind offers many of the advantages of both terrestrial and oceanic wind, while posing other challenges.  Will the Lake Erie project be the first to reach success?

November 23, 2010 - Twelve Mile Creek dam removal?

Whether a dam will be removed can depend on what's trapped behind it.  Dams can trap a lot of sediment behind them, as solids carried downstream in a flowing river fall out into dams' impoundments as the flow backs up behind the dam.  These sediments can add up to a huge volume of material.  For example, on the Elwha River in Washington's Olympic Peninsula, where the Glines Canyon and Elwha dams are being removed, nearly 18 million cubic yards of sediment were trapped above the dams.  That's a whole lot of sediment.  (Picture a large gravel trailer passing you on the highway.  Even if the truck can haul the weight, it's likely carrying less than 100 cubic yards, meaning it would take more than 180,000 truck trips to haul the sediment away.)

Sometimes the sediment trapped behind dams comes with an even heavier burden: toxic contaminants washed downriver from upstream sources.  South Carolina's Twelve Mile Creek provides a vivid example of this hazard.  From from 1955 to 1987, Sangamo Weston, Inc. owned and operated a capacitor manufacturing plant in Pickens, South Carolina.  Waste and effluent including 400,000 pounds of polychlorinated biphenyls (PCBs) made its way (in part through direct discharges) to Town Creek and Twelve Mile Creek, a major tributary of the 56,000 acre Lake Hartwell (where Clemson, South Carolina is located). Sangamo Weston ultimately merged with Schlumberger.  The area is now a Superfund site.

In 2006, a court ordered Schlumberger to take a variety of remedial actions, including paying $9 million in damages and removing two lower dams -- and possibly a third upstream dam owned by the Easley-Central Water District.  It is this dam behind which some of PCB-laden sediments are now trapped.  The question is not as much whether, but rather how much.  Other sediments have made their way down into Lake Hartley; removal of the three dams is expected to allow cleaner sediments to flow down into Lake Hartwell where they are hoped to be able to cap the PCB-contaminated lake bottom.  A study of this dam removal was approved earlier this year, but has yet to commence due to lack of funding.

If and when the dams in question are removed, what will happen to the sediment?  Will it have downstream effects?  PCB contamination can be serious, as seen in the Champlain Hudson Power Express transmission line's route jog to avoid PCB-contaminated sediments in the Hudson River.  Recall that this PCB problem may have been exacerbated by dam removal: the 1970 removal of the Fort Edwards Dam on the Hudson River downstream of PCB-releasing General Electric factories allowed PCB-laden sediment to flow farther and more quickly downstream, resulting in one of the country's largest Superfund sites. By contrast, in Danville, Virginia, where the Brantley Dam is now targeted for removal, studies suggest a small enough volume of sediments (and a low enough toxics load) that dam removal may be feasible without requiring the kind of extensive sediment recovery that may be needed on Twelve Mile Creek.