To remove or not to remove?5 February 2013
More and more dam removal stories appear to be hitting the headlines in North America every day. However, upon analysis, it appears that dam removal is quite often the last resort for some ageing, obsolete or unsafe structures. IWP&DC gives an insight into recent removals across Canada and the US.
Since 2006, the Canadian province of British Columbia has overseen the removal of 21 dams, some of which were owned by the province and some of which were privately held. 'Dams are most often decommissioned or removed when they no longer meet the needs of the dam owner, and/or when the dam has deteriorated to the point that it is no longer safe, and the cost of repair or replacement exceeds the benefit,' says Brennan Clarke, Public Affairs Officer from the Ministry of Forest, Land and Natural Resource Operations in BC.
Following the failure of Testalinden dam in 2010, BC undertook a review of all dams and identified those that no longer serve their original purpose, and need significant upgrades to meet provincial and national dam safety standards. 'Most of the ones that have been unplugged in the last decade or so fall into that category,' Clarke added.
Four major dams over 9m in height have been removed since 2006. Heber River dam, near Campbell River on Vancouver Island, was removed in 2012 as part of the water use plan for the Campbell River system. The following dams were all removed as the cost for repair or replacement exceeded their benefit:
- Mavis Lake dam in Greater Victoria on Vancouver Island. Removed in 2007.
- Jack Lake dam in Greater Victoria on Vancouver Island. Removed in 2007.
- Upper Greyback dam near Penticton. Removed in 2006.
It was during safety inspections after the Testalinden dam failure that a number of concerns were identified by the ministry at the Providence dam near the southern BC town of Greenwood. Further investigation was warranted.
Standing at 155m long and 9.1m high, Providence dam forms Marshall Lake and the ministry holds two water licences for a total of 3.3Mm3 of storage. Originally built as a wood and timber structure in the 1930s, it was reconstructed as an earthfilled dam in 1961 by the Phoenix Mining Company. In 1966-7 it was reconstructed using rock to its current height of 9.1m to supply water to the now-defunct Phoenix mine which closed in 1976. Since then it has served mainly as a recreational site for residents. It is currently owned by the Okanagan Fisheries Section of Forest, Lands and Natural Resource Operations
After the initial inspection at Providence, a dam safety review was subsequently completed in December 2010 and identified a number of management concerns. Providence is classified as a 'high consequence' rockfilled dam based on the potential for loss of life, substantial economic and social loss, and significant environmental and cultural loss in the event of a dam failure. It does not currently meet provincial dam safety regulations or Canadian Dam Safety Association (CDA) standards. A significant amount of work would be required in order to meet current regulations and ensure public safety.
In early 2011, ministry staff met with officials from the City of Greenwood and gave local government a year to explore the option of transferring the dam licence and liability to local government or the public. The Kootenay Boundary Regional District indicated they were not interested. Staff did not receive a response from the City of Greenwood at that time and in May 2012 ministry staff made another presentation along with a site visit to Marshall Lake. The town formally declined the opportunity to assume responsibility for the dam in July.
Prompted by safety concerns related to the condition of the ageing structure, the decision to decommission the dam was then made and was. Decommissioning is slated for 2013. The water level in the reservoir had already previously been lowered, and will be further lowered later in 2012 to the level of the original lake prior to dam construction. This will alleviate public safety risk as well as the liability and long term maintenance costs to the province. The resulting lake will be 7.7m deep and continue to be stocked with rainbow trout to support a recreational fishery and ecosystem values. The Ministry's Regional Fish and Wildlife staff are preparing to submit a decommissioning plan to the senior dam safety officer. Until the plan is received and approved decommissioning cannot proceed but is anticipated that it will not happen until spring 2013 at the earliest.
Also in the province of BC, Nanaimo City Council is supporting recommendations to remove the 100-year-old Lower and Middle Colliery dams on the Chase River. Engineering assessments concluded that the dams had reached the end of their service life and are currently unstable. Significant earthquake or extreme rainfall events may even cause them to fail.
Having considered all options, including reinforcing or rebuilding the dams, removal of the structures was deemed the safest long-term solution. The target date to commence deconstruction is set for the summer of 2013. Evacuation procedures have also been put in place for residents should the dams fail prior to removal.
Lower and Middle Colliery dams were built by the mining industry in 1911 for the sole purpose of providing water to wash coal. When mining operations ceased the water stores were adopted for recreational purposes only. The City of Nanaimo re-iterated the fact that the dams are not used for general consumption, irrigation, power or flood mitigation.
Illinois Dam Removal Initiative
Governor Pat Quinn of Illinois in the US is moving forward with a major initiative to remove or modify 16 low head dams throughout the state over the next several years. The latest removal centred on the Hofmann dam in late October 2012 under an agreement between the Chicago District of the US Army Corps of Engineers and the Illinois Department of Natural Resources.
The Illinois Dam Removal Initiative has been described by Governor Quinn as an attempt to protect the environment and preserve Illinois' natural resources. Nearly US$10M will be invested to remove 12 dams in Cook County on the Des Plaines and Chicago Rivers, including three that have already been removed: Hofmann, Fairbank and Armitage dams in Riverside.
The removals are being funded through Governor Quinn's Illinois Jobs Now! capital construction programme which began in 2009. Supporting an estimated 439,000 construction jobs, the programme aims to modernise Illinois' infrastructure.
'Removing dams improves water quality, aquatic habitat and recreational safety,' said Illinois Department of Natural Resources Director Marc Miller. 'It also addresses the issue of dealing with crumbling and ageing infrastructure, which would be much more expensive to repair or replace. These dams no longer serve their original purpose and removal or modification will save the state and local communities money in the future.'
Largest dam removal project in California history
In June 2012 the California Public Utilities Commission (CPUC) approved California American Water's request to permanently remove the ageing San Clemente dam from the Carmel River on the Monterey Peninsula. California American Water President Rob MacLean said this was the largest dam removal project in Californian history which will bring numerous benefits to customers, the environment and the public at large.
The Monterey Peninsula is an area which has a semi-arid climate and few year-round water sources. With increasing yearly water demands from the then-burgeoning population and tourism industry, the 32m high concrete arch San Clemente dam was built in 1921 in upper Carmel Valley to supply water. The original reservoir capacity of approximately 1.7Mm3 was essential in the 1930s and for several decades thereafter.
Today however the reservoir is more than 90% filled with sediment and no longer serves an important water supply function. The communities of Monterey Peninsula now get their water from wells in Carmel Valley and Seaside. Furthermore, the structure is no longer in compliance with state seismic safety requirements.
At the time of construction, American Water says that little was known about building for earthquake safety. Between 1980 and 1992, studies were performed to determine the safety of the San Clemente dam in the event of a major earthquake on the nearby Tularcitos fault, or a flood caused by a very large storm. In 1992, the California Department of Water Resources, Division of Safety of Dams (DSOD), required that California American Water as the current owner and operator of the San Clemente dam, upgrade it to comply with modern seismic safety standards. DSOD also ordered interim safety measures be taken, including an annual drawdown of the reservoir, which required drilling holes through the dam to release hydraulic pressure. Work in excess of US$1M was completed, with the first annual draw-down performed in 2003. In addition, various measures to protect the threatened Central Coast steelhead trout and California red-legged frog were implemented, and an evacuation plan for residents downstream of the dam was developed in co-operation with the Monterey County Office of Emergency Services and the Carmel Valley Fire Department.
Since the mid-1990s, multiple engineering and environmental studies have been prepared by California American Water and DSOD to determine what should be done to improve the dam for safety and environmental protection. In December 2007, DSOD certified a Final Environmental Impact Report (FEIR) that analysed potential impacts to geology and soils, hydrology and water resources, water quality, vegetation and wildlife, wetlands, air quality and noise. The FEIR concluded that adding a steel-reinforced layer of concrete to the dam would minimise risk of dam failure in an earthquake or flood, and that installing a state-of-the-art fish ladder would be an environmentally acceptable method to ensure survival of the Carmel River's steelhead trout population. The total cost of this dam strengthening project was estimated at US$50M.
At the request of DSOD, California American Water also commissioned engineering and environmental studies to evaluate the possibility of removing the dam, while retaining the accumulated silt onsite and re-routing the river. The estimated the cost of this alternative project is approximately US$85M.
In January 2010 a formal agreement was reached with California American Water and federal, state and local agencies that provides a framework to co-operatively remove the dam. It enables California American Water to resolve dam safety concerns through the lowest cost solution for ratepayers.
The removal project is unique in its approach because rather than remove the sediment, which would fill 250,000 truckloads, the accumulated sediment will be left in place and located between two new, stabilised, natural, earthen structures. The Carmel River will be re-routed 0.8km to bypass the sediment and as the final step, the dam will be removed. California American Water will donate the 3.76km2 property where the dam is located to the Bureau of Land Management. The project area adjoins two regional parks, creating over 21.8km2 of combined open space available for hiking and recreation.
Groundbreaking on the project will commence later this year and completion is expected in 2015. Benefits of the dam removal will include:
- Providing jobs and local economic stimulus: The project's direct construction expenses of approximately US$62M are projected to result in over US$150M in economic output that will save or generate over 900 jobs. Monterey County has been hard hit by the recession and currently has an unemployment rate of over 12%.
- Permanently improve public safety: Removing the dam will permanently resolve a threat to 1500 structures in the downstream floodplain that are now threatened by dam collapse.
- Facilitate military readiness: The Department of Defence's Innovative Readiness Training (IRT) programme is for military reserve and active-duty forces, and helps them achieve training objectives by participating in civilian projects. Reserve forces could undertake many tasks such as road building, earthmoving, water diversions and removal of the dam. The project presents an excellent opportunity for multi-year, joint training operations.
- A model for western dam removal projects: The San Clemente dam will be one of the largest dams removed in the west. Californian American Water says there is a great opportunity to learn more about post-dam removal sediment transport, channel response, and river restoration processes from studying the outcomes of the project. The project team has invited a group of academic experts to develop a co-ordinated research programme for the project that will help guide all future dam removal projects in the west.
- Restoring connectivity and recovering species: Steelhead along California's central coast is a threatened species. Removing the San Clemente dam will restore access to 40km of spawning and rearing habitat, critical to steelhead recovery. Enabling sediment to move past the dam will also help replenish sand supply to Carmel River beach and dunes, fortifying the beach and coastal area against sea level rise.