A look at Dam removals: The Science and Policy Approach&The Milltown Dam Superfund site Case Study

UMT 2005

Abstract

Dams in America have caused river systems to be drastically impacted. Species have gone extinct due to the building of dams. In the 1970s Americans became aware of the damages dams have caused. The National Environment Policy Act and the Environmental Quality Improvement Act; started the movement of dam removals. The current method for removing a dam is causing damage to the environment from high levels of sediments in the river. The sediment pollution is the leading problem with dam removals. To restore a river system by removing a dam, models are used to predict the sediment flux the river will experience. With knowing the sediment flux, appropriate management can be performed on the river upstream and down stream of the removal site. Financial risks associated with dam removals needs to be understood to prevent local economies from collapsing, due to the removal. This project seeks to asses the issues associated with dam removals and the use of methods to prevent negative affects. I will use Milltown Dam as an example of how complex dam removals are. The Milltown Dam reservoir contains high amounts of contaminated sediments. The contaminated sediments are the reason for the extensive research of the site. The extensive research will offer great examples for future dam removals.

Introduction      

 Human civilizations have built dams to advance their societies for years, the Romans had aqueducts, the Egyptians had irrigation systems, and the Mayans had a form of plumbing for their cities. During the go-go years of the 1950 and 60’s, dams were being built all around the world at alarming rates in order to support the fast growing economy and population. Ecosystems that were dependent on the free-flowing water source have rapidly diminished. Changes include, spawning behavior of fish, migration patterns of wildlife, and decimation of wetlands. Dams were built to serve a purpose for one sole species, humans, and the ecosystems affected were forced to adapt. Now, in the 21^st century, some dams have lost their functional purpose and humans are calling for their destruction and the restoration of the rivers. Dams are being removed at alarming rates and are having drastic affects on the local ecosystems. It is imperative to understand the science of dam removals to inform policy makers, for the future of our rivers. We need to gain an understanding of the physical and biological processes governing a river system, to better restore the system.       

   Dams are built to support human activity. They create clean power, by converting a rivers' energy into electric power. Reservoirs that form behind dams supply water for irrigation, navigable water ways and recreation. Dams have helped America's economy to thrive. Dams offer stable agriculture, because of the ability to store or release water when in demand. Dams have allowed the chemical and metal industry to grow. The navigable waterways supplied a cheap and efficient way of transporting goods. Dam also protect from flooding events. Dams have drastically altered the landscape of America's rivers. Dams stop the transport of sediments, which cause a drastic change in the geomorphology of the river. Upstream from a dam there is an increase in sediment accumulation along the banks and the bed of the river, downstream from the dam the river is starved of sediments leading to more erosion of the banks and bed. Sediments that are trapped behind dams cause riparian habitats and wetlands to diminish downstream from the dam, and the increase in sediment deposition upstream from the dam may cause habitats to become flooded. Dams dampened the natural high flows and low flows of a river, this effects the temperature chemical composition and shape of the river; ultimately affecting the diverse ecosystem. Most dams in America were built a hundred years ago, and are starting to retire. In the past six hundred years dams have been removed in the United States and a third of them in the past six years (Martin Kaste, 2005).   Dams are being removed for an array of reasons generally for fish passages and safety issues. Dam reservoirs become filled with sediments and no longer function for flood control, storage, and hydroelectric power. The accumulation of sediment behind the dam weakens the structure. Safety issues with dams have been increasing. An independent agency started the Federal Energy Regulatory Commission (FERC), which oversees energy industries, and safety interests of the American public. The FERC oversees infrastructures and asses the safety of the structures. Dam removal projects affect various societal goals such as the health of our environment and economy. It appears that the United States has embraced a trend for the removal of dams; however, it is unclear whether municipalities, scientist, environmental agency, engineers and communities fully understand the various effects dam removal will have. 

Data Sources and Methods      

    For my data I analyzed past dam removals documented in articles. I used these writings to better understand the response to a river system after a dam removal. From the lack of well documented science papers I inferred the importance for the need of dam removal science. I am using the Milltown Dam Superfund site as a case study. The Milltown dam removal site offers a chance to gain information on dam removals in all aspects.      

   Milltown Case Study There are currently many case studies that will add huge amounts of data for the river systems that form after a dam has been removed. The Milltown Dam site is a great opportunity to advance in the science behind dam removals. Due to its vast amount of stakeholders involved, more aspects of the project will analyzed. Milltown Dam was constructed in 1907 for hydroelectric power, below the confluence of the Blackfoot River and the Clark Fork River. It was built downstream from two major mining towns; Butte and Anaconda. In 1908 a major flood caused a mass movement of sediment down the Clark Fork River. These sediments contained high amounts of heavy metals from mine tailings. High floods, ice jams and flows, and earthquakes have affected the safety of the Milltown dam. The dam was built on alluvial deposits, which are not consistent with dam building due to its high ability to erode. Faulting in the area has caused part of the timber crib to become weak. Faulting probably caused the alluvium deposits to settle and erode within and below the dam. The current state of the dam is unsafe consisting of cracks with water flowing through them and large voids within the structure. The FERC assessed Milltown dam as being unsafe and in need of repair. If the dam were to fail 6.6 million tons of contaminated sediments would be washed downstream. North West Energy (NWE) currently owns the dam and is responsible for repairing it or the removal of it.        

  In the case of the Milltown dam, the reservoir and the Clark Fork River have high amounts of heavy metals: such as arsenic, copper, cadmium, lead, zinc and manganese. These metals over time have caused the environment to be devastated.  In 1981 four drinking wells in Bonner (located just above the dam) had levels of arsenic ranging from 220 - 550 µg/l. F In 1983 Milltown dam was listed as a superfund site by the federal government and EPA, decided the dam needs to be removed to clean the arsenic plume in the Milltown Drinking water wells. In 1980 a law was create for industrial pollution cleanup, it required that the corporation that caused the pollution is responsible to pay for the cleanup. It was called the Comprehensive Environmental Response Compensation and Liability Act (CERCLA), which is no longer taxing the industrial corporations leaving the EPA with no leeway for environmental cleanup. The contaminated sediments that are behind the Milltown dam came from Butte and Anaconda mining company, which is currently owned by the Anaconda Mining Co. (ARCO-BP). Arco is responsible for the sediment cleanup; NWE, ARCO, and EPA are in charge of the removal of the dam. This was decided after many different proposals concerning the health of the Clark Fork River and the Bonner aquifer.        

  The Milltown dam will tentatively be removed in the winter of 2007. Also in the case of Milltown's dam the existing reservoir has been a wonderful habitat for Northern pike a very aggressive fish and hopefully with the removal the endangered trout can grow in population. Environmental management issues are very complex and it is imperative for guidelines to be made revolving around dam removals and land management.         

 The Milltown dam Superfund decisions have gone under many reviews. The Butte Anaconda, Milltown Superfund site is currently the biggest in America. There are many people involved with the restoration project and many people studying the process, in relation to society, environment, geology, engineering and politics. The Clark Fork Coalition is a conservation group that is contributing greatly to the advancement of dam removal science and restorative projects. They have scientist, lawyers, and land management advisors working for them. The Clark Fork Coalition has gone through many steps to help mitigate any possible issues that may arise from the removal of the dam and the overall clean up the river. They built a network of individuals that represent an interest in the health of their river. They also organized an outreach program that informs landowners of opportunities and benefits for restoration. They also helped the local economy by setting up marketing programs to help sell their products. They started working with watershed restoration, by providing technical review of funding proposals, design a website and serve on an advisory subcommittee. The Clark Fork Coalition would like the Milltown dam removal plans to include: a more tight look at the copper and arsenic warning limits that would trigger adjustments to the construction work, expand the free arsenic-testing program for domestic wells, create a central web-based repository for all monitoring data as a way to promote agency coordination and public involvement, and make the monitoring plan itself a flexible document that can adapt to changing conditions.      

     The removal; of the dam is going to benefit the long term health of the environment. Removing the sediments allows the Milltown drinking water to be restored and prevent any more pulses of metals down the river from ice scouring. And restorative projects could bring more use to the area. The methods involved with removing the dam doesn’t seem very effective with capturing contaminated sediments from moving downstream. Some of the process include: monitoring for turbidity, and water quality. The sediments that are being removed will be shipped by train to Opportunity ponds where they will be placed over sediments that are incapable of supporting vegetation. The sediments being excavated from the Clark Fork River are high in organic matter, so by placing it on the sediments in Opportunity ponds the sediments will be put to beneficial use. Only a portion of the contaminated sediments is being removed at the Milltown Superfund site, the rest of the sediments will be used to build up the flood plain. The banks will be rip-raped so they won’t be eroded by the river and will be stabilized by vegetation. The problem with this is that the upper Clark Fork River is filled with contaminated sediments. Removing the dam before cleaning the river upstream leaves a chance for more contamination of metals to larger reaches of the river. Due to the complexity of the decision-making for the Milltown Superfund site these issues will be dealt with has they arise. Envirocon was been hired for removing the dam and the sediments; they used models to help understand the river dynamic system and constructed the ideal riverbed model to create after the removal. Possible risks after the removal would be that the channel forms a knick point incision, which increases the rivers ability to erode. Also the arsenic plume in the groundwater in Bonner currently is in equilibrium with its surroundings and the removal of the dam could cause a drastic change it its dynamic and cause a wider area of groundwater to be contaminated. The policy for this issue currently is “dilution is the solution.”  Milltown dam research is currently looking at the ecological risk, associated with the contaminated sediments and the underlying aquifer. The understanding of how the flow of the Milltown aquifer will change due to the removal of the Milltown dam is undetermined. But we do know that the groundwater is forced to move north from the Milltown dam due to the dam blocking its original path west.  Currently it is understood that the aquifer runs north form the Milltown dam then North West and in to the Hellgate canyon aquifer.  The arsenic plume is currently in equilibrium; when the dam is removed the flow could change and cause the arsenic plume to move west towards the Missoula aquifer. The Hellgate Aquifer, Clark Fork River and Rattlesnake River recharge the Missoula valley aquifer. "Isotope and general chemistry do show that the Clark Fork River is well connected to and probably a large source of recharge to the Missoula Valley Aquifer." (Robyn Cook, 2005). To quantify where the Missoula aquifer is recharged is important to determine what effects the removal of the Milltown dam will have on water quality. When the water table is higher there are high concentrations of Arsenic in shallow wells near the river. Deep groundwater trends of arsenic do not follow the arsenic trends in the river; there are few fluctuations in the ground water levels of arsenic (Robyn Cook, 2005). Arsenic is found in the saturated zones, shallow groundwater and the Clark Fork River. This research arise questions of how will the water quality be affected following the removal.   

    Science        

    In recent years, scientists have performed studies on the environmental effects of dam removals and river restoration. Models are used to help understand the complex system; they built model streams to analyze the stream processes in order to mitigate catastrophes caused by the destruction of a dam. Models are computer programs that take many different variables and process them to give outputs. Each model has some constants that apply to empirical data, but all rivers are different, so many different case studies should be used to build the most effective model for stream modeling, after a dam removal. Here are some examples of river systems that are drastically different and expresses the dynamic behavior of river transport systems: Some case studies of dam removals, dealing with large sediment built up are: The Newaygo Dam on the Muskegon River, Michigan was removed in 1969; 40% of stored sediments moved downstream at a rate of 1.6 km a year (Simons and Simons, 1991). The Fort Edward Dam on the Hudson River removed in 1973; 33% of the stored sediments moved downstream within a year of removal, the transported sediments contained PCB's (Shuman, 1995). The Woolen Mills Dam was removed in 1988 in Wisconsin and most of the sediments moved downstream within 6 months, similarly the Oak Street Dam showed a drastic increase of sediments downstream with in two months. In the case of the Elwha River, HEC-6 is being used to predict how much sediment will be moved downstream after the Elwha and Glines Canyon dams are removed.       

   When removing a dam the concern is sediment pollution. Sediment pollution is defined by the river, if the total sediment concentration exceeds the amount the river natural carries, then is considered pollution. Sediment pollution can cause catastrophic floods, fish kills and irrigation problems. Sediment pollution is the leading reason to use river models. A case study for tributary modeling program was done on the Saginaw River using empirical data with modeling data. The researchers set up sediment traps along the river than compared their results with the HEC-6 model and the actual trapped sediment was similar to the models’ trapped sediment. (Baird 1999). Another study was done with the HEC-6 model, the interpreter predicted that after the removal, the bed would aggregate and have flooding downstream within the first two years, form this they decided to raise the height of levees down stream by about a meter. Models are difficult to interpret, depending on who interprets the model; plays a huge role on what happens in removal and restoration process.      

     The lack of peer reviewed articles on the science of rivers after a dam removal is the reason for an increase in models. Dam removal models have been constructed to help predict the time it would take for the river to reestablish its natural flow. The models help scientist understand the possible outcomes of the river, so they can better inform policies makers. The task of today is to develop a base of knowledge for decisions surrounding dam removals. The biggest problem with dam removals is the sediment that is built up behind the dam and the effects on down stream macro and micro invertebrates (Watters, 1999). This has been shown with most dams that have been removed in the past or dams that periodically release mass amounts of sediments down stream. These events were not properly documented, but it is known that mass pulse of sediment down a river can causes ecological problems. For instance fine sediment fills places where fish spawn, or cause the river to become shallow which increases flooding risks and altering the natural course. When a small dam on the Koshkonong Creek in Wisconsin was removed high rates of downstream siltation accrued. The increase in sediment deposits cause mussels to die at high rates. Mortality of mussels was observed 1.7 km below the dam, in 2000 sediment increased by 1.1 % and after three years it increased to 15.9%. The sediment concentrations in the water column were higher downstream form where the reservoir was, this suggest the deaths of the mussels were due to the removal of the dam without removing enough sediments from the reservoir (Sethi, 2004) Another study was performed to examine how an increase in sedimentation affects algal and detrital based stream communities. The study concluded that the addition of sediments had significant effects on the benthic communities, mainly with the macro-consumers. The indirect effects of sedimentation were not as well studied as the direct biotic response, understanding the system of sediment transport can help determine the outcome of a streams ecosystem with an increase in sediment load (Schofield, 2004). In 1999 A small dam was removed on the lower Manatawny Creek. A group performed a study on the river after the removal, of the physical, chemical, and biological responses. They discovered that the increased sediment transport led to drastic changes in the river downstream. The water quality did not change, due to the short hydraulic residence time. After the removal, macro invertebrates and fish shifted from lentic to lotic taxa, and some fish were negatively affected by the increase in sediment (Bushaw-Newton, 2002).    

 Sediment transport models are useful for informing the possible risks associated with dam removals. The most commonly used sediment transport models are: HEC-6, MIKE11, and SED2D. HEC-6 was created by the Army Corp of Engineers as a 1-deminsional model. This model cannot simulate a flood event or complex river networks, to fully model a river network, each section of the river network must be modeled separately. MIKE11 was developed by the Danish Hydraulic Institute; it can be used for water quality modeling, hydrodynamic events and complex river networks. The SED2D is a 2D hydrodynamic sediment transport model that works with RMA2. RMA2 is used to compute the flow field and SED2D is coupled with it to model the sediment transport. The Army Corps of Engineers created this model but due the complexity of the model it is not widely used. On the other hand the HEC-6 model is widely accepted in the states, mainly for its wide acceptance from federal agencies and familiarity to engineers. In the case of Milltown dam they used HEC-6 to model how much contaminated sediments will be washed down stream. Knowing how much contaminated sediments that will be washed down stream is important for planning the best time the dam should be removed. Models are essential to use when there is not empirical data. Science Influences Policy      

     I will outline areas of concern when deciding whether a dam should be removed or restored due to either science or politics. Where a dam is located in the watershed area is very important to consider when assessing the future of a dam. If the dam is at the head waters, it does to have many threats on the fish habitat, and it does not generate very much power due to the lack of hydraulic head. If people live near the dam, what effects would the removal have on their way life? Is the water used for irrigation, recreation, or electricity? Will the removal ultimately affect their livelihood? The age of the dam brings allot of insight to its construction, a fair amount of older dams were built out of wood and are no logger structurally sound. The political and economic issues play a huge role in the action taken with dams. Knowing the original reason for the dams' construction and owner is imperative when assessing for a removal. Other questions to consider:

Ø     Does the dam meet safety standards?

 Ø     Would it be catastrophic if the dam were to fail?

Ø     Does it meet current environmental laws?

 Ø     Will the removal benefit species and what types of species, are they invasive?

Ø     What are the costs associated with the removal?

Ø     What is the current state of the environment with the dam in place?

Ø     What time of the year should the dam be removed, considering the possibility of flooding and fish spawning?

Ø     What are the legal ramifications of the removal process? 

Ø     Does the removal trigger any of the following laws or regulations the Clean Water Act, Endangered Species Act, National Flood Insurance Program, and FERC?

Ø     What type of effect will the removal have upon society, history and culture?

Ø     What are the public involvement and planning issues associated with the dam removal project?

Ø     How will information on the project be communicated to all interested parties?     

 After considering all the issues involved with dam removal, it is best to understand the greatest risks associated with removals. Based upon the case studies it is clear that there are numerous factors for consideration when determining whether a dam should be removed or restored.        

  The highest risks associated with dam removals are ecological disasters. Dams cause dramatic geomorphologic changes to a river altering its natural course. Dams dampen the flow to be relatively constant or much lower than average, by regulating the rivers high flows and low flows, which has effects on the vegetation, animals and micro/macro invertebrates. Some side effects of dam construction have caused wetlands to disappear, fish extinction, vegetation drastically altered and socioeconomic changes. Dams alter the path of fish to there spawning grounds, kill them from water turbines and change the temperature of the water. Wetlands are destroyed by the lack of flooding that once accrued regularly, and lack of or an excess of sediment transport. Vegetation is also altered by the sediment transport system being disrupted and from the change in temperature and water chemistry due to the reservoir. Towns and tribes have been ultimately displaced when there land was flooded from large dam construction. Removal of dams could help bring about a change that could benefit our environment. The risks of dams existing are known and the damage has been great. Restoring the environment is something unknown along with what will happen to an ecosystem that has grown accustomed to the dams. In the case of the Milltown Dam there is a risk of contaminated sediments to affect water quality in stream and in the underlying aquifers. The Milltown dam removal plan might be catastrophic to the Missoula community and the economy related to fishing, therefore understanding the risk is important so policies can be made to mitigate possible damages. The lack of scientific understanding prolongs an efficient way to mitigate such catastrophes.    

      Environmental laws were passed in the 1970's such as the National Environmental Policy Act (NEPA) and the Environmental Quality Improvement Act. They were created to protect the environment from public or private actions. An environmental law is a combination of three things: first is the statute that is passed through Congress. The second is the list of regulations imposed by the Environmental protection Agency in relation to the statute and the third is the legal interpretation of theses regulations by the federal courts in the case of a problem. Some of the laws passed are: the Clean Water Act, Pollution Prevention Act, Toxic Substances Control Act, and the Resource Conservation Act. When deciding a removal some environmental concerns should be addressed, such as the health of the watershed near the site. Many western states have relatively dry climates, and high rates of logging. The combination of dry soils and land disturbance due to logging may cause high rates of erosion in a watershed. If a dam has been in place for a while the river channel below it has shaped to meet the high flows that the dam permits. If once a dam is removed the river channel may see more water during high flows which may cause banks to erode. The increase in sediment to the river may cause many disturbances to the habitats associated with it. The logging debris may now be washed down stream during high flows. It is very important to remove a dam at the opportune time of the year, to avoid possible ecological disasters associated with the high levels of sediment. During the spring fish spawn and need high waters to reach their spawning grounds and un-silted gravels to lay their eggs. Removing the dam before the spring runoff would be a good time, because the high flow will hopefully distribute most of the sediments in large area along the river rather than in a small area. Small dam removals in Wisconsin have had many fish kills due to the time of the dam removal.     

     Many problems arise with socioeconomics, when considering a dam to be removed. Dams that were created for navigable waterways, water storage, or hydroelectric power are being removed. If a dam’s use was to store water and is being removed due to environmental hazards then the community will need to look for alternate water sources. Considering many issues around water shortages, many political steps need to be taken to assure a use of water. The Snake River has many dams on it are under consideration of being removed for salmon runs. The Snake River is widely used for shipping farm goods, without this cheap form of transportation many farmers are facing bankruptcy. Another side affect of removing navigable waterways is an increase in either coal use or oil in transportation, which has an impact on air quality. Many people live next reservoirs and have property that is dependent on the body of water next to it. If the dam was removed their house values would drop, which could cause financial worries to the town. The town could also thrive of water sports and the aesthetics of the reservoir therefore removing it could cause the town to lose huge amounts of economic value. Economic and financial concerns play a key role in most controversies regarding dam removal; there are often many questions about the adequacy and accuracy of benefit-cost analyses prepared in conjecture with decision-making. Some key elements that are not included in the benefit-cost analysis are value of ecological and aesthetic benefits and cost attached to dams and their impoundments versus those with a free-flowing river    (Meier, 2003). Economic issues associated with dam removal decisions are long-term operation and maintenance cost versus removal and financial liability considerations. Potential liability can be serious concerns for dam owners because they are liable for dam failure, personal injury to visitors or trespassers, and potential environmental and property damage caused by dam failure. Dam liability insurance policies are commonly umbrella policies with large deductibles, leaving dam owners exposed to substantial financial risk. The stakeholders involved include the dam owner, shoreline property owners directly affected by any decision, and the community of local interests and governmental interest, and sate agencies and nonresident recreational and environmental interests. All these stakeholders may have different positions in the issue, but varying degrees of salience in the outcome. Understanding the physical and biological processes governing a river system is difficult due to the complexity of the system. It is imperative to understand the relationship between the community and the river system. The lack of peer-reviewed science of dam removals leads to a gap with local community groups becoming involved the process is helped. Dam removal projects have the possibility to drastically alter the ecosystem, economy and environmental policies. The lack of peer-reviewed articles on the science of rivers after a dam removal is becoming a concern. Models are used to help predict the time it would take for the river to reestablish its natural flow. Determining what policies that are needed for dam removals, rely strongly on why a dam should be removed. Safety and liability issues are often the driving factors in the emergence of a potential removal due to the aging of dams. The current environmental laws offer a base for polices to be made upon. The current financial risks of dam removals are great, and it is important to fully asses each dam that is under consideration of removal. Milltown dam has many risks associated with its removal, but with the vast amount of research dealing with the site great knowledge will be gained.