The selection of an appropriate sediment remedy directly affects the welfare of the community whose environment, public health, and economy may have been affected by sediment contamination. At many sites, a simple risk reduction may not be sufficient to protect human health and the environment because sites must also comply with the full complement of water law and public trust principles in order to maintain a sustainable and productive resource. The relationship between remedial technologies and the laws and regulations that apply to sediment sites can complicate site cleanup. Both stakeholders and regulated parties should understand the technologies and the regulations in order to select remedies that are acceptable to all who share water resources. This understanding is of special importance for tribal lands because additional tribal agreements must be considered when developing sediment cleanup RAOs for habitat and watershed use.
A sediment remedy must protect public resources for all who depend on these resources. Clean sediments provide the base for regional ecosystems that supply food to aquatic organisms, wildlife, and people. A clean sediment environment is equally important for economic, recreational, and subsistence fishing for tribal and community health. Significant stakeholderAffected tribes, community members, members of environmental and community advocacy groups, and local governments. and tribal concerns exist that are unique to contaminated sediment remediationThe act or process of abating, cleaning up, containing, or removing a substance (usually hazardous or infectious) from an environment. because of these effects on surface water and sediment resources. Communicating with stakeholders early in the remedial process helps to develop a shared, resource-driven discussion and form a cooperative basis for remedy selection and implementation.
Under the Public Trust Doctrine (PTD), state governments must manage and protect certain natural resources for the sole benefit of their citizens, both current and future. The National Pollutant Discharge Elimination System (NPDES) is one of many examples of how the science behind watershed management works to achieve the goals and principles that form the basis of the PTD model for protection and management of water resources. The science that drives watershed management principles for multiple sources of contaminated sediment is similar to that for setting limits on chemical discharges from municipal or industrial treatment plants. The cumulative effect of sediment sources of contamination in the watershed can have the same detrimental effect as too much loading from municipal or industrial facilities, and thus should be managed using similar principles.
Much of the world’s population lives in or near watersheds, and thus is affected by the sustainability of these watersheds. In a 2000 report, the World Resources Institute stated the following: “…in 1995, over 2.2 billion people—39 percent of the world’s population—lived within 100 km of a coast, an increase from 2 billion people in 1990. The coastal area accounts for only 20 percent of all land area” (WRI 2000). According to 2002 data from the National Oceanic and Atmospheric Administration, over 50% of people in the United States live within 50 miles of an ocean or Great Lake. Clearly, major population centers at risk of food chain exposure from bioaccumulatives, endocrine disruptorsEndocrine disruptors are chemicals that may interfere with the body’s endocrine system and produce adverse developmental, reproductive, neurological, and immune effects in both humans and wildlife. A wide range of substances, both natural and artificial, are thought to cause endocrine disruption, including pharmaceuticals, dioxin and dioxin-like compounds, polychlorinated biphenyls, DDT and other pesticides, and plasticizers such as bisphenol A. Endocrine disruptors may be found in many everyday products– including plastic bottles, metal food cans, detergents, flame retardants, food, toys, cosmetics, and pesticides. The NIEHS supports studies to determine whether exposure to endocrine disruptors may result in human health effects including lowered fertility and an increased incidence of endometriosis and some cancers. Research shows that endocrine disruptors may pose the greatest risk during prenatal and early postnatal development when organ and neural systems are forming. http://www.niehs.nih.gov/health/topics/agents/endocrine/, and other risks are in proximity to surface waters, and by association, sediment sites. Sediment sites are often literally in the backyards of stakeholders and, because of the relatively high mobility of sediments and some contaminants, these sites may expand farther downstream into other larger watersheds and into more accessible private and public property resources.
Management of these public resources has always been in the public trust arena; however, this public trust is not always recognized as the foundation of management decisions for specific sites. Therefore, oversight agencies, as well as the responsible party facilitating the cleanup, must conduct the remedial investigation, development of RAOs, FS, and remedy selection and design with the public resource concept at the core of decision making. This approach reminds both the regulated community and the interested stakeholders that they are operating under a complement of existing laws clearly designed and developed for the welfare of the public.
Many general stakeholder concerns are also relevant to tribal lands and water resources. Tribal lands include the reservation land base as well as ceded and usual and accustomed areas (CUAAs), which are lands that are co-managed under both tribal and federal jurisdiction based on court decisions and cooperative agreements. The natural resource base of tribal and CUAA lands is about 135 million acres, or almost 211,000 square miles. This area contains more than 730,000 acres of lakes and reservoirs and over 10,000 miles of streams and rivers. Numerous treaties between the U.S. government and Native American tribes guarantee complete sovereignty to the tribes for these lands and natural resources. Currently, many tribes are asserting their treaty rights to manage their fish and wildlife resources, but most tribes lack the funding and human resources necessary to adequately manage these resources.
Generally, both statutory and tribal management practices require a watershed and regional perspective to manage the resources for the benefit of those who use the resources. The welfare and protection of water resources from a state and national perspective are considered a matter of public trust. The PTD holds that these resources should be sustained and made available for current and future generations. The Native American perspective toward contaminated sediment remediation varies among tribes depending on their location, climate, natural resources, and culture. Certain central tenets, however, hold true across all tribal lands in regard to pollution of natural resources. Native American cultural and spiritual values pertaining to the environment differ from those of mainstream U.S. society. Clean water and unpolluted waterways are of paramount importance to tribal societies, especially those that depend on subsistence fishing and hunting. Even in tribes that are not subsistence societies, a clean natural environment is considered a sacred responsibility and held in highest honor.
Contaminated sediments have the potential to damage public and tribal resources, thus regional watershed management is an integral part of sediment remedy selection discussions with stakeholders and regulators. Multiple sediment site effects on the health of local or regional watersheds are a component of decisions, because the entire resource may be held in public trust or tribal sacredness. These concerns align with the concerns of stakeholders who wish to protect these resources for current and future use. The PTD and regulations for management of resources for the benefit of the citizens are based on the same principle: to protect the public health and environment for the good of the citizens and to sustain resources for future generations.
Significant national economic interests rely on aquatic resources that may be affected by contaminated sediments. As a result, recreational opportunities, cultural issues, property values, tribal fishing rights and treaties, reproductive habitatAn environment where reproduction can occur, usually expressed as species specific., and regional economies based on consumption of noncontaminated freshwater and saltwater species become important stakeholder concerns.
Because of their mobility, contaminated sediment sites are in the public resource arena and should be addressed on a regional basis, especially if bioaccumulatives and endocrine disruptors are present in the food chain and watershed. The release of bioaccumulatives and endocrine disruptors to the environment through long-term leachingLeaching is the extraction of certain materials from a carrier into a liquid; usually, but not always, a solvent. from contaminated sediment can affect the health of those using the watershed. The cost of chronic health care issues and potential birth defects due to these compounds must be discussed with stakeholders. Sediment cleanup to levels that are developed to protect human health and the environment when these compounds are present will directly affect the selection of an appropriate remedial technology and its associated costs.
Costs are also associated with only addressing risk, while not improving habitat, restoring recreational opportunities, or expediting the elimination of fish advisories for bioaccumulatives from entire regions. The Great Lakes hold 22% of the world’s fresh water resources, and currently fish consumption advisories are placed on all five of the Great Lakes. The same endocrine disruptors and bioaccumulative substances that have resulted in the Great Lakes advisories also exist in Gulf Coast estuaries, many coastal and inland wetlands, regional watershed ecosystems such as the Chesapeake Bay, and many inland lakes and streams that feed the tributaries that discharge to the East, West, and Gulf Coasts.
Risks associated with contaminated sediments differ from risks that can be controlled on private upland industrial property or public property. Upland sites can often be visually monitored through frequent inspections. Many of the chemicals in sediment, however, are soluble (and therefore mobile) and subject to extreme drought and weather events that flood, dry, and eventually redistribute the contaminants. The physical setting, the science of short- and long-term contaminant transport, and the sediment mobility make visual monitoring cost prohibitive or technically impossible for most sediment sites.
Risk management is more challenging in sediments than at upland sites. Engineering and design assumptions may not always account for the effects of extreme storm events and drought conditions followed by flooding, which can completely or partially redistribute massive quantities of contamination. Redistribution of chemicals buried at depth and thus assumed to be in a stable environment are of greater concern under these conditions.
The cost of sediment remediation to federal, state, and local governments and tribes who also have obligations to fund human health and social mandates is a concern to stakeholders. These direct needs must be balanced with the quality of life and health of the regional population and environment that are affected by the contaminated site. Government and tribal entities fund cleanup of contamination that has become their obligation due to bankruptcy, default, or poor environmental practices from the past century. These legacy problems are difficult because it is sometimes impossible to determine which parties are responsible for the contamination.
Native American tribes vary widely in their ability to finance and manage environmental programs. For example, one tribal nation in the southeast United States is aware of lead and mercury contamination in their riparian and lake sediments, but does not have funds to conduct a site characterization and develop baseline data, much less to undertake remediation. Conversely, a large tribal nation in the southwest United States has a fully staffed Division of Natural Resources within its tribal government. Yet another tribal federation in northeast United States had the resources to use stable isotope analysis to identify a near-by smelter as the source of contamination of tribal water resources and sediments and is negotiating with the smelter for future remedial action.
Most tribes desire to be good stewards of the environment, but realize that financial resources for such efforts are scarce. Because a high percentage of reservation inhabitants live below the poverty line, many tribal governments fund health and social services as their highest priority and then struggle to find funds for other programs such as sediment remediation. Grant money, although helpful for short-term projects, does not provide the long-term support necessary to develop environmental programs and to retain a trained technical staff. Consequently, more costly technologies to remediate contaminated sediments are not likely to be used extensively on most tribal lands. Another challenge is the difficulty in obtaining access to some tribal lands for making improvements.
Aquatic habitat restoration is a component of remedy discussions that should occur with stakeholders and tribes prior to any decision involving a remediation technology. Preventing destruction and maintaining habitat for both terrestrial and aquatic environments are important from a regulatory as well as stakeholder perspective. This concern is not always adequately represented by resource agencies that may invoke natural resource damages claims. Stakeholders should be apprised of these discussions before remedial decisions are made in order to be certain that their concerns for local and regional watersheds are represented.
The need for habitat restoration is based upon strong supporting scientific research and restoration is usually supported by stakeholders. Each technology in this guidance should be presented to the stakeholders to assess restoration benefits and then evaluated by the stakeholders to determine how effective the technology will be with respect to restoration of habitat. These discussions should occur with stakeholders when developing RAOs, as well as during the remedy selection process.
The nation’s fisheries and aquatic-based environment depend on the high-quality sediment resources necessary to provide healthy populations of aquatic organisms that support the food chain—the foundation of the regional ecosystem. Restoration and sustainability of the hyporheic zoneThe hyporheic zone is an active ecotone between the surface stream and groundwater. Exchanges of water, nutrients, and organic matter occur in response to variations in discharge and bed topography and porosity. Upwelling subsurface water supplies stream organisms with nutrients while downwelling stream water provides dissolved oxygen and organic matter to microbes and invertebrates in the hyporheic zone. Dynamic gradients exist at all scales and vary temporally. At the microscale, gradients in redox potential control chemical and microbially mediated nutrient transformations occurring on particle surfaces. (see Section 8.5) are necessary to maintain critical habitat and to sustain the health of the entire watershed (see Ground Water and Surface Water: A Single Resource, USGS 1998). The hyporheic zone often is the base for entire aquatic ecosystems in watersheds that have interaction with groundwater and surface water. The value of remedial activities for this zone should also be communicated to stakeholders early in the decision-making process.
The habitat generated by the interaction of saltwater, brackish water, and freshwater in the rivers and estuaries of the Gulf, East, and Pacific coasts are essential for species that reside in these ecosystems. Thus restoration and preservation of this zone of interaction is of great importance. Most, if not all, of the geochemical and biological characteristics of these zones are necessary to maintain the habitat, spawning and fisheries health, and the aquatic and terrestrial ecosystems.
Although habitat restoration is important, responsible parties may only be responsible for areas that they have affected, and complete restoration may not always be achievable. Stakeholders should be made aware of what is realistic and achievable in the context of the individual cleanup. Larger watershed issues should be discussed with other resource protection agencies that are part of the process in order to integrate site-specific cleanup into the larger watershed management during the remedy selection process.
The hyporheic zone is defined as a subsurface volume of sediment and porous space adjacent to a stream, river, or lake through which surface water readily exchanges with groundwater. Although the hyporheic zone physically is defined by the hydrology of a body of water and its surrounding environment, it strongly influences the ecosystem of the water body, biogeochemical cycling, and water temperatures. A functioning and intact hyporheic zone provides the biological and geochemical environment for success in many monitored natural recovery remedies that do not involve persistent bioaccumulative organic compounds. For additional information regarding the hyporheic zone and surface water interactions in groundwater/surface water transition zones in ecological risk assessments, see Evaluating Ground-Water/Surface-Water Transition Zones in Ecological Risk Assessments (USEPA 2008b).
A hyporheic zone that no longer functions due to sediment contamination can impair or even prevent this zone from geochemically processing waste and providing habitat for aquatic insects, vegetation, and spawning beds for fish and other critical species. Sediment cleanup can act as a catalyst to bring parties together in order to consider larger watershed issues that may need to be addressed. A collaborative model for watershed management issues as well as sediment cleanup is a means to bring these issues forward.
The Great Lakes watershed offers an example of the regional issues and approaches often relevant to stakeholders for contaminated sites. The Great Lakes regional population dynamics are summarized as follows:
- 25% of U.S. cities with over 100,000 residents live within 100 miles (160 km) of a Great Lakes port.
- 29% of the U.S. population resides in the region.
- 30% of U.S. personal income is distributed in the eight Great Lakes states.
- 31% of the U.S. population over 65 resides in the eight Great Lakes states.
These figures pertain to the U.S. side of the border, but they are comparable for the Canadian portion of the region as well.
Groundwater in the Great Lakes watershed provides the base flow for rivers, lakes, and streams and is the origin of most surface water in Lakes Michigan, Superior, and Huron and, to a lesser degree, Erie and Ontario. This means the vast majority of water in the upper Great Lakes watershed must pass through sediment prior to becoming surface water in the Great Lakes. In Lake Michigan alone, 78% of the water interacts with sediment prior to becoming surface water. Long-term, low concentration, leaching of bioaccumulative compounds from sediments in tributaries affect Lake Michigan. These compounds may circulate in the lake for a century before moving into Lake Huron, remain there for a significant period of time, and then pass on to Lakes Erie and Ontario (USEPA 2012b)
Bioaccumulative substances can have extremely low solubility and are stable compounds known to persist for long periods of time. Continuous interaction with water can leach these substances at their limits of solubility into bodies of water that sustain the Great Lakes or, on a national level, estuaries and oceanic coastal environments where commercial and recreational fisheries and critical ecosystems are located. These substances can exist in or below the BAZ and pose a long-term risk to the watershed while not necessarily demonstrating a risk on a site-specific area. This concern is most critical where groundwater and surface water interact continuously or there is a tidal ebb and flow that continually flushes the sediments in the tidal basins.
In any watershed, continuous groundwater and surface water interaction may cause mobilization of the bioaccumulative compound at the limits of solubility in the dissolved-phase into surface water. These phenomena may not be significant to local watersheds since low dissolved endocrine disruptor levels are not generally considered to be biologically available. However, the long-term leaching to a body of water such as a Great Lake with a long residence time is likely transferring the chemical to a regional watershed where it may reside for hundreds of years.
Other contaminant transport processes may be site-specific such as spring action and erosion of deeper sediments that mobilize colloidal and particulate matter saturated with these compounds. These long-term contaminant processes take on a much greater significance in the Great Lakes watershed where the rate of flushing of the system is approximately 191 years for Lake Superior and 99 years for Lake Michigan. Cyclical fluctuations in the Great Lakes, often many feet, do not allow for long periods of sediment accumulation to bury the affected sediment below the BAZ. Shallow mud flats can extend for significant distances. Other fine-grained deposits may reside for several years off shore before being redistributed once again by waves as the lake fluctuates in level. Large amounts of sediment and any associated chemicals may be redistributed with each cyclical event.
Based on these watershed dynamics, the vast majority of water in the upper Great Lakes watershed must pass through sediment prior to becoming Great Lakes surface water. The long-term fate of very low solubility bioaccumulative substances discharged to a Great Lake is a concern to stakeholders, because the residence time for those compounds can be hundreds of years to flush through all five lakes. The long-term fate and transport of bioaccumulative substances and endocrine disruptors in systems having continuous flushing with groundwater or tidal influences requires careful evaluation when recommending that significant quantities of these compounds be allowed to remain in the watershed for an MNR or EMNR remedy.
Evaluating all sites from a regional or larger watershed management viewpoint could be part of the decision process because the cumulative impact of multiple sites in a watershed can seriously impair the regional aquatic ecosystem as well as human health, especially with respect to bioaccumulative and endocrine disruptor compounds. Sediments, of course, are not the only sources of bioaccumulatives deposition into the Great Lakes system since aerial deposition from rain and particulates is also of concern. The fish consumption advisories for the entire Great Lakes region are, in part, due to the cumulative impact of multiple sources in the watershed. Ongoing work at the various Great Lakes Areas of Concern will go a long way towards ultimately lifting those advisories.
Publication Date: August 2014