State of the Lakes Ecosystem Conference
SOLEC '96 Paper on Changing Land Use: Case Study Section
U.S. Great Lakes Dredging and Confined Disposal Facilities
By Steve Thorp, Great Lakes Commission
For more than 150 years, dredging for navigation purposes has taken place in the Great Lakes. Dredging, involving the removal of accumulated bottom sediments, is necessary to maintain channel depths for safe and efficient vessel operations. In U.S. waters, the U.S. Army Corps of Engineers is authorized to maintain 131 navigation-related projects, nearly all of them commercial and recreational harbors and navigation channels. Many of these projects require periodic dredging. For other commercial and recreational harbors, some are privately owned and maintained or state and local jurisdictions have responsibility. The appropriate disposal of material dredged from navigation projects is a nationwide issue but has important implications for the use, management and protection of waters in the Great Lakes Basin. Confinement of contaminated dredged material, determined to pose an unacceptable risk to the environment, is a federal policy and is recognized as necessary by state and local governments. Many facilities for placement of these polluted sediments have been built in the Great Lakes nearshore area, some in water and others at upland locations. Concern over environmental effects of dredging and disposal of dredged material, the increasing unavailability of suitable disposal sites and dredging's role in supporting waterborne commerce have combined to elevate the issue in the region's public policy agenda.
The history of dredging in the Great Lakes is one of incremental development, responding to both political and environmental considerations, as well as changes in vessel design. Early efforts aimed at improving U.S. harbors, such as the construction of piers and breakwaters and limited dredging, were often undertaken by private and local interests with some federal involvement. Many of these harbors were located in the lower reaches or mouths of tributaries to the Lakes. As vessel size and draft increased over time, harbor sediments needed to be regularly removed and adjacent shore lands modified to widen harbor areas and also to accommodate waterfront development. Federal funding for some of this work ebbed and flowed prior to the Civil War reflecting congressional opinion on "internal improvements." By the middle of the 19th Century and under the direction of the Board of Works, Canadian navigation improvements such as enlargement of the Welland Canal (first opened in 1829 as a way around Niagara Falls) were well underway. When Congressional appropriations for Great Lakes harbors became more regular in support of national infrastructure development and in response to Canadian competition, a pattern emerged that would sustain harbor and channel development up to the present time.
As Great Lakes commodity movement increased, the Corps of Engineers undertook a more system-wide approach to navigation improvements. Connecting channels became a top priority with incremental depth improvements as well as new locks at Sault Ste. Marie, Michigan. The River and Harbor Act of 1892 authorized a minimum 20 foot (6.1 meters) navigation depth in connecting channels and eventually major commercial harbors were also dredged. Vessel drafts and navigation depth continued to increase and in 1956, U.S. legislation set the stage for the current 27-foot (8.2 meters) vessel draft. This Congressional action was related to St. Lawrence Seaway legislation in both Canada and U.S. that culminated with the modern Seaway lock and channel system in 1959. These channel and related harbor deepening activities created an initial increase in dredged material quantities and subsequent maintenance of authorized depths for U.S. projects has continued to generate relatively large volumesfrom 3 to 5 million cubic yards per year (2.3 and 3.8 million cubic meters). Another 1-3 million cubic yards (.76 - 2.3 million cubic meters) are removed annually at other sites controlled by private interests and state and local jurisdictions. Until the mid-1960s, much of the dredged material was redeposited offshore away from navigation channels. Some of it though was used for nearby land filling and to replenish beach sand lost to littoral drift and wave action. Rising concern about Great Lakes water quality and possible connection to polluted sediments resulted in a shift of policy on disposal of dredged material.
During the latter half of the 1960s the Corps of Engineers, in cooperation with the Federal Water Pollution Control Administration (predecessor of USEPA), began to study its Great Lakes dredging activities and related in-water disposal of dredged material. Although the first Great Lake confined disposal facility (CDF) was built near Detroit in 1960, several more CDFs were built as the federal study effort continued. A Corps of Engineers Buffalo District report released in 1969, concluded that, in-water disposal of polluted dredged material was "presumptively" undesirable for the Great Lakes. The Corps investigation coupled with growing concern about water quality in the Great Lakes and elsewhere spurred Congress to take action. With passage of the River and Harbor Act of 1970 (P.L. 91-611), the current era in U.S. disposal of contaminated dredged material from the Great Lakes was launched. Section 123 of this legislation authorized the construction of diked disposal facilities for the Great Lakes. The legislation also authorized the Corps of Engineers to undertake "a comprehensive program of research, study and experimentation relating to dredged spoil" for all U.S. waters. From 1973 to 1978, the Dredged Material Research Program managed by the Corps Waterways Experiment Station had been the principal follow-up program but the study effort has continued through additional coordination with government agencies and other researchers. For example, due to speculation over the effectiveness of Great Lakes CDFs in containing contaminants, an interagency CDF Work Group was formed in 1986, consisting of representatives from the Corps Buffalo, Chicago and Detroit Districts, the U.S. EPA Region 5 and Great Lakes offices of the U.S. Fish and Wildlife Service. A number of studies and monitoring efforts have been conducted by these agencies as well as others.
Since the 1960s, the Corps has constructed 40 confined disposal facilities around the Great Lakes. Of the total number of U.S. Great Lakes CDFs, 14 were constructed on land and 26 were built as in-water facilities often at shore-adjacent or nearshore locations. Those CDFs built in the water average 112 acres (45 ha) in size whereas the upland sites are considerably smaller averaging 36 acres (14.5 ha). In Canada 12 CDFs have been constructed.
Under current dredged material evaluation procedures, about half of the material removed each year is considered polluted or otherwise not suitable for open water disposal and placed in confined disposal facilities. This amount, averaging around 2.5 million cubic yards (1.92 million cubic meters) would fill 500,000 standard dump trucks and if parked end-to-end, the line of trucks would stretch from Windsor, Ontario to Spokane, Washington. The size and design of each facility is site-specific, depending on the location, the nature and potential amount of sediments and how it will be used or function once it is full and/or no longer receiving dredged material. Dikes for in-water CDFs are usually constructed in layers with heavy, protective stone on the outside (heaviest on lakeside)and progressively smaller stones to sand on the inside. Some CDFs incorporate liners or steel sheet pile in the dike walls. As dredged material is pumped or placed in a CDF, the sediments settle out and the accompanying water evaporates or percolates through the walls or into the ground. When permeability is reduced over time because of sediment sealing, a variety of water release mechanisms including overflow weirs and filter cells are used.
The regulation of dredged material disposal activities in U.S. waters is governed by the Clean Water Act of 1972 and its subsequent amendments (CWA). Corps district offices handle permitting under Section 404 except in Michigan where most relevant authority has been transferred to the state. For all of the disposal activities managed by the Corps, the agency conducts an evaluation based on guidelines developed in cooperation with USEPA and must comply with respective state regulations. In addition to this level of regulation, state review of dredge and fill disposal activities under Section 401 is required to certify that such activities will not violate state water quality standards or criteria. Another regulatory issue is whether contaminated dredged material is also subject to hazardous waste regulation and how that complicates the review and permitting process. Pennsylvania is one of the states with this concern. For various dredging projects around the Great Lakes, the evaluation process, particularly as it relates to open water disposal of dredged material and CDF expansion or location, has become publicly contentious and administratively protracted. Part of the problem rested with national testing guidelines and evaluation criteria used under Section 404 that were deemed to be inadequate for the Great Lakes. As a result, the Corps' North Central Division and the EPA regions having some Great Lakes jurisdiction have prepared a draft Great Lakes Dredged Material Testing and Evaluation Manual (released for public review and comment October 1994). Evaluation of dredged material will be through a tiered approach, starting with a "reason-to-know" that sediments are contaminated and, if necessary, progressing to more rigorous chemical, physical and biological assessments. If a contaminant determination is made, confinement and/or remediation of the polluted material triggers another set of issues, some of which pose formidable future challenges.
Great Lakes ecosystem health depends, among other things, on contaminant elimination or, where necessary, a high level of contaminant isolation. A major concern relates to how effective CDFs are in keeping the material from recontaminating the surrounding environment. Contaminants often bind with fine sediments such as silt and clay. To the extent that this form of pollution is confined to the CDF and bioaccumulation of pollutants by plants and animals in or near CDFs is not significant, then CDFs are presumed to be relatively efficient. Volatilization of contaminants is another potential problem but it varies from site to site. There is no systemwide, continual monitoring program for Great Lakes CDFs. However, CDF water quality monitoring generally occurs during dredging and disposal operations and 12 CDFs do have monitoring wells in dike walls. The effectiveness of these monitoring wells has been questioned and may have limited value. Also many environmental studies have been conducted at selected CDFs around the Great Lakes with interesting results. A 1993 CDF report prepared by the Corps' North Central Division summarized the overall environmental status of CDFs as reported in studies to date by stating, "The results of water quality monitoring has confirmed that CDFs are highly efficient at retaining the sediment solids and attached contaminants." CDF influent typically has suspended solids levels around 100 mg/1 whereas effluents are normally around 1 mg/l. With respect to contaminant losses from in-water CDFs, detailed studies at several facilities show a high level of efficiency at keeping pollution within the CDF itself. For example, computer modeling of PCB loss at the Saginaw Bay CDF indicates a 99.82 to 99.93 percent efficiency. Biomonitoring studies there did not detect any contaminant transfer. But these kinds of evaluations can also have problems because of the presence of background contamination. At the Chicago Area CDF, tissues from organisms near the CDF were shown to be no different (with respect to contaminant levels) than those taken from remote locations. But fish and invertebrates collected from within the CDF did reveal some elevated contaminant levels. The Times Beach CDF at Buffalo has had more biological studies than any other Great Lakes CDF. This 46 acre (18.6 ha) facility was used for only 4 years before becoming designated a nature preserve in 1976. Dozens of studies since have shown some mobility of heavy metals through the plant community into soil invertebrates in an upland area. Contaminant mobility within wetland and aquatic communities has been detected but not yet fully quantified. Studies have been undertaken for all Canadian CDFs and the results indicate that plant and animal life that inhabit CDFs are bioaccumulating contaminants. Canadian researchers have suggested that waterfowl that inhabit or visit CDFs may be good biomonitors of bioaccumulation of sediment-associated contaminants. Even though CDFs appear to be efficient regarding retention of the contaminants, more research is needed to describe the potential contaminant exposure pathways associated with CDFs and test mitigation strategies such as capping or otherwise eliminating or neutralizing sediment exposure.
The use of confined disposal facilities in the Great Lakes continues to be necessary. Originally, the main CDF program authorized by P.L. 91-611 envisioned use of such facilities for a 10 year period. It was believed that progress in pollution control particularly from municipal and industrial point sources would sufficiently reduce the contamination of sediments and thereby eliminate (or reduce) the need to use CDFs. However, the extensive accumulation of contaminated bottom sediments particularly in industrial harbor areas and tributary river reaches and continuing land use practices that create erosion, sedimentation and related pollution require on-going confinement of large quantities of polluted dredged material. Contaminated sediments in the Great Lakes represent an acknowledged threat to Basin ecosystem health. Human health is threatened, particularly through fish consumption and related PCB contamination related to polluted sediments. Long-term use of CDFs is the principal means to address the overall problem of disposal of contaminated sediments derived from dredging for navigation purposes, but other strategies exist. Remediation or clean up of polluted material from a CDF or elsewhere has been demonstrated to be technologically feasible through various means, but is relatively expensive compared to placement/storage in a CDF. Sediment reduction at the source, though, offers much promise, both as a means to reduce polluted sediment transport and, where possible, lessen navigation-related dredging requirements.
Most of the sedimentation in tributary rivers and streams to the Great Lakes is caused by human activity. Although agricultural practices are the primary culprit in many sub-basin areas, construction activity and the relative imperviousness of the built environment also contribute to sediment loads and transport dynamics. Littoral drift is a natural process which contributes to some sedimentation in navigation channels exposed to or near the open lake. Also, siltation levels are high for many Great Lakes harbors, particularly those that contain river flows and where the basin has substantial agricultural activity. For example, the largest tributary of Lake Erie, the Maumee River, with a 6,750 square mile (17,483 square kilometers) watershed, transports huge quantities of silt and clay sediment that cause shoaling in parts of the river and at the Port of Toledo. It was estimated that the mean annual sediment load for the Maumee River during the 1980s was 1.1 million metric tons representing about 10 percent of annual gross erosion in the Maumee watershed. In addition to the physical movement of sediment and associated dredging impacts, sediment-produced turbidity reduces light penetration affecting aquatic plant growth. Agricultural runoff is also a primary source of phosphorus loading for streams and rivers and especially for lakes. The infusion of phosphorus into receiving waters, in both its soluble and particulate (in association with sediments) forms, acts as a plant nutrient resulting in eutrophication problems.
The control of erosion is recognized as a key component for reducing sedimentation in streams, rivers and Great Lakes harbors as well as reducing associated chemical pollution. In a recent initiative of the U.S. Natural Resources Conservation Service in the Maumee River Basin, erosion control projects for the three state, 25 county area, is aiming at a 15 percent annual reduction in the volume of sediment dredged at Toledo for several successive years. The increasing adoption of conservation tillage (reduced til and no-til) has made significant progress in parts of the Basin in reducing erosion rates as well as phosphorus and pesticide loads for tributary waters and the Great Lakes. Other measures and programs such as acreage set-asides embodied in the Conservation Reserve Program, and Ontario's Conservation and Environment Protection Assistance Program along with contour plowing, vegetative and woodland cover efforts in erosion-prone areas, filter strips, and sediment detention ponds have proved that progress is possible on this difficult issue where land meets the water.
Additional CDF capacity beyond that which exists now or alternatives will be needed. Some CDFs have been filled to capacity and are no longer being used and all but two of the 26 CDFs built and used under P.L. 91-611 will be full or at design capacity by the year 2006. There are added concerns among states and communities that certain CDFs could be used for material originating far away from their localities as other CDFs fill up and despite the high cost of transporting the material. Without more CDF capacity, much of the maintenance dredging for navigation purposes could come to an end with serious consequences for commercial navigation and the regional economy. The Lake Carriers' Association indicates that even slight decreases in available depth reduces significantly a vessel's carrying capacity. For example, with respect to the workhorse vessel of the Great Lakes fleet, the 1000-footer, it loses 270 tons (245 metric tons) of cargo for each inch (2.54 cm) reduction in draft. For steel production dependent on waterborne commerce and with its connection to the region's durable goods manufacturing sector, low-cost, efficient transport of raw materials on the Great Lakes is necessary. New construction of CDFs or expansions of existing ones are subject to non-federal cost sharing. With a CDF costing potentially several million dollars to develop, the willingness and ability of non-federal sponsors to build new CDFs has been understandably muted. Another serious problem is the siting of new CDFs. The Great Lakes have the most in-water CDFs in the country and this apparent bias in favor of water locations is partly explained by the relatively high cost of upland sites which are often in highly urbanized areas. An alternative to a water site that is getting a closer look is using an existing contaminated site and incorporating a cleanup as part of the CDF construction process. Ccontaminated sediments from Indiana Harbor are likely to end up at such a nearby site.
Several communities around the Great Lakes are taking a "conservation-of-space" approach to the problem of future CDF capacity as well as planning for new facilities when they may become necessary. For example, in the shared harbor at Duluth, Minnesota and Superior, Wisconsin, the CDF known as the Erie Pier Dredged Materials Placement Facility, has been the site of a successful sediment cleaning and sorting activity. Coarser-grained material (clean) is separated from the finer particles and reused offsite for construction, road maintenance and other purposes. This process, supported by the local Remedial Action Plan Citizens Advisory Committee, will increase the lifespan of the CDF. In Cleveland, an option to raise dike walls on a CDF that is close to capacity has been ruled out in favor of building a new CDF adjacent to a waterfront airport. In this case, land use considerations were very important where the City planned to add the existing CDF to its park space and the new CDF would be compatible with airfield operations. In Ashtabula, Ohio the lack of a plan to dispose of highly polluted sediments from a portion of the lower Ashtabula River prevented any dredging from 1979 until 1993, when a limited amount of recreational dredging took place with temporary disposal at a river adjacent confinement site. Eventually, this polluted material along with a greater volume of dredged material, will be moved to a permanent upland site. Two sites are now under active consideration by the Ashtabula River Partnership, a public/private group of stakeholders. In Toledo, Ohio a Harbor Planning Group made up of local, state and federal officials has developed a long-term management strategy for its dredged material disposal problems. With an average of 850,000 cubic yards (649,910 cubic meters) of sediment needed to be dredged each year, this large volume has spawned a three-pronged approach: 1) continued short-term use of the harbor CDF for nearly three-quarters of the sediment with the rest determined to be suitable for open lake disposal; 2) concerted effort to continue reuse of dredged material subject to cleaning and combined with sewage sludge to create top soil material along with efforts to better manage CDF sediments through dewatering to facilitate compaction (to create additional capacity); and 3) plan for a new CDF-type facility that would function as a shoreline protection structure and also create wildlife habitat and eliminate the need for future open lake disposal. These three activities combined with the effort to substantially reduce erosion and sediment transport in the Maumee River basin has created a plan, to not only protect the waters of Lake Erie, but maintain the port as a valuable economic development asset for the region.
Now that many CDF's have been built, with several closed for disposal operations, there is an interest in converting them to another use. The only CDF built under P.L. 91-611 that has been released from Corps of Engineers jurisdiction is the small facility at Kenosha , Wisconsin. Part of the CDF (2.5 acres/1 ha) is now city parkland. A marina has also been developed adjacent to it utilizing some of its structure. Various other CDFs are being contemplated as part of parkland areas or specially developed to provide wildlife habitat and/or function as shoreline protection structures. The Pointe Mouillee Diked Disposal Project on Lake Erie south of the Detroit River illustrates this multiple purpose approach to CDF development and use. The 700 acre (283 ha) diked island was needed to hold polluted dredged material from the Detroit and Rouge Rivers when other containment areas were nearing capacity. Its location and crescent-shape configuration was designed as a barrier island to protect the Pointe Mouillee State Game Area and associated marsh from wave action. This area is the largest in the Detroit area.
Dredging and fill operations in the Great Lakes have modified the shoreline and nearshore waters in many places. Thousands of acres have been added to urban waterfronts including harbor areas. Some of this "created" land is occupied by parks and buildings and other land has been used for industrial and port development. Confined disposal facilities, many with their unique non-developable status, encompass hundreds of these nearshore acres throughout the Great Lakes. They do serve an important environmental purpose. Possibly, with appropriate planning and remediation, existing and future CDFs can also support more direct human uses.
Last Modified: November 04, 2002
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