DECIDING WHEN TO INTERVENE

Saginaw Bay is a relatively large (2,960 km²) southwestern extension of Lake Huron, located in the east central portion of Michigan's lower peninsula. The Saginaw Bay watershed drains 22,557 km², including portions of 22 counties and 15% of Michigan's total land area. Saginaw Bay is regarded as one of the prime walleye fishing and waterfowl hunting areas in the Great Lakes.

Industrial facilities and wastewater treatment plants on the Saginaw River have released PCBs (polychlorinated biphenyls) and related compounds into the Saginaw River for decades. These releases have decreased in recent years as a result of various controls, but sediment remains contaminated and the PCBs released have caused environmental damage to the ecosystem of the Saginaw River and Bay. The bay also drains into Lake Huron, so contaminants pose far reaching risks if not contained and halted.

Contamination has impacted fish and wildlife resources in the Saginaw River and Bay, resulting in advisories against human consumption of all species of fish in the river and many species of fish in the bay. Also, bald eagle reproduction is significantly lower in these areas than found in less contaminated areas.

The U.S. Fish and Wildlife Service, the State of Michigan, and the Saginaw Chippewa Tribe worked as co-trustees in conducting a Natural Resource Damage Assessment for the Saginaw River and Bay. In the assessment process, the trustees evaluated injuries to trust resources as well as restoration actions that could restore the ecosystem functions and compensate the public for injuries to their natural resources caused by the release of PCBs.

In the injury assessment process, the trustees selected species of concern and endpoints to evaluate, and then calculated target concentrations of PCBs in the sediment. Bald eagles and fish-eating birds were selected for evaluation because they are at the top of the food chain and are therefore highly exposed to PCBs. In addition, many published reports were already available on the effects of PCBs on fish-eating birds in Saginaw Bay and at other Great Lakes sites, in both contaminated and reference areas. Mink were selected because they are also fish-eaters, and because mink are highly sensitive to PCBs and related compounds. Studies in which ranch mink were fed fish from Saginaw Bay had clearly demonstrated that mink reproduction could be impaired by such a diet. Finally, sport fish were selected for analysis because of past and existing fish consumption advisories for PCBs and because of the value that the public places on having fishable waters from which they can eat the fish.

The endpoints selected for evaluation for the birds were reproduction and recruitment. Decreased hatching and fledgling success were documented in the field, and concentrations of PCBs were measured in tissues and prey items. A steady-state bioaccumulation model was used to calculate a No Observable Adverse Effect Level (NOAEL) in whole forage fish from a NOAEL value in bird eggs from the literature. Site-specific information was then used to estimate sediment concentrations which correspond to the NOAEL in forage fish.

The endpoint selected for evaluation for the mink was reproduction. Laboratory data demonstrated effects in the laboratory and anecdotal information indicated a reduction in populations in the area (decreased ratio of incidental mink capture to muskrat capture by trappers). An oral dose model was used to calculate a NOAEL in the fish component of the mink diet from an oral dose NOAEL from the literature. As for the birds, site-specific information was then used to estimate sediment concentrations which correspond to the NOAEL in forage fish.

The endpoint for sport fish was target tissue concentrations low enough such that consumption advisories for PCBs could be removed. Site-specific information was used to estimate sediment concentrations corresponding to target tissue concentrations in sport fish fillets.

Sediment thresholds were compared to spatial patterns of PCB concentrations in Saginaw River and Bay. Thresholds were exceeded in surficial sediment in many areas of the river and the inner part of the bay. A few thresholds were exceeded in the outer bay. The patterns of PCB concentrations with depth indicated that inputs to sediment in the river have decreased recently, but that PCBs in the bay are at greater concentrations at the surface than at depth. The sediment of the Saginaw River contains a significant mass of PCBs, which has the potential to be released downstream. Thus, the river continues to be a source of PCBs to the bay.

The trustees decided that it would not be practicable to remediate sediment to all threshold levels everywhere that they occur. Without field-proven methods for in situ reduction of PCB concentrations to the sub- mg/kg range, removal and capping were the options considered. Capping was not a viable option for the river because of its shallow depth, regular dredging, extensive recreational and commercial navigation, and trend toward shoreline development with dredging and bulkheading. The trustees concluded that removal (or capping) of large areas of sediment (hundreds of square kilometers) in the bay was likely to cause a disproportionate destruction of habitat. The trustees selected removing the largest mass of PCBs

practicable from the river and compensating the public for past and continuing injuries to natural resources as their goals in the negotiations with responsible parties.

The trustees recently reached a negotiated settlement for natural resource damages with General Motors Corporation and the cities of Bay City and Saginaw. The settlement provides for substantial cleanup of river contamination and for protection and restoration of fish and wildlife habitats in the Saginaw River and Bay. The settlement is one of the largest achieved by the Department of the Interior as the lead federal agency to recover natural resource damages.

The settlement will result in the removal of 264,000 cubic meters of contaminated sediment, or about 90 percent of the mass of PCBs in the lower river (Table 1). Dredging is expected to begin in 2000. Although not all risk will be removed, experts believe that additional restoration dredging would significantly increase the physical injury to habitat while providing little additional removal of PCBs. The settlement also provides for acquisition, restoration, and protection of more than 680 hectares of habitat, as well as restoration of acquired land that has been drained previously for agricultural use. Restoration will also include fish habitat between Saginaw Bay and Tobico Marsh, and for the Green Point Environmental Learning Center in Saginaw. Boat launches and nature viewing opportunities will be provided at two sites on the river in Bay City and at one site on the bay in Essexville to compensate the public for injuries to the State's resources. A restoration account will be funded by the responsible parties so that the trustees can monitor recovery of the system and make informed decisions on balancing additional habitat restoration projects, additional cleanup activities, and continued monitoring.

Table 1. Components of the Saginaw Natural Resource Damage Assessment Settlement

Component	Description	Cost
Removal of contaminated sediment from deposits in the Saginaw River	264,000 cubic meters will be removed and placed in an Army Corps disposal facility dredging will meet environmental performance criteria dredging will be managed by the Corps with oversight and responsibility by the Service and the State project will take 1-2 years dredge design has optimized to remove 90% of the mass of PCBs remaining in the lower river	$11,150,000
Land acquisition to restore habitat and to protect existing habitat from development	680 hectares land to be owned and managed by the Michigan Department of Natural Resources, the Saginaw Chippewa Tribe, and the Service's Shiawassee National Wildlife Refuge land selected based on long-lasting ecosystem management objectives, relationship to existing public lands, and restoration of resources injured by PCBs	$6,700,000
Restoration on acquired land	restoration of acquired land which was previously drained for agriculture emphasis on coastal wetlands and lake plain prairie	$1,000,000
Tobico Marsh restoration	restoration of water flow between Saginaw Bay and Tobico Marsh emphasis on restoration of northern pike and yellow perch spawning	$500,0000
Green Point Environmental Learning Center activities	restoration of lost services because of injury to natural resources emphasis on services important to area residents	$520,000
Green Point Environmental Learning Center leases	two 99-year leases of Green Point Environmental Learning Center includes interpretive center building and 32 hectares of riparian and upland habitat	not quantified
Restoration Account	funds in court registry account to be managed by Trustee Council emphasis on monitoring recovery and implementing additional restoration projects monitoring builds on existing assessment data	$3,100,000
Recreational/educational areas	three areas with boat launches, nature-viewing opportunities, interpretive signs Bay City will operate and maintain two of the areas and MDNR will own and operate the third	$3,500,000
Cost Recovery	Service to receive $0.8 million for past assessment and future oversight costs State to receive $1.2 million	$2,000,000