Can NRDAs take the environment back to the future? New York's Hudson River stretches over 200 miles from the wilds of Glens Falls to the canyons of Manhattan. Wisconsin's Fox River hosts the largest concentration of paper mills in the world. What the two rivers share is a legacy of PCBs. Both will become the focus of intense scientiÆc economic and legal energy when two giant Natural Resource Damage Assessments (NRDAs) get into full swing next year. Already the U.S. Fish and Wildlife Service has estimated that for the Fox River where historic PCBs contamination has meant Æsh advisories for every species of sport Æsh lost Æshing opportunities total over $100 million in public damages.1 For the Hudson NRDA estimates are much higher. NRDAs are a little known part of the Superfund Law which empower certain federal and state agencies to seek damages for injuries to public natural resources caused by hazardous wastes.The idea is to replace or restore damaged natural resources so that they can continue to be enjoyed by the public. But this simply stated aim makes complex scientiÆc and economic demands. Agencies must assess the extent of the damage and link it to a toxic release; Hudson River The General Electric Hudson Falls plant in northern New York used PCBs in the manufacture of capacitors from 1957 to 1977. It is one of two plants whose discharges contaminated the river. Photograph courtesy US Environmental Protection Agency. This journal is # The Royal Society of Chemistry 2000 devise a restoration plan; and determine the full value of what the public has lost.This value can be large indeed. The Exxon Valdez oil spill the largest and most famous NRDA cost Exxon $1 billion in addition to the clean-up bill of $2 billion. NRDAs at hazardous waste sites have to date been much more modest. Close to 70 sites have been settled for some $177 million,2 with six settlements accounting for most of the expenditure. In Natural Resource Damage Assessments scientists and economists work closely together. Scientists are involved in measuring injury and teasing out the links between contamination and some measure of harm by determining a pathway from the contamination to exposure of the resource. At every step economists are also involved in determining the value of the claim– whether in terms of money or in terms of other natural resources that could replace what has been lost.Challenging science For both the Fox River and the Hudson River scientists will be trying to resolve long-standing disagreements over PCBs fate and transport. In the Hudson River for example,EPAcontends on the basis of its sampling program that large quantities US Focus of PCBs are still washing out of old deposits in the upper part of the river. But General Electric the principle responsible party claims based on its own sampling program that old PCBs deposits are no longer a problem because they are being buried by fresh clean sediment. EPA's efforts compared data from core samples taken in 1994 with data from core samples taken between 1976 and 1984.The data show that about three-quarters of PCBs lost from the pool entered the water column and were redistributed throughout the Hudson River system according to EPA. But GE contends that the agency took too few samples failed to study them in sufÆcient detail compared results from two different and incompatible sampling techniques and misused a key statistic.3,4 Damages to natural resources are judged in comparison to ``baseline'' or what the ecosystem would have been like had it not been for the contamination. But the dynamic nature of ecosystems plays havoc with a simple-minded conception of a stable undisturbed system.For example for the Fox River NRDA an extensive study of lake trout reproduction found that lake trout could no longer reproduce. But a thorough investigation revealed that PCBs long thought to be the primary factor appear to be less important than egg thiamin deÆciency. This is believed to happen because lake trout eat alewife a Æsh that was introduced into the Great Lakes. As a result lake trout injuries will not be included in the NRDA.1 Unique economics NRDAs are unique in terms of their economic aspects especially in the role of compensatory damages. Compensatory damages seek to compensate the public for the loss of a resource from the time when the damage occurred until restoration. In the past these damages were valued in monetary terms but the new emphasis on restoration now favors habitat equivalency.5 In habitat equivalency the object is to Ænd one aspect of a habitat called a metric that can stand for the habitat as a whole.This metric is then used to assess other habitats and to Ænd comparable replacements. For example in a coastal setting trustees might use the average 51N J. Environ. Monit. 2000 2 US Focus Fox River Aerial photograph of the lower Fox River adjacent to the Fort James East Paper Mill (the facility is in the foreground). PCBs used in the manufacture of carbonless copy paper led to the Fox River's contamination. Photograph courtesy US Fish and Wildlife Service. stem density and height of sea grass to compare habitats.This one measure can account for Æsh habitat sediment stabilization contaminant Æltration and all of the other services the habitat provides. In addition to determining whether a given area has the physical and biological capacity to provide a range of services. NRDA economists also look at 52N J. Environ. Monit. 2000 2 ``opportunity'' and ``payoff''. For example to use the capacity of a wetland to Ælter water there needs to be an upstream pollution source to present the opportunity. If there were a shellÆsh bed downstream then the payoff is great while the presence of a fast Øowing stream would offer a smaller payoff. In the next few years the giant NRDAs for the Fox and Hudson Rivers will sorely test these concepts in an effort to see if the legal system can use science and economics to get back to the future.Notes 1 US Fish and Wildlife Service press release (http //www.fws.gov/r3pao/ext_affr/ news_rel/ea99_50.html) 2 Superfund status of selected federal Natural Resource Damage SettlementsGAO/RCED-97-10 November 1996. 3 Phase II Reassessment Data Evaluation and Interpretation Report for the Hudson River PCB Superfund Site; U.S. Environmental Protection Agency(Region 2) U.S. Government Printing OfÆce Washington DC February 1997.Available at http // www.epa.gov/region02/superfnd/hudson/ 4 Phase II Reassessment Low-Resolution Coring Report for the Hudson River PCB Superfund Site; U.S. Environmental Protection Agency (Region 2) U.S. Government Printing OfÆce Washington DC July 1997. Available at http //www.epa.gov/region02/superfnd/ hudson/ 5 National Oceanic and Atmospheric Administration Damage Assessment and Restoration Program (revised June 1996) Habitat Equivalency Analysis. Policy and Technical Paper Series No. 95-1. Rebecca Renner Science Writer and Editor Tel z1 570 321 8640 Fax z1 570 321 9028 E-mail applepie@sunlink.net