Ecotoxicology and Environmental Safety 52, 46 56 (2002) Environmental Research, Section B doi: IO. 1006/eesa.2002.2145, available online at http://www/idealibrary.com on IO E +l”

Regulatory Implications of Using Constructed toTreat Selenium-Laden Wastewater

and agricultural wastewater during the past two decades. The practice of using constructed wetlands to treat seleninm- Textbooks such as those by Hammer (1989), Moshiri laden wastewater is gaining popularity in the linited States and (1993), and Kadlec and Knight (1996) attest to the elsewhere. However, proponents of treatment wetlands often escalation in awareness and application of this treatment overlook important ecological liabilities and regulatory implica- technology. Constructed wetlands can substantially im- tions when developing new methods and applications. Their prove down-gradient water quality by removing pollutants research studies typically seek to answer a basic performance question-are treatment wetlands effective in improving water through a variety of chemical, physical, and biological quality-rather than answering an implicit safety question-are processes. Pilot or operational-scale wetlands have been they hazardous to wildlife. Nevertheless, owners are used to remove everything from sediment and nutrients to responsible for both the operational performance of treatment organic chemicals, pesticides, trace elements, and heavy wetlands and the health of animals that use them. This is true metals. With their apparent low cost relative to conven- even if wetlands were not created with the intent of providing tional wastewater treatment methods, as well as the wildlife habitat; the owner is still legally responsible for toxic environmentally friendly image they generally convey, hazards. If poisoning of fish and wildlife occurs, the owner can be constructed wetlands have become popular throughout prosecuted under a variety of federal and state laws, for many regions of the world (Kadlec and Knight, 1996). example, the Migratory Bird Treaty Act and the Endangered In addition to improving water quality, treatment Species Act. In considering this type of treatment technology it wetlands create habitat for wildlife--- sometimes conspic- is important to document the selenium content of the waste- uous, sometimes not. In some cases the habitat function water, understand how it cycles and accumulates in the environment, and evaluate the threat it may pose to fish and may be considered a valuable feature, and it may even wildlife before deciding whether or not to proceed with influence the construction design of wetlands to enhance construction. Many of the potential hazards may not be obvious wildlife use; in others it may be overlooked or ignored. to project planners, particularly if there is no expressed intention Whether recognized or not, it is important to understand for the wetland to provide wildlife habitat. Ecological risk that the habitat feature will attract wildlife, which may be assessment provides an approach to characterizing proposed exposed to hazardous concentrations of pollutants retained treatment wetlands with respect to wildlife use, selenium in the wetlands (e.g., Helfield and Diamond, 1997). contamination, and possible biological impacts. Proper applica- Poisoning of wildlife is especially likely when wastewatel tion of this approach can reveal potential problems and the contains a substance that bioaccumulates in their food associated liabilities, and form the basis for selection of an organisms, for example, selenium (Ohlendorf c’r al., environmentally sound treatment option. G 2002 lilsevier Sricnce (154) 1986a,b; Lcmly et al., 1993; Skorupa, 1998). Thus, it is possible for treatment wetlands to create toxic conditions while at the same time improving water quality for down- INTRODUCTION gradient ecosystems. There has been a m;l.jor expansion in the use of The overlap of these two factors, contaminant removal constructed wetlands for treating industrial, municipal, and wildlife exposure, conveys important responsibilities to wetland owners and managers. They are responsible for ‘To whom correspondence should be addressed. FZX: (540) 23 I - 1383. both the operational performance of treatment wetlands E-mail: dlemly(cr vt.edu. and the health of animals that use them. This is true even if

46

0147-65 13:02 x35.00 (‘ 2002 Elsevier Science (USA) All riehrs recervcd. 0AP

SELENIUM IN CONSTRUCTED WETLANDS 41

wetlands were not created with the intent of providing wildlife habitat; the owner is still legally responsible for toxic hazards. For example, if poisoning of migratory waterfowl or shorebirds occurs, the owner can be prosecuted for violating the Migratory Bird Treaty Act (Margolin, 1979). Proponents of treatmcnt wetlands often overlook this type of liability when developing new methods and applications (e.g., Rodgers and Dunn, 1992; Hawkins ct al., 1997; Hansen et al., 1998; Terry and Zayed, 1998). Their research studies typically seek to answer a basic performance question----are treatment wetlands effective in removing contaminants‘?---rather than answer- ing the implicit safety question-are they hazardous to wildlife? In this article we examine the selenium liability issue by discussing a classic case example that illustrates where and FIG. 1. Major pathways for selenium movement in wetland ecosys- how problem situations can arise, and the possible tems. The same process that makes treatment wetlands effective in regulatory consequences to wetland owners. We also removing selenium from water bioeccumulation in food chains can provide guidance on how ecological risk assessment can render them unsafe by exposing wildlife to toxic levels of selenium in their be used to evaluate proposed treatment wetlands and diet. Those who are considering treatment wetlands for selenium removal identify problems. need to understand the ecological liabilities associated with this technology as well as the regulatory implications that can result if wildlife poisoning occurs. ,ECOLOGICAL LIABILITY: CREATING TOXIC HAZARDS TO WILDLIFE The consequences can be severe, culminating in teratogenic The major objective of treatment wetlands is to remove deformities, reproductive failure, and elimination of entire materials that could threaten the health and biological animal communities (Ohlendorf et al., 1986a; Hoffman integrity of down-gradient receiving waters. If that goal is et al., 1988; Lemly, 198&b, 1993b). Waterborne concen- achieved, ecological benefits result. However, if the waste- trations above 16pg Se/L pose an even greater threat to water being treated contains selenium, the apparent wildlife health (Ohlendorf, 1989; Ohlendorf et al., 1986b; benefits to down-gradient water quality can be more than Skorupa and Ohlendorf, 1991; Lemly, 1997a). Wastewaters offset by toxic hazards created within the wetlands. The that are treated to remove selenium typically contain end result can be a net loss of benefits and creation of an >2Opg Se/L (Hansen et ul., 1998) and thus fall into the ecological liability that would not exist if predischarge highest risk category. wastewater treatment technologies were used. Treatment The habitat feature of constructed wetlands is the second wetlands may thus raise serious environmental safety principal factor in the liability scenario. It is important to issues. understand that constructing wetlands-whether a O.l- ha There are two principal factors responsible for ecological treatment cell or a 50-ha marsh--creates habitats suited to liability. First is that selenium strongly bioaccumulates in a variety of animals, particularly invertebrates eaten by fish wetland plants and animals. Bioacculnulation creates an and wildlife. This sets the stage for problems because a important dichotomy; on one hand, it can remove selenium contaminant exposure pathway is established. Biologically from water and make wetlands very effective treatment removing selenium from water and providing wildlife tools; on the other hand, it can render wetlands unsafe by habitat are not compatible wetland functions. However, exposing wildlife to toxic levels of selenium (Fig. 1). For it is not easy to separate the two and simply design a example, waterborne selenium concentrations of 2--16 1.18 wetland to exclude wildlife. What might seem to be Se/L (parts per billion) can increase manyfold in aquatic unattractive conditions from an engineering standpoint, food chains and may reach 35,000 times the water e.g., shallow, hot, hypersaline water, no macrophytes or concentration in fish and wildlife tissues (Lemly, 1993a), emergent vegetation, can turn out to be a magnet for resulting in damage to internal organs, physiological wildlife because of invertebrates that Aourish under those dysfunction, and death (Sorensen, 1986; Ohlendorf et al., conditions (e.g., Parker and Knight, 1989). Short of 19X&~). In addition to these direct toxic effects, there are enclosing wetlands under domes, there is no method that also important indirect impacts. Selenium consumed in the will completely eliminate wildlife exposure to selenium diet of adult birds and fish is passed to their offspring in contamination. For example, perimeter fences may exclude eggs, where embryos absorb the selenium as they develop. certain mammals but do not affect use by birds (Hawkins 48 LEMLY AND OHLENDORF et ul., 1997). Propane noise cannons and human patrols have a clear understanding of the ecological liabilities that may not eliminate poisoning of waterfowl and shorebirds can result. (Zahm, 1986; Hoffman et nl., 1986). Even covering a wetland with screening to exclude birds still allows passage REGULATORY IMPLICATIONS: FEDERAL of selenium-contaminated insects, which can be a signifi- AND STATE STATUTES cant route of exposure for insectivorous birds and mammals (Hothem and Ohlendorf, 1989; King et al., In the United States, legal responsibility for endangering 1994). Taking the steps necessary to reduce ecological the health of wildlife stems from a variety of federal and liability can increase the cost of wetland treatment state laws. At the federal level, liability is imposed dramatically, perhaps to the point of making the project primarily by the Migratory Bird Treaty Act and the unfeasible from an economic standpoint. Endangered Species Act. State environmental laws may The most insidious reason for liability problems is the augment these statutes to create significant additional failure of those who develop wetland selenium treatments liability at a local level. For example, in the . to adequately evaluate risks to wildlife. Because of highly Toxic Pits Act, the Katz Act, the Porter-Cologne Water publicized examples of selenium-poisoned waterfowl and Quality Control Act, and the Public Trust Doctrine all shorebirds (e.g., Kesterson Marsh, CA; see following case frame the definition of environmental acceptability in s example), the need to thoroughly examine these risks which treatment wetlands must function (Dunning, 1985). should be obvious, yet major oversights continue to occur. Thus, it is critical for those who wish to construct For example, researchers developing treatment methods treatment wetlands to understand the laws that will typically seek to establish how effective wetlands can be in determine the ultimate fate of their projects. Because of removing selenium from water, but make little effort to broad applicability and implications, the principal federal document or disclose ecological liabilities. This is particu- statutes are discussed here in some detail. larly evident with regard to “phytoremediation” techniques that rely on bioaccumulation as the selenium removal Migrntory Bird Treaty Act (MBTA) mechanism (e.g., Hansen et al., 1998; Terry and Zayed, 1998). Consequently, the methods have-inherent dangers This statute was legislated by Congress in 1918 to that are not readily apparent to potential users. Another implement the convention between the United States and major source of problems is failure to recognize that Great Britain protecting certain birds that migrate between selenium should be a high priority concern in the waste- the United States and Canada. Migratory bird treaties were water being treated. For example, methods developed to later reached with Mexico, Japan, and Russia, and the Act remove heavy metals (Cu, Pb, Zn) from oil refinery was amended in 1974 to bring these treaties within its effluents (e.g., Hawkens et al., 1997) do not recognize the provisions (Margolin, 1979; Vencil, 1986). For many years, presence of elevated selenium (>20 ug Se/L) in the criminal prosecutions under the Act were for violations of wastewater or acknowledge the potential for creating hunting regulations. Then in 1978 there were two cases that environmental hazards. Moreover, selenium is not men- extended prosecutions and convictions to situations where tioned as an item of concern when refinery ellluents are birds were not intentional targets. Those cases involved discussed in treatment technology textbooks (e.g., Kadlec inadvertent deaths of birds resulting from pesticide and Knight, 1996), or when case examples are used to contamination. In the first case, poisoning occurred as a illustrate the benefits of wetland treatment of refinery result of wastewater released from a pesticide manufactur- wastewater (e.g., Amoco Oil Company’s Mandan, North ing process. The U.S. Court of Appeals for the Second Dakota Refinery; Hammer, 1989; Kadlec and Knight, Circuit held that intent to kill birds is not required for 1996). Similar problems exist in recognizing potential conviction under the MBTA. In the second case, birds died threats from coal processing materials and combustion in a field recently sprayed with an insecticide. The District wastes (e.g., Hammer, 1989; Kadlec and Knight, 1996) all Court of the United States for the Eastern District of of which can contain high concentrations of selenium and California reached the same decision with regard to ’ lead to significant environmental hazards (Lemly, 1985b). criminal liability. These two court decisions set an These oversights are a major shortcoming that is pervasive important precedent that has far-reaching implications in the wetland treatment technology field. It is essential to for treatment wetlands. The MBTA provides a means of know the entire chemical matrix of wastewater and prosecuting those who bring harm to birds, regardless of evaluate each component under the planned treatment intent (Margolin, 1979). This liability cannot be eluded by scenario. saying that treatment wetlands were not created to provide Many wetland treatment methods are being marketed habitat for wildlife. If poisoning occurs, the owners/ without full knowledge or disclosure of the risks they pose operators are in violation of the MBTA. Importantly, to wildlife. Those who wish to apply the methods should many of the birds likely to be attracted to treatment SELENIUM IN CONSTRUCTED WETLANDS 49

wetlands fall under MBTA protection: waterfowl, shore- threatened species, and (2) to prevent degradation of birds, and a variety of wading birds. habitat that supports those species. Creating a treatment The penalties imposed under the MBTA are substantial, wetland whose contaminant load poisons wildlife or plants and suits can be brought by private citizens, conservation violates both of these elements. groups, natural resource management agencies, and The current federal list includes 896 endangered species regulatory authorities (Vencil, 1986). Killing one bird (343 animals, 553 plants) and 230 threatened species (11.5 constitutes a violation and conviction carries a fine of animals, 115 plants) (U.S. Fish and Wildlife Service, 1998). $US 500.00 and 6 months imprisonment, or both, on each Although what constitutes a count and violation under count. The prosecution can charge counts for each type of ESA is similar to that under MBTA, penalties under ESA bird poisoned and each day on which birds are killed are more severe. For example, each count can carry a fine (Vencil, 1986). Thus, the greater the degree and persistence exceeding $US lO,OOO.OO and 1 year imprisonment, or of impacts to wildlife health, the greater the potential both. An important point to note is that there are penalty. For example, a poisoning event that kills three numerous state laws that complement and extend the kinds of birds on 6 consecutive days could generate 18 federal legal authority for ESA to a local level. Many states counts, with a total fine of $US 9000.00 and a jail term of 9 also have their own lists of endangered and threatened years. species, which makes liability under ESA even more broad The power of the MBTA is evidenced by the outcome of and far reaching (Bean, 1986). major state and federal cases in which it was not even It is not necessary for an endangered or threatened invoked in a court proceeding, but only raised as an issue. species to live exclusively within a treatment wetland for it For example, the U.S. Department of the Interior (DOI) to be protected under ESA. If a species uses the habitat in constructed Kesterson Marsh for wildlife habitat during any way (resting, migration stopover, etc.), it is fully the 1970s). In the 198Os, selenium-laden drainage from covered. This is especially important because the new DOI-managed agricultural irrigation projects entered the habitat provided by constructed wetlands may attract marsh and caused deaths of waterfowl and shorebirds (see wildlife from their native range on a seasonal basis or for following case example on Kesterson Marsh). Advised of a specific purpose, e.g., feeding. Once endangered wildlife liability under the MBTA, then Secretary of the Interior or plants colonize or use the constructed wetland, liability Donald Hodel ordered Kesterson closed to the public, for their well-being conveys to the owner/manager. Of changed water management practices to stop inflow of particular interest is the potential for situations in which irrigation drainage, and implemented an elaborate hazing the wildlife species of concern do not use the wetland site program to scare birds away (Popkin, 1986; Zahm, 1986). directly, but feed on small rodents or other animals that However, hazing was not completely effective and some move off-site and carry their body burden of contami- bird poisoning--and liability-continued. Kesterson nants with them, for example, predatory birds and Marsh was eventually removed from the National Refuge mammals. System, drained and capped with uncontaminated soil, and At first glance, the likelihood of having endangered or managed by DOI as an upland site. threatened species in a treatment wetland may seem Kesterson Marsh was a large (5 18 ha) wetland designed remote. However, as the list of species grows, both at the to serve two purposes: treat (store and evaporate) irrigation federal and state levels, so does the potential for interaction drainage and provide wildlife habitat. These were not with constructed wetlands. This is particularly true in arid compatible functions. However, it does not take a and semiarid regions where wetland habitat is very scarce. Kesterson with its massive poisoning of wildlife for legal Moreover, water utilization policies have compounded the problems to occur. Treatment wetlands need not be problem in many locations. For example, since the late hundreds of hectares in size or intentionally provide 18OOs, Western U.S. water law has provided for agricultur- habitat to incur liability. Whatever size, shape, or primary al uses at the expense of in-stream flow and wetland function, treatment wetlands are all subject to the same preservation. The steady shrinking of wetland habitat has wildlife safety responsibilities conveyed by the MBTA. reached a critical point for many species, including several that are endangered and threatened. Constructed wetlands are a virtual oasis for wildlife in those situations (Lemly et ul., 1993) and it is not unrealistic to expect that sooner or In contrast to MBTA, the federal endangered species later the ESA will come into play. program has a relatively recent origin. Congressional As with MBTA, it is important to understand that legislation implementing the ESA dates only to 1973. creating treatment wetlands also creates liability for Two elements of the statute that have particular relevance wildlife exposure to contaminants. Endangered and threa- for constructed wetlands are: (1) to protect against killing tened animals and plants are an important consideration (intentional or unintentional) of listed endangered and within that exposure scenario. The legal implications 50 LEMLY AND OHLENDORF should be recognized and used to guide decisions during cultural irrigation wastewater (Zahm, 1986; Moore ct ai., the planning phase of wetland construction projects. 1990).

CASE EXAMPLE: KESTERSON MARSH Through the mid-1970s the San Luis Drain conveyed a mixture of operational spillage from valley water projects, The Kesterson Marsh episode has become a classic case agricultural surface runoff, and subsurface drainage. In for illustrating the dangers of selenium in treatment 1978 the proportion of subsurface drainwater increased, wetlands. That episode came about because of ambitious and by 1981 almost all of the flows discharged into agricultural water management plans coupled with a Kesterson Marsh were composed of subsurface drainage failure to recognize selenium as an environmentally generated by 3240 ha of irrigated agricultural lands in the hazardous constituent in wastewater. The series of events Westlands Water District (WWD) of the San Luis Unit that culminated in wildlife poisoning began in 1949, when (Zahm, 1986). In 1980--1981, samples of water from the the U.S. Bureau of Reclamation (USBR) submitted a drain and Kesterson Marsh were found to be saline and status report to Congress recommending additional water contaminated by selenium (15-400 ktg Se/L) (Saiki, 1986a). development for the (CVP) in The source of selenium was later determined to be natural California. The USBR also noted that because subsurface seleniferous soils in the WWD. Irrigation water dissolved soils on the west side of the San Joaquin Valley consisted of and leached selenium out of the soil as it percolated impervious clay that prevented deep infiltration of water, downward, and carried it to Kesterson Marsh in the continued intensive irrigation could lead to salt buildup resultant subsurface drainage. that would reduce crop production unless drainage systems Beginning in 1982, biological surveys were conducted by were installed to collect and convey return flows to the the USFWS to determine the extent and severity of Sacramento- Delta, San Francisco Bay, selenium contamination in aquatic food chains at Kester- and the sea (Moore et al., 1990). The first subsurface son Marsh (Saiki, 1986a,b; Hothem and Ohlendorf, 1989; drainage systems were installed in the 196Os, concurrent Schuler et NI., 1990). Extensive chemical analyses revealed with the construction of the San Luis Unit of the CVP that selenium concentrations were greatly elevated in the (Beck, 1984). Irrigation drainwater was dealt with on a water, detritus, and food organisms present in the piecemeal basis until the late 197Os, when the San Joaquin reservoir. Some of the highest concentrations of selenium Valley Interagency Drainage Program was formed to ever reported for fish tissues (37Obtg Se/g dry) were found review drainage needs for the valley. That program in these early studies. Aquatic invertebrates and forage fish recommended construction of a valleywide master drain contained from 1000 to 5000 times the concentrations of with a series of flow-regulating reservoirs to be operated as selenium present in the water, which indicated that wetlands for wildlife (SJVIDP, 1979). significant bioaccumulation was occurring. Elevated sele- The master San Luis Drain was originally designed to be nium concentrations were found in every animal group operated in conjunction with adjacent regulating reservoirs coming in contact with Kesterson Marsh, including fish, to seasonally discharge subsurface irrigation wastewater birds, insects, frogs, snakes, and small mammals (Saiki, into the river delta during periods of high outflow, thereby 1986a; Clark, 1987; Ohlendorf rt al., 1988b, 1990). High ensuring drainage water dilution. Kesterson Reservoir (a selenium concentrations were also found in food organisms series of 12 shallow ponds collectively known as Kesterson of predatory birds and endangered species such as the San Marsh) was the first regulating reservoir to be built (Moore Joaquin kit fox (Vulpcs macrotis rnutica). et NI., 1990). In 1970, the U.S. Fish and Wildlife Service Field studies indicated a high frequency (up to 65%) 01 (USFWS) and the USBR signed a cooperative agreement selenium-induced developmental deformities in the em- for management of Kesterson Marsh and associated bryos and hatchlings of waterfowl and other aquatic birds uplands. That agreement formally designated 2390 ha as nesting at Kesterson Marsh (Ohlendorf et ul., 1986a, 1989; Kesterson National Wildlife Refuge (NWR), and specified Williams et al., 1989). Congenital malformations were that the USFWS manage the area for wildlife and often multiple and consisted of missing eyes and feet, associated recreational values, but retained the right for protruding brains, and grossly deformed beaks, legs, and USBR to use the marsh for management of irrigation wings (Ohlendorf rt ml., 1986b, 1988a; HolYman et drainwater (Zahm, 1986). By 1972, only 132 km of the a/.,1988). Four species of ducks (mallard, Am/s phrtyr- intended 302 km of the master drain was finished, and h~wchos; pintail, A. acuta; cinnamon teal, A. cymoptcra; project funds was depleted. The 518-ha Kesterson Marsh gadwall, A. .strep,era), coot (Fuliccr umericunrr), avocet became the terminus of the drain, and its 12 shallow ponds (Recurvirostm anwricuncr), grebe (Podiqu nigricollisj, functioned as a treatment wetland for evaporating agri- and stilt (Nimrmtopus me.uicunuLs) were affected. Several SELENIUM IN CONSTRUCTED WETLANDS 51 pathological and biochemical symptoms of selenium rounding irrigation drainage. Second, using wetlands to toxicosis were also found in the adult wild birds (Ohlendorf treat agricultural irrigation drainage can set the stage for ct ul., 1988a). Estimates indicated that several thousand severe impacts to fish and wildlife. Bioaccumulation of birds were poisoned. selenium in aquatic food chains can lead to a variety of Other field studies documented a massive fish kill at reproductive impacts as well as selenium toxicosis in adult Kesterson Marsh in 1983 (Saiki, 1986a), followed by a high animals. Third, if treatment wetlands are contaminated by frequency (30%) of selenium-induced stillbirths in mosqui- selenium to the point that wildlife problems occur, tofish (Gcrmhusicr @t?is), the only fish species that managed aggressive cleanup will likely be necessary and it is to persist in the reservoir and the San Luis Drain (Saiki extremely expensive. This may more than offset perceived rt ml., 1991, Saiki and Ogle, 1995). or actual cost savings of the wetland treatment option when it was designed and implemented. Fourth, there are serious regulatory issues relating to the Migratory Bird Treaty Act and the Endangered Species Act that can come By 1985, selenium-induced death and deformities had into play. Violation of these and other laws may impose affected thousands of aquatic birds, and the “poisoned” severe penalties on the wetland owner. refuge became highly publicized (Marshall, 1985; Popkin, 1986). Threats of lawsuits against the Department of the PREVENTING PROBLEMS THROUGH ECOLOGICAL Interior, the federal agency with stewardship/ownership RISK ASSESSMENT responsibility for Kesterson, were voiced by several environmental groups and private citizens. Soon after the It is important for those considering wetlands as a toxic threat of contaminants in irrigation drainage was selenium treatment method to understand the ecological verified, then Secretary of the Interior Donald Hodel, citing risks. Many of the risks may not be obvious to project concerns over violation of the Federal Migratory Bird planners, particularly if there is no expressed intention for Treaty Act, officially closed Kesterson National Wildlife the wetland to provide wildlife habitat. Ecological risk Refuge to the public, began a hazing program to scare assessment provides an approach for characterizing pro- waterfowl and other wildlife away from the refuge, and posed treatment wetlands with respect to wildlife use, issued an order for the San Luis Drain to be plugged selenium contamination, and possible impacts. Proper (USGAO, 1987). By June 1986, all irrigation drainage application of this approach can reveal potential problems flows into Kesterson Marsh had stopped. In 1987 USBR and the associated liabilities, and form the basis for implemented a cleanup plan that called for drainage of the selection of an environmentally sound treatment option. wetlands, excavation and on-site disposal of contaminated Although it is beyond the scope of this article to give an soil and plant material in a lined and capped containment exhaustive detail of assessment procedures, a brief over- area, and long-term site monitoring to detect possible off- view is presented as a foundation from which the reader site seepage of selenium-contaminated water. The cost of can obtain additional information. the cleanup was about $US 50 million (1987 dollars) (USGAO, 1987; SJVDP, 1988). The lands constituting A ssrssm~w f Guidelines Kesterson Marsh were removed from the national refuge The USEPA (1992, 1998) has developed a “framework” system and placed under the jurisdiction of USBR for to serve as guidance for conducting ecological risk management as a contaminated landfill. To offset this loss assessments that are applicable to a wide range of potential of wetlands, some 9500 ha of private lands adjoining the ecological effects. The guidance is intended to provide a refuge was purchased and developed into waterSow and simple, flexible structure for conducting and evaluating upland wildlife habitat (USGAO, 1987; SJVDP, 1990). The ecological risks and to foster consistent approaches to total cost of mitigating selenium contamination at Kes- ecological risk assessment. This structure includes three terson was about $US 60 million (1987 dollars), not major steps called Problem Formulation, Analysis, and including the ongoing cost of long-term site monitoring, Risk Characterization (Fig. 2). which continues today. Some of the individual U.S. states as well as various other agencies also have developed guidance for conduct- Irnpliur t ions fbr Trcw trim 1 Wet lands ing ecological risk assessments. Although these guidance The lessons learned at Kesterson were painful but documents vary in specifics and may apply only to a valuable. First, it is essential to know the contaminants particular type of site or kind of facility, there are many in wastewater and their hazards to wildlife; selenium common elements among them. Following the USEPA surprised many of those involved with Kesterson but it framework guidance should help ensure that an ecological need not have. Information available at the time was risk assessment will address the important issues for a adequate to reveal the environmental safety issue sur- treatment wetland. 52 LEMLY AND OHLENDORF

FRAMEWORK FOR A WETLAND-SPECIFIC ECOLOGICAL RISK ASSESSMENT

PROBLEM FORMULATION: Management Issues Identify: management goals, policy drivers, regional issues, communication plan, resource needs, public input Wetland Characterization Determine: functions/values, wetland type, hydrology, geomorphology Stressor Identification Identify: chemical, biological, physical, contaminant Receptor Identification Identify: biotic, abiotic <

Modelling ANALYS*S: Exposure Assessment 4 Biological Assessment Ecological Assessment

FIG. 2. Various steps and components of the risk assessment process [or wetlands. (Adapted, with permission, from USEPA 1992).

The USEPA framework (1992, 1998) emphasizes the there must be one or more parameters that can be importance of discussion between the risk assessor and the measured and quantified. These have been referred to as risk manager (the person or persons who must decide how “Measurement Endpoints,” but the more recent USEPA to manage the site), especially at two times (Fig. 2). Early guidance (USEPA, 1998) has changed that terminology to discussions are important in ensuring that the risk “Measures of Exposure,” “Measures of Ecological assessment will focus on the questions about which the Effects,” and “Measures of.. . .” For example, a measure manager wants information, and that the manager under- of exposure for the first assessment endpoint listed above stands the limitations concerning how much information might be the concentration of selenium in food-chain the risk assessment is likely to produce. After the risk organisms found in the wetland; a measure of ecological assessment is completed, discussions between the risk effects could be the hatching success of aquatic birds assessor and the risk manager help to interpret the findings nesting at the wetland. For the second assessment and uncertainties related to them. The effectiveness of the endpoint, a measure of exposure might be the waterborne risk assessment usually increases in proportion to the concentrations of all potentially toxic chemicals in the clarity of communication between the risk assessor and risk wetland. manager.

Ecological Objectives Genual Orgmizntion and Content The objectives of an ecological risk assessment are The risk assessment report is usually organized to usually identified as “ecological endpoints” that are more provide information concerning problem formulation, or less subject to direct measurement. The overall exposure assessment, ecological effect assessment, and risk objectives (called “Assessment Endpoints”) are often characterization so it is consistent with the main activities not directly measurable, but are statements about the that are conducted in the assessment. Figure 2 provides a resources that are to be protected. Examples include: (a) schematic representation of the kinds of information that protect waterfowl populations from chemicals that could are typically included in each major section. However, bioaccumulate in the food chain, thereby potentially because of space limitations, the specifics are not described causing reproductive impacts in birds; or (b) maintain here in detail. Readers are referred to the USEPA the integrity of a wetland food chain that provides habitat framework (USEPA, 1992, 1998) or similar documents for aquatic birds. For each identified assessment endpoint, for further explanation. SELENIUM IN CONSTRUCTED WETLANDS 53 Phase II Phase III

Site Further Sampling to Dctcrminc Adverse Effects YCS Are Data NO CharactcrizaQl Ecological b I, Idkely ,o Occur? - Adequate for Risk + Bioasscssment and Screening ) Impairment Assessment?

No

Yes

Potentially Are Data Complete YCS Complete Risk - \ Adequate for Risk Assessment I:xposurc Assessment?L1 .I Pathways’! I I

a Review of availahlc information to identify chemicals, habitats, and rcccptors of concern and to screen chemical concentrations against available criteria, standards, or effect levels.

b In accordance with Data Quality Objectives, Rcld Sampling Plan, Quality Assurance Project Plan, and Health and Safety I'la~i; may include laboratory bioassays, tissue analysis, field studies for further definition of extent 01 conlamination or effects. etc.

NOTE: Arcas of concern, chemicals, cxpasurc pathways, and rcccptors arc evaluated independently so Lhal further evaluation is only to satisfy identified needs.

FIG. 3. Typical phased approach to ecological risk assessment.

Phused Approuch The chemical screening during this phase is conducted to: An important aspect of the approach to ecological risk l Compare chemical concentrations with established assessment is not to do only the necessary work, but to do criteria or standards and with ecological effect levels (if all of the work that is necessary (USEPA, 1992). This is criteria/standards have not been established) accomplished by conducting the work in a phased manner, l Evaluate potential bioaccumulation (especially for whereby the work completed in one phase helps to selenium and other persistent, bioaccumulative chemicals) determine whether further studies are required and, if so, specifically what additional information is needed. Figure 3 Phase I is a critical point in the evaluation of proposed shows this method of phasing the risk assessment for a treatment wetlands because it will likely be the step at wetland. Phase I is primarily the Problem Formulation, but which a decision is reached on whether to proceed with it includes some preliminary evaluation of exposure and construction. The risk assessor must formulate a prediction ecological effects. Phase II would be conducted in of future conditions based on current information from the accordance with a sampling and analysis plan developed site concerning selenium concentrations and wildlife use. after Phase I has been completed. If further data needs are Phase I may be all that is possible (or necessary) before identified after Phase II is completed, additional studies planners make a judgment on whether it is worthwhile, may be conducted as Phase III. from a risk perspective, to pursue the project further. In The Phase I site characterization would review available situations when existing treatment wetlands are being information to: evaluated, all three phases of risk assessment may be needed to assess risk under actual operating conditions. l Identify chemicals in water or soils at the proposed site When the Phase I site characterization and chemical l Describe habitats present or expected to develop in the screening have been completed, the question becomes “Is wetland more information needed to complete the risk assessment?” l Identify receptors of concern (such as aquatic birds, fish, There may be a generally inadequate amount of informa- fish-eating mammals, etc.) tion, or it may be limited to a particular exposure pathway 54 LEMLY AND OHLENDORF

or medium (such as selenium concentration in bird eggs). l Mortality or reproductive impairment documented Some risk analysis protocols for selenium require informa- through in .situ effects studies tion on several environmental matrices (e.g., water, l Teratogenic deformities found in combination with sediment, benthic macroinvertebrates, fish, birds). If the elevated tissue residues of selenium answer to the question is “Yes,” the next step is to develop There are several research reports and guidance docu- the study plan (or sampling and analysis plan) for ments available for interpreting selenium concentrations obtaining the additional information. and biological effects and evaluating risks to fish and Typical objectives for a study plan include: wildlife. The reader is directed to the following publications for more information: Hoffman et ul. (1988), Lemly l Further characterization for wildlife use (1993a,b, 1995, 1996, 1997b), Ohlendorf (1989), Ohlendorf l Determination of the exposure point chemical concentrations (including food-chain bioacccumulation) rt al. (1986a, b, 1988a, 1989, 1990), Skorupa and Ohlendorf (1991), Skorupa ~‘t ~1. (1996), NIWQP (1998). l Evaluation of specific direct or indirect effects of chemical exposure under site-specific conditions CONCLUSIONS The plan should include the data quality objectives (such as required sample sizes, detection limits for chemical The practice of using constructed wetlands to treat analyses, etc.) and the decision strategy/rationale that selenium-laden wastewater is gaining popularity in the includes: United States and elsewhere. In considering this type of treatment technology it is important to document the l Sample locations and methods selenium concentration of the wastewater, understand how l Chemical analyses it cycles and accumulates in the environment, and evaluate l Bioassays and bioaccumulation assessment the threat it may pose to fish and wildlife before deciding l /n sifu biological effects assessment whether to proceed with construction. It is also important to remember that constructing wetlands, even small ones, For selenium, measurement of bioaccumulation in the creates wildlife habitat and may lead to an exposure food chain is particularly important when the receptors of scenario that has strict regulatory penalties under various concern are fish or aquatic birds. Chemical analyses of the federal and state laws. Evaluating potential effects in water or sediment may be useful for evaluating exposure, wildlife should be an integral part of the planning stage for but extrapolation to effects in fish or birds are predictive treatment wetlands. Ecological risk assessment provides a rather than proven. This issue has been discussed elsewhere good framework for such evaluations, and the phased (e.g., Skorupa and Ohlendorf, 1991) and is not repeated approach allows an assessment to address site-specific here. needs. For selenium, it is essential to evaluate bioaccumu- The most important point about following this phased lation in the food chain to accurately assess risk. With this approach is that studies are conducted to satisfy specific information in hand, enviromnentally sound choices for information needs, and that the investigation can end as wastewater treatment can be made. soon as those needs are met. This avoids the potential for the project becoming one of “open-ended research” that REFERENCES continues to follow up on leads that may be of interest to the investigator but will not provide information that the Bean, M. J. (1986). The endangered species program. In A&r/m? W~/cil[/i~ risk manager needs for decision-making purposes. How- Report 1086 (R. L. Di Silvcstro, Ed.), pp. 347 ~371. Natl. Audubon ever, in some instances the Phase II or 111 studies are Sot., New York. essential for providing the needed information. Beck. L. A. (1984). Case history: San Joaquin Valley. c’cr/$ Agric,. 38, 16- 17. Clark, D. R., Jr. (1987). Selenium accumulation in mammals exposed to contaminated California irrigation drainwater. Sci. To/al &l?rort. Once data and information collection efforts are 66, 147 16X. completed, it is necessary to interpret the findings in the context of risks to fish and wildlife. Depending on the type of treatment wetland (proposed or existing) and specific needs of the assessment, this step may occur following Phase I, Phase II, or Phase III. Some of the primary indicators that can be used to determine risk include: Hansen, D., Duda, I’. J., Zaycd, A., and Terry, N. (1998). Selenium l Seleniuln concentrations exceeding hazard thresholds removal by constructed wetlands: Role of biological volatilization. (water criteria or biological effects levels for diet/tissue) Et~riror~. Sci. Tdvml. 32, 59 1 591. SELENIUM IN CONSTRUCTED WETLANDS 55

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