DECIDING WHEN TO INTERVENE

A central tenet to rehabilitating sediment quality and renewing ecosystem health is that control of contaminants at their source remains the primary imperative for action. It can only be through the cessation of inputs of contaminants from sources that other sediment management actions such as sediment removal can be economically viable, ecologically successful, and sustainable.

The Imperative: Restoring Beneficial Uses

According to Annex 2 of the Great Lakes Water Quality Agreement, the purpose of RAPs is the restoration of beneficial uses. Contaminated sediment potentially poses a challenge in restoring 11 of the 14 beneficial use impairments identified in the Great Lakes Water Quality Agreement (SedPAC 1997). Therefore, decisions regarding sediment management actions in Areas of Concern should be tempered and driven by the goal of restoring beneficial uses.

Indicators are measurable features which provide communities, scientists, and resource managers with useful information on the state of the ecosystem, environmental quality or trends, and the status of programs and activities directed at rehabilitating the Great Lakes ecosystem. Indicators measure progress toward community-based and/or government-driven management goals. If the goal of RAPs is restoration of beneficial uses, then indicators of a successful sediment management strategy should include progress toward restoration of beneficial uses.

In general, sediment management can be viewed as either activities or outcomes. Sediment management activity indicators include issuance of permits by governments, control of contaminants at their source, and sediment remediation. Outcome indicators can include environmental responses such as changes in fish and wildlife populations and human health risk (Table 1). Therefore, sediment management can and should be evaluated against a spectrum of indicators ranging from programmatic activities to ecosystem outcomes.

It must be recognized that there are considerable interrelationships among sediment management indicators and use impairments (Table 1). There can also be a temporal factor in restoring certain use impairments. For example, a sediment management activity like dredging and disposal will have an immediate impact on sediment chemistry. However, the effect of this same sediment management activity on liver tumors in fish and consumption advisories may not occur for several to many years later. Such interrelationships and temporal sequencing must be understood and considered in the assessment of sediment quality, data interpretation, and final sediment management decisions.

In general, the highest order and most important indicators in the context of restoring beneficial uses are seen as the ones that represent ecosystem outcomes. The WQB has called for a step-wise and incremental approach to management of contaminated sediment and restoration of beneficial uses (SedPAC 1997). Sediment remediation, removal of a mass of contaminants, and reduction of risk are important indicators of incremental progress. The ultimate success of sediment management activities will be judged upon restoration of beneficial uses (e.g., elimination of fish consumption advisories, restoration of fish and wildlife populations, restoration of benthos).

Table 1. The interrelationships among sediment management outcome indicators and use impairments as defined in the Great Lakes Water Quality Agreement (GLWQA)

INDICATOR OR MEASUREMENT	USE IMPAIRMENTS MOST CLEARLY ADDRESSED (As defined in Annex 2 of GLWQA)	RELATIVE TIME SCALE* FOR RESTORATION OF BENEFICIAL USES
Improvements in sediment chemistry	Restrictions on dredging activities, added costs to agriculture and industry, degradation of aesthetics, eutrophication or undesirable algae	Short-term
	Degradation of phytoplankton or zooplankton populations	Short-term to intermediate
	Degradation of benthos, loss of fish and wildlife habitat	Intermediate to long-term
Improvements in toxicity in sediment bioassays (invertebrates)	Eutrophication or undesirable algae	Short-term
	Degradation of phytoplankton or zooplankton populations	Short-term to intermediate
	Degradation of benthos, loss of fish and wildlife habitat	Intermediate to long-term
Improvements in benthic invertebrate community structure	Degradation of benthos, loss of fish and wildlife habitat, degradation of fish and wildlife populations	Intermediate to long-term
Decline in bioaccumulation and biomagnification	Loss of fish and wildlife habitat, degradation of benthos, fish tumors or other deformities, bird or animal deformities or reproductive problems, restrictions on fish and wildlife consumption	Intermediate
	Degradation of fish and wildlife populations	Intermediate to long-term
Improvements in vertebrate populations and communities	Eutrophication or undesirable algae, fish tumors or other deformities, bird or animal deformities or reproductive problems	Short-term to intermediate
	Loss of fish and wildlife habitat, degradation of fish and wildlife populations	Intermediate to long-term
Decline in risk to human health	Restrictions on fish and wildlife consumption	Intermediate to long-term

* Relative time scale: Depending on the degree of degradation, even a short-term time scale can span months to years. Subsequent response times would then be relative to achieving the earlier indicators of improved ecological conditions.

It is generally accepted that progress in sediment management should be measured by a broad spectrum of indicators. However, it must be recognized that there are considerable interrelationships and temporal complexities among sediment management indicators and the 11 beneficial use impairments potentially affected by contaminated sediment (Table 1). As a result, it is easy to understand why there is no simple approach to applying data interpretation tools to make sediment management decisions.

Considerable work has been undertaken to identify beneficial use impairments in Areas of Concern. This extensive effort to identify the status and cause of impairments provides a good foundation to guide sediment management decisions. To rehabilitate an Area of Concern, linkages between contaminated sediment and known use impairments must be considered (Figure 1). In many cases, the information needed to make the connections has been collected by assessing chemistry, benthic community structure and composition, laboratory toxicity, contaminant bioaccumulation/ biomagnification, and sediment/site stability.

If contaminated sediment is not causing or contributing to any use impairments, and site stability is clearly known to be high, then regardless of sediment chemistry, no sediment management actions are recommended beyond routine monitoring (and pollution prevention). However, if the data link contaminated sediment to one or more use impairments, and site stability cannot be ensured, then it is recommended that an intensive assessment of the quantitative relationships between contaminated sediment and use impairments be undertaken.

Figure 1. A generalized flowchart which can be used to help make a sediment management decision regarding whether or not to take action beyond source control.

How to Best Interpret the Data

Equally important to the collection of data is that sufficient attention be placed on thorough and comprehensive interpretation of the data. By employing scientifically sound methods of data interpretation, the information from an intensive sediment assessment can finally be integrated to make a decision to intervene (i.e., remediate contaminated sediment) or pursue source control and natural recovery as the preferred remedial option. A variety of data interpretation tools are available to make a decision (Table 2).

By way of example, a recently well-received approach could be used consistently across jurisdictions to determine the significance or severity of benthic community structure data or laboratory toxicity results (see Appendix 5). Reference conditions can be defined using an array of reference sites for comparison with test site data using multivariate methods. A reference site database is used to predict the structure of the benthic invertebrate community or the response of bioassay species for a test site. The test site's potential for a certain faunal community or bioassay endpoint can be based on variables that are least affected by anthropogenic impacts (e.g., geographic location, particle size distribution, major elements, etc.). The distribution of the reference sites provides the range of variation in unimpaired communities. The community at the test site can then be compared to this normal variability. The greater the departure from the reference sites, as measured in ordination space, the greater the certainty of environmental effects resulting from contaminants.

The consensus among community-based and agency RAP practitioners is that consistent application of sediment assessment and data interpretation methods across the regions is desirable (i.e., collect and interpret data similarly across Areas of Concern). Site specificity, however, remains important in applying tools due to local conditions, constraints, and nature of the chemical contamination.

To ensure that sediment management decisions consider restoration of beneficial uses in a comprehensive manner, one could also use a checklist in making a sediment management decision beyond source control. These key elements are presented and related to relevant data interpretation tools in Table 3.

Table 2. A matrix of data interpretation tools and references for making a sediment management decision beyond source control to restore beneficial uses as defined in the Great Lakes Water Quality Agreement

Use Impairment	Assessment Element	Data Interpretation Tools	Reference
Restrictions on fish and wildlife consumption	Bioaccumulation	Equilibrium partitioning, comparison to guidelines	Appendices 6, 7, 10, 12, and 14; Beltran and Richardson (1992)
Degradation of fish and wildlife populations	Community structure, bioaccumulation	Food web model, weight of evidence	Appendices 6, 12, and 14; Beltran and Richardson (1992)
Fish tumors or other deformities	Bioaccumulation, chemistry	Reference frequencies	Baumann (1992); Baumann et al. (1982)
Bird or animal deformities or reproduction problems	Bioaccumulation, community structure	Food web model, comparison to reference conditions, weight of evidence	Appendices 6, 12, and 14; Beltran and Richardson (1992)
Degradation of benthos	Community structure, toxicity (bioassays)	Comparison to reference conditions	Appendices 4, 5, 9, 10, 12, and 14
Restrictions on dredging activities	Chemistry, toxicity (bioassays) , stability*	Comparison to guidelines and/or reference conditions	Appendices 3, 8, and 10; U.S Army Corps of Engineers web site (www.wes.army.mil/el/dots)
Eutrophication or undesirable algae	Chemistry, stability	Modeling	Gore & Storrie, Ltd. (1991); Pennsylvania DEP's "The Lake Model" (1998)
Degradation of aesthetics	Chemistry, stability	Comparison to reference conditions	Heidtke and Tauriainen (1996)
Added costs to agriculture or industry	Chemistry, stability	Comparison to reference conditions	Park and Hushak (1998); Ontario MOE and Michigan DNR (1991)
Degraded phytoplankton and zooplankton populations	Bioaccumulation, chemistry, stability	Comparison to reference conditions, target nutrient loads	Bierman et al. (1983)
Loss of fish and wildlife habitat	Chemistry, bioaccumulation, toxicity, benthos, stability	Comparison to reference conditions, weight of evidence	Appendices 6 and 12; Minns et al. (1996)

*physical sediment characteristics, quiescent vs. energetic site characteristics, etc.

Table 3. A checklist of key elements to consider in making a sediment management decision beyond source control.

ASSESSMENT ELEMENT	REFERENCE FOR FURTHER INFORMATION
Characterization of the nature and extent of chemical contamination	Appendix 3, 5, and 9; IJC (1987); IJC (1988)
Measurement of toxicity endpoints (lethal and sublethal chronic effects)	Appendix 4, 5, 9, 10, 13, and 14
Assessment of bioaccumulation/biomagnification potential	Appendix 10, 12, and 14
Characterization of benthic communities	Appendix 5, 9, 10, and 12
Evaluation of the nature and extent of fish tumors and abnormalities	Appendix 12
Assessment of human health risk from sediment contamination	Appendix 7 and 14
Assessment of wildlife risk from sediment contamination	Appendix 6, 12, and 14
Assessment of fish and other aquatic life risk from sediment contamination	Appendix 14
Evaluation of the physical stability of contaminated sediment deposits (i.e., Would a storm scour the sediment from the river resulting in a pulsed loading of contaminants to the lake?)	Beltran and Richardson (1992); U.S. EPA (1993); Lick (1992); and Cardenas and Lick (1996)
Determination of control of contaminants at source (i.e., have upstream sources of contamination also been controlled/ terminated?)	IJC (1987)

The data interpretation tools presented in Table 2 and the checklist in Table 3 have been developed to help make a decision regarding whether the scientific evidence warrants consideration of taking action beyond source control. It is beyond the intent of this report to address how decisions are tempered by factors other than the science-based tools discussed above. Once a decision has been made to intervene, however, those as well as the following additional elements require attention:

• engineering factors (e.g., technical feasibility, contaminant reduction, permanence of remedial options like capping, in situ treatment, dredging and disposal, etc.);
• economic factors (e.g., cost effectiveness, economic benefits);
• social factors (e.g., public acceptance, partners' opinions, adherence to public use goals, conflicting actions); and
• long-term monitoring considerations.