DECIDING WHEN TO INTERVENE

Abstract

The U.S. Army Corps of Engineers has statutory authority to regulate the disposal of dredged material in waters of the United States under the Clean Water Act and in the oceans under the Marine Protection, Research, and Sanctuaries Act. In carrying out this authority, the Corps has conducted over $100 million of research on dredging and the disposal of dredged material.

As required by domestic law and the International London Dumping Convention, the suitability of dredged material for open-water disposal is determined by an ecological effects-based approach rather than consideration of the concentrations of chemical contaminants in the sediment. The rationale for this is that dredged material is a complex mixture of many substances whose bioavailability and potential interactions cannot be predicted merely on the basis of the concentrations of the chemicals of concern.

This effects-based approach uses physical, chemical, and biological assessments, and consists of contaminant mobility/bioavailability modeling; acute toxicity bioassays, which address the benthic and water column environments; and contaminant uptake bioassays, which provide information on the potential for bioaccumulation. Risk assessment procedures are available for the more difficult projects. The procedures followed by the Corps in accordance with U.S. Environmental Protection Agency regulations have significant potential for the evaluation of sediment in general. However, it must be recognized that the disposal of dredged material is usually an instantaneous event (hopper, dredges, dump scows), or very short-term (hydraulic pipeline). Thus, acute, rather than chronic effects, are of primary concern. Chronic/sub-lethal tests will be available in the near future.

For further information on environmental effects of dredging, please see "Environmental Effects of Dredging Program Technical Notes" under "Publications" on the following web site: http://www.wes.army.mil/el/dots

The U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (Corps) have developed a regional testing manual for evaluating potential impacts of contaminants from dredged material proposed for discharge to the Great Lakes, connecting channels, and tributaries. This manual is intended to be used as a decision-making tool for dredge and fill permits issued by the Army Corps of Engineers, or States or Tribes where delegated, under Section 404 of the Clean Water Act. This guidance is consistent with the technical framework developed by the Corps and EPA for evaluating the environmental effects of dredged material management alternatives (USACE/USEPA 1992).

The Great Lakes Dredged Material Testing & Evaluation Manual utilizes a tiered approach for testing and evaluation, which is consistent with the national manuals developed for testing dredged material proposed for discharge in inland waters (USEPA/USACE 1998) and ocean disposal (USEPA/USACE 1990). This tiered approach is also generally consistent with the "Guidelines for Project Evaluation" developed by the International Joint Commission (IJC 1982).

The objective of the tiered testing approach is to make optimal use of resources in generating the information necessary to make a contaminant determination, using an integrated chemical, physical, and biological approach. To achieve this objective, the procedures in this manual are arranged in a series of tiers with increasing levels of intensity. The initial tier uses available information that may be sufficient for completing the evaluation in some cases. Evaluation at successive tiers requires information from tests of increasing sophistication and cost.

The most logical and cost efficient approach is to enter Tier 1 and proceed as far as necessary to make a determination. There are two possible conclusions that can be made at each of the first three tiers:

1. Available information is not sufficient to make a contaminant determination, or
2. Available information is sufficient to make a contaminant determination.

Where information is sufficient (conclusion 1), one of the following determinations may be reached:

• The proposed discharge will not have unsuitable, adverse, contaminant-related impacts, or
• The proposed discharge will have unsuitable, adverse, contaminant-related impacts

Tier 1 compiles existing information about the potential for contamination in the proposed dredged material. Disposal operations that are excluded from testing or have historic data sufficient for the contaminant determination may proceed to a determination without additional testing. The manual identifies sources of historical sediment data, lists industries and activities associated with sediment contamination, and provides examples of cases where testing is and is not needed.

Tier 2 evaluates the potential impacts of the proposed discharge on water column and benthic environments using sediment physical and chemical data collected for this tier, and applied with computer models to project worst-case conditions for water quality impacts and bioaccumulation. The manual provides detailed guidance on acceptable analytical procedures for physical and chemical analysis of selected parameters. Based on the results of Tier 2 evaluations, additional testing may be reduced or eliminated.

Tier 3 evaluates the potential impacts of the proposed discharge on water column and benthic environments using effects-based biological testing. The manual presents recommended procedures for biological-effects tests developed specifically for use in the Great Lakes Basin. The features of these tests are summarized below. Not all tests endpoints have been approved for Tier 3 application.

Species	Medium	Endpoint(s)	Test Duration (days)
Daphnia magna	Elutriate	Survival/Survival and Reproduction	2/21
Ceriodaphnia dubia	Elutriate	Survival/Survival and Reproduction	2/7
Pimephales promelas	Elutriate	Survival/Survival and Growth	4/7
Chironomus tentans	Sediment	Survival and Growth	10
Hyalella azteca	Sediment	Survival and Growth	10
Lumbriculus variegatus	Sediment	Bioaccumulation	28

Tier 4 is only entered if the information provided by Tiers 1 through 3 is not sufficient to make a contaminant determination. The procedures used in Tier 4 are keyed to site specific issues not resolved by the standardized procedures of earlier tiers. It is intended that very few situations will require a Tier 4 evaluation.

With this tiered testing structure, it is not necessary to obtain data for all tiers to make a contaminant determination. It may also not be necessary to conduct every test described within a given tier to have sufficient information for a determination. The underlying philosophy is that only that data necessary for a determination should be acquired.

The Great Lakes Dredged Material Testing & Evaluation Manual is available to download from the following web site:

References

International Joint Commission (IJC). 1982. Guidelines and Register for Evaluation of Great Lakes Dredging Projects. Report of the Dredging Subcommittee to the Water Quality Programs Committee of the Great Lakes Water Quality Board. Windsor, Ontario.

USACE/USEPA. 1992. Evaluating Environmental Effects of Dredged Material Management Alternatives - A Technical Framework. EPA842-B-92-008, Washington, D.C.

USEPA/USACE. 1998. Evaluation of Material Proposed for Discharge to Waters of the U.S. - Testing Manual (Inland Testing Manual). EPA-823-B-98-004, Office of Water, Washington DC.

USEPA/USACE. 1990. Ecological Evaluation of Proposed Discharge of Dredged Material Into Ocean Waters. EPA-503-8-90/002, Washington DC.