Massachusetts (Cont.)

The Massachusetts guidance is of interest to dredged material disposal

activities because it explicitly defines background and allows a consideration of

local conditions in eliminating contaminants of concern from the risk assessment.

a. Background concentrations are those which are ubiquitous and

consistently present near the disposal site and are attributable to

geological or ecological conditions, atmospheric deposition of industrial

or engine emissions, fill materials containing wood or coal ash, releases to

groundwater from a public water supply system, and/or petroleum

residues that are incidental to the normal operation of motor vehicles.

Compounds which are consistent with background are not assessed

further.

b. Comparison to local conditions is another step which the guidance

recommends only for aquatic environments, specifically sediment and

surface water. Local conditions are levels of oil and/or hazardous material

present consistently and uniformly throughout the surface water body, or

throughout a larger section of a river that contains the area potentially

affected by contamination at or from the site. Hot spots and localized

contamination are not considered local conditions. Like background, local

conditions may be assessed on a chemical-specific basis. When

concentrations are consistent with local conditions, further assessment of

the risk posed by that substance in that medium may not be required.

In aquatic environments, the detection of elevated levels of contamination in

sediment or surface water, or the potential for elevated levels to occur in the future

constitutes identification of a complete exposure pathway. For any complete

pathway, effects-based screening is necessary in Stage I. For effects-based

screening levels, the guidance recommends National Oceanic and Atmospheric

Administration (NOAA) Effect Range Low) ER-Ls (Long et al. 1995) for

marine and estuarine sediment, Ontario Ministry of the Environment Guidelines

for freshwater sediment (Persuad 1993), and Ambient Water Quality Criteria

(AWQC) or Lowest Observed Effect Level (LOELs) (in that order) published for

surface water. For a Stage I screening for wetlands, again the complete exposure

pathways should be identified and then an effects- based screening should be

conducted. Note that the effects screening criteria are only for ruling out

pathways, not individual chemicals. If a pathway is not ruled out, risk from all

chemicals that result in exposure by that pathway should be evaluated in Stage II,

even if those substances are present at levels below their screening criteria.

The Stage II ecological risk assessment follows the general framework of

USEPA ecological risk assessment guidance. The process includes problem

formulation, analysis of exposures and associated ecological effects, and risk

characterization, which integrates exposure and effects analysis. Also, an

uncertainty analysis should be included in the risk characterization. The risk of

harm to the environment is characterized by comparing the concentration of each

oil or hazardous material to the upper concentration limits in soil and

A22

Appendix A Summary of Federal, State, and Regional Guidance