TABLE 5.1. Summary of definitions of impact intensities given in the DEIS. Definitions are effectively the same for some resource categories (wetlands, eelgrass, and wildlife and wildlife habitat) while others are specific to the resource category (special status species, coastal flood zones, water quality, and soundscapes).

Language Resource Category Minor Moderate Major
Common Across Categories Wetlands, Eelgrass, and Wildlife Localized, slightly detectable, no affect on community structure Clearly detectable; could appreciably effect individuals, communities or natural processes Highly noticeable, would substantially influence individuals, communities or natural processes
Resource-Specific Language Special Status Species Changes to an individual, population or critical habitat are possible Some changes to an individual, population, or critical habitat would result A noticeable change to an individual, population or critical habitat would result
Coastal Flood Zones Takes place in the floodplain or flood zone, no increase in potential flood damage to other areas (or is exempt from NPS floodplain management guidelines) Takes place within the floodplain or flood zone, would result in increased potential for flood damage to property or environmental contamination at the project site. Would have a measurable impact on potential flood damage or environmental contamination to the site and to adjacent & downstream properties
Water Quality Temporary and localized, may or may not be detectable, would not have long-lasting effects, & would be within historical or desired water quality conditions. Short- and long-term detectable impacts would change the chemical, physical, or biological integrity of water quality that would alter the historical baseline or desired water quality conditions Short-term and longterm detectable impacts would change the chemical, physical, or biological integrity of waters of Drakes Estero that would alter the historical baseline or desired water quality conditions.
Soundscapes Human-noise at a level that makes vocal communication difficult between people separated by more than 32 ft, and the natural soundscape is interfered with > 5% of the time. Human-noise at a level that makes vocal communication difficult between people separated by 32-16 ft, and the natural soundscape is interfered with 5-10% of the time. Human-noise at a level that causes vocal communication difficult between people separated by > 16 ft, and the natural soundscape is interfered with < 10% of the time.

The committee’s conclusions in Table 5.2 may be explained in part by the definitions of impact intensities used in the DEIS. For resource categories with common definitions for impact intensities across resource categories (Table 5.1; Appendix C), the committee found the definitions to be ambiguous and challenging to use for distinguishing among adverse impact levels. For example, a moderate adverse impact is characterized as having an “appreciable effect” that is “clearly detectable” while a major impact is characterized as having a “substantial influence” that is “highly noticeable.” In addition, adverse impacts are considered to be moderate or major if an individual organism is affected while an impact is considered to be minor if it has no affect on community structure. Does this mean that an impact on an individual organism may be considered to be moderate or major, but not minor? All impact intensities could be improved by clearly scaling the definitions in terms of their effects on individuals and populations within the Drakes Estero ecosystem as well as the community of populations that make up the biota of the ecosystem. Likewise, as discussed in Chapter 2, the scale of an impact may match the scale of the pressure (or source), or it may be on a much larger scale, e.g., the scale of Drakes Estero. However, adverse impacts that are judged to be minor are characterized as being “localized,” while definitions in the DEIS are silent on the temporal and spatial scales of moderate and major impacts. To provide distinct levels of impact, the definitions of impact intensities need to distinguish between impacts on the same scale as the pressure (e.g., direct impacts such as eelgrass scarring caused by propellers) and impacts on the larger scale of the Drakes Estero ecosystem (e.g., indirect impacts such as the dispersal of



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