limited in scope (e.g., turbidity, suspended organic matter, nutrient concentrations, phytoplankton biomass). Thus, the committee disagrees with conclusion (1).

In contrast to this review in the Atkins report, the committee determined that an alternate conclusion on the overall impact of DBOC operations could be reached, with the beneficial effects of shellfish filtration outweighing the adverse impacts from sediment disturbance and the low levels of contaminants generated by DBOC activities.

Soundscapes (p. 81-86)

The Atkins review concluded that the scientific interpretation and analyses in the DEIS are reasonable, supported by the available data, and adhere to standard techniques and metrics. The committee agrees with the following comments made in the Atkins review:

  • The section on basic acoustics and concepts was well written and comprehensible to a broad audience (with the exception that the definition of dBA was incorrect);
  • The DEIS provides a good review of the effects of noise on wildlife “basic life functions” referencing key papers. Several new studies have emerged in the last two years that point to more evidence that noise negatively impacts wildlife;
  • There is evidence that noise detracts from a positive park visitor experience and noise generated by DBOC activities negatively affects the human wilderness experience;
  • Noise maps (spatial-temporal) of DBOC sound sources would be beneficial for explaining impacts on human and wildlife acoustic space;
  • Alternatives B and C are likely to have the same level of impacts on soundscapes; and
  • More supporting information is needed for assumptions about nighttime versus daytime ambient noise and propagation.

The committee disagrees with the following conclusions of this section of the Atkins report:

  • The evidence presented in the DEIS is “robust.” The committee concludes that the acoustic data, which were collected for other purposes, are not adequate to provide information on (1) spatial-temporal natural sounds, and (2) DBOC levels of noise from various activities and other transient human-related sounds (e.g., air flights, kayakers, etc.).
  • L50 is an adequate measure of noise. L50 does not capture high and low extreme values of the amplitude of noise to provide adequate context (range and variability) of noise sources. To characterize the statistical properties of noise in a given environment, a number of measures should be presented.
  • Table 3-3 of the DEIS “shows noise level values within close proximity to DBOC noise sources.”1 In reality, several of these values are reported from a 1995 study (Noise Unlimited, Inc., 1995). Apparently, the Atkins reviewer misinterpreted these as in situ data. Table 3-3 data are not from DBOC noise sources at the site and may not be representative of DBOC sound sources.
  • The committees disagrees that there is sufficient evidence presented to conclude that alternatives B and C have “major” impacts (Atkins, p. 85). The committee disagrees with the statement that alternative D would have a “greater” (Atkins, p. 85) impact on soundscapes than alternatives B or C. For example, a new building could be constructed to reduce noise from onshore DBOC operations and mitigation measure are available that could reduce noise associated with motorboat activity.

The committee identified additional shortcomings in the DEIS that were not mentioned by this review, including a lack of underwater soundscape assessments (underwater acoustic data collection). Also, the Atkins review did not mention that additional relevant information was available in the Volpe (2011) study that was not included in the DEIS analysis.

__________________

1 DEIS, p. 204.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement