CHAPTER 5

Conclusions

Overall Assessment of Conclusions Presented in the DEIS

Across the eight resource categories reviewed by the committee, the most common concern that arose was the lack of an assessment of the level of uncertainty associated with the scientific information on which conclusions were based. An assessment of the level of uncertainty, based on the availability and quality of data and level of scientific consensus on interpretation, is a key component of communicating scientific findings to decision makers (NRC, 2007).

The DEIS provides definitions of impact intensities for each resource category, as recommended in NPS Directors Order 12, to guide analyses of the severity of impacts and magnitude of change. Hence, the intensity definitions are integral to the conclusions on level of impact. In this DEIS, only one category of beneficial impact is used, such that effects that may range from minor to major beneficial could not be distinguished. In contrast, adverse definitions are described as minor, moderate, and major in the DEIS (Table 5.1). The DEIS did not include negligible as an impact level, although negligible impact is a useful category provided in the examples for the NPS NEPA guidance document “Summary of Regulations and Policies — Impact Indicators and Criteria,” Director’s Order 12.¹ In some cases, the committee concluded that an impact on a resource category could most accurately be described as negligible.

The scientific literature on Drakes Estero is not extensive and research on the potential impacts of shellfish mariculture on the Estero is even sparser (NRC, 2009). Consequently, for most of the resource categories the committee found that there is a moderate or high level of uncertainty associated with impact assessments in the DEIS. The committee estimated the level of uncertainty using the criteria described in Chapter 3 (Table 5.2). Only three impact assessments were considered by the committee to have a low level of uncertainty and these were for three special status species (Myrtle’s silverspot butterfly, California red-legged frog, and California least tern) for which no alternative conclusions were identified. Impact assessments for harbor seals, the coastal flood zone, water quality, soundscapes, and socioeconomics were all considered to have a high level of uncertainty, and the committee determined that alternate conclusions could reasonably be reached for these (Chapter 3). Eight of the remaining 16 categories were assigned moderate levels of uncertainty, and for these the committee determined that there could be reasonable, equally scientific, alternate conclusions for impact intensity.

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¹ Available at: http://www.nature.nps.gov/protectingrestoring/do12site/tabs/tab22.htm.

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).

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

propagules). The definitions do not provide distinct criteria for assessing the temporal and spatial scale of the impact, and hence limit the effectiveness with which the DEIS conveys the impacts of DBOC operations on the Drakes Estero ecosystem and its natural resources.

TABLE 5.2. Summary of impact intensities from the DEIS and the committee’s assessment of the analyses and conclusions reached in the DEIS for each resource category. Level of uncertainty for each resource category, as estimated by the committee, is indicated by a white dot (low uncertainty), gray dot (moderate uncertainty) or black dot (high uncertainty); the level of uncertainty applies to conclusions reached in the DEIS and by the committee. For additional details see Chapter 3.

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² Since Drakes Estero does not contain the habitat required for leatherback turtles, this resource category is not included here.

TABLE 5.2. CONTINUED

In addition, the committee found that the relationship of impact intensities across resource categories was not well articulated. For example, impacts on eelgrass habitat across alternatives B, C, and D were classified as “moderate,” while impacts on the fish species utilizing eelgrass habitat were determined to be “minor.” Similarly, soundscape impacts were identified as “major” for alternatives B, C, and D, while impacts on birds and harbor seals that would be affected by that soundscape were defined as “moderate.”

The committee’s concerns with definitions that are specific to each resource category (Table 5.2) can be summarized as follows:

• Special-status species: Impacts may be minor, moderate or major even if only one individual in a population is affected. Also, an impact is considered to be moderately adverse if some changes are detected, but major if changes are noticeable. Because the difference between “detectable” and “noticeable” is unclear, the distinction between moderate and major is unclear.
• Coastal flood zones: No distinction is made between flood zones and the flood plain. The distinction between “moderate” and “major” seems to be that a moderate impact is confined to the project site while a major impact includes the project site and beyond. Is “project site” synonymous with “project area”? For “minor,” is there an increase in flood risk at the project site? What is meant by “other areas”?
• Water quality: Impacts classified as minor may not be detectable, which would correspond to a negligible impact from the committee’s perspective. While a minor impact is defined as a local

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³ Since Drakes Estero does not contain the habitat required for leatherback turtles, this resource category is not included here.

⁴ Surplus refers to the net value of the commodity or service. For a producer, this value would be equivalent to profit (sales minus expenses). For a consumer, this represents the difference between the value of the item (e.g. what the consumer would be willing to pay) and the cost of the item.

• occurrence, the corresponding moderate and major impacts are not well defined in terms of scale. Moderate and major impacts appear to be on an ecosystem scale, but this is not clear. Additionally, the definitions for “moderate” and “major” impacts are identical in the DEIS. Quantitative indicators of water quality are not specified as they are for many estuaries in the U.S. This raises several questions: What is meant by “detectable”? What attributes of “chemical, physical or biological integrity” need to be changed and by how much? Assuming historical baselines are not available, what are the desired water quality conditions as quantified by accepted indicators of water quality (turbidity, chlorophyll-a concentration, nutrient concentration, etc.)?

• Soundscapes: Adverse levels of impact are based on distance between people communicating (minor by >32 ft, moderate by 16-32 ft, and major by <16 ft) and the proportion of time the soundscape is interfered with (5%, 5-10%, and >10%). The basis for these thresholds are not specified and do not appear to be based on scientifically established criteria. The adverse impact categories presented by the NPS, while useful in the sense of providing clear, readily measureable criteria; do not address the impacts of anthropogenic sounds on wildlife. Criteria that evaluate the responses of wildlife, as well as humans, to various sound sources would provide a more comprehensive assessment of this potential environmental impact. However, because sensitivities to sound vary among species, simple numerical measurements of sound levels would not be sufficient for assessing impact.

Suggestions for DEIS Revisions and Reducing Uncertainty in the Conclusions

The following comments are based on the committee’s review of the scientific foundation of the DEIS and should not be interpreted as a conclusion that the DEIS does not meet NEPA requirements. As discussed in Chapter 2, determination of the sufficiency of the DEIS to meet NEPA requirements was not part of the committee’s statement of task.

Recognizing that the final EIS will be issued based on currently available information, the committee provides the following suggestions for consideration in revising the DEIS:

• Re-define levels of impact intensity using criteria that clearly distinguish levels of impact (negligible, minor, moderate and major) that are comparable across levels (e.g., direct and indirect impacts; impacts at individual, population and community levels of organization).
• Qualify each impact intensity conclusion in terms of levels of uncertainty such as those used by the committee.
• Clearly identify and explain all assumptions made in reaching conclusions concerning impact intensities.
• Describe potential alternate conclusions as appropriate (e.g., Table 5.2).
• Segregate impact assessments for alternative A from alternatives B, C, and D and indicate that the assessments are not comparable due to use of different baselines.
• Use all relevant and available information, especially for water quality and soundscapes, such as additional measurements reported in Volpe (2011); analyze sound levels based on both dBA and unweighted values across a wide frequency range; and consider duty cycles when estimating the fraction of time DBOC activities impact the soundscape.
• Additional mitigation options could be included as possible permit conditions for the action alternatives to reduce impacts, e.g., an option to cease the culture of Manila clams would address some concerns about the establishment of that non-indigenous species in Drakes Estero; impacts of many DBOC practices (i.e., boat use, culture species and techniques, marine debris, soundscape effects) could potentially be reduced by the implementation of appropriate mitigation measures.
• Assess impacts associated with the potential establishment of non-indigenous species as a separate category.
• Provide greater consideration of the potential influence of climate change on DBOC operations and their associated impacts, e.g., rising sea level over the next 10 years could influence the spatial extent of inundation, potentially impacting resource categories such as vegetated tidal

• wetlands and the coastal flood zone (NRC, 2012); geographic ranges of warm water marine species are already extending poleward (e.g., Sorte et al., 2010; Doney et al., 2012), a trend that could exacerbate problems associated with invasive non-indigenous species, including increasing the potential for establishment of reproductive populations of the nonnative Pacific oyster in Drakes Estero.

The committee found that many of the impact assessments for the resource categories were limited by a lack of scientific information, resulting in moderate to high uncertainty in the conclusions. Although the feasibility of gathering new data within the given time constraints may be limited, the committee identified the following approaches for reducing scientific uncertainty in the DEIS:

• To the extent feasible, monitor how frequently boats are used for both bag and rack culture relative to stage of tide, motor boat routes relative to the distribution of seagrass beds and harbor seal protected areas, and more details on how the balance between bag culture and rack culture has changed from year to year and may change in the future (acreage used, location and production).
• Document the air and underwater soundscape, including evaluation of both natural and anthropogenic noise sources.
• Apply scientific methods to the assessment of socioeconomic impacts. Consider the use of qualitative modeling techniques to integrate across environmental, fishery, and socio-economic information.
• Assess the abundance and distribution of native and non-indigenous benthic invertebrates (infauna, epifauna, sessile and mobile species on hard, soft, and biological surfaces).
• Develop more accurate estimates of the seasonal flushing rate in the culture areas and use those for developing simple models of the contribution of cultured shellfish to water quality and food resource competition.
• Conduct a rigorous and comprehensive analysis of aerial photographs to resolve uncertainty in issues such as eelgrass extent and change, bag and rack culture area, and propeller scarring and other disturbance effects on eelgrass.
• Measure temporal (day/night) and spatial variability (distance from sources) within Drakes Estero using unweighted measures of ambient and source sound levels.

In Drakes Estero, as in many highly valued coastal areas, sustained monitoring of key variables (e.g., water quality parameters such as current velocities, temperature, salinity, dissolved nutrients, phytoplankton biomass, suspended organic matter, attenuation of downwelling radiation, and turbidity; abundance and distributions of benthic fauna, fish, birds, harbor seals, and non-indigenous species; extent and condition of eelgrass beds and tidal marshes) would reduce the uncertainty of impact assessments. These types of monitoring programs have been established through programs such as the National Estuarine Research Reserve System and the Integrated Ocean Observing System. Monitoring data on some of these key variables would inform adaptive, ecosystem-based management of the impacts of human uses on soundscapes, water quality, benthic habitats, biodiversity, and living resources in Drakes Estero.