Letter - R5 Page

Transcription

1 Page 18 Response to Comment R5-70 The salinity impacts resulting in a shift to a brine fly- and brine shrimpbased ecosystem have already been described. It is not known if the decreased loads (but selectively increased input concentrations) of toxic constituents will result in significantly changed surface sediment concentrations. Sediment exposure to the food chain (through invertebrates to birds) will change, in general, with the changing invertebrate community. The possibility that more surface sediments will be resuspended should not change the sediment exposure routes in the near-shore littoral regions. In particular, as the sea shifts to a brine fly dominance, the larvae and pupae will aggregate in extremely shallow shoreline environments which are always wave washed and turbid. Project impacts that may cause enhanced mid-water sediment concentrations should have no significant effect on that nearshore community. Response to Comment R5-71 The Draft EIR/EIS has been revised to more specifically address effects to double-crested cormorants from reductions in the water surface elevation of the Salton Sea. These revisions are found in this Final EIR/EIS in subsection under Section 4.2, Text Revisions. In addition, the revised Salton Sea Conservation Strategy would avoid accelerating exposure of nesting/roosting features and changes in fish abundance. See the Master Response for Biology Approach to Salton Sea Habitat Conservation Strategy in Section 3 in this Final EIR/EIS. Response to Comment R5-72 As described in responses to comments R5-67, R5-68, and R5-70, the best available data do not suggest that a shallower Sea will result in enhanced sediment resuspension (over its already well-mixed state) or that enhanced mixing (should it occur) will act to enhance toxicity from sediment-associated chemicals. A future Sea dominated by brine shrimp feeding on midwater algae and brine flies feeding in extreme shoreline algae mats would not be expected to be significantly affected by sediment-bound toxins in the water column

2 Response to Comment R5-73 Areas currently used by snowy plovers for nesting will become farther removed from the water as the water surface elevation of the Salton Sea declines. A decline in the water surface elevation is projected to occur under both the Proposed Project and the No Project alternative. Thus, to the extent that distance to water influences suitability of breeding sites for snowy plovers, existing nesting areas will become unsuitable under both the Proposed Project and the No Project alternative and therefore is not an impact attributable to the Proposed Project. The commenter suggests that at a reduced sea elevation, near shore areas will be too steep to be suitable for snowy plover nesting. Bathymetric data show a general pattern of increasing acreage of shallow sloped areas with declining surface elevation (see response to comment G25-82). At most of the lower elevations, the amount of shallow sloped areas (as indicated by acreage less than 1 foot) is greater than at the current elevation. This information suggests that suitably sloped areas would be available for snowy plovers at lower elevations. Impacts of the Proposed Project are assessed relative to the No Project alternative. As described under the No Project alternative, snags in the Salton Sea that are currently surrounded by water would no longer be surrounded by water as the water surface elevation declines. Herons and egrets could abandon use of snags as nesting and roosting sites when they are no longer surrounded by water. This effect could occur under both the No Project and the Proposed Project, the only difference being that it could happen 3 years earlier under the Proposed Project. Thus, the potential for abandonment of snags as nesting and roosting sites is not a consequence of the Proposed Project and therefore is not considered a significant impact of the Proposed Project. Further, herons and egrets are known to nest in snags and trees that are not surrounded by water (Kaufman 1996; Shuford et al. 2000), suggesting that birds may continue to use snags at the Salton Sea when they are no longer surrounded by water. Finally, with implementation of the Salton Sea Conservation Strategy, the acceleration of exposure of nesting/roosting sites would be avoided. See the Master Response on Biology Approach to Salton Sea Habitat Conservation Strategy in Section 3 in this Final EIR/EIS

3 Page 19 Response to Comment R5-74 There is no reason to expect that basic processes of uptake and precipitation that serve to limit water-borne selenium concentrations in the Sea will be significantly altered by the projected increase in salinity. Selenium that enters the Sea is quickly reduced to selenite and incorporated into fine sediments and settled biomass (Setmire and Schoeder 1998). Such bacterial reduction processes will not be eliminated by projected increases in selenium. In fact, selenium loss in saline evaporation ponds has been specifically attributed to salinetolerant algae populations (Fan and Higashi 1998). In addition, the biomagnification that occurs in current Salton Sea biota (Setmire and Schroeder 1998) would be reduced in a future, more limited ecosystem by the elimination of a fish-based food chain. Bird exposures should be reduced by the shift to an all-invertebrate diet of lowered average tissue selenium concentrations (as compared to predatory fish tissues). Response to Comment R5-75 The bathymetric data are not accurate enough to precisely predict the amount of shallow water habitat in the 4-15 cm depth range. However, they do reasonably predict changes in the amount of habitat of less than 1 foot depth, some of which would be in the 4-15 cm range preferred by shorebirds. The area less than 1 foot deep provided an index of the possible dynamics of shallow water habitat and constituted the best available quantitative information. The amount of shallow water habitat (< 1 foot deep) would increase under the Baseline from 1,143 acres at an elevation of -227 ft msl to about 3,600 acres at -235 ft msl. The Proposed Project would show a similar pattern. Although the perimeter of the Sea would decrease to 83 miles, the amount of shallow water habitat would increase to about 3,200 acres at -246 ft msl. The bathymetry analysis indicates that both the Baseline and Proposed Project would increase the amount of shallow water/mudflat habitat to a similar degree relative to existing conditions. There is no indication that there will be a net loss of shallow water/mudflat area under either the Baseline or Proposed Project conditions. Existing shallow water/mudflat habitat could be lost or reduced in certain areas as the Sea recedes. These existing areas would be lost at 5-346

4 Response to Comment R5-75 (continued) the same rate under the Proposed Project and No Project alternative. Also, under both alternatives, new areas of shallow water/mudflat habitat would also be created at lower elevations. As the shallow impounded areas at the southern and southeast side of the Sea are lost due to elevation declines, new shallow impounded areas will likely be created either in the vicinity or in other areas of the Sea. Conversion of drains into gravity-flow systems will allow water from the drains to flow naturally to the Sea. The drains likely would create "minideltas" at each outlet as the water spreads out and meanders to the Sea. Foraging habitat for shorebirds could improve under this situation by (1) an increase in the amount of shallow water/mudflat habitat, and (2) creation and maintenance of lower salinity areas where a greater diversity of invertebrates can persist. As shorebirds are mobile and able to utilize different areas as habitat conditions become suitable, it is unlikely that negative impacts to shorebirds will occur as shallow water/mudflat areas shift locations. In areas along the southern portion of the Sea, barnacle bars and other topographic variations back up drainwater and create small, shallow impoundments where shorebirds forage. To the degree that water from the Sea also contributes to determining the extent and depth of these impoundments (i.e., creates a backwater effect), the extent of inundation and characteristics of these areas could change as the Sea recedes. These potential changes would occur under both the Proposed Project and Baseline. At the north end of the Sea, there could be a net reduction in the amount of shallow water/mudflat habitat. The topography of the seabed is much steeper than at the south end of the Sea. Thus, as the Sea recedes and the total length of shoreline becomes smaller, the amount of mudflat/shallow water habitat would decline. This effect would be greater under the Proposed Project than the Baseline. However, the Whitewater River could create a more extensive delta with greater amounts of shallow water/mudflat habitat as its discharge spreads out as the Sea pulls away from the river mouth. Increased flow from the CVWD Service Area could enhance this effect. Under both the Proposed Project and Baseline, shallow water/mudflat habitat could be lost or reduced as the Sea recedes, but under both alternatives, new areas of shallow water/mudflat habitat also would be created as the Sea recedes. Because the magnitude and likelihood of changes in amount and characteristics of shallow water/mudflat habitat, either positively or negatively, does not differ between the Proposed Project and Baseline, the Proposed Project would not significantly affect the availability of this habitat type. All of these potential impacts to shallow water/mudflat habitat are described under Impact BR The analysis was based on the best available information on the bathymetry of the Sea and the potential changes in Sea elevation under the Proposed Project. Response to Comment R5-76 It is not clear that a shallower Sea will be more productive. Total nutrient loading will be reduced with the conservation program and possible enhanced resuspension of surface sediments could contribute nutrients to stimulate more algae growth. Alternatively, suspended sediments may reduce average light exposure to the algae community and thus reduce productivity (light reduction to algae is a likely result of enhanced mixing of the water column, and is exacerbated by entrained sediment). In addition, the change in productivity of the Sea in relation to decreased average depth is likely to be insignificant as the Sea is now and has always been highly eutrophic. Regardless, as discussed in the text, there is no known quantitative link between Sea productivity and avian disease that would allow us to predict changes in incidence of disease (even if we could predict changes in the Sea's productivity). Response to Comment R5-77 Please refer to the Master Response on Biology Approach to the Salton Sea Habitat Conservation Strategy

5 Page 20 Response to Comment R5-78 Approach 1, which included stocking tilapia in the Salton Sea and constructed ponds, has been eliminated from consideration. See Master Response for Biology Approach to Salton Sea Habitat Conservation Strategy in Section 3 of this Final EIR/EIS. Response to Comment R5-79 Please refer to the Master Response on Biology Approach to the Salton Sea Habitat Conservation Strategy. Response to Comment R5-80 See Master Response on Biology Approach to Salton Sea Habitat Conservation Strategy in Section 3 of this Final EIR/EIS. Native tree habitat likely would not be created in the seabed exposed by the receding Salton Sea because, as the commenter notes, the soils are not likely to be suitable. (If soils and water quality are suitable, the HCP Implementation Team [IT] could locate native tree habitat in areas of exposed seabed). Rather, native tree habitat most likely would be created in natural riparian systems such as along San Felipe Creek or in conjunction with managed marsh habitat created in the Imperial Valley. IID would work with the HCP IT to identify the location for creating native tree habitat and the specific design characteristics with approval required from the USFWS and CDFG for implementation. The HCP includes a monitoring and adaptive management program to ensure that created native tree habitat is developing and functioning as desired, or to identify whether management actions are necessary. If there is a net loss in the amount of tamarisk scrub habitat, IID could create native tree habitat (see Salton Sea - 3 in Chapter 3 of the HCP). IID could elect to create native tree habitat prior to or after a loss of tamarisk scrub habitat. As explained in Salton Sea - 2, if IID creates native tree habitat prior to a loss of tamarisk scrub, there would be no short-term reduction in habitat value. Alternatively, IID could create native tree habitat after documenting a net loss of tamarisk scrub. In this case, IID would create three times the acreage that would be required if IID created the habitat prior to documenting a loss. If IID creates habitat after documenting a decline, there would be a shortterm reduction in the availability of tamarisk scrub habitat. A short-term reduction could have significant impacts if tamarisk scrub habitat is a 5-348

6 Response to Comment R5-80 (continued) limiting factor for a species. Tamarisk scrub is an invasive, non-native plant that provides poor habitat quality for wildlife. Given its abundance in the Project Area (more than 7,000 acres quantified) and poor quality, it is not likely to be a limiting factor for any wildlife species, and a short-term reduction would not be expected to result in population-level effects. Response to Comment R5-81 With the implementation of the Salton Sea Habitat Conservation Strategy as described in the Master Response on Biology Approach to Salton Sea Habitat Conservation Strategy (in Section 3 of this Final EIR/EIS), the elevation of the Salton Sea will not begin to decline until at least the Year 2030, and the ultimate elevation under the Proposed Project would be approximately -240 ft msl, reducing the surface area of the Salton Sea by approximately 16,000 acres (or 25 square miles). This is one-quarter of the reduction that was projected under HCP Approach 1. As the commenter states, primary recreation use of the Sea is associated with the fishery. The Salton Sea Habitat Conservation Strategy mitigates Project impacts to fish. Since it can be assumed that recreation use would decline under the Baseline once fish are no longer able to reproduce, the Project impacts associated with the decline in surface area are still not considered to be significant

7 Page 21 Response to Comment R5-82 With implementation of the Salton Sea Habitat Conservation Strategy, no additional area of the seabed would be exposed beyond that projected for the Baseline until the year After 2035, the additional exposed area of seabed would be reduced by approximately 16,000 acres or 25 square miles. Mitigation measures included in the Draft EIR/EIS recommend relocation of camping and boating facilities to assure continued opportunities for those recreation activities. The greatest additional width of exposed area would be along the southern portion of the Sea, where slopes are gentlest. Response to Comment R5-83 Mitigation Measure R-7 specifies that if the elevation of the Sea declines, boat launching facilities and access to them must be relocated as the Sea declines to provide ongoing boat launching opportunities. The relocation of these facilities may be temporary and ongoing until the Sea reaches its minimum and stable elevation, at which point permanent facilities must be provided. When the Project is approved, IID must adopt a Mitigation and Monitoring Plan which will specify who is responsible for implementation of mitigation measures. The relocation of boat launching facilities is the responsibility of IID. With implementation of the Salton Sea Habitat Conservation Strategy, the elevation of the Salton Sea would remain stable until the year 2030, at which point the Sea would begin to decline below the Baseline elevation until it reaches approximately -240 ft msl. As stated above, IID would be responsible for maintaining ongoing boat launching opportunities as the Sea declines. Mitigation Measure R-7, has been revised to reflect that elevation changes would also occur with the HCP Approach 2 (Salton Sea Habitat Conservation Strategy). See subsection 3.6 under Section 4.2, Revised Text in this Final EIR/EIS. Response to Comment R5-84 Mitigation Measure R-10 specifies that if elevation of the Sea declines, camping facilities and access to them must be relocated as the Sea declines to provide ongoing boat launching opportunities. The relocation of these facilities may be temporary and ongoing until the Sea reaches its minimum and stable elevation, at which point 5-350

8 Response to Comment R5-84 (continued) permanent facilities must be provided. When the Project is approved, IID must adopt a Mitigation and Monitoring Plan which will specify who is responsible for implementation of mitigation measures. The relocation of camping facilities is the responsibility of IID. With implementation of HCP Approach 2 (now referred to as Salton Sea Habitat Conservation Strategy), the elevation of the Salton Sea would remain stable until the year 2030, at which point the Sea would begin to decline below the Baseline elevation until it reaches approximately -240 ft msl. As stated above, IID would be responsible for maintaining ongoing camping opportunities as the Sea declines. Mitigation Measure R-10 has been revised to reflect that elevation changes would also occur with implementation of the Salton Sea Habitat Conservation Strategy. See subsection 3.6 under Section 4.2, Revised Text, in this Final EIR/EIS. Response to Comment R5-85 Please refer to the Master Response on Air Quality Salton Sea Air Quality Monitoring and Mitigation Plan in Section 3 of this Final EIR/EIS. Comment noted. Response to Comment R

9 Page 22 Response to Comment R5-87 Please refer to the Master Response on Air Quality Applicability of General Conformity Requirements to the Proposed Project or Alternatives in Section 3 of this Final EIR/EIS. Response to Comment R5-88 Please refer to the Master Response on Air Quality Wind Conditions at the Salton Sea in Section 3 of this Final EIR/EIS. Response to Comment R5-89 Please refer to the Master Response on Air Quality Wind Conditions at the Salton Sea in Section 3 of this Final EIR/EIS

10 Page 23 Response to Comment R5-90 Please refer to the Master Response on Air Quality Wind Conditions at the Salton Sea in Section 3 of this Final EIR/EIS. Response to Comment R5-91 Please refer to the Master Response on Air Quality Wind Conditions at the Salton Sea in Section 3 of this Final EIR/EIS. Response to Comment R5-92 Commenter notes that Figures through illustrate the locations of monitoring stations in the Project region, rather than Figure as noted in the Draft EIR/EIS. The previous Draft EIR/EIS has been revised to reflect this concern. This change is indicated in this Final EIR/EIS in subsection 3.7 under Section 4.2, Text Revisions. Response to Comment R5-93 Please refer to the Master Response on Air Quality Applicability of General Conformity Requirements to the Proposed Project or Alternatives in Section 3 of this Final EIR/EIS. Response to Comment R5-94 Please refer to the Master Response on Air Quality Applicability of General Conformity Requirements to the Proposed Project or Alternatives in Section 3 of this Final EIR/EIS. Response to Comment R5-95 Please refer to the Master Responses on Air Quality Applicability of General Conformity Requirements to the Proposed Project or Alternatives and Air Quality Consistency with the State Implementation Plan for PM10 in Section 3 of this Final EIR/EIS. Response to Comment R5-96 Please refer to the Master Response on Air Quality Emissions from Construction of Conservation Measures in Section 3 of this Final EIR/EIS