Final Mitigated Negative Declaration and Response to Comments

More detail on the range of lake bottom elevations, and locations of the marker buoys and
watercraft navigation land at the entrance of Emerald Bay, to identify whether the bottom
barriers would be located within the watercraft navigation lane.
Response: These comments are related to whether or not boat traffic into and out of
Emerald Bay will be restricted. The map on Appendix A shows the contours of water
depth which detail the deepest part of the channel where the watercraft navigation lane
is. The Asian clam project activities would occur throughout the entire navigation lane
as this is where the Asian clam infestation is centered. As stated above, traffic into and
out of Emerald Bay will need to be controlled to implement the project safely (also
discussed in Transportation and Public Services), which means that no boats will be
allowed in or out for short periods of each day during installation and removal unless
water levels are high enough to allow non-motorized boats to pass and escorted
motorized boats to pass, while still protecting diver safety. These closure periods would
be scheduled during the mornings and on weekdays to avoid visitor use periods to the
extent possible and we will add a bullet to Mitigation Measure Rec-1 to state that “To
the extent possible, all installation and removal activities will be scheduled outside of the
high recreation period between Memorial Day and Labor Day.”
More detail on characterization of the lake bottom substrate and fish habitat and/or Tahoe
Regional Planning Agency designated fish habitat.
Response: This restoration project is located in prime feeding and cover habitat on the
Tahoe Regional Planning Agency Fish Habitat Map. As stated in the Biological
Resources discussion “The proposed project would not impede fish or wildlife
movement and would not impact wildlife corridors. Work would occur in a fish bearing
lake, but the high boat traffic and wave action in the treatment area, short term duration
of barrier deployment and removal activities, and positive impact of removing an
invasive competitor would result in less than significant impacts to fish.” There is also
discussion of fish spawning areas and Lahontan cutthroat trout in the Environmental
Setting section of Biological Resources. Completion of project activities would
constitute a restoration of this prime feeding and cover habitat.
More detail on the total depth within the lake bottom substrate that will be affected/ treated by
bottom barriers.
Response: This information is not currently known. The benthic barriers have been
shown to kill Asian clams down to greater than 8 cm depth, and it is anticipated that
impacts would be similar in this case. We do not feel that this information would change
any determinations in this environmental analysis.
More detail on alternative treatment methods.
Response: Freezing clams in place has been suggested as a potential method
because the technology is used in non-restoration actions to freeze sediment under the
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Asian Clam Control Project
Final Mitigated Negative Declaration and Response to Comments