Final Mitigated Negative Declaration and Response to Comments

project in Marla Bay showed that large scale benthic barrier removal yielded turbidity levels
not to exceed 0.9 NTU (nephelometric turbidity units) and the turbidity measurements
returned to background levels in a matter of minutes. Suction removal also has the
potential to increase local turbidity. Implementation of Mitigation Measure Hydro-1 and
Mitigation Measure Hazmat-1 will reduce these potential impacts to less than significant.
b) The project would not deplete groundwater supplies or interfere with groundwater recharge.
No impact.
c) No existing drainages or drainage patterns would be substantially altered by the proposed
project. No impact.
d) No project activities would result in a substantial increase in the rate or amount of surface
runoff or result in off-site flooding. No impact.
e) The proposed project would not create or contribute runoff water. No impact.
f) The proposed project may cause a temporary increase in turbidity during removal of
benthic barriers or suction removal activities. The barriers can have fine sediment
deposited on them during the period of deployment, and this fine sediment can cause
turbidity as the barriers are removed. Previous bottom barrier water quality monitoring
results indicate that turbidity is localized and temporary in nature. A pilot project in Marla
Bay showed that large scale benthic barrier removal yielded turbidity levels not to exceed
0.9 NTU (nephelometric turbidity units) and the turbidity measurements returned to
background levels in a matter of minutes. Suction removal can also result in short term
localized increases in turbidity similar to that observed during barrier removal.
Supplementation of the barrier treatment method with straw or other material to help reduce
oxygen under the mats would be small in scale and not negatively impact water quality.
Implementation of Mitigation Measure Hydro-1 will reduce these potential impacts to less
than significant.
g) The proposed project does not include a housing component. No impact.
h) The proposed project does not include construction of any structures. No impact.
i) The proposed project would not expose people or structures to a significant risk of loss,
injury, or death from flooding, including flooding resulting from the failure of a levee or dam.
No impact.
j) Lake Tahoe is a large water body with the potential for the production of seiche waves.
However, project activities would not increase the risk of seiche waves or increase public
exposure to this risk. The Lake Tahoe Basin is classified as having low incidence and
susceptibility of small or large landslides (USGS 2007) and project activities will not expose
the public or property to an increased risk or susceptibility from these events. No impact.
Asian Clam Control Project IS/MND
Emerald Bay State Park
California Department of Parks and Recreation
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