Chapters 1 - U.S. Fish and Wildlife Service

Chapter 5
Refuge. Removal of concrete and debris from existing marsh areas and removal of the drop tower
would augment these beneficial visual impacts.
Public Use
Alternative C would expand opportunities for environmental education, interpretation, wildlife
observation, and wildlife photography by increasing the number of guided tours and constructing
an elevated wildlife observation deck. These proposals would have no effect on the topographic
character of the Refuge. Because the elevated observation deck proposed for construction under
this alternative would be constructed in the general vicinity of other existing structures including
the Refuge headquarters and various Navy buildings, it would not fundamentally alter the current
visual character of the area. Therefore, the public use proposals included under this alternative
would not adversely affect the character or visual quality of the area.
5.2.3.2 Effects to Geology/Soils
Wildlife and Habitat Management
Each of the management activities conducted under Alternative A would also occur under
Alternative C. None of these activities would trigger or accelerate substantial slope instability,
subsidence, ground failure, or erosion, thus affecting onsite facilities or adjacent facilities, such as
roadway embankments and bridge abutments and pilings. Alternative C proposes to expand
existing management activities to include habitat restoration, culvert replacement, concrete debris
removal, improvements to cordgrass habitat, and removal of the drop tower. Restoration
activities could temporarily expose soil to wind and water erosion if BMPs are not implemented
during construction. To avoid such impacts, all restoration construction specifications would
include the requirement to implement appropriate BMPs for erosion and sediment control during
construction to minimize the potential for water and wind erosion at the project site. In addition,
all slopes associated with future restoration would have a slope gradient of 4:1 or flatter to avoid
the potential for erosion in the future. The restoration of portions of the Refuge’s upland areas
would have no effect on the site’s current susceptibility to geological hazards, such as liquefaction,
settlement, ground rupture, or lateral spreading.
To avoid erosion and soil loss during the installation of a new water control structure in the levee to
the west of the Bolsa channel, BMPs such as the use of silt fencing, cofferdams, straw wattles, and
filter fabric to protect exposed soil would be implemented during project construction. The slopes
adjacent to the structure would be protected from erosion through the use of rip rap or native
vegetation as deemed appropriate during final design.
The implementation of appropriate BMPs during habitat restoration would reduce the potential for
impacts to soil erosion to below a level of significance. Additionally, the restoration proposals
included in Alternative C would not trigger or accelerate substantial slope instability, subsidence,
ground failure, or erosion that could adversely affect onsite facilities or adjacent facilities, such as
roadway embankments and bridge abutments and pilings.
Public Use
Alternative C would expand opportunities for environmental education, interpretation and wildlife
observation and wildlife photography by increasing the number of guided tours and constructing
an elevated wildlife observation deck. These proposals would have no effects on the Refuge’s
geology or soils and the proposed observation deck would not be susceptible to geological hazards,
such as liquefaction, settlement, ground rupture, or lateral spreading.
5-26 Seal Beach National Wildlife Refuge