Chapters 1 - U.S. Fish and Wildlife Service

Chapter 3
greater than three miles per hour from the south or southwest. No aerial spraying over
the Refuge would be permitted. OCVCD shall also coordinate with the Refuge Manager
and NWSSB prior to applying any adulticides, as well as during the monitoring and
evaluation of the effectiveness of the treatment in eliminating the threat to human health.
Under Alternative B, the following mosquito control products would be considered for use
under appropriate condition: the larvicides Bacillus thuringiensis var. israelensis (Bti),
Bacillus sphaericus (Bs), Altosid, and Natular; the pupacide, monomolecular biodegradable
film (e.g., Agnique MMF); and adulticides with the active ingredient sumithrin (e.g., Anvil
10+10 ULV, AquaAnvil).
Other Management Activities. Other management actions proposed under this alternative to
benefit listed species, as well as the other trust species supported by the Refuge include:
1. Replacement of the Western Culverts in the Bolsa Cell
Two 30-inch culverts were installed within the western levee of the Bolsa Cell as part
of the Port of Long Beach restoration project (refer to Section 4.2.5.1 for more
information). These culverts, which facilitate the flow of bay water into the western
end of the cell, have over the years been plugged to reduce the volume of water
entering the cell and then subsequently reopened in an attempt to better regulate
water levels, all with limited degrees of success. The existing culverts are in poor
condition, with significant signs of deterioration. Tidal flow through the culverts has
been severely compromised by mussel fouling, while pipe erosion is allowing water to
flow around the culvert, threatening the stability of the levee. Under this alternative,
the culverts would be removed, the levee repaired, and a new water control structure
installed near the center of the levee.
The preliminary design for the water control structure indicates that the structure
would likely consist of pre-cast concrete headwalls and tail walls, a stainless steel
slide/screw gate, and two 30-inch diameter, 40-foot-long High Density Polyethylene
(HDPE) pipe, which is highly resistant to biological buildup (e.g., mussel fouling) and is
not susceptible to corrosion. The incorporation of a slide/screw gate into the design
would allow for the precise management of tidal flows into and out of the Bolsa Cell.
Although the specific design of the structure could change during final design, the
general way in which the structure would be operated would remain the same.
Installation of the new structure would require the use of coffer dams, or the
implementation of other appropriate actions, during construction to prevent tidal
exchange through the construction site. The tide gate structure would be placed on
base rock and then back filled with appropriate clean material. Once the areas around
the concrete headwalls and tailwalls are back filled and properly compacted, rip-rap
would be placed around the structure to prevent any erosion of the back fill material.
Following installation and testing of the new water control structure, the old culverts
would be removed and this portion of the levee would be filled and stabilized with the
rip-rap. Installation of the new structure, culvert removal, and levee stabilization
would be implemented using a conventional land excavator. Debris and any excess fill
from the project would be trucked away for disposal at an appropriate off-site location.
All work would be conducted between September 1 and February 1 to avoid impacts to
nesting birds and best management practices would be implemented to protect water
quality and native habitat.
3-28 Seal Beach National Wildlife Refuge