4.4 Biological Resources
Additionally, no measurable sedimentation is predicted for historic kelp bed locations to the north or south
of the receiver site.
PotentialIndirect Impacts at Imperial Beach. Sand is the predominant habitat offshore ImperialBeach
(Figure 4.4-12). Kelp have historically occurred offshore with low to moderate persistence at depths of
-20 to -35 MLLW which is at a minimum of 1,900 feet from the shoreline of Imperial Beach.
A maximum persistent depths of cover less than four inches is predicted for distances ranging from
approximately 1,900 to 2,300 feet offshore for one year (Figure 4.4-12). After the first year, maximum
persistent predicted sand is one inch. These estimates of sedimentation are within the historical average
differences in sand depth between winter and summer profiles at these distances offshore and there would
be no significant impact.
Summary of Conclusion, Indirect SedimentationImpacts. In conclusion, based on worst-case model
predictions, partial sedimentation could occur to hard substrate with indicator species near four receiver
sites: North Carlsbad, Batiquitos, Moonlight Beach, and Solana Beach. A total of 3.2 acres with giant kelp
could experience partial sedimentation off of North Carlsbad (0.73 acres), near Batiquitos (1.46 acres),
and near Solana Beach (1.05 acres). The impact is considered to be less than significant because the kelp
is generally sparse and located in a non-persistent kelp area. A 0.27 acre reef off Moonlight Beach is
predicted by the model to experience partial sedimentation and it contains a subclimaxcommunityofsparse
feather boa. Impacts would be less than significant in the long-term because sedimentation would not
overtop the reef and feather boa is characterized by rapid re-colonization. Finally, three small reefs totaling
0.24 acre, with some surfgrass, off of North Carlsbad may experience partial sedimentation under worst-
case conditions. This impact would also be less than significant because it is predicted to affect only one
growing season and the leaves would be well above the sand deposition levels, allowing for long-term
recovery.
Borrow Sites
Potential impacts to marine resources would be related to the dredge itself (direct and indirect) and
placement of the dredge equipment (pipelines, etc.). The following section addresses these impacts in that
order.
Regional Beach Sand Project EIR/EA
Page 4.4-37
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