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impacts of burial at these depths is considered adverse but insignificant.  Benthic
communities on low rocks within the active littoral zone are adapted to seasonal sand
movement. Recovery of the community on the rocks would be expected to take 1 to
2 years. From 800 ft. seaward, the depth of sand cover is estimated to be less than
6 inches with an average sand cover of approximately 1.5 inches. Sediment deposition
at the scale of a few inches would have little impact on hard bottom communities in the
area. Impacts would be insignificant.
Carpinteria Reef is located west of the Ash Avenue beach placement site. Beach fill is
proposed during the fall and winter only, when the littoral drift is predominately to the
east. Therefore, sand burial of the reef should not occur. To insure that beach
nourishment at Ash Avenue does not impact this sensitive reef habit, the reef will
be monitored for potential sand burial.  Significant impacts to Carpinteria Reef are
not expected.
Significant rocky intertidal habitat with extensive surfgrass beds occurs about 1,500 ft.
downcoast of the Ash Avenue site. Some sediment placed at Ash Avenue may be
carried downcoast to this rocky intertidal area. Based on studies done by Moffatt &
Nichol Engineers for a similar beachfill project, the beachfill will gradually taper off and
will be negligible 2,000 ft. up or downcoast. At the location of the rocky intertidal area,
approximately 1,500 ft. from the Ash Avenue beach placement site, the depth of cover
would be about 25 percent of that at the fill site or approximately 3 to 6 inches. Patches
of sand are characteristic of the habitat in this area and deposition of minor amounts of
sediment from the BEACON project is not expected to cause a significant adverse
impact. However, the intertidal habitat will be monitored to insure that the habitat is not
being degraded by BEACON's beach enhancement program.
Depending on the method and rate of placement as well as the percentage of fine
sediment, the proposed project would create temporary turbidity plumes in nearshore
coastal waters.  Because sediment transport and currents are primarily downcoast
during the winter when sand replenishment would occur at Ash Avenue, turbidity
plumes from beach placement would not be expected to affect Carpinteria Reef.
Scattered rocky habitat offshore of the proposed sand placement site would be
expected at times to be subjected to turbidity from BEACON's beach enhancement
project. Rocky habitat in the intertidal and shallow subtidal areas off Carpinteria Creek
about 1,500 ft. downcoast from Ash Avenue would also be affected by turbidity plumes
from beach nourishment at Ash Avenue. Brief pulses of turbidty that lasted a day or two
would not be expected to have a significant adverse impact on these resources.
However, extended turbidity could have a significant adverse impact. BEACON
proposes to monitor turbidity during beach fills. If the monitoring indicates turbidity is
occurring in rocky intertidal and subtidal areas for extended periods, the rate of
placement of sand will be modified so that large, long lasting turbidity plumes are no
longer created.  The criterion will be that turbidity plumes that extend to the hard
substrate area 600 ft. offshore or downcoast 1,500 ft. to the rocky areas off Carpinteria
Creek should not persist for a period of more than 6 days. Because of this monitoring
and management program, turbidity created by beach fill will not have a significant
effect on biological resources.
36
3208 Bio Report
06/12/02



 


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