4.4 Biological Resources
sensitive species and their relative distribution along the coast; and in conservative interpretation of model
predictions. A very detailed evaluation of potential impact associated with sediment transport is provided
in Appendix D, and this summary is provided to briefly describe the methodology and results. Overall,
the evaluation concludes that no significant indirect impacts to sensitive marine resources are anticipated,
although SANDAG would prepare and implement a monitoring plan to verify significant impacts do not
occur. As described in Section 2.5, this monitoring plan would be similar to the Coastal Monitoring Plan
approved by the USACOE in 1997 for the Navy Homeporting project.
The approach to analysis of indirect sedimentation impacts involved the following steps:
(1)
Review of life history information for indicator species to understand sensitivity and recovery rates
after disturbance and therefore generate species-specific significance criteria.
(2)
Review of historical profile data to establish the range in sand fluctuation that naturally occurs along
beach profiles correlated to individual receiver sites.
(3)
Review of historic beach replenishment volumes in the vicinity of the receiver sites to establish the
degree of disturbance to habitats previously experienced from sedimentation.
(4)
Review of project-specific model predictions to identify potential depositional areas, and review of
reef height and occurrence of sensitive resources within predicted depositional areas.
Life History Information. Surfgrass is considered a stress-tolerant species that withstands
sedimentation by having an extensive root system, fibrous leaf sheaths that provide protection from
abrasion, and long leaves (three to five feet) that extend above the sand. While the amount of sand that
would certainly cause mortality is not known, the recovery of surfgrass is tied to the degree of disturbance
to the root system. Surfgrass can recover quickly via regrowth if the root system remains intact. Given that
sand burial does not remove the root system, it is assumed that sedimentation would not be expected to
result in an irreversible impact as long as burial did not persist for several years at the location. An impact
would be significant if sedimentation substantially buried surfgrass (root system and the entire length of
leaves) for more than two consecutive seasons. For this project there were no cases where a reef with
R
surfgrass would be completely buried for two seasons. So further evaluation of the relative sand depth to
R
leaf length was also considered.
R
Feather boa kelp commonly occurs from intertidal to subtidal depths and has a naturally high recruitment
rate on exposed hard substrates and rapid growth. Impacts to feather boa kelp would be expected to last
only as long as a reef was covered by sand. Irreversible impacts to feather boa kelp would not be
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