2.0 Alternatives Considered
definitive. Actual project impacts can only be determined based on post-project monitoring. However,
sensitivity analyses were performed to understand how results could vary based on input parameters and
a comparison of results with empirical data was performed to help understand the model predictions in this
context. The predictions were found to be relatively consistent with empirical data, and likely conservative
(Moffatt & Nichol 2000b). Also, when interpreting the results of the model, this analysis has consistently
utilized the worst-case, most conservative output.
Based on the results of initial modeling, four receiver sites were modified in length and location to avoid
direct impact to resources, typically reefs (Section 2.3). Modeling was performed again with a maximum
3 million cy alternative and the refined receiver sites. Potential worst-case impacts to sensitive marine
resources were quantified. In an attempt to further reduce impacts, two scenarios were generated with less
sand overall (2 million cubic yards). In October 1999, the SEC authorized their consideration. Under one
scenario, the total volume of sand at each receiver site was reduced by one-third (Scenario 1). Under the
other scenario (Scenario 2), reallocation of sand away from more sensitive beaches was reevaluated to
further reduce impacts. As a result, Moonlight Beach and Cardiff receiver sites were eliminated and that
sand placed at alternate northern beaches. The intent was to reduce potential impacts to marine resources
by decreasing the amount of sand introduced to the system and by avoiding direct sand placement at
offshore sensitive receiver sites. Based on additional sand transport modeling and evaluation of sand
deposition patterns, potential worst-case impacts to biological resources were again estimated.
Both of the 2 million cy scenarios, as well as the 3 million cy alternative, were presented to the SEC on
December 9, 1999. Based on direction from the SEC, both scenarios were modified slightly to increase
sand volume at the North Carlsbad receiver site from 160,000 cy to 240,00 cy. Preliminary evaluation
indicated that potential impacts to marine resources would be very similar in scale under either 2 million cy
scenario. At the December 1999 SEC meeting, Scenario 1 was selected as preferred, and the SEC
directed the evaluation of that scenario in this EIR/EA.
Subsequent to the December 1999 meeting, a preliminary evaluation of mitigation and monitoring
requirements was prepared using the previous Navy project's permit requirements as a guide. That
evaluation identified monitoring requirements during constructionas well as post-construction, and provided
preliminary cost estimates. Based on the high cost to mitigate impacts to reefs, another alternative was
generated. The modeling of various alternatives consistently predicted areas of persistent sand deposition
off North Carlsbad and Moonlight Beach. The depositional areas were located where mapping was not
available. Based on worst-case, conservative assumptions, the potential indirect impacts to reefs would
Regional Beach Sand Project EIR/EA
Page 2-5
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