4.4 Biological Resources
tern nesting island was constructed at Batiquitos lagoon just east of the I-5 freeway which is approximately
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0.75 mile further inland than the river mouth.
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Based on the figures, borrow sites S0-9, MB-1 and SS-1 would be greater than one mile distant while SO-
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7 and SO-6 would be under one mile. Receiver sites at South Oceanside, South Carlsbad North and
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Moonlight Beach would be outside the two mile radius. The two closest receiver sites would be Batiquitos
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and Cardiff which are just south of the lagoon mouths at Batiquitos and San Elijo, respectively.
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To gain an understanding of the potential impact to tern foraging during nesting season the percentage of
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foraging area potentially affected by turbidity within the one and two mile distances was calculated for the
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both the cutterhead and hopper dredge. The calculations and supporting technical notes are contained in
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Appendix F while key conclusions are summarized in Table 4.4-1. The potential turbidity varies with the
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two dredges. With the cutterhead there would be simultaneous dredging and sand placement. With the
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hopper dredge there would be tailings at the dredge and mono buoy locations. The percentage calculation
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considers both average and maximum typical current conditions. It is an extremely conservative analysis
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because it assumes nearshore sand placement not onshore, and no training dikes. Both of these elements
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are part of this project's design and would further reduce turbidity in the near shore. It also does not
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consider the available foraging area inside the lagoons themselves, which the terns are known to utilize.
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Under the very worst-case conditions of maximum current speed at the two receiver sites closest to the
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nesting locations (Batiquitos and Cardiff) the percentage of area affected by the hopper dredge would be
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less than four percent of the available foraging area within one mile. At the remaining sites, the percentage
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of foraging area affected would range from zero to less than 2.5 percent. With the cutterhead dredge the
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percent potentially affected would be a maximum of two percent at the Cardiff site, within one mile.
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Considering the two mile radii the percentage would reduce further.
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Based on the remaining area available for foraging and the fact that this worst-case analysis likely overstates
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the potential impact, impacts associated with construction turbidity during the tern nesting season would
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be less than significant. However, the USFWS and USACOE have requested that SANDAG continue
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to consult with them under Section 7 of the Endangered Species Act to further reduce the potential for
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construction impacts. This process would be completed during the permit negotiation process and would
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consider such items as phasing to construct more sensitive sites such as Batiquitos prior to nesting, or early
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in the nesting season, other construction methods to minimize turbidity, and predator control.
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Regional Beach Sand Project EIR/EA
Page 4.4-25
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