Alternative Futures for the Region of Camp Pendleton, California
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Interstate-15 Wildlife Crossing
The Santa Ana Mountains and the Palomar Mountain area are regarded as high quality habitat and are crucial to the maintenance of the region's high biodiversity. Much of the area is managed by the Cleveland National Forest, The Nature Conservancy, and Camp Pendleton. However, Interstate-15 has fragmented this habitat, making it difficult for the several species that require large home ranges, especially the California cougar, to use the full extent of the area. Currently, several cougar from small populations die each year on the Interstate. Male cougar must cross Interstate-15 to sustain genetic diversity within the Santa Ana population; without this, inbreeding will lead to regional extinction in a few generations (Beier, 1993). Crossing can be enabled by an overpass or underpass that will allow wildlife movement.
The following criteria should govern any design, and are based on the more stringent needs of the cougar:
- Cougar travel at night, in places without lighting and favor routes in the scour zones of stream channels, along ridgelines, and on dirt roads and trails through dense chaparral. They use woody cover near road crossings for protection and avoid row crops and orchards.
- Cougar avoid undercrossings less than 3m wide and noise levels greater than 60 decibels (Beier, 1993).
Two solutions are proposed and are shown in figure 117. The first is a partially enclosed underpass at the I-15 crossing of Temecula creek. The second is an overpass near this point.
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