Santa Clara River Trail Final Master Plan - Development Services ...

Santa Clara River Trail Plan
Townsend’s big-eared bat (Corynorhinus townsendii), and coast horned lizard (Phrynosoma coronatum) are
also known to occur in the vicinity. Additional species of concern that could occur due to the presence of
potentially suitable habitat and range include the southwestern willow flycatcher (Empidonax traillii
extimus), arroyo toad (Bufo californicus), and California red-legged frog (Rana aurora draytonii). However,
these species have not been recorded in the project vicinity. The density of plant growth in combination
with the linear quality of the river make the riverbed an important wildlife corridor for larger species as
well, including coyotes and deer.
Approximately 2 miles downstream (west) of the project site, the river supports a large area of riparian
habitat upstream of the river’s estuary. This estuary has been noted to be a major stopover for migratory
and/or breeding species of shorebirds and waterfowl, including the endangered California least tern
(Sterna antillarum browni) (City of Oxnard 2004). The estuary is also known to support the tidewater goby
(Eucyclogobius newberryi) and western snowy plover (Charadrius alexandrinus nivosus). The Ventura marsh
milk-vetch (Astragalus pycnostachyus var. lanosissimus), an endangered species, has also been identified in
this area.
Although quality riparian habitat exists along significant portions of the riverbed, disturbance along the
edges of the floodplain and upland areas can be substantial. Trails are found throughout the riverbed,
which are apparently used by off-road vehicles as well as foot traffic. These trails appear to be mostly
limited to the edges of the floodplain, as there is little evidence of such use within the riverbed adjacent
to the project site. Further, exotic (i.e., invasive) vegetation has degraded native habitats in some areas,
particularly giant reed (Arundo donax) and salt cedar (Tamarix spp.), although no exotic species dominate
habitats in the immediate project vicinity (Caltrans 2001).
GEOLOGY AND SOILS
The proposed project is located near the center of the Oxnard Plain, a broad alluvial basin that is filled
with sediments, sands, and gravels deposited by the Santa Clara River. These sand and gravel deposits
are generally characterized as being rich in minerals but unsuitable for agriculture. These alluvial soils are
prone to compaction and liquefaction, and the potential for liquefaction is increased by the high
groundwater level found in the region. Compaction of alluvial soils caused by seismic events has the
potential to affect the project area, with a potential settlement of 1-2 feet projected for the region (City of
Oxnard 2004).
The project vicinity is located within a seismically active region subject to the effects of moderate to large
earthquake events along major faults (City of Oxnard 2004). No active faults have been mapped across
the study area. Several active and potentially active regional faults that may affect the area include the
San Andreas Fault, the Simi-Santa Rosa fault system, the Oakridge fault system, the Santa Monica-
Anacapa and Malibu fault zones and the Ventura-Pitas Point faults, all within 60 miles from the
proposed project area. A complete description of area geologic resources can be found in the City of
Oxnard 2030 General Plan, Open Space/ Conservation Element.
HAZARDS AND HAZARDOUS MATERIALS
There is potential for hazards and hazardous materials to exist within the project area. Natural hazards
are described in Geology and Soils above and Hydrology and Water Quality below. Previous uses of hazardous
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