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

Chapter 1: Existing Conditions
materials in the general project vicinity are known to have resulted in soil and groundwater
contamination. Although pesticides and herbicides used for agricultural operations can pose a hazard to
humans and native biological communities, the County of Ventura Agriculture Commissioner's Office
records show the only remaining residue is DDT and breakdown products. A search of Ventura County
files and the GeoTracker database identified four Underground Storage Tank (LUST) cleanup sites and
‘other’ cleanup sites near the project area (SWRCB 2009). None exist within the project area.
The River Ridge Golf Course was constructed on top of the former Santa Clara landfill. The landfill was
lined and accepted only Class III (non-hazardous) waste during its operation, and was closed according
to closure requirements of the Ventura County Environmental Health Division and California Regional
Water Quality Control Board (City of Oxnard 2008). Hazardous materials are routinely transported on
Highway 101 and the railroad, presenting the possibility of an accident in the vicinity of the project area.
Of the trucks that enter Ventura County on Highway 101, the California Highway Patrol estimates that
52 percent carry hazardous materials and an additional 22 percent carry hazardous wastes (City of
Oxnard 2004). Although the probability of a railroad hazardous materials incident is lower, the severity
is potentially greater because of the greater potential quantities involved as well as the potential for
chemicals and explosive substances to be mixed together.
HYDROLOGY AND WATER QUALITY
The Santa Clara River is the predominant surface
water hydrologic feature in the region, with a
watershed drainage area of 1,634 square miles and
generally produces an intermittent flow regime, which
reflects the area’s predominant wet winter/ dry
summer pattern. Flows can increase rapidly in
response to high intensity winter rainfall events. This
can result in flooding along the river, which has
required municipalities such as the VCWPD and the
City of Oxnard to construct a system of levees. This
flow regime also significantly shapes the vegetative
communities of the Santa Clara River.
The Santa Clara River channel is a wide,
sandy wash through much of the year;
however wet season flows can flood the
channel.
The water flow in the project area reaches its high flo w
period during the local wet season which occurs December through April. Natural flow in the river is
affected by groundwater withdrawals, diversions, municipal uses, and groundwater recharge. Flow is
also regulated by operational conditions at upstream reservoirs, including Lake Piru, Pyramid Lake, and
Castaic Reservoir.
The Federal Emergency Management Agency (FEMA) identifies much of the City of Oxnard to the south
of the project site, as well as the agriculture and recreation areas to the north as being subject to a 1%
annual chance flood event (formerly referred to as 100-year flood event) associated with the river.
Flooding associated with the river has historically posed a significant hazard to communities along its
banks, including the City of Oxnard and the project vicinity. However, as noted above, with the
exception of the project site’s middle segment from N. Ventura Road to the Highway 101 Bridge, the
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