Ventura River Preserve – Rice Creek Re‐Alignment Project Restoration Plan
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Ventura River Preserve – Rice Creek Re‐Alignment Project Restoration Plan I. Project Summary The Rice Creek Re‐Alignment Project will return flow to the historic channel of Rice Creek. Rice Creek was channelized and diverted over a cliff through a culvert in the 1920’s, severing its hydrologic connection to the Ventura River. The diversion also de‐watered over 2,900 feet of the stream’s natural course. Subsequently, the land was developed and re‐contoured for the installation of orchard crops. By re‐directing the flow back into a channel along the historic route, the project will create approximately 1,700 linear feet of stream habitats, and re‐wet an additional 1,200 linear feet of remnant channel. The project is expected to increase habitat for birds, wildlife, and amphibians, while maintaining water quality important for steelhead downstream in the Ventura River. The proposed restoration work is being funded primarily by offsite mitigation funds approved for use on this site by the U.S. Army Corps of Engineers as part of the Ventura River Watershed Habitat Restoration Fund, an approved In‐Lieu Fee program. II. Project Location The proposed project is located in the Ventura River Watershed in Ventura County, CA on the Ventura River Preserve (VRP), a property owned by the Ojai Valley Land Conservancy. (Fig. 1). The watershed encompasses 228 square miles, of which slightly less than half lie in the Los Padres National Forest. The river supplies water to the Ojai Valley and the City of Ventura. The 1600‐acre VRP is located approximately 13 miles upstream of the Ventura River’s estuary. The property is divided into eastern and western sections by the Robles Diversion Water Canal (“Canal”) managed by Casitas Municipal Water District. The western section contains portions of the Santa Ynez Mountains and four small tributary watersheds; Rice, Wills, Olive and Sycamore Creeks. The eastern section of the preserve includes a 64‐acre orange grove as well as the channel, floodplain and alluvial terraces of the Ventura River. Through the VRP, the Ventura River channel and associated floodplains are characterized by sub‐surface summer flows (with a relatively high water table) and intermittent surface flows in the winter including occasional catastrophic floods. The project site for this application is located on Rice Creek (Fig. 2), an intermittent stream with a watershed of approximately 0.6 sq. mi., and is effectively divided into upper and lower portions by the diversion canal. Currently, the upper portion of Rice Creek, or that which lies to the west of the canal, is in a relatively natural, undisturbed condition and functions as a riparian 1 corridor that provides seasonal stream habitat, riparian canopy cover and connectivity from the upper watershed within Los Padres National Forest to the lower watershed. However, after Rice Creek passes through a 60‐inch culvert under the canal, these functions are greatly diminished. The proposed project will both enhance habitat values and re‐create the hydrologic connection between Rice Creek and the Ventura River. Figure 1. Regional Location Map 2 III. Permits Requested We are requesting authorization for this project under nationwide Permit #27, Stream and Wetland Restoration Activities and Nationwide Permit #33 for Water Diversion. While most of the project will be undertaken in areas that are not now considered Waters of the United States, the structural elements and stream bank modifications necessary for the re‐direction of stream flow from the existing diversion channel does constitute work in jurisdictional waters. Nationwide Permit #33 is requested because the project will permanently divert the live flow of Rice Creek from its existing channel into the newly restored historic channel. The project work will be undertaken during the summer when there is no surface flow in Rice Creek, so diversion measures do not include temporary diversion of any live flow. Permits will also be necessary from the Regional Water Quality Control Board (401 Certification), CA Department of Fish and Game (Streambed Alteration Agreement), and Ventura County (Grading Permit). These permits are in process. 3 IV. Project Description Background and Site Description The lower portion of Rice Creek was diverted from its historic or natural course in the 1920’s. It was channelized when the orange grove was planted to allow full usage of the acreage for agricultural purposes. The diversion channel was then planted with Arundo donax to stabilize the channel banks. Today, while most of the arundo has been removed, the only native vegetation along the 700‐foot channelized portion includes a few scattered coast live oaks and arroyo willows. At the end of this channel, flows are carried over a grade stabilization structure that creates a 25‐foot drop to the Ventura River floodplain. Rice Creek’s historic channel was effectively dewatered when the creek was diverted to the man‐made channel. However, a 1,700‐foot long depression along its historic course through the orange grove is visible today and continues to carry surface runoff to a 1,200‐foot section of remnant riparian corridor between the orange grove and Rice Creek’s historic confluence with the Ventura River. Though this remnant section is degraded due to altered hydrology and infestation of Arundo (currently being removed), native riparian vegetation includes large sycamores and willows, as well as coast live oaks. The project site is a 64‐acre orange grove (Fig. 2) that was abandoned when OVLC took ownership of the property in 2003. It is bounded on the west by the Robles Diversion Water Canal and access road, and on the east by a 15 to 40‐foot high terrace that drops to the floodplain of the Ventura River. Irrigation of the grove ceased in 2006 and most of Existing culvert outlet on Rice Cr. the orange trees are stressed and dying. Ground cover consists of invasive non‐native plants such as various thistles, mustard and brome grasses. Currently, Rice Creek and the orange grove provide very little habitat value other than for disturbance‐ adapted species such as ground squirrels. Bird nesting in orange trees is minimal although some bird species do forage in the orange grove area. Within some areas of the orange grove, natural recruitment 4 of native plant species has occurred to some extent (coast live oak, laurel sumac, toyon, mulefat, coyote brush, California sagebrush, black sage, and pearly everlasting). In 1992, a small diesel spill occurred where the historic channel of Rice Creek leaves the orange grove and moves into the remnant strip approximately 1,200 ft upstream of where the creek historically joined the Ventura River. In 2008‐2009, OVLC assessed the remaining contaminants with funds from Department of Toxic Substances Control and oversight from Ventura County’s Voluntary Cleanup Program (VCVCP). Results indicate that the remaining concentrations of Total Petroleum Hydrocarbons as Diesel meet the commercial requirements thus Ventura County Voluntary Cleanup Program (VCVCP) will allow OVLC to leave the contaminants in place with assurance that they will not be remobilized by realigning Rice Creek. The project plan accounts for this by re‐locating the confluence of the restored channel and the remnant channel away from the historic spill area. Earthwork – Excavation and Fill Earthwork for the project will consist of modifications at the upstream and downstream extents of the project site. At the upstream end, the existing channel will be plugged to divert water into the historic channel. It will also be necessary to configure the confluence of the new channel with the remnant historical channel. Two design alternatives were analyzed for diverting the stream from the existing diversion and back into the historic channel (See Alternatives Report). Alternative 2 was chosen because it lengthens the channel and results in a smoother interface between the existing and new channels. It requires some additional grading and fill, but will also preserve some existing oak trees. A pool structure was added in the upstream reach to help manage water velocity and to create more aquatic habitat. The flow of Rice Creek is being directed into a remnant channel still existing on the site. Therefore, the project does not require excavation of the new channel. This approach was chosen because the historic channel is stable and already stabilized with grasses that will prevent erosion of the new channel. 5 Grading plan details are based on information developed in Attachment A, Rice Creek Restoration: Alternatives and Hydraulic Analysis Report, and the attached Hydrology Appendix. The dimensions of the constructed channel sections have been based on hydrologic modeling using the HEC‐RAS model. Based on model runs, the new channel will be approximately 10 feet wide at the channel bed and bank slopes will be shallow at approximately 3:1. The channel shape will provide stable banks for supporting native riparian plants. The channel route will follow the historic route of the stream as indicated by the existing depression that currently exists on the site, and illustrated on the plan view diagram Figure 3. A typical channel cross‐section of the upstream diversion structure is shown in Figure 4. The downstream road crossing will have a similar cross‐ section, but a portion will be left unplanted for vehicular access. Armoring will be necessary on 2 sections of the new channel due to higher water velocities. These areas include the initial diversion of the stream into the new channel, and the new confluence area where the new channel joins the historic remnant channel. At the downstream location, an armored road crossing will be constructed as part of the new confluence zone. This will provide seasonal access to portions of the site Figure 4. Cross‐section of diversion structure and will also serve as the gradient control for the downstream end of the project during high flows.