The Coachella Valley Water District (CVWD) will construct and install concrete slope protection on the northern bank of the Whitewater River Stormwater Channel (WWRSC) upstream of Cook Street in the city of Palm Desert within Riverside County. Specifically, the project site is limited to the northern bank of the WWRSC, adjacent west of Cook Street and south of the Golf Center at Palm Desert. Elevation at the site is approximately 123 feet to 136 above mean sea level (amsl) in the channel bottom and 155 feet amsl along the top of the channel bank. The WWRSC conveys the Whitewater River through the communities of Palm Springs, Cathedral City, Rancho Mirage, Palm Desert, and portions of La Quinta, terminating at the western most segment of the Coachella Valley Stormwater Channel.
The slope protection project would extend approximately 2,400-feet upstream of Cook Street and consist of both lateral erosion protection for the exposed bank, and also scour protection during large stormwater events. The project will also protect the two (2) 24-inch and 30-inch sanitary sewer lines located in the northern bank of the WWRSC that run parallel to the channel. The concrete slope lining will vary in width, but average less than 100 feet in height and extend from near the top of the channel wall to the toe of the slope where a footing will be installed to provide scour protection of the channel. Temporary staging and work areas at the top of the slope will be needed to access portions of the slope, and these areas will be restored to prior elevational and topographic conditions. Construction equipment will consist of excavators, dozers, backhoe, graders, concrete trucks, dump trucks, water trucks and utility trucks. The acreage of disturbance during construction activities is approximately 5 acres. No import or export of soil is anticipated for the project. Standard best management practices for stormwater and dust control will be implemented. Construction is expected to take approximately 400 work days to complete.
The project site is not located within or adjacent to a conservation area associated with the Coachella Valley Multiple Species Habitat Conservation Plan. The project is not subject to the Coachella Valley Association of Governments Local Development Mitigation Fee because the project location is an existing, disturbed parcel which functions as a stormwater conveyance system.
A cultural resources survey along the project area found that no cultural resources occur in the project area, and therefore none will be affected by the project (ECORP Consulting, Inc. 2020). CVWD will require that any unanticipated discoveries found during project construction be managed through a state-designated procedure designed to assess and treat the find as quickly as possible and in accordance with applicable State and federal law.
A biological resources study was conducted along the project area, which determined that one special-status plant species (chapparal verbena) and one special-status wildlife species (burrowing owl) have moderate potential to occur on the project site. However, the loss of approximately 2.1 acres of low-quality habitat is not considered significant due to the relatively small amount and poor quality of the habitat (ECORP Consulting, Inc. 2020). A pre-construction biological survey will be required to verify there are no nesting birds or burrowing owls along the project site before construction activities begin.
A jurisdictional wetland delineation was conducted within the project area (ECORP Consulting, Inc. 2021). The U.S. Army Corps of Engineer’s Approved Jurisdictional Determination concluded that waters of the United States do not occur on the project site; and therefore, a permit is not required (March 2021). The project will be required to obtain a permit with the California Department of Fish and Wildlife prior to construction.