Valencia Water Reclamation Plant Scour Emergency Repair/Riprap Installation

The middle section of the retaining wall that separates the Valencia Water Reclamation Plant (VWRP) from the Santa Clara River (SCR) consists of a mechanically stabilized earth (MSE) wall and large rock riprap. The large rock riprap was installed under the California Regional Water Quality Control Board, Los Angeles Region, File No. 05-140, to repair the damaged retaining wall resulting from the January 2005 flood. Since the riprap installation, scour and erosion have advanced the riverbank northward, exposing the MSE wall beyond the riprap for approximately 50 feet in length and 14 feet in height. With the expected El Niño conditions during the 2026-2027 wet weather season, heavy flows in the SCR could extend erosion and scour farther north, undermining and destabilizing the MSE wall, interrupting wastewater treatment service for over 200,000 residents, and ultimately sending untreated wastewater down the SCR. The emergency project was originally part of the VWRP Middle Section Retaining Wall Ground Improvement Project under the California Regional Water Quality Control Board, Los Angeles Region, Clean Water Act Section 401 Certification File No. 26-113, with an expected construction start date of April 2027. However, due to the expected El Niño conditions during the 2026-2027 wet-weather season, the Santa Clarita Valley Sanitation District advanced the riprap installation as an emergency project.