The San Diego County Water Authority (SDCWA) held a public hearing on the draft environmental Mitigated Negative Declaration (MND) for the Moosa Canyon erosion control project, and the Feb. 23 hearing during the meeting of the SDCWA’s Water Planning Committee did not produce any opposition to the draft MND.
“It’s always good when there is little or no public comment, (because) that generally means that bases got covered, and we worked hard to do that,” said Water Planning Committee chair David Cherashore, who is one of the City of San Diego’s representatives on the CWA board.
The CWA’s Second Aqueduct includes Pipelines 3, 4, and 5. The pipelines transport water through steep terrain and cross under Camino Del Rey in Bonsall. Moosa Creek is a riparian environment with dense vegetation, and in 2013 CWA staff observed that a portion of Pipeline 4 was exposed in Moosa Creek due to creek bed erosion. The location coincides with a horizontal bend in the pipeline where the pipeline crown is visible.
The site is within Rainbow Municipal Water District boundaries.
“This is all an impact of the Highway 15 construction back in the ’80s,” said Rainbow general manager Tom Kennedy, who is also Rainbow’s representative on the CWA board. “It’s going to be an ongoing issue.”
The exposed bend in Pipeline 4 is subject to internal water force, or thrust, as the water changes direction, although a structural analysis of the internal water forces indicate that those forces are not currently a concern. The CWA is concerned that future storms could cause additional erosion and threaten the suitability of the pipelines at the creek crossing.
“The purpose of this structure is to dissipate the energy of the water prior to the water leaving the project site,” said CWA senior water resources specialist Don Chadwick.
During 2016 CWA staff installed interim erosion control measures to restore cover over the pipeline and stabilize the area prior to the next wet season. In June 2016 the CWA board authorized a $279,630 professional services contract with Michael Baker International, Inc., for the design of pipeline protection. That 30-month contract includes design services, bidding services, and construction phase design support services.
The MND cites less than significant impacts for all environmental categories other than riparian habitat, and a combination of on-site restoration and off-site acquisition will reduce that impact to less than significant.
The final environmental statement is expected to be certified during the CWA’s April 27 meeting. Prior to construction, the project would still require temporary right-of-way agreements, a U.S. Army Corps of Engineers letter allowing the project, and a streambed alteration agreement with the California Department of Fish and Wildlife. Once the requirements to proceed are met, the CWA will advertise the project for bid. The actual construction is expected to begin in fall 2017 and take approximately 40 workdays.