The San Diego County Water Authority held a public hearing April 24 on the SDCWA’s plans to reline the San Luis Rey River portion of the CWA’s Second Aqueduct pipelines, and the hearing drew no opposition.
The CWA board is expected to approve the environmental Mitigated Negative Declaration at the CWA’s May 22 board meeting and approve a contract for the relining at the July 24 board meeting. The CWA’s April 24 meeting also included a presentation on the planned work.
“This relining is intended to extend the service life of the pipelines by about 75 years,” said CWA senior water resources specialist Mark Tegio.
The Second Aqueduct includes Pipelines 3, 4, and 5. Pipelines 3 and 5 currently convey untreated water along the San Diego Aqueduct. Pipeline 4 currently transports treated water. (The master plan update adopted by the CWA on March 27 includes switching Pipeline 3 to treated water and Pipeline 4 to untreated water, which would increase the CWA’s untreated water conveyance capacity, during the 2020-25 timeframe.) Pipeline 3 is a welded steel pipe 72 inches in diameter; Pipeline 4 is a prestressed concrete cylinder pipe with a 90-inch diameter; and Pipeline 5 is a prestressed concrete cylinder pipe 96 inches in diameter.
Several pipeline failures in the early 1990s resulted in the CWA’s 1992 creation of the Aqueduct Protection Program for pipeline constructed prior to 1984. The program included an initial assessment which determined the estimated remaining service life of pipeline portions and the frequency of internal inspections which are used to adjust the replacement and relining schedules.
Pipeline 4 was scheduled to be rehabilitated during fiscal year 2017. However, the widening of State Route 76 between South Mission Road and Interstate 15 includes an alignment which will cross over the CWA’s Second Aqueduct approximately half a mile west of Interstate 15.
The planned bridge over the Second Aqueduct will provide approximately eight feet of vertical clearance between the bottom of the bridge and the ground. Since the new bridge crossing will hinder the CWA’s future ability to maintain, repair, or replace the pipelines under the bridge, an agreement to reline the pipelines impacted by the new bridge crossing was negotiated by the CWA, the California Department of Transportation, and the San Diego Association of Governments (which has been delegated funding discretion for state highways). The expected service life of the new Caltrans bridge is 75 years, so the pipeline relining will likely eliminate the need for future work during those 75 years.
The relining work will cover 3,372 lineal feet of Pipeline 4, 316 lineal feet of Pipeline 3, and 288 lineal feet of Pipeline 5. The relining of Pipelines 3 and 5 will be within the new Caltrans easement limits while the Pipeline 4 relining will start north of the existing State Route 76 and end south of the San Luis Rey River.
Combining the longer portion of the Pipeline 4 relining with the portion necessitated by the new Caltrans bridge provides an economy of scale with the relining while also reducing the frequency and number of pipeline shutdowns and completing the rehabilitation of that part of Pipeline 4 ahead of schedule.
Caltrans will reimburse the CWA for the portion of the pipelines impacted by the new bridge crossing while the CWA will be responsible for the remaining costs. The estimated construction cost is $8-10 million, and Caltrans will reimburse up to $6.1 million of that.
Since the CWA aqueduct easement precedes the Caltrans highway easement, it was necessary for the CWA to grant Caltrans a right of entry permit to construct the bridge crossing. Caltrans will not have that access until the pipeline relining work is completed.
The work must be completed by May 1, 2015, to avoid delaying the Caltrans schedule, and the pipeline rehabilitation schedule includes a September 2014 start date and an April 2015 completion. Caltrans and the CWA have agreed to exchange mitigation land currently owned by Caltrans as compensation for the CWA property required for the Highway 76 project.
The environmental mitigation measures for the potential traffic, noise, and habitat impacts created by the work on the pipeline include erosion control measures, noise control barriers, temporary fencing, and traffic control.
The CWA board will certify a mitigation monitoring and reporting program along with the Mitigated Negative Declaration. The pipeline rehabilitation will also require County of San Diego access easements, Caltrans traffic control permits, and Regional Water Quality Control Board stormwater permitting.