Construction is set to begin before the end of the year and continue through 2011 on a pipeline tunnel, flow regulatory structure, stabilized river crossing and relining of an existing pipeline in Mission Trails Park.
The San Diego County Water Authority awarded a $20 million contract to LH Woods & Sons, Inc. to complete tunneling for a new pipeline and the relining of an existing pipeline.
Another contract worth $26 million is out to bid for the remaining projects, said Jack Neely, Construction Administrator for San Diego County Water Authority.
The project includes construction of a new tunnel for a pipeline that failed in May of 2006.
The pipeline, which conveys water from both the Delta region and Colorado River, has not been operational since failing.
The new pipeline will operate more efficiently than the previous one due to its continuous slope. While the previous pipeline moved up and down with the contours of the landscape, the new structure will convey water along a constant incline, eliminating the need for pumping along the way, Neely said.
Vista-based contractor LH Woods & Sons plans to construct the pipeline by drilling and blasting rock. The company is very experienced with the type of work, said Shane Sato, project manager at LH Woods & Sons.
The contractor is also relining a segment of a pipeline that it originally constructed in 1959, between State Route 52 and Lake Murray.
Despite the company's familiarity with tunneling there is always the possibility of unforeseen challenges, Sato said.
"Anytime you're working underground you can encounter changes in the rock or unexpected groundwater," Sato said. "Then we have to change our means and methods."
In completing the project, LH Woods & Sons will be working closely with San Clemente-based Foxfire Constructors, Inc. along with a variety of other subcontractors.
The new pipeline will also allow for removal of two vent structures standing more than 20-feet tall. The highly visible blue vents will be replaced with four-foot tall air vacuum valve structures, said Craig Balben of the San Diego County Water Authority.
Both pipeline projects are fairly routine for the Water Authority. At least one pipeline is relined each year, Balben said.
The second Water Authority project currently out to bid includes construction of a flow regulatory structure with the capacity to store 12 million gallons of water, as well as a stabilized Arizona River Crossing.
The installation of a concrete slab will make it easier for park officials and emergency vehicles to access the park during periods of low flow on the San Diego River.
The Water Authority was required to mitigate the impact of the river crossing due to the sensitive habitat found around the San Diego River. The environmental impact report required the Water Authority to mitigate the impact on species of butterflies and gnatcatchers found in the area.
Recreational use of Mission Trails Park will also be impacted by the project. Once construction is underway, access to many of the hiking and biking trails in Mission Trails Park will be limited. The park entrance and parking lot on Clairemont Mesa Boulevard will be closed between 7 a.m. and 7 p.m., except on Sundays. Alternative access will be available at Calle De Vida off Corte Playa Catalina in Tierrasanta.
The project's extensive impact on recreational use of the park is unprecedented, Balben said.
"I don't recall a project like this ever before where the hiking trails have been impacted so significantly," Balben said.
More information on the project and trail closures is available at: http://missiontrails.sdcwa.org