The sewer system serving Linda Vista desperately showed its age. Built too small in the 1960s, it was designed with clay pipe and loose joints prone to root intrusion and infiltration. Increased flows and surcharge conditions from ongoing development posed an increasing threat to public health. Planners and developers realized they were dealing with compound challenges—and called on Harris & Associates for a holistic solution.
Completing the project would involve high-volume traffic through multiple intersections, congested utility corridors, four trenchless crossings, easement acquisitions, sewer bypassing, environmental studies and permitting, and many other construction challenges.
Harris designers applied a constraints matrix analysis to identify alternatives for each challenge and selected the most robust technology—minimizing time and costs. Designers used trenching where possible. Pipe alignments were selected to meet separation criteria and facilitate traffic control during construction and future manhole maintenance.
Altogether, Harris and the District successfully realigned approximately 3,400 feet of surcharging 8-inch clay sewer mains and 14 manholes with 15-inch PVC trunk sewer.
The $2.6 million project engaged District leaders in every detail. Harris designers led coordination with all agencies and stakeholders to provide a single line of accountability and ownership on all issues.
The project included:
Using different methods depending on the challenges of each segment, including trenchless crossings, jack and bore and hand tunneling
Identifying proper approaches to expedite the Mitigated Negative Declaration and permitting from Caltrans, San Marcos, Encina and Vallecitos Water District
New easement acquisitions
Building sewer replumbs
Coordinating with city officials, hotel developers and local business owners
Removing the infiltrating and surcharging sewer facilities cut sewer flows by about 50 percent along the alignment and reduced flows significantly through pipelines, pump stations and the treatment plant at the coast.
The project reduced costs to taxpayers, spill potential and maintenance efforts.
And plans by the City of San Marcos to enhance the Creekside corridor with planned redevelopment of the commercial and industrial area are underway.
Beyond the Blueprints
Minimizing construction impacts is always a challenge. Excessive damage requires replacement of the pavement via a grind and cap method. To divert this issue, Harris used a highly filled polymer-modified asphalt emulsion to fill in minor cracks and gouging caused by construction equipment prior to slurry seal of the roadway.
This reduced the amount of pavement Harris needed to grind out and replace—keeping the project schedule on track, reducing added costs incurred to the contractor and providing the city with a fully functioning, highly efficient new sewer system.