La Jolla Ecological Reserve Low Flow Diversion Project

Residents of San Diego were quietly suffering low flow stormwater contamination impacts at one of their most cherished natural assets. Nearly two miles of environmentally sensitive shoreline in La Jolla was under siege, and the area was designated as one of California's sites of special biological significance. Urban runoff was threatening more than 450 acres of protected marine habitat as well as the local beach economy.

That's all history, thanks to the La Jolla Ecological Reserve Low Flow Diversion Project where Harris & Associates was proud to participate by designing a key solution to this problem. Now contaminated low flows are safely diverted to the sewer system for treatment. People, wildlife and jobs are all protected.

Core Elements

Harris & Associates project-managed this vital initiative, which required:

• State-of-the-art sensing and control technology to prevent sewer system overload
• Pilot-tube-guided boring trenchless technology
• Custom-designed vaults
• Scientifically-based design features

Low flow diversion is still a nascent field, so all assumptions, calculations, technical design and constructability were extensively scrutinized prior to bidding. Still, Harris completed the $4.8 million project on time and on budget.

Beyond the Blueprints

People take more than 57,000 motorized vehicle trips each day, dodging heavy bicycle and pedestrian volumes on the scenic Torrey Pines Road in La Jolla, where construction was required. Harris worked closely and collaboratively with the City and contractor and community throughout the project. Harris scheduled the project so that construction avoided the community's summer beach moratorium on construction, and designed traffic control to incorporate the newly-adopted Sharrow lane to protect and maintain safe bicycle traffic through the site. The Harris design also included trenchless technology and minimized footprint that allowed daytime construction so vibration and noise would not disturb residents’ sleep.

Harris designed solutions throughout the project to accommodate existing deep and congested utility constructions. Harris also provided on-the-spot engineering solutions to mitigate the impact of several significant undocumented utilities which challenged construction feasibility and schedule. A deep vault had to be constructed within inches of beam-and-lag shoring to retain three stories of earth, coordinated closely with an adjacent multimillion-dollar multi-story underground construction immediately adjacent to the shoreline.

These types of design innovations and a collaborative working relationship with the community, helped make this project a success worthy of local and national recognition and, more importantly, deliver water quality benefits to the region for decades to come.