Client
Location:
San Carlos, California
The Problem
Caltrans requested our infrastructure asset management expertise to restore the capacity of several large diameter storm drains along Highway 101. These storm drains had become 100% full of bay mud throughout their years of service, resulting in a loss of storm water flow capacity. During storm events, a nearby trailer park and neighborhood would become inundated with storm water flooding municipal roadways, local businesses and residencies.
Our Solution
Perform infrastructure asset management for Caltrans by cleaning the storm drains and returning them to 100% carrying capacity. Replace old tide gates so that bay tidal water could not encroach on the storm drain system – allowing for storm water to leave the system, but not infiltrate the existing system. Installation of additional manholes, which would make maintenance easier for Caltrans crews.
Project Challenges
All work had to be conducted off the shoulder of an active highway with a speed limit of 65 miles per hour. Pipe & Plant had to maintain a construction right of way that was 8’ wide and 1000’ long. We did this by using Concrete Krail Barrier and having lane closures for major ingress and egress events
Bay mud can be synonymous with quick sand. When one tries to handle this material it turns into a sludge that is consistent with drilling mud. Pipe & Plant had to develop means not only to remove this material, but also to dewater the material enough so that it could be disposed of in an economical fashion.
The nearest source of water for cleaning purposes was thousands of feet away. In addition to dewatering bay mud for disposal, Pipe & Plant developed a sophisticated onsite water recycling system where we recycled all water in the existing storm drain system for cleaning purposes… saving 5,000,000 gallons of water during the cleaning process.
Because tide control gates had become corroded and had failed, the entire surrounding storm drain system was effected by the tide. Work had to be performed in accordance with the fluctuating tides. Pipe & Plant was required to develop a cleaning plan that accommodated the tide schedule and one that could maintain the normal function of the storm drain system.
Because of the urgency of the situation, the Department of Transportation did not have adequate time to design the solution to its problems with an engineering team. PPSI furnished a Civil Engineering team to develop the design, self performed all of the work, and delivered a project on time and under budget.
