City of Los Angeles Ready to Build Redundant Force Main for Their Largest Pump Station
By Alec Mackie, LABS Corporate Director
The City’s Bureau of Engineering has completed design work on a critically needed second sewer force main to manage peak flows from the Venice Pumping Plant to the Hyperion Wastewater Treatment Plant. The City is ready to start building the $60 million, 2 mile force main but a new court case has stopped the project.
During a luncheon presentation on June 24th to members of the Los Angeles Basin Section (LABS) of CWEA, Sean Zahedi , PE, Engineer for the City, explained the three potential routes and construction methods. Ultimately the team selected micro-tunneling and the Via Marina route as having the least impact on the environment and neighborhood.
The Venice Pumping Plant is the City’s largest handling 36 mgd (1500 l/s) and a critical link in the Coastal Interceptor Sewer. Sean noted the facility is in great condition, has plenty of capacity and handles wastewater from Pacific Palisades, Venice and Marina del Rey. The City even uses the original, massive Fairbanks-Morse pumps from the 1950s thanks to careful maintenance and rebuilds.
Less is known about the 50 year old, 48” reinforced concrete force main. It is the only link to Hyperion and cannot be shut down for inspections or maintenance because flow is too great, Sean said. Moreover, the single pipeline carries only 60% of the pumping plant’s ultimate capacity, so without a second force main the system is susceptible to a breakdown or heavy storm flows. Either could cause an emergency situation.
The Bureau of Engineering examined three routes for the new pipeline – along the beach, Pacific Avenue and Via Marina. The beach route was problematic because it disrupts beach goers, impacts a Least Terns colony and is susceptible to beach erosion. The Pacific Avenue route is direct but very difficult for construction since it is a small two lane avenue with homes close to either side. Construction would block access to homes and finding locations for boring holes would be difficult – homes were close to each side. Construction could also mean the loss of parking for several blocks.
The Team selected the Via Marina route. The 4 lane street has plenty of room for access and would be the least disruptive. The City engineering team also chose a combination of micro-tunneling and cut and cover to complete the project – carefully balancing the cost (microtunneling is more expensive) with the disruption to the public (cut and cover can be disruptive to traffic).
Sean noted there would be 12 boring holes to manage the tunneling, with depths from 15 to 70 feet for both jacking and receiving. The longest tunnel drive length will be 1,764 feet long. There will be about 1,000 feet of cut and cover trenching. City engineers spent a year talking with local residents and businesses and getting their input on the project.
Currently the County of Los Angeles has taken the City to court challenging the Environmental Impact Report and the project is on hold.
The luncheon also featured a presentation by Hadronex President David Drake about remote sewer monitoring. David’s full presentation, including audio will be available on the LABS website at www.labsofcwea.com.
The luncheon was sponsored by BioCope Inc www.biocope.com.
