Venice Dual Force Main
To avert potential sewage spills that could occur due to an overflow or failure of a 60-year-old 48-inch force main, the City of Los Angeles Department of Public Works developed the Venice Dual Force Main Sewer Project. Planning for this project began nearly 20 years ago, anticipating growth in the area and the critical need to manage increased capacity on the City’s sewage system. The design by Brierley Associates involves construction of a new 54-inch sewer main operating parallel to the existing 48-inch main. The total pipeline spans over 10,000 linear feet in length, beginning at the Venice Pumping Plant, crossing under the Marina Del Rey basins, and ending at the Coastal Interceptor/North Outfall Sewer (CIS/NOS) Junction. To support this project, Geneva manufactured 1,710 feet of 72-inch diameter reinforced concrete jacking pipe to be used as casing pipe, which would host the new 54-inch pressurized force main.
Microtunneling was selected as the primary construction method for more than 90% of the two-mile long pipeline. Only 150 feet of the project required open trench construction. Trenchless methods create a smaller construction footprint and minimize surface disruptions such as road closures and noise, making it an optimal application for the densely populated beach town. Microtunneling is also ideal for installation under high ground water conditions, which is essential in the Venice Dual Main Project. Due to the coastal geography of the region, the project crosses below 15 to 30 feet of groundwater in certain sections.
Our team worked with Hamilton Kent to determine the optimal joint design for this project to prevent chances of infiltration and inflow (I&I) during installation. The final joint design consisted of a confined O-ring gasket and a steel bell band, and had a hydraulic pressure rating of 50 psi. The steel bell band allowed a larger concrete surface to disperse the jacking forces, while the specially designed gasket allowed for optimal hydraulic performance.
Due to existing site constraints, this job requires both a vertical and horizontal curve, which increased the technical requirements of the jacking contractor, Vadnais Trenchless Services. Despite these complexities, the experienced Vadnais team continued to apply their specialized microtunneling expertise to meet all the unique needs of this project.