The cities of Carlsbad and Vista are teaming up to replace a segment of critical infrastructure along Carlsbad’s coastline that conveys up to 33 million gallons a day of wastewater to the Encina Water Pollution Control Facility.
Work on the Avenida Encinas Sewer Improvement Project began in January in Avenida Encinas just south of Cannon Road. Construction will be performed in segments along Avenida Encinas extending from the Encina Water Pollution Control Facility and ending just north of the Agua Hedionda Lagoon near Chinquapin Avenue. The work is anticipated to take about two years.
The project improvements include the installation of approximately two miles of new sewer pipeline that will carry wastewater from the north shore of Agua Hedionda Lagoon to the Encina Water Pollution Control Facility on Avenida Encinas. Construction crews will lay the new 54-inch diameter pipeline beneath Avenida Encinas using a combination of open trench construction and an underground tunneling method to minimize impacts to local businesses, residents and visitors.
“There will be some equipment at the tunnel shafts, but tunneling the pipeline will have less traffic impact than open trench construction,” said City of Carlsbad Senior Engineer Terry Smith, the project manager. “Crews will try to maintain an open lane of traffic in each direction along Avenida Encinas during construction, and we’ll keep nearby businesses and residents informed as work progresses.”
During pipeline work, the City of Carlsbad will also install a new, 11,000-foot recycled water line to enhance the city’s overall goal of improving water conservation through the expanded use of recycled water. This line will connect with other existing pipelines and accommodate future recycled water expansion to areas such as Carlsbad Village.
The project also includes replacement of the old Agua Hedionda Sewer Lift Station on the south shore of the lagoon with a new facility that will improve reliability and increase system capacity. Lift stations include pumps that raise wastewater to higher elevations so that it can then flow by gravity to the water pollution control facility for treatment.
Crews will also construct a new 140-foot single span steel bridge across the Agua Hedionda Lagoon to support pipelines for wastewater, recycled water and other utilities. The new bridge will be wide enough to accommodate a maintenance vehicle and a future segment of the Coastal Rail Trail, the planned route that will eventually run 44 miles between Oceanside and San Diego. The new single span bridge also will improve the lagoon’s tidal flow with the removal of the existing wooden trestle bridge.
“This is a significant infrastructure improvement project, but there will be large periods of time where people won’t see much construction work because some of the project area is inaccessible to the public,” said Smith. “Agua Hedionda Lagoon Lift Station, for example, the city’s largest, is largely obscured from public view.”
The original Vista/Carlsbad interceptor sewer system was constructed in 1965 and is jointly owned by the cities of Vista and Carlsbad. The two cities have been upgrading the system in stages and have improved the pipes and pumps north of Agua Hedionda Lagoon.
The Carlsbad City Council awarded the approximately $44.2 million construction contract in May after a competitive process to Pulice Construction.
The cities of Vista and Carlsbad are sharing the $64.2 million project cost, with two-thirds of the project is being funded by the City of Vista, and the City of Carlsbad providing the other third. NRG Energy is also contributing $1 million to have access to a recycled water line. Carlsbad’s contribution is approximately $25 million.
The project includes:
A new 33 million gallon-per-day lift station on the south shore of Agua Hedionda Lagoon, which will increase the station’s capacity by 50 percent to meet future demand. The new lift station will include eight pumps, which will help ensure against possible spills.
Construction of a new pressurized force main and gravity sewer that parallel the existing line and will expand capacity to meet future demand. The city has inspected the existing 42-inch diameter pipe and upgraded it by installing a new liner in the manholes to bring it up to modern standards and guard against leaks.
Construction of an 11,000-foot recycled water line that will extend from the Carlsbad Water Recycling Facility on Avenida Encinas to the new bridge over the lagoon. The pipe will deliver recycled water to customers along Avenida Encinas and to the future Carlsbad Energy Center, and will intersect with the existing recycled water lines in Palomar Airport Road and Cannon Road. It will also make it possible to deliver recycled water to Carlsbad Village in the future.
New pavement overlay on Avenida Encinas after the project is complete, including new restriping to incorporate bicycle lanes.