Mesa Road Trunk Sewer Project
In order to accommodate increased system flows and improve wetland protections for Goleta Slough, Goleta West Sanitary District will be replacing and relocating a main sewer line along Mesa Road. The District hopes to begin construction of the project in the spring/summer of 2013.
The existing collection system includes a 33-inch gravity sewer line located just south of Mesa Road between Los Carneros Road and the District headquarters.The line was constructed in 1966 and is located in a wetlands area of the Goleta Slough.
As part of the District’s planning efforts a hydraulic analysis was performed on the entire sewer collection system. The purpose of the analysis was to identify GWSD facilities that do not meet the District’s design capacity standards. Those standards were adopted to ensure that the collection system is sized to convey peak wet weather flows in order to protect against sewer system overflows. The aforementioned 33-inch sewer was identified as not meeting the design capacity standard under existing, ten year and build-out flow conditions.
In the past, groups such as the Goleta Slough Management Committee have encouraged the District to relocate the sewer line out of the environmentally sensitive wetland area.
After receiving the results of the hydraulic analysis, GWSD determined that the environmental concerns could be addressed concurrently with increasing the pipe size. The Board of Directors decided to relocate the new pipeline into Mesa Rd.out of the wetland area and to abandon the existing 33-inch pipeline. While this alternative was determined to be more costly, the environmental benefits are significant thus making this approach the overall best solution.
District Consultants are nearing the end of the design and permitting portion of the project. The engineer’s estimate for the project is $9 million.
Mesa Road Pipeline Replacement Project Begins This Summer
Western Goleta and Isla Vista’s wastewater lines flow like tree branches from neighborhoods, commercial properties and through some of Goleta’s most prized open spaces. Eventually, these all feed into one major “trunk” pipeline, beginning near the intersection of Los Carneros and Mesa roads. This main line adjacent to Mesa Road flows to the District headquarters pump station. The wastewater is then pumped to the regional treatment plant, east of the Santa Barbara Airport terminal.
In 2007, Goleta West completed a Wastewater Master Plan, which determined that the capacity of the “Mesa Trunk Sewer Line” should be increased to ensure that the system is sized to convey future peak
wet weather flows. A plan was then put into motion to replace the old 33-inch line with a 42-inch pipeline and to relocate it out of the wetlands and into Mesa Road
Construction begins this summer.
For years, the District has set aside funds for capital improvement projects like this one. The cost to replace the Mesa Trunk Sewer is estimated to be approximately $9 million, and it will be paid entirely from our reserve funds.
Pipeline Relocation = Wetlands Benefit
Currently, the existing line is located just south of Mesa Road in the East Storke Wetlands, an environmentally sensitive habitat located next to the Goleta Slough Ecological Reserve. In the past, community groups such as the Goleta Slough Management Committee have encouraged the District to relocate the trunk line out of this environmentally sensitive area. Agreeing, the District’s Board of Directors made the decision to abandon the old line and relocate the new larger pipeline out of the wetland area and underneath existing Mesa Rd. This relocation will also provide for improved maintenance access to the facilities. The Goleta Slough Management Committee has been consulted on this project. Founded in 1991, the Committee’s purpose is to work cooperatively with regulatory agencies, property owners and public interest groups to provide for a healthy Goleta Slough, considering the Slough’s ecosystem and recognizing a mixture of land uses. Pat Saley, the facilitator of the Slough committee says: “The Goleta Slough Management Committee has supported relocating sewer lines out of wetlands since our inception over 20 years ago. We see this as a win-win project for two reasons. First, access and maintenance of the sewer lines will be much easier once they are relocated outside the wetland. Second, the habitat will also benefit by eliminating sewer line maintenance work in the wetland.”
Using Modern Technology
Due to unstable soil conditions, a process called “microtunneling” will be used to install the new pipeline underneath the existing pavement of Mesa Road. The process is similar to installing a new sewer lateral from one’s home to a system main via trenchless technology. Simply put, there are two excavation points – at the beginning and the end of the line. The microtunneling machine is placed in the launch shaft (see Figure 1); the machine bores a subterranean tunnel thru the soil. Pipe segments are then lowered into the shaft and installed into the newly bored tunnel. The process continues until reaching the retrieval shaft.