The Val Vista Water Transmission Main program is being constructed in three phases sequential to one another, originating at the Val Vista Water Treatment Plant, and includes 8 miles of 72” to 48” diameter waterline. The project is located in the “City Zone” which is the City of Mesa’s largest pressure zone. Once the program is complete, this new pipeline will be capable of delivering 90 MGD of water from the Val Vista Water Treatment Plant that is operated by the City of Phoenix to three City of Mesa reservoir and booster pump stations.
Upon completion of the program, these three continuous pipeline segments will serve as a “stand alone” City of Mesa water conveyance system and will fulfill the requirements of an existing inter-local agreement between the City of Mesa and City of Phoenix. Upon completion of each segment, there will be permanent disconnects from the existing City of Phoenix transmission system that assisted previously with water transport to the terminal locations. Consequently, the City of Mesa will be afforded the opportunity of operating their water distribution system much more independently from the City of Phoenix’s operations.
Phase 1 of the program is considered the most critical of the three waterline segments, as water must be conveyed through this pipeline prior to reaching either of the three terminal reservoir / booster pump stations. This project originates at the Val Vista Water Treatment Plant with a 72” connection and extends south along Lindsay Road for 10,845 LF before connecting to the City of Mesa’s existing 42” waterline. Thereafter, the existing 42” waterline continues south to the existing Lindsay Pump Station. Just north of the 42” connection at the intersection of Brown and Lindsay Road, the Phase 1 transmission main tee transitions and reduces to 60” diameter extending west along Brown Road for another 2,402 LF, terminating near 24th Street just west of the Mountain View High School. This terminal point is the start of the Phase 2 segment.
The scope of Phase 2 consists of 10,155 LF of 72”, 2,402 LF of 60”, and 160 LF of 42” C303 pipe. In addition, the project included 530 LF of 94” diameter tunnel liner plate installation, three large diameter isolation valves, five 8” and 10” combination air release assemblies, five dewatering standpipe assemblies, and ten 30” access manways along the pipeline route. In addition to the mainline installation, there was 100 LF of 30” C303 piping installed related to the TS-3 interconnect. This portion of the work entailed final connections to an existing 60” ductile iron pipe section and existing 30” C303 pipeline.
Outside of the pipeline segments, a complete surge protection system was implemented at the existing Lindsay Pump Station. This included placing a 6,000-gallon surge tank, drywell installation, various structural concrete, electrical, mechanical piping, and interconnection to an existing 48” PCCP line. This system was designed to protect not only the newly installed pipeline, but also the existing distribution mains from the potential of catastrophic failure during a complete power outage causing immediate shut down of the service pumps.