The Town of Payson has secured a 3,000 ac-ft annual allocation of water from the C.C. Cragin Reservoir. The Town plans to divert its allocation of water from the existing Hydroelectric Power Plant, operated by the Salt River Project (SRP), on the downstream side of the power generation turbine. The water will be diverted into a new raw water pipeline (Phase I) and delivered to a new water treatment plant (Phase II). Once the water is treated to drinking water standards it will be delivered via a treated water pipeline and in-town distribution system improvements (Phase III) into the Town’s drinking water system.
Project Management Services: Sunrise Engineering worked closely with the Town to develop overall project cost estimates and a comprehensive schedule for this $42M project. In addition, the Town sought funding for this project through the Bureau of Reclamation (BoR) Rural Water Funding Program. This project was the first project through this program and required a feasibility study covering all aspects of the project including design, costs, economic analysis and environmental compliance. The BoR performed a DEC (Design, Estimating & Construction) Review on the project based on the feasibility study in which the BoR ultimately approved the project. Lastly, the project team provided support services during the preparation and approval of the Environmental Assessment (EA) for the project because most of the project resides within the Tonto National Forest. Ultimately the Town was able to obtain a Special Use Permit (SUP) from the Forest Service for all of the work on Forest Property.
The scope of work for this contract includes the final design and studies for the tailrace connection, raw water pipeline and new hydroelectric generating station (Phase I), equipment piloting and water treatment plant preliminary design (Phase II), overall project management assistance and support services as needed for other phases of the project. A brief description of each major component and service is as follows:
Tailrace Connection: In order for the Town to receive their water right a connection was necessary to the existing SRP hydroelectric facility located at the headwaters of the East Verde River. This portion of the project includes a tailrace connection concrete box, meter vault, valving, piping and other appurtenances. The challenges for this project include the limited space for construction, rock excavation and environmentally sensitive area. Our project team had to coordinate with the Tonto National Forest and Salt River Project (SRP) for the approvals on the project.
Raw Water Penstock: After the tailrace connection the project inlcuded a 13.5 mile long, 18" diameter transmission main to deliver water to a new hydroelectric facility. The alignment for the project is located adjacent to Houston Mesa Road in through the Tonto National Forest. This pipeline will be constructed of ductile iron and steel pipe due to the pressures experienced in the pipeline and longevity of the materials. In addition, the project inlcuded air/vacuum relief valves, valving and cathodic protection. Some of the challenges for this portion of the project are rock excavation, tight working conditions along the roadway, over 70 culvert crossings and 3 crossings of the East Verde River.
Hydroelectric Generating Station: Hydroelectric (renewable) power generation can be generated based on the elevation difference (approximately 550-feet) between the Tailrace Connection and WTP site and flow. At the design head and flow rate, a small Pelton turbine will produce approximately 234 kilowatts of power. The power generated will primarily be used to run the WTP and excess sold back to the power company. Sunrise worked with the Town on the preliminary and final design of this facility which inlcuded the turbine equipment selection, electrical design, valving, bypass sleeve valve design and control strategy between the WTP, tailrace connection and hydro generator.
Water Treatment Plant: Because C.C. Cragin Water is a surface water source a WTP is required to treat the water to drinking water standards. The new 4.5MGD WTP includes water storage, pre-treatment, membrane filtration, GAC polishing, backwash handling facilities, sludge handling facilities and other facilities. Sunrise Engineering assisted the Town in the site selection, membrane equipment selection (Pall Water Processing), piloting of the equipment and preliminary design of the water treatment which included site planning, hydraulic profile, process diagrams, building floor plan and preliminary design report. One challenge to the project was the need to develop a way to mitigate the creation of disinfection-by-products (DBP's) within the treated water. Our team worked to include a pre-treatment regimen of adding PACl and post-treatment with granular activated carbon (GAC) within the treatment train on the pilot to effectively reduce the DBP formation to levels well below the maximum contaminate level.