Beginning last week, there are many new sewer customers in the Marana Water system thanks to an almost complete capital improvement project. This new sewer line runs from our existing sewer system through portions of North Marana near Moore Road, down Tangerine Farms Road, underneath the Santa Cruz River, and ends at the Saguaro Bloom neighborhood off of Silverbell and Twin Peaks. This line will be able to carry a maximum of 1.8 million gallons per day allowing for growth opportunities all along the new line.
Divided into several phases, the construction of this project was no easy feat. Beginning in October 2014, the project began to be fleshed out and our Town Capital Improvement team, along with Marana Water, began working with a consultant to determine the best approach. It was then that it became clear that the project would be divided into distinct phases. When reviewing work that was previously planned on the alignment, our team resurrected a design from 2008, which was part of the planned improvements for the area but was never constructed. The original engineering firm and our new engineering firm worked together to match up their respective plans. The first phase was completed in October 2015. Additionally, there was sewer infrastructure built during the Tangerine Farms Road construction that we made sure became a part of the first phase of the project. This phase of construction included 3.5 miles of brand new 15-18” sewer main and 45 new manholes.
The second phase was approximately two miles in length. This included approximately 0.5 miles of 15” gravity main with seven new manholes, and approximately 1.25 miles of 8” force main with three new air release valves. A 1,900 linear foot portion of the force main was bored under the Santa Cruz River to depths of up to 60 feet. The completion of this project allowed for the connection of the Saguaro Bloom and the Rillito Vista neighborhoods. We had to use specialized drilling equipment, drilling mud, welding, and testing equipment on the steel casing, and a special machine to pull the casing through after the drill under the Santa Cruz River. Construction for this portion of the project began in December 2016 and there are just a few more pieces left until this is completed.
While also part of Phase II, there is another part of this project that is particularly interesting - the lift station. As part of the original Saguaro Bloom development, a lift station was constructed to pump the sewage up and over the Tucson Mountains where it would eventually be treated at Pima County’s Tres Rios Water Reclamation Facility. These types of lines are called force mains due to the pressure required to get the contents where it needs to go. Phase II described above is construction of a force main line while Phase I is a gravity fed line, meaning once the contents reach that portion of the system, gravity does all the work to get it to our Water Reclamation Facility. That pressure is provided through a system of pumps and wells called a lift station. In the new construction, instead of pumping the sewer over a mountain, we need to pump it under the Santa Cruz River and over to where the gravity flow portion begins.
In the late hours of Wednesday, May 17 and the early hours of Thursday, May 18, we tied into this lift station and began taking flows into our newly constructed line. We pumped all the contents out of the existing force main that flowed over the mountain and hauled it to an upstream manhole, cut into the existing pipe, and connected our new pipe all while monitoring flows from the neighborhood. We are proud to say this was done seamlessly and without any service disruption.
This project required substantial coordination and collaboration to ensure that it was completed properly and in the best interest of all stakeholders. We worked with the farming community on the construction of parts of the gravity line, collaborated with the original engineering firm from 2008, and, of course, with Pima County to ensure there was no noticeable change for our customers. We also took precautions to ensure the lifespan of this infrastructure. We used a specific type of pipe that is welded together rather than coupled together to prevent leaks at connection points. We added SCADA software to monitor and notify the department of any issue that might be present at the site, and we added variable frequency drives which allow for more efficient use of the lift station pumps. As part of the 2012 settlement for the Town to take over the sewer system, the transition of this area from Pima County to Marana was established. The efficiencies generated from not having the pump over the mountain and connecting to a gravity line are beneficial for both parties. The installation of this line allows for savings across the board. While there are additional testing and maintenance requirements that our wastewater staff are now taking on, the opportunity for growth in this area just expanded substantially.
The construction of this project is a great example of how we operate at Marana Water. We work in teams to provide the best outcomes, use materials and equipment that will provide long term health for our system, create thoughtful proactive maintenance plans, and ensure no noticeable change in our customer experience. We are proud to say this project came in under budget, and we are now taking the wastewater discharge into our new line. Should any Saguaro Bloom customer have a sewer related question, they will now call Marana Water at (520) 382-2570. There will be no change to the statements of the method of payment.
For all intents and purposes this project is completed. There are some minor adjustments to some of our monitoring equipment that are necessary, but the majority of the work was completed when we tied into the lift station last week. We can now incorporate this new infrastructure into our maintenance schedule and keep working hard to provide resiliency and redundancy to all of our systems.
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