Mesa moving on massive pipeline for more water

Jun. 20—Mesa city officials have been talking about the Central Mesa Reuse Pipeline for years, and the big infrastructure project may take a step closer to reality tomorrow, June 20, when City Council will consider selecting a contractor for the project and awarding $3 million for preconstruction services.

When finished, the planned 3-foot-wide underground pipeline would move millions of gallons of reclaimed wastewater a day 10 miles south from the Northwest Wastewater treatment plant at Thomas Road and Val Vista Drive for ultimate delivery to the Gila River Indian Community's agricultural fields.

With an estimated $90 million price tag, the project is a major undertaking, both financially and in terms of public inconvenience during construction, which could last up to two years.

But the city believes the costs and impacts will be worth it, potentially expanding Mesa's access to Colorado River water at a relatively cheap price.

That's vital for continued growth, leaders say, particularly for southeast Mesa, where industrial growth is rapid and current and prospective users are seeking access to large volumes of water.

Following a study of routes, officials selected a path for the pipeline completely within city rights-of-way beneath public streets, meaning crews will have to dig up portions of roadways to install the pipeline.

The pipeline route heads south down Val Vista Drive until McLellan Road, where it turns east before arriving at Greenfield Road via 40th Street and Brown Road. The pipeline then follows Greenfield Road south, crosses US 60, then turns southwest before connecting with an existing pipeline at Recker and Houston Roads.

Supervising Engineer Jesse Heywood said construction on the pipeline is planned to begin May 2023.

"Construction will be phased to limit traffic impacts," a staff report to council states. "Public access will be maintained to businesses and local streets as required per contract documents. Additional street impacts include potential left turn restrictions, lane closures and other temporary restrictions."

Three construction companies submitted Statements of Qualification in July of 2021, and city staff recommend awarding Garney Companies Inc the contract. Garney's Arizona office is located in Mesa, and the company is one of the city's current utility construction service providers.

The council report states that a Guaranteed Maximum Price for the project will be set during the last phase of the preconstruction process.

City Manager Chris Brady told the council in 2021 that the pipeline project would likely be fully or partially funded by future bond packages.

Reclaimed water

Many cities in the Southwest are looking to their treated effluent water to stretch their water portfolios, using reclaimed water to irrigate places like golf courses and city parks — locations that might otherwise use drinking water.

Mesa's Northwest water treatment plant can churn out up to 18 million gallons of effluent a day, but the city has a problem: it currently has limited options for delivering that water.

It lacks infrastructure in the form of pipes to send it around the city for beneficial uses.

Most of the Northwest Water Reclamation Plant effluent is currently sent underground via the Salt River Project's Granite Reef Underground Storage Project, a basin at the Salt River bed where surface water is absorbed into the aquifer.

When a storm in 2020 knocked GRUSP offline, Mesa sent effluent down the Salt River channel for about a year.

While storage has benefits — Mesa Water Resources Director Chris Hassert told city council in May the city has banked almost six years' worth of water underground and managers think they can make the city's effluent work harder by building the Central Mesa pipeline.

Mesa has a 99-year deal with the Gila River Indian Community to trade effluent water for Colorado River water credits from the Central Arizona Project. With the new pipeline, Mesa would be able to increase the effluent it trades to GRIC from 6,800 acre-feet per year to as much as 20,000 acre-feet, Hassert said.

Mesa only gets 80% of the water it sends to GRIC back in CAP credits, but city officials still consider that a bargain, since delivering the treated effluent costs them less than it would to buy the CAP water at market rates.

Betting on the Expensive Option

City officials studied a less costly way to deliver Northwest plant effluent to GRIC via an existing canal but rejected it in favor of a new pipeline using rights-of-way beneath city streets.

The rejected option was to make an agreement with the Roosevelt Water Conservation District to share its main canal, which begins near the Northwest water treatment plant and runs to GRIC at Hunt Highway.

Mesa's consultants estimated $20 million in canal improvement would be necessary to transport Mesa's effluent, plus several smaller projects needed to make it work.

The upfront costs of forging a water transport agreement with RWCD were lower than those of building the pipeline. Even factoring in costs incurred over 40 years, including transport fees and water loss, the canal was figured to cost $18 million less than a pipeline.

A study prepared by Dibble Engineering in November 2020 reported that RWCD was willing to share the costs of canal upgrades and work with the city to resolve other issues associated with transporting the city's effluent.

But based on a scoring system of the different alternatives that awarded points for different categories like cost, risk and autonomy, Dibble ranked the pipeline under city streets No. 1, and the city went with that recommendation.

The pipeline scored particularly high on autonomy, meaning the city is in greater control of its own pipeline than a shared canal. A pipeline owned by the city requires fewer legal agreements with outside entities.