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Board picks two Gila diversion projects

SILVER CITY – The local board in charge of plans to divert water from the Gila River decided Monday to pursue a combination of two projects that may cost less but would also deliver less water than planners originally intended.

Facing a Friday deadline to inform the Bureau of Reclamation of its plans, the New Mexico Central Arizona Project entity selected alternatives for further study that would, together over the long term, divert water from a northern point on the river to storage areas underground and in one or two canyons.

Contract engineering firm AECOM estimated the initial phases of the projects would cost $84 million and $82.5 million, respectively – although there is expected to be significant overlap in the infrastructure. Total cost for each alternative fully built, but excluding potential savings due to overlap, is $366 million and $336 million, respectively, according to the AECOM analysis.

An estimate for the combined project, stripping out duplication, was not discussed but would be significantly less than the totals added together, said NM CAP entity Executive Director Anthony Gutierrez.

New Mexico is entitled to an average 14,000 acre-feet of water per year under the Arizona Water Settlement Act, and the act allots the state up to $128 million to pursue a diversion.

NM CAP entity board members made it clear at a recent meeting that they wanted a project that was “feasible” with a budget of $80 million to $100 million and a yield of up to 4,000 acre-feet. Together, the projects selected would yield in their initial phases up to 1,800 acre-feet annually and in the longer term up to 3,000 acre-feet, according to AECOM estimates.

At one point, the Bureau of Reclamation had estimated the cost of a major diversion could reach $1 billion. The CAP entity’s chosen alternatives scale back the size and scope of the diversion and storage systems.

Should the project costs exceed the settlement funding available, it’s not clear where the additional funding would come from. It’s also not clear what the water would cost likely beneficiaries: local farmers and ranchers.

Gutierrez recommended the two alternatives, and the board agreed unanimously with his choices. Now the plans go to the Bureau of Reclamation for a multiyear review under the National Environmental Policy Act, or NEPA.

Gutierrez told board members that in making their decision, they needed “to consider the long-term goals and needs of southwest New Mexico” and noted that the day’s decision “is only a steppingstone for decisions to be made by people who are going to outlive us all.”

The entity could take 50 years to fully build out the diversion and reservoir projects, he said, spreading the higher costs across decades.

Todd Schulke, co-founder of the Center for Biological Diversity and an advocate for Gila River protections, said the projects are “additive” and the costs must be summed with the cost of operation and maintenance over 30 or 40 years – costs not included in the top-line AECOM estimates.

“You have two roughly $350 million projects on opposite sides of the river, and the only common piece of them is the diversion,” he said, noting that plus the operation and maintenance costs, “when you add all those things up, yeah, it’s less than a billion dollars but not a lot less.”

Gutierrez disputes that.

The storage canyons contemplated in the different projects “are an either-or option – not both,” he said, and the storage reservoirs are the biggest cost to each. “The existing infrastructure won’t have to be rebuilt.”

The board’s primary choice – “alternative No. 4” – would divert water at a bend in the river called the Gila Gage, move it into infiltration ponds for storage in an “aquifer storage and recovery” system, which is like a reservoir underground but the water keeps flowing. In a later phase, the project would add a reservoir in Winn Canyon on the west side of the river farther south.

A second, overlapping choice – “alternative No. 1” – would use the same Gila Gage diversion to pipe water into a reservoir in Upper Spar Canyon on the east side of the river, also farther south.

The board members asked questions of engineers about how quickly the water would be available from diversion to storage under the different alternatives and about whether the infiltration ponds could be made to look natural in an area that is popular with hikers and campers.

Of particular concern was competing data regarding elevations of the diversion and reservoirs, which has bearing on whether the projects use gravity conveyance – much cheaper than pumping and lifting water from one spot to another.

The alternatives presented by engineers represent minimal design and leave a number of questions unanswered. Engineers and Gutierrez told the board that many of the design details will be worked out through the NEPA process.