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Pipe inadequate for 2 hookups to CAP, city says

2014-02-26 14:34:45   COMMENT:0 HITS:
An existing pipeline at a Sahuarita-area groundwater recharge project isn't nearly big enough to carry all the Colorado River water that two other parties say they want to put into two proposed connecting pipelines, Tucson officials said Tuesday.
The City Council unanimously agreed Tuesday to tentatively adopt 11 criteria for deciding who gets to hook their pipeline up to an existing pipeline, serving the Pima Mine Road Recharge Project, that's owned by the city and the Central Arizona Project. The council will have to formally adopt them later, after the city staff incorporates some changes the council wants in the criteria.
Before the vote, Tucson Water officials told the council that the utility's 36-inch existing pipeline can't accommodate both 36-inch pipelines that Farmers Investment Co. and Community Water Co. of Green Valley have proposed to take CAP to southern Pima County. Community Water Co. plans to recharge CAP water to compensate for groundwater pumping that Rosemont Copper will do for its proposed mine.
Both pipelines would parallel Nogales Highway from the Pima Mine recharge site - CWC's for seven miles, FICO's for 3 1/2 miles at first and up to nine miles later. The limited capacity might help FICO more in the next few years but prove more advantageous to Community Water later.
The city's current pipeline has a capacity of 40,000 to 42,000 acre-feet. About 30,000 acre-feet goes through the city CAP pipeline annually, leaving 10,000 to 12,000 unused space in that line or maybe a little more.
While that fact has several potential implications, the ultimate bottom line is that these pipelines would not be immediate cure-alls for the perennial groundwater overdraft that has plagued Sahuarita-Green Valley since the 1970s due to pumping by FICO's pecan groves, existing copper mines and suburban development.
"From a hydraulic point of view, it makes no sense to connect two 36-inch lines to an originating 36-inch line," said Chris Avery, a principal assistant city attorney. "Typically, pipelines get smaller, not larger as they go out."
Avery said this determination was made by several engineers for Tucson Water, including Director Alan Forrest.
"This is why it's important to have these discussions about the pipelines with their actual applications, and why it's important to have these criteria adopted by the mayor and council," he said, since the criteria will take the existing line's limited capacity into account.
Asked how both pipelines could succeed based on the limited amount of water capacity available, Avery replied: "I don't know. That's something they'll have to figure out."
In the short run, FICO officials say, the limits on pipeline capacity argue for their project, because if they could get access to all the CAP water that could be carried by the existing pipeline, it would eliminate a substantial share of the pecan groves' contribution to the regional overdraft of groundwater.
"We agree that there's no room for two pipelines. It doesn't make any sense if you are going to have half of that CAP capacity going to someone speculative who doesn't have a recharge permit," said FICO spokesman David Steele, referring to the fact that Community Water could be up to a year away from getting a state permit to build recharge basins to store whatever water it brings in. By contrast, FICO has had a state permit to put CAP water in the pecan groves for more than a decade.
In the long run, however, Community Water may have more ability to adapt to the limited capacity of the existing city pipeline. That's because Community Water plans to ultimately connect its pipeline at the westerly CAP terminus near Interstate 19 and run it over the Santa Cruz River to where it would go south to its recharge basins. That work will be done in about five years, after a new bridge is built over the Santa Cruz River that could handle a new pipeline.
Raul Piña, project manager for Community Water's project, noted that in 1998, a study done for Tucson said a 66-inch line is needed to take enough water to make a serious dent in the Green Valley area's groundwater overdraft.
"There is now one 36-inch line, and we will build one line to parallel that 36-inch line, and that will come close" to the 1998 recommendation, Piña said. "These two pipelines are not competing - you need to bring that much water into the area."
FICO, by contrast, says it has designed its pipeline only to connect at the Pima Mine Road recharge facility area with the existing city-CAP line. It's not planning to build an extension of that line to the CAP terminus. The pecan growing company is hopeful that once the improved bridge is built, that would give the existing pipeline possibly 8,000 acre-feet more capacity. That would still give only 20,000 acre-feet of CAP for use on the pecan groves, and no more room for additional water to offset pumping by other mines, golf courses and subdivisions.
On the other hand, if Community Water can use only its current allocation of 2,800 acre-feet, that won't even be enough to offset all of Rosemont's planned groundwater pumping of 5,000 to 6,000 acre-feet per year, Steele said.
CAP water: Comes via a massive system of canals and pipelines from the Colorado River to serve Tucson's needs, and then to a terminus at Pima Mine Road and Interstate 19 near Sahuarita.
CAP recharge: Placement of the water into basins to seep down and replenish the aquifer.
Overdraft: State law requires the Tucson area to stop using more groundwater than it replaces by the year 2025.
An acre-foot: Enough water to serve two to three households for a year.
Farmers Investment Co., or FICO, grows pecans in the Sahuarita area. It opposes Rosemont Copper's proposed open-pit mine southeast of Tucson, partly because they're in competition for CAP water.
Community Water Co. of Green Valley is working with Rosemont Copper's parent, Augusta Resource Corp., to develop a CAP pipeline to Sahuarita-Green Valley to compensate for the mine's pumping. The private water company wants access to the water in part to serve suburban development.

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