Thirsty for new recycled-water projects, Palo Alto, Mountain View and other Peninsula cities are rethinking old partnerships, exploring new technologies and considering new collaborations that would expand the existing "purple pipe" system into new areas.

Few area cities are as enthusiastic about the potential of recycled water as Mountain View, which is one of the partner agencies in Palo Alto's Regional Water Quality Treatment Plant. Mountain View already uses recycled water from Palo Alto to irrigate Shoreline Park and it plans to extend its purple pipe system to areas near Moffett Field and the Sunnyvale border in the coming years.

Palo Alto, which uses recycled water at the municipal golf course and Greer Park, is also eyeing its own expansion of the system, possibly to south Palo Alto and the Stanford Research Park. At the same time, the city and its partners are preparing to fund a study that would evaluate various ways to improve the quality of the recycled water by running it through an additional filtration process such as reverse osmosis or microfiltration. Both processes are already in use at the Silicon Valley Advanced Water Purification Center, a water-treatment plant that opened in San Jose in 2014.

In the northern part of county (and the East Palo Alto Sanitary District, which is also served by the Palo Alto plant), the cities are just beginning their march toward a purification system of this sort, an effort that will be informed by a feasibility study that the city is now embarking on (the contract is scheduled to be awarded this summer). But while they are exploring a joint investment in water-treatment improvements, each city is also pursuing its own specific goals.

Mountain View, which is among the leaders in the field, expanded its recycled-water system to Shoreline Park in 2009. Today, the city distributes about 400,000 gallons per day of recycled water to the area north of U.S. Highway 101 in the North Bayshore Area, according to Gregg Hosfeldt, assistant director of public works.

Hosfeldt also noted at the March 29 meeting of the Joint Recycled Water Advisory Committee (a new group that includes representatives from Palo Alto, Mountain View, East Palo Alto and the Santa Clara Valley Water District) that Mountain View now requires companies that are located in an area where recycled water is available to use that water for irrigation.

Given the existing use and plans for expansion, Mountain View has requested an extension in the city's agreement with Palo Alto, which was signd in 2005 and currently runs to 2035. The extension, which the Palo Alto City Council considered on Monday night, would stretch the expiration date until 2060. It will entitle Mountain View to 3 million gallons of recycled water per day, same as in the current agreement.

While the two cities agree that recycled (and purified) water are the way of the future, current plans remain somewhat murky. During a long discussion Monday night, Palo Alto officials balked at approving the extension of its agreement with Mountain View and directed staff to take a fresh look at the contract.

Specifically, council members wanted to make sure that the contract can accommodate a situation in which the partners pursue different visions for recycled water and disagree on the types of capital investments that need to be made at the plant.

During the discussion, Vice Mayor Greg Scharff was the leading critic of the proposed extension as he pushed Public Works staff to provide reassurances that the new contract will not constrain Palo Alto's options for future water projects.

Scharff noted that by 2060, Palo Alto will likely move from recycled to purified water. The existing contract, however, states that Palo Alto and Mountain View shall work cooperatively to cover the incremental costs to "encourage the use and recycled water," a clause that may not be applicable decades from now, he said.

The contract also doesn't expressly state how Mountain View would cover the operational costs for the expanded recycled-water system.

Scharff suggested that the extension may be premature.

"My concern is that I haven't heard how this agreement limits options in the future," he said. "If we're going to have a strategic plan, shouldn't we sign this after we have the strategic plan? Shouldn't we understand where the strategic plan is going to go?"

The council voted 8-1, with Councilwoman Liz Kniss dissenting, to refer staff to further review the terms of the proposed extension and make sure it does not restrict Palo Alto's future options. Kniss was in favor of approving the extension, but directed staff to make a few corrections and clarifications.

While Kniss lamented the council's delay in approving the agreement, Mayor Pat Burt argued that careful review is warranted because "the landscape is actually changing."

"The basis for the agreement back in 2005 was based upon recycled water, with really no envisioning of purified water on the horizon and the ramifications of all the things we're going to be studying," said Burt, who chairs the joint committee on recycled water. "What we need to make sure is that the agreements do not restrict us."

Despite their questions and caution, council members were generally in favor of continuing the long-standing partnership with Mountain View. Scharff said he would like to see the city attorney take a closer look at the existing agreements, which City Attorney Molly Stump called "more general and cooperative in tone ... and don't necessarily address at a fine point all these various contingencies."

The council's motion directed staff to make sure that the extension is consistent with the cities' "base agreement" for water allocation and cost sharing. Burt said the council's concern is that the new agreement "doesn't restrict options in some legal way that we haven't identified."

Scharff agreed, saying, "We don't need a sword here. We just need a shield."