The city of Mountain View is planning to rapidly expand its recycled water use in the coming years, with ambitious plans to build an expanded network of pipes that can deliver to water to areas slated for major new development.

Recycled water currently makes up just a small fraction of the city's daily water use, at around 460,000 gallons per day, or 4%, of the Mountain View's total water use. But with persistent statewide droughts and constraints on imported water, city officials are turning to treated wastewater as a sustainable alternative.

The top option, according to city staff, is to expand recycled water infrastructure in North Bayshore, under a plan that would crank up recycled water demand to more than 1.4 million gallons per day. Other options include taking it a step farther and extending the system into East Whisman -- a long-range plan that would take decades to complete and cost upward of $40 million.

The Mountain View City Council is scheduled to weigh in on at the options at its Tuesday, March 22, meeting.

Mountain View send its wastewater to Palo Alto's Regional Water Quality Control plant and has the rights to 3 million gallons of treated water per day, under a deal that has recently been extended to 2060. That treated water then comes back through a network of purple pipes that circulates to locations throughout North Bayshore, but does not cross U.S. Highway 101 into the rest of the city.

The city is using only a fraction of its allocation, in part because of the quality of the water itself. The high salinity levels of the treated water means it cannot be used to irrigate certain landscaping and plants -- most notably redwood trees -- and can lead to erosion in buildings. A plan to upgrade Palo Alto's treatment facility is in the works, allowing the facility to produce "highly treated" water that has far more uses.

Under "Alternative 1," which city officials are recommending to the council, Mountain View would extend pipelines through North Bayshore along streets including Shoreline Boulevard, Amphitheatre Parkway, Shorebird Way and Space Park Way. The plan would increase the range of recycled water to include more commercial customers in the area, notably Google, and prepare for future water demand caused by major residential and commercial growth planned for the area.

The other alternatives look at different ways the city can take on the expensive and difficult task of getting water south of Highway 101, specifically into East Whisman -- another area slated for heavy development. The pipelines could cut through NASA Ames property or could extend south on Shoreline Boulevard and east along either Middlefield Road or Central Expressway. Costs for any of the three options range from $41.4 million to $52.2 million.

The city is also facing some tricky challenges related to the Regional Water Quality Control facility improvements in Palo Alto. Cost estimates have exploded from $22.3 million to $51.4 million since 2019, and city officials fear the Santa Clara Valley Water District is looking to pay for the upgrades using money slated for other water improvements in the North County.

Mountain View residents, like those in other North County cities, pay taxes into the State Water Project that helps finance a massive system of reservoirs, aqueducts and pumping plants that circulate water throughout the state. But only about 10% of Mountain View's water use comes from that system, leaving most residents with the full cost but none of the benefits. In 2017, Valley Water's board of directors agreed to return the funds -- roughly $8.5 million spanning from 2018 to 2024 -- by way of a grant program.

Last August, Valley Water voted to allow those funds to be rerouted into paying for the recycled water facility upgrades, and that $6 million of the $8.5 million is expected to go towards those improvements. Mountain View officials are protesting the decision, saying it was never the intent to pay for the upgrades using its own, separate grant program that could be used for the city's own conservation and recycled water efforts.

Expanding the recycled water network in North Bayshore is expected to cost $27.4 million and take nine years to complete, and the city has already laid the groundwork for businesses to take advantage of the purple pipes. Mountain View passed an ordinance requiring all new commercial buildings larger than 25,000 square feet to have dual plumbing to allow the use of recycled water when it becomes available, specifically for uses like flushing toilets.