California has made significant progress helping small communities address problems of contaminated drinking water, but the costs of bringing safe tap water to hundreds of communities over the next five years will run more than $11.5 billion, according to a new state estimate.

In a newly released report, the staff of the State Water Resources Control Board estimated that at the start of this year approximately 913,000 Californians depended on public water systems that are failing to comply with drinking water regulations, while an additional 1.5 million people depended on water systems that are determined to be “at-risk.”

Officials carried out the assessment nearly five years after the state established the Safe and Affordable Funding for Equity and Resilience, or SAFER, drinking water program. They said in the report that under the program, the state water board has since 2019 given more than $831 million in grants for drinking water projects in disadvantaged communities, and that about 250 failing water systems serving more than 2 million people have come into compliance with drinking water standards.

“What our analysis has shown time and again is that the common denominator is size,” said Joaquin Esquivel, chair of the state water board. “Small systems struggle, especially in communities that have experienced discrimination and disinvestment, and their challenges will be amplified as weather grows more extreme, new contaminants emerge and costs increase.”

California declared access to clean, safe and affordable water a human right in 2012, but the state has faced significant challenges in developing policies and securing adequate funding to bring solutions for communities where people live with contaminated tap water.

In small rural communities across the state, the water pumped from wells contains harmful levels of contaminants including naturally occurring arsenic, bacteria from sewage leaks, nitrate from animal manure, fertilizers or other sources, and carcinogenic chemicals.

Not all systems that are deemed to be failing deliver water that is contaminated, but many of them have at least one contaminant at levels that violate safe drinking water standards.

According to state data, about 56% of the 385 failing water systems supply disadvantaged communities, and 67% of them supply majority communities of color.

“All of our current failing water systems are on track to come off the failing list,” said Kristyn Abhold, senior environmental scientist for the state water board. “They are working on long-term solutions, and our staff and funding resources are being targeted to the ones that are in most need.”

State water regulators have found that the vast majority of the failing water systems serve a small number of residents, while 98% of the state’s population receives water from sources and suppliers that meet drinking water standards.

For a water system to come into compliance with regulations, it takes not only funding but also planning, engineering work and permits, Abhold said.

State officials have assessed other communities that are at risk by analyzing the potential for water quality violations or water shortages, among other factors.

The number of people affected has fluctuated in recent months as some water systems have come off the list and others have been added. The state’s latest estimates show that 738,000 people currently receive water from failing systems, while more than 1.8 million people depend on 548 systems with drinking water supplies determined to be at risk.

The state’s report includes estimated costs for infrastructure solutions such as installing treatment systems, drilling a new well, or consolidating by connecting one water system to another.

The estimated costs of solutions in the latest report were substantially higher than previous state estimates. In a 2021 report, the state water board included a range of estimated costs up to $9.1 billion. Officials said they used new methods and improved data this time, including more water systems and risks in their analysis.

According to the report, the estimated costs of long-term solutions for failing and at-risk public water systems total $6.6 billion over five years, while the costs of solutions for “high-risk” small water systems and domestic wells total $4.9 billion.

Those combined costs, totaling more than $11.5 billion, would be significantly higher if loan repayment costs and operations and maintenance costs are included, the report said, pushing the total estimated cost of “achieving the human right to water” to $15.9 billion.

Officials projected that $2 billion in state grant funds will be available over five years, as well as $1.5 billion in state loans, leaving a substantial gap in available funding. Officials said a large portion of the money to address the problems may need to come from “local cost share” funds collected through rates, fees and taxes.

The report’s higher cost estimates were released amid discussions about budget cuts in Sacramento.

Citing recent cuts, more than 180 organizations, including environmental groups and other organizations, wrote to state leaders urging them to approve placing a $10 billion bond on the November ballot to provide “direct and meaningful investments in the California communities and natural resources most impacted by climate change.”

As part of that ballot measure, they called for including $1 billion for drinking water and wastewater infrastructure for communities and tribes.

Leaders of the groups wrote that “recent and proposed cuts to funding for such programs have prompted consensus that additional bond funding is necessary to ensure priority programs continue beyond this year.”

Jennifer Clary, California director for the group Clean Water Action, said: ”drinking water infrastructure isn’t a luxury item. Without these projects, thousands of Californians will continue to lack access to safe and clean drinking water.”

Clean water advocates have also voiced concerns as state officials have reviewed the costs of a program that provides household tanks and hauls water by truck to thousands of low-income families whose wells have gone dry.

More than 3,000 domestic wells have run dry throughout California since 2020, according to reports submitted to the state. Those with dry wells have started relying on water delivered by tanker trucks to fill their tanks, while also receiving bottled water.

Leaders of the nonprofit group Self-Help Enterprises, which manages the water-hauling effort, recently urged Gov. Gavin Newsom and other state leaders to reject proposals that would take away critical funding for the program. They wrote in a June 11 letter that taking away $17.5 million would “cut off access to water for more than 20,000 people who are still awaiting a permanent solution.”

The letter, which was first reported by the news site SJV Water, was also signed by leaders of other organizations, including the Community Water Center and Union of Concerned Scientists.

“The reversions of these funds will cut off access to water for more than 20,000 people who are still awaiting a permanent solution,” the groups said. “Cutting funding for such a crucial program would have devastating effects on rural and disadvantaged communities by immediately cutting them off from their sole source of water supply, and doing so with no warning.”

Leaders of some groups said later that the funding for the program has been restored.