Depressurization, the other major contributor to pollution, occurs when firefighting efforts remove enormous amounts of water from the system in a short period. “A water line connecting to a house can typically produce about 9 gallons per minute,” Whelton says. “Firefighters can extract 500 gallons or up to 1,500 gallons of water per minute. So if you were to run five or six pump trucks from one water line, you would be looking at thousands of gallons of water being pulled from the water system in a very short period of time.”
When that happens, water pressure plummets and the system becomes vulnerable to the entry of bacteria or chemicals from the surrounding environment. Typically, the high water pressure within the system prevents any external contaminants, such as soil or groundwater, from reaching the interior of the system components.
Structural damage from fires can also cause pressure losses, Whelton says. In the case of large-scale fires like the Palisades or Eaton fires, large volumes of water can be seen pouring, uncontrollably, out of the system due to burst pipes and other parts of the system. When there is damage, smoke and debris can be sucked into the water system, while damaged sewer lines can leak into drinking water pipes running nearby. “When the water system utility starts trying to repressurize, they start pushing that contaminated water through the infrastructure again,” Whelton says.
During the Marshall Fire in Louisville, Colorado, in 2021, which burned more than 1,000 homes, city officials advised residents to use tap water only for flushing until extensive testing confirmed safety. With more than 12,000 structures burning in Los Angeles as of Monday morning, the potential for widespread contamination is significant, Kearns warns.
The next few days and weeks will be crucial. Once water experts assess the damage, they will determine if the system can be cleaned or if infrastructure repairs are necessary. If enough has burned, workers will have to replace pumps, pipes and even tanks. For parts of Los Angeles County served by LADWP, McCurry estimates this recovery could take anywhere from a few days to weeks.
Altadena and the surrounding regions, however, are served by several smaller water providers, such as Lincoln Avenue Water Company, Las Flores Water Company, Rubio Canon Land and Water Associationand Kinneloa Irrigation District—All of which have issued Do Not Drink advisories. “In the case of a large water system like LADWP, you’ll probably see things resume a little quicker,” Kearns says. “Smaller water suppliers, who may sometimes only have a couple of employees and not have budgets for these types of events, may have some difficulties.” Santa Cruz experienced similar challenges during the CZU Lightning Complex fire in 2020, and water service took months to stabilize. McCurry warns that some regions may need years to build from scratch or overhaul large systems that have burned out.
It’s vital that residents stay informed about recovery efforts, because alert systems can be complicated and many residents may not even receive them, Kearns says. People should “proactively look for any boil water or Do Not Drink alerts from your water provider, your city, your county,” he advises. “Share them with your neighbors and make sure that anyone who has languages other than English as their first language receives those alerts and understands what’s happening.”
Some places, such as Louisville in Colorado and Maui in Hawaii, published publicly accessible maps that tracked water quality on each piece of land, helping to keep residents informed in the months and years that followed.
Before lifting warnings, the state of California legally requires water suppliers to monitor benzene. However, Whelton warns that benzene is not the only chemical of concern and that the list of possible contaminants is long. Both government and third-party testing services do not always take into account all possible exposures. “Some of those chemicals may linger longer than water suppliers expect,” McCurry echoes. He still recommends staying alert. Activated carbon filters can help remove some organic contaminants, but may not completely eliminate risks.
“Safe water can restored after a fire,” says Whelton. “Communities that recover quickly and are stronger are those that work together and support each other.”