Corpus Christi may be known as “the Sparkling City by the Sea,” but the city’s shine has been significantly dulled lately, thanks to a string of water safety problems that have left residents without clean water for an extended period of time on four separate occasions within the last 18 months. The first three incidents involved the city warning residents to boil their water before using it, but the fourth incident, which happened last week, was perhaps the most troubling.

Late last Wednesday night, a city-wide notice was issued alerting residents to stop using tap water for anything at all, including for drinking, showering, or brushing teeth. The city also told residents that there was essentially nothing they could do to make the water any safer, including boiling it, “freezing, filtering, adding chlorine or other disinfectants, or letting the water stand,” according to a city news release. Details of the reason for the ban were not immediately made clear, but it later emerged that Indulin AA-86, a chemical asphalt emulsifier, had leaked from a private industrial site into the water supply, due to what is believed to have been a “backflow” problem.

The ban lasted for nearly four days. In the meantime, the city was nearly paralyzed. Schools and some businesses were forced to close down, and residents seeking clean, bottled water were confronted with absurd, winding lines with up to three-hour wait times at local stores. The crisis made national headlines, and as of Tuesday, twelve people had reported symptoms consistent with Indulin exposure, according to the Corpus Christi Caller-Times, although testing has yet to confirm whether their symptoms are the result of the water contamination. The Texas Attorney General’s Office, the Texas Commission on Environmental Quality, and the federal Environmental Protection Agency are jointly investigating to determine what exactly went wrong in Corpus Christi.

Corpus Christians are, by now, all too familiar with the feeling of being left without clean water in their own city. Corpus Christi’s water problems go back to July 2015, when the city issued a boil water notice after discovering E. coli contamination in water samples. The notice lasted two days. Later that year, in September, the city again issued a boil water notice, this time due to low levels of chlorine. Most of the city remained under the boil warning for ten days. In May this year, the city issued its third water boil notice in ten months. This one was the longest. It stretched from May 6, when water initially tested positive for non-harmful bacteria, until May 25, when testing revealed the water was finally free of contaminants.

The third water boil notice left Corpus Christians particularly concerned. One woman circulated a petition calling on Mayor Nelda Martinez to resign (she didn’t), and the crisis ultimately claimed the job of city manager Ron Olson, who stepped down while the notice was still in effect, in part, according to the Caller-Times, because he felt he should be held accountable for the city’s long-running water problems. Residents flooded the social media pages of celebrity environmentalist Erin Brockovich, begging for her help, until her partner paid a visit to the city and met with city officials. “At the end of the day, every one of us deserves clean drinking water,” Brockovich told Corpus Christi’s NBC-affiliated KRIS-6 in May.

The city took immediate steps to address the problems that led to the water boil notices, embarking on a comprehensive “source-to-tap” plan of action to improve and stabilize the city’s water quality, focusing on three main components: the source of the water, water treatment, and distribution. A good chunk of that plan was completed by November, when interim director of water and utilities Dan Grimsbo presented a project update before the city council, claiming that the completed projects had already resulted in “significant improvements in the stability of water quality.”

But less than a month after that presentation, the tap water ban hit Corpus Christi. Now, residents seem less confident than ever in their city’s ability to provide them clean, safe water. Perhaps nowhere were their frustrations more evident than at a news briefing held by the city on Thursday, where, according to the Associated Press, a group of residents started angrily chanting, “What do we want? Clean water! When do we want it? Now!”

Frustrations also boiled over inside grocery stores. During the ban, Corpus Christians scrambled to purchase safe water, often finding empty shelves instead. According to the Caller-Times, water was sold out at one H-E-B as early as 6:30 a.m. on the first day of the tap water ban, and hundreds of people were forced to wait in line for hours until the next shipment of water arrived. Compounding the issue was the extra money people had to shell out on water at a time when many are particularly strapped for cash due to Christmas shopping.

Water outages like the one at H-E-B were consistent at grocery stores, gas stations, and corner spots across the city. Residents were also critical of the effectiveness of the city’s alert system. According the Caller-Times, city officials were able to notify 119,119 people that a tap water ban was in place, which is less than half of the city’s total population.

City officials worked to address those concerns. “The city set up five free water distribution points and gave out bottled water,” city spokeswoman Kim Womack told Texas Monthly in an email. “Donations came from all over the country along with supplies the city secured with the help of State of Texas Emergency Management. Local stores were also very helpful in providing water residents could purchase. The city used reverse 911, reverse alert, and local media. Our media partners were amazing and did live cut-ins during national programming, provided scrolls, and many live interviews.”

Womack declined to name the responsible party, citing an ongoing investigation, but the Caller-Times has reported that the city believes the third-party to be Ergon Asphalt and Emulsions. Energy giant Valero said in a statement last week that the contamination was caused by “localized backflow issue from third party operations in the area of Valero’s asphalt terminal.” Both Valero and Ergon are already facing seven lawsuits on behalf of Corpus Christi businesses who were forced to shut down during the ban, and hundreds of similar suits could soon be filed, according to the San Antonio Express-News.

In her email, Womack emphasized the water boil incidents and the tap water ban were different, although she did not explain how. When asked how the city could reassure its residents that they won’t face more water crises in the future, she said that in the next few months, the city will be “providing recommendations to our elected officials regarding the industrial district and amendments to back-flow prevention (both residential and commercial) along with the other already in motion improvements to the water system.”

It’s important to note that Corpus Christi is not the only city to have problems ensuring its residents have access to safe water. Water boil orders are not tracked nationally, but an analysis by the Huffington Post in May found that from February 22 to March 22, there were 142 incidents in 27 different states that involved residents in a city or town—including eleven in Texas—being told to boil their water for more than 24 hours.

Perhaps the most high-profile water contamination crisis in the history of the U.S. is currently ongoing in Flint, Michigan, where cost-cutting measures led drinking water to become contaminated with unsafe levels of lead, forcing the state’s governor to declare a state of emergency. On Tuesday, several Flint officials were charged with felonies for their alleged roles in the lead contamination.