In 2013 and 2014, the City of Sacramento tested a new chemical at its main water treatment plant, and an ABC10 investigation found the substances that formed in the city's drinking water system as a result, could cause cancer.

Testing of the chemical called aluminum chlorohydrate, or ACH, almost immediately sent up warning signs that something was seriously wrong, and even though those red flags continued for an entire year, the city didn't stop and didn't warn people about a hazard.

The byproducts Sacramento residents were exposed to are called disinfection byproducts, or DBPs. DBPs are considered likely carcinogens. Studies have also linked the byproducts to low birth weight and even miscarriages.

City officials allowed the testing to continue, despite early warnings the new chemical being tested was creating DBPs at levels that the Environmental Protection Agency says could be unsafe, especially with long term use.

It started as a short-term test of ACH to replace another water treatment chemical called ALUM.

Sacramento's Utility Director, Bill Busath told ABC10 the test was all about one thing, "There was an expectation that we would be able to save quite a bit of money."

More on that claim below.

Coagulants like ACH and ALUM are important. They take river water and bond with impurities after they enter a treatment plant. The chemical weighs down the silt and other impurities, so they fall to the bottom of giant pools. The sediment is then swept away.

Now, Sacramento officials acknowledge there was a serious flaw with their chemical test. In a report the city filed with state regulators, the city admits the test caused DBP numbers to rise to "historically high levels when using (ACH) aluminum chlorohydrate."

To make up for the chemical's lack of effectiveness, the city pumped in more chlorine. But, when chlorine and these organic compounds spend too much time together, the chlorine can turn into disinfection byproducts, or DBPs, in your drinking water.

Busath said, "As soon as the levels got to where we thought that we wouldn't be in compliance, and hence wouldn't be protective of public health, we stopped the trial."

The city did eventually stop testing in May of 2014, but that was after the chemical trials went on for an entire year. During that year, according to internal tests the city was performing, reading after reading went above what the EPA considers safe for long-term exposure to DBPs.

A man who grew up working in the water treatment industry, Bob Bowcock, said what the city did endangered the health of citizens. "This community was basically looked at as a laboratory guinea pig, in that they were exposed to violation level trihalomethanes for up to one year without any proper notification whatsoever," Bowcock said. Trihalomathane is one type of DBP. They're often referred to THMs.

Bowcock managed water treatment plants in southern California for decades. Today he works as an adviser to Erin Brokovich, made famous by the movie about her fight against chemically-tainted water in Hinkley, California.

Pregnant women and unborn babies, Bowcock said, are especially vulnerable to DBPs. "In first trimester pregnancies, there's a significant rise in miscarriages, and in third trimester there's evidence of low birth weight," he said, describing how the DBP-tainted water is even more dangerous when its mists are breathed in while showering or washing dishes.

Sacramento isn't the only city that has had problems with DBPs. Flint, Michigan had a problem earlier this year. But unlike Sacramento, health warnings went out to Flint residents. The elderly, the very young and pregnant women were told they might want to consider filtered or bottled water. Churches even gave away safe water to the poor.

People in Sacramento were never notified about the dangers, never given that choice to opt for bottled water, even though the city had all kinds of data showing they had a serious problem.

The troubling data came fast. A city chemist noticed the problem on the third day of the testing. She wrote in an email to managers, "I'm nervous about the distribution samples." A chart that went along with that email showed DBPs well above EPA limits.

"I think the testing should have stopped immediately," Bowcock said. "I think they should have called the Division of Drinking Water."

Sacramento officials didn't call that state agency or stop the test. Instead, they expanded it, telling the city council they needed enough money allocated, $850,000, to buy a truckload of ACH every week for a year for more testing.

In July of 2013, Busath and other utility officials told the city council in a staff report the State of California "has now mandated that the trial be extended from three weeks to a full year."

That sounds like a good reason if the state mandated it, but it's also not true.

The California Environmental Protection Agency Division of Drinking Water told ABC10 that they never told the city it had to do a year-long trial of ACH or any other chemical.

In fact, CalEPA said it was the other way around. "The city approached us," said Division of Drinking Water Deputy Director Bruce Burton. " It was the city who asked us if they could use that chemical at their water treatment plant."

When we asked the city about that discrepancy with the state, we got an admission from Busath with the utilities department. "The word mandate used in the council report was probably a poor choice of words," he told ABC10.

"Every corner you turn, on this particular project, it's red flag, red flag, red flag," Bowcock said. "It's like peeling back an onion. There is just another layer. The closer you get to the center, the stronger the smell.

So how much was the public exposed to DBP's in some neighborhoods?

ABC10 obtained data showing dozens of readings in excess of the EPA standard of 80 parts-per-billion during the year-long trial. In the Westlake neighborhood, near Sleep Train Arena, during a two-month period between August and October 2013, 11 of 13 readings were above EPA limits. Then in March of 2014, readings were way up across the city. Some people were drinking water with DBP levels above 130 parts-per-billion.

ABC10 asked Busath, the utilities director, about those numbers and why he allowed the testing to continue. He always gave the same answer. "Because we had the anticipation of saving money with using ACH," said Busath.

And when asked why his department didn't share all that data, all those alarming numbers with the public and with regulators, Busath told ABC10, "As long as we were in compliance, we don't need to contact them." He said what really matters, is that the city DBP numbers were within safe range for quarterly EPA mandated tests. "All this trial, we were within the guidelines for the disinfectant byproduct levels, which is a one-year running average," he said.

Busath is right, by law the city did not have to report its unusually high DBP levels unless its annual average of those quarterly samples was higher than the safe drinking water standard set by the EPA.

But, ABC10 found evidence that for one of those tests in January 2014, the Sacramento River Plant where the chemical trials were being performed was turned off, and the city took water from another plant on the American River.

And for another one of those quarterly tests, emails reveal the city intentionally switched water sources from the city to the county, days before an EPA test.

This was the subject of one email; "Request for emergency water service from Sacramento County Water Agency to the City of Sacramento."

What was the emergency? If the city didn't get water from another source, it was certain to exceed yearly standards for its disinfection byproducts.

Erin Brokovich had strong words for the department concerning that staff report and the alleged manipulation of water sources to control test results. She told ABC10, "Its deceptive, its mismanagement. You lied. You lied."

If the annual averages exceeded 80 parts-per-billion, by law, the city would have had to tell the public about the problem just like utilities officials did in Flint, Michigan.

When pressed about why his department continued testing because of believed cost savings, even in the face of all of that troubling data, Busath said, "Of course, our main goal, is that we have to stay in compliance."

Busath said everything that the city did was legal, including switching out water sources.

Brokovich had some advice for Sacramento residents. "I would light up the city council, make sure that there are repercussions, and every assurance it doesn't happen again and that you are delivering safe drinking water to every person in your district," she said.

In the end, the alleged money savings Utilities Director Busath was talking about appears to have been overstated or completely wrong. The staff members said in a report to council that they expected to save up to a million dollars using ACH. But, ABC10 found the department used bad data. The actual numbers show that not only was the original chemical safer, it appears it was also cheaper.

Read the Consumer Confidence Report (CCR) here.

Read a letter from the Sacramento Water Quality Superintendent to a California Department of Public Health associate sanitary engineer.


WATCH MORE: Sacramento's drinking water secret