Long before a pipeline leaked volatile gas into a Firestone home that exploded, Colorado’s overseers of the oil and gas industry were warned such pipelines posed major risks.

For years, they’ve known leaking underground pipes carrying oil, gas and processing waste regularly contaminate soil and water and potentially threaten thousands of people around the state, records show.

Now, the home explosion that killed Mark Martinez and Joey Irwin and left Erin Martinez traumatically burned has Gov. John Hickenlooper and other officials questioning whether, given the magnitude of the issue, enough safeguards are in place. A review by The Denver Post shows regulators for decades relied only on self-reporting by companies or complaints to identify failed pipelines even though pipelines are the leading cause of oil and gas leaks to the environment. It wasn’t until last year that the state began any program to monitor the underground pipes connecting wells to tanks and other equipment in the field.

Just three state officials are tasked with ensuring the integrity and safety of thousands of miles of pipelines in Colorado connected to about 53,000 active wells and associated with an additional 36,500 inactive wells. The Colorado Oil and Gas Conservation Commission, which regulates the industry, didn’t deploy those officials until 2016, leaving the vast majority of oil and gas pipelines still uninspected. Regulators say they don’t know where all the pipelines are located. And they leave it up to local jurisdictions to decide whether developers can build homes over them.

A proper pressure test on the supposedly abandoned pipeline in Firestone would have identified a cut in the pipe that gushed gas just 6 feet from the southeast corner of the house that exploded on April 17, state officials acknowledged Thursday.

“We’re hopeful that this will be a unique situation, that this will be a one-time occurrence,” Hickenlooper recently said. “But, until we can be absolutely sure of that, we’re going to go above and beyond all requirements for safety.”

He added: “How could we have anticipated this?”

But problems with oil and gas industry pipelines have not only been anticipated, they’ve been documented repeatedly in state records, industry spill reports, academic studies and even a crucial 2014 report state regulators prepared for the legislature.

Broken underground pipelines carrying oil or gas from wells to tanks and to other equipment in the field are the leading cause of hazardous oil and gas industry leaks, reports show.

The 2014 risk report prepared by COGCC for lawmakers identified crumbling and deteriorating pipelines as the source of half of the equipment failures that cause industry spills in Colorado. Yet that report found the state did not have a “formal program to monitor ongoing compliance” regarding integrity testing for pipelines in the state.

It took at least a year for the state to finalize how to respond. In 2016, COGCC finally deployed three people — an inspector, an engineer and a supervisor — to tackle the problem.

Since then, the new inspector has conducted about 400 pipeline inspections, leaving most pipelines in Colorado with no on-site review by any state official.

The new state pipeline engineer has audited 24 oil and gas operators on whether they maintain records to show they are conducting required annual pipeline pressure tests. The 2016 audits reviewed industry record keeping for only about 10 percent of Colorado flowlines — associated with about 2,760 wells — state statistics show. No operators were cited with a violation as a result of the audits.

Companies pass the audit if they can show they have conducted pressure tests on a third of their pipelines, which the company selects for review. The state has concentrated the audits on major operators, leaving much of the state where smaller operators proliferate with no current state oversight of pipelines. The engineer also reviewed reported pipeline failures and found that nearly half were caused by corrosion.

“This was my scheme to get the best effort possible,” said Stuart Ellsworth, engineering manager for the Colorado Oil and Gas Conservation Commission. “I believed this would be getting us a random-sample kind of scenario and a risk-based model that would be a forward focus that would get the state a good outcome.”

He said state officials now are reviewing the pipeline rules to see if a more robust response is warranted in light of the Firestone explosion that killed two men, one of whom was a licensed plumber.

Among the issues under review are whether they need to produce a comprehensive map of where pipelines are and make it available for public review, and whether new pressure testing should be required for smaller pipelines. State officials also are considering increasing inspections of pipelines. Operators also may end up having to install new monitoring equipment on pipelines, something only a handful of operators have done. Legislators are pushing a bill that would require the COGCC to create a statewide pipeline map that would be posted online for the public.

The April 17 explosion was caused by a cut flowline attached to an active Anadarko Petroleum well about 170 feet from the home, state and local investigators said. The men died while replacing the home’s water heater. Investigators say an odorless mix of propane and methane seeped into the house through French drains and a sump pump and ignited. Commercial gas had been turned off inside the home the day before the explosion.

The COGCC notified Anadarko in an August letter that the agency had audited the company’s pipeline pressure testing records. As a result of the audit, the agency recommended the company use GPS to accurately determine the location of its pipelines. Anadarko also should ensure that all pipelines it had acquired from another operator were registered properly with the state, the audit recommended. The audit also said the company should start documenting the cause of pipeline leaks when it reported those leaks to the COGCC and explain how such leaks would be prevented in the future.

A pressure test of the flowline that leaked gas into the Firestone home would have identified the hazard that turned fatal, Ellsworth said. That line once was connected to a nearby tank, which was moved before the Oak Meadows subdivision was built. The pipeline should have been capped at the well but instead was left connected to the well, investigators said.

State Rep. Jonathan Singer, a Democrat from Longmont who pushed for the 2014 risk-based assessment report, said that report has taken on renewed urgency after the fatal explosion. He said he and other legislators may push for a new inspection regimen for oil and gas pipelines or new restrictions on oil and gas operations.

“When you have over 50,000 active wells in the state and only a handful of inspectors, you have to use the best type of engineering available to make sure people are kept safe,” Singer said. “In 2013, that was a very abstract conversation, but just a couple of weeks ago, it got very real.”

After the explosion in Firestone, the state ordered operators to inspect and test oil and gas flowlines within 1,000 feet of occupied buildings within 30 days. Lines not in use must be properly marked and capped, and any abandoned lines must be cut 3 feet below the surface and sealed.

Records show that in 2016, COGCC began allowing operators to skip pressure testing if they installed monitoring equipment on their pipelines. The monitoring equipment is supposed to identify any pressure anomalies and immediately shut down a pipeline if anomalies are discovered. Since then, only a handful of operators have filed records showing they have installed such monitoring equipment, state regulatory records show.

In one instance, state regulators and officials with BP America Production Co. debated whether the company’s pipeline-monitoring program was adequate for a variance from pressure testing, records show. BP wanted to stop pressure testing 542 natural gas flowlines and 505 miles of processed water waste flowlines in La Plata and Archuleta counties, records show. The regulators pushed back, noting that BP’s monitoring program in 2015 failed to identify two leaks of production waste from corroded pipelines.

“No continuous pressure monitoring program is guaranteed to detect all leaks,” BP said in a letter, which stressed that additional company safeguards had been developed.

COGCC granted the variance.

The 2014 report was prepared for lawmakers, who passed legislation in 2013 requiring a risk-based assessment of how the state inspects oil and gas operations. The commission submitted the report in February 2014 to three legislative committees, one in charge of writing the state budget and two others overseeing natural resources.

To prepare the report, the commission hired a Maryland-based environmental consulting firm, S.S. Papadopulos and Associates Inc., which reviewed 1,638 spill reports filed with the commission from 2010 to mid-2013. The consultants found that nearly 80 percent of spills occurred during production and that nearly 70 percent of those production spills were caused by equipment failures, 50 percent of which were due to pipelines.

“Those leaks are different than these leaks,” Hickenlooper told reporters in his office last week when asked why state officials’ extensive knowledge of pipeline leaking had not been sufficient to prevent a tragedy such as the Firestone blast.

“To me, this feels almost like a perfect storm,” Hickenlooper said. “Somehow, that line got severed. I’m not sure how it got severed. I’m not sure whether it was done by excavation for housing, or whether it was done by oil and gas.”

“When there is a leak from a flowline that gets into groundwater, we require complete remediation,” he said. “That is part of the reason why, with modern wells, we try to keep track of those flowlines as much as possible.”

But Joseph Ryan, a University of Colorado environmental engineer, whose studies have identified oil and gas pipelines as susceptible to major spills, said the state needs to reconsider its current approach. State officials should consider requiring better public mapping of flowlines and also restricting how closely flowlines can be located to housing, Ryan said.

“If we view the flowlines as hazards — and, after what happened a couple of weeks ago, I cannot see how we would not see it that way — having public records of where these flowlines are located would be important,” Ryan said.

He added: “How many of these flowlines are near homes?”

That’s a question now being asked east of Berthoud, where Extraction Oil and Gas in the past week began fracking two new wells drilled less than 500 feet from a house in a wetlands area around a reservoir. Under state rules, the buffer of 500 feet can be waived if landowners grant permission.

While red trucks lined up with the sand and water for fracking, neighbors fumed about the dust and truck traffic that they say is disturbing their lives. Oil and gas industry officials approached other landowners in the area asking whether they would allow wells on their property for payments of around $3,000 a month, said resident Stephanie Nilson, who raises draft horses just north of the pastures where Extraction crews were working at full force.

“That money could have paid my whole mortgage, but I am more into my horses,” Nilson said. “We didn’t even debate it. We don’t want them around here. Look what happened in Firestone.”