When Tammy Boarman first contacted oil regulators, she was hopeful state officials would find the source of the pollution and clean it up. For the next two years, the state repeatedly tested the Boarmans’ water for contaminants and found salt concentrations that made the water undrinkable and, at one point, toxic metals at levels high enough to endanger human health — strong signs of oil field wastewater pollution, according to agency testing.

But regulators repeatedly delayed or failed to conduct other tests recommended by the agency’s own employees to locate the pollution source, according to internal agency documents obtained by The Frontier and ProPublica through public records requests.