Using data from public records requests and independent researchers, the AP examined 43 mining sites under federal oversight, some containing dozens or even hundreds of individual mines.
The records show that at average flows, more than 50 million gallons (189 million liters) of contaminated wastewater streams daily from the sites.
In many cases, it runs untreated into nearby groundwater, rivers and ponds — a roughly 20-million-gallon (76-million-liter) daily dose of pollution that could fill more than 2,000 tanker trucks.
The remainder of the waste is captured or treated in a costly effort that will need to carry on indefinitely, often with little hope for reimbursement.
The volumes vastly exceed the release from Colorado’s Gold King Mine disaster in 2015, when a U.S. Environmental Protection Agency cleanup crew inadvertently triggered the release of 3 million gallons of mustard-colored mine sludge, fouling rivers in three states.
Some sites feature massive piles or impoundments of mine waste known as tailings.
A tailings dam collapse in Brazil last month killed at least 169 people and left 140 missing.
But even short of a calamitous accident, many mines pose the chronic problem of relentless pollution.
Tainted wells In mountains outside the Montana capital of Helena, about 30 households can’t drink their tap water because groundwater was polluted by about 150 abandoned gold, lead and copper mines that operated from the 1870s until 1953.
Most are controlled by the Bureau of Land Management, which under Trump is seeking to consolidate mine cleanups with another program and cut their combined 2019 spending from $35 million to $13 million.