The first sign of trouble bubbled up from gopher holes a stone’s throw from Stan Ledgerwood’s front door. The salt water left an oily sheen on the soil and a swath of dead grass in the yard.

A new production boom never materialized for Southcreek in this slice of Garvin County, and the family didn’t hear much from the oil company.

But then a corroded valve malfunctioned underground, injecting brine into the soil, according to a report by a Southcreek contractor.

Some orphan well cleanup in Oklahoma is funded by a voluntary 0.1% fee paid by industry on the sale of oil and natural gas. The Oklahoma Energy Resources Board spent $156 million of the funds collected from this fee over the past three decades. The state has an additional orphan well fund with several million dollars in it.

But Oklahoma has more than 260,000 unplugged wells — behind only Texas — according to data from energy industry software firm Enverus. To plug and clean up the state’s wells could cost approximately $7.3 billion, according to an analysis of state records. Oklahoma has just $45 million in bonds.