The US Nuclear Regulatory Commission (NRC) has issued a Confirmatory Order to Homestake Mining Co of California outlining actions to be taken as part of an ongoing groundwater cleanup program at the site of a former uranium mill in New Mexico.
The mill, at a site near Grants, processed uranium for several local mines between 1958 and 1990. Tailings from milling operations were placed in two piles. In 1975 it was discovered that seepage from the tailings piles had contaminated groundwater, and a groundwater protection plan was implemented from 1977. The mill itself was decommissioned and demolished between 1993 and 1995.
The site, which is also under the oversight of the US Environmental Protection Agency (EPA) through the Superfund program, is undergoing a major groundwater corrective action plan under an NRC licence. Site closure is estimated for 2022.
The Confirmatory Order issued by the NRC finalises and makes legally binding commitments made by Homestake to address apparent violations of the NRC-approved corrective action progam. The violations, discovered by the NRC during records inspections between October 2014 and May 2016, include the discharge of water that exceeded site standards; the discharge of water containing byproduct material to unauthorised locations; failure to obtain liquid effluent samples and report the results; and the injection of water using a method inconsistent with the approved program.
The NRC noted that Homestake took immediate corrective actions to comply with the regulator's requirements. "The NRC has no immediate public health and safety concerns, because the apparent violations did not result in the public being exposed to contaminated groundwater," it said yesterday.
Homestake has agreed, through a mediated dispute resolution process, to further commitments to bring it into compliance with NRC requirements. A root cause protocol, which will be submitted for review to the NRC and an "independent third party", will be used to analyse the reasons for the violations and identify additional further corrective actions. The company will also assess all its activities, including a review of its safety culture, to determine their compliance with NRC requirements. Homestake will submit a revised groundwater program to the NRC by the end of 2018.
According to the EPA, the large tailings impoundment at the Homestake site covers an area of about 200 acres (81 hectares) and is about 85-100 feet (26-30 metres) high. It contains an estimated 21 million tonnes of mill tailings. The small tailings impoundment covers an area of about 40 acres and is 20-25 feet high, containing about 1.2 million tonnes of tailings. Seepage from the two tailings impoundments has resulted in the contamination of the underlying groundwater aquifers. The current remedial program consists of a groundwater collection/injection system, tailings collection wells within the tailings impoundment, a tailings impoundment toe drain, a reverse osmosis treatment plant, and three evaporation ponds.
Homestake Mining Company is a wholly owned subsidiary of the Canada-based Barrick Gold Corporation following a merger in 2001.
Researched and written
by World Nuclear News