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EPA has completed the fifth five-year review report of the remedial actions performed under the Superfund program for the site. The purpose of the five-year review is to evaluate the implementation and performance of a remedy to determine if it is or will be protective of human health and the environment. The report is available at the public information repositories and online:

The five-year review addresses all 12 of the site’s operable units (OUs):

Former mining operations contributed to metals contamination in surface water, groundwater, soil and sediments. The Yak Tunnel Water Treatment Plant in OU1 primarily treats waters draining from the Yak Tunnel and OU4.

Extensive piles of mine tailing, slag and waste rock are present on the site and remedial efforts at OUs 2 through 11 have been designed to control these source areas. Water quality data is collected on an ongoing basis as part of the OU12 remedy, selected in 2009. The OU12 and OU6 remedies are in the remedial action phase with expected completion dates in 2020.

Remedies for OUs 1, 2, 3, 4, 5, 7, 8, 9,10 and 11 have been completed and are being monitored and maintained as required. These remedies are generally performing as intended. All of these OUs except OU11 have been partially deleted from the NPL.

Remedial actions in OU6 and 12, once fully implemented, are expected to perform as intended. OU11 entered the O&M phase on May 1, 2017 and needs institutional controls before the OU can be partially deleted from the NPL.

Go to What Is the Current Site Status? for a detailed description of each operable unit.

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