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Red And Bonita Portal Shed Replacement

 
Site Contact:
Craig Myers
OSC

(myers.craig@epa.gov)

Site Location:
Gladstone, CO 81433
response.epa.gov/RedBonitaPortalShed

The Red and Bonita Mine is located within the Cement Creek watershed, a component of the upper Animas River watershed in San Juan County, Colorado. These watersheds within the volcanic terrain of the San Juan Mountains were the focus of both large- and small-scale mining operations that flourished between 1871 and 1991. Historic mapping of the Red and Bonita Mine indicates that mining operations began prior to 1899 and lasted for only a short
period. The Red and Bonita is one of several mines in the Cement Creek basin that have adits discharging acid mine drainage (AMD).

In the fall of 2011, the EPA removed a blockage in the Red and Bonita Mine opening and constructed a temporary portal for accessing the mine. The mine adit is approximately five feet wide by seven feet high and extends underground for several hundred feet in multiple directions. Investigations of the mine allowed access to approximately 2,000 feet of workings. Based on historic information and the calculated waste dump volumes, it is
estimated that there are 3,500 feet of underground workings and that the adit does not connect to other mines. In addition, there are no other mapped surface openings to the mine, and none were found during Site investigations in September 2014 or previously.

In 2012 and 2013, the EPA and Division of Reclamation and Mine Safety (DRMS) conducted entries into the mine to determine, if possible, where the mine water flow was originating and what options existed for controlling the flow. A preliminary assessment of the rock and adit conditions indicated that it might be feasible to install a concrete bulkhead. The conditions underground and associated discharge from the mine required that the
operations in 2012 be postponed and re-attempted the following year.

In August 2013, a second entry operation was performed. The results of the investigation revealed that the two primary sources of water include the main cross-cut and flow from a drift at 275 feet. Suitable rock for potential bulkhead construction was identified within the mine at approximately 265 feet in from the portal, which is down stream of the two sources of flow. The source of water flow within the mine could not be isolated, and no connections to other mine workings were identified. Solids precipitate from the mine water collected during the operations in 2011 and 2012 was determined not to exhibit a hazardous waste characteristic (URS Field Activities Report, December 2012).

Following additional investigation and design in 2014, a concrete bulkhead with a flow control valve was constructed in 2015. Closing the flow control valve in the bulkhead floods the interior workings. Conceptually this may reduce the generation of AMD by reducing oxygen contact with pyrite containing mineralized zones in the underground workings and surrounding rock. While the valve was closed for a short period for a test in 2020, at this time the valve has been left open allowing AMD to flow out of the mine year-round.

In 2023, work was completed at Red and Bonita to reroute the AMD from Red and Bonita Mine. The 2015 design allowed water to flow from the mine and discharge across an adjacent iron fen. As a result of the work in 2023, AMD from the site now flows out a conveyance line, through a culvert, and into a lined earthen ditch before entering Cement Creek. Following this work, EPA's Remedial Program requested that EPA's removal program evaluate replacement of the portal shed to better protect the drainage and workers from rockfall and winter conditions as described in the May 2025 Action Memorandum. 

Regional leadership suspended work at the end of July 2025 due to resource/staffing constraints. The portal shed has been  procured and stored at the Interim Water Treatment Plant in Gladstone.