A recent report (June 2006) makes fascinating reading and instructive reporting. I refer to the Reclamation Feasibility Report Henson Creek Watershed (June 2006) put out by the Colorado Department of Natural Resources, Division of Minerals and Geology. The report was prepared as part of an evaluation of the impact of drainage from mines in the Henson Creek watershed and the potential impact of mine drainage on the Lake Fork of the Gunnison River I Hinsdale County in the San Juan Mountains of southwestern Colorado.

Prospecting began in Hinsdale County in 1860. Mining began in 1871. There are numerous inactive mines in the Henson Creek watershed, but no active mines.

Both natural and mining related metal loadings affect water quality in Henson Creek. The report describes work done to quantify the contribution by natural and mining sources. Total zinc and manganese were chosen as the indicator metals. Reasons include the presence of zinc and manganese in the adit drainage of all the mines surveyed, the correlation of zinc and manganese with other heavy metals of concern, and because of the “conservative” nature of these metals.

The report concludes: a maximum of 35 percent of the zinc load in Henson Creek is from mining waste; six percent of the zinc is from adits; a maximum of three percent of the manganese in Henson Creek is from mining wastes; and 30 percent of the manganese is from adits. The report concludes that the majority of the metal loading is therefore from natural sources.

To address the mining-related contributions, the report makes recommendations for each site. Seven of the 23 sites surveyed are recommended for no action at this time, thirteen waste rock piles are recommended for reclamation, five of the 23 sites are recommended for adit discharge reclamation, seven for further investigation. Here are some of the specific recommendations that caught my attention:

  • Due to the inaccessibility of both dumps by relative to road access, reclamation of the two waste piles is questionable. The Hoffman site would require crossing an expanse of tundra, while the Engineer site could be accessed from above. Both dumps could be reclaimed with limestone amendments or subsurface burial. The Engineer site would require extensive up-slope handling with a dragline. The measurability of this measure on water quality would not be cost effective.
  • Because of the natural amelioration which occurs from DM-7, no reclamation or treatment of water drainage from the Chicago tunnel is recommended at this time. Zinc removal could be increased through the addition of limestone to the bog/beaver pond area. Because of poor access, this would have to be done by hand or helicopter. The potential negative impacts to the biology of the bog area outweigh any potential benefits to water quality.
  • The Hanna Mill site has not been reclaimed because it is on private land. The current landowner has chosen not to reclaim the site because the site is slated to be the location of a mountain cabin. The land owner plans to use the flat area of the mill building foundation and associate waste rock as a foundation. The foundation will be poured concrete, which would help to immobilize some of the metal in the waste rock pile. If landownership changes, recommended reclamation of this site would either be to remove the waste rock to the Ute-Ule repository or to create an on-site repository and revegetate.
  • The Excelsior waste rock pile is a seasonal source of heavy metals to Henson Creek. The recommended site reclamation is to remove the waste from the drainage, and dispose of the materials in an excavated area on the slope west of the mine.
  • The reclamation recommended for this site is to divert the drainage from the spring above by constructing a ditch around the waste pile. This can probably be accomplished by hand methods.