The WCRC has found that the Nelson Tunnel has been found to be the primary contributor of metal contamination to Willow Creek. In 2005, the WCRC contracted McLaughlin Rincón to evaluate the feasibility of treating discharge from the Nelson Tunnel to reduce metals loading to Willow Creek and to the Rio Grande.  The study investigated conventional chemical, biological, and electrical treatment methods, and examined potential treatment locations, the potential to use hydropower generation, and the potential for heat recovery.  McLaughlin Rincón recommended use of chemical hydroxide precipitation to treat Nelson Tunnel water.

Nelson Tunnel Water Management Feasibility Study

Computer modeling suggested that chemical precipitation treatment methods may not be able to remove some metal contaminants in Nelson Tunnel water to table value standards. The WCRC performed bench scale testing to evaluate treatment of actual Nelson Tunnel water with lime and caustic soda. The bench scale tests indicated that treatment using hydroxides should be able to remove metals to effluent standards. 

Bench Scale Testing of Chemical Precipitation Treatment Effectiveness

Funding for this study was provided by a grant from the U.S. Environmental Protection Agency.