2011-04-06_REVISION - M1977300 - Laserfiche WebLink

Home Browse Search

MALCOIA1 PIRNIE The Water Division of ARCADIS SUMMARY ARCADIS Technical Memorandum Date: April 6, 2011 To: Daniel Arnold, Esq., Denver Water Copy: Jason Kerstiens, Malcolm Pirnie From: Tim Cox, P.G. CGWP, Jeff/Gillow, PhD., and Phil DeDycker, P.E. ARCADIS Re: Addendum for Environmental Protection Plan Review Schwartzwalder Mine Denver Water retained ARCADIS U.S., Inc. /Malcolm Pirnie, Inc. to review and comment on the Environmental Protection Plan (EPP) for the Schwartzwalder Mine, which is owned by Cotter Corporation (N.S.L.) (Cotter). The EPP was prepared by Whetstone Associates Inc. (2010) and its intent was to provide information for improvements in the protection of human health, property, and the environment related to affected areas of the mine including reclaimed waste rock piles, the flooded underground workings, and valley fill. The ARCADIS /Pirnie review of the EPP (EPP Review) is contained in a January 25, 2011 draft Technical Memorandum that was submitted to Denver Water, and then provided to Cotter. Cotter subsequently commented on the EPP Review in a February 22, 2011 document. Attachment 1 of that document contains comments by Cotter and Attachment 2 contains comments by Cotter's consultant Whetstone Associates. This Addendum to the EPP Review responds to Cotter's comments; the original EPP Review remained unchanged. The comments by Cotter and Whetstone provide several alternative explanations for the nature and extent of uranium and other site contaminants in groundwater and in Ralston Creek (creek). Additional information and data, not originally contained in the EPP, is provided in some of the comments and offers further insight on historical water quality conditions, operation of sumps, and water treatment. The additional data and data collection efforts are appreciated. Several of the alternative explanations, however, continue to be based on indirect evidence and do not change the major findings in the EPP Review, even after considering the additional data. Corrections to statements in the EPP (e.g., cycling of water from Sump 1 to Sump 4) are made in the comments, indicating questionable knowledge of water management at the site over the years. Additional information and maps showing locations of unplugged coreholes are provided, which is helpful, but after review of the maps the discharging corehole that was discovered in July 2010 may be a different corehole than believed by Cotter. There are potentially three other unplugged coreholes that are shown to be completed into the mine workings that could be discharging mine pool water. 4-1q77 ,4Af -95Z