2010-07-31_REVISION - M1977300

• Permit No: M1977300
• IBM Index Class Name: REVISION
• Doc Date: 7/31/2010
• Doc Name: Tech. Memo- Response
• From: Cotter Corp./ Whetstone Associates
• To: DRMS
• Type & Sequence: TR11
• Email Name: DB2
• Media Type: D
• Archive: No

M- 19 77-3aa
Whetstone'
Associates
_FA I I
Technical Memorandum
To: David Bird, DRMS
From: Susan Wyman, P.E., P.G.
Date: July 31, 2010
Subject: Response to DRMS letter dated May 19, 2010 regarding
Schwartzwalder Mine Environmental Protection Plan Adequacy Review #2
4109C
The revised Environmental Protection Plan (EPP) for the Schwartzwalder Mine was submitted to the
Colorado Division of Reclamation, Mining and Safety (DRMS) on April 19, 2010. DRMS reviewed
the EPP and issued a letter on May 19, 2010 to Cotter Corporation (N.S.L.) (the Operator)
identifying four corrective actions as Permit Technical Revisions and a fifth corrective action as a
Permit Amendment (revising the EPP). The purpose of this technical memorandum is to summarize
how each issue raised by DRMS in their May 19 letter is being addressed in the revised EPP and to
identify any other modifications to the EPP (such as updating tables to include the most recent data,
etc.).
Issues identified by DRMS are summarized in italics below.
SECTION 7. FACILITIES EVALUATION
1) Operator states on pg. 7-3 "...because flow rates from the mine are extremely low, total mass
loading from the underground workings is small." Other than the mine inflow rates, is there any
direct evidence to support the statement that flow rates from the mine are "extremely low?"
Flow from the mine is controlled by hydraulic conductivity of the bedrock. Hydraulic conductivity
has been determined from numerous sources including underground packer tests, 2007 pumping test
data for the shaft, and mine inflow rates during shaft sinking (Soul6, 1960) and during mine
operations.
Inflow to the mine during operations essentially represents a 40-year pumping test. Long-term
pumping tests are the most utilized, trusted, and reliable source of information on aquifer or bedrock
hydraulic conductivity. The importance of mine inflow data cannot be overstated. The hydraulic
conductivity value for the rock mass determined by mine inflow rates is 2.8x10-7 cm/sec.
The text on page 7-3 has been modified to refer the reader to other sections in the EPP that discuss
hydraulic conductivity.
2) Operator states on pg. 7-3 "Issues related to the flooded mine workings include water chemistry
in the mine, flow rates from the mine, potential interaction with water in Ralston Creek, and
potential pathways in low permeability bedrock. " This list should also include the possibility of
potential ground water pathways in structural conduits such as the Schwartz Trend and perhaps the
West Rogers Fault.
Whetstone Associates, Inc.
243 N. Main St. ? Gunnison, Colorado 81230 ? Phone [phone] Fax [phone]