REV90145

• Permit No: M1988112
• IBM Index Class Name: Revision
• Doc Date: 9/14/2005
• Doc Name: Analysis of Pre-mining Water Quality
• From: Harry Posey
• To: Bruce Humphries
• Type & Sequence: TR26
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Delaartment of Natural Resources
1313 Sherman St., Room 215 C O L O RA D O
Denver, Colorado 80203 DIVISION O F
Phone: [phone] M [ N S RA L $
FAX: [phone] G E O L O G Y
RECLAMATION•MINING
SArETY•SCIENCE
Date: S ptember 14, 2005 Bill Owens
Governor
Russell George
TO: BPUCe HUmphrle~ Executive Director
/ Ronald W. Cattany
L/ From: I-Iarry POSey Division Director
Natural Resource Trustee
RE: Review: "Analykis ofPre-mining water quality in the vicinity of the West Pit;"
Battle Mountain Resources Inc., San Luis Project, M-1988-112; TR-26
The above-captioned Technical Memorandum (Tech Memo), dated January 3, 2004, was submitted to the
Division on February 1, 2005. The Tech Memo was prepared in response to outstanding issues related to
TR-26, namely, to answer whether West Pit water quality, after natural flushing and treatment to remove
contaminants, has reached either apre-mining or ambient groundwater condition.
The project at hand was permitted in 1988. As part of the application, the company submitted a set of
groundwater quality information collected from exploration drill holes prior to the mine permit
application. The existence of such pre-mining baseline data is unusual for permits of this era.
Exploration drill holes were mined out by the operation after 1988.
"Ambient Groundwater Quality" is defined in the Rules and Regulations at 1.1(5) as follows:
"Ambient Groundwater Quality" for mining operations permitted prior to January
31, 1994, ambient groundwater quality shall mean the quality of the groundwater
at the mine site as of January 31, 1994. For mining operations permitted on or
after January 31, 1994, ambient groundwater shall mean the quality of
groundwater at the time of submittal of the permit application. In establishing
ambient groundwater quality, an Operator or Applicant shall use available or
collected groundwater data sufficient to characterize the site's ambient
groundwater quality and submit such information in a form suitable to the Office.
Based on the Division's procedures for establishing ambient conditions at other pre-1994 sites, the San
Luis Project data set provides a sound basis for determining pre-mining baseline, even though the actual
number of samples is less than that desired for a rigorous statistical assessment. Also, based on principles
of weathering and water-rock interactions, it is likely that groundwater quality that existed near the mine
while excavation was in progress was more degraded than the groundwater condition prior to mining.
The 2004 Tech Memo provides a synthesis ofpre-mining and current West Pit water quality. Based on
this assessment, the Tech Memo concluded:
"Current backfill groundwater concentrations are equal or less than the pre-mining,
shallow ground water chemistry in the bedrock aquifer, The concentration of TDS,
sulfate, iron, and manganese in the West Pit backfill are statistically less than the
average pre-mining concetnrtions in the shallow bedrock aquifer. Current fluoride
Office of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey