REV12101

• Permit No: M1977215
• IBM Index Class Name: Revision
• Doc Date: 6/15/1998
• Doc Name: GROUND WATER QUALITY ISSUES RELATED TO 9360 ADIT PLUG
• From: DMG
• To: STEVE SHUEY
• Type & Sequence: TR5
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Depdnmern ui Natural Resources
1 117 Sherman 51., Room 215

Dcnvnr. Culurarlu 80203 ' 0~~~~
Phunc: UU31 t4rfiJ Sfi7
FAX: 11011 All-A 1116
DEPARTMENT OF
NATURAL
RESOURCES
~
DATE: June 15, 1998 "°° aomrr
Governn~
lames $. Luchhead
TO: Steve Shuey E~rcmrve Dnec:or

~ .titicharl 8. Lonb
~
/ Division Direau:
FROM: Allen Sorenson L/-,
i7 oC . N0.w~~e ;
RE: Ground Water Quality Issues Related to 9360 Adit Plug, omestake
Miuing Company, Bulldog Mine, Permit No. M-77-215
It is the Operator's technical opinion that the water flowing in the 9360 adit at the Bulldog Mine is
derived from surface water that infiltrates the formation into which the adit was driven, percolates
through the formation until it intercepts the adit, then drips or flows into the adit. The first 1200 feet of
the adit was driven into anon-indurated formation of boulders in a clayey matrix. This formation has
been identified by the Operator as the Creede Formation. At 1200 feet inby of the portal the adit
intersects the contact between the Creede Formation and rhyolite bedrock. Based on historic
observations made during adit construction and mine operations, most water flow to the 9360 adit is
believed to occur along the contact between the Creede Formation and the rhyolite. Some seepage is
also known to occur seasonally in an area about 180 feet inby of the portal. It is the Operator's
intention, by impounding water inflows to the adit behind the recently constructed concrete bulkhead,
to force the water to reinfiltrate the Creede Formation thereby reestablishing ground water flow paths
that existed prior to adit construction. A diagram of the 9360 adit and related elements is attached to
this memo.
Through the approval of technical revision TR-005, Homestake is required to sample and analyze 9360
adit water on a monthly basis. The data generated between December 1997 and April 1998 indicate
that contamination in the 9360 adit water exceeds the Basic Standazds for Ground Water for a number
of pazameters. For example, dissolved lead concentrations in the 9360 adit water range from 0.07 to
0.29 mg/I compared to the standard of 0.05 mg/I, and dissolved cadmium concentrations in the 9360
adit water range from 0.087 mg/I to 0.126 mg/l compared to the standazd of 0.005 mg/I. The Basic
Standazds for Ground Water are established by the Colorado Water Quality Control Commission in
Regulation 4l (5 CCR 1002-41). The Division and the Operator must address the consequences to
ground water quality of reinfiltration of the 9360 adit water following the procedures of Rule 3.1.7 of
the Hard Rock/Metal Mining Rules and Regulations and considering the Interim Narrative Standard for
ground water promulgated by [he Water Quality Control Commission.
The Interim Narrative Standard states that: