HYDRO31064

• Permit No: M1980244
• IBM Index Class Name: Hydrology
• Doc Date: 5/23/1997
• Doc Name: MEETING AGENDA
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman 51., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: U031 8 3 2-81 06
DATE: May 16, 1997
TO: Bruce Humphries
Berhan Keffelew
Jim Stevens
FROM: Harry Posey
RE: Preparation for meeting with hydrologic/geochemical modelers for CC&V
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DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
lames S Lochhead
Execwive Director
Michael B. Long
Division Director
On May 23, we are to meet with CC&V, Adrian Brown Consultants, and Shepherd-Miller to
lay our a project to define the hydrologic conditions of the Cresson diatreme and surrounding
area, and determine whether the diatreme has adequate buffering capacity to attenuate the
effects of acid rock drainage that will be generated in the waste rock. This memo identifies the
questions that I think should be answered from a geochemical perspective. Berhan already set
forth his thoughts on the hydrology, and I believe Jim will do so as well.
1. Determine wha[ portion of the water discharging from the Carlton Tunnel comes
through the diatreme and what portion comes through other rock. (This probably will
require the use of isotopic measurements such as sulfur or lead.)
If one could determine what portion of the discharge water comes through the
diatreme, then the infiltration rate could be determined explicitly. Previous estimates
of infiltration were based on the simple assumption that all water exiting the Carlton
portal came through the diatreme, but only through the diatreme. This seems
unrealistic given the structural complexity of the area.
Determine the origin of the alkalinity in the discharge water.
The infusion of C02 into the diatreme, which the USGS says comes from the mantle,
could cause carbonic acid to form as it mixes with undersaturated water in the
diatreme. However, the Ca to CO, ratios in some of the analyses suggest that the
water is saturated with respect to calcite (CaCO~). Whether the water is calcite
saturated due to the high COZ content coupled with the dissolution of calcium
minerals, and whether the Ca source is calcite, Ca-plagioclase, or other Ca mineral, is
not known. This needs to be determined because it should be used in the modeling
calculations to anchor the abundance of available alkali and thereby quantify the
abundance of acid neutralizing materials.