HYDRO30666

• Permit No: M1977208
• IBM Index Class Name: Hydrology
• Doc Date: 6/18/2004
• Doc Name: Groundwater Response Plan
• From: DMG
• To: CEMEX Inc.
• Media Type: D
• Archive: No

STr~TE OF COLORr~DO
gIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
7373 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
June 18, 2004 '~
Mr. John Lohr
CEMEX
P.O. Box 529
Lyons, CO 80540

RE: CEMEX, Inc., Lyons Mine, Pemut No. M-1977-208
Groundwater Response Plan
Deaz Mr. Lohr,
COLORADO
DIVISION O F
MINESRALS
GEOLOGY
A£0.ANATfON•NINING
SAf ETY•SCIENCE
Bill Owens
Governor
Russell George
Executive Director
Ronald W. Cattany
Division DireROr
Natural Resource Trustee
This letter is in response to the potential exceedance of the numeric protecfion level (NPL) for selenium
in the C-Pit based on sampling conducted on April 16, 2004 and May 19, 2004.
In regard to the April 16, 2004 sample it was previously noted to CEMEX that it maybe in error due to
the analytical method. The lab report indicates selenium was measured by the total selenium method.
However, selenium is regulated based on dissolved selenium. The change from total to dissolved
method was effective by the December 30, 2001 regulations for the basic standards for groundwater
(Regulation No. 41) administered by the Colorado Department of Public Health and the Environment
(CDPHE) Water quality Control Cornmission. A copy of a portion of this rule is attached for your use.
DMG would require that the selenium concentration meet the lowest state water quality standazd for
selenium, which would be measured by the dissolved or potentially dissolved method, depending on
current CDPI-IE protocols. The Lyons Pit monitoring gazameters will need to be revised to reflect a
'change from an analytical method of total to dissolved for selenium.
Groundwater monitorine stations:
Several features aze implicit to groundwater monitoring and should be put into practice at the Lyons
Mine if not already so.
1. Groundwater should be monitored downgradient of all potential contaminant sources.
2. Groundwater monitoring stations should include both monitoring (early warning) points and
compliance points. The number and placement of monitoring and compliance stations
should be based on site-specific conditions and, in order to detect contamination from all
potential sources, composed of single or combined contaminant streams.
3. Monitoring points should be placed as close downgradient of the contaminant sources as
practical. In all cases, monitoring points should be sufficiently close to contaminant sources
as to detect contaminant discharges very soon after such a dischazge, and well within the
projected life of the mine.
4. The compliance points should be downgradient of the monitoring points, should be within
the permit boundary (even if an island outside the existing boundary), and should be
sufficiently close to the monitoring points as to detect contamination well within the life of
the mine.
5. Monitoring and compliance stations should be placed in the same aquifer or aquifers.
6. Where there is potential for contamination of more than one aquifer, the other aquifers
should have established monitoring and compliance points.
Once of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey