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Erica Crosby Page 3 of 4 September 21, 2004 New Model An updated computer model will be prepared and submitted to the Division to reflect current hydrologic conditions in C-pit and current water quality data. The results of the mode] will be submitted to the Division no later than October 15, 2004. Monitorin¢ and Compliance Points Cemex will examine the degree of hydraulic connection between A-pit and C-pit to determine whether A-pit is a viable downgradient monitoring and compliance point. The results of this investigation shall be submitted to the Division by November 1, 2004. If it is determined that a different compliance point is needed, Cemex will propose a change in the compliance point from the currently used A-pit water. Source Removal Cemex will substantially reduce the size of the pond in C-pit within 12 months of the time of acceptance of this plan by the Division. The plan has two (2) elements: - Minimize the amount of water entering C-pit - Continue to use C-pit water year-round for operational demands Inflows Cemex will continue its analysis of the water balance in C-pit pond and minimize inflows where practical. Runoff from precipitation and snowmelt will be prevented from entering C-pit where practical by use of diversion ditches and berms. Nothing can be done with incident precipitation. A-pit water is pumped to C-pit for dust control spraying as directed by the Colorado Department of Public Health and Environment Air Quality Control Division (AQCD). AQCD determines the dates and hours of water application but not the volume. Cemex will examine this issue to determine if dust control performance standards can be met with a lower volume of water, however we continually monitor and adjust sprinkler times to minimize inflows while meeting AQCD standards. The water level in C-pit will be monitored on a weekly basis with progress reported monthly to the Division. A water balance analysis will be submitted to the Division within 60 days of approval of this plan. Implementation of recommended inflow controls shall begin immediately upon approval by the Division. C-Pit Water Treatment Richard Henry, Cemex's consulting ground water geochemist, has described the mechanism by which pH and selenium have become elevated and is researching water treatment options. Cemex will treat the water in C-pit to reduce the pH to 9 which meets applicable water quality standards as quickly as possible. A water treatment plan will be submitted to the Division within 30 days of acceptance of this proposal.