PROJ00538

• Contract/PO #: C153581
• Contractor Name: Minnesota Canal and Reservoir Company
• Water District: 0
• County: Gunnison
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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6.6 Hydrology

The watershed area impacting the proposed dam site is shown in Figure 6.6.

6.6.1 Surface Water

Long term Stream flow records for the Dry Fork of Minnesota ereek are limited. Arco eoal
eompany installed stream monitoring equipment in June 1977, as part of the environmental
permitting process for the Mount Gunnison Mine. Based on stream flow data collected during
the years 1978, 1979, and 1980, the estimated mean annual runoff for the Dry Fork of
Minnesota ereek is 1,100 acre-feet (Armstrong, 1980).

Stream flow records for both the upper and lower reaches of the Dry Fork of Minnesota Creek
were provided by the West Elk Coal Company, Inc. These records provide statistical data
regarding the discharge rate and volume for the water years 1987 and 1988. The recording
station for the upper reach is located in the SE 1/4, SW 1/4, Section 2, T 14S, R 90W. The
recording station for the lower reach is located downstream of Minnesota Reservoir in the SW
1/4, Section 31, T 13S, R 90W. The stream flow records suggest that the period of snowmelt
runoff commences in late May, peaks in mid-June, and is completed during July. Stream flow
discharge records for the lower and upper reaches are provided in Appendix e. Figure 6.7
illustrates the seasonal variation in streamflow for the upper and lower reaches of the Dry Fork.
Discrepancies in flows between the upper and lower reaches is primarily due to storage and
discharge of flows within the existing Minnesota Reservoir.

6.6.2 Groundwater

Groundwater quantity and quality data for the project site is not available. It is anticipated that
groundwater flow is approximately parallel to axis of the Dry Fork of Minnesota ereek, and is
primarily confined quaternary alluvial and colluvial deposits within the creek basin.

7.0 SITE SELECTION STUDY

7.1 Site Selection Methodology

SRK performed a site selection study to characterize, evaluate, and identify the most favorable
site Cor the proposed New Minnesota Dam and Reservoir. The formal site selection process
included:

· Regional screening in which the study area is defined, potential sites are identified, and
unsuitable sites are rejected;

· Site characterization whereby topographic, geologic, hydrologic, and environmental
conditions are assessed on a site-by-site basis;

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