PERMFILE46021

• Permit No: M2000158
• IBM Index Class Name: Permit File
• Doc Date: 3/23/2001
• Doc Name: POTENTIAL GROUND WATER RESOURCE IMPACTS ASSOCIATED WITH STARTER PIT DEWATERING
• From: DENNIS MCGRANE
• To: GREG ROUSE
• Media Type: D
• Archive: No

Memorandum to Greg Roush •
Mazch 23, 2001
Page 7
ADDTI'IONAL WAYS TO MININIIZE IMPACTS
We have identified the following additional ways to minimize the effects of the proposed mining
activities on existing wells:
Begin pit mining in eazly summer. Aquifer dewatering would likely not occur until after
the irrigation season and would be complete before the following summer. In this way,
the greatest impacts would occur in the late winter and spring when ground water
demands are lowest.
• Begin mining as faz away from existing irrigation wells as possible; as close to the Platte
River as Possible and in areas of reduced aquifer transmissivity (See Hurr's Map).
CONCLUSIONS AND RECOMMENDATIONS
Starter pit dewatering will cause water level declines off-site for a short period of time. We .
calculated the maximum amount of that drop to be around 5 feet 2000 feet from a starter pit site
located above the most permeable portion of the aquifer (Table 3). We believe that the
mitigating effects of aquifer subflow and recharge will reduce these effects by around 50 percent.
If this occurs, the impacts to nearby well users will likely be insignificant.
To further minimize impact to other ground water users, we recommend that S&H Mine:
• Begin pit mining in early summer so that aquifer dewatering is complete prior to the next
irrigation season; and
• Begin mining as faz away from existing irrigation wells as possible; as close to the Platte
River as possible and in areas of reduced aquifer transmissivity (See Hurr's Map).
SOURCES
Driscoll, Fletcher, 1986. Gtound Water and Wells; Johnson Division, St. Paul, Mn. 55112
Hurr, Theodore, 1972. Hydrogeologic Characteristics of the Valley-Fill Aquifer in the Greeley
Reach of the South Platte River Valley, Colorado; USGS Open File Report 73-124.
McWhorter, David B. and Sunada, Danial K., 1977. Ground Water Hydrology and Hydraulics;
Water Resources Publications, Ft. Collins, Colorado.
LEONARD RICE CONSULTING WATER ENGINEERS, tNC.
2000 CLAY STwEET. SUITE HOO. DENVEF. COLOPADO 8021 1-51 1 9 • PHOHe [phone] • Fwx (303) 455-OI 15