2011-08-29_REVISION - M1986015 ‎(11)‎

• Permit No: M1986015
• IBM Index Class Name: REVISION
• Doc Date: 8/29/2011
• Doc Name: Amendment Submittal
• From: Continental Materials Corporation
• To: DRMS
• Type & Sequence: AM4
• Media Type: D
• Archive: No

Ground Water Zone
Comments
Areas within 600 -feet of Phase 7 Mining
_
Potential ground water level impact in excess of 15
feet in most areas. Average pre- mining saturated
thickness of alluvial aquifer is 20 to 30 feet.
Mitigation may be needed for some affected wells.
Areas with More Than 5 feet of Potential Water Level
Drawdown (600 feet to 2,170 feet from Phase 7
mining)
Potential ground water level impact in excess of 5
feet in most areas. Average pre- mining saturated
thickness of alluvial aquifer is 20 to 30 feet. Need
for mitigation is possible for some affected wells.
Areas with Less Than 5 feet of Potential Water Level
Drawdown (2,170 feet to 3,400 feet from Phase 7
mining)
Potential ground water level impact less than 5 feet.
Average pre- mining saturated thickness of alluvial
aquifer is 20 to 30 feet. Need for mitigation is
unlikely in this area.
Ground water zones based upon ground water analysis using the Dupuit equation for unconfined ground water flow in a regression of
nearby ground water level drawdown and the following inputs: distance to zero drawdown (L) = 3,400 ft, aquifer saturated thickness at
Phase 7 dewatering (H I) = 1 ft, aquifer saturated thickness at zero drawdown (H2) = 25 ft.
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feet of remaining saturated alluvial aquifer thickness is adequate to support most domestic and
commercial water demands. Estimated ground water level drawdown from dewatering will range
from more than 15 feet, close to Phase 7 boundary to less than 5 feet, at approximately 2,170 feet
from the Phase 7 boundary.
Following mining, the pit will be backfilled above the ground water level. Therefore, the ground
water table is expected to return to near its pre - mining level and wells will not be affected
following mining. To address ground water level impacts, mapping was prepared of potentially
impacted areas and TMOP has completed an inventory of wells within approximately 2,170 feet
of the Phase 7 mine permit area.
Mapping of areas potentially affected by dewatering was developed based upon TMOP's
experience and water level data from dewatering at the Phase I mining area. A relationship
between distance from dewatering and ground water level decline was determined from the
Phase I water level data. This relationship was used to estimate ground water level impacts at
distances from Phase 7 mining, shown in Figure G -1. Three potential ground water level zones
were identified based upon distance from Phase 7 mining and potential ground water impacts:
A summary of the methodology used to prepare water level impact projections is presented
below:
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