2009-05-19_REVISION - M1981021 ‎(36)‎

• Permit No: M1981021
• IBM Index Class Name: REVISION
• Doc Date: 5/19/2009
• Doc Name: EPP amendment ‎(AM-01)‎ submittal ‎(part 1)‎
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM1
• Email Name: RCO
• Media Type: D
• Archive: No

Section 7
Groundwater Information
E
•
Fxhihit 7_1 _ Definition of local hvdroaeoloaic units in vicinity of the Sunday Mines Group
Hydrogeologic Unit Local Description
Defined by Weir et al. Hydrologic
1983 Unit
Mesozoic Aquifer Navajo Aquifer Aquifer contains saturated portions of the Cutler
Formation, Chinle Formation, Wingate Sandstone,
Kayenta Formation, Navajo Sandstone, and Entrada
Sandstone. The aquifer is overlain by shale of the
Summerville Formation, and underlain by rock salt of
the Paradox Member of the Hermosa Formation.
Salt Wash Aquifer includes the saturated portions of the Saltwash
Aquifer Member of the Morrison Formation. This aquifer is
overlain by bentonitic shales of the Brushy Basin
Member of the Morrison Formation and is underlain by
shale of the Summerville Formation.
Tertiary to Upper Dakota Aquifer Aquifer contains the saturated portion of the Dakota
Cretaceous aquifer Sandstone and the Burro Canyon Formation. It is
overlain by the Mancos Shale and underlain by shale of
the Brushy Basin member of the Morrison Formation.
Mesaverde Not present in the Sunday Mines Group area.
Aquifer
It is likely that groundwater flows laterally within the sandstone aquifers in a
direction that is generally towards the Dolores River. However, local flow directions
in direct vicinity of the mines are likely modified by the complex structural geology of
area, and groundwater in the vicinity of the mines may take a complex route in the
process of moving generally towards the Dolores River. A hydrogeologic divide is
interpreted to be present coincident with the topographic divide between Big
Gypsum and Disappointment Valleys with groundwater north of the divide staying
within the Big Gypsum Creek watershed and groundwater south of the divide
staying within the Disappointment Creek watershed.
The Salt Wash aquifer and the Dakota Aquifer crop out adjacent to the Dolores River
in the Disappointment Creek watershed, and the Salt Wash aquifer crops out adjacent
to the river in the Big Gypsum Creek watershed. These are likely areas of
groundwater discharge to the river. Groundwater discharge from the Dakota aquifer
is also reported from several artesian wells in the Disappointment Creek watershed
(Weir et al. 1983).
Groundwater in the vicinity of the mine affected areas is generally unconfined.
Confined conditions are reported for aquifers in Disappointment Valley, and it is
7-3
TA64986-Denison Mines\Task Order 4 - EPP Sunday Mines Gmup\FINAL EPP\FINAL - Environmental Protection Plan Sunday Mines.doc