2012-09-28_REVISION - M1977307 ‎(23)‎

• Permit No: M1977307
• IBM Index Class Name: REVISION
• Doc Date: 9/28/2012
• Doc Name: EPP Submittal- Ex. F to Emergency Response and Control Plan
• From: Cotter
• To: DRMS
• Type & Sequence: AM1
• Media Type: D
• Archive: No

Due to the remoteness of the region, the nearest available hydraulic information for the
Navajo Sandstone comes from northwest of the area in Grand and San Juan counties,
Utah where Lowe et al. 2007 report moderate permeability values and wells that yield as
little as 5 gallons per minute to wells located in fractured portions of the aquifer that yield
as much as 300 gallons per minute. Since the mine site is on the edge of a discontinuous
lens of the Navajo Formation with a maximum thickness of only 40 feet, it is expected
that this unit is not an important source of water in Colorado. The Wingate appears to be
the dominant source of groundwater for the area. Lowe et al. (2007) report that springs
discharging from the Wingate Sandstone, range from 10 to 240 gallons per minute.
Wells used to supply the former town of Uravan also report substantial quantities of
water are possible from the Wingate.
Table 3: Hydraulic Conductivity Values for Selected Rock Units at the Site.
Rock Type Hydraulic Conductivity (cm /s)
Dakota /Burro Canyon (Kdbc)
Mudstone /Shales (Jms,Js)
Jms Sandstones
Entrada Sandstone (Je)
Navajo Sandstone (Jn)
Wingate Sandstone (Jw)
1.0E -04
1.6E -07
1.0E -06
5.0E -05
1.0E -06 to 3.0E -03
3.0E -05 to 5.0E -04
Assuming saturated conditions existed in the Salt Wash Sandstone, a porosity value of
0.2, and a hydraulic gradient of 0.05 (equal to the regional dip of the strata), then
calculated groundwater transport rates for uranium and related constituents from ore
bodies would be approximately one foot a year in a northwest direction. Average
transport rates in the upper -most aquifer, the Wingate Formation, would be less than 100
feet per year in the same northwesterly direction.
Several of the geologic units in the area exhibit low permeability values and restrict the
downward movement of water from surface recharge to underlying aquifers. UMETCO
(1997) conducted a series of packer test in the Summerville Formation to measure the
hydraulic conductivity for work involving the Uravan Mill and the associated waste
disposal facility located on Club Mesa. These tests, conducted at 167 to 270 psi, did not
introduce any water into the formation, indicating that the hydraulic conductivity of the
Summerville Formation is no greater than 1.0 E -08 cm/s. This conclusion is supported
by laboratory testing that measured horizontal and vertical permeabilities of less than 9.7
E -10 cm/s. For all practical purposes, this low permeability value indicates that the
Summerville Formation is an aquiclude - rock incapable of transmitting groundwater.
Peel Environmental Services (1993) conducted hydraulic tests of the Kayenta Formation
using packer tests that showed the formation did not take water at a pressure of 745 psi.
Based on these tests, the report estimated that the permeability of the portions of Kayenta
Formation is 3.8E -08 cm/s - basically impermeable. The test interval was in a shale unit
O'Connor Design Group Inc. T - 12