2012-10-01_REVISION - M1977305 ‎(16)‎

• Permit No: M1977305
• IBM Index Class Name: REVISION
• Doc Date: 10/1/2012
• Doc Name: EPP Submittal- Part 2, Ex. Q to QA/QC Summary.
• From: Cotter Corp.
• To: DRMS
• Type & Sequence: AM1
• Media Type: D
• Archive: No

8.3.3 Hydraulic Parameters
There is only a limited amount of hydraulic data available for the geologic formations
capable of transmitting water at the LP -21 mine area. Consequently, estimates of
hydraulic conductivity (permeability) are based on limited site data and reported values
for the type of rocks underlying the mine. Reference values for the Entrada Sandstone
are from Lohman (1965) while sandstone and shale unit values are from Freeze and
Cherry (1979).
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 reports 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 Formation.
Table 2: Hydraulic Conductivity Values for Selected Rock Units at the Site.
Rock Type
Dakota/Burro Canyon (Kdbc)
Mudstone /Shales (Jms,Js)
Jms Sandstones
Entrada Sandstone (Je)
Navajo Sandstone (Jn)
Wingate Sandstone (Jw)
Hydraulic Conductivity (cm/s)
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 0.07, equal to the regional dip of the strata, then calculated
groundwater transport rates for uranium and related constituents from ore bodies would
be approximately less than 4 feet a year in a northwest direction. Average transport rates
in the upper -most aquifer, assuming that the Wingate Formation contains groundwater,
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.
Geotechnical reports for work involving the Uravan Mill and the associated waste
disposal facility located on Club Mesa. UMETCO (1997) conducted a series of packer
test in the Summerville Formation to measure the hydraulic conductivity. 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
O'Connor Design Group Inc. U - 13