GENERAL33297

• Permit No: M1983194
• IBM Index Class Name: General Documents
• Doc Name: COVER SHEET 3 TEXT CHANGES TO DRAFT EIS
• Media Type: D
• Archive: No

3. TEXT CHANGES
hydrologic conditions, (2) provide a arotinuing documen-
tation and factual record of any changes due to lease
operations, and to allow separation of these changes fiom
natural hydrologic changes in the area, (3) provide continuing
check on compliance with lease tertns and with other
applicable laws and regulations, (4) provide earlyron notice
of any detrimental effects or conditions that require further
mitigation or control measures, (5) provide a check on the
efficiency of mitigation and control measures, and (6) provide
factual basis for any needed revisions. to the monitoring
system.
In order to measure potential effects on surface Oows
and water quality, monitoring stations :tre Deeded upstream
and downstream on the main channel of Yellow and
Piceance creeks. Surface water monitoring should include
continuous Oow, precipitation, and a~mprehensive water
quality analysis for major and traa: constituents. The
intensity of monitoring water quality probably can be
reduced following a few years of data collection and analysis.
A groundwater monitoring network is required to further
refine knowledge of the groundwater system (e.g., aquifer
anisotropy), and to detect and quannf}~ as early as possible
any hydraulic and water quality affects from project
operations. The monitoring network will require an adequate
number of properly constructed wells to monitor several
aquifer zones at the mining site and vicinity. Four zones
of critical concern are; (1) the bottom 20-50 feet of the
lower aquifer, which probably will be the first zone affected
by the mining operatiam and by caving of cavities, (2) the
B-groove, which will reflect any upward migration of
hydraulic effects in the bottom zone noted above, as well
as reflect leakage through the Mahogany Zone both From
the supply well and from subsidence, (3}the A-groove, where
the most pronounced effects at the mine sire of pumping
from the supply well will occur. These effects will need
to be separated in the interpretation of data from effects
of leakage across [he Mahogany, and (4) the perched aquifer
in the Uinta Formation, which will reflect both subsidence
effects and inFlows from the surface that may degrade water
quality. Monitoring all of these zones will also serve to
detect and locate leakage of brine from production wells
and/or ravines. In order to be effective, monitoring wells
should not be open to more than 50 ftxt of aquifer section,
and effectively sealed from any communication with other
zones, and in place 6 months prior W mining operations.
Detailed monitoring of subsidence is also necessary in order
to evaluate catrseroffect relations between subsidence and
changes in aquifer properties and in water levels.
Details of the groundwater moniu~ring system for the
commercial phase operation, can best be established after
initial data are collected and analyzed From the pilot project
operations. Refer to Surface and Groundwater sections of
the Environmental Consequences for expected impacts and
further justiLcadon of this monitoring rationale.
Page 4-13
(11)
Column 2, paragraph 2, sentence 1: "Spills of nahcolite
pregnant solution could occur ...:' should read: "Spills
of pregnant solution (sodium bicarbonate) could occur .
(11)
Column 2, paragraph 2, sentence 2: "Surface spillage of
nahcolite would ... :' should read: "Surface spillage of
sodium bicarbonate would ...."
(11)
Column 2, paragraph 2, sentence 5: "...soils from
possible nahcolite spillage ... :' should read: "...soils
from possible sodium bicarbonate spillage ...:'
Page 4-19
(14)
Column 2, replace paragraphs 1, 2, and 3: "No significant
alteration or reduction of waterfowl habitats in Piceance
or Yellow Creek would occur as a result of the No Action,
50,000 TPY, or 125,000 TPY alternatives. Palustrine
wetlands comprising dense nesting and brood cover, and
forage provided by aquatic vegetation and macroinvertebrate
populations are not expected to be measurably impaired.
Reductions in surface water availability would be most
pronounced during the winter low flow period. Average
Oow reductions during the mid-winter occupation period
(November-January) would not normally exceed 6 percent
and would not be expected to significantly reduce the areal
extent of suitable winter habitat.
Implementation of the 500,000 TPY Alternative could
induce notable reduction or degradation of waterfowl
habitats existing in lower Yellow Creek. Flow reductions
during the nesting season (May-July) may average l5 to
30 percent, and over time, could lead to major losses or
alteration of dense streamside vegetation as nesting or brood
cover. Average fall and winter flow losses of 20 to 30 percent
would substantially reduce stream depth and tend to
accelerate the formation and prolong the persistence of ice
cover, thereby reducing the extent of surface water
availability for winter waterfowl use.
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