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
No springs occur in the lease area or within 1 /2 mile
of the lease boundaries. The closest springs to the lease
area are located in Yellow Creek and Corral Gulch.
3.4.1.2 Surface N'arerQuality
There are no site-specific water quality data for the
ephemeral tributary drainages on the Lase tract area. Sparse
data in similar areas suggest that runoff probably contains
a few hundred milligrams per liter (mg/I) total dissolved
solids (TDS). A recent report by Tobin et al. (1985) and
water quality analyses published by the U.S. Geological
Survey indicate that the surface waters of Yellow Creek
and its tributaries can be classified as a mixed bicarbonate
type in the upper reaches, grading to a sodium bicarbonate
type in the lower reaches. This change in water quality
is thought to be caused by groundwater discharge from the
Uinta and Green River formations (W'eeks et al. 1974).
Water temperatures in Yellow Creek range Crom summer
highs in the 86°F to 95°F range, to 3:?°F during the winter
months. Specific conductance, which is related to TDS
content, typically is in the range of 800-1,500 uhmos (550-
1,000 mg/I TDS) in the upper reaches, and 3,000-4,000
uhmos (2,000-2,500 mg/I TDS) at the mouth of the creek.
Dissolved solid concentrations typically decrease during the
spring high-Bow period because of dilution from snowmelt
runoff. During low-Flow periods, the amcentrations increase
because of irrigation return flow and groundwater discharge.
Piceance Creek has similar water quality; it also shows an
increase in TDS in a downstream direction, however, TDS
leveis are generally less in Piceance (:reek than in Yellow
Creek (Weeks et al. 1974).
3.4.2 Groundwater
3.4.1. l Regiow! Sening
The principal usable bedrock aquifers that occur in the
basin are commonly referred to as iihe upper and lower
aquifer systems of the Uinta and Grren River formations.
Figure 3-2 shows a generalized geohydrologic cross section
of the Piceance Basin aquifer system. These aquifers are
recharged at the higher elevations on the west, south, and
eastern margins of the basin, by lateral inFlow and deep
percolation to the upper aquifer through the Uinta
Formation. Flow is generally to the north~•zntral part of
the basin (Weeks et al. 1974). The aquifers discharge to
Piceance Creek and Yellow Creek •which discharge into
the White River. The Piceance Basin groundwater system
probably does not dscharge directly to the White River,
because the White River Flows on alluvium which rests
on the Wasatch Formation, which is hydrologically isolated
from the Green River Formation within the basin. For this
analysis, it is assumed that the groundwater transport of
salt/dissolved solids is a closed system in the Piceance Basin,
with all inputs restricted to the basin and out Flow by way
of discharge to Piceance and Yellow weeks.
Three major aquifer systems occur within the basin: the
alluvial, upper, and lower aquifers. These aquifers have
limited hydraulic connection with one another, and are
considered separate reservoirs. The degree and extent of
hydraulic connections are not yet fully understood and
probably vary considerably by location within the basin.
The major alluvial aquifers are restricted to stream valleys
and do not occur on uplands. Most of the stream valleys
in the basin contain recent alluvial material, ranging in
thickness up to 140 feet, are less than one-half mile in width,
and aze saturated in certain areas. This saturated zone is
the alluvial aquifer, which is generally unconfined and varies
greatly in size and yield from one stream valley to another.
The alluvial aquifer system is important, in that it functions
throughout most of the basin as a transient storage system
to move groundwater to or from streams and the deeper
aquifers.
The upper and lower aquifers are bedrock aquifers, within
the Uinta Formation and the Parachute Creek Member of
the Green River Formation (Figure 3-1 A). The upper aquifer
contains confined and unconfined water bearing zones and
extends from the top of the Mahogany Zone to the surface.
The upper portion of the Uintz Formation contains
discontinuous, unconfined water bearing zones (perched
aquifer) throughout the basin. These beds occur in the ridges
between stream valleys and usually can be identified by
the occurrence of springs above the valley bottoms. Perched
aquifers are sometimes associated with alluvial aquifers,
where streambeds intersect permeable outcrop areas. The
upper confined bedrock aquifer extends from the top of
the Mahogany Zane to the base of the unconfined Uinta.
The principal water bearing zone in the aquifer is the A-
Groove located just above the Mahogany Zone. The
remainder of the upper aquifer consists of confined water
bearing zones that vary with depth and permeability.
The lower aquifer extends from the dissolution surface
up to the base of the Mahogany Zone. The principal water
bearing zone is the B-Groove, and [he remainder of the
aquifer yields varying quantities of water depending on the
depth and the degree of secondazy porosity developed.
Secondary porosity is created principally by fracturing and
as a result oC dissolution of the soluble salt nodules and
layers within the oil shale. The secondary porosity developed
in the dissolution features could result in high rates of water
movement throughout the zone; however, the irregularity
and localized occurrence of the dissolution features also
accounts for some wide variations in porosity and
permeability.
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