GENERAL36100

• Permit No: C1981012
• IBM Index Class Name: General Documents
• Doc Date: 12/1/1988
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN1
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

The alluvial flood plain ground water is a calcium-bicarbonate type water
with a chemistry similar to that of the Purgatoire River (see permit
application Exhibit 6, Figures 12 and 14), but with slightly higher
concentrations of the major ions. The only significant difference with
respect to the major ions is an elevated sodium concentration in the
alluvium relative to that in the stream. Although seepage from the New
Elk Mine refuse pile has high sodium concentrations, mining activities
are not the sole cause of the elevated sodium levels. Sodium is high in
all four wells. The sodium is probably being contributed, in part, by
the dissolution of one or more sodium salts contained in the soils or
alluvium.
Concentrations of major ions and the conductivity of alluvial wells at
the downstream Golden Eagle Mine site are less than the concentrations
and conductivities of wells at the New Elk Mine site (Exhibit 6,
Table 3). This is probably the result of inflows of better quality water
from the North Fork of the Purgatoire that joins the Middle Fork of the
Purgatoire between the two mine sites.
D. Surface Water
The Purgatoire River, a tributary of the Arkansas River, is the major
surface drainage feature of the area. The headwaters of the Purgatoire
are located on the eastern slope of the Sangre de Cristo Range west of
the study area. The three major branches of the river, the tJorth Fork,
Middle Fork, and South Fork, all converge within the study area. The New
Elk Mine is located on the Middle Fork, about 1.5 miles upstream of the
confluence of the North and Middle forks of the river. The Golden Eagle
Mine is located downstream of the confluence of the North and Middle
Forks of the Purgatoire River, and approximately two miles upstream of
the confluence of the South Fork and the main stem of the Purgatoire
River at Weston.
The headwaters of the Purgatoire River system are in excess of 9,000 ft.
elevation and receive substantial snowfall. For example, the mean annual
precipitation at North Lake at the head of the North Fork (elevation
8,800 ft.) is 20.55 in. of which 7.48 in. is in the form of snow. On the
other hand, the mean annual precipitation at Trinidad (elevation
6,030 ft.) is 13.22 in. and only 2.19 in. of this total is in the form of
snow. The disturbed areas of the mine sites are between 7,000 and
7,500 ft. in elevation and are located between the Trinidad and North
Lake stations. The mean annual precipitation at the New Elk Mine is
calculated to be 16.9 in. with snowfall contributing 5.00 in. to this
total.
In order to assess the effect of mining operations on the river the mine
operator has monitored surface water flow and quality at three stations
along the Purgatoire River since February 1984. The stations are
designated PRS-1, 2, and 3. The records of this monitoring appear in
Exhibit 10 of the renewal application. PRS-1 is located upstream from
the surface facilities at New Elk Mine and the confluence of the North
and Middle Forks of the Purgatoire River. PRS-2 is below the FJew Elk
Surface facilities and confluence of the North and J4iddle Forks of the
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