GENERAL48692

• Permit No: C1981019
• IBM Index Class Name: General Documents
• Doc Name: Proposed Decision & Findings of Compliance
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

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Permit Araa
No significant effect on surface water quality in or adjacent to the permit
area will occur as a result of mining operations. Water quality in and
adjacent to the mining area is highly variable with primary constituents
of concern reflecting seasonal and precipitation- related trends.
TSS values show extreme fluctuations at Taylor, Wilson, and Good Spring
Creeks. Sediment yeild rates for the mine area using the Universal Soil
Loss Equation and a rainfall factor of 30.0 averaged 0.96 tons/acre/year
for the mine permit area. This average was broken down into`-the
component parts of undisturbc-d Sand and land being mined or in a stage of
reclamation. Undisturbed land is expected to contribute 0.49 tons/acre/year
while disturbed lands will yield 3.5 tone/acre/year, The total acreage
contributing to these estimates is 1787 acres, of which a maximum of 279
acres will be disturbed at any one time. The estimated yield of 3.5 tons/
acre/year for the disturbed land is much less than the 5.0 tons/acre/year
maximum acceptable topsoil loss from agriculturally productive land
calculated by the U.S. Department of Agriculture Soil Conservation
Service (SCSJ. The design Limit was based on continued productivity of
topsoils for crop production.
TSS will be controlled in runoff from the permit area by detention ponds
which have been designed to retain runoff water for a minimum of 24 hours
after a storm event. This time period will allow for settling out of
TSS and attainment of water quality standards in the Colowyo Coal Company
NPDES permit. The detention pond design criteria are discussed in the
earlier section, Occurrence of Surface Water.
TDS concentrations in receiving streams are expected to remain within the
ranges of values known to exist presently. The data presented and
discussed earlier show tremendous fluctuations. TDS is inversely related
to flow. That is, as the flow decreases, the TDS values increase as a
result of a larger proportion of ground water seepage into the drainages
as the seasons progress. Runoff-related TDS values are much less due to the
dilufion of the minerals influencing this constituent.
Specific conductivity is a measure of TDS and also shows the same variability.
Parker and Turk (1981) and Bishop and others (1982) have examined and
discussed the potential impacts of mining on the hydrology of the Yampa
River Basin, and have related TDS and specific conductivity to predictive
models of impacts. Both studies show that the Colowyo mine will have no
significant impact on the water quality for both the short-term and long-
term. Other constituents will not be significantly affected as a result
of mining. Iron and manganese mean values did not exceed specific
health-related criteria or show signs of acid mine drainage.