2020-10-27_PERMIT FILE - C1981035 ‎(22)‎

• Permit No: C1981035
• IBM Index Class Name: Permit File
• Doc Date: 10/27/2020
• Section_Exhibit Name: KII Appendix 16 Dunn Ranch LBA Technical Resources Report
• Media Type: D
• Archive: No

coal-bearing sedimentary rocks of Late Cretaceous age (100-65 million years ago). Coal was deposited in
a series of regressive/transgressive shoreline migrations in marginal-shore swamps, marshes, and other
marine sediments deposited behind barrier beaches that formed a northwest/southeast trend. These
coal-bearing sediments were transected by northeast-trending streams, resulting in the fragmentation of
the coal deposits by stream sediments.The main Late Cretaceous geologic units of hydrologic interest are
part of the Mesaverde Group and include the Cliff House Sandstone,the Menefee Formation(coal-bearing
unit), and the Point Lookout Sandstone. These are overlain by Quaternary age sediments in stream
channels, of which the Hay Gulch alluvium is the most important hydrologic unit (RHS 2016a).
2.3.1.3 Surface Water Resources
The surface water drainages within the CIAA for surface water are considered ephemeral and intermittent
by OSMRE based on 30 CFR 701.5 (OSMRE 2017). There are no perennial streams in the CIAA; however,
Hay Gulch Ditch and the Huntington Ditch/Reservoir/Pipeline carry irrigation water diverted from the La
Plata River on a year-round basis. The Mormon Reservoir, a 26-acre reservoir constructed in 1910 for
irrigation water has a capacity of 1,100-acre ft and holds water on a year-round basis. Ephemeral streams
flow only in response to precipitation events or snow melt. East Alkali Gulch and West Alkali Gulch are
ephemeral drainages that cross the King II workings and are tributary to Hay Gulch below the Mormon
Reservoir. An intermittent stream is a stream with a portion of the stream below the water table, so that
there may be flow in a segment of the stream over part of the year that is derived from groundwater.
Surface water features are shown in Figure 2.3-2. Because there are no perennial streams and surface
water resources are limited in this semi-arid environment, surface water quantity and quality are related
mainly to storm water runoff and snowmelt.
Surface Water Regulatory Requirements
Surface water runoff from mining areas is required to be managed in a manner that prevents additional
contribution of suspended solids to streams outside the permit area to the extent possible with best
available technology(30 CFR 816.41(d)). GCCE complies with this requirement by designing, constructing,
and maintaining siltation structures, impoundments, and clean water diversions. Quarterly reports are
submitted to CDPHE Water Quality Control Division as required by GCC's NPDES Permit#COG85001.
Surface Water Baseline Quantity
Because of the lack of perennial streams in the CIAA, quantification of surface water is limited to storm
water events or flow in irrigation ditches (OSMRE 2017). No storm water events have been successfully
measured for flow or water quality to date.The Hay Gulch Ditch is monitored on a quarterly basis at two
locations, the Hay Gulch Ditch Upgradient and the Hay Gulch Ditch Downgradient locations. These
monitoring sites are located upgradient and downgradient respectively of the King I and King II mines.
Monitoring for the period from April 2016 through March 2017 showed a range of flow from 0.28 to 1.5
cubic ft per second (cfs). Upgradient and downgradient flow rates were comparable and seldom varied by
more than 20 percent. The typical flow rate at these locations was on the order of 1 cfs (OSMRE 2017).
The Huntington Ditch,which delivers the King II Mine operations water supply is not specifically monitored
for flow, but the Huntington Reservoir that the ditch flows into typically holds about 40 acre-ft of water.
Dunn Ranch Area LBA and Mining Plan Modification 54
Technical Resources Report