2021-12-22_PERMIT FILE - C1981019A

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RULE 2 PERMITS provided in the WDEQ guidelines. These samples are all in interburden and almost exclusively beneath the deeper coal seams (Exhibit 6, Item 6). Mining operations will naturally rebury these deeper interburden layers in the lower portions of the pit. Of 308 regraded spoil piles in Colowyo Mine operations reported in the 2005 Annual Reclamation Report, only eight exceeded the WDEQ SAR "suitable" criterion of 10, only two exceeded the permit "suspect level" of 15, and the mean value was 2.01. As such, SAR is not expected to be an issue in the regraded spoil in the South Taylor pit. Saturation percent was outside of the WDEQ "suitable" range in 477 feet, or 10.9% of the borehole intervals. Mean saturation percent ranged from about 35 to 50%. During reclamation, overburden is homogenized and the saturation percent of the various layers is averaged. As reported in the 2005 Annual Reclamation Report, the 34 samples of regraded spoil analyzed for percent saturation ranged from 28 to 60.5% saturation, which is within the WDEQ "suitable" range. There are no WDEQ "unsuitable" criteria for percent saturation. The anticipated root and aquifer zones within the regraded overburden of South Taylor/Lower Wilson should be of suitable quality due to the following: • There is a limited amount of unsuitable overburden material when compared to the amount of suitable overburden material within the South Taylor/Lower Wilson pit areas. • In general, the limited amount overburden material that is unsuitable will be mixed with suitable material to create suitable root zone and aquifer restoration material during mining and the backfilling of pits and out -of -pit disposal facilities. • Unsuitable overburden materials that represent a considerable portion of the overburden to be mined will be identified, selectively handled, and isolated from aquifer and root zone areas within the backfilled pits and out -of -pit disposal facilities using the methods specified in the mine plan. • Historic regraded spoil data from the existing operation demonstrates that current mining practices consistently result in suitable overburden at this mining location. • The approved overburden suitability criteria for the Colowyo Mine can be found in Volume 1, Section 2.05 of the existing permit.Hydrology Description The objective of this section is to meet the requirements of Rule 2.04.7 et seq. by furnishing hydrological information for the permit revision area in sufficient detail to describe the following: • Character of surface and groundwater resources; • Baseline groundwater quantity and quality; • Baseline surface water quantity and quality; • Seasonal variations in surface and groundwater quantity and quality; and • Ownership and use of surface and groundwater resources. To meet the requirements of Rule 2.04.7 et seq. both general and detailed groundwater and surface water resource information was collected, compiled, and analyzed. Groundwater resource information will be provided first followed by surface water resource information. 2.04.7(l) Groundwater Resource Information Both general and detailed information regarding groundwater in the vicinity of the mining areas will be presented in the following subsections. South Tavlor/Lower Wilson — Rule 2, Pa -e 18 Revision Date: 4/7/17 Revision No.: RN -07