2021-05-27_REPORT - C1982057 ‎(2)‎

• Permit No: C1982057
• IBM Index Class Name: Report
• Doc Date: 5/27/2021
• Doc Name: Annual Hydrology Report Adequacy Review
• From: DRMS
• To: Twentymile Coal, LLC
• Annual Report Year: 2020
• Permit Index Doc Type: Hydrology Report
• Email Name: RAR
• Email Name: JLE
• Media Type: D
• Archive: No

Seneca IIW AHR 2020
Requirement Requirement citation Comment
8. Basic Standards for CWQCC regulations Only sites WSD5, WSSF3, WSH7 and WSHFFI
Surface Water 31.1.11 downstream of the Seneca IIW site have their waters
used for irrigation.
Native springs did not discharge above the 5gpm
flow rate where sampling would be indicated during
water year 2020.
The manganese standard (0.2 mg/1), for agricultural
use, was not exceeded during the 2020 water year.
Based on CWQCC reg. 31,the standard of 0.2 mg/l,
applies to plants grown in acidic soils (<6.0 pH).
In alkaline soils,as found throughout the Yoast and
Seneca II W region,the EPA standard would be 10
mg/l. Pre mining manganese baseline values exceeded
the 0.2 mg/1 standard as well.
9. Instream Numeric CWQCC regulation 33.0 15 monitoring sites exist within the Sage Creek, and
Standards Hubberson Gulch/Dry Creek basins: WSD5, WSH7,
WHSF1, WSH9,WSPG7, WSPG46, WSPG47,
WSPG50(native springs); NPDES 5,NPDES 6,NPDES
16,NPDES 17 are within Hubberson Gulch/Dry Creek
Basin as are Spoil Springs 1-5. NPDES 9, WSSF3,and
NPDES 15 are located within Sage Creek basin.
The receiving stream standard for Sage Creek is on
Segment 13c of the Yampa River basin and, on Segment
13d of the Yampa River basin for Hubberson Gulch/ Dry
Creek basin.
The stream standards for Sage Creek and Dry Creek
are based on aquatic life standards. Seneca II Ws'
NPDES discharge limitations are based on constituents
in Senecas'effluent likely to cause an exceedance of
Segment 3e and 3d's numeric standards. Appendix D
of the 2020 report compares standards to water quality
collected from NPDES points and stream sites in the
Hubberson Gulch/ Dry Creek Basin.
The iron standard(total recoverable),was exceeded five
times. None of the exceedances were outside of
premising values. Iron exceedances are likely the result
of high suspended solids. Premising samples also
exhibited elevated manganese and total recoverable iron
values as stated in section 8 above.
A high level mercury test with a method detection limit
of 0.2 ug/1 for streams was run. All high level test
values this year were less than the detection limit. The
mercury standard (0.2 ug/1)was exceeded at sites
WSHF1 and WSD5. None of the exceedances were
outside method detection limits.
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