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2020-06-08_REVISION - C1982057 (20)
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2020-06-08_REVISION - C1982057 (20)
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Last modified
12/27/2024 8:36:47 PM
Creation date
6/11/2020 5:40:04 PM
Metadata
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Template:
DRMS Permit Index
Permit No
C1982057
IBM Index Class Name
Revision
Doc Date
6/8/2020
Doc Name Note
Hydrology Demonstration
Doc Name
Initial Application Materials
From
Seneca Property, LLC
To
DRMS
Type & Sequence
SL7
Email Name
RAR
JLE
Media Type
D
Archive
No
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(WSSPGS) is located upstream of NPDES Outfall 016 (see Figure 1). The post-mining land use of the <br /> reclaimed parcels in this Phase III bond release application are designated as livestock grazing and <br /> wildlife habitat.Therefore the water quality data collected from these springs are compared to the <br /> CWQCC Agricultural Use surface water standards as established in CDPHE Regulation 31. <br /> Table 20 includes the analytical results for the spring samples collected from 2015—2019. No <br /> Agricultural Use surface water quality standard was exceeded at the Spoil Springs.The Manganese <br /> Agricultural Use Standard in CDPHE Regulation 31 were recently updated to specify that this standard is <br /> only applicable to plants that are grown in areas with acidic soils (<6.0 pH). In alkaline soils, as are found <br /> in the Seneca II-W region, a more appropriate standard would be 10 mg/L(EPA, 1976). None of samples <br /> collected from the spoil springs exhibited manganese above 10 mg/L.There were also no excursions of <br /> the CDPHE Yampa Segment 13d acute or chronic standard for manganese at the spoil springs or at <br /> surface points WSH7 (SW-S2W-SG7), WSHF1 (SW-S2W-FG1), WSDS (SW-S2W-SG5) downstream of <br /> outfalls 005, 006, and 016. <br /> Sage Creek Segment 13e <br /> There were no excursions of the CDPHE Yampa Segment 13e Sage Creek water quality standards at <br /> downstream monitoring point WSSF3 (SW-S2W-FG4) during the last five years (Table 6). As discussed <br /> above in the Dry Creek Mercury section the lab used by SCC has a method detection limit for mercury <br /> (0.02 ug/L)that is above the 0.01 ug/L aquatic life standard. None of the samples collected during the <br /> last five years exceed the labs method detection limit.The CDPHE performed a reasonable potential <br /> analysis for the Sage Creek NPDES outfalls to exceed the mercury limits during the last NPDES renewal <br /> and determined that there was no reasonable potential for the mines outfalls to exceed the mercury <br /> limit. As discussed in greater detail in the Dry Creek Sulfide section the sulfide detection method used by <br /> SSC's lab exceeds the instream water quality standard.The analytical method used by SCC's lab detects <br /> both dissolved sulfides and acid-soluble metallic sulfides that are present in suspended matter and <br /> provides a single cumulative concentration that includes both the ionized (HS-) and un-ionized forms of <br /> hydrogen sulfide (HzS).The un-ionized hydrogen sulfide is the potentially toxic form that the instream <br /> water quality standard was established for. Calculations of the un-ionized HzS indicate that the alkaline <br /> surface water at this location will not result in un-ionized HzS above the water quality standard when the <br /> sulfide concentrations are less than or equal to 0.02 mg/L. None of the samples collected from the <br /> stream points exceed the 0.02 mg/L concentration.There have also been no excursions of the NPDES <br /> discharge limits during this period at Outfalls 009 and 015 which discharge to Sage Creek. <br /> C.) Permit Requirements of the Colorado Department of Public Health & Environment(CDPHE) <br /> The six Seneca II West Mine NPDES outfalls located within the Phase-III request area are permitted <br /> under CPDS Permit No. CO-0000221. Outfalls 006, 016, and 017 discharge to unnamed tributaries to the <br /> Hubberson Gulch, Outfall 005 discharges to an unnamed tributary to Dry Creek, and Outfalls 009 and <br /> 015 discharge to unnamed tributaries to Sage Creek. Between January 1, 2015 and December 31, 2019 <br /> there was only a single exceedance of the NPDES limits at these six outfalls (Tables 7—12).Total <br /> recoverable iron exceeded the monthly average limit at Outfall 005 in April 2016.The NPDES permits <br /> monthly average limit is based on the 1 mg/L chronic total recoverable iron table value standard. <br /> However, a temporary modification of the chronic total recoverable iron standard is in place for Dry <br /> Creek segment 13d and was recently extended by the Colorado Water Quality Control Commission until <br />
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