2009-03-06_PERMIT FILE - C1981012A ‎(6)‎

• Permit No: C1981012A
• IBM Index Class Name: Permit File
• Doc Date: 3/6/2009
• Section_Exhibit Name: Exhibit 22 NPDES Permit
• Media Type: D
• Archive: Yes

CO-0000906
New Elk Mine Water Quality Assessment
Table A-2b
In-stream Standards for Stream Segment COARLA06
Physical, and Biological
Dissolved Oxygen (DO)= 6mg/1minimum (7 mg/l, minimum during spawning)
,
pH=6.5-9su
E. coli chronic = 126 colonies/100 ml
Inorganic
Free Cyanide acute = 0.2 mg/1
Boron chronic = 0.75 mg/l
Nitrite acute = 10 mg/I
Nitrate acute =100 mg/I
Metals
Total Recoverable Arsenic chronic = 100 µg/l
Total Recoverable Beryllium chronic = 100 µg/1
Total Recoverable Cadmium chronic = 10 µg/l
Total Recoverable Trivalent Chromium chronic = 100 µg/l
Total Recoverable Hexavalent Chromium chronic = 100 µg/1
Total Recoverable Copper chronic = 200 µg/l
Total Recoverable Lead chronic = 100 µg/1
Total Recoverable Nickel chronic = 200 µg/l
Total Recoverable Selenium chronic = 20 µg/l
Total Recoverable Selenium chronic = 21.3 µg/l (Temp. Std. expired 12/31/2012)
Total Recoverable Zinc chronic = 2000 µg/1
the arsenic standard of 0.02
For chronic total recoverable arsenic on stream segment COARLA05a,
µg/1 applies at the point of intake to a water supply. Because there are no downstream water supplies
on this segment, the chronic total recoverable arsenic standard for water supplies is not applied.
Instead, the agricultural standard for total recoverable arsenic of 100 µg/1 will apply, based on the
Regulation 31.
The chronic dissolved manganese, chronic dissolved iron, and sulfate standards set out for stream
segment COARLA05a in the regulations are specified as WS, which stands for water supply, and the
regulations intend for these standards to only be applicable in cases where there is a water supply in
existing use on the stream segment downstream from the facility discharge location. Although water
supply intakes are located on tributaries to the facility's receiving stream, the downstream waters
below the facility discharge point are not actively used water supplies and therefore the standards for
these parameters do not apply. However, it should be noted that the chronic manganese standard
based on Table Value Standards (TVS) does apply, as it is not dependent upon water supply use.
Standards for metals for stream segment COARLA05a are shown in the regulations as Table Value
Standards (TVS), and these often must be derived from equations that depend on the receiving
• stream hardness or species of fish present; for ammonia, standards are discussed further in
Appendix A (WQA Version 5-4(FABL)) Page 6 of 29 Last Revised August 26, 2008