HYDRO31322

• Permit No: C1980001
• IBM Index Class Name: Hydrology
• Doc Date: 6/6/2007
• Doc Name: Authorization to Discharge Under the Colo Discharge Permit System
• From: Department of Health Department
• To: DRMS
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

Pittsburg and Midway Coal Company Edna Mine Water Quality Assessment CO-0032638
Table A-7
Acute A
ssim
ilative C
a acities
for Metals at Outfall 007
pQY(iIl/CfBY ~,, .~ .... /
l
~~1~4~CfS/~ {
~2~~C/S~.` /
Q3'tCfS~ .•,1~'7=; .,'..; l~j ::.'. M~ ~~~~ NOtCS.
As, TR (ug/1) 0.046 4.0 4.0 1.0 50 51 1
Cd, Dis (ug/1) 0.046 4.0 4.0 0 17 17
Cr+3, Dis (ug/I) 0.046 4.0 4.0 26 1773 1,793 2
Cr+3, TR (ug/1) 0.046 4.0 4.0 11 50 SO 1,2
Cu, Dis (u 0.046 4.0 4.0 8.5 50 50
Pb, Dis (u 1) 0.046 4.0 4.0 0 281 284
Mn, Dis (ug/1) 0.046 4.0 4.0 13 4738 4,792
Ni, Dis u 1) 0.046 4.0 4.0 0 1513 1,530
Se, Dis (ug/1) 0.046 4.0 4.0 1.1 18 18
A ,Dis (ug/1) 0.046 4.0 4.0 0 22 22 3
Zn, Dis (ug/I 0.046 4.0 4.0 18 379 383
Note l: Note that these limits are effective only from June through February. Also, for As TR, see Note 1 in Table A-6.
Note 2: See Note 2 in Table A-6.
Note 3: See No[e 3 in Table A-6.
V. Antidegradation Review
As set out in The Basic Standards and Methodologies of Surface Water, Section 31.8(2)(b}, an
antidegradation analysis is required except incases where the receiving water is designated as "Use
Protected." Note that "Use Protected" waters are waters "that the Commission has determined do
not warrant the special protection provided by the outstanding waters designation or the
antidegradationreuiew process" asset out in Section 31.8(2)(b). The antidegradation section of the
regulation became effective in December 2000, and therefore antidegradation considerations are
applicable to this WQA development.
According to the Classifications and Numeric Standards for Upper Colorado River Basin and North
Platte River (Planning Region 12), stream segment COUCYA13c is Undesignated. Thus, an
antidegradation review is required for this segment ifnew or increased impacts are found to occur.
The Division's Antidegradation Significance Determination for New or Increased Water Quality
Impacts Procedural Guidance provides guidance on the determination of new or increased water
quality impacts and significant degradation.
Consistent with current Division procedures, the baseline water quality (BWQ) concentrations for
pollutants of concern should be established so that it can be used as part of antidegradation reviews.
BWQ is defined by the Division as the condition of the water quality as of September 30, 2000.
Furthermore, the Division specifies that BWQ concentration will include the influence of the
discharger if it was in place on September 30, 2000. Accordingly, BWQ concentrations are
calculated based on the following equation:
Appendix A 1wQA as version a-s FABL> Page 13 of 19 Last Revised September 2, 2005