HYDRO28488

• Permit No: C1981041
• IBM Index Class Name: Hydrology
• Doc Date: 9/15/2004
• Doc Name: Amendment No. 1 to CDPS Permit No. CO-0027146
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

Snowcap Coal Co. Inc WWTF Water Quality Assessment CO-0027146
Industrial processes at this facility would not generate hexavalent chromium and therefore the
evaluation for chomium is limited to the trivalent form.
Using the mass-balance equation provided in the beginning of Section IV, the low flows provided in
Section III, the background concentrations contained in Section II, and the in-stream standards for
metals shown in Section II, assimilative capacities were calculated. The data used and the resulting
calculations of the allowable discharge concentrations, Mz, are set forth in Table A-6 for chronic
assimilative capacities and in Table A-7 for acute assimilative capacities.
Table A-6
Chronic Assimilative Ca acities for Metals
Xvcm*'Y D v ~ r 1. '
O/;'QmCt 1~' ~ P~ 4+
Q ~~CfS~ n
`~~ Z~ 6~~5 .w. r~~rm-~r~,"F
~ 3~~C.~~J kYr~ 9aM .c
3,.1'1 "- , at
r r.:;_3t ,r. ' 1 $- -a,•
bM~~ ,s~. rSK';
~IYOteS~
Cd, Dis ug/1) 235 0.91 235.91 0.39 4.5 1,066 1
Cu, Dis (ug/1) 235 0.91 235.91 9.1 20 2,835 1
Fe, Dis (ug/1) 235 0.91 235.91 20 300 72,608
Fe, Trec ug/1) 235 0.91 235.91 695 1000 79,764 1
Pb, Dis (ugJl) 235 0.91 235.91 4.8 6.9 549 1
Mn, Dis ug/1) 235 0.91 235.91 15 50 9,088
Hg, Tot (ug/1) 235 0.91 235.91 0 0.010 2.6 2
Ni, Dis (ug/1) 235 0.91 235.91 0 116 30,072 3
Se, Dis (ug/1) 235 0.91 235.91 1.0 4.6 934
Ag, Dis (ug/1) 235 0.91 235.91 0 1.6 415
Zn, Dis (ug/1) 235 0.91 235.91 85 263 46,230 1
Note 1: Only limited ambient background data were available for dissolved cadmium, dissolved copper, total recoverable iron, dissolved lead
and dissolved zinc. However, alrtgst 50 samples for these metals in total foan were available. in order to use a broader base of data and
provide a conservative level of evaluation, the total metals data were used in this evaluation for the aforementioned parameters.
Note 2: Current data were available for rotal mercury but were found at values of less than detectable levels based on a detection ]evel of 0.2
up/I. Consistent with the WQCD's standard approach for summarization and averaging, a value of zero is used when sample results are found at
less than detection levels and thus a concentration of zero was used ro establish the background concentration for total mercury.
Note 3: No torten[ data were available for dissolved nickel. Findings of wmparable studies suggest [ha[ pollutants consistently found at I
than detection levers in-stream are deleted as pollutants of concem for a water body and are no knger analyzed when in-stream sampling
performed. Thus, it has bern assumed that dissolved nickel has been elirtdna[ed as a pollutant of concem in the receiving stream Based on thi
assumption, a background concentratlon of zero was used for dissolved nickel.
J
Appendix A Page 10 of 12 last Revised 9/15/2003