PERMFILE105530

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: Exhibit 44 NPDES Permit No. CO-0042161
• Media Type: D
• Archive: No

Twentymile Coal Company Water Quality Assessment 000042161
Steamboat Springs) was evaluated for the 1955 through 1972 POR and a more recent POR. Based
• on this evaluation, the older POR data at the Yampa River was comparable to the more recent POR
data. Thus, the low flows calculated based on the older data from USGS gage station 09244100 are
considered to be representative of current low flows.
•

Table A-0
Existing Quality for Site ]6 in Fish Creek
~~ Parameter "°

`' Number
of ;

Samples ~ ~ 1 Sth ' ~
Percentile

' ~ 50th
Percentile ~_ ~ 85th. ~ :
Percentile
z- Mean :~=- ° Ch~~onic ~
Stream.~~
m.>
Standard ::Notes:
• < :_. ~.;
=
;g=
Sulfate (mg/1) 27 89 132 170 154 NA
Iron, Trec (ug/1) 30 580 1105 4600 2175 1000
Cd, Trec (ug/1) 23 0 0 0 0.026 3.4 1, 2
Mn, Trec (ug/1) 23 55 78 143 106 3105 2
Ag, Trec (ug/1) 23 0 0 0 0 0.81 1, 2, 3
Zn, Trec (ug/1) 23 3.0 20 37 23 343 1, 2
Hg, Trec (ug/1) 25 ND ND ND ND 0.01 1, 3
Se, Trec (ug/1) 23 0 0 0 0.22 5.0 1, 2
TDS (mg/1) 30 274 420 543 402 NA
TSS (mg/1) 30 13 38 188 85 NA
NH, (mg/1) 24 0 0.015 0.070 0.031 NA 1
Note I: When sample results wtte not detected, the value of zero was substituted in accordance with the WQCD's sandard approach for
summarization and avenging.
Note 2: Corrtparison of tool recoverable metals data to in-stream dissolved meals sundards were conducted because of the absrnce of a total
recoverable in-stream standard.
Note 3: For Ag and Hg, data were found at less than detection levels but the detection Itvel was greattt than the in-stream standard. Thus, in
accordance with WQCD's standard approach, no in-stream water qualiry assessment was performed.
During the months of February, April, and November, the acute low flow calculated by DFLOW
exceeded the chronic low flow. In accordance with WQCD procedures, the acute low flow was thus
set equal to the chronic low flow for these months.
IV. Technical Analysis
Appendix A Page 6 of 12