PERMFILE64153

• Permit No: C1980005A
• IBM Index Class Name: Permit File
• Doc Date: 6/29/2007
• Doc Name: pg 7-300 to 7-388
• Section_Exhibit Name: Tab 7 Hydrology Part 3
• Media Type: D
• Archive: Yes

Ponds 002 and 003 discharge to Grassy Creek; discharge from the Pecoco Impoundment flows to Pond
002. Pond 004 discharges to Cow Camp Creek, while Pond 008 discharges to Bond Creek; both are
tributary to Fish Creek. CDPHE has determined that beneficial uses include aquatic life and aricultural
uses. Consequently, impoundment effluent has been compared to aquatic life and agricultural
standards. Promulgated water quality criteria are presented in Regulation 31, Basic Standards for
Surface Water and Regulation 33, Classification and Numeric Standards for Upper Colorado River
Basin (Yampa River Segments 13b [Fish Creek] and 13e [Grassy Creek]).
Table 7-116, Comparison of Pond 002 and 003 Effluent Quality to Yampa Segment 14E Standards,
summarizes Pond 002 and Pond 003 effluent exceedences of the stream standards from 1999 to 2004.
The table indicates Pond 002 effluent exceeded the chronic copper standard one time out of 16
observations (06/05/01:30 micrograms per liter [pg/l] versus 29 pg/l). However, the standard is based
on the dissolved fraction and the reported value is a "total recoverable" concentration - an analytical
result which includes extractable metals lightly adsorbed on particulate matter -and, consequently,
most likely resulting in a reported value that biased high. Total iron concentrations in the effluent for
both Pond 002 and 003 (1.28 and 2.49 milligrams per liter [mg/I], respectively) exceeded the standard
(1.0 mg/l) on 04/08/03. These results indicate a very low exceedence rate (1.7 and 1.4 percent,
respectively), and are not considered significant.
The mercury standard presented in the table is the analytical method detection limit. This value (0.2 pg
/I) is greater than the than the standard (0.01 pg/I). Two samples out of 16 from Pond 002 contained
mercury concentrations (0.3 pg/I) greater than the standard. Because mercury is not typically seen in
Seneca II samples, SCC believes the observed mercury values may be biased by a sampling or
analytical artifact and not representative of Seneca II water resources. Pond 003 effluent had one
nitrite concentration (0.06 mg/I on 04/07/99) that exceeded the standard (0.05 mg/I). Hem (1989) reports
nitrates are unstable in aerated water and will quickly oxidize to nitrate. Consequently, this single
exceedence is not considered significant. Pond 003 also had a single sulfide concentration (0.003
mg/I on 04/03/01) that exceeded the standard (0.002 mg/I). Sulfide is another unstable ionic compound
and also quickly oxidizes to the more stable sulfate in aerated water (Hem, 1989). Consequently, this
single exceedence is not considered significant. Table 7-116 indicates that the effluent quality from
Pond 002 and 003 is suitable to support aquatic life and agricultural uses and will not impact water
quality in Grassy Creek.
Table 7-117, Comparison of Pond 004 and 008 Effluent Quality to Yampa Segment 14B Standards,
summarizes Pond 004 and Pond 008 effluent exceedences of the stream standards from 1999 to 2004.
Table 7-117 indicates that the effluent quality from Pond 004 and Pond 008 is suitable to support
aquatic life and agricultural uses and will not impact water quality in Fish Creek. The chronic and acute
hexavalent chromium (chromium IV) standards (11 and 16 pg/I, respectively) were exceeded one time
for Pond 004 effluent (70 pg/I on 09/20101). SCC's analytical techniques detects both the hexavalent
and trivalent species. The trivalent chromium (chromium III) chronic/acute standard (at a hardness of
400 mg/I) is 231 pg/I. Chromium VI is uncommon in aerated water, and like nitrite and sulfide, it quickly
oxidizes to the more stable chromium III. Furthermore, the chromium VI standard is based on the
TR-37 7-380 Revised 04/05