2018-03-01_HYDROLOGY - C1981010 ‎(2)‎

• Permit No: C1981010
• IBM Index Class Name: Hydrology
• Doc Date: 3/1/2018
• Doc Name: CDPS/NPDES Permit
• From: Department of Public Health & Environment
• To: DRMS
• Permit Index Doc Type: NPDES
• Email Name: RAR
• Media Type: D
• Archive: No

COLORADO
Water Quality Assessment
Department of Public
•�' �' Health b Environment
insignificant level is the ADBAC calculated in Table 16. If the new WQBEL concentration is greater than the
ADBAC, an AD limit would be applied. This comparison is shown in Table 17.
Table A-17
Concentration Significance Test Outfall 025
Pollutant
New WQBEL
ADBAC
Concentration Test Result
Aquatic Life Parameters
As, Dis (pg/1)
340
51
Significant
Cd, Dis (pg/l)
0.5
0.075
Significant
Cr+3, Dis (Ng/t)
88
13
Significant
Cu, Dis (pg/1)
11
6.8
Significant
Fe, TR (pg/1)
1000
150
Significant
Pb, Dis (pg/1)
3.2
0.56
Significant
Mn, Dis (pg/1)
1772
285
Significant
Hg, Tot (pg/1)
0.01
0.0015
Significant
Ni, Dis (Ng/l)
62
10
Significant
Se, Dis (Ng/t)
4.6
1.3
Significant
Ag, Dis (Ng/l)
0.46
0.069
Significant
Zn, Dis (Ng/l)
147
25
Significant
Human Health Parameters
As, TR (Ng/l)
0.13
0.7
Insignificant
Cr+3, TR (pg/1)
225
529
Insignificant
Hg, Tot (Ng/l)
0.067
0.053
Significant
Antidegradation Based Effluent Limitations (ADBELs)
The ADBEL is defined as the potential limitation resulting from the AD evaluation, and may be either the
ADBAC, the NIL, or may be based on the concentration associated with the threshold load concentration (for
the bioaccumulative toxic pollutants). ADBACs, NILS and TLs have already been determined in the AD
evaluation, and therefore to complete the evaluation, a final comparison of limitations needs to be
completed.
Note that ADBACs and NILS are not applicable when the new WQBEL concentration (and loading as evaluated
in the New and Increased Impacts Test) is less than the NIL concentration (and loading), or when the new
WQBEL is less than the ADBAC.
Where an ADBAC or NIL applies, the permittee has the final choice between the two limitations. A NIL is
applied as a 30 -day average (and the acute WQBEL would also apply where applicable) while the ADBAC
would be applied as a 2 year rolling average concentration. For the purposes of this WQA, the Division has
made an attempt to determine whether the NIL or ADBAC will apply. The end results of this AD evaluation
are in Table A -18a through A -18f, including any parameter that was previously exempted from further AD
evaluation, with the final potential limitation identified (NIL, WQBEL or ADBAC).
Paine 37 of 40
4300 Cherry Creek Drive 5., Denver, CO 80246-1530 303-692-2000 www.cotorado.gov/cdphe/wqcd ��