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
Table A-1 la
Department of Public
Health b Environment
Outfall 023 = 0.91 MGD
Total = 21.73 MGD
Water Quality Assessment
Therefore, the NIL values from September 30, 2000 can be used in the analysis for these outfalls. The permit
limit for total recoverable iron at outfalls 002, 011, 017, 020, 021 and 023 is the only parameter available
for a NIL. An implicit NIL must be determined for the remaining outfalls.
The permittee submitted effluent data for metals along with the permit application. For arsenic and dissolved
manganese, data prior to 2000 were not available. Arsenic data from March 2005 through December 2009
were determined to be adequate and were used to determine the implicit limitations using the highest 30 -
day average effluent concentration. Arsenic data were not available to calculate an implicit NIL for outfall
021 and 023.
For dissolved manganese, data prior to 2000 were not available. Therefore, data from March 2010 through
December 2016 were determined to be adequate and were used to determine the implicit limitations using
the highest 30 -day average effluent concentration. Dissolved manganese data were not available at outfalls
0017, 021 or 023 at the appropriate PQL to determine an implicit NIL.
For the remaining parameters, data were not available, or were not available in the appropriate form, or
with the appropriate PQL. Monitoring may be included in the permit for these parameters so that data can
be collected in order to make a determination of an implicit NIL in the future.
Table A-1 la through A-1 'If shows the results of these calculations and the determination of a new or
increased impact.
Outfall 025 is a new outfall that was not in place as of September 30, 2000, and is therefore automatically
considered a new or increased impact. The antidegradation review for outfall 025 must continue to the next
two significance tests (bioaccumulative and concentration). To evaluate these significance tests the
antidegradation limitations need to be calculated.
11
As shown in Table A -11a, there are no new or increased impacts to the receiving stream based on the new
WQBELS. The AD evaluation for these parameters is complete, and the WQBELs are the final result of this
WQA. Note that the dissolved manganese NIL for aquatic life is greater than the WQBEL calculated for the
water supply standard in Table A -8e. The water supply WQBEL will apply as it is more stringent.
Pae 30 of 40
4300 Cherry Creek Drive S., Denver, CO 80246-1530 303-692-2000 www.colorado.gov/cdphe/wqcd I ®�
Table A-1 la
Determination of New or Increased Impacts at Outfall 002 Discharge to the Yampa
River
Sept
Sept
Pollutant
2000
Permit
2000
Permit
NIL
New
New
W ABEL
New or
Limit/
Load
WQBEL
Load
Increased
Implicit
(lbs/day)(lbs/day)
Impact
NIL
Aquatic Life Parameters
Fe, TR (pg/1)
3000
177
3000
1000
8
No
Mn, Dis (Ng/l)
180
11
180
50"
0.42
No
Human Health Parameters
As, TR (pg/1)
4.1
0.24 4.1
0.13
0.014
No
varpr v innly
11
As shown in Table A -11a, there are no new or increased impacts to the receiving stream based on the new
WQBELS. The AD evaluation for these parameters is complete, and the WQBELs are the final result of this
WQA. Note that the dissolved manganese NIL for aquatic life is greater than the WQBEL calculated for the
water supply standard in Table A -8e. The water supply WQBEL will apply as it is more stringent.
Pae 30 of 40
4300 Cherry Creek Drive S., Denver, CO 80246-1530 303-692-2000 www.colorado.gov/cdphe/wqcd I ®�