HYDRO25625

• Permit No: C1981071
• IBM Index Class Name: Hydrology
• Doc Date: 3/17/1986
• Doc Name: DRAFT PERMIT FOR PUBLIC NOTICE
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

COLORADO DEPARTMENT OF HEALTH
Water Quality Control Division
Rationale - Page 5
Permit No. CO-•0027154
APPLICABLE RUL1sS AND REGULATIONS:
Outfalla 001, 002, 003, 004, 006, 008, 018
These outfalls serve as discharge points for surface runoff from active mining
areas. Federa:~ BPT (Beat Practicable Control Technology) and BAT (Best
Available Tectu:ology Economically Achievable) apply as do state SES (State
Effluent Standards) sad WQS (Water Quality Standards). Because discharges are
intermittent and usually in response to precipitation events, only WQS for pH
apply. A comparison is shown in Table 1 below.
TABLE 1
Parameter SES WQS BPT BAT
pH, s.u. a/ 6. 0 - 9.0 6.5 - 9.0 6.0-9.0 N/A
011 sad Grease, mg/1 a/ 10.0 N/A N/A N/A
Total Suspended Solids, mg/1 30/45 N/A 35/70 b/ N/A
Total Iron, mg/1 N/A N/A 3.5/7.0 b/ 3.5/7.0
Settleable Solids, ml/1 c/ N/A N/A N/A 0.5
a/ This parameter applicable at all times.
b/ This limitation applicable to discharges during periods of no precipitation.
c/ This parameter applicable to discharges during periods of precipitation less
than or equal to the 10-year, 24-hour event for this facility.
Outfalls 009, 010, 011. 012, 013, 015, 016, 017
These outfalls serve as discharge points for surface runoff from post-mining
areas. Federal BPT (Best Practicable Control Technology) and BAT (Best Available
Technology Economically Achievable) recently promulgated specify the following
effluent limitations for reclamation areas:
TABLE 2
Parameter
BPT BAT
pH, s.u. 6.0 to 9.0 NA
Settleable Solids, ml/1~ 0.5 0.5
°This parameter does not apply to discharges caused by precipitation greater than
the 10-year, 24-hour event (or equivalent snowmelt volume).
State Effluent Standards ($E$) dictate the imposition of an 011 and Grease
limitation of 10.0 mg/1 for all discharges not otherwise limited. Additionally,
State Water Quality Standards (WQS) dictate a pH limitation of 6.5 to 9.0 s.u.
This supresedes the BPT limitation for pH shown in Table 2.
Because discharge will be intermittent and will normally occur only during
precipitation events (periods when receiving water flows will be high) no water
quality standard-based effluent limitations are appropriate other than pH.