Section 440.42 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT)Except as provided in subpart L of this part and 40 CFR 125.30 through 125.32 , any existing point source subject to this subpart must achieve the following effluent limitations representing the degree of effluent reduction attainable after application of the best practicable control technology currently available (BPT):
(a) The concentration of pollutants discharged in mine drainage from mines, either open-pit or underground, operated for the production of mercury ores shall not exceed the following limitations:| Effluent characteristic | Effluent limitations |
| Maximum for any 1 day | Average of daily values for 30 consecutive days |
| Milligrams per liter |
| TSS | 30 | 20 |
| Hg | .002 | .001 |
| Ni | .2 | .1 |
| pH | (1) | (1) |
1 Within the range 6.0 to 9.0.
(b)(1) Except as provided in paragraph (b) of this section, there shall be no discharge of process wastewater to navigable waters from mills beneficiating mercury ores by gravity separation methods or by froth flotation methods. The Agency recognizes that the elimination of the discharge of pollutants to navigable waters may result in an increase in discharges of some pollutants to other media. The Agency has considered these impacts and has addressed them in the preamble published on December 3, 1982.(2) In the event that the annual precipitation falling on the treatment facility and the drainage area contributing surface runoff to the treatment facility exceeds the annual evaporation, a volume of water equivalent to the difference between annual precipitation falling on the treatment facility and the drainage area contributing surface runoff to the treatment facility and annual evaporation may be discharged subject to the limitations set forth in paragraph (a)(1) of this section.