Section 304.126  Mercury

a)         Except as provided below, a person must not cause or allow the concentration of mercury in any effluent to exceed the following level, subject to the averaging rule contained in Section 304.104(a).

b)         It is an exception to subsection (a) if all of the following conditions are met:

1)         The discharger does not use mercury; or, the discharger uses mercury and this use cannot be eliminated; or, the discharger uses mercury only in chemical analysis or in laboratory or other equipment and takes reasonable care to avoid contamination of wastewater;

2)         The effluent mercury concentration is less than 0.003 mg/L, as determined by applying the averaging rules of Section 304.104(a);

3)         The discharger is providing the best degree of treatment consistent with technological feasibility, economic reasonableness, and sound engineering judgment.  This may include no treatment for mercury; and

4)         The discharger has an inspection and maintenance program likely to reduce or prevent an increase in the level of mercury discharges.

c)         It is an exception to subsection (a) if all of the following conditions are met:

1)         The discharger is a publicly owned or publicly regulated sewage treatment works;

2)         The discharger does not use mercury; or, the discharger uses mercury only in chemical analysis or in laboratory or other equipment and takes reasonable care to avoid contamination of wastewater;

3)         The effluent mercury concentration is less than 0.003 mg/L, as determined by applying the averaging rules of Section 304.104(a); provided, however, that daily averages may exceed 0.006 mg/L 30% of the time;

4)         The discharger has enforceable ordinances or contract provisions by which it limits the use of mercury by dischargers and the discharge of mercury into its sewage system;

5)         The discharger's limitations on the use and discharge of mercury to its sewage system are at least as stringent as those provided in 35 Ill. Adm. Code 307.1102;

6)         The discharger has a surveillance program with a reasonable likelihood of determining sources of mercury discharged to the sewage system;

7)         The discharger takes all lawful steps to eliminate known mercury discharges to the sewage system that contribute to levels exceeding those allowed by 35 Ill. Adm. Code 307.1102; and

8)         The discharger reports all known violations of 35 Ill. Adm. Code 307.1102 to the Agency.

d)         When it issues a permit, the Agency may consider applying the exceptions of this Section to determine compliance with this Section. The Agency may impose permit conditions necessary or required to assure continued application of an exception.  When subsection (b) applies, the Agency may impose an effluent limitation in the permit which allows discharge of a concentration of mercury greater than 0.0005 mg/L but not more than 0.003 mg/L.

(Source:  Amended at 47 Ill. Reg. 4601, effective March 23, 2023)