Ill. Admin. Code tit. 35 § 303.410
The general use chronic water quality standard for dissolved nickel contained in 35 Ill. Adm. Code 302.208(e) does not apply to the segment of the Sangamon River that receives discharges from the Sanitary District of Decatur's Main Sewage Treatment Plant, from that facility's Outfall 001 located at 39° 49' 56" North Latitude, 89° 0' 7" West Longitude, to the point of the confluence of the Sangamon River with the South Fork of the Sangamon River near Riverton. Instead, waters in this segment of the Sangamon River must meet a chronic water quality standard for dissolved nickel as follows:
Chronic Dissolved Nickel Standard (µg/L) = exp[A+Bln(H)] x 0.997 * x WER
where:
A = -2.286,
B = 0.8460,
ln(H) = natural logarithm of Hardness, and
WER (Water Effect Ratio) = 2.50.
*conversion factor multiplier for dissolved metals
Ill. Admin. Code tit. 35, § 303.410