Illinois Administrative Code
Title 35 - ENVIRONMENTAL PROTECTION
Part 352 - PROCEDURES FOR DETERMINING WATER QUALITY BASED PERMIT LIMITATIONS FOR NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM DISCHARGERS TO THE LAKE MICHIGAN BASIN
Subpart D - ASSESSMENT OF REASONABLE POTENTIAL TO EXCEED WATER QUALITY STANDARDS, CRITERIA, AND VALUES
Section 352.410 - Data Requirements
Current through Register Vol. 48, No. 38, September 20, 2024
For a particular application, reasonable potential analysis is primarily based on the effluent quality demonstrated by self-monitoring data, as required by the NPDES permit, or Agency-generated data, such as effluent sampling, facility-related stream studies, or whole effluent toxicity (WET) testing. Effluent data used in derivation of Projected Effluent Quality (PEQ) shall be selected to best represent the concentration and variability of the pollutant in the discharge anticipated for the applicable period of the NPDES permit. Data shall be collected and analyzed in accordance with USEPA or Agency approved sampling and analytical methods. The following criteria will be followed in data selection:
a) The most recent five years of data shall be used unless the Agency determines that an alternative period better represents the time period for which effluent quality is being projected. Such alternative time periods may include but are not limited to shorter periods that reflect changed discharge characteristics resulting from changes in manufacturing activities or wastewater treatment systems.
b) Data outliers and other anomalies resulting from collection, analysis or recording errors or non-repeatable plant operation or discharge conditions may be eliminated from the data.
