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Characterization of Waters
35 Ill. Adm. Code Section 302.105 (f)(1)(A) requires characterization of the water body’s physical, biological, and chemical conditions and identification of its existing uses.
The below procedures, methods, and protocols should be adequate to address these requirements for typical scenarios requiring antidegradation assessment.
The results of the waterbody characterization efforts must be included into an “Antidegradation Assessment Report” and submitted to the Illinois EPA for review. Examples of such reports are can be found on the 401 program webpage.
There are some scenarios under which the IEPA may consider a proposed activity as not requiring characterization of biological or chemical conditions of the waterbody. Two scenarios where the IEPA may deem a waterbody as having already been adequately characterized, and thereby exempt from the biological and chemical characterization requirements, are:
1. If the stream segment affected by the pollutant loading or hydrologic modification has already been assessed pursuant to IEPA’s CWA 305(b) Integrated Report. Waters can be identified using Integrated Report Companion App (Interactive Map): https://epa.illinois.gov/topics/water-quality/watershed-management/tmdls/303d-list.html
2. If the stream segment can be categorized as a 7Q1.1 zero flow stream (headwater-ephemeral) meaning it has zero flow for at least seven continuous days in nine out of ten years and there is no data indicating there is sufficient base flow to support aquatic life use. Illinois EPA considers such streams to coincide with watersheds that are less than 1 square mile in Illinois FOS regions 1 and 2, less than 3 square miles in regions 3, 4, and 5, and less than 5 square miles in regions 6 and 7. Watershed area of the furthest downstream affected area may be obtained through USGS StreamStats (https://streamstats.usgs.gov/ss/).
One other potential exemption from the characterization requirement involves short-term, temporary (i.e., weeks or months) lowering of water quality. Qualifying exemptions must provide sufficient evidence that activity will result in no permanent hydrologic modifications and that all associated pollutant loadings are minimal and temporary.
Please note that a physical characterization of the affected waterbody is necessary in all cases and in some cases characterization of chemical conditions in the receiving waters will be required.
Stream Assessments
1. Biological Characterization:
According to the Illinois EPA’s CWA 305 Integrated report, biological indicators used to determine aquatic life conditions include: the fish Index of Biological Integrity (fIBI) (Karr et al. 1986; Smogor 2000, 2005), the macroinvertebrate Index of Biological Integrity (mIBI) (Tetra Tech, Inc. 2004), and the Macroinvertebrate Biotic Index (MBI) (Illinois EPA 1994).
Below are the methods and protocols recognized by the Illinois EPA for use in proper identification and characterization of biological and chemical attributes for a defined reach in a stream.
Macroinvertebrate Sample Collection and Processing
One macroinvertebrate sample collection method (Artificial Substrate) is for collection in streams that are non-wadeable.
Another macroinvertebrate sample collection method attached is the 20-Jab method to be used in conjunction with the Standard Operating Procedure for Sample Processing for the Macroinvertebrate Index of Biotic Integrity (mIBI) protocol for wadeable streams, which is the preferred method and protocol for macroinvertebrate identification.
Fish Sample Collection and Processing
IDNR-Fisheries Stream Sampling Guidelines (2001)
2. Chemical Characterization:
Use Standard Operating Procedure for Stream Water Quality Sample Collection and Guidelines to Identify Potential Causes of Impairment of Aquatic Life Use in Streams.
(2026 Draft IIR Table C-5 Parameter List)
3. Physical Characterization
At a minimum, physical characterization of the stream is required for all individual certification requests. The appropriate Qualitative Habitat Evaluation Index (QHEI) and Use Assessment Field Sheet
Wetland Assessments
Wetland delineation is the process of identifying the boundaries of wetlands for regulatory, conservation, and land management purposes. In Illinois, this process is guided by the Corps of Engineers Wetland Delineation Manual 1987 along with the Midwest Regional Supplement. These two resources are found here:
https://www.usace.army.mil/Missions/Civil-Works/Regulatory-Program-and-Permits/reg_supp/
For impacts to jurisdictional wetlands, proper characterization in accordance with 35 Ill. Adm. Code Section 302.105 (f)(1)(A) requires completion of a combined wetland assessment using the Illinois ORAM–FQA Hybrid Scoring Sheet in accordance with the Ohio Rapid Assessment Method and Floristic Quality Assessment (FQA) using the procedure described in Plants of the Chicago Region (Swink and Wilhelm 94). The hybrid or combined assessment is designed to provide both functional and floristic quality wetland assessment necessary for compliance with Illinois EPA’s regulatory requirements.
(Illinois ORAM–FQA Hybrid Scoring Sheet)
Supporting resources:
Ohio Rapid Assessment Method (ORAM)