AECOM Environment
Upper Fox River/Flint Creek Watershed 4-4 March 2010
not result in exceeding the HPV at each meal consumption frequency. The Protocol also assumes a 50%
reduction of contaminant levels for organic chemicals (not used for mercury) when recommended cleaning and
cooking methods are used. The HPVs, target populations, critical health effects to be protected by the HPVs,
and the criteria for PCBs, mercury and chlordane for the various meal frequencies, are listed in Table C-13 (of
the 2008 Integrated Water Quality Report) as well as the FDA action levels for other contaminants.
According to Illinois water quality standards, “primary contact” means “...any recreational or other water use in
which there is prolonged and intimate contact with the water involving considerable risk of ingesting water in
quantities sufficient to pose a significant health hazard, such as swimming and water skiing” (35 Ill. Adm. Code
301.355). The assessment of primary contact use is based on fecal coliform bacteria data. The General Use
Water Quality Standard for fecal coliform bacteria specifies that during the months of May through October,
based on a minimum of five samples taken over not more than a 30-day period, fecal coliform bacteria counts
shall not exceed a geometric mean of 200/100 ml, nor shall more than 10 percent of the samples during any
30-day period exceed 400/100 ml (35 Ill. Adm. Code 302.209). This standard protects primary contact use of
Illinois waters by humans. Due to limited state resources, fecal coliform bacteria is not normally sampled at a
frequency necessary to apply the General Use standard, i.e., at least five times per month during May through
October, and very little data available from others are collected at the required frequency. Therefore,
assessment guidelines are based on application of the standard when sufficient data is available to determine
standard exceedances; but, in most cases, attainment of primary contact use is based on a broader
methodology intended to assess the likelihood that the General Use standard is being attained.
To assess primary contact use, Illinois EPA uses all fecal coliform bacteria from water samples collected in
May through October, over the most recent five-year period (i.e., 2002 through 2006 for this report). Based on
these water samples, geometric means and individual measurements of fecal coliform bacteria are compared
to the concentration thresholds in Tables C-16 and C-17 (of the 2008 Integrated Water Quality Report). To
apply the guidelines, the geometric mean of fecal coliform bacteria concentration is calculated from the entire
set of May through October water samples, across the five years. No more than 10% of all the samples may
exceed 400/100 ml for a water body to be considered Fully Supporting.
According to Illinois water quality standards, “secondary contact” means “...any recreational or other water
use in which contact with the water is either incidental or accidental and in which the probability of ingesting
appreciable quantities of water is minimal, such as fishing, commercial and recreational boating and any
limited contact incident to shoreline activity” (35 Ill. Adm. Code 301.380). Although secondary contact use is
associated with all waters of the state, no specific assessment guidelines have been developed to assess
secondary contact use because existing water quality standards have no water quality criterion that
specifically address this use. However, consistent with the meanings of these two uses, in any water where
primary contact use is assessed as Fully Supporting, secondary contact use is also assessed as Fully
Supporting. In all other circumstances secondary contact use is not assessed.
Attainment of public and food processing water supply use is assessed only in waters in which the use is
currently occurring, as evidenced by the presence of an active public-water-supply intake. The assessment of
public and food processing water supply use is based on conditions in both untreated and treated water (Table
C-21). By incorporating data through programs related to both the federal Clean Water Act and the federal
Safe Drinking Water Act, Illinois EPA believes that these guidelines provide a comprehensive assessment of
public and food processing water supply use.
Assessments of public and food processing water supply use recognize that characteristics and
concentrations of substances in Illinois surface waters can vary and that a single assessment guideline may
not protect sufficiently in all situations. Using multiple assessment guidelines helps improve the reliability of
these assessments. When applying these assessment guidelines, Illinois EPA also considers the water-quality
substance, the level of treatment available for that substance, and the monitoring frequency of that
substance in the untreated water.
