Illinois EPA’s Ash Impoundment Strategy Progress Report
August 4, 2010
In response to the massive coal ash spill at a Tennessee Valley Authority facility, Illinois
EPA developed an aggressive strategy to assess ash impoundments at coal fired power
plants. Since the early 1990s, new ash ponds (surface impoundments) have been
required to be lined1 and groundwater monitoring wells have been installed at many of
these new ash impoundments. There are also older ash ponds at many of these
facilities. Review of the United States Environmental Protection Agency’s (U.S. EPA)
pre-proposal, in regard to coal combustion residues (CCR) at surface impoundments at
coal fired electric generating plants yields that their “D prime” option is very similar to
what we have been implementing.
An inventory of power plants with surface impoundments permitted by the Illinois EPA
under the National Pollutant Discharge Elimination System permit program has been
created. There are 24 power plants in Illinois with a total of 83 ash impoundments.
Table 1 below indicates the number of impoundments that are active, those that have
low permeability liners, and those that have groundwater monitoring.
83 68 15 31 28
Table 1. Number of Impoundments that are Active, have Low Permeability Liners, and
Groundwater Monitoring Systems
The geologic vulnerability of groundwater at the 24 power plants was assessed using
the Illinois’ “Potential for Aquifer Recharge” map which classifies the potential for
precipitation to infiltrate the surface and reach the water table. This map can also be
used to determine the potential for groundwater contamination on a regional scale.
Figure 1 shows the location of each power plant and the potential for aquifer recharge at
each plant. This information, along with the presence of potable wells identified near the
plants, was used to determine the potential contamination threat to those wells. The
contamination potential ranges from “very high” to “low.”
The aforementioned criteria were used to develop assessment priorities for these
facilities under an action-oriented strategic plan. The plan was finalized and
implementation began on February 26, 2009.
1 We have not required the double composite liners with leachate collection until very recently.