by Michael P. Murphy

The Illinois Pollution Control Board issued a ruling on November 4, 2021, which, if approved by the United States Environmental Protection Agency (USEPA), will become the first time-limited water quality standard (TLWQS) in Illinois. The TLWQS represents a variance from the applicable water quality standard for chloride and only applies to two watersheds in the Chicago area: the Chicago Area Waterway System (CAWS) and the Lower Des Plaines River (LDPR). (The Opinion and Order, which was entered on November 4, 2021, is available here.)

Summary of Ruling

The TLWQS is granted for a 15-year term, as long as the USEPA approves the TLWQS. Petitioners must implement best management practices (BMPs) and submit annual reports to show progress toward compliance. They are also required to participate in a chloride workgroup. The TLWQS requirements will be applied initially through a blanket general permit and then incorporated into NPDES permits as they come up for modification or renewal.

Significant Board Findings

Individual Pollution Minimization Program (PMP)

The Board agreed with the USEPA that “each discharger must provide a PMP expected to achieve the greatest achievable chloride reduction.” Opinion and Order, p. 27. The Board found that PMPs must be made public, but it rejected the argument that each PMP should be subject to additional public comment. Id.


“The BMPs represent the actions that each individual petitioner must undertake to help the watershed get closer to the goal of achieving the chloride WQS [water quality standard].” Opinion and Order, p. 27. Fifteen BMPs apply to all dischargers, including industrial dischargers. Id. at 28. The Board ruled that one BMP required for all petitioners is participation in a chloride workgroup. Although some Petitioners argued that the Board lacked authority to require participation in a workgroup, the Board ruled that it does have that authority and found that mandatory participation in the workgroup is necessary to ensure progress under the TLWQS. Id. at 32. The Board declined, however, “to rigidly dictate” how the workgroups will function. Id. at 33. The Board also found, over the objection of some Petitioners, that it was reasonable to require the workgroups to engage in education and outreach, as well as to explore financial and technical assistance. Id. at 34. The Board declined to dictate specific education and outreach and did not require any discharger to actually provide direct financial assistance; however, the workgroups must engage in these activities in order to achieve the highest attainable condition. Id. at 35. Finally, the Board found that the BMPs proposed with respect to industrial sources were appropriate, and it adopted them in Table 3 of the Opinion and Order. Id. at 40; 90.

A few of the BMPs required for industrial sources include:

  • Participate in a Chlorides workgroup for the CAWS or LDPR (depending on where the watershed for the facility’s discharge is located).
  • Implement good housekeeping practices at the site.
    • Store all salt on an impermeable pad. (The pad must be constructed to ensure minimal stormwater is coming into contact with salt unless the salt is stored in a container that ensures stormwater does not come into contact with it.)
    • Cover outdoor salt piles when not in active use.
    • Clean up salt either at the end of each day or at the conclusion of a storm event
    • Put tarps on trucks used for transporting bulk chloride
    • Use good practices while loading, unloading, and cleaning up loading and spreading equipment after each snow/ice event
    • Complete a written inspection program for the storage facility, structures, and work area
    • Calibrate all salt-spreading equipment at least annually before November 30. (Records of the calibration results must be maintained for each piece of spreading equipment.)
    • Pre-wet road salt before use. (Either apply liquids to the salt stockpile or use the spreading equipment to apply liquids as the salt is deposited on the road.)
  • Develop a written plan for implementing anti-icing. The plan must consider increased use of liquids (e.g., carbohydrate products), beginning with critical locations such as bridges over streams.
  • Before November 30 of each year, provide employees involved in winter maintenance operations with training on best management practices in the use of road salt in operations, including the practice of plowing first and applying salt only after snow has been cleared.
  • Comply with all applicable BMPs— even when de-icing practices are contracted out. Ensure that contractors are properly trained and that they comply with all applicable BMPs.
  • Complete a standardized, electronically formatted annual Report and submit it to the IEPA’s website and the watershed group.
  • Provide berms and or sufficient slope for working areas to allow snow melt and stormwater to drain away from the area. If snow melt and stormwater cannot be drained away from the working area, consider either channeling water to a collection point (such as a sump, holding tank, or lined basin) for discharge at a later time, using it for prewetting, or using it for make-up water for brine.

Opinion and Order, Table 3, pp. 90-93.

Interim Criterion

The Board set the four-year winter seasonal average for chloride concentration at 280 mg/l. (A winter season is defined as December through April.) It chose a four-year period so the data would be available in time to meet the required five-year re-evaluation. The 280 mg/l was based on the Lockport and Channahon sampling points. Opinion and Order, p. 44. The current water quality standard of 500 mg/L cannot be exceeded except in waters where mixing is allowed. Id.

Term of the TLWQS

The Board agreed that 15 years is the minimum time necessary to assess how much chloride use has been reduced by BMPs, individual PMPs, and adjustments made through re-evaluation. Opinion and Order, p. 45. Per Board rules, the TLWQS must be re-evaluated after 5 and 10 years.  Any Petitioner that does not conduct these re-evaluations will no longer be entitled to the benefit of the TLWQS. Id. at 46.

Additional Monitoring

The Board agreed with environmental groups that chloride data from two downstream locations is insufficient to assess the effectiveness of BMPs by dischargers. Opinion and Order, p. 58. Petitioner Metropolitan Water Reclamation District of Greater Chicago (MWRD) suggested that data from its existing stations would suffice for the additional monitoring. The Board agreed, rejecting the environmental groups’ requests for even more data points. Id. The Board required MWRD to collect hourly conductivity data at nine stations, collect data from 15 ambient water quality monitoring stations, derive hourly chloride estimates, and include the data in its annual report. Id. at 59.


Federal law requires that the requirements of the TLWQS be enforceable conditions of the discharger’s NPDES permit. Opinion and Order, p. 60. The Board agreed with the Illinois EPA (IEPA) that the most efficient way to incorporate the chloride standard and TLWQS requirements into NPDES permits is for the IEPA to create a general overlay permit solely designed to add the TLWQS. Opinion and Order, p. 61. When a Petitioner’s NPDES permit is later modified or renewed, the TLWQS can be incorporated into the modified or renewed NPDES permit. Id.


The Board granted the chloride TLWQS, and that Board-approved TLWQS was incorporated into and attached to the Board’s opinion and order. Opinion and Order, p. 64. IEPA must now submit the Board-approved TLWQS to the USEPA for approval, and the USEPA must approve the TLWQS before it is effective. Id. After the Board’s opinion and order is final (petitioners have 35 days to appeal or file motions to reconsider or correct) and after the USEPA approves it, the TLWQS will be the applicable water quality standard for each covered discharger for the 15-year term. Id. The requirements of the TLWQS will first be enforceable conditions through a general overlay permit and later incorporated into individual NPDES permits. Id. For the TLWQS to remain applicable, petitioners must conduct the required re-evaluations. Id. The stay of the chloride water quality standard remains in effect until the USEPA approves or disapproves the TLWQS. Id.

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