Ohio EPA Issues Draft General NPDES Permit for Data Centers
Given the proliferation of data center activity in Ohio, the Ohio EPA has issued a draft general permit for discharges to waters of the state from data center facility operations. The Ohio EPA is holding a public hearing and accepting comments on the draft permit through December 17, 2025. The availability of general permit coverage offers a streamlined path to permitting for those eligible facilities, making this an attractive option for data centers that otherwise would be subject to the lengthier process for pursuing individual permit coverage.
The permit covers proposed and existing data center facility operations that discharge to waters of the state. It defines “data center facility” as an establishment that provides computer processing and data preparation services, and houses computing equipment that stores, processes, and distributes digital data. This generally includes Standard Industrial Classification (SIC) Code 7374 – Data Processing and Preparation.
The draft permit covers both wastewater and stormwater discharges, including:
- Non-contact cooling waters (once through or re-circulated water that does not come into contact with the process operations of the facility and is used only to convey heat from the facility);
- Low volume wastewaters (including cooling tower blowdown, boiler blowdown, or air compressor condensate; excluding certain waste streams such as sanitary wastes); and
- Stormwater associated with industrial activities at the data center site (including generators, fuel and chemical storage tanks, outdoor equipment storage, and material loading/unloading areas).
The permit proposes limits for specific parameters, including pH, Total Filterable Residue (i.e., Total Dissolved Solids), Residual Chlorine, and Residual Oxidants. It further proposes monitoring for flow volume, oil and grease, total suspended solids, and temperature. Two monitoring tables are included within the permit, depending on whether the wastewater discharge is mixed with stormwater (outfall 001) or if stormwater is a separate outfall (outfall 002).
The draft permit is similar to other general NPDES permits in Ohio, in that:
- Once issued, it would be effective for a period of five years.
- Coverage is available throughout the entire state of Ohio.
- The application process involves the submittal of a Notice of Intent (NOI) form.
- Coverage becomes effective when the Director notifies the permittee that the discharge is authorized under the general permit.
- Discharge Monitoring Reports (DMRs) must be submitted by the 20th day of the month following the month of interest.
- Coverage is transferable, requiring 60 days advance notice.
- If the discharge is eliminated, a Notice of Termination must be submitted.
The permit lists 15 examples of specific discharges that are not authorized by the permit, which include discharges that exhibit the reasonable potential to exceed a Water Quality Standard; discharges located within 500 yards upstream of a public water supply surface water intake that cannot meet Ohio’s public water supply standards; discharges to a lake other than Lake Erie; discharges from co-located activities such as steam electric power generation facilities; discharges to combined or sanitary sewer systems or ground water; and discharges that include certain concentrations of volatile organic compounds.
In addition to accepting comments on the draft permit through December 17, 2025, the Ohio EPA is holding an in-person and virtual information session and public hearing on the draft permit on December 17, 2025, at 2:30 PM ET. Further details regarding the public hearing and how to submit comments are contained within the public notice and fact sheet.
