Draft NPDES General Permit for Discharges from Data Centers: Ohio Environmental Protection Agency Announces Issuance

The Ohio Environmental Protection Agency (“OEPA”) has public noticed a document titled:

Draft NPDES General Permit for Discharges from Data Center Facilities to State Waters (“Draft General Permit”).

See Public Notice No. 215991.

The document is a draft Clean Water Act General National Pollutant Discharge Elimination System (“NPDES”) Permit for statewide regulation of data center discharges.

A Clean Water Act NPDES individual permit is written to reflect site-specific conditions or a single discharger based on information submitted by that discharger in a permit application. It is unique to that discharger.

In contrast, an NPDES General Permit is written to cover multiple dischargers with similar operations and types of discharges. They are written based on the permit writer’s professional knowledge of those types of activities and discharges.

Individual permits are issued directly to an individual discharger but in the case of a general permit, it is issued with no particular facility in mind. In other words, multiple dischargers can obtain coverage under that general permit after it is issued, if consistent with the permit eligibility and authorization provisions.

Dischargers covered under general permits are informed of their applicable requirements before obtaining coverage under that permit. As a result, obtaining coverage under a general permit is typically faster than an individual permit with coverage under a general permit often occurring immediately.

The OEPA draft general permit for data centers covers facility operations that discharge to waters of the state. Both wastewater and stormwater from the data center facility are proposed for coverage under this permit.

Wastewater discharges are stated to include non-contact cooling waters (once through or re-circulated water that does not come into contact with the process operations of a facility and is used only to convey heat from the facility), low volume wastewaters (such as, cooling tower blowdown, boiler blowdown, and air compressor condensate yet excludes some waste streams like sanitary wastes) and stormwater associated with the industrial activities from the site.

Parameters addressed in the permit include:

• pH.
• Total filterable residue (i.e., Total Dissolved Solids).
• Residual chlorine.
• Residual Oxidants.

Key parameters monitored in the draft data center general permit include:

• Flow volume.
• Oil and grease.
• Temperature.

A data center facility is defined by the general permit as including an establishment that provides computer processing and data preparation services, housing computing equipment that stores, processes, and distributes digital data. They are generally indicated to be defined by standard industrial classification code 7374-data processing and preparation.

OEPA notes that data centers can use a variety of cooling systems for the purpose of removing unwanted heat. These may include:

• Air-cooled condensers.
• Water-cooled condensers.
• Evaporative cooling or a hybrid condenser with both air- and water-cooled modes.
• Liquid-based cooling that uses coolants such as water or refrigerants.

Activities exposed to stormwater are described by OEPA as including:

• Generators.
• Fuel and chemical storage tanks.
• Outdoor equipment storage.
• Material loading/unloading areas.
• Other operations where stormwater runoff may discharge pollutants.

A copy of the OPEA draft general permit can be found here.