Do You Need a Thermal Variance Under Section 316(a) of the Clean Water Act, Or a Thermal Mixing Zone?
The Federal Water Pollution Control Act and West Virginia’s state counterpart (West Virginia Water Pollution Control Act) regulate discharges of pollutants to water bodies from point sources. Regulations are intended to include conditions and effluent limitations to require that any discharge of a pollutant does not cause a violation of “water quality standards.” Most people understand the concept that a contaminant (like the MHCM that was discharged by Freedom Industries) is a pollutant, and the discharge of such a contaminate is strictly regulated.
What many people may not be aware of is that an elevated discharge temperature is also considered a “pollutant” and is, like a contaminate, strictly regulated. West Virginia regulations include water quality standards that both limit the maximum temperature allowable in a stream (no more that 87 degrees Fahrenheit in the summer in most streams) and limit the temperature differential between the stream ambient temperature and the discharge temperature (typically limited to no more than a 5 degree Fahrenheit differential). Since many industrial processes, including in particular, electric power generation, discharge a significantly heated wastewater, measures to cool the effluent are often employed to ensure that temperature water quality standards are met.
From time to time however, even with the application of effluent cooling technology, effluent temperature has the potential to violate the applicable water quality standard, and dischargers must look at other opportunities to ensure compliance with water quality standards. Often, dischargers are able to comply with water quality standards when they are granted an appropriate “mixing zone” or when they have been granted a “Thermal Variance” under Section 316(a) of the Clean Water Act for such discharges. Interestingly, in West Virginia, a “thermal mixing zone” and “thermal variance” are almost, but not quite, the same.
Under West Virginia’s regulations, a mixing zone for thermal discharges may be demonstrated where:
“In the case of thermal discharges, a successful demonstration conducted under section 316(a) of the Act shall constitute compliance with all provisions of this section.” See, 47 CSR 2-5.2.i
A CWA 316(a) Thermal Variance provides:
“whenever the owner or operator … can demonstrate to the satisfaction of the Administrator(or, if appropriate, the State) that any effluent limitation proposed for the control of the thermal component of any discharge from such source will require effluent limitations more stringent than necessary to assure the protection and propagation of a balanced, indigenous population of shellfish, fish and wildlife in and on the body of water into which the discharge is to be made, the[State] may impose an effluent limitation under such sections on such plant, with respect to the thermal component of such discharge… that will assure the protection and propagation of a balanced indigenous population of shellfish, fish and wildlife in and on that body of water.”
Furthermore, Federal Regulations provide:
“Thermal discharge effluent limitations or standards established in permits may be less stringent than those required by applicable standards and limitations if the discharger demonstrates that such effluent limitations are more stringent than necessary….” See, 40 CFR part 125.73(a).
Accordingly, West Virginia’s rules appear to allow two separate, but related ways to comply with a thermal discharge that otherwise causes a violation of the temperature water quality standard. An applicant can either 1) apply for and successfully obtain (and maintain) a variance under Section 316(a) of the CWA ; Or 2) apply for and successfully obtain a site specific thermal mixing zone for its discharges.
Why does any of this matter? Because once a site specific mixing zone is approved and demonstrated, it is unlikely to be subject to significant review in the future absent changes in the nature of the stream segment or the discharge. A variance under Section 316(a) however, will, according to a WV DEP permits supervisor, require the discharger to regularly demonstrate “protection and propagation of a balanced, indigenous population” of wildlife. To be sure, both a thermal mixing zone and a thermal variance are subject to “demonstration” during the permit term, wherein a discharger must demonstrate compliance with the water quality standard rules. The rules provide that, for a mixing zone, the temperature water quality limit must be maintained at the edge of the mixing zone, OR, that the discharge satisfies the CWA section 316(a) criteria. For a Section 316 (a) thermal variance, only the criteria described above (regarding propagation of wildlife) needs to be satisfied.
Certainly a somewhat circular and complex process, but for purposes of planning, a thermal discharger should keep in mind the following process for a thermal discharge:
- The discharger should request that WVDEP evaluate a site specific “thermal mixing zone” first.
- Because the rules require that a CWA Section 316(a) variance application be filed “during the public comment period,” the applicant should file the CWA section 316(a) application with its permit comment letter, but request that the application not be acted on unless the mixing zone is demonstrated to be unsuccessful in meeting water quality standards at the edge of the mixing zone.
- In its comment letter to a draft permit, an applicant should suggest that it will first attempt to demonstrate that it meets water quality standards at the edge of mixing zone, but if unsuccessful, will demonstrate compliance with the mixing zone requirements under the rule with the CWA section 316(a) demonstration.
If the applicant follows the above described procedure, this writer believes that a strong argument can be made that a successful CWA section 316(a) demonstration simply confirms compliance with the mixing zone demonstration and is therefore not subject to future review or re-demonstration.