Sec. 26.08.03.03. Water Quality Impact Assessment for Thermal Discharges

A. Purpose. This regulation specifies procedures for compliance with Maryland water quality standards for thermal discharges and describes the factors, criteria, and standards for the establishment of alternate thermal effluent limitations under the Federal Act, §316(a), in permits issued under the Environment Article, Title 9, Subtitle 3, Annotated Code of Maryland, and this chapter.

B. Definition. For purposes of this regulation only, "significant" means having a statistically measurable effect beyond the mixing zone.

C. Control of Thermal Discharges.

(1) The mixing zone for thermal discharges shall be 50 feet radially from the point of discharge.

(2) The Department may establish a mixing zone of different size or shape on a case-by-case basis.

(3) Thermal discharges shall be controlled so that the:

(a) Temperature outside the applicable mixing zone meets the applicable water quality criteria specified in COMAR 26.08.02.03-3; or

(b) Discharges comply with the thermal mixing zone criteria in §D of this regulation.

(4) Request for Alternate Thermal Effluent Limitations.

(a) Dischargers who are unable to meet the requirements of either §C(3)(a) or (b) of this regulation may request alternate thermal effluent limitations as provided in §E of this regulation.

(b) A new request for alternate thermal effluent limitations shall be made within 180 days of notification by the Department that the discharger's thermal discharge cannot assure protection of a balanced indigenous community of shellfish, fish, and wildlife in and on the body of water into which the discharge is made. This request shall include a completed demonstration or a study plan for a demonstration to show compliance with §E of this regulation.

(c) A request for renewal of alternate thermal effluent limitations shall be made at the same time that the application for the renewal of the existing State discharge permit is made. This request for the renewal of existing alternate thermal effluent limitations shall include a summary of the basis for granting the alternate thermal effluent limitations and subsequent data, if any, to show that the thermal discharge effluent limitations are more stringent than necessary to protect a balanced indigenous community of shellfish, fish, and wildlife in and on the body of water into which the discharge is made. In addition, the application shall provide any other pertinent information which the Department requests within 60 days after receipt of the permit application.

(5) Alternate effluent limitations are approved only for the term of a specific State discharge permit. When renewing that State discharge permit, the discharger shall be prepared to demonstrate that continuation of the alternate effluent limitations is appropriate.

D. Thermal Mixing Zone Criteria.

(1) Requirements for Discharges to Tidal Waters.

(a) The 24-hour average of the maximum radial dimension measured from the point of discharge to the boundary of the full capacity 2°C above ambient isotherm (measured during the critical periods) may not exceed 1/2 of the average ebb tidal excursion.

(b) The 24-hour average full capacity 2°C above ambient thermal barrier (measured during the critical periods) may not exceed 50 percent of the accessible cross section of the receiving water body. Both cross sections shall be taken in the same plane.

(c) The 24-hour average area of the bottom touched by waters heated 2°C or more above ambient at full capacity (measured during the critical periods) may not exceed 5 percent of the bottom beneath the average ebb tidal excursion multiplied by the width of the receiving water body.

(2) Requirements for Discharges to Nontidal Waters.

(a) The distance downstream from the point of discharge to the 24-hour average 2°C above ambient isotherm at full capacity may not exceed the distance traveled in 6 hours by the receiving stream. Both distances shall be measured during the critical periods.

(b) The 24-hour average full capacity 2°C above ambient thermal barrier (measured during the critical periods) may not exceed 50 percent of the accessible cross section of the receiving body. Both cross sections shall be taken in the same plane.

(c) The area of the bottom touched by waters heated 2°C or more above ambient at full capacity may not exceed 5 percent of the stream bottom passed over by the stream flowing for 6 hours. Both areas shall be measured during the critical periods.

E. Establishment of Alternate Effluent Limitations.

(1) 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 to the satisfaction of the Department that the effluent limitations or standards are more stringent than necessary to assure the protection and propagation of a balanced, indigenous community of shellfish, fish, and wildlife in and on the body of water into which the discharge is made. This demonstration shall show that the alternate effluent limitation desired by the discharger, considering the cumulative impact of its thermal discharge together with all other significant impacts on the species affected, including impingement and entrainment impacts, will assure the protection and propagation of a balanced indigenous community of shellfish, fish, and wildlife in and on the body of water into which the discharge is to be made.

(2) In determining whether the protection and propagation of the affected species will be assured, the Department may consider any information contained or referenced in any applicable thermal water quality criteria and thermal water quality information published by the Environmental Protection Agency under the Federal Act, §304(a), or any other information considered relevant by the Department. The demonstration shall include evidence for the lack of the following factors:

(a) A significant increase in abundance or distribution of any species considered to be nuisance species by the Department of the Environment;

(b) A significant change in biological productivity;

(c) A significant elimination or impairment of economic and recreational resources; and

(d) A significant reduction in the successful completion of the life cycle of representative important species (RIS).

(3) Existing dischargers may base their demonstration upon the absence of prior appreciable harm instead of predictive studies. Demonstrations shall show that:

(a) Appreciable harm has not resulted from the thermal component of the discharge, taking into account the interaction of the thermal component with other pollutants and the additive effect of other thermal sources, to a balanced, indigenous community of shellfish, fish, and wildlife in and on the body of water into which the discharge has been made; or

(b) Despite the occurrence of the previous harm, the desired alternate effluent limitations, or appropriate modifications of them, will nevertheless assure the protection and propagation of a balanced, indigenous community of shellfish, fish, and wildlife in and on the body of water into which the discharge is made.

(4) In determining whether prior appreciable harm has occurred, the Department shall consider the length of time in which the applicant has been discharging and the nature of the discharge.

(5) If a discharger fails to demonstrate that existing facilities, or alternate effluent limitations together with all other impacts, will assure the protection and propagation of a balanced indigenous population of shellfish, fish, other aquatic life, or wildlife in and on the receiving water, then the discharger shall make changes in facility processes or operations, or both, sufficient to assure the protection and propagation of a balanced indigenous population of shellfish, fish, other aquatic life, or wildlife in and on the receiving water.