Reservoir and Lake Thermal Studies and Modeling

Recent updates to Sections 316(a) and 316(b) of the Clean Water Act regulate the use and operation of cooling water intake structures and revised national effluent limitation guidelines, significantly impacting many factory and power plant operators. The use of cooling water involves significant regulatory hurdles to address aquatic environmental impacts caused by thermal discharges and the impingement and entrainment of fish and shellfish at water intake structures.

Geosyntec offers years of experience to support factory and plant operators with successful environmental permitting and compliance services, especially related to Section 316(a) and (b) compliance. While Section 316(a) addresses the thermal discharges of point sources, Section 316(b) applies to the cooling water intake structures. Although often evaluated independently during the National Pollutant Discharge Elimination System (NPDES) permitting process, the interplay between thermal discharge and cooling water withdrawal permit limits can result in complex compliance issues for existing facilities.

Notably, Section 316(a) provides that the U.S. Environmental Protection Agency (EPA) and delegated state agencies may authorize alternate thermal conditions in NPDES permits where the effluent limitation is 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 thermal discharge is made. The U.S. EPA's regulations and guidance provide a broad for framework for developing the studies and data necessary to demonstrate that the alternative effluent limit is justified.

To guide clients through this regulatory framework, Geosyntec's scientists and engineers provide compliance strategy support through the management and integration of multidisciplinary studies and study plan development. We provide peer review of data collection plans; prepare early data submittals; conduct studies of fisheries, aquatic invertebrate, and water quality; and delineate areas of influence delineation using acoustic Doppler technology. We also employ computational fluid dynamics modeling to examine cooling water intake and discharge flows.

In just one example of our services, Geosyntec performed a re-verification study for SCANA Services, Inc., and SCE&G's Williams Station, a steam electric station discharging to a tidal river. We developed a limited study plan, scaled to provide only the direct information necessary to re-verify the conditions upon which the existing 316(a) thermal variance was based without being a full-fledged 316(a) demonstration study, which would have been much more costly.

The study plan has since been circulated inside EPA Region 4 as model for other facilities pursuing renewals of 316(a) thermal variances. Geosyntec implemented thermal plume monitoring, aquatic biological sampling, and reporting, which found no evidence of prior appreciable harm to a balanced indigenous population and supported continuation of the existing thermal variance.

In addition, for Georgia Power's Plant Branch, Geosyntec prepared and implemented a study plan incorporating an innovative study approach that integrated contemporary multi-metric bioassessment methods with more traditional 316(a) demonstration guidance. This provided for a structurally definitive decision-making process, which was otherwise lacking, for assessing biological community impacts. The results of our studies met prior performance standards, demonstrating the presence of a balanced indigenous biological community in the thermal discharge area.

 

Lead Consultants

  • Robert Annear, Ph.D., P.E.
    Robert Annear is a Senior Principal Water Resources Engineer based in Oregon with more than 18 years of experience focused on the development and calibration of hydrodynamic and water quality model ...
  • Steve Layman, Ph.D.
    Steven Layman is a Principal Environmental Scientist based in Georgia with more than 25 years of experience focused on the characterization, assessment, and mitigation of impacts to water resources ...
Geosyntec Consultants
Geosyntec is a specialized consulting and engineering firm that works with private and public sector clients to address new ventures and complex problems involving our environment, natural resources, and civil infrastructure.

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