POWER PLANT THERMAL DISCHARGE AND UNIONID MUSSEL STUDIES
Dayton Power & Light Company
EA conducted a thermal discharge study for Dayton Power & Light Company’s J.M. Stuart Station in Aberdeen, Ohio. The NPDES permit for the Stuart Station required that a thermal study be conducted “to evaluate the technical feasibility and economic reasonableness of methods other than cooling towers for reducing the temperature of the mixing zone in the Ohio River resulting from the discharge from Outfalls 001 and 002.”
The overall objective of the thermal discharge study was to examine whether any cost effective, technically feasible alternatives could be applied to the existing discharge to the Ohio River that would benefit the resident aquatic community. To meet this objective, a number of alternative discharge scenarios were identified, modeled, assessed for impacts to aquatic life, and then evaluated for engineering feasibility/cost.
The study included:
- Compilation of representative J.M. Stuart Station (10 years) and historic Ohio River data.
- Examination of historic temperature plume data for the facility and evaluation of its applicability to current conditions.
- Evaluation of two- and three-dimensional hydrodynamic models for applicability to the thermal program.
- Development of a three-dimensional thermal model for evaluating discharges to the Ohio River under alternate scenarios. The Environmental Fluid Dynamics Computer Code Model was used for the instream thermal modeling.
- Development of five alternate scenarios for thermal modeling and feasibility analysis. These included the existing condition and four submerged offshore discharge locations.
- Prediction of relative thermal effects on the biological community for each alternative discharge scenario.
- Engineering feasibility study that evaluated the effectiveness, implementability, and cost for each of the alternatives.
- Costing of the alternatives included engineering design, pump station and pipeline construction, administration and management, regulatory permitting and other institutional requirements, and long-term operation and maintenance costs.
The thermal project was completed in 2006 and submitted to Ohio EPA as part of the facility’s NPDES compliance documentation.
EA’s Stuart Station work also included conducting a freshwater Unionid mussel survey to assess the existing biological condition of areas that may need to be dredged as part of an expanded barge loading area. A total of 55 live individuals comprising 5 species were collected during the survey, none of which were federally or state (Kentucky) listed threatened or endangered species. These specimens were later relocated to another area along the river. The mussel study was also conducted at Dayton Power & Light Company’s Killen Station.