Through detailed analyses for two power plants, this report evaluates the use of stormwater for cooling and other uses. The report will benefit environment, generation, and planning managers within power companies, government agencies, and water resource stakeholders.
In recent years, there has been a focus on evaluating the use of nontraditional water sources for thermoelectric power plant cooling, such as reclaimed municipal wastewater, produced water from oil and gas drilling, and saline groundwater (described in EPRI report 1014935). These efforts are intended to minimize the freshwater footprint of current electricity generation and to develop alternative pathways for future generation growth in a water-constrained world. The current study was preceded by a scoping study (EPRI report 1021124) that examined stormwater generation across a range of climatic conditions, represented by 10 urban areas throughout the United States. Coupled with available data on stormwater quality from a national database, the scoping study identified treatment requirements for use in power plants. It concluded that stormwater could serve as a meaningful resource in certain power plant settings and for power plant uses with specific quality requirements, but that more site-specific analyses would be needed to consider water quality constraints; costs associated with conveyance, storage, and treatment; and discharge requirements.
This report provides guidance on assessing potential stormwater use at a generation plant by describing site-specific assessments conducted at two power plants.
Building on information obtained in the scoping study, this investigation focused on two power plants in detailed site-specific analyses. Both plants are owned by Great River Energy (GRE). The first is a 1,100-MW coal burning plant on the Missouri River in North Dakota (Coal Creek Generating Station); the second is a 37-MW refuse-derived fuel plant on the Mississippi River in Elk River, Minnesota (Elk River Energy Recovery Station). Analyses also considered a generating station with water demands similar to those of Coal Creek but placed in other climatic conditions (representing upstate New York, Illinois, and southern California). Therefore, the analyses presented pertain not only to the two plants, but also to plants with varying climatic drivers.
This report presents the methodological approach used to estimate stormwater flows, conveyance, and storage and treatment needs in a general plant setting in Section 2. A discussion of water quality and constraints related to discharge is presented in Section 3. Off-site and on-site stormwater volume estimates for the Coal Creek and Elk River stations are presented in Sections 4 and 5. The integration of stormwater flow, quality, treatment requirements, and costs is presented for Coal Creek Station in Section 6 and for Elk River Station in Section 7. Stormwater estimates and related calculations of their use for three hypothetical locations are presented in Section 8, and Section 9 presents the main findings of this study and their relevance to current and future electricity generation.
For the two GRE plants considered, significant amounts of stormwater are available from both on-site and off-site sources. Water quality at these locations is acceptable from a process perspective for a variety of uses within power plants. The 1,100-MW Coal Creek plant may integrate stormwater into its water management using the existing infrastructure, with modest additional cost. Because the plant is spread over a large area, on-site stormwater provides a significant resource for use. The 37-MW Elk River station, at its current capacity, is not a good candidate for the use of stormwater either off- or on-site. It is, however, located near storm drains that convey substantial volume. If there is an increased need for water at this location (perhaps if a larger plant were built), the use of stormwater should be explored.
Following are general findings from this analysis, beyond the results for the two GRE plants:
Existing empirical tools can be used to estimate stormwater generation through modest computational effort, and the analysis developed for this work can be readily modified for other locations in North America.
Stormwater is a steady resource in regions and seasons in which rainfall is abundant. It is not a significant resource during dry or drought periods and may be an infrequent resource in arid areas.
The presence of a variety of added constituents in stormwater, specifically metals and organics, poses a problem from a discharge standpoint because these constituents will be further concentrated in discharge.
Costs of off-site stormwater conveyance through pipelines may limit use.
Applications, Value, and Use
As freshwater resources become more constrained by existing demands and needs for environmental protection, there is significant value in evaluating what might be considered a new water resource: stormwater. Stormwater is often seen as a flooding risk and not a potential water supply, but it is in some respects similar to municipal wastewater—a source often considered for replacing freshwater supply to power plants. Both sources are largely considered waste streams and must be collected and discharged with permits into surface waters. Stormwater does differ from municipal wastewater in terms of its quality and its highly variable volume and timing.