Policy & Regulations

Planning for the unintended consequences of CCR/ELG

On April 17, 2015, the Environmental Protection Agency (EPA) issued the final version of the federal Coal Combustion Residual Rule (CCR Rule) to regulate the disposal of coal combustion residual (CCR) materials generated at coal-fired units. 

By Jason Eichenberger, P.E., Burns & McDonnell, and Jim Palmer, P.E., Kansas City Power & Light

Jason Eichenberger
Jim Palmer

On April 17, 2015, the Environmental Protection Agency (EPA) issued the final version of the federal Coal Combustion Residual Rule (CCR Rule) to regulate the disposal of coal combustion residual (CCR) materials generated at coal-fired units. EPA also released the final version of the federal Effluent Limitations Guidelines and Standards (ELG Rule) on Nov. 3, 2015 to eliminate the discharge of bottom ash and fly ash transport water and place stringent limits on the discharge of flue gas desulfurization (FGD) wastewater. Over the last year, the power industry has been focused on planning and/or implementing ash handling conversions and FGD wastewater treatment systems and rightly so; however, the most challenging compliance projects will likely involve managing large volumes of plant stormwater following any ash pond closures required by the CCR Rule.

Typical power plant discharges are comprised of many streams. These categories, and average percentages of overall plant discharges, are summarized in the figure on this page. As you can see, a large portion of the total discharge is not currently regulated by ELG; however, many of the other flows are starting to be tightly regulated at the state level. Some state implemented metal limits imposed on general plant drains and stormwater outfalls in recently issued permits include mercury, aluminum, zinc, along with many others. These new limits can have significant compliance risk since the water quality in these streams can be impacted by relatively simple site activities.

Outage flows associated with plant wash down events and peak runoff from heavy storm events are the primary drivers that must be investigated when sizing a treatment system for these non-ELG regulated flows. Historically, this has not been an issue for plants that have large ash ponds. These ponds have been the heart of a plant water balance, and have provided both surge capacity and equalization of water quality for many years. Not only that, but ash sluice flows also provide a great deal of relatively clean water that has comingled with these other streams in the past. With ash sluicing flows being removed from the water balance and ash ponds closing across the country, utilities can expect much more fluctuation in their discharge water quality and flow rate. Some plants will have enough real estate to construct a new pond-based treatment system for these flows or potentially repurpose portions of their ash pond systems; however, many others are going to need alternatives that minimize footprint requirements while still accommodating large peak volumes of water.

Typical Peak Discharges
Averaged across six recent Burns & McDonnell water balance projects.

Several tank-based solutions have been designed for treatment of these flows. Some use high-rate clarifiers and polishing filter systems, while others use concrete tanks with polymer feeds to remove solids prior to combining with other outfalls. These solutions can cost 50 percent to 80 percent more than a pond-based alternative for a given flow rate; however, they require only 15 percent to 30 percent of the site footprint and can potentially be provided with manufacturer performance guarantees as well. Site specific flow rates must be determined prior to sizing these systems. When performing water balance updates for ELG compliance, plants should be taking every opportunity to measure their outage flow rates and runoff from storm events. Site specific hydrographs can help minimize some of the conservatism in typical hydrology calculations, thus limiting the total installed cost of a stormwater treatment solution.

As the EPA, and consequently the power industry, begins to focus on limiting discharges or converting to zero discharge alternatives, it will become even more critical for utilities to understand the big picture of their overall water balances. Minimizing flows will increase concentrations for many of the constituents of concern and will complicate the water treatment systems, but reducing volume will likely save a much larger portion of the cost in the long term.

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