MEMORANDUM 

TO: Steam Electric Rulemaking Record 

FROM: TJ Finseth, ERG 

 Danielle Lewis, ERG 

DATE: April 19, 2013 

SUBJECT: Evaluation of Chemical Precipitation Costs for Ash Transport Water 

ERG is providing technical support to the U.S. Environmental Protection Agency’s Office of 

Water, Engineering and Analysis Division (EAD) for development of effluent limitations 

guidelines and standards (ELGs) for the Steam Electric Power Generating Industry. As part of 

this technical support, EPA, with support from ERG, evaluated chemical precipitation as a 

potential basis for a technology option for the treatment of fly ash transport water and bottom ash 

transport water. EPA considered including chemical precipitation as a technology basis for ash 

transport water in one or more of the proposed regulatory options (see Section 8 of the Technical 

Development Document for the Proposed Effluent Limitations Guidelines and Standards for the 

Steam Electric Power Generating Point Source Category for more details on the proposed 

regulatory options), with numeric effluent limitations or standards for discharges of fly ash 

transport water or bottom ash transport water to surface waters. Based on EPA’s analysis, 

described below, EPA found costs for chemical precipitation treatment of fly ash and bottom ash 

transport water to be comparable or higher than the cost for converting to dry handling or closed 

loop technologies. Additionally, the chemical precipitation technology removes fewer pollutants 

compared to conversion to dry handling; therefore, EPA did not include chemical precipitation 

treatment as part of the proposed regulatory options. This memorandum describes the 

methodology EPA used to estimate capital costs to install a chemical precipitation system for the 

treatment of fly ash transport water and bottom ash transport water, and a comparison of 

chemical precipitation treatment system capital costs to estimated capital costs for the dry 

handling or closed loop technologies. 

For this evaluation, EPA used the one-stage chemical precipitation cost module along with plantlevel discharge flow rates for fly ash transport water and bottom ash transport water to estimate 

plant-level capital costs to install a chemical precipitation treatment system. The one-stage 

chemical precipitation cost module, as described in the Incremental Costs and Pollutant 

Removals for the Proposed Effluent Limitations Guidelines and Standards for the Steam Electric 

Power Generating Point Source Category report (DCN SE01957), is the same cost module used 

to estimate costs associated with one-stage chemical precipitation systems used to treat flue gas 

desulfurization (FGD) wastewater. As described in Section 6.1 of the report, the one-stage 

chemical precipitation cost module estimates capital and operating and maintenance (O&M) 

costs to install and operate a one-stage chemical precipitation system specifically designed and 

operated to treat FGD wastewater. To estimate the capital costs associated with the treatment of 

ash transport water , EPA summed the capital cost output elements, including purchased 

equipment (with the exception of the equalization tank), equipment installation, buildings, site 
Memorandum 

April 19, 2013 

Page 2 

preparation, construction, and engineering costs, from the cost module for the purposes of this 

cost analysis. EPA excluded capital costs associated with equalization tanks (See Section 6.1.6.2 

of DCN SE01957) because EPA believes plants would be likely to continue operating existing 

ash settling ponds instead of installing large holding tanks for equalization. EPA used the same 

residence time and other equipment sizing bases as used to cost chemical precipitation for FGD 

wastewater. 

EPA estimated plant-level capital costs for 50 plants discharging fly ash transport water and 204 

plants discharging bottom ash transport water to treat the ash transport water with a chemical 

precipitation system. The capital costs are based on plant-level discharge flow rates for either fly 

ash transport water or bottom ash transport water. EPA used discharge flow rates from the “Ash 

Transport Water Input Table,” (See Section 4.1.2 of DCN SE01957), which is the basis for the 

ash transport water loadings calculations. Where the information was available from responses 

in the Steam Electric Survey, EPA separated flows identified as combined ash sluice into 

contributions from fly ash sluice and bottom ash sluice. Tables A-1 and A-2, included as 

attachments to this memorandum, include the plant-level discharge flow rates used to estimate 

the costs associated with a chemical precipitation treatment system for fly ash transport water 

and bottom ash transport water, respectively. Plant-level capital cost estimates were calculated 

for only those plants whose plant-level fly ash transport water flow rate or plant-level bottom ash 

transport water flow rate could be determined. While not all plants discharging ash transport 

water were included in this analysis, the results for the plants that were included is sufficient to 

inform how costs for treatment of ash transport water via chemical precipitation compares to dry 

ash handling conversions.1

For the 50 plants included in this analysis that discharge fly ash transport water, EPA estimated a 

total capital cost of $5.4 billion to install one-stage chemical precipitation systems. For the 204 

plants included in this analysis that discharge bottom ash transport water, EPA estimated a total 

capital cost of $11.8 billion to install one-stage chemical precipitation systems. Tables A-1 and 

A-2 include the plant-level cost estimates. 

EPA compared the capital costs estimated for the chemical precipitation systems to the capital 

cost estimated for the dry ash handling or closed loop ash handling system on a plant-level. 

Plant-level capital costs for dry handling or closed loop ash handling systems are included in 

Tables A-1 and A-2. For the 50 plants discharging fly ash transport water, chemical 

precipitation treatment systems capital costs are almost 22 times more expensive than dry 

handling on an industry-level. For the 204 plants discharging bottom ash transport water, 

chemical precipitation systems capital costs are almost two times more expensive than dry 

handling or closed loop systems on an industry-level. Because the costs for chemical 

precipitation treatment were found to be higher than the cost for converting to dry handling or 

closed loop technologies, for both fly ash and bottom ash, EPA chose not to include this 

treatment technology as part of the proposed regulatory options. 

 

1

 EPA estimated plant-level capital costs for 50 of the 66 plants (76%) incurring fly ash compliance costs 

(excluding oil-fired and small generating units) and 204 of the 240 plants (85%) incurring bottom ash compliance 

costs (excluding oil-fired and small generating units).