MEMORANDUM 

TO: Steam Electric Rulemaking Record 

FROM: Elizabeth Gentile, ERG 

DATE: September 30, 2015 

SUBJECT: Bottom Ash Complete Recycle – Estimated Cost for Plants with Remote 

Mechanical Drag Systems to Implement Complete Recycle of Bottom Ash 

Transport Water 

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

Water, Engineering and Analysis Division for development of effluent limitations guidelines and 

standards (ELGs) for the Steam Electric Power Generating Industry. 

As described in EPA’s Incremental Costs and Pollutant Removals for the Final Effluent 

Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source 

Category Report (Cost and Loads Report, DCN SE05831/SE05832), EPA calculated plantspecific incremental compliance cost estimates associated with zero discharge of bottom ash 

transport water. For those plants that announced plans to convert to dry handling bottom ash 

systems in the Questionnaire for the Steam Electric Power Generating Effluent Guidelines

(“Steam Electric Survey;” DCN SE05903) or in separate company announcements1

, EPA 

estimated that the plants would not incur costs to comply with an ELG requirement for zero 

discharge of pollutants in bottom ash transport water. Although the assumption that plants 

announcing planned conversions of their bottom ash systems is reasonable, EPA nonetheless 

evaluated what additional costs may be incurred if the plants were to actually convert their 

bottom ash handling system to a remote mechanical drag system remote MDS that discharges to 

surface water, or similar system that results in a discharge to surface water. Thus, this 

memorandum presents information on the estimated cost to implement complete recycle of 

bottom ash transport water for plants that operate or plan to install remote MDS systems that are 

not known to already be closed-loop systems. 

EPA identified plants that have announced plans to convert their bottom ash handling systems, 

independent of any new ELG requirements, using two key sources of information. 

1. EPA’s Steam Electric Survey performed a census of all coal-fired plants in the U.S. As 

part of the survey, EPA asked each plant the following question (Question C3-19): “If 

the current bottom ash handling operations for the steam electric generating unit are 

expected to significantly change by December 31, 2020, indicate how (i.e., convert to or 

add dry handling capability). [Check all boxes that apply.]” For those plants responding 

that they intend to “End use of wet bottom ash handling system,” EPA estimated that the 

 

1

 See “Changes to Industry Profile for Steam Electric Generating Units for the Steam Electric Effluent Guidelines 

Final Rule” (“Industry Profile Changes memorandum;” DCN SE05069) 
Memorandum 

September 30, 2015 

Page 2 

affected generating units would not incur costs for the ELG. This is a reasonable 

approach because the response specifically states that the plant will end the use of the 

wet bottom ash handling system and, as a result, in the absence of a wet ash handling 

system the plant will not generate bottom ash transport water. These bottom ash 

conversions identified in the Steam Electric Survey were incorporated into the 

compliance cost estimates published for proposal (78 FR 34432). 

2. EPA also has information that identifies plants for which power companies have 

announced that they plan to convert the bottom ash handling practices (see the Industry 

Profile Changes memorandum).EPA’s compliance cost estimates for the ELGs assume 

that the plants will install an under-boiler MDS (or other under-boiler modification that 

eliminates generation of bottom ash transport water) or a remote MDS. Regardless of the 

specific bottom ash handling system modification that would be employed at these 

plants, EPA estimated that the plants would not incur costs to meet the zero discharge 

requirement. 

As noted above, EPA expects that the plants identified as bottom ash handling conversions in the 

Industry Profile Changes memorandum would incur zero incremental compliance costs for the 

ELG bottom ash requirements. However, EPA does not have data on the specific type of bottom 

ash handling conversion planned for the plant and it is possible that some conversions may 

include a remote MDS that is designed to discharge to surface water, rather than completely 

recycle all bottom ash transport water in a closed-loop process. If configured to discharge, the 

remote MDS would likely include additional TSS removal capability to meet the current BPT 

limits for TSS, and may accomplish this TSS removal using a clarifier. 

Because closed-loop remote MDSs have been installed at plants in recent years, and some plants 

have replaced their wet handling system with MDS or completely dry under-boiler systems that 

do not generate transport water, EPA believes few plants with planned bottom ash conversions 

would actually incur costs for the ELG. EPA nonetheless evaluated what it would cost plants to 

install and operate equipment to ensure complete recycle of the bottom ash transport water. 

Based on vendor discussions, EPA determined that for a converted system that is designed to 

discharge the transport water, such as a remote MDS and clarifier configuration, the equipment 

needed to implement complete recycle would include a surge tank, return water pumps, and 

carbon steel piping. Consistent with EPA’s cost methodology, EPA also determined that the 

additional equipment may need to include a chemical addition system, as described in Section 

8.2.4.3 of the Costs and Loads Report. Therefore, EPA estimated a potential incremental 

compliance cost associated with installing and operating this additional equipment. A description 

of EPA’s methodology and compliance cost estimates associated with these specific generating 

units is provided below. 

1.0 POPULATION OF PLANTS WITH ANNOUNCED BOTTOM ASH HANDLING CONVERSIONS

Based on the data in the Industry Profile Changes memorandum, EPA identified 39 generating 

units (corresponding to 10 plants) identified as bottom ash handling conversions after taking into 

account the implementation of the Disposal of Coal Combustion Residuals from Electric Utilities 

(CCR) rule and removing generating units at or below the 50 MW threshold. Table 1 lists the 

steam electric power plants and the number of generating units identified as bottom ash handling 

conversions in the Industry Profile Changes memorandum. 
Memorandum 

September 30, 2015 

Page 3 

Table 1. Steam Electric Power Plants with Announced Bottom Ash Handling 

Conversions 

Steam Electric Survey 

Plant ID Plant Name 

Total Number of 

Converting Units 

16 Paradise 1 

265 Kingston 9a

3597 Marshall Steam Station 4 

5065 Allen Steam Plant 3 

5570 Asheville Steam Electric Plant 2 

6257 Widows Creek 1 

6279 Gallatin 4 

6329 Cumberland 2 

6602 Shawnee 9a

9391 Roxboro Steam Plant 4 

a – EPA estimated compliance costs, described in Section 2.0, associated with these plants based on the number of 

bottom ash transport water lines at the plant, not the total number of generating units (DCN SE05969). 

Of these 39 units, EPA identified 30 generating units (corresponding to eight plants) identified as 

bottom ash handling conversions after taking into account the implementation of the CCR rule, 

the Clean Power Plan (CPP), and removing generating units at or below the 50 MW threshold. 

Table 2 lists the steam electric power plants and the number of generating units identified as 

bottom ash handling conversions in the Industry Profile Changes memorandum, accounting for 

the implementation of the CPP. 

Table 2. Steam Electric Power Plants with Announced Bottom Ash Handling 

Conversions, Accounting for CPP 

Steam Electric Survey 

Plant ID Plant Name 

Total Number of 

Converting Units 

16 Paradise 1 

265 Kingston 9a

3597 Marshall Steam Station 3 

5065 Allen Steam Plant 3 

5570 Asheville Steam Electric Plant 2 

6329 Cumberland 2 

6602 Shawnee 9a

9391 Roxboro Steam Plant 1 

a – EPA estimated compliance costs, described in Section 2.0, associated with these plants based on the number of 

bottom ash transport water lines at the plant, not the total number of generating units (DCN SE05969). 
Memorandum 

September 30, 2015 

Page 4 

2.0 METHODOLOGY FOR ESTIMATING COSTS

EPA estimated the potential incremental compliance costs associated with bottom ash handling 

generating units identified as conversions by estimating the capital and operation and 

maintenance (O&M) costs associated with additional surge tank capacity, water return pumps, 

and carbon steel piping. This equipment is required to ensure complete recycle at plants that may 

not have originally designed bottom ash remote MDS conversions for complete recycle, but 

rather discharge to surface water. 

Based on vendor data, EPA determined that the number of remote MDS installations at a plant 

depends on bottom ash transport water flow rate (in gallons per minute) and the total number of 

bottom ash transport water lines at the plant. If the number of bottom ash transport water lines at 

the plant is not available, the total number of generating units can be used for the estimate 

(assuming there is one bottom ash transport water line per generating unit). Table 3 presents a 

crosswalk for a general rule of thumb for estimating the required number of remote mechanical 

drag systems at a plant (DCN SE05970). 

Table 3. Estimated Number of Remote MDS Installations for 

Number of Generating Units 

Number of Generating Units 

Estimated Number of Remote MDS 

Installations 

1 1-2 

2 2 

3 2 

4 2-3 

5 3-4 

>5 

Dependent on Quantity of Bottom Ash 

Transport Lines 

For each set of two remote MDS installations, EPA estimates that one surge tank, one set of 

water return pumps, and carbon steel piping to return water to the boiler are required to 

completely recycle bottom ash transport water. EPA estimates that the total capital cost 

associated with this equipment is $7.5 million and that the total O&M cost is between $50,000 

and $100,000 (in 2015 dollars) (DCN SE05970). The capital and O&M costs associated with the 

chemical addition system were estimated using the same methodology described in Sections 

8.2.4.3 and 8.2.5.2 of the Cost and Loads Report, respectively. To estimate the size of chemical 

feed systems and chemical addition required, EPA used the plant-level normalized bottom ash 

sluice flow. EPA assumed one chemical addition system would be installed for each set of two 

remote MDS installations and that they would operate 365 days per year. EPA also estimated the 

total indirect capital costs associated with this additional equipment using the indirect cost factor 

described in Section 8.2.4.6 of the Cost and Loads Report. 

Therefore, for every set of two remote MDS installations identified for the plant, based on the 

number of generating units presented in Table 1 and Table 2, EPA applied the capital and O&M 

costs stated above. As a conservative approach, EPA estimated the total costs at plants identified 
Memorandum 

September 30, 2015 

Page 5 

as requiring three remote MDS installations by assuming two sets of the additional equipment 

would be installed. 

3.0 RESULTS

Based on the population of plants presented in Section 1.0 and the methodology described in 

Section 2.0, EPA estimated the potential incremental compliance costs for generating units 

flagged as bottom ash handling conversions. The estimated compliance costs, compared to the 

industry-level bottom ash and Regulatory Option D compliance cost estimates, are presented 

below in Table 4. Table 5 adjusts the results shown in Table 4, taking into account 

implementation of the CPP. 

Table 4. Bottom Ash Handling Conversion Compliance Cost Estimates Compared to the 

Estimated Total Industry Compliance Costs 

Compliance Cost Capital Cost (2010$) 

O&M Cost 

(2010$) 

Bottom Ash Conversions 124,000,000 1,170,000 

Industry-Level Bottom Ash 3,460,000,000 203,000,000 

Industry-Level Regulatory Option D 5,430,000,000 326,000,000 

Table 5. Bottom Ash Handling Conversion Compliance Cost Estimates Compared to the 

Estimated Total Industry Compliance Costs, Accounting for CPP 

Compliance Cost Capital Cost (2010$) 

O&M Cost 

(2010$) 

Bottom Ash Conversions 76,200,000 717,000 

Industry-Level Bottom Ash 2,520,000,000 133,000,000 

Industry-Level Regulatory Option D 4,160,000,000 235,000,000 

As shown in Table 4, the estimated capital costs associated with the bottom ash handling 

conversion generating units are less than four percent of the bottom ash industry capital costs and 

less than three percent of the Regulatory Option D capital costs. Table 5, accounting for CPP, 

shows that the estimated capital costs associated with the bottom ash handling conversion 

generating units are less than four percent of the bottom ash industry capital costs and less than 

two percent of the Regulatory Option D capital costs. Further, O&M costs are less than one 

percent of both the bottom ash and Regulatory Option D O&M costs. EPA does not expect 

generating units identified as bottom ash handling conversions to incur incremental compliance 

costs; however, if they do it would be a small percentage of the total industry costs and therefore 

would not change EPA’s determination that the ELGs are economically achievable. 

Additionally, EPA expects that these are the maximum costs incurred and may be reduced by the 

elimination of the clarifier, which is required for discharge but not required for complete recycle. 

For the plant-level cost estimates, see the calculation file for estimating costs associated with 

implementing complete recycle at plants with remote MDS installations (DCN SE05969).