### MEMORANDUM

TO: Steam Electric Rulemaking Record

FROM: TJ Finseth, ERG

DATE: 19 April 2013

SUBJECT: Evaluation of Generating Capacity Thresholds for FGD Wastewater and Bottom Ash Transport Water

ERG is providing technical support to the U.S. Environmental Protection Agency’s Office of Water, Engineering and Analysis Division (E AD) for development of effluent limitations guidelines and standards (ELGs) for the Steam Electric Power Generati ng Industry. EPA, with the support of ERG, evaluated wa stewater flow rates and pollut ant concentration data from survey responses, site visits, sampling episodes, trade associations, i ndividual power plants, states, and previous rulemakings to estimate pollu tant discharge loadings associated with the discharge of FGD wastewater, fly ash transport water, botto m ash transport water, and
combustion residual landfill leachate. In addi tion, EPA estimated the corresponding pollutant removals associated with installing and operating the proposed ca ndidate BAT technology options for each of these wastestreams.

As described in Section 8.1.3.1 of the Technical Development Document for the Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (TDD), EPA is proposing to establish BAT limits equal to BPT for existing oilfired units. Additionally, as de scribed in Section 8.1.3.2 of the T DD, EPA is also proposing to establish BAT effluent limits equal to BPT for existing generating units with a total nameplate generating capacity of 50 MW or less. EPA is proposing to establish these BAT limits for all eight of the regulatory options described in Section 8 of the TDD; however, for regulatory Options 3b and 4a, EPA is proposing to use a different capacity threshold for certain

wastestreams.

For Regulatory Option 3b, EPA is proposing to es tablish numeric effluent limits for mercury, arsenic, selenium, and nitrate- nitrite in discharges of FGD wastewater from steam electric facilities with a total plant-level wet- scrubbed capacity of 2,000 MW or greater. 1 As part of the analysis, EPA also evaluated other plant-leve l wet-scrubbed capacity thresholds. Table 1 presents the number of plants that would incu r costs and the total pollutant removals (both pounds and TWPE) that would be achieved at other plant-level wet-scrubbed capacity thresholds for FGD wastewater for Option 3b.

1 Total plant-level wet-scrubbed capacity is calculated by summing the nameplate capacity for all of the units that are serviced by wet FGD systems.Memorandum April 19, 2013 Page 2

Table 1. FGD Wastewater Plant-Level Wet-S crubbed Capacity Threshold Evaluation a

Plant-Level WetScrubbed Capacity

Threshold (MW) Number of Plants Incurring Costs Pollutant Removals Achieved by Regulation b

Pounds Removed (lbs/yr) TWPE Removed (TWPE/yr)

None a 116 1,160,000,000 2,620,000

500 94 1,120,000,000 2,470,000

1,000 61 944,000,000 1,770,000

1,500 37 668,000,000 1,200,000

2,000 17 446,000,000 908,000 Note: Removals are rounded to three significant figures.
a – All threshold evaluations for FGD wa stewater include establishing BAT effluent limits equal to BPT for existing generating units with a total nameplate generating capacity of 50 MW or less. b – Excludes loadings for BOD, COD, TSS, and TDS.

For Regulatory Option 4a, EPA is proposing to esta blish “zero discharge” effluent limits for all pollutants in bottom ash transport water, with the exception of all generating units with a nameplate generating capacity of 400 MW or less . As part of the analysis, EPA also evaluated other unit-level capacity thresholds . Table 2 presents the number of plants that would incur costs and the total pollutant removals (both pounds a nd TWPE) that would be achieved at other unitlevel thresholds for bottom ash transport water for Option 4a. 2

Table 2. Bottom Ash Transport Water Unit-Level Capacity Threshold Evaluation

Unit-Level Capacity

Threshold (MW) Number of Plants Incurring Costs Pollutant Removals Achieved by Regulation a

Pounds Removed (lbs/yr) TWPE Removed (TWPE/yr)

50 240 1,700,000,000 2,710,000

100 220 1,590,000,000 2,540,000

200 172 1,280,000,000 2,050,000

300 138 1,100,000,000 1,750,000

400 115 991,000,000 1,570,000

500 100 918,000,000 1,430,000

600 67 739,000,000 1,150,000 Note: Removals are rounded to three significant figures. a – Excludes loadings for BOD, COD, TSS, and TDS.

2 EPA estimated the bottom ash transport water pollutant removals associated with Option 4a by developing adjustment factors that were applied to the pollutant rem ovals associated with bottom ash transport water based on the 50 MW unit-level capacity threshold. For more deta ils on how EPA estimated the bottom ash transport water pollutant removals, see the memorandum entitled, “Memorandum to the Rulemaking Record: Methodologies for Estimating Costs and Pollutant Removals for Steam Electric ELG Regulatory Option 4a” (DCN SE03834). The same methodology was used to estimate the pollutant removals for the other bottom ash transport water unit-level capacity thresholds presented in Table 2.