Notes from Site Visit at CWLP’s Dallman Power Station on April 26, 2010

EPA conducted a site visit at the City, Water, Light, & Power (CWLP) Dallman Power Station 

(Dallman) located in Lake Springfield, IL on April 26, 2010 to learn about the operations at the 

plant, specifically to learn about the pretreatment technologies evaluated for FGD wastewater.

Table 2, located at the end of these notes, identifies the site visit participants. The presentation 

that the CWLP personnel gave during the site visit is provided as Attachment 1. 

These notes describe the information collected during the site visit and the pre-site visit phone 

call, which was held on April 8, 2010.

Plant Overview

CWLP is a municipal utility for the City of Springfield that operates four coalfired generating units at Dallman, as shown in Table 1, with a net capacity of 517 

595 MW. Dallman 4 Power Station (i.e., Unit 4) is located west of the original 

Dallman Station and was completed in 2009. [QUESTION FOR DALLMAN: 

Please confirm total net capacity.]

Table 1: Dallman Power Station Units Operation

Unit

Installation 

Date

Net Capacity 

(MW) Particulate Control NOx Controla SO2 Control

Dallman 1 

(Unit 31)

1968 7086 ESP (cold-side) Selective catalytic 

reduction (SCR)

Common wet flue gas 

desulfurization (FGD) 

Dallman 2 for both units

(Unit 32)

1972 7087 ESP (cold-side) SCR

Dallman 3

(Unit 33)

1978 175192 ESP (cold-side) SCR Wet FGD

Unit 4 May 2009 202230 Baghouse + wet ESP SCR Wet FGD a Catalysts are regenerated off site.

Dallman receives about 200 - 250 truckloads of coal per day from the Illinois 

Viper Mine and keeps a 2- to 3-week supply on site. Their coal has sulfur 

concentrations ranging from 5.8 to 6.2 lbs SO2/MMBTU, and the chlorine content 

ranges up to 2,000 ppm.

Dallman 1 and 2

• Dallman 1 and 2 operate cyclone-fired boilers and once-through cooling systems.

Both units are equipped with SCRs installed in 2003 that operate year round and 

achieve more than 85% reduction in NOx.

• These units generate about 20% fly ash and 80% bottom ash and are equipped 

with electrostatic precipitators (ESPs); all ash (i.e., fly and bottom ash) is handled 

wet.

• Dallman 1 and 2 share one limestone, forced oxidation FGD system, installed in 

2000. This system achieves more than 90% SO2 removal and is a one-pass 

system. The FGD is designed for a maximum chlorides concentration of 
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12,000xxxx pm. [QUESTION FOR DALLMAN: Please provide design chlorides

concentration.]

Dallman 3

• Dallman 3 operates a pulverized coal-fired boiler and a once-through cooling 

system. The unit is equipped with an SCR installed in 2003 that operates year 

round and achieves more than 80% reduction in NOx.

• A limestone, forced oxidation FGD system was installed on Dallman 3 in 1978 

and is planned to be upgraded in 2011 to increase the SO2 removal efficiency

(currently >9085%). The FGD system currently has one tray and will be 

upgraded to add a second tray. The FGD is designed for a maximum chlorides 

concentration of 15,000 ppm.

• The unit is equipped with an ESP; fly ash and bottom ash from this unit are

handled wet.

Dallman 4

• Dallman 4 operates a pulverized coal-fired boiler and a recirculating cooling 

system (i.e. cooling tower) due to heat limits on Lake Springfield. The unit is 

equipped with an SCR that was installed at the time the units was built. The SCR 

system operates year round and achieves more than 85% reduction in NOx.

• A limestone, forced oxidation FGD system was installed on Dallman 4 in 2009, 

when the unit was built. The FGD achieves >95% SO2 removal. The FGD is 

designed for a maximum chlorides concentration of 15,000 ppm. 

• The unit is equipped with a baghouse, for dry fly ash removal, and a wet ESP, for 

acid mist collection. Fly ash is stored in an on-site silo and can be loaded either 

dry or wet. Bottom ash is removed using a submerged chain conveyor.

FGD Solids Treatment

• The blowdown from the three FGD scrubbers totals about 250,000 gallons/day. 

This FGD slurryblowdown from each scrubber is transferred to a set of 

hydrocyclones to separate the gypsum solids from the water. Note that each of the 

Unit 31/32, 33, and 4 scrubbers has its own solids handling equipment.

• The underflow from the hydrocyclones is transferred to a rotary vacuum drum for 

dewatering. Dewatered gypsum is 10-12% moisture. The overflow is returned to 

the scrubber. The blowdown from the three FGD scrubbers totals about 250,000 

gallons/day Dallman washes the gypsum with city water (or sometimes service 

water) to meet a 200 ppm chlorides limit for wallboard manufacturing.

• The gypsum from the vacuum drum is not significantly different between the 

three scrubbers, and is stored in a 3.5-acre onsite landfill before it is ultimately 

given away to cement plants or for use in wallboard manufacturing. Dallman pays 
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for trucking of the gypsum to its destination. Dallman attempts to give away all 

the gypsum, but that is not always possible.

• The landfill is lined with a 5 foot clay liner and geotextile liner, and is equipped 

with a leachate collection system. Leachate is transferred to the Dallman ash pond 

and monitored quarterly.

FGD Wastewater Treatment

• The filtrate from the vacuum drum is transferred to the plant pretreatment system, 

shown in Attachment 2. The blowdown from the three FGD scrubbers totals about 

250,000 gallons/day Dallman previously transferred the filtrate to an ash pond and 

directly discharged the effluent. However, due to issues with the discharge of 

boron, Dallman investigated indirectly discharging the FGD wastewater to the 

local POTW. Dallman was required to install pretreatment before such discharge 

was allowed and now operates the onsite FGD pretreatment system. Dallman 

began testing the system in June 2009 and began full operation and discharging to 

the POTW in November 2009.

• The filtrate enters the influent equalization tank before it is transferred to the 

clarifier, where the plant adds a metal chelating agent (either Nalmet or Metclear), 

lime, a cationic polymer, and an anionic polymer. The clarifier residence time is 

approximately 90 minutes.

• The effluent from the clarifier (<10 ppm solids) is transferred to the effluent tank, 

while the solids are transferred back to the scrubber. If necessary for pH control, 

Dallman adds carbon dioxide. The final total suspended solids effluent 

concentration is 8-10 ppm.

• Dallman personnel stated that they do not add lime to the clarifier because the 

solids are transferred back to the absorbers and could cause issues with the 

gypsum. NOTE: this problem has been corrected since the inspection and lime is 

added continuously to the clarifier for pH control. 

• The flow rate through the system is approximately 170 - 200 gpm. If the flow falls 

below 170 gpmthis, the plant recycles clarifier effluent to the influent equalization 

tank to make up the flow.

• The system is operated in batch mode, except when all three FGD systems are 

operating simultaneously.

• Based on a system test completed in June 2009, the effluent had 0.2 ppm cyanide 

and <100 to 3,000 ppt mercury (based on analysis by EPA Method 1631E for 

mercury).
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Alternate Technologies Investigated for FGD Discharge

• Dallman also investigated other alternate technologies for treating the FGD 

wastewater before deciding to proceed with discharging the FGD wastewater to 

the local POTW.

• Dallman investigated installing a brine concentrator system to meet an estimated 

1 mg/L boron limit. The initial cost estimate of $1 million escalated to $8 million, 

before an estimate of $40 million capital was determined. Because there was no 

guarantee of effluent quality, Dallman decided not to pursue further.

• Dallman also investigated electrocoagulation but found the waste characteristics 

were damaging the equipment and the volume of waste generated very large. 

Essentially, the system coagulated other pollutants before boron.

Ash Handling

• Wet fly ash from Units 1-3 is sluiced to the northback portion of the Dallman ash 

pond, along with bottom ash from unit 3. while Bbottom ash from Units 1-23 is 

sluiced to the southwest corner front portion of the Dallman ash pond.

• All Bbottom ash from units 1 and 2 is beneficially reused as roofing shingles. 

Dallman dredges the ash out of the southwest corner of the Dallman ash pond as 

needed for the market.

• Dallman also investigated converting Units 1-3 to dry fly ash handling. However, 

they had difficulty finding a central location for a silo on the site.

• The Dallman ash pond has about 10 years remaining in its life and is unlined. 

Effluent from the ash pond overflows to the Clarification Pond, where it is 

commingled with effluent from the Lakeside ash pond1 and polymer is added

prior to discharge to Sugar Creek (prior to Lake Springfield).

 1 Lakeside is an adjacent power plant retired by CWLP in 2009. The Lakeside ash ponds were not closed at the time 

of the site visit, and water still contributed to the final discharge through Outfall 004.
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Table 2. Site Visit Attendees

Name Organization (Representing) Telephone E-mail

Sue Corcoran CWLP 217-757-8610 x1108 Sue.corcoran@cwlp.com

Doug Brown CWLP 217-757-8670 Doug.brown@cwlp.com

John Davis CWLP 217-757-8670 John.davis@cwlp.com

Dave Farris CWLP 217-757-8610 Dave.farris@cwlp.com

Gregg Finigan CWLP 217-757-8670 x2481 Gregg.finigan@cwlp.com

Jeff Hillebrenner CWLP 217-757-8670 x2432 Jeff.hillebrenner@cwlp.com

Scott Rogers CWLP 217-757-8670 Scott.rogers@cwlp.com

Christine Zeman CWLP 217-789-2116 Christine.zeman@cwlp.com

Donna Hill UWAG 205-257-5234 dbhill@southernco.com

Darin LeCrone Illinois EPA 217-782-0610 Darin.LeCrone@illinois.gov

Ron Jordan EPA/Office of Water 202-566-1003 jordan.ronald@epa.gov

Bill Swietlik EPA/Office of Water 202-566-1129 Swietlik.william@epa.gov

Deb Bartram ERG (Contractor to EPA) 703-633-1669 deborah.bartram@erg.com

TJ Finseth ERG (Contractor to EPA) 703-633-1698 Thomas.finseth@erg.com