Final Notes from Site Visit at CWLP’s Dallman Power Station on April 2 6 , 20 1 0

EPA conducted a site visit at the City, Water, Light, & Power (CWLP) Dallman Power Station ( Dallman ) located in Lake Springfield , I L on April 2 6 , 20 1 0 to learn about the operations at the plant

, specifically to learn about the pre treatment technologies evaluated for FGD wastewater. Table 2 , located at the end of th ese notes , identifies the site visit participants. The presentation that the CWLP personne l 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 , 20 1 0.

Plant Overview

CWLP is a municipal utility for the City of Springfield that operates four coal

- fired generating units at Dallman

, as shown in T able 1 , with a net capacity of 517 MW. Dallman 4 Power Station (i.e., Unit 4) is located west of the original Dallman Station an d was completed in 2009.

Table 1: Dallman Power Station Units Operation

Unit Installation Date Net Capacity (MW) Particulate Control NOx Control a SO 2 Control Dallman 1 (Unit 31) 1968 70 ESP (cold

- side) Selective catalytic reduction (SCR) Common w et flue gas desulfurization (FGD) for both units Dallman 2 (Unit 32) 1972 70 ESP (cold

- side) SCR

Dallman 3 (Unit 33) 1978 175 ESP (cold

- side) SCR Wet FGD

Unit 4 May 2009 202 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 SO 2 /MMBTU, and the c hlorine 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 2 0% fly ash and 8 0% 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% SO 2 removal and is a one

- pass system. The FGD is designed for a maximum chlorides concentration of 12,000
p pm.Page 2

Dallman 3

• Dallman 3 operate s a pulverized coal

- fired boiler and a once

- through cooling system

. The unit is equipped with an SCR installed in 2003 that operate s year round and achieve s more than 8 0 % 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 SO 2 removal efficiency (currently > 90 %)

. 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; f ly 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 in stalled 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% SO 2 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 o r wet. Bottom ash is removed using a submerged chain conveyor.

FGD Solids Treatment

• Th e FGD slurry from each scrubber is transferred to a set of hydro cy clone s 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 blowdown from the three FGD scrubbers totals about 250,000 gallons/day.

• The underflow from the hydro cy clone s is transferred to a rotary vacuum drum for dewatering . Dewatered gypsum is 10

- 12% moisture

. The overflow is returned to the scrubber

. 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 for trucking of the gypsum to its destination. Dall man attempts to give away all the gypsum, but that is not always possible.Page 3

• The landfill is lined with a 5 f oot clay liner and geotextile liner, and is equipped with a leachate collection system. Leachate is transferred to the Dallman ash pond and monitore d quarterly.

FGD Wastewater Treatment

• The filtrate from the vacuum drum is transferred to the plant pretreatment system, shown in Attachment 2. Dallman previously transferred the filtrate to an ash pond and directly discharged the effluent. However , due to issues with the discharge of boron, Dallman investigat ed 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 pre treatment syste m

. Dallman began testing t he 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 ag ent (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 transfe rred back to the scrubber

. 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
gy psum. NOTE: this problem has been corrected since the site visit and lime is

now 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 gpm , 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 2 009, the effluent had 0.2 ppm cyanide and <100 to 3,000 pp t mercury (based on analysis by EPA Method 1631E for mercury)

.
Alternate Technologies Investigated for FGD Discharge

• Dallman also investigated other alternate technologies for treating the FGD wastewater before deciding to pro ceed 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,Page 4

before an estimate of $40 mil lion 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 g enerated very large. Essentially, the system coagulated other pollutants before boron.

Ash Handling

• Wet fly ash from Units 1

- 3 is sluiced to the north portion of the Dallman ash pond, along with bottom ash from unit 3. B ottom ash f rom U nits 1 and 2 is sluiced to the southwest corner of the Dallman ash pond

.

• B ottom 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 inve stigated converting Units 1

- 3 to dry fly ash handling. However, they had difficulty find ing a central location for a silo on the site.

• The Dallman ash pond has a bout 10 year s 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 pond 1 and polymer is added prior to discharge to Sugar Creek or 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.Page 5

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