Notes from Site Visit at Ameren Corporation’s Duck Creek Energy Center 

on April 27, 2010 

EPA conducted a site visit at the Ameren Corporation’s Duck Creek Energy Center (Duck 

Creek) located in Fulton County, IL on April 27, 2010 to learn about the operations at the plant, 

specifically to learn about the FGD operations and how they operated without the discharge of 

FGD wastewater. Table 1, located at the end of these notes, identifies the site visit participants. 

The water flow diagram discussed during the site visit is provided as Attachment 1 to these 

notes. The presentation Duck Creek personnel gave during the site visit is included as 

Attachment 2. 

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 

 Ameren Corporation’s subsidiary, Ameren Energy Resources Generating 

Company, is comprised of two coal-fired power plants: Duck Creek (Canton, IL) 

and E.D. Edwards (Bartonville, IL). 

 The Duck Creek plant operates one generating unit with a coal-fired cyclone 

boiler. The unit has a gross capacity of 465 MW and a net capacity of 430 MW. 

 The unit was originally installed in 1976. The unit has operated with a FGD 

system since its initial operation. In 2003, a selective catalytic reduction (SCR) 

system to control NOx emissions was added, followed by an upgrade to a low 

NOx burner in 2007. In March 2009, Duck Creek installed an electrostatic 

precipitator (ESP) to control particulate emissions and upgraded their flue gas 

desulfurization (FGD) system to a limestone, forced oxidation system to better 

control SO2. The plant also installed a continuous emissions monitoring system at 

this time. 

 The catalyst for the SCR is not regenerated on site. To date, the plant has changed 

one layer of catalyst in the system. 

 The plant burns about 1 million tons of coal per year. Approximately 400,000 

tons of coal and limestone is stored on site at any given time, with ditch collection 

for rainwater, which is transferred to the cooling water reservoir. 

 The system was designed to operate with 100% Illinois bituminous coal; however, 

the plant currently operates with a blend of Powder River Basin (PRB) coal. The 

coal typically runs between 900 and 1,000 ppm SO2. The absorber is made of 

carbon steel with a flake glass lining. 

FGD System 

 The new FGD scrubber system is a Hitachi spray tower design, with forced air 

oxidation, which operates with a counter-current spray. The Hitachi design 

includes a continuous limestone slurry bleed loop, which the plant stated allows 
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higher SO2 removal than a batch system. The system achieves 95% removal of 

SO2. 

 Duck Creek operates a horizontal wet ball mill to process the limestone. A new 

mill was installed at the time the new scrubber system was installed. The old ball 

mill was also upgraded and is used as a backup system. Duck Creek uses water 

from their cooling pond to create a limestone slurry with about 30% solids. 

 The FGD system has five spray levels, and the plant typically operates three to 

four levels at a time dependent on the SO2 removal rate achieved. 

 The pH of the system is 5.8 S.U., with a density of 70 pounds per cubic foot. The 

level in the system ranges from 18 to 22 percent. 

 The FGD system is designed to operate up to a maximum chlorides level of 

50,000 ppm; however, the plant currently operates at about 2,500 ppm chlorides. 

The plant stated that the chloride concentration is dependent on the coal blend 

combusted in the boiler. 

 The system has a feed forward control system to trigger blowdown. The bleed 

stream is transferred to a tank, where it is mixed with reclaim water to dilute the 

stream to 2% solids. This dilution is to prevent plugging of solids in the two sets 

of 3-mile transfer lines to the gypsum management facility. 

FGD Solids and Wastewater Treatment 

 The FGD system is a closed loop system. Duck Creek uses water from the 

gypsum management facility as make up water to the system, and ultimately 

blows down FGD wastewater to the closed loop system. The plant must manage 

the influx of rainwater to maintain the water balance within the closed loop 

system. 

 The plant was not able to quantify the flow of blowdown because it is not 

measured, but the plant stated that the blowdown flow could be calculated using 

pump runtime and capacity. 

 The gypsum management facility is comprised of a 30-acre pond in which the 

diluted bleed stream is fed to settle out the gypsum and the decant water is 

transferred to a reclaim pond which is ultimately returned to the FGD system. 

Gypsum can be stacked up to 100 feet high. The gypsum stack pond is lined with 

compacted clay, and a 60-ml HDPE and geotextile double liner with integral leak 

detection and leachate collection between the two HDPE liners. Duck Creek 

expects the lifespan of the pond will be 7 to 8 years, and will be expanded as 

needed. 

 The reclaim pond is 10 acres with a volume of 33 million gallons (water is 

approximately 20 feet deep). This pond receives the gypsum stack decant, stack 

runoff, and leachate from the gypsum stack. The leachate collection system has 

been operating since March 2009 and no leachate had yet been collected as of the 
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time of the site visit. Dam safety measures require that the reclaim pond also has 

four relief pipes for overflow to the cooling water pond. 

 The gypsum stack pond is monitored using a series of 40 groundwater monitoring 

wells. 

Fly Ash Handling System

 

 The fly ash handling system was retrofitted in 2005 and 2006 to a dry ash 

(vacuum pump) handling system. 

 The dry ash is transferred to the top of onsite silos, where the ash is separated 

using bag filters similar to a baghouse. Mixers at the bottom of the silos move the 

ash to the storage facilities. Duck Creek uses fresh water to condition the ash. 

Although Duck Creek also has the ability to load ash dry (i.e., unconditioned), the 

dry unloading capabilities had not yet been used at the time of the site visit 

because none of the fly ash has been marketed/reused. 

 Duck Creek personnel stated that ash from a mixture of PRB and bituminous coal 

is not as competitive as ash from 100% PRB. For another Ameren plant, their ash 

marketability was further reduced since they are adding activated carbon for 

mercury controls. 

 The dry ash that will be disposed is transferred to the onsite landfill. 

Bottom Ash Handling System

 

 The current bottom ash handling system began in 2008, and all bottom ash is 

beneficially reused in road construction. 

 Bottom ash is sluiced from the boiler to one of two primary settling basins. The 

majority of the ash settles out in the primary basins, where it is pushed out and 

allowed to dewater. While one primary basin is being cleaned out, the other is 

used to treat the bottom ash sluice. The decant from the primary basins is 

transferred to one combined secondary equalization basin, where it then 

overflows continuously to the cooling water reservoir. 

 The basins are lined with compacted clay, HPDE, and 8 inches of concrete. 

 Duck Creek uses 2 MGD of bottom ash sluice water. The source for this water is 

treated service water from the cooling water reservoir. 

 Duck Creek’s previous bottom ash handling system combined the bottom ash 

with low volume wash water and FGD solids, and placed this material in the old 

ash ponds. Both bottom ash solids and bottom ash sluice water were sent to the 

former ash pond system. 
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Other Plant Wastewater

 The plant generates low volume waste from the water treatment system (0.5 

MGD), the turbine room sump (0.3 MGD), and the boiler room sump (0.3 MGD). 

This water is treated in the bottom ash basins. 

 Runoff from the onsite landfill is transferred to the cooling water reservoir, while 

leachate from the onsite landfill is used for dust control and/or in the gypsum 

management facility. 

Plant Outfalls

 Duck Creek has four outfalls: 

 001: Dam seepage collection; 

 002: Cooling pond overflow (elevation 565) for Duck Creek; 

 003: Intake screen backwash; and 

 004: Cooling pond overflow (elevation 562.5) for Illinois River. 

 Outfall 004 is a new outfall to allow discharge to the Illinois River. Both the 

Illinois River reservoir makeup water and Outfall 004 share a pipeline. The 

Illinois River reservoir make water intake structure was used to originally fill the 

cooling water pond, while 004 can be used to discharge to the river. 

 Outfall 002 has not been used since 2004 as there have been no cooling water 

reservoir discharges via this outfall. 

Ash Ponds 

 Duck Creek previously had three unlined ash ponds: 

 Ponds 1 and 2: all wastewater was transferred to Pond 1 until full, then 

moved to Pond 2 (each pond had a 7-14 day turnover); 

 Recycle Pond: this pond was built for surge capacity for the plant. 

 At the time of the site visit, Pond 1 was mounded with ash, while Pond 2 had 

freestanding water. Duck Creek is actively involved in closing the ponds. They 

are transferring the remaining water to the reservoir, which discharges via 

Outfalls 002 and 004. 

 Duck Creek conducted a study to look at the impact of the out of service pond 

discharges to the reservoir and the Illinois River. The out of service ash ponds are 

monitored using a series of 44 groundwater monitoring wells. A hydrogeologic 

report was delivered to the State of Illinois in March. The plant did not provide 

EPA a copy of this report because a subsequent evaluation was conducted after 

the water from the ponds was transferred to the reservoir. 
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 The plant is currently evaluating different methods for closing the ponds, 

including “in place closure” (no removal of solids), with a cap and cover, 

installation of a storm water management system, and installation of groundwater 

monitoring. 

 In Duck Creek’s 2004 permit package, the plant conducted a technology 

evaluation related to closing the ash ponds, including the cost and feasibility of 

treating the ash pond water, discharging to both Duck Creek and the Illinois 

River, and impact of boron and other pollutants on water quality. A copy of this 

technology evaluation is included as Attachment 3. 
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 Table 1. Site Visit Attendees 

Name Organization (Representing) Telephone E-maiMichael Bollinger Ameren 314-554-3652 mfbollinger@ameren.coRoger Ferguson Ameren 314-825-9163 rferguson3@ameren.coJim Marshall Ameren 309-668-3804 jmarshall@ameren.com Rich Phillips Ameren 314-609-5947 rphillips@ameren.com Greg Russell Ameren 309-668-3800 grussell2@ameren.com Michael Smallwood Ameren 314-554-4581 mjsmallwood@amerenSteve Whitworth Ameren 314-554-4908 scwhitworth@ameren.cDonna Hill UWAG 205-257-5234 dbhill@southernco.com Bill Buscher Illinois EPA 217-785-4787 bill.buscher@illinois.goDarin LeCrone Illinois EPA 217-782-0610 Darin.lecrone@illinois.Leslie Lowry Illinois EPA 217-782-0610 leslie.lowry@illinois.goRon Jordan EPA/Office of Water 202-566-1003 jordan.ronald@epa.gov Bill Swietlik EPA/Office of Water 202-566-1129 swietlik.william@epa.gDeb Bartram ERG (Contractor to EPA) 703-633-1669 deborah.bartram@erg.cTJ Finseth ERG (Contractor to EPA) 703-633-1698 thomas.finseth@erg.com