Notes from Site Visit at Ameren Corp oration’s Duck Creek Energy Center on April 27, 2010

EPA conducted a site visit at the Ameren Co rporation’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 a nd how they operated without the discharge of FGD wastewater. Table 1, located at the end of th ese notes, identifies the site visit participants. The water flow diagram discusse d during the site vis it is provided as Attachment 1 to these notes. The presentation Duck Creek personnel ga ve during the site vi sit is included as

Attachment 2.

These notes describe the information collected du ring the site visit and the pre-site visit phone call, which was held on April 8, 2010.

Plant Overview

 Ameren Corporation’s subsidiary, Am eren 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 gene rating unit with a coal-fired cyclone boiler. The unit has a gro ss 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 cata lytic 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 contro l particulate emissions a nd upgraded their flue gas desulfurization (FGD) system to a lime stone, forced oxidation system to better

control SO 2 . The plant also installed a conti nuous emissions monitoring system at

this time.

 The catalyst for the SCR is not regenerate d 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 s ite at any given time, with ditch collection for rainwater, which is transferre d 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 SO 2 . The absorber is made of carbon steel with a flake glass lining.

FGD System

 The new FGD scrubber system is a Hitach i spray tower design, with forced air oxidation, which operates with a counte r-current spray. The Hitachi design includes a continuous limestone slurry bleed loop, which the plant stated allowsPage 2

higher SO 2 removal than a batch system. The system achieves 95% removal of

SO 2

.

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

mill was installed at the time the new sc rubber 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 lime stone slurry with about 30% solids.

 The FGD system has five spray levels, a nd the plant typically operates three to four levels at a time dependent on the SO 2 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 range s 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 ope rates at about 2,500 ppm chlorides. The plant stated that the chloride con centration is dependenton 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 th e 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 comp rised 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 ul timately 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 geot extile 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 volu me of 33 million gallons (water is approximately 20 feet deep). This pond receives the gypsum stack decant, stack runoff, and leachate from the gypsum stac k. The leachate collection system has been operating since March 2009 and no leachat e had yet been collected as of thePage 3

time of the site visit. Dam safety measur es 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. Mixe rs 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% P RB. For another Ameren plant, their ash marketability was further reduced sin ce they are adding ac tivated 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 ba sin 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 th e 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 hand ling 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.Page 4

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 coo ling 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 (eleva tion 562.5) for Illinois River.

 Outfall 004 is a new outfall to allow disc harge 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 us ed 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 tr ansferred 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 activ ely 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 Illinoi s River. The out of service ash ponds are monitored using a series of 44 groundw ater 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 tr ansferred to th e reservoir.Page 5

 The plant is currently evaluating di fferent 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 installa tion of groundwater monitoring.

 In Duck Creek’s 2004 permit packag e, 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 pollu tants on water quality. A copy of this technology evaluation is in cluded as Attachment 3.Page 6Table 1. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailMichael BollingerAmeren314-554-3652 mfbollinger@ameren.comRoger FergusonAmeren314-825-9163 rferguson3@ameren.comJim Marshall Ameren 309-668-3804 jmarshall@ameren.comRich Phillips Ameren 314-609-5947 rphillips@ameren.comGreg Russell Ameren 309-668-3800 grussell2@ameren.comMichael Smallwood Ameren 314-554-4581 mjsmallwood@ameren.comSteve WhitworthAmeren314-554-4908 scwhitworth@ameren.comDonna HillUWAG205-257-5234 dbhill@southernco.comBill BuscherIllinois EPA217-785-4787 bill.buscher@illinois.govDarin LeCroneIllinois EPA217-782-0610 Darin.lecrone@illinois.govLeslie Lowry Illinois EPA 217-782-0610 leslie.lowry@illinois.govRon Jordan EPA/Office of Water 202-566-1003 jordan.ronald@epa.govBill Swietlik EPA/Office of Water202-566-1129 swietlik.william@epa.govDeb Bartram ERG (Contractor to EPA) 703-633-1669 deborah.bartram@erg.comTJ Finseth ERG (Contractor to EPA) 703-633-1698 thomas.finseth@erg.com