### Final Notes from Site Visit at
Louisville Gas & El ectric Company’s M ill Creek Station on December 12, 2008

EPA conducted a site visit at Louisville Gas & Electric Company’s Mill Creek Station (Mill Creek) located in Louisville, KY on Friday, Decemb er 12, 2008 to learn about the operations at the plant, specifically the FGD wastewater handli ng system. Table 1, located at the end of this memorandum, identifies the site vi sit participants. The presentati on that the Mill Creek personnel gave during the site visit is provided as an at tachment to this memorandum. Also included as
attachments to this memorandum are a labeled aeri al photo of the plant, an overall process flow diagram for the generating units, a process flow diagram for the FGD systems, and the specifications for the gypsum to be ma rketed for wallboard manufacturing.

This memorandum describes the information collected during the site visit, as well as the pre-site visit phone call, which was held on November 17, 2008.

Plant Overview

 Mill Creek operates four coal-fired generating units at the power plant, which is a baseload plant with a net generati ng capacity of 1,470 MW. Mill Creek is Louisville Gas & Electric Company’s larg est plant, based on generating capacity. The table below contains some general information for the four generating units. A process flow diagram for Units 1 through 4 is included as an attachment to this
memorandum.

Unit Installation
Date Capacity (MW) Particulate
Control NOx Control SO 2 Control 1 1972 356 ESP (cold-side) Low-NOx
burners and
overfire air Wet FGD installed (1980). Subsequently modified.

2 1974 356 ESP (cold-side) Low-NOx
burners and
overfire air Wet FGD installed (1981). Subsequently modified.

3 1978 443 ESP (cold-side) SCR, lowNOx burners Wet FGD in original design (1978)4 1982 544 ESP (cold-side) SCR, lowNOx burners Wet FGD in original design (1982)

 Mill Creek burns eastern bituminous coal in all four units. The plant burns approximately 4.6 million tons of coal per year. The coal comes from the Illinois basin and is mostly mined in Kentucky, I ndiana, southern Ohio, West Virginia,
and Illinois. The coal is delivered to the plant by barge and by railroad.

 The sulfur content of the coal used at Mill Creek is typical ly 3.3 to 3.4 percent sulfur (6.0 to 6.2 lbs SO 2 /mmBTU). Mill Creek stated th at if the sulfur content is too low, it can cause issues with the E SP. Low sulfur content has a negative effect in the ESP on the flyash resistiv ity and thus reduces the ESP particulate removal efficiency.Page 2

 The chlorine content of the coal typically averages <1,500 ppm.

 The coal pile runoff is collected in a coal pile runoff pond that also receives limestone pile runoff. The overflow from the coal pile runoff pond is transferred
to the ash treatment basin.

 Prior to the site visit, Mill Creek personne l collected four samples from the coal pile runoff pond and measured the pH and temperature. The table below presents the results of the pH measurements.

Date pH (S.U.)
11/21/2008 7.41
11/28/2008 7.21
12/4/2008 7.01
12/8/2008 7.11

 Mill Creek operates an SCR system on Units 3 and 4. Mill Creek has typically operated the SCR systems only during the ozone season. Because of the uncertainty of CAIR, Mill Creek will begin operating the SCRs year round.

 Mill Creek does not currently add hydrated lime or trona to the flue gas because the SCRs convert only a small amount of su lfur dioxide to sulf ur trioxide. Mill Creek stated that hydrated lime will be injected into Units 3 and 4 by the end of 2011 to meet compliance with the Best Available Retrofit Technology (BART)
standards.

 Mill Creek uses the Ohio River as the source of the power plant’s water. Mill Creek operates a once-through cooling system for Unit 1 and recirculated cooling tower systems for Units 2, 3, and 4.

 The Unit 1 once-through cooling water is disc harged directly to the Ohio River. The Unit 2 cooling tower blowdown is transf erred to the ash treatment basin prior to discharge. Some of the Unit 3 and 4 cooling tower blowdown is transferred to the FGD clearwell and reused in the FGD pr ocess and the remainder is discharged directly to the Ohio River.

 The Mill Creek plant is located on approximately 500 acres of land.

 Mill Creek employs 213 full-time workers.

FGD System

 Mill Creek operates a limestone, forced oxidation wet FGD scrubber on each of the four generating units. A process flow diagram for the FGD systems is
included as an attachment to this memorandum.

 All four FGD systems were initially in stalled as lime, inhibited oxidation wet
FGD scrubbers. Mill Creek mixed the calci um sulfite product with lime and flyPage 3

ash and produced a poz-o-tec material, sim ilar to concrete, that was landfilled. Between 1996 and 1998, Mill Creek converted ea ch of the scrubbers to limestone, forced oxidation systems.

 Mill Creek stated that the gypsum is clean er and much easier to manage than the poz-o-tec material. Additionally, the plan t is capable of selling most of the gypsum, whereas all of the poz-o-tec material had to be landfilled.

 Mill Creek uses ball mills to crush the limestone to the correct size for use in the limestone slurry. FGD clearwell water or Unit 3 and 4 cooling tower blowdown is used to prepare the limestone slurry.

 Mill Creek uses approximately 475,000 tons of limestone each year (dry basis). The limestone is delivered to the plant via barge.

 The Unit 1 and 2 FGD systems each have two absorber modules and one reaction tank. The Unit 3 and 4 FGD systems each have four absorber modules and two
reaction tanks. All of the absorber modul es have four spray headers and one tray, with one of the spray headers located below the tray.

 The Unit 3 reaction tanks were constr ucted partially below ground and have individual, separated cells w ithin the reaction tanks. Mi ll Creek stated that the design of the Unit 3 reacti on tank decreases th e performance of the FGD system. Therefore, Mill Creek adds formic acid to the Unit 3 FGD system to increase the sulfur dioxide removal efficiency. Mill Creek used to add DBA, but they stated that DBA is no longer readily available to purchase.

 The FGD systems remove approximately 88 to 93 percent of the sulfur dioxide from the flue gas.

 Mill Creek continuously runs the blowdow n pumps for each of the scrubber
modules. Most of the time the blowdown is recycled back to the reaction tank in the module. The blowdown from the FGD systems is intermittently directed to the hydroclones based on solids control in the reaction tank. The solids in the
reaction tanks are controlled to between 10 and 13 percent solids. Limestone slurry is added to the reaction tanks to control the pH between 5.5 and 5.9. To make up for the evaporative water loss in the scrubbers and to control the level in each reaction tank, Mill Creek adds water from the FGD clearwell to the reaction
tanks.

 The FGD systems are not constructed of hi gh alloy materials, so the chloride limit for the scrubbers is relatively low. The Unit 1 and 2 FGDs are constructed of
316L stainless steel and have a target chloride level of 1,500 ppm. The Unit 3 and
4 FGDs are constructed of 317LM stainless steel and have a target chloride level of 2,000 ppm.

 The blowdown from the reaction tanks is transferred to hydroclones to separate the solids from the aqueous phase. There ar e six sets of hydroclones at the plant, one for each reaction tank (Units 1 and 2 each have one set of hydroclones andPage 4

Units 3 and 4 each have two sets of hydr oclones). Each set of hydroclones are operated approximately 14 hours during the day.

 Approximately 70 to 80 percent of the hydr oclone overflow is recycled back to the reaction tanks; the remai nder is purged to the ash tr eatment basin. Mill Creek estimates that the hydroclone overflow c ontains three to four percent solids.

 Mill Creek monitors the chlorides in th e reaction tanks daily to determine the amount of purge that is required to main tain the chlorides concentration. Mill Creek stated that the FGD scrubber purge flow rate is approximately 1,000 gpm
for all four units combined.

 The hydroclone underflow is transferred to the hydroclone un derflow tanks. There is one hydroclone underflow tank fo r every two sets of hydroclones, so Units 1 and 2 share a hydroclone underf low tank and Units 3 and 4 each have a separate tank. Mill Creek estimates that the hydroclone underflow contains 40 to 50 percent solids.

 The hydroclone underflow is then transfe rred to two filter feed tanks, which are approximately 2,500 feet away at the gypsum processing plant.

 From the filter feed tanks, the gypsum slurry is fed to the rotary drum vacuum filters. The gypsum is washed with hot-side cooling tower blowdown (cooling
water downstream of the condensers a nd upstream of the cooling tower) to remove the chlorides. The gypsum produced has a moisture content of approximately 12 percent.

 Mill Creek sells some of the gypsum that is produced in the FGD process to a wallboard manufacturer. Mill Creek pr oduces 768,000 tons of gypsum per year and sells approximately 654,000 tons; however , the contract that the plant has with the wallboard manufacturer expire s at the end of 2009. Therefore, Mill Creek is uncertain how much gypsum w ill be marketed after that time. Unmarketed gypsum is landfilled.

 Mill Creek delivers the gypsum to the wallboard manufacturer via barge. For the wallboard plant to accept the gypsum, th e gypsum must meet specifications agreed upon in the contract. The gyps um specifications are included as an
attachment to this memorandum.

 The filtrate from the rotary drum vacuum filters is transferred to the “E” settling pond, or emergency settling pond. The “E” settling pond covers approximately 1⁄2
acre and also receives floor drain wate rs from the gypsum processing plant.

 From the “E” settling pond, the FGD wast ewater is transferred to the “Dead Storage” pond. The “Dead Storage” pond c overs approximately one acre. The water in the “Dead Storage” pond can be tr ansferred to the FGD clearwell, but it is not typically done. Most of the wate r in the “Dead Storag e” pond is transferred to the gypsum processing and construction runoff pond.Page 5

 The gypsum processing and construction r unoff pond discharges directly to the Ohio River via Outfall 012. Mill Creek pe rforms quarterly monitoring at Outfall 012 for TSS, oil and grease, chlorides, a nd pH. Additionally, the plant tests for hardness, sulfate, and ammonia, but doesn ’t have any limits on these parameters.

 Mill Creek dredges the “E” settling pond, “Dead Storage” pond, and gypsum processing and construction runoff ponds a few times a year to maintain the pond in working condition. The solids remove d from the ponds are placed in the onsite landfill.

 Mill Creek operates a FGD clearwell, which is used as the source of make-up water for the FGD system. The FGD clear well receives water from the Ohio River, some of the Unit 3 and 4 cooling tower blowdown, and occasionally receives water from the “Dead Storage” pond.

Ash Handling and Wastewater Treatment

 Mill Creek operates cold-side electrostatic precipitators (ESPs) on all four generating units.

 Mill Creek estimates that approximately 425,000 tons of fly ash are generated each year from the operation of all four un its. The plant has been able to market approximately 300,000 tons of the fly as h per year to a cement manufacturer.

 There is a cement manufacturer (Cemex ) located across the street from Mill
Creek. Mill Creek stated that they have historically so ld a large amount of the fly ash to Cemex, but recently have not been able to sell as much because Cemex reduced production due to th e downturn in the economy.

 Mill Creek has both a wet and a dry fly ash handling system; however, the wet fly ash handling system is only used for em ergency purposes. Plant staff estimated that less than five percent of fly ash is handled wet. Mill Creek prefers to handle the fly ash dry because it is less expensive to do so. The plant initially sluiced all fly ash wet, but converted to dry fly as h handling when scrubbers were installed to enable it to operate a poz-o-tec proce ss, whereby FGD solids (calcium sulfite) were mixed with lime and dry fly ash to create a cementitous product (poz-o-tec).

 If the fly ash were handled wet, it would be transferred to the ash treatment basin. From the ash treatment basin, the plant would excavate the fly ash out of the pond
and truck it to the on-site landfill; therefore, they would be double handling the fly ash, increasing operating costs. The sour ce of ash sluice water is service water
and/or Unit 2 coo ling tower blowdown.

 The dry fly ash is pneumatically conveyed to the two fly ash silos, which are located approximately 2,000 feet from th e generating units. Mill Creek has two different methods for handling the fly ash fr om the silos. If the fly ash is being marketed, the fly ash is kept completely dr y and transferred into closed top trucks. If the fly ash is not marketable, then it is sent through a pug mill where FGDPage 6

clearwell water is added to the fly ash to a moisture content of 18 percent. The fly ash is then placed in a truck and tr ansferred to the on-site landfill.

 Mill Creek estimates that approximately 104,000 tons of bottom ash are generated each year from the operation of all four units. Mill Creek operates wet bottom ash handling systems for each unit. All of the bottom ash sluice is transferred to the
ash treatment basin.

 The bottom ash sluice enters the ash treatme nt basin in a channel. Most of the
bottom ash settles out within the channel and Mill Creek excavates the bottom ash from the channel five days a week.

 A vendor sorts the bottom ash by size a nd markets the bottom ash for use as
“black sand”. Mill Creek estimates th at approximately 71,000 tons of bottom ash is marketed per year. The remainder of the bottom ash is trucked to the on-site landfill for disposal.

 As discussed previously, the ash treatment basin al so receives some of the hydroclone overflow from the FGD process, which contains three to four percent gypsum. Like the bottom ash, the hydrocl one overflow enters the ash treatment basin in a channel. The gypsum present in the overflow settle s out of the water
within the channel. Mill Creek excavat es the gypsum from the channel weekly
and trucks it to the on-site landfill.

 The ash treatment basin also receives Unit 2 cooling tower blowdown and other
low-volume wastewaters. The overflo w from the ash treatment basin is commingled with the Unit 1 once-through c ooling water and is discharged to the Ohio River. Mill Creek does not reuse any of the ash treatment basin water at the plant.

 The ash treatment basin was built in the 1970’ s and is not lined. Mill Creek stated that they will be able to use the basi n for an extended period of time because the plant excavates almost all of the solids that are entering the pond.

Landfills

 Mill Creek has closed and capped one landfill at the plant. Mill Creek is currently operating another landfill.

 The current landfill was originally designed to receive the poz-o-tec material that the FGD systems were originally gene rating, along with fly and bottom ash.
After Mill Creek switched to forced oxidation scrubbers, it began sending the gypsum to the landfill.

 Mill Creek estimates that the current landf ill will only last for another two years before it reaches capacity and needs to be capped and closed. Therefore, the plant is already working on plans for a new landf ill that will provide the plant with 12 years worth of capacity.Page 7Table 1. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailMike Buckner Louisville Gas & Electric –Mill Creek (502) 933-6515mike.buckner@eon-us.comPhil CookLouisville Gas & Electric – Mill Creek(502) 933-6878 phil.cook@eon-us.comOz HaeberlinLouisville Gas & Electric – Mill Creek(502) 933-6977 oz.haeberlin@eon-us.comMike KirklandLouisville Gas & Electric – Mill Creek(502) 231-5035 mike.kirkland@eon-us.comRoger MedinaE.ON U.S.(502) 627-2997 roger.medina@eon-us.comMichael WinklerE.ON U.S.(502) 627-2338 michael.winkler@eon-us.comDonna HillUWAG(205) 257-5234 dbhill@southernco.comJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@epa.govRon Jordan EPA/Office of Water(202) 566-1003 jordan.ronald@epa.govT.J. Finseth ERG (Contractor to EPA) (703) 994-7130 thomas.finseth@erg.com