Final Notes from Site Visit at 

Louisville Gas & Electric Company’s Trimble County Station 

on December 10, 2008 

EPA conducted a site visit at Louisville Gas & Electric Company’s Trimble County Station 

(Trimble County) located in Bedford, Kentucky on December 10, 2008 to learn about the 

operations at the plant, specifically the FGD wastewater handling system. 

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

call, which was held on November 19, 2008. Attached to this document are the following: 

(1) List of site visit participants; 

(2) Presentation that the Trimble County personnel gave during the site visit; 

(3) Labeled and unlabeled aerial photographs of the plant; 

(4) Plant water balance diagram; 

(5) Simplified plant overview process flow diagrams for the current operation of generating 

unit 1 and the proposed operation of generating units 1 and 2; 

(6) Simplified process flow diagrams for the Unit 1 FGD system and the planned Unit 2 

FGD system; and 

(7) Graph showing buildup of chlorides in the FGD reaction tank, followed by graph 

showing buildup of chlorides in the ash pond. 

Plant Overview 

 Trimble County operates one coal-fired generating unit at the power plant, which 

is a baseload unit with a net generating capacity of 515 MW. A second unit is 

currently under construction at Trimble County, which is expected to begin 

commercial operation in June 2010. This second unit will have a net generating 

capacity of 760 MW. The table below contains some general information for the 

two generating units. A process flow diagram for the existing operation of Unit 1 

and the proposed operation of Units 1 and 2 are included as attachments to this 

memorandum. 

Unit 

Installation 

Date 

Capacity 

(MW) 

Particulate 

Control NOx Control SO2 Control 

1 1990 566 ESP (cold-side) SCR, low-NOx 

burners and 

overfire air

Wet FGD in original 

design (1990) 

2 

(planned) 

Expected 

2010 

810 ESP (cold-side) SCR, low-NOx 

burners and 

overfire air

Wet FGD in original 

design (2010) 

 The Unit 1 boiler is a subcritical boiler, which converts 33.5 percent of the energy 

in the coal to electricity. The planned Unit 2 boiler will be a supercritical boiler, 

which is expected to convert approximately 40 percent of the energy in the coal to 

electricity. 
Page 2 

 Ultra supercritical boilers also exist in the industry and these typically convert 50 

percent of the energy in coal to electricity. Trimble County stated that they do not 

expect any more subcritical boilers to be built. 

 Trimble County burns eastern bituminous coal in Unit 1. The plant burns 

approximately 1.6 million tons of coal per year. The coal comes from the Illinois 

basin and is mostly mined in Kentucky, Indiana, southern Ohio, West Virginia, 

and Illinois. All of the coal is delivered via barge on the Ohio River. 

 When Unit 2 begins operating, the unit will burn a mixture of 70 percent eastern 

bituminous and 30 percent Powder River Basin (PRB) coal. The PRB coal will 

be used to lower the total sulfur content of the coal burned. The lower sulfur coal 

is needed because Unit 2 has a stricter SO2 emission limit (i.e., 3,263 tons 

SO2/year for Unit 2 versus 4,822 tons SO2/year for Unit 1). 

 Trimble County is currently building a coal blending facility at the site to blend 

the eastern bituminous and PRB coals. The blending facility will consist of a 

conveyer system with weight belt feeders. 

 Trimble County occasionally burns a deslagging coal which helps with slagging 

issues in the boiler. The deslagging coal is a “middlings” coal and is generally 

high ash (25-35%), lower sulfur (1%), and low BTU (9,000-10,500 BTU) with a 

high ash fusion temperature. The coal is mined in Eastern Kentucky and West 

Virginia. 

 The sulfur content of the coal used at Trimble County typically ranges from 5.5 to 

6.5 lbs SO2/mmBTU, but Trimble County has received some coal that is 7 lbs 

SO2/mmBTU. 

 Trimble County stated that the chlorine content of the coal is typically 300-700 

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, Trimble County personnel collected four samples from the 

coal pile runoff pond and measured the pH and temperature. The table below 

presents the results of the measurements. 

Date pH (S.U.) Temperature (oC) 

11/19/2008 7.92 7.7 

11/26/2008 7.99 5.8 

12/3/2008 7.88 4.3 

12/8/2008 7.75 2.7 

 Trimble County operates a SCR system on Unit 1. Prior to December 2008, 

Trimble County operated the SCR only during the ozone season. Because of the 
Page 3 

uncertainty of CAIR, Trimble County resumed operation of the SCR in December 

2008 and plans to operate it year round. 

 Trimble County uses the Ohio River as the source for the power plant’s water. 

Trimble County operates a recirculating mechanical draft cooling tower for Unit 

1. Trimble County Unit 1 used to utilize a natural draft hyperbolic cooling tower, 

but the tower wouldn’t have the capacity to handle the cooling water for both Unit 

1 and the new Unit 2. Therefore, Trimble County built a mechanical draft cooling 

tower, which is now used for the Unit 1 cooling water. Trimble County will use 

the natural draft hyperbolic cooling tower for Unit 2 when it begins operating. 

 The cooling tower blowdown from Unit 1 is discharged directly to the Ohio 

River. The Unit 2 cooling tower blowdown will also be discharged directly to the 

Ohio River. 

 Trimble County also operates six combustion turbines, which each have a 

capacity of approximately 160 MW. The capacity of the combustion turbines 

changes with the seasons. The capacity is larger in the winter because the air is 

denser and therefore, more fuel can be burned efficiently with the same volume of 

air. In the summer, Trimble County can use evaporative cooling water to cool the 

air at the intake, prior to the compressor, which causes the inlet air to become 

more dense, thereby allowing more fuel to be efficiently burned which results in 

an increase in capacity. 

 Illinois Municipal Electric Agency owns 12.12 percent of the Trimble County 

coal-fired units and Indiana Municipal Power Agency owns 12.88 percent of the 

coal-fired units. Louisville Gas & Electric Company and Kentucky Utilities 

Company own the remaining 75 percent of the coal-fired units, 100% of the 

combustion turbines and manage all plant operations. 

 The Trimble County plant is located on approximately 2,250 acres of land, 

including a 114-acre wildlife preserve. 

 Trimble County employs approximately 125 workers. 

Unit 1 FGD System (Current Operation) 

 Trimble County operates a limestone, forced oxidation wet FGD scrubber on Unit 

1. Process flow diagrams for the Unit 1 FGD system and the planned Unit 2 FGD 

system are included as an attachment to this memorandum. 

 Trimble County uses large, horizontal ball mills to crush the limestone to the 

correct size for use in the limestone slurry. Water from the ash treatment basin is 

used to prepare the limestone slurry. 

 Trimble County uses approximately 185,000 tons of limestone each year (dry 

basis). The limestone is delivered to the plant via barge. 
Page 4 

 The Unit 1 FGD system began operating in 1990, when the plant began operating. 

The FGD system has four absorber modules. Each of the four modules has five 

recirculation pumps, each with a designated elevation of spray header nozzles. 

There are two reaction tanks for the four modules (two modules per reaction 

tank). 

 Trimble County has the capability of adding dibasic acid (DBA) or equivalent 

organic acid to the Unit 1 FGD system to increase the sulfur dioxide removal 

efficiency, but the plant has not used DBA in the system. Its use has never been 

required to meet permit compliance levels. The new Unit 2 FGD system was 

designed to meet compliance requirements without the use of DBA. 

 Trimble County stated that when the FGD system was built for Unit 1, it was 

considered a 3rd-generation design capable of high removals with all pumps 

running but intended for compliance at lower removal levels with some 

equipment redundancy. Through equipment changes using the existing 

equipment installed on-site, the plant recently upgraded the system to optimize the 

sulfur dioxide removal. The upgrade included the following: 

o Optimizing the liquid to gas (L/G) ratio; 

o Replacing some spray header nozzles with bidirectional spray nozzles; 

o Inserting a ring between the spray levels which forces the flue gas up the 

middle of the scrubber and prevents gas sneakage up the module walls; 

o Changing the angle at which the flue gas enters the scrubber; and 

o Removing pluggage in the spray headers. 

 The system upgrade improved the FGD equipment reliability by reducing spray 

nozzle pluggage and gas flow imbalances. This assures that sulfur dioxide 

removal efficiency can be reliably achieved at levels of 98 percent. 

 Trimble County continuously runs the blowdown pumps for each of the FGD’s 

two reaction tanks. Most of the time the blowdown is sent to a 3rd Party gypsum 

marketer for shipment to a wallboard manufacturing plant. On the infrequent 

occasions when slurry is not sent to the gypsum marketer, it is transferred to the 

ash treatment basin. The solids in the reaction tank are controlled to between 13 

and 17 percent solids. Limestone slurry is added to the reaction tank to control 

the pH to between 5.5 and 5.8. To make up for the evaporative water loss in the 

scrubber and to control the level in the reaction tank, Trimble County adds water 

from the ash treatment basin to the reaction tank. 

 Trimble County stated that the Unit 1 FGD was designed for a maximum 

chlorides concentration of 5,000 ppm. Trimble County stated that the chlorides in 

the FGD system have been building up because the plant is recycling all the FGD 

water and does not have a chlorides purge from the system. A graph presenting 

the chlorides concentration in the Unit 1 reaction tanks over time is included as an 

attachment to this memorandum. 

 Trimble County sells most of the gypsum that is produced in the FGD process to a 

gypsum marketer who then provides it to a wallboard manufacturer. Trimble 
Page 5 

County recently reached an agreement with the same gypsum marketer to provide 

a wallboard manufacturer with at least 350,000 tons of gypsum per year for 20 

years. For the wallboard manufacturer to accept the gypsum, the gypsum must 

contain a minimum of 93 percent gypsum solids. [CBI information has been 

removed from this document.] 

 The blowdown from the scrubber is either transferred directly to the ash treatment 

basin or to the hydroclone feed tank. Because the gypsum marketer does not take 

100% of the gypsum produced by the Unit 1 FGD, the plant transfers the amount 

the gypsum marketer will take to the hydroclones for dewatering. The quantity 

that is not used by the gypsum marketer is diverted to the ash treatment basin. 

 The slurry in the hydroclone feed tank is transferred to the hydroclones. The 

overflow from the hydroclones is transferred to the ash treatment basin. The 

underflow from the hydroclones is transferred to the vacuum belt filters. Trimble 

County washes the gypsum with service water as it is applied to the vacuum belt 

filter to reduce the chlorides concentration in the gypsum. Trimble County also 

operates a steam heater box on the vacuum belt filter, which reduces the chlorides 

concentration and helps dry the gypsum. 

 The gypsum from the vacuum belt filters is approximately 8.5 percent moisture. 

The gypsum is trucked from the plant to the wallboard manufacturer. Trimble 

County has typically produced approximately 250,000 dry tons of gypsum per 

year. On average, they have been able to market approximately 230,000 tons per 

year. 

 

 The filtrate from the vacuum belt filters is transferred to the ash treatment basin. 

 In the ash treatment basin, the FGD wastewaters are mixed with ash sluice, 

effluent from the coal and limestone pile runoff ponds, pyritic mill reject sluice, 

and low-volume wastewaters. 

 Trimble County stated that the chlorides concentration in the ash treatment basin 

is gradually increasing and therefore, continued operation of the basin by current 

practices is unsustainable. The current chlorides concentration is approximately 

2,500 ppm. A graph presenting the chlorides concentration in the ash treatment 

basin over time is included as an attachment. 

Ash Handling and Wastewater Treatment (Current Operation) 

 Trimble County operates a cold-side electrostatic precipitator (ESP) on Unit 1. 

 Trimble County injects hydrated lime into the Unit 1 flue gas before and after the 

ESP to remove the sulfur trioxide from the flue gas, which reduces the blue plume 

from the stack. The sulfur trioxide is generated in the SCR when the catalyst 

converts sulfur dioxide to sulfur trioxide. Trimble County adds the hydrated lime 

before and after the ESP to capture as much of the sulfur trioxide as possible. 
Page 6 

 Trimble County estimates that approximately 149,000 tons of fly ash is generated 

each year from operation of Unit 1. Trimble County operates both a wet and dry 

fly ash handling system. The fly ash is handled dry when it is marketable. 

Typically, Trimble County is able to market approximately 8,000 tons of fly ash 

per year because there isn’t always a buyer for the fly ash. Therefore, the plant 

typically operates the wet fly ash handling system, which sluices the fly ash to the 

ash treatment basin. 

 Trimble County estimates that approximately 37,000 tons of bottom ash are 

generated each year from the operation of Unit 1. Trimble County operates a wet 

bottom ash handling system. The bottom ash sluice is transferred to the ash 

treatment basin. A vendor classifies the bottom ash by size using a sieve 

operation and markets approximately 13,000 tons of the bottom ash per year. 

 The ash treatment basin also receives FGD wastewaters, effluent from the coal 

and limestone pile runoff pond, pyritic mill reject sluice water, and other lowvolume wastewaters. 

 All overflow from the ash treatment basin is recycled for use as either bottom/fly 

ash sluice make-up water, FGD make-up water, or pyritic mill reject sluice makeup water. There is no discharge from the ash treatment basin. 

 Because the FGD process has large evaporative losses, the FGD process 

consumes a large portion of the water from the ash treatment basin. 

 The ash treatment basin was originally 60 to 70 feet deep when it was built. Now, 

the area where the ash enters the basin in only about 10 to 20 feet deep. The area 

where the wastewater leaves the pond is still about 60 feet deep. Trimble County 

expects that there are only a few years of capacity remaining in the ash treatment 

basin. 

 As a short-term solution to extend the lifetime of the basin, Trimble County plans 

to complete building up the sides of the ash pond as originally designed including: 

vertical extension of the existing clay liner; engineered structural support using 

on-site soils and as much beneficial reuse of excavated bottom ash as practical. 

Trimble County estimates that this will add at least a couple years to the life of the 

pond. 

 As a long-term solution for the disposal of ash and gypsum at the plant, Trimble 

County has plans to use two ravines near the plant. The ravines may be used as 

either landfills or impoundments for the disposal of gypsum and ash. One of the 

ravines would be used exclusively for gypsum and the other would be used 

exclusively for ash, although these plans are subject to change. 

Generating Unit #2 (Under Construction) 

 Trimble County is currently constructing a new generating unit (Unit 2) that is 

planned to begin operation in May 2010. The unit will have a capacity of 

approximately 810 (gross) MW. 
Page 7 

 As described previously, the unit will have a supercritical boiler. Additionally, 

the unit will have a bottom ash handling system that operates with a drag chain. 

The bottom ash will be collected in a trough of water at the bottom of the boiler 

and a drag chain will move across the trough and convey the ash out of the boiler 

to a collection point. 

 Unit 2 will have a SCR and a cold-side ESP. Trimble County will add hydrated 

lime into the flue gas prior to the ESP to remove sulfur trioxide, but will not add it 

after the ESP. Instead, Trimble County will inject powdered activated carbon 

(PAC) into the flue gas after the ESP. The PAC will absorb some of the mercury 

in the flue gas. The flue gas will be sent through a fabric filter baghouse, which 

will capture the PAC and the mercury absorbed with it, reducing the plant’s 

mercury emissions. 

 Trimble County stated that they had originally planned to only operate the 

baghouse for particulate control; however, because the fly ash captured in the 

baghouse would contain PAC and mercury, the fly ash would not be marketable. 

Therefore, Trimble County decided to add the ESP prior to the baghouse to allow 

for most of the fly ash to be marketed, if possible. The addition of the ESP also 

reduced the size of the baghouse required. 

 Trimble County is currently revising the approach for handling fly ash and 

anticipates that both Unit 1 and 2 ultimately will operate dry fly ash systems. The 

system being considered at the time of the site visit, as represented by the attached 

process flow diagrams, is as follows: 

 Both a wet and dry fly ash handling systems would be installed for the fly 

ash collected from the Unit 2 ESP. Similar to Unit 1, the dry handling 

system would be used if there is an opportunity to market the fly ash and 

the wet handling system will be used when marketing is not possible. The 

fly ash sluice would be transferred to the ash treatment basin. If handled 

dry, it would be placed in an on-site landfill. 

 Fly ash collected from the Unit 2 baghouse would be handled wet. 

Because the fly ash collected in the baghouse will contain PAC that has 

absorbed mercury, the fly ash will not be marketable. The fly ash sluice 

would be transferred to the ash treatment basin. If handled dry, it would be 

placed in an on-site landfill. 

 After passing through the fabric filter, the flue gas will be sent to a wet FGD 

scrubber system, which will be a limestone, forced oxidation system. The FGD 

system will have only one absorber module with five spray levels. The designed 

sulfur dioxide removal from the FGD system is 98.5 percent. 

 After the FGD system, the flue gas will pass through a wet ESP (a separate ESP 

from the dry ESP located upstream of the baghouse). The wet ESP uses spray 

headers to remove the collected fine particulate from the collection plates. The 

water stream from the wet ESP will be transferred to the FGD system. Service 

water will be used as the source water for the wet ESP. 
Page 8 

 Trimble County stated that the wet ESP is intended for sulfuric acid mist 

mitigation and it is possible it may also help with capturing mercury. 

Future FGD System Operation (Units 1 & 2) 

 When Unit 2 begins operating, Trimble County will also begin operating a 

gypsum storage pond. Trimble County will be relining the area next to the ash 

treatment basin, which was originally intended to collect emergency overflow 

from the treatment basin, for use as the gypsum storage pond. 

 At the time of the site visit, Trimble County intended to use the ash treatment 

basin as the source water for the limestone slurry, which feeds both of the FGD 

systems. However, the plant now plans to use service water as the source of 

makeup water. 

 The blowdown from the Unit 1 and Unit 2 FGDs will either be transferred to the 

hydroclone feed tank or directly to the gypsum storage pond, depending on how 

much gypsum can be marketed. 

 The slurry (reaction tank blowdown) from the hydroclone feed tank will be 

transferred to the hydroclones and the hydroclone overflow will be recycled to 

Unit 2 as make-up water. None of the hydroclone overflow is planned to be used 

as make up for Unit 1. Currently, the plant anticipates using service water for 

makeup. (At the time of the site visit, the ash treatment basin was expected to be 

the makeup water source for Unit 1.) 

 The hydroclone underflow will be transferred to the vacuum belt filters for 

dewatering. The filtrate from the vacuum belt filters will be transferred to the 

gypsum storage pond. 

 Because of the issue with the increasing chlorides concentration in the Unit 1 

reaction tanks, Trimble County will no longer recycle all of the FGD wastewater. 

Instead, the effluent from the gypsum storage pond will be commingled with 

cooling tower blowdown and discharged to the Ohio River. This discharge will 

purge chlorides from the FGD system. 

 None of the water entering the gypsum storage pond will be recycled back to the 

FGD process. 

 At the time of the site visit, Trimble County estimated that the gypsum storage 

pond effluent would have a flow rate of 1.7 MGD with both units operating. 

However, Trimble County has made a recent change in the plant water 

management design strategy. Trimble County no longer plans to reuse the ash 

treatment basin water as make-up in the FGD systems. Trimble County is still 

evaluating the reconfiguration of the water management design, but the plant 

expects the flow rate from the gypsum storage pond to be greater than 1.7 MGD 

for the following reasons: 
Page 9 

 Increase in freshwater use for the two FGD systems (related to the 

decrease in recycled ash treatment basin water); 

 Increase in evaporation losses (for two FGDs instead of one); 

 Addition of coal pile and limestone pile runoff to the gypsum pond; and 

 Addition of new storm water accumulated in the gypsum pond. 

 
Page 10 

 Site Visit Attendees 

Name Organization (Representing) Telephone E-Tom Crutcher Louisville Gas & Electric – Trimble County (502) 627-6201 tom.crutcher@John Kipfer Louisville Gas & Electric – Trimble County (502) 627-6212 john.kipfer@eWesley Moll Louisville Gas & Electric – Trimble County (502) 627-6202 wesley.moll@Mitch Slaughter Louisville Gas & Electric – Trimble County (502) 627-6208 mitch.slaughteSharon Dodson E.ON U.S. (502) 627-2940 sharon.dodsonRoger Medina E.ON U.S. (502) 627-2997 roger.medina@Michael Winkler E.ON U.S. (502) 627-2338 michael.winkleDonna Hill UWAG (205) 257-5234 dbhill@southeJosh Hall EPA/Office of Water (202) 566-1002 hall.josh@epaRon Jordan EPA/Office of Water (202) 566-1003 jordan.ronald@T.J. Finseth ERG (Contractor to EPA) (703) 994-7130 thomas.finseth
















0.0

1000.02000.03000.04000.05000.06000.07000.0

07/22/91

07/13/92

07/12/93

08/15/94

08/14/95

08/19/96

10/13/97

11/09/98

05/24/99

08/30/99

11/30/99

03/14/00

06/05/00

08/28/00

01/15/01

04/23/01

07/23/01

07/22/02

07/14/03

08/09/04

06/20/05

12/13/05

02/27/06

05/22/06

08/21/06

11/13/06

02/12/07

05/14/07

08/09/07

Chloride Concentration (mg/L)

A Rx Tk ClB Rx Tk Cl
0

500

100015002000250030003500

07/22/91 01/15/92 07/13/92 01/11/93 07/12/93 02/07/94 08/15/94 02/06/95 08/14/95 02/12/96 08/19/96 04/08/97 10/13/97 05/04/98 11/09/98 04/13/99 05/24/99 07/19/99 08/30/99 10/19/99 11/30/99 1/25/200 03/14/00 04/28/00 06/05/00 07/18/00 08/28/00 11/27/

0

Chloride Concentration (mg/L)