Final Notes from Site Visit at Midwest Generation’s EME Homer City Generation Plant on August 22, 2012
EPA conducted a site visit at Midwest Generation’s EME Homer City Generation Plant (Homer City) located in Homer City, P ennsylvania on Wednesday, August 22, 2012 to learn about operations at the plant and discuss recent upgrades to the FGD and bottom ash systems. These notes describe the information collected during the site visit. Table 2 identifies the site visit participants.

Pla nt Overview

• Homer City operates three electric generating units, all of which are baseload coal

- fired units. The plant ’s net generating capacity is 1,884 MW. The table below contains some general information on the current operation of each steam electri c generating unit.

Table 1

. Steam Electric Generating Unit Operations

SE Unit Fuel Net Capacity

(MW) Fly Ash Bottom Ash FGD Flue Gas Mercury Control

1 Coal: Bituminous 6 20 Dry Ash Handling

– Combined Vacuum/ Pressure System Wet Sluiced None None 1

2 Coal: Bituminous 6 14 Dry Ash Handling

– Combined Vacuum/ Pressure System Wet Sluiced None None 1

3 Coal: Bituminous 6 50 Dry Ash Handling

– Pressure System Wet Sluiced Wet System None
1

– A dry activated carbon injection system , located upstream of the electrostatic precipitator ( ESP )
, was installed in January 2010 to service units 1 and 2. Plant personnel indicate that this system has not been operated since installation.

• Homer City is in the process of upgrading the wet

- bottom ash handling system on all three generating units to a tank

- based system (i.e., no discharge of bottom ash transport water) . This upgrade is currently under construction and is planned to be completed by November 2012.

• Homer City is also in the process of installing two dry lime scrubber systems, one each on units 1 and 2. Thes e systems are being installed in anticipation of the pending Mercury and Air Toxics Standard (MATS) Rule. These systems are currently under construction with a plan ned start

- up date in 2014.

Fly Ash Handling System

• Homer City operates dry fly ash handling systems on all three of its generating units. Units 1 and 2 utilize a combined Vacuum/Pressure system while Unit 3 uses a pressure system.

• Each unit t ransfers ash to one of three silos, each generating unit has a dedicated silo. The plant maintains a one

- unit

- per

- silo method for ash collection to allow for the shortest transport time and simplicity. Each silo has the capacity to store roughly two to three days wor th of fly ash.

• Fly ash from each silo is transferred to truck s using a pugmill to moisten the ash to approximately 12 percent moisture

. Homer City unload s the fly ash from Units 1, 2
, and 3 approximately five to six days per week

.

• Homer City beneficially uses (placement) fly ash at the ‘Coal Refuse Site’ or disposes of fly ash
at the ‘Ash Disposal Site

. ’ Homer City co llects weekly samples of the ash, using a combination of fly ash from all three units. Provided that the material meet benefic ial use criteria (whichPage 2

include Synthetic Precipitation Leaching Procedure [SLPL] analysis) the plant has the option to manage the material in either the ‘Coal Refuse Site’ or the ‘Ash Disposal Site. ’ If the material does not meet beneficial use criteria, the plant manages the material in the ‘Ash Disposal Site. ’

• Homer City personnel stated that t he loss of ignition ( LOI ) i n the fly ash is too high for the ash to be used by the concrete industry ; however, it can be used as structural fill, flowable fill, an d for road construction.

• Homer City does not transport any of the fly ash using dry unloaders (i.e., without moistening the ash using a pugmill).

Bottom Ash Handling System

• Currently the bottom ash from all three units is wet sluiced to dewatering bins. The dewatered

non

- pyritic solids are sold as anti

- skid material. The pyritic bottom ash is managed in either the coal refuse of the ash disposal sites. Overflow from the dewatering bins is transferred to a series of settling ponds. The effluent from these ponds is either reused in the bottom ash sluice system, used to moisten fly ash, or discharged.

• Homer City evaluated several options for achieving zero discharge of bottom ash sluice, including a mechanical drag system . The plant determined that the clos ed

- loop tank

- based system currently being installed provided the best solution for managing all of the various plant interferences associated with the bottom ash system.

• The new bottom ash system is planned to be operating by November 2012 . The new system will continue to use water to sluice the bottom ash from the boiler. The sluice will continue to be collected in the dewatering bins where the majority of the bottom ash will settle out and be sold as anti

- skid material or landfilled. The overflow from t he dewatering bins will then be transferred to a set of settling tanks operating in series with each settling tank

. The underflow from the settling tanks will be sent back to the dewatering bins to remove the solids with the majority of the bottom ash. T he overflow will be routed to a set of surge tanks operated in parallel. Similar to the settling tanks, the underflow from the surge tanks will be sent back to the dewatering bins to remove the solids with the majority of the bottom ash. The overflow from the surge tanks will be transferred to a clearwell and from there it will be recycled back as sluice water or used to moisten the fly ash. A process flow diagram of the new bottom ash system is included as Attachment 1 of this memorandum.

• The set of settling tanks and surge tanks are open topped tanks and were sized by United Conveyor Corporation (UCC) to include 100 percent redundancy (i.e., o ne settling tank and one surge tank would have been sufficient to handle the dewatering bin overflow for all three units)

. Once construction on the tanks is complete the plant will operate both the tank based system and the pond system until the new system can achieve equilibrium. At which point the bottom ash system is designed to require no discharge of wastew ater and the bottom ash sluice discharge to O utfall 005 will be sealed.

• Homer City expects that m ake

- up water will need to be added to the system to account for the water remaining in the bottom ash solid, evaporation, and water used to moisten the fly ash

. Homer City is planning to use stormwater from the area around the bottom ash system as part of the make

- up water for the syste m.

• Homer City does not anticipate any build up of constituents or scaling issues within the system and therefore
, has no plans t o add any chemicals to the system.

• Homer City made no other changes to the bottom ash sluicing system itself (e.g., no changes to the sluice pumps)

.

• Once the new bottom ash system is operating and the settling ponds are no longer needed, the ponds will b e closed. The space currently occupied by these ponds will be used for the new dry FGD systems.Page 3

Flue Gas Desulfurization (FGD) Systems

• Homer City is in the process of installing dry FGD scrubbers on Units 1 and 2. Both units are expected to be operating by 2014. These systems will be dry lime scrubbers and will include the addition of activated carbon for increase d mercury removal. The plant plans to landfill solids produced by the dry FGD systems. These solids will undergo an evaluation to determine which disposal site can be used for management of this material

. Homer City personnel believe that the dry FGD solids could potentially be used as a soil amendment because of its elevated pH.

• Homer City is currently operating a limestone forced oxidation FGD system on Unit 3.

• Homer City personnel indicated that dib asic acid ( DBA ) and formic acid w ere previously added to the wet FGD system to increase the sulfur dioxide removal of the system. Homer City determined that these additives were resulting in some of the selenium to be organically bound
, which is more difficult to remove in the downstream wastewater treatment system. Homer City is no longer using DBA or formic acid in the wet FGD sys tem.

• The c hloride level in the wet FGD system is typically between 14 ,000 to 18,000 ppm.

• Blowdown from the FGD system is transferred to the primary hydro cy clone s for initial solids separation. The overflow can be transferred to the secondary hydro cy clone s or recycled back to the absorber. The underflow is transferred to the vacuum belt filter s

.

• From the secondary hydro cy clone, the overflow (i.e., FGD purge) is transferred to the FGD wastewater treatment system , while the underflow is transferred to the vacuum belt filters . The flow rate of th e FGD purge stream is estimated to occur for 5 to 9 hours twice per day at a rate of 220 gpm

. The typical solids concentration of the FGD purge is two percent (but it ranges from one to four percent ) . Underflow from the secondary hydro cy clone is transferred to the vacuum belt filter along with the underflow from the primary hydro cy clone.

• Homer City uses a vacuum belt filter to dewater the gypsum. The filtrate from the vacuum belt is transferred back to the absor ber.

• Dewatered gypsum from the vacuum belt filter is either transferred to the ’Coal Refuse Site’ or the ’Ash Disposal Site

. ’ Provided that the material meet beneficial use criteria (which include SPLP analysis) the plant has the option to manage the mater ial in either the ‘Coal Refuse Site’ or the ‘Ash Disposal Site. ’ If the material does not meet beneficial use criteria, the plant manages the material in the ‘Ash Disposal Site. ’ Prior to 2008, Homer City was able to sell 100 percent of the gypsum to the wallboard industry. The influx of scrubbers and slow housing market has caused the demand for gypsum to decrease and the plant has been unable to sell gypsum recently.

• Homer City has not conducted any studies on the oxidation reduction potential (ORP) wit hin the scrubber and its effects on the FGD wastewater characteristics

. FGD Wastewater Treatment System

• The FGD purge is transferred to the wastewater treatment feed tank. The water from the feed tank is then transferred to the first stage neutralization tank where 40 ppm ferric chloride and lime slurry a re added to adjust the pH to between 6.8 and 6.9 S.U . Homer City noted that historically it sees better selenium removal at a lower pH.

• From the firs t stage neutralization tank
, the wastewater is sent to the first stage clarifier. A cationic polymer is i njected inline as a coagulant, while an anionic polymer is added to the 1 st stage clarifier center well as a flocculent. Overflow from the clarifier
, which the plant adds 15 to 20 ppm of ferric chloride, is sent to the second stage neutralization tank
, while the underflow is transferred to a thickener

.

• In the second stage neutralization tank more lime slurry is added to adjust the pH to 7.0 S.U

. From the second stage neutralization the wastewater is sent to the second stage clarifier, where more polymer is added.Page 4

• Homer City personnel noted that the second stage clarifier is operating with an effluent turbidity of 20 to 30 NTU, which is slightly hi gher than the normal level of 5 to 15 NTU . The plant speculates the increased solids are due to chemicals (i.e., dispersants) used to treat the cooling
water to allow for additional cycling within the cooling towers . Cooling water is used as FGD make

- up and slurry and reagent preparation water.

• Homer City maintains a sludge blanket of roughly 5 feet in the second stage clarifier to help remove the smaller finer particles. During the site visit the sludge blanket was approximately 2.5 feet thick. Homer Ci ty personnel attributed the smaller sludge blanket to it being an older sludge.

• The underflow from the second stage clarifier is combined with the underflow from the first stage clarifier and sent to the thickener. The overflow from the thickener is transf erred back to the first stage neutralization tank. The thickened solids are dewatered by a vacuum drum filter and the solids are hauled to the ‘Ash Disposal Site

. ’ The vacuum drum filtrate is transferred to the first stage neutralization tank.

• The o verfl ow from the second stage clarifier is sent to a pH adjustment tank , which was previously used to adjust the pH prior to the downstream biological treatment system. Homer City no longer operates the biological treatment system as the system was designed and therefore, Homer City no longer adds any chemicals to the pH adjustment tank

.

• The wastewater is then bypassed around the existing heat exchanger and sent to the biological system, which consists of an aerobic biological reactor. This system was operate d to remove the organic content in the wastewater added from the organic acids (i.e., DBA/formic acid) as well as the biochemical oxygen demand (BOD) present . Because Homer City no longer adds organic acid to the FGD system , th e biological system is not n eeded. Homer City still transfers the wastewater to the reactor and aerates the system

. Solids accumulated in the biological reactor are transferred to the thickener and handled with the clarifier solids.

• Effluent from the biological reactor is transferred to sand filters and then onto the effluent tank and discharged. Filter backwash from the sand filters is recycled back to the initial wastewater feed tank.

• Using the two stage chemical precipitation system, Homer City indicated that they are a ble to achieve over 90% removal of selenium (from 7 ppm to 0.5 ppm). For the most part
, only soluble selenium remains in the treated effluent.

• Homer City indicated that the mercury concentration in the treated FGD wastewater effluent is normally at non

- detect levels using EPA M ethod 245.1

.

• Homer City has not yet evaluated whether the treated FGD wastewater could be used as make up for the dry FGD systems to eliminate the FGD discharge; however, Homer City personnel stated that there are concerns regardi ng times when Unit 3 is operating (which generates FGD wastewater) and Unit 1 and/or Unit 2 are not operating, in which case some or all of the FGD wastewater would need to be discharged because one or both of the dry FGD systems would not be operating.

F lue Gas Mercury Control (FGMC) Systems

• In January 2010, Homer City installed a dry upstream activated carbon injection system on Units 1 and 2 to comply with the Pennsylvania Mercury Rule

. The plant has never operated either of these systems because the Pennsylvania Mercury Rule requirement was not upheld.

• Homer City indicated that no changes were made to the ash handling system as a result of the added FGMC systems. The added solids resulting from the FGMC system would have been minimal
, resulting in no need for added storage space in the silos.

• Homer City had expected that the f ly ash samples including the FGMC solids would have still passed the toxicity characteristic leaching procedure ( TCLP ) analysis and therefore, could have been disposed of at the ‘Ash Disposal Site

. ’Page 5

• The dry lime scrubbers being installed on Units 1 and 2 will include the injection of activated carbon to control mercury.

Landfills and Leachate Treatment Systems

• Homer City operates three landfills. Two active landfills and one ret ired landfill. The active landfills are referred to as the ‘Ash Disposal Site’ and the ‘Coal Refuse Site. ’ The retired landfill is known as the ‘ Strike Pile. ’

• The ‘Ash Disposal Site’ receives fly ash, bottom ash, and calcium sulfate ( synthetic gypsum), in addition to other plant solids. The ‘Coal Refuse Site’ receives fly ash, bottom ash, and calcium sulfate ( synthetic gypsum), as well as coal refuse. The State of Pennsylvania maintain s programs that regulates what type of material can be beneficially us ed in the ‘Coal Refuse Site

. ’ Provided that the material meet beneficial use criteria (which include synthetic precipitation leaching procedure ( SPLP ) analysis) the plant has the option to manage the material in either the ‘Coal Refuse Site’ or the ‘Ash D isposal Site. ’ If the material does not meet beneficial use criteria, the plant manages the material in the ‘Ash Disposal Site. ’

• The ‘Ash Disposal Site’ has an underdrain system to collect leachate. The leachate and a portion of the storm water is sent t o a leachate treatment system. Landfill runoff from the ‘Ash Disposal Site’ is either sent to the leachate treatment system or discharges to the ash landfill’s stormwater outfalls

.

• Leachate from the ‘Ash Disposal Site’ is piped directly to the leachate treatment system at a rate of roughly 180 gpm. There is no leachate collection pond or tank prior to the treatment system. In the first step of the treatment system
, c austic is used to raise the pH to 8.9 S.U . The amount of caustic added is based on pH m onitoring that occurs at the treatment system influent and effluent. In the second step of the treatment system, the leachate is transferred to a flocculation tank where a gel polymer is added. The treated effluent is sent to one of two settling ponds. Both settling ponds discharge to a single polishing pond. Treated leachate from the polishing pond is discharged via plant Outfall 004.

• The treatment system for leachate from the ‘Ash Disposal Site’ targets iron and manganese

. Recent permit amendments added new constituents to the limits to include arsenic, boron, nickel, and thallium. These additional limits are water quality based limits. Homer City expects that additional treatment will be needed to meet the limits; however, the plant is currently e valuating options to meet these limits from the permit amendment

.

• The ‘Coal Refuse Site’ is lined and includes a leachate collection system. Leachate from the Coal Refuse Site is sent to a separate leachate treatment system (Wastewater Recycle [WWR])

. WWR also treat s stormwater from the ‘Coal Refuse Site

. ’ Homer City personnel stated that coal pile runoff is not treated in WWR ; the ‘Coal Refuse Site’ and coal pile are separate entities.

• Leachate from the ‘Coal Refuse Site’ is collected in a series of six ponds prior to entering the treatment systems. Leachate feeds by gravity from one pond to the next and is then pumped to the leachate treatment system (WWR)

.

• The commingled leachate and stormwater from the ‘Coal Refuse Site’ are mixed with lime slurry. T he target pH of the system is 8.5 S.U . Air is added to the system to encourage iron to oxidize and convert from the ferrous oxidation state (Fe 2+ ) to the ferric oxidation state (Fe 3+ ) . The aerated stream is sent to a clarifier where it is mixed with raw intake water. The oxidized iron, along with coagulants, help to precipit ate and settle any sediment s out of the intake water . The clear combined effluent is then used throughout the plant as make

- up water

.

• Homer City cited the final destination of each stream as the reason for the different treatment methods. Leachate from the ‘Coal Refuse Site’ is used to help treat the plant intake and then used as make

- up water for various processes within the plant
, whi le leachate from the ‘Ash DisposalPage 6

Site’ is discharged. Additionally, the ‘Coal Refuse Site’ is larger than the ‘Ash Disposal Site’ and produces roughly twice as much leachate.

• The permit for the ‘Ash Disposal Site’ expires in 2013. On October 1, 2012, Ho mer City received a permit to expand the site both horizontally and vertically. The State of Pennsylvania requires that the expansion include a synthetic liner.

• The ‘Strike Pile’ is the plant’s retired landfill. This landfill was only used for a 108

- day p eriod during a labor strike at the plant. No new waste is being added to this landfill.Page 7

Table 2 . Site Visit Attendees

Name Organization (Representing) Telephone E

- mail

Tom Wilson Homer City Power Plant (724) 479

- 6140 twilson@mwgen.com

Gary Cline Homer City Station (724) 479

- 6255 gcline@mwgen.com

Tom Suda Homer City Station (724) 479

- 6123 tsuda@mwgen.com

Joe Stanek Homer City Station (724) 479

- 6256 jstanek@mwgen.com

John DeMarines Homer City Station (724) 479

- 6237 jdemarines@mwgen.com

Bob Duey Homer City Station (724) 479

- 6145 bduey@mwgen.com

Jeff Lellock Homer City Station (724) 479

- 6247 jlellock@mwgen.com

Jim Beninati HDR Engineering (724) 497

- 6237 james.beninati@hdrinc.com

John VanGehuchten HDR Engineering (724) 497

- 6236 John.vangehuchten@hrdinc.com

Cassandra Shaw GE EFS (508) 596

- 9140 Cassandra1.shaw@ge.com

Donna Hill Southern Company (205) 257

- 5234 dbhill@southernco.com

Ron Jordan EPA/Office of Water (202) 566

- 1003 Jordan.ronald@epa.gov

Cuc Schroeder EPA/Office of Water (202) 566

- 2397 Schroeder.cuc@epa.gov

James Covington EPA/Office of Water (202) 566

- 1034 Covington.james@epa.gov

T.J. Finseth ERG (Contractor to EPA) (703) 633

- 1698 Thomas.finseth@erg.com

Danielle Lewis ERG (Contractor to EPA) (703) 633

- 1703 Danielle.lewis@erg.com