Draft Notes from Site Visit at Midwest Genera tion’s EME Homer City Generation Plant on August 22, 2012

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

Plant 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 electric 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: Bituminou s 620 Dry Ash Handling – Combined Vacuum/Pressure System Wet Sluiced None None 1

2 Coal: Bituminou s 614 Dry Ash Handling – Combined Vacuum/Pressure System Wet Sluiced None None 1

3 Coal: Bituminou s 650 Dry Ash Handling – Pressure System Wet Sluiced Wet System None 1 – A dry activated carbon injection system, located upstream of the ESPs, was installed in January 2010 to service units 1 and 2. Plant personnel indicate that th is 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 di scharge 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. These systems are being installed in an ticipation of the pending Mercury and Air Toxics Standard (MATS) Rule. These systems are curren tly under construction with a planned 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 Syst em while Unit 3 uses a pressure system.

 Each unit transfers ash to one of three silos, each generating unit has a dedicated silo. The plant maintains a one-unit-per-silo method for ash collecti on to allow for the shortest transport time and simplicity. Each silo has the capacity to stor e roughly two to three days worth of fly ash.

 Fly ash from each silo is transferred to trucks using a pugmill to moisten the ash to approximately 12 percent moisture. Homer City unloads the fly ash from Units 1 and 2 and 3 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 collects weekly samples of the ash, using a combination of fly ash from all three units. Provided that the mate rial 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 th e ‘Ash Disposal Site’. If the material does not meet beneficial use criteria, the plant manag es the material in the ‘Ash Disposal Site’.

 Homer City personnel stated that the loss of ignition (LOI) in 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, and 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 ash disposal sites. Overflow from the dewatering bins is transferred to a series of settling ponds. The effluent from these ponds is e ither 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. It was de termined that the closed-loop tank-based system currently being installed provided the best so lution for managing all of the various plant interferences associated with the bottom ash system.

 The new bottom ash system is planned to be ope rating 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 major ity of the bottom ash will settle out and be sold as anti-skid material or landfilled. The overflow from the 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 bi ns to remove the solids with the majority of the bottom ash. The 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 th e bottom ash. The overflow from the surge tanks will be transferred to a clearwell and from there it w ill 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 pe rcent redundancy (i.e., one settling tank and one surge tank would have been sufficient to handle th e dewatering bin overflow for all three units). Once construction on the tanks is complete the pl ant 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 w astewater and the bottom ash sluice discharge to Outfall 005 will be sealed.

 Homer City expects that make-up water will need to be added to the system to account for the water remaining in the bottom ash solid, evapora tion, 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 system.

 Homer City does not anticipate any build up of c onstituents or scaling issues within the system and therefore, has no plans to 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 be closed. The space currently occupi ed by these ponds will be used for the new dry FGD systems.
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 system s will be dry lime scrubbers and will include the addition of activated carbon for increased mercury removal. The plant plans to landfill solids produced by the dry FGD systems. These solids will undergo an evaluati on 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 DBA and formic acid were 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 system.

 The chloride 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 hydrocyclones for initial solids separation. The overflow can be transferred to the secondary hydrocyclones or recycled back to the absorber. The underflow is transferred to the vacuum belt filters

.
 From the secondary hydrocyclone, the overflow (i.e., FGD purge) is transferred to the FGD wastewater treatment system, while the underflow is transferred to the vacuum belt filters. NOTE TO HOMER CITY: Please confirm these flow rates.] The flow rate of the FGD purge stream is estimated to occur 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 hydrocyclone is tr ansferred to the vacuum belt filter along with the underflow from the primary hydrocyclone.

 Homer City uses a vacuum belt filter to dewater the gypsum. QUESTION FOR HOMER CITY: To where is the filtrate from the vacuum belt f ilters transferred?] The filtrate from the vacuum belt is transferred to the absorber/reaction tank.

 Dewatered gypsum from the vacuum belt filter is e ither transferred to the ’Coal Refuse Site’ or the ’Ash Disposal Site’. Provided that the mate rial meet beneficial use criteria (which include SPLP analysis) the plant has the option to manage th e 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’. 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 pl ant has been unable to sell gypsum recently.

 Homer City has not conducted any studies on the oxidation reduction potential (ORP) within the scrubber and its effects on the F GD 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 neutra lization tank where 40 ppm ferric chloride and lime slurry are 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 first stage neutralization tank, the wastew ater is sent to the first stage clarifier. A cationic polymer is injected 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 to20 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 slur ry are added to adjust the pH to 7.0 S.U. From the second stage neutralization the wastewat er is sent to the second stage clarifier, where more polymer is added.

 Homer City personnel noted that the second stage clar ifier is operating with an effluent turbidity of 20 to 30 NTU, which is slightly higher than the normal level of 5 to 15 NTU. The plant speculates the increased solids are due to chemical s (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 roughl y 5 feet in the second stage clarifier to help remove the smaller finer particles. During the s ite visit the sludge blanket was approximately 2.5 feet thick. QUESTION FOR HOMER CITY: W as this smaller sludge blanket due to the increased solids in the clarifier?]The sludge thickness was attributed to an older sludge.

 The underflow from the second stage clarifier is co mbined with the underflow from the first stage clarifier and sent to the thickener. The overflow from the thickener is transferred back to the first stage neutralization tank. The thickened solids ar e dewatered by a vacuum drum filter and the solids are hauled to the ‘Ash Disposal Site’. [QUESTION FOR HOMER CITY: To where is the vacuum drum filter filtrate transferred?]The vacuum drum filter filtrate is transferred to the first stage neutralization tank.

 The overflow from the second stage clarifier is sent to a pH adjustment tank, which was previously used to adjust th e 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 existi ng heat exchanger and sent to the biological system, which consists of an aerobic biological r eactor. This system was operated 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, the biological system is not needed. 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 transferre d 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 able 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 concentra tion in the treated FGD wastewater effluent is normally at non-detect levels using EPA Met hod 245.1 [QUESTION TO HOMER CITY: Please confirm the method used to test mercury in the treated FGD wastewater?]. Method confirmed to be EPA Method 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 regarding times when Unit 3 is operating (which generates FGD wastewater) and Unit 1 and/or Unit 2 are not oper ating, 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.Flue Gas Mercury Control (FGMC) Systems

 In January 2010, Homer City installed a dry ups tream activated carbon injection system on Units 1 and 2 to comply with the PA Mercury Ru le. [QUESTION FOR HOMER CITY: Why were these systems installed? What State requirement resulted in the installation of these systems?] The plant has never operated either of these sy stems because the PA 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 resu lting 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 fly ash samp les including the FGMC solids would have still passed the TCLP analysis and therefore, could have been disposed of at the ‘Ash Disposal Site’.

 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 activ e landfills and one retired 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 programs that regulates what type of material can be benefi cially used in the ‘Coal Refuse Site’. Provided that the material meet beneficial use criteria (which include SPLP analysis) the plant has the option to manage the material in either the ‘Coal Re fuse 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’.

 The ‘Ash Disposal Site’ has an underdrain system to collect leachate. The leachate and a portion of the storm water is sent to a leachate treatment system. The landfill runoff from the ‘Ash Disposal Site’ is either sent to the leachate tr eatment system or discharges to the ash landfill’s stormwater outfalls.

 Leachate from the ‘Ash Disposal Site’ is piped direc tly to the leachate treatment system at a rate of roughly 180 gpm. There is no leachate collecti on pond or tank prior to the treatment system. In the first step of the treatment system, caustic is used to raise the pH to 8.9 S.U. The amount of caustic added is based on pH monitoring that occurs at the treatment system influent and effluent. In the second step of the treatment system, the le achate 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 evaluating options to meet these limits from the permit amendment.

 The ‘Coal Refuse Site’ is lined and includes a leach ate collection system. Leachate from the Coal Refuse Site is sent to a separate leachate treatment system (Wastewater Recycle [WWR]). WWR also treats storm water from the ‘Coal Refuse Site’. Homer City personnel stated that coal pile runoff is not treated in WWR; the ‘Coal Refu se 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 system. 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 ‘C oal Refuse Site’ are mixed with lime slurry. The 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 w ith raw intake water. The oxidized iron, along with coagulants, help to precipita te and settle any sediments out of the intake water. The clear combined effluent is then used thr oughout 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, while leachate from the ‘Ash Disposal Site’ is discharged. Additionally, the ‘Coal Refuse Si te 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, Homer City received a permit to expand the site both horizonta lly 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 period during a labor strike at the plant. No new waste is being added to this landfill.Table 2. Site Visit AttendeesNameOrganization (Representing)TelephoneE-mailTom Wilson Homer City Power Plant (724) 479-6140twilson@mwgen.comGary Cline Homer City Station (724) 479-6255gcline@mwgen.comTom Suda Homer City Station (724) 479-6123tsuda@mwgen.comJoe Stanek Homer City Station (724) 479-6256jstanek@mwgen.comJohn DeMarines Homer City Station (724) 479-6237jdemarines@mwgen.comBob Duey Homer City Station (724) 479-6145bduey@mwgen.comJeff Lellock Homer City Station (724) 479-6247jlellock@mwgen.comJim Beninati HDR Engineering (724) 497-6237james.beninati@hdrinc.comJohn VanGehuchten HDR Engineering (724) 497-6236John.vangehuchten@hrdinc.comCassandra Shaw GE EFS (508) 596-9140Cassandra1.shaw@ge.comDonna Hill Southern Company (205) 257-5234dbhill@southernco.comRon Jordan EPA/Office of Water (202) 566-1003Jordan.ronald@epa.govCuc Schroeder EPA/Office of Water (202) 566-2397Schroeder.cuc@epa.govJames Covington EPA/Office of Water (202) 566-1034Covington.james@epa.govT.J. Finseth ERG (Contractor to EPA) (703) 633-1698Thomas.finseth@erg.comDanielle Lewis ERG (Contractor to EPA) (703) 633-1703Danielle.lewis@erg.com