### MEMORANDUM

TO: Ron Jordan, EPA

FROM: TJ Finseth, ERG

DATE: 24 May 2007

SUBJECT: Notes from Site Visit at Tampa El ectric Company’s Big Bend Station on April 27, 2007

EPA conducted a site visit at Tampa Electric Co mpany’s Big Bend power plant on Friday, April 27, 2007 to learn about the operations at the plan t and determine where and how samples would be collected if the plant was selected for sampling. Table 2, at the end of this memorandum, identifies the participants at the site visit.

This memorandum summarizes the information colle cted during the site vi sit and the pre-site visit phone call, which was held on April 23, 2007.

Plant Study

Plant personnel noted that they are in the process of installing SCRs on each of the four units over the next few years; the SCR on Unit 4 begins operation in the next couple of weeks. As part of their NPDES permit modification, they will be conducting a study over the next nine months to assess the impact of the installation of the Unit 4 SCR on wastewater characteristics. The plant will collect wastewater samples at se veral points throughout th e process including the FGD make-up water, FGD blowdown prior to tr eatment, FGD wastewater treatment effluent, and intake cooling water. The plant will an alyze the waste streams for nitrogen, ammonia, mercury (low-level), and flow. Table 1 below shows which anlaytes will be analyzed at each sampling point.

Table 1. Sampling Points and Analytes for the Big Bend Wastewater Study

Parameter FGD Make-up FGD Blowdown

Prior to Treatment FGD Wastewater

Treatment Effluent Intake Cooling

Water Ammonia (as N) X X Nitrogen, Total (as N) X X Mercury, Total X X X

Flow X X

Although ammonia is added to the SCR, the plan t theorizes that nitrogen load s in the FGD wastewater drop when an SCR is operating (fro m about 400 mg/L without the SCR in operation to 100 mg/L with the SCR in operation). However, because some of the sulfur dioxide in the flue gas is converted to sulfur trioxide in the SCR, the plant in tends to inject ammonia into the flue gas downstream of the SCR and upstream of th e air preheater, ESP, a nd FGD. In fact, theMay 24, 2007 Page 2

plant intends to add excess ammonia to the flue ga s. The ammonia and sulfur trioxide will react to form ammonium sulfate. Althought the plant expects the majority of the ammonium sulfate to be removed by the ESP, they expect that some of the ammonium sulf ate will pass through the

ESP and be transferred to the wastewater in the FGD system. The study will determine the resulting wastewater characteristics associated with operation of the SCR and determine the nitrogen species present. If possible, they will determine if denitrification will be necessary.

The plant stated that they could provide the study data to EPA in lieu of EPA sampling the plant.

EPA stated that there could be some issues wi th the timing of the plant’s study and when EPA

would need the results to make decisions for the detailed st udy. In addition, the plant’s study may not cover all the analytes and wast e streams that EPA intends to sample.

Plant Overview

• There are 4 units at the Big Bend plant. Unit 1 began operation in 1970, Unit 2 in 1973, Unit 3 in 1976, and Unit 4 in January of 1985. Units 1 and 2 are each rated at 445 MW, Unit 3 is rated at 465 MW, and Unit 4 is rated at 485 MW.

• All 4 units have ESPs.

• Each of the 4 units is scrubbed, by one of two FGD systems. The plant has one FGD scrubber system for Units 1 and 2 (began operation 1/1/2000), and one FGD scrubber system for Units 3 and 4 (began scrubbing Unit 4 in 1985 and Unit 3 in 1995).

• Currently none of the units have SCRs operating, but the plant will begin operating the Unit 4 SCR within the next couple weeks. The plant intends to install one new SCR each year until all f our units have SCRs. All of the SCR units, once installed, will operate yea r-round. The plant estimates that the NO

x emissions will be reduced by approximately 89% (based on 1998 levels) once all four are operating.

• The plant estimates that the improvements to the scrubber, ESPs, and the addition

of the SCRs will reduce the SO 2 emissions by 89%, th e particulate matter emissions by 72%, and the mercury emissions by 78% (all based on 1998 levels).

• The plant burns approximately 4 to 5 million tons of coal per year. The coal is

eastern bituminous and comes from Kentucky. The coal used in Unit 4 is Illinois

Number 6. The coal contains approximately 5 pounds of SO 2 per million BTU. The plant is permitted to blend 20 percent petroleum coke with the coal; however, they typically burn around 1 to 2 percent petroleum coke, with a maximum of 5 percent petroleum coke.

• According to the plant, the use of anhydrous ammonia to control SO 3 emissions (originating from SCR operat ion) is not typical of th e industry. Most plants do

not use ammonia because it sticks to the fly ash and therefore, the fly ash cannot be sold. The Big Bend plant is planning to build a fly ash beneficiation plant that will strip the ammonia from the fly ash a nd return it back to the plant. In addition, the remaining carbon in the fly ash will be stripped from the fly ash inerts. The resulting fly ash inerts will be marketable.May 24, 2007 Page 3

• The plant operates a dry fly ash handling system and currently sells approximately 99 percent of the fly ash produced.

• Unit 4 has a dry bottom boiler. The bottom ash from the other units is sent to the bottom ash ponds. The plant sells the slag and bottom ash from the plant.

• The plant has installed hydrobins to separa te the bottom ash from the sluice water; however, they are not currently operating. The plant intends to begin operating them in the next 4 to 6 months. The plan t stated that most of the water will be reused for sluicing and some may go the plant’s pond system.

• All four units generating units have a once-through cooling water system. The plant uses approximately 1,300 MGD of cooling water combined for all four units. The plant pulls cooling water from the intake canal, uses it to condense steam, and discharges it to the discharg e canal. The plant does not perform any type of biofouling control.

• The Tampa Bay Desalination plant is locate d next door to the power plant. The desalination plant pulls wate r from Big Bend’s intake can al and discharges to Big Bend’s discharge canal. The discharg e is downstream of the Big Bend’s monitoring location.

• The plant is currently working on several projects to improve the environmental impacts from the plant. As mentione d previously, the pl ant has installed hydrobins and will begin operating them in Fall 2007. The current slag pond will be used for stormwater collection. The pl ant is also working to line the existing unlined ponds. In addition, the plant is upgrading the gypsum storage area.

FGD System and Wastewater Treatment System

• The scrubber system for Units 3 and 4 wa s initially designed only for Unit 4 for compliance with NSPS. It is a limestone , forced oxidation system. The scrubber design is old and consists of a double loop, spray/tray tower and is not typical of the newer scrubbers being in stalled. The scrubber was modified to be used for both Units 3 and 4, including the use of DBA as an additive. There are four individual scrubber towers for the syst em. When the scrubber was initially designed only three of the four towers we re intended to operate at one time (with the fourth used as a spare), but when Un it 3 started being scrubbed in the system, all four towers needed to operate.

• The plant installed a single scrubber for Units 1 and 2 that began operating on January 1, 2000. The scrubber is approxima tely 60 feet in diameter and 60 feet tall. The scrubber holds approximately 1.3 million gallons of water. The scrubber is a limestone, forced oxidation system and the plant uses DBA as an additive. The scrubber system contains a single tower and is one of the largest

scrubbers in the United States.

• Approximately 1.25 gpm/MW of water eva porates in the scrubber, which exits

out the stack

• The limestone used in the scrubbers is sent to three individual day silos for storage, which feed the three ball mills. The ball mills pulverize the limestone, but it is a rougher pulverization than most plants because of the initial design ofMay 24, 2007 Page 4

the Unit 4 scrubber. The limestone feed ra te to the scrubbers is based on the pH

in the scrubber.

• The DBA for the Unit 3 and 4 scrubber is added to the limestone reagent,

therefore all the limestone that is adde d contains DBA. The DBA for the Unit 1

and 2 scrubber is added to th e reaction tank in the scrubber.

• Both of the scrubbers produce commerci al grade gypsum for use in wallboard manufacturing. National Gypsum built a wallboard manufacturing plant near the power plant. The Big Bend plant pr oduces 650,000 to 900,000 tons of gypsum per year, which is transp orted to National Gypsum.

• The gypsum slurry from the Unit 1 and 2 scrubber is pumped directly to primary hydroclones. The gypsum slurry from the Unit 3 and 4 scrubber is pumped to quencher blowdown tanks and then pump ed to a separate set of primary hydroclones. The underflow from both of the primary hydroclones is approximately 50 to 55% solids and is comb ined and sent to rotary drum vacuum filters. The overflow from both primary hydroclones is approximately 6% solids and is combined in the chloride purge f eed tank. Most of the primary hydroclone

overflow is transferred from the chloride purge feed tank to the return water tank and recycled back to the Unit 1 and 2 scrubber. The remaining primary hydroclone overflow is sent to a secondary hydroclone. The overflow from the secondary hydroclone is between 1 and 2 % solids and flows to the wastewater equalization tank (the beginning of the F GD wastewater treatment system). The underflow from the secondary hydroclone is returned to the Unit 1 and 2 scrubber. The blowdown to the equaliza tion tank represents the purge stream from all four units and it is fairly continuous at a fl ow rate of approximately 230 gpm. The

chlorides concentrati on is about 30,000 mg/L.

• The rotary drum vacuum filters dry the 50% solids underflow from both primary hydroclones into a 90% solids gypsum produc t. The plant washes the gypsum with Sun City Center Sewage effluent. The gypsum produced by the plant is transported to the National Gypsum plan t next door. Any off-spec gypsum is piled on-site and allowed to sit. The ra in rinses the chlorides out of the gypsum and the product is later sold to the National Gypsum plant.

• The make-up water for the FGD system is taken from a series of ponds on site that have a 70 million gallon water storage capacity. The plant pulls additional water (about 3.5 MGD) into the pond system from the Sun City Center Sewage

Treatment Plant effluent disc harge. The plant washes the gypsum cake with fresh Sun City Center Sewage Treatment Plant effluent to remove the chlorides from the gypsum. The plant is capable of using potable water for the FGD make-up, but avoids using it unless absolutely necessary.

• The FGD wastewater treatment system began operation in January 2000, but the plant immediately had issues with settling the calcium sulfate. The clarifiers were

unable to settle the solids. Therefore, the plant redesigned the treatment system. The plant initially had a prim ary clarifier for initial so lids settling and secondary

clarifier after solids conditioni ng. In the redesign, the pl ant built a larg er clarifier that was capable of handling all of the wastewater after the solids conditioning. The original primary and secondary clarifie rs are now used in parallel with theMay 24, 2007 Page 5

new primary clarifier after solids conditio ning. The plant no longer has an initial solids settling clarifier.

Current FGD Wastewater Treatment System:

• The equalization tank recieves wastewaterfrom the secondary hydroclones, offspecifiation effluent from the treatment system, and wastewater from the filtrate sump, which includes filter backwash and filter press filtrate.

• From the equalization tank the water is tran sferred to a reaction tank where lime is added to adjust the pH. The water is then transferred to a second reaction tank where ferric chloride is added for coagulat ion. Then the wastewater is sent to a third reaction tank where the water is gently mixed to create a denser floc. From the third reaction tank, a polymer is a dded as the wastewater flows to the clarifiers. The plant is not sure what polymer is used.

• The wastewater treatment plant has three cl arifiers; one primary clarifier that can

treat all of the wastewater and two secondary clarifiers that can each treat 50% of the wastewater. All three clarifiers operat e in parallel. In th e retrofit design, the plant intended to only use the secondary clarifiers as back -ups, but the plant typically operates all th ree of the clarifiers.

• The overflow from all three clarifiers is combined and sent to the filtration system. From the filters, the wastewater is sent to the treated water transfer tank, which is where the plant collects its NP DES monitoring samples, and then is discharged to the Tampa Bay.

• The underflow from the clarifiers is se nt to the sludge storage tank and goes through one of two filter pre sses to dewater the sludge.

FGD Wastewater Treatment Data

• The plant stated that they have had so me issues analyzing the FGD wastewater treatment effluent samples using clean met hods for mercury. The plant stated that they have also had issues analyzing for arsenic, chromium, lead, nickel, and selenium using the 200 series method because of the dilution needed for the

matrix.

• The plant monitors the FGD treatment syst em effluent quarterly for TSS, oil and grease, arsenic, chromium, copper, lea d, mercury, nickel, selenium, gross alpha, combined radium 226 and 228, and pH. Note: All metals are total recoverable and all are low-level, except mercury. The plant provided EPA with the data

collected since 2000.

• The plant does not have data for the in fluent to the FGD treatment system.

Sampling Information

• The sampling points are located outside; therefore, we will need to prepare to any rainfall that may occur.May 24, 2007 Page 6

• The influent to the FGD treatment system could be collected from the equalization tank effluent. There is a va lve and sample tap located on the pipe exiting the tank where the samples could be collected. This point is where the plant will be collecting the influent to treatment samples for their study. The plant monitors the flow from the tank. Figure 1 presents a picture of where the sample could be collected.

• The effluent from the FGD treatment system could be collected from the sample collection tap for the plant’s monitoring location I-130. The FGD effluent sample piping is next to the filter press filtrate piping; however, the filter press filtrate discharge can be shut off. The plant m onitors the flow rate for I-130. Figure 2 presents a picture of where the sample could be collected.

• The intake canal only provides water for th e cooling systems. The intake for the process comes from the recycle pond system. Therefore, the intake water sample would be collected from the recycle pond. The plant has a sample tap from the pump that transports water from the r ecycle ponds back to the plant operations. The plant monitors the flow rate of th e water back to the system. Figure 3 presents a picture of the sample tap for the recycle pond water.

• The plant has an on-site nurse for minor in juries. The nearest hospital is Sun City Center Hospital. The plant would require a ll samplers to complete a 4-hour health and safety training course. The course could be completed the day before sampling, or on-line.

• The plant has a lab in the FGD area that we could use as the staging area.May 24, 2007 Page 7

Figure 1. Sampling Location for FGD Influent to TreatmentMay 24, 2007 Page 8

Figure 2. Sampling Location for Effluent from FGD TreatmentMay 24, 2007 Page 9

Figure 3. Sampling Point for Process Intake WaterTable 1. List of AttendeesNameOrganization (Representing)TelephoneE-mailLaura Crouch Tampa Electric Company (813) 228-4104 lrcrouch@tecoenergy.comTara Crews Tampa Electric Company(813) 228-4740 tncrews@tecoenergy.comJohn Smolenski Tampa Electric Company (813) 228-1456 jusmolenski@tecoenergy.comKaren Zwolak Tampa Electric Company(813) 630-6968 kozwolak@tecoenergy.comDonna Hill Southern Company (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) 633-1698 thomas.finseth@erg.com