Notes from Site Visit at Seminole Electric Cooperative on January 23, 2013

EPA conducted a site visit at Seminole Electric Cooperative, Incorporation’s Seminole

Generating Station located in Palatka, FL on Wednesday, January 23, 2013 to learn about the 

operations at the plant, specifically the dry conveyor bottom ash handling retrofit. These notes 

describe the information collected during the site visit. Table 2, located at the end of these notes, 

identifies the site visit participants. A summary of the bottom ash handling conversion and block 

diagram of the bottom ash system, provided by Seminole during the site visit, are included as 

Attachment 1 to these notes. Additionally, a water flow diagram provided by Seminole during 

the site visit is included as Attachment 2 to these notes. 

Plant Overview

• Seminole operates two coal-fired generating units at the power plant. Construction of the 

Seminole plant initiated in October 1979, for approximately $960 million. Units 1 and 2, 

which begin operation in January and December 1984, respectively, each have a gross 

generating capacity of 715 megawatts (MW). Both units are categorized as base load 

units. Table 1 contains some general information for the two generating units.

Table 1. Seminole Generating Station Units Operation

Unit Fuel

Capacity 

(MW) Fly Ash

Bottom 

Ash FGD

NOx 

Control FGMC

1

Coal: Bituminous

Oil: No. 2 Fuel Oil 715

Dry Ash

Handling –

Pressure System

Dry Ash 

Handling

Wet 

System

SCR, Overfire 

Air, Low NOx 

burner None

2

Coal: Bituminous

Oil: No. 2 Fuel Oil 715

Dry Ash

Handling –

Pressure System

Dry Ash 

Handling

Wet 

System

SCR, Overfire 

Air, Low NOx 

burner None

• The Seminole plant covers approximately 1,980 acres. After the plant started producing a 

gypsum product, Seminole sold a portion of the land to Lafarge, a wallboard 

manufacturing company that purchases 100 percent of the gypsum product. [QUESTION 

FOR SEMINOLE: Confirm the year and approximate acreage of the land sold to 

Lafarge.] Seminole employs approximately 250 employees on site. 

• The plant draws raw intake water from the St. Johns River. Seminole also discharges its 

treated wastewater to the St. Johns River via NPDES-permitted Outfall D-001. A flow 

diagram for Seminole is provided in Attachment 2 of this memorandum.

• Seminole primarily burns bituminous coal from the Southern Illinois Basin and has up to 

72 additional different sources of coal, primarily including Illinois and Kentucky mines. 

[QUESTION FOR SEMINOLE: Please provide the chloride content of the coal?]
Seminole burns No. 2 fuel oil in Units 1 and 2 for startup and supplemental co-firing for 

flame stabilization. 

• Seminole is currently considering switching to a natural gas fuel source for the plant, due 

to its cost effectiveness. [QUESTION FOR SEMINOLE: If you converted, would you 

modify the existing boilers or install new units for the change to natural gas? If installing 

new units, would you install combined cycle units?]

• Seminole has the following NOx controls installed for both units: SCR, overfire air, and 

low NOx burners. The SCR catalyst is not replaced or regenerated onsite. Seminole

operates its NOx controls year round.

• The plant operates two cooling towers which each process 5,000 gallons of water per 

minute (GPM).

• Seminole performs chemical cleaning of the boilers every five years. [QUESTION FOR 

SEMINOLE: Is this boiler cleaning the fireside of the boiler or the inside of the boiler 

tubes?] The resulting metal cleaning waste is transported by truck and disposed offsite. 

Boiler blowdown and air preheater wash are sent to two percolation ponds (north and 

south) located at the plant. After the water discharges to groundwater, the plant dredges 

the solids and disposes of them in the onsite landfill. [QUESTION FOR SEMINOLE: Is 

Seminole required to do any groundwater monitoring around the percolation ponds?]

• Seminole operates electrostatic precipitators (ESPs) to control fly ash and particulate 

emissions from the plant. The ESPs remove approximately 99.7 percent of the fly ash 

from the flue gas. Seminole generates approximately 250,000 tons of fly ash per year. 

• Seminole currently has no plans to install flue gas mercury control (FGMC) technologies 

at the plant. Seminole is already meeting current air requirements.

Ash Handling Operations

Fly Ash Handling

• Seminole operates dry pressure fly ash handling systems on both units. The dry fly ash

handling systems were installed on Units 1 and 2 as part of the original plant design (i.e., 

the systems were not retrofits). 

• Each unit has 16 fly ash hoppers. Fly ash is collected from the ESP into the 16 hoppers 

and pneumatically conveyed from Units 1 and 2 to two dry fly ash handling storage silos. 

The two silos are equipped to accept dry fly ash from either Unit 1 or Unit 2. The two fly 
ash silos have the capabilities to moisture condition the fly ash or unload the ash

completely dry. 

• The transferred fly ash in the two storage silos is used to stabilize the other materials

transferred to the onsite landfill, which is primarily sludge from the FGD wastewater 

treatment system. The fly ash is mixed with the wastewater treatment sludge, using a 

pugmill unloader, and piled onto a pad near the landfill. The fly ash is fed to the pugmill 

using a screw conveyor. Trucks transport the fly ash and sludge mixture from the pad to 

the landfill.

• Prior to 2000, before sellable gypsum was produced onsite, Seminole was able to sell 100 

percent of the fly ash. However, with the production of sellable gypsum, Seminole must 

use all of the fly ash to stabilize the FGD sludge prior to disposal. Seminole’s fly ash has 

a low enough loss on ignition (LOI) to be marketed.

• Because the plant uses oil for startup fuel, the LOI of the fly ash is higher during startup. 

Bottom Ash

• In 2012, Seminole completed conversion of the bottom ash wet sluicing systems on each 

unit to completely dry bottom ash conveyor systems. Seminole installed Clyde 

Bergemann Power Group’s (CBPG) DRYCONTM systems on Units 1 and 2 at the plant.

The retrofit of the Unit 2 bottom ash handling system was completed in April 2012, and 

Unit 1 was completed in November 2012. Seminole installed the first DRYCONTM 

systems (or similar type of dry conveying system) in the United States since the 1980’s. 

An older version of the dry conveyance system, designed by Magaldi, was installed in the 

United States at the Crystal River Plant. The combined total cost to convert both units at 

Seminole was approximately $25 million, including engineering, equipment, installation, 

removal, and other activities. 

• The bottom ash handling conversion took four years from conception through 

completion. Seminole considered a conversion from the wet sluicing system based on an 

economic analysis completed in 2007. Seminole chose to retrofit their wet bottom ash 

sluicing system because it was labor intensive, energy intensive, and vendors were 

starting to phase out required replacement parts. 

• Prior to the conversion, Seminole was wet sluicing bottom ash and economizer ash to 

four dewatering bins for solids removal. The overflow water from the dewatering bins 

was recycled back to the bottom ash handling system or sent to a wastewater treatment 

system, including pH adjustment and settling, prior to discharge to St. Johns River. The 

wet bottom ash handling system used 26 pumps per unit and generated 300 GPM of 
bottom ash sluice. The wet system required an operator to maintain the bottom ash wet 

sluicing system (i.e., fixing valves and leaks) at all times. Additionally, sluice water was 

previously pumped approximately 150 feet to the economizer ash hoppers to collect 

economizer ash prior to being combined with the bottom ash sluice sent to dewatering 

bins, all resulting in high operation and maintenance costs.

• Seminole did not have any problems meeting Florida water quality limitations or 

discharge permit limitations for the bottom ash sluice; therefore, the plant did not convert 

the systems due to water quality issues. The plant ultimately decided to convert to the dry 

handling system because of the benefits resulting from an economic analysis completed 

in 2007, which included less maintenance and labor, safety benefits, and energy savings. 

• Seminole looked at all available bottom ash handling systems for the planned conversion. 

These systems included complete recycle, mechanical drag systems, dry conveying 

systems, and pneumatic systems. Based on the economic analysis, Seminole determined 

that the DRYCONTM installation would result in a lower horsepower requirement for 

bottom ash handling equipment, a reduced parasitic load (40 MW per unit), reduced labor 

and maintenance costs, reduced operator exposure to the system, and thermal efficiency 

benefits. Seminole did not pursue the mechanical drag system due to concerns with drag 

chain breakage and replacement. [QUESTION FOR SEMINOLE: Please provide an 

estimate of the reduced thermal energy losses realized after installing the DRYCONTM 

system.]

• The new DRYCONTM system does not use any water, requires less power, parts, and 

system-operator interaction. 

• In the DRYCONTM system, the bottom ash from each unit drops into one of three bottom 

ash hoppers. Each hopper has three pressure gates equipped with jaw crushers, which are 

manually operated to break apart large agglomerations of bottom ash slag to ensure that 

they are the right size to be cooled and conveyed. The crushers break the bottom ash up 

to roughly 8 inch pieces. Because of the new hopper design and internal temperature, 

Seminole worked with the contractors to install cameras within the hoppers so operators 

can observe the operation of the crushers, and any potential issues with boiler slag, prior 

to sending bottom ash through the rest of the conveyance system. Additionally, the 

contractors worked with Seminole to install poke holes along the hopper walls to break 

up or redirect any large pieces of bottom ash potentially causing issues prior to sending to 

the primary conveyor.

• The three crushers at the bottom of each hopper have gates; therefore, Seminole can 

isolate the bottom ash if there are any issues downstream with a conveyor or any part of 
the bottom ash handling system. At full load, the hoppers (with a 4,600 cubic feet 

capacity) can hold up to four days worth of bottom ash.

• From the crushers, the 8 inch bottom ash pieces fall onto the primary conveyor 

underneath the boiler. The primary conveyor is fully sealed to the combustion chamber. 

Negative pressure inside the bottom of the boiler pulls air into the system to cool the 

bottom ash. The idea is that the incoming air will re-burn the bottom ash and reduce the 

unburned carbon level, increasing thermal efficiency. 

• The primary conveyor runs horizontally underneath the boiler prior to inclining up to the 

primary crusher. The conveyor belt is a chain of linked conveyor pans. The conveyor 

pans can be removed and replaced separately as necessary, rather than replacing the 

entire chain.

• A similar conveyor belt is in place approximately 150 feet above the bottom of the boiler 

underneath the six economizer hoppers (for each unit). The economizer collecting 

conveyor dumps the economizer ash into a double dump isolation valve and onto another 

conveyor. From the second economizer ash conveyor, the economizer ash is dumped on 

to the primary conveyor (carrying the bottom ash) prior to the conveyor incline to the 

primary crusher.

• Bottom ash and economizer ash are conveyed up an incline and dumped into the primary 

crusher. The primary crusher is actually two crushers with a diverter valve by the mouth 

of the primary conveyor. Seminole built in this redundancy in the event that one crusher 

requires maintenance. The primary crusher reduces the size of the bottom ash and 

economizer ash pieces to approximately 3 inches. An air inlet is also located at the top of 

the primary conveyor to pull in extra air to the system for cooling the bottom ash. See 

Attachment 1 for a diagram of the bottom ash handling system.

• From the primary crusher, 3 inch pieces of bottom ash and economizer ash fall onto a 

secondary conveyor. The secondary conveyor inclines to the secondary crusher (built 

with the same redundancy as the primary crusher). The secondary crusher reduces the 

size of the bottom ash and economizer ash to approximately 3/4 inch pieces. The bottom 

ash and economizer ash are then deposited into the bottom ash silo. 

• The primary and secondary conveyors carry the bottom ash approximately 150 feet from 

the units to the bottom ash silo. Each unit has an identical conveyor and silo system. The 

inclines are built into the conveyors to deposit the ash into the silo and to provide enough 

time for the bottom ash to cool during the trip from the bottom of the boiler to the silo. 
• The storage capacity of each bottom ash silo is 20,000 cubic feet, which can store 

approximately 7 to 9 days of bottom ash and economizer ash. Blowers are installed at the 

bottom of each silo to ensure that the bottom ash isn’t settling at the bottom of the silos. 

Ash is unloaded from the silos approximately twice a week. The bottom ash can be 

unloaded completely dry or moisture conditioned. [QUESTION FOR SEMINOLE: 

Please provide the moisture content of dry bottom ash.]

• Bottom ash unloaded into an open top dump truck is moisture conditioned and unloaded 

with a pugmill, using intake water, for dust control. Seminole does not measure the 

moisture content of the bottom ash unloaded from the pugmill, but rather, wets the 

bottom ash based on the look and feel of the moisture conditioned bottom ash from the 

pugmill. [QUESTION FOR SEMINOLE: Please provide an estimate of the moisture 

content of the moisture conditioned bottom ash.] Bottom ash unloaded into closed, 

vacuum trucks is unloaded completely dry using a telescopic chute with a bin vent 

pulling vacuum off the truck to eliminate fugitive dust. Currently, all bottom ash is 

unloaded using the pugmill unloader. The moisture conditioned bottom ash is sold to a 

concrete manufacturing company. The dry telescopic unloader was installed for future 

contracts. 

• The pugmill unloader and telescopic chute can unload bottom ash at a rate of 275 tons per 

hour.

• The bottom ash from the wet sluicing system had an LOI of 8 to 9. With the new system, 

particularly from the re-burning of the bottom ash, the LOI is approximately 1 to 2.

• Seminole hired an outside engineering firm to help prepare the request for proposal for 

the bottom ash conversion. Additionally, this outside engineering firm was responsible 

for overseeing the onsite contractors and construction of the system. 

• The goal of the dry bottom ash system design was to build the systems with enough 

capacity in the design (e.g., overdesign the system) to account for emergency situations. 

Seminole worked with the contractor to incorporate enough capacity into the speed of the 

conveyors to handle different bottom ash loads from the hopper. The DRYCONTM 

system is designed to handle 10 tons per hour (tph) (the actual bottom ash production rate 

is 8 tph); however, the conveyor can actually handle up to 40 tph of bottom ash, not 

because of the size of the equipment, but because of the speed of the conveyors. Having 

the variable conveyor speed allows the plant to handle different amounts of bottom ash, 

which is helpful during start ups and shutdowns because it moves the bottom ash out 

quickly. Additionally, if the DRYCONTM system had a maintenance issue, the plant 

would hold the bottom ash in the hoppers (up to four days storage time when the unit 
runs at full capacity) and then quickly be able to move the bottom ash running the 

conveyor at a higher speed. Incorporating this design “redundancy” did not increase the 

cost of the retrofit significantly, because the system’s ability to handle additional ash is 

not in the size of the conveyor belt, rather the speed of the conveyor.

• Similarly, the plant designed the economizer ash conveyors for the same redundancy. The 

units produce approximately 1-2 tons of economizer ash per hour and the conveyor can 

handle up to 7 tons of economizer ash per hour. 

• The conveyors run constantly at approximately 25 percent of the maximum design speed 

for the system. 

• As part of the request for proposal, Seminole included the specific number of outage days 

that would be allotted for the conversion (30 days). The retrofit for each unit was 

successfully completed within the 30 day planned outage, with all necessary preparation 

done leading up to the outage. For both units the contractor actually completed the 

conversion within 21 days. After the conversion was complete, the contractors tested the 

system for three to four days prior to start up. Seminole did not have any notable start up 

issues, excluding warranty issues with the contractors and learning curves with pressure 

ratings and temperature settings. Seminole had more issues with the installation of the 

first system (on Unit 2) compared to the second installation (on Unit 1).

• Seminole has not had any forced outages because of the DRYCONTM system since its 

installation in 2012.

• The installation of the DRYCONTM system was facilitated by vertical space already 

available underneath the boiler. The contractors did not have to excavate any space for 

the removal of the wet sluicing system or installation of the DRYCONTM system. The 

removal of the wet bottom ash hopper created more maintenance space around the 

boilers. Additionally, the area around the boiler is cleaner and safer, as it was previously 

covered with water. 

• Seminole removed all equipment from the wet sluicing system, including the four 

dewatering bins and overflow tank, from the site. The majority of the metal was given to 

the contractor to sell as scrap metal. Seminole saved motors and valves that could be 

reused throughout the plant. The only pieces of equipment that Seminole kept are the 

unloaders underneath the silo where the dewatering bins would dispense the dewatered 

bottom ash into dump trucks. 
• Seminole has 5 operators per shift at the power plant. These operators are responsible for 

all the operations at the plant, including the bottom ash handling system. The new 

system requires significantly less operator interface and is considered to be safer than the 

old system. At this point, Seminole can quantify the savings on electrical power, 

maintenance, and operation; however, an analysis on improved boiler efficiency has not 

been completed. [QUESTION FOR SEMINOLE: Please provide data on the specific cost 

savings experienced from converting from the wet sluicing system.]

• The main concern for wear and tear on the system is the affect of the hot bottom ash on 

the system. The temperature in the bottom of the boiler is 300 oC. Because the conveyors 

move so slowly, the fatigue on the equipment is not significant and is not really a 

concern. 

• Seminole estimates that conveyor plates and other pieces of equipment on the system 

would need to be replaced every 30 years; however, the entire system would not need to 

be replaced.

FGD System

• Seminole operates two wet FGD systems, which service Units 1 and 2. Both systems are 

limestone forced oxidation systems that achieve 92% sulfur dioxide efficiency. Seminole 

uses 1,000 tons of limestone per day in their FGD systems. 

• Seminole does not monitor solids concentrations within the scrubber. However, Seminole 

operates the scrubber at chloride levels between 8,000-12,000 ppm. When the FGD 

systems were originally installed, the plant did not have a purge stream and had chlorides 

concentrations ranging from 40,000 to 80,000 ppm. The high chlorides level was 

corroding the equipment so the plant installed the purge water treatment system to allow 

the plant to discharge the FGD wastewater from the system. 

• The design maximum chlorides level is 20,000 ppm. Seminole sends blowdown to the 

wastewater treatment system constantly at a rate of 850 GPM. [QUESTION FOR 

SEMINOLE: Please confirm that the plan blows down continuously at a rate of 850 

GPM?]

• Seminole adds dibasic acid to the scrubbers to improve the sulfur dioxide removal 

efficiency.

• Seminole uses the following sources of water as makeup to the FGD system as FGD 

reagent preparation, absorber makeup, or mist eliminator wash water: 
o Recycled scrubber purge;

o Gypsum washwater;

o Landfill leachate;

o Uncapped landfill runoff water;

o Condensate polisher regeneration wastewater;

o Filter backwash water; and

o Service water from St. Johns River.

• FGD slurry blowdown is transferred from each scrubber to the scrubber thickeners (one 

for each unit) at a rate of 850 GPM. Polymer is added to the thickeners to lubricate the 

gypsum to facilitate settling. 

• The overflow from the thickeners (i.e., FGD scrubber purge) is sent to the supernatant 

tank (overflow tank). Some of the water from the supernatant tank is transferred back to 

the scrubber and some is transferred to the Purgewater Treatment System. Additionally, 

Seminole has the option to send some of the water to the onsite pond system, depending 

on system operations. [QUESTION FOR SEMINOLE: Please provide the total flow from 

the supernatant tank to the treatment system, recycled back to the scrubber, and to the 

pond system.]

• The underflow from the thickeners is directed to a surge tank once the unprocessed 

gypsum is thickened to 55 percent solids. From the surge tank, the underflow it is sent to 

the vacuum belt filters, which were installed in 2008, for dewatering. Seminole installed 

the vacuum belt filters to replace rotary drum filters; however, the rotary drum filters can 

still be used in backup situations. Additionally, the plant installed hydrocyclones in 2012 

as backups for the thickeners. The plant only uses the hydrocyclones if the thickeners are 

down for maintenance. 

• The plant washes the gypsum with service water from St. Johns River as it is applied to 

the vacuum belt filter. The filtrate from the vacuum belt filters and the wash water are 

transferred back to the thickeners or to the onsite pond system. 

• Seminole sells 100 percent of the produced gypsum to Lafarge. Since 2005, Seminole 

estimates that approximately 500,000 to 600,000 tons of gypsum is produced every year.

FGD Wastewater Treatment

• The FGD wastewater treatment system (i.e., Purgewater Treatment System) treats the 

FGD scrubber purge from the supernatant tank. The Purgewater Treatment System was 

originally designed for remove the selenium present in the FGD wastewater. The FGD 

scrubber purge is sent to one of two batch reactors that operate in parallel. Each batch 
reactor holds 24,000 gallons of wastewater. As one batch reactor is treated, the other 

batch reactor is filling with process wastewater from the supernatant tank at 300 GPM. 

• As each reactor fills, agitators operate at high speed. Lime slurry is added to the batch 

reactor to raise the pH to 8.5 S.U. The plant also adds ferrous chloride to the reactors 

while the tank is filling. After the reactor is full, the agitators are switched to low speed. 

• Seminole sends samples of the influent to the batch reactors to a laboratory to measure 

selenium concentrations using atomic absorption. Selenium concentrations at the influent 

to the batch reactor can range from between 180 ppb to 400 ppb. The treatment system 

reduces the selenium levels in the wastewater to 20 ppb and less. Historically, Seminole 

has observed 98 percent selenium removal. [QUESTION FOR SEMINOLE: Please 

confirm the 98 percent selenium removal.]

• The effluent from the batch reactors is pumped to the clarifier (an old backup thickener). 

[QUESTION FOR SEMINOLE: Please provide the flow rate from the batch reactors to 

the clarifier.] Polymer is added to the wastewater flow as it is pumped from the batch 

reactors to the clarifier. The retention time in the clarifier is approximately four days. 

• The underflow from the clarifier is sent to the fly ash silos to mix with fly ash prior to 

disposal in the onsite landfill. Alternatively, the plant has two filter presses to dewater the 

sludge prior to disposal in the landfill. [QUESTION FOR SEMINOLE: How often do 

you dewater the FGD sludge with the filter presses? Why do you use the fly ash to 

stabilize the FDG solids instead of selling the fly ash and dewatering the FGD solids in 

the filter presses?]

• The overflow from the clarifier is gravity fed to sand filters. Filter backwash from the 

sand filters is transferred back to scrubber. The treated water is then mixed with treated 

domestic wastewater, coal pile runoff, demineralizer regeneration water, and cooling 

tower blowdown, treated with sulfuric acid to lower the pH to 7 S.U., and then 

discharged directly to St. Johns River via final outfall D-001. Prior to converting the 

bottom ash handling system, Seminole diluted the FGD wastewater discharge with 

bottom ash sluice water. Since the conversion to the dry bottom ash system, Seminole has 

needed to pull in additional process wastewater for dilution. Therefore, the conversion to 

the dry bottom ash system did not reduce the amount of intake water required by the 

plant.

• Seminole is currently operating under a consent order to address multiple permit 

violations for elevated mercury levels coming from the Purgewater Treatment System. 

Seminole’s NPDES permit limitation for mercury is 90 ng/L.
• Seminole has observed mercury concentrations up to 150 ng/L -160 ng/L being 

discharged to St. Johns River. Seminole usually measures mercury discharge 

concentrations at internal outfall I-006 (directly from the Purgewater Treatment System) 

ranging from 400 ng/L to 500 ng/L. These concentrations are diluted ten times when 

mixed with the cooling tower blowdown and other wastewaters prior to final discharge to 

St. Johns River. Seminole has observed some mercury concentrations at outfall I-006 

ranging from 1,000 ng/L to 2,000 ng/L.

• Seminole recently installed a new layer of catalyst in each of the SCR systems. Since this 

installation, Seminole observed large mercury concentration spikes and had two permit 

exceedances in two months. Seminole believes that the SCR catalyst is the cause of the 

high mercury discharges. 

• Currently, Seminole has an interim mass-based permit limit of 2.65 lbs/year for mercury. 

As part of the consent order, Seminole needs to complete studies to get back into 

compliance with the mercury permit limitation. As part of the studies, Seminole is 

evaluating the following: 

o Scrubber operation;

o Additional treatment steps;

o Scrubber ORP effects;

o Iron cycling; and [QUESTION FOR SEMINOLE: Please provide some 

information on iron cycling? What type of negative effects could iron cycling 

have on the gypsum?]

o Adding inorganic or organic sulfides to the treatment system.

• Seminole evaluated the possibility of adding organosulfides to the Purgewater Treatment 

System and determined that additional reaction tanks and a clarifier would be required for 

system operation, costing approximately $5 million. Additionally, Seminole determined 

that adding large amounts of organosulfide to the system decreased the effluent mercury 

concentrations by 50 percent. [QUESTION FOR SEMINOLE: Do you have any 

sampling results for dissolved mercury in the system? Was the 50 percent reduction in 

mercury concentrations based on bench scale testing, pilot scale testing, theoretical 

calculations, or another basis?]

• Seminole expects that the addition of dibasic acid in the scrubber is increasing selenium 

concentrations in the scrubber purge water; however, Seminole does not believe this has 

an effect on mercury concentrations in the scrubber purge water.
• Seminole conducted a study to evaluate the possibility of installing the GE Advanced 

Biological Metals Removal System (ABMet®) to treat selenium and cyanide. According 

to the study, the system did not decrease the cyanide or selenium concentrations in the 

effluent from the system. 

• Seminole also evaluated the possibility of installing a zero liquid discharge (ZLD) 

system, in combination with the proposal of a new coal-fired unit at the plant. Although 

Seminole is not moving forward with the new unit, the evaluation of the ZLD system 

showed high capital, O&M, and landfilling costs for the system. Seminole estimates that 

it would likely cost approximately $100 million just to landfill the solids from the ZLD 

system.

Landfill and Leachate Collection

• Seminole operates one onsite, lined landfill (FGD Landfill). Seminole is planning to 

expand the landfill in 2022. 

• The FGD landfill was brought online in 1984 and now covers approximately 118 acres. 

The landfill receives and stores boiler slag, bottom ash, fly ash, calcium sulfate (gypsum), 

calcium sulfite, pozzolanic material, plant sump solids, cooling tower basin sludge, and 

solids from the domestic wastewater treatment. The expansion of the landfill will provide 

Seminole with 8 to 10 more years of storage space.

• The landfill is lined with a double liner. Additionally, Seminole installed a French drain 

along three sides of the landfill to collect leachate, runoff, and groundwater. All of the 

collected leachate is transferred to the onsite pond system (EPF Pond Treatment System) 

and either transferred to the FGD scrubber system or transferred to the Purgewater 

Treatment System prior to being discharged to St. Johns River.

Ponds

• Seminole has five stormwater ponds, two coal pile runoff ponds, two percolation ponds, 

and six process wastewater ponds. 

• The process wastewater ponds (EPF Pond Treatment System) store FGD scrubber purge, 

gypsum wash water, storm water, filter process water, and leachate. All six of the process 

wastewater ponds are lined. Seminole does not discharge the overflow from the EPF 

Pond Treatment System directly to surface water, instead the overflow is either sent to 

the Purgewater Treatment System and ultimately discharged to St. Johns River or used as 

FGD absorber make-up water.

• The two percolation ponds receive boiler blowdown and air heater wastewater. 
Table 2. Site Visit Attendees

Name Organization (Representing) Telephone E-mail

John Lopez SECI – SGS Palatka 386-328-9255 x2178 jlopez@seminole-electric.com

Robert Yarbrough SECI – Environmental 813-739-1228 ryarbrough@seminole-electric.com

Justin Gostnell SECI – Environmental 813-739-1375 jgostnell@seminole-electric.com

Donna Hill Southern Company 205-257-5234 dbhill@southernco.com

Tom Wess SECI – HQ 813-739-1206 twess@seminole-electric.com

Kevin Misamore SECI – SGS 386-328-9255 x2254 kmisamore@seminole-electric.com

Ron Jordan EPA 202-566-1003 jordan.ronald@epa.gov

Jezebele Alicea EPA 202-566-1755 alicea.jezebele@epa.gov

Daisy Wang ERG 703-633-1692 daisy.wang@erg.com

Elizabeth Sabol ERG 610-344-0829 elizabeth.sabol@erg.com