Notes from Site Visit at Duke Energy’s Gibson Generating Station on February 24, 2009

EPA conducted a site visit at Duke Energy’s Gibson Generating Station (Gibson) located in 

Gibson County, IN on Tuesday, February 24, 2009 to learn about the operations at the plant, 

specifically the deepwell injection of FGD wastewater and planned conversions to dry fly ash 

handling. Table 2, located at the end of these notes, identifies the site visit participants. The 

presentation that the Gibson personnel gave during the site visit is provided as Attachment 1 to 

these notes. 

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

call, which was held on February 13, 2009.

Plant Overview

• Gibson operates five coal-fired generating units at the plant. The table below 

contains some general information on the current operation of each steam electric 

generating unit. 

Table 1. Gibson Generating Station Unit Operations

Unit

Installation 

Date

Gross Capacity 

(MW) Particulate Control NOx Control SO2 Control

1 5/3/1976 670 ESP (cold-side) Selective catalytic 

reduction (SCR)

Wet flue gas 

desulfurization 

(FGD)

2 4/16/1975 670 ESP (cold-side) SCR Wet FGD

3 3/28/1978 670 ESP (cold-side) SCR Wet FGD

4 3/27/1979 670 ESP (cold-side) SCR Wet FGD

5 10/1/1982 670 ESP (cold-side) SCR Wet FGD

• Gibson burns about 29,000 tons of coal per day. The majority of their coal is 

Illinois Basin coal, with sulfur concentrations ranging from 1.5 to 5 lbs 

SO2/MMBTU, but more typically 4.5 to 5.0 SO2/MMBTU. The chlorine content 

of the coal ranges from 0.2 to 0.25% by weight.

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• Gibson is a zero discharge plant and, therefore, does not have a NPDES permit. 

The Gibson plant transfers certain process water to its unlined manmade cooling 

pond, which covers 3,000 acres and is generally 10 to 12 feet deep. The cooling 

pond also provides the service water for the plant. As needed, the plant pulls 

water from the Wabash River into the cooling pond, but the cooling pond does not 

discharge to the Wabash River. [CBI has been removed from this section.]
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FGD Systems

• Gibson stated that they use service water (i.e., cooling pond water) for limestone 

slurry make up, mist eliminator wash water, gypsum washing (Units 1, 2, and 3 

only), and make-up water to the FGD.

• Gibson stated that they can use a blend of service water and reclaim water for 

gypsum washing, limestone slurry make-up, and make-up to the FGD, but they 

try to use as much service water as possible for the mist eliminator wash. [CBI 

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Units 1, 2, and 3 FGD Systems

• The Units 1, 2, and 3 FGD systems are all single tower, limestone forced 

oxidation scrubbers. The FGDs were installed at the following times:

• Unit 1 – Fall 2007;

• Unit 2 – Spring 2007; and

• Unit 3 – Winter 2006.

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Unit 4 FGD System

• The Unit 4 FGD system is a dual tower, limestone inhibited oxidation FGD 

scrubber. Gibson adds emulsified sulfur to the scrubber to prevent the oxidation 

of calcium sulfite to gypsum.

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Unit 5 FGD System

• The Unit 5 FGD system is a horizontal flow, limestone forced oxidation FGD 

system. Gibson stated that the FGD was originally designed for inhibited 

oxidation, but it was recently converted to increase sulfur dioxide removals. The 

Unit 5 FGD was converted to forced oxidation in June 2008. [CBI has been 

removed from this section.]

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• Gibson stated that fixating gypsum is the same as fixating calcium sulfite.

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FGD Solids Disposal

• Gibson stated that Units 1, 2, and 3 have a shared gypsum stacker, but Units 4 and 

5 each have their own FGD solids stacker. Gibson collects the solids from the 

stacker pads and trucks it to the on-site landfill. The gypsum solids from Units 1, 

2, and 3 and the pozzolanic materials from Units 4 and 5 are commingled within 

the landfill.

FGD Wastewater Treatment and Disposal

FGD Wastewater Treatment

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FGD Wastewater Disposal

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• Gibson currently has three nonhazardous injection wells on site. The wells are 

approximately 12,000 feet deep and cased to 5,200 feet. The ground level 

footprint is 150’ x 150’. The surface casing goes to 500 feet.

• Well 1 currently has a test injection permit. Gibson began injecting some amount 

of wastewater down Well 1 in June/July 2007, [CBI has been removed from this 

section.]

• Gibson stated that Wells 2 and 3 are almost complete.

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• Gibson stated that their contractors have been monitoring TSS, pH, chlorides, 

calcium, magnesium, and sulfate to determine whether the wastewater is safe to 

be deep well injected.

Ash Handling

• Gibson is converting Units 1-3 to dry fly ash handling. They currently expect 

conversion to begin in Fall 2011 and to be complete by Spring 2012. 

Construction on all units is expected to be simultaneous with scheduled outages. 

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• Gibson does not expect much change in equipment for the conversion. Currently 

the vacuum pulls ash out of the hoppers, mixes with water, and transfers to the 

pond. For dry handling, they will still use the trunk line, but will add piping from 

the trunk to the filter separation tank. The ash in the separator tank from Unit 3 

will be blown to Units 1 and 2 transfer bins. Ash from Units 1 and 2 will drop 

directly into the transfer bins.

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Ash Ponds

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• Gibson’s ash pond previously used in the 1980s was closed in 2005.
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• Following conversion to dry fly ash handling, Gibson plans to transfer bottom ash 

sluice water only to the North Ash Pond.

On-Site Landfills

• Gibson operates two on-site landfills: South Landfill and the Fixated Scrubber 

Sludge (FSS) Landfill.

• Gibson’s South Landfill includes 377 permitted acres. Thirteen acres are 

currently open. The landfill leachate collects in a separate pond which discharges 

directly to the cooling pond.

• The FSS Landfill, named in 1982, accepts all solids generated at the plant. Fixated 

materials generated from Units 4 and 5 are stored alongside ash and other solids. 

Gibson does not segregate the wastes in the landfill. Leachate from this landfill 

flows into North Basin, and ultimately to the cooling pond.
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Table 2. Site Visit Attendees

Name Organization (Representing) Telephone E-mail

Becky Sparks Gibson Station – Environmental 

Coordinator 812-386-4202 rebecca.sparks@duke-energy.com

Mick Harpenau Gibson – Engineering 812-386-4886 mick.harpenau@duke-energy.com

Tom McClellan Gibson – Engineering - Retired Retired Retired

Debbie Nispel Duke Energy 317-838-1957 debbie.nispel@duke-energy.com

Robert Wylie Duke Energy 704-382-4669 rrwylie@duke-energy.com

Mike Judd Duke Energy 317-838-1729 mike.judd@duke-energy.com

Howard Lewis Duke Energy - Retired Retired Retired

Jim Meiers Duke Energy 317-838-1955 jim.meiers@duke-energy.com

Rick Cleveland Duke Energy 812-386-4146 rick.cleveland@duke-energy.com

Donna Hill UWAG 205-257-5234 dbhill@southernco.com

Keith Condra Indiana DEM 812-380-2311 kcondra@idem.in.gov

Ron Jordan EPA/Office of Water 202-566-1003 jordan.ronald@epa.gov

Deb Bartram ERG (Contractor to EPA) 703-633-1669 deborah.bartram@erg.com