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Site Visit Report

Walter Scott, Jr. Energy Center

7215 Navajo Road

Council Bluffs, IA 51501

March 2, 2009

1.0 Background and Objectives

The Environmental Protection Agency (EPA) is in the process of developing 

316(b) cooling water intake structure (CWIS) requirements that reflect the best 

technology available (BTA) for minimizing adverse environmental impact for all 

existing power plants and manufacturing facilities. As part of this process, EPA 

staff is visiting electric generators and manufacturers to better understand the 

CWIS technologies in use at facilities, including the site-specific characteristics of 

each facility and how these affect the selection and performance of CWIS 

technologies. EPA is also visiting facilities to better understand cooling water use 

and specific issues or technologies that can affect 316(b) compliance. Walter 

Scott, Jr. Energy Center (WSEC)1 was selected for a site visit due to its location 

on a large freshwater river.

2.0 Facility Description

WSEC is located approximately four miles south of downtown Council Bluffs, 

Iowa. The facility began operations in 1954. Units 1, 2, and 3 withdraw oncethrough cooling water from the Missouri River, and Unit 4 withdraws closedcycle cooling tower make-up water from four lateral alluvial wells. WSEC is 

regulated by NPDES permit IA0004308 (which expired February 26, 20082) and 

is owned by MidAmerican Energy Company. The facility employs 

approximately 220 people. The facility and surrounding land encompasses

approximately 1,195 acres.

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3.0 Electricity Generation and Transmission

WSEC consists of four coal-fueled generating units with a total generating 

capacity of 1623 MW.

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 The facility’s low sulfur coal comes via rail from the 

Powder River Basin in Wyoming; 128 car trains arrive approximately every 18 

hours and the facility uses about seven million tons of coal per year. The 

 

1 The facility has historically been referred to as the Council Bluffs Energy Center.

2 All NPDES permits for MidAmerican facilities are currently expired; renewal applications were timely 

submitted but await approval by the permitting authority. Neal South was the first MidAmerican facility to 

receive a renewed permit effective March 31, 2009.

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Facility representatives noted that approximately 304 acres of the site is in use surface impoundments. 

Additionally, adjacent farmland was purchased to provide a buffer from surrounding lands.

4 Unit 1 has a capacity of 45 MW and began operations in 1954; Unit 2 is 88 MW and began in 1958; Unit 

3 is 690 MW and began in 1979; Unit 4 is 800 MW and began in 2007.
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facility’s capacity utilization rate (CUR) is approximately 80%; all four 

generating units operate as baseload units.

The transmission system is owned by MidAmerican Energy Company but is 

operated by a different business unit.

4.0 Cooling Water System and Intake Structure

WSEC has two CWISs that withdraw cooling water from the shoreline of the 

Missouri River. Units 1 and 2 share one CWIS; it has four traveling screens and 

four circulating water pumps. Unit 3’s CWIS has four screens and four 

circulating water pumps. The design intake flow (DIF) for the facility is 662

million gallons per day (mgd) and the average actual intake flow (AIF) for 2009

was 470 mgd. Units 1-3 utilize once-through cooling and Unit 4 uses a closedcycle cooling system (see Section 6.0 below).5

Units 1-3 employ coarse mesh traveling screens.6 Units 1 and 2 have standard 

debris return troughs that return fish and debris to the river; Unit 3 has a separate 

fish spray wash and trough that combines with the debris return before being 

discharged to the river. The screens automatically rotate every 15-20 minutes and 

are cleaned with a high pressure spray wash; during high debris loading periods, 

the screens often operate continuously. The design through-screen velocity 

ranges from 1.7 to 1.9 feet per second (fps) at Units 1-2 and approximately three 

fps at Unit 3.

Scheduled four to six week major maintenance outages are taken on each unit as 

needed (typically once every 4 years). For Units 1-3, one traveling screen and 

circulating pump are refurbished each year. Maintenance can be scheduled during 

the winter, when all of the screens and pumps are not required for normal 

operations. 

5.0 Impingement and Entrainment Information

WSEC is currently working to finalize a 2007 impingement study; this study will 

also include an evaluation of intake technologies and compliance approaches.

6.0 Cooling Tower Feasibility

Facility representatives stated that close-cycle cooling was not reasonably feasible 

for WSEC Units 1-3. They noted a number of potential problems: space 

 

5 Makeup water for the towers is drawn from groundwater wells.

6 Travelling screens for Units 1, 2, and 3 are 3/8-inch mesh.
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constraints, a loss of generating efficiency, high costs,7and icing on the 

transmission lines.8

The cooling tower for Unit 4 (a 22-cell mechanical draft tower with two back-toback rows of 11 cells) was not designed with plume abatement9

and typically

cycles water 6-8 times before blowdown.10 The towers use a standard mix of 

biocides—12.5% sodium hypochlorite and bisulfate at the basin discharge. The 

system loses approximately two percent of the circulating flow to evaporation.

7.0 Debris Handling

WSEC has historically had issues with debris in the spring, when leaves, sticks, 

and eroded low-grade coal (found in the surrounding soil) are swept up in the 

rising waters. Because a major outage occurred on Unit 3 as a result of debris, the 

facility installed a 5mm Tapproge debris filter on Unit 3. 

According to facility representatives, ice is not a significant problem at WSEC. 

The facility is capable of recirculating warm water to the CWIS to address the 

issue. However, at the time of the site visit, Unit 1 had been taken offline due to 

ice blocking the intake and causing condenser vacuum problems.

The condenser also experiences some scaling and calcium deposits, but this issue 

is manageable; a firm is hired once per year to remove these deposits.

8.0 Repowering/Future Uses

WSEC’s Unit 4 began operations in 2007. There are no plans for additional units 

at the facility at this time.

The facility also provides steam to a neighboring ethanol manufacturing plant that 

recently began operations. WSEC provides approximately 475,000 pounds of 

steam per hour from Unit 3, which represents approximately 10% of the main 

steam flow.

9.0 Cooling Ponds

There are no cooling ponds on site.

 

7 A consultant’s report estimated costs for closed-cycle cooling at $55 million, plus $2-3 million per year in 

operations and maintenance (O&M).

8 The cooling tower for Unit 4 has exhibited problems with icing. At the time of the site visit, icing was 

clearly visible in the area above the basin and on the structural elements of the tower.

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Facility representatives noted that the plume can block visibility within the plant boundaries. 

Additionally, depending on wind conditions, the tower plume can be drawn back into the towers, reducing 

the overall efficiency.

10 Water hardness (calcium and magnesium) is generally the limiting factor.
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10.0 Ownership

The WSEC facility is operated by MidAmerican Energy, an investor-owned 

utility. Units 1 and 2 are 100% owned by MidAmerican Energy Company, 

whereas Units 3 and 4 are jointly-owned units.

11.0 316(a)

Facility representatives stated that, under the current NPDES permit, WSEC is not 

subject to any 316(a) limitations. They expect to complete a thermal plume 

mixing zone study later this year.

12.0 Ash Handling

Fly ash from Units 1-3 is typically sold for beneficial uses, but is occasionally

stored in a lined monofill when market conditions are unfavorable. Bottom ash 

from Units 1-3 is wet sluiced to two onsite impoundments; facility representatives 

noted that they are researching potential markets for the sale of the bottom ash.

Fly ash and bottom ash from Unit 4 is stored in an onsite lined monofill.

The Army Corps of Engineers conducts inspections of the levees surrounding the

surface impoundments and performs any necessary maintenance.

13.0 Air Emissions Controls

WSEC uses low NOx burners on all of its generating units, and overfire air is 

installed on Units 2-4. Dry scrubber and baghouse systems are installed on Units 

3 and 4; and a selective catalytic reduction system and activated carbon injection 

system is installed on Unit 4. Materials provided by the facility also note that 

Unit 4 uses a supercritical boiler, increasing efficiency and reducing carbon 

dioxide emissions by approximately 15%. There are no firm plans for any 

additional air emission control equipment at this time.

Attachments

Attachment A List of Attendees

Attachment B Aerial Photo

Attachment C Walter Scott Energy Center Fact Sheet

Attachment D Walter Scott Energy Center CWIS Information

Attachment E Engineering and Flow Diagrams

Attachment F Site Photos

Attachment G Proposal for Information Collection
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Attachment A--List of Attendees

Paul Shriner, EPA Headquarters

Jan Matuszko, EPA Headquarters

Jamie Hurley, EPA Headquarters

John Dunn, EPA Region VII

Glenn Curtis, EPA Region VII

John Bender, Nebraska Department of Environmental Quality

Kelly Meadows, Tetra Tech

Matt Finnegan, MidAmerican

John Lusan, MidAmerican

Spencer Moore, MidAmerican

David O’Dell, MidAmerican

Mark Podany, MidAmerican

Jeff Walters, MidAmerican
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Attachment B–Aerial Photo

Please see DCN 10-6518A accompanying this document

Attachment C--Walter Scott Energy Center Fact Sheet

Please see DCN 10-6518B accompanying this document

Attachment D--Walter Scott Energy Center CWIS Information

Please see DCN 10-6518C accompanying this document

Attachment E--Engineering and Flow Diagrams

Please see DCN 10-6518D accompanying this document

Attachment F--Site Photos

Please see DCN 10-6518E accompanying this document

Attachment G--Proposal for Information Collection

Please see DCN 10-6518F accompanying this document