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Site Visit Report

Nebraska City Station

7264 L Road

Nebraska City, NE 68410

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 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 cooling 

water intake structure (CWIS) technologies in use at facilities, including the sitespecific 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. Nebraska City was selected for a site visit due to its location 

on a large freshwater river.

2.0 Facility Description

Nebraska City began operations in May 1979 on a 1600-acre site1about 8 miles 

southeast of Nebraska City, Nebraska. The facility withdraws cooling water from 

the Missouri River (at river mile 556.2) and is regulated by NPDES permit 

NE0111635, which was renewed on July 1, 2008. Nebraska City is owned by the 

Omaha Public Power District (OPPD) and employs approximately 158 people.

3.0 Electricity Generation and Transmission

Nebraska City is a 650 MW coal-fired2power plant with 1 generating unit. The 

facility’s capacity utilization rate (CUR) is approximately 77%.

The transmission system is owned by OPPD but is operated by a different 

business unit of the company.

4.0 Cooling Water System and Intake Structure

Once-through cooling water is withdrawn through a shoreline CWIS with 6 intake 

bays; each intake bay houses one coarse mesh (3/8”) traveling screen and each 

pair of bays feeds one circulating pump with a capacity of 244.8 million gallons 

per day (mgd or 170,000 gallons per minute [gpm]) each. Typically, two pumps 

 

1 Over 1200 acres are leased as farmland.

2 The facility’s coal comes via rail from the Powder River Basin in Wyoming; 135-car trains arrive every 

20 hours.
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are used during generation; facility representatives noted that they prefer to use 

the northernmost pumps, as these are less prone to debris and sediment fouling.

The traveling screens are typically rotated continuously (at 2.5 feet per minute) to 

best handle debris loading.3 The original screen design included intermittent 

screen rotation, but the sedimentation in the intake bays prompted more frequent 

screen rotation.

In total, the facility has a design intake flow (DIF) of 670 mgd and an average 

actual intake flow (AIF) of 450 mgd. The average design intake velocity of the 

CWIS is 1.36 feet per second (fps).4

5.0 Impingement and Entrainment Information

EPA did not collect any information about biological studies at this site.

6.0 Cooling Tower Feasibility

Nebraska City is adding a second unit (see Section 8.0 below) that will utilize 

closed-cycle cooling.5 The 18-cell mechanical draft tower was built at a cost of 

$40-60 million and will withdraw makeup water from an existing intake pipe.

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The towers include drift eliminators, but no plume or noise abatement 

technologies were installed. The towers are aligned in two back-to-back rows.

Facility representatives have not considered closed-cycle cooling for Unit 1.

7.0 Debris Handling

Nebraska City has historically had greater problems with sedimentation than other 

OPPD facilities (such as North Omaha). The facility is located downstream of the 

confluence with the Platte River, which adds a significant volume of suspended

sediment, as well as debris. Every 6 months, the traveling screens become silted 

in and sediment must be pumped out. A water sparging system is used; a 3” 

screen wash header removes debris from the screen face, a 4” water line sparges

the screen boot whenever the screen is in service, an 8” water line expels sand 

from each screenwell and two 20” lines sparge sediment at the entrance to the 

CWIS as needed. Additionally, fine grain sand erodes screen parts and water 

pumps.

 

3 The screens can be rotated on a fast speed (10 feet per minute) for heavy debris loads.

4 At low water, the through-screen velocity is 1.8 fps; at high water, 1.1 fps.

5 The planning for the design of Unit 2 began before the Phase I and Phase II rules were published; at the 

time, OPPD assumed that the new unit would likely be required to install closed-cycle cooling.

6 Nebraska City has been able to use much of the existing infrastructure in regards to its cooling tower 

installation
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In winter, the facility deploys an ice barge. Facility representatives noted that the 

Army Corps of Engineers regulates the water levels, leading to additional 

difficulties in the winter as water levels are lower, making ice a greater danger to 

the operation of the CWIS.7 The facility is also able to recirculate warm water 

and use a cold water agitator at the water’s surface to address icing. The agitator 

can also be used to expel floating debris.

8.0 Repowering/Future Uses

Construction of Unit 2 is nearly complete. It will also be a 650 MW coal-fired 

unit.

9.0 Cooling Ponds

There are no cooling ponds on site.

10.0 Ownership

OPPD is a public utility that is owned by the state of Nebraska. The entire state is 

supplied by public power.

11.0 316(a)

The permits for all OPPD facilities have thermal discharge limits; facility

representatives noted that the most troublesome time of year for meeting these 

limits was in the summer, when the ambient water temperatures are highest. They

added that they have not had any problems meeting state water quality standards, 

though.

12.0 Ash Handling

Bottom ash is handled wet; some is sold for beneficial uses, but most is stored in 

an onsite landfill.

Fly ash is stored dry and sold for beneficial uses.

13.0 Air Emissions Controls

Nebraska City Station uses a cold-side electrostatic precipitator for control of 

particulate matter, SO3 Injection to reduce opacity, and over-fire air for reduction 

of NOx.

 

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Facility representatives cited a recent alert from the Corps about an ice bridge upstream that could affect 

water levels at Nebraska City by as much as 2 feet.
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14.0 Additional Information

Facility representatives noted that there are no additional design considerations 

for being located in a tornado-prone region.

Facility representatives considered variable speed pumps for the CWIS, but 

cannot justify the capital cost for replacing the equipment.

Facility representatives stated that they are concerned about the use of fine mesh

screens, as the river conditions (especially during spring due to increased runoff 

and in winter due to icing) could jeopardize operations. Specifically, the concern 

is that the differential across the screens would increase significantly due to debris 

plugging, possibly jeopardizing generation activities. See Section 7.0 below.

Attachments

Attachment A List of Attendees

Attachment B Aerial Photos

Attachment C Nebraska City Facility Description

Attachment D Engineering Diagrams

Attachment E Information on Debris 

Attachment F Site Visit Photos
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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

Russ Baker, OPPD

Kirk Miller, OPPD

Ray Lynn, OPPD

Tim Yager, OPPD

Mike Krumland, Nebraska Public Power District (NPPD)

Joe Citta, NPPD

Justin Reimers, NPPD
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Attachment B—Nebraska City Aerial Photo

Please see DCN 10-6520A accompanying this document

Attachment C—Nebraska City Facility Description

Please see DCN 10-6520B accompanying this document

Attachment D—Engineering Diagrams

Please see DCN 10-6520C accompanying this document

Attachment E—Information on Debris

Please see DCN 10-6520D accompanying this document

Attachment F—Site Visit Photos

Please see DCN 10-6520E through G accompanying this document