1 Site Visit Report North Omaha Station 7475 Pershing Drive Omaha, NE 68112 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 th e cooling water intake structure (CWI S) technologies in use at facilities, including the site
specific characteristics of each facility and how these affect the selection and performance of CWI S technologies. EPA is also visiting facilities to better unde rstand cooling water use and specific issues or technologies that can affect 316(b) compliance. North Omaha was selected for a site visit due to its location on a large freshwater river and onsite pilot testing of Beaudrey screen s . 2.0 Facility Description North Omaha began operations in 1954 on a 100
- acre site in northern Omaha, Nebraska. The facility

withdraws cooling water from the Missouri River (at river mile 625.2) and is regulated by NPDES permit NE0000621 , which was renewed October 1, 2008. North O maha is owned b y the Omaha Public Power District (OPPD) and emplo ys approximately 120 people. 1 3.0 Electricity Generation and Transmission North Omaha consists of 5 coal
- fired 2 generating units that ty pically operate as load
- following 3 units. The facilit y’s capacit y utilization rate (CUR) is approximately

75%. North Omaha ty

picall y operates at a heat rate of 10,800 Btu/Kwh and has a total generating capacity of 663 MW
. The facility

schedules a one week routine maintenance outage annually and a three week boiler outage every three y ears . The condensers are cleaned during each outage to ensure efficient operation of the generating unit. Facility representatives noted that, despite the heav y debris loads, the condenser tubes

1 Another 70 OPPD maintenance staff are also based at North Omaha. 2 North Omaha’s coal comes via rail from the Pow der River Basin in Wyoming; 125
- car trains arrive every 2 days. 3 Load following plants typically operate near capacity during the day and early evening when demand for pow er is highest; these facilities then reduce generation at night when demand is lower.2 have never needed to be replaced. A major turbine outage occurs every 8
- 10 ye ars. The transmission sy stem is owned by OPPD but is operated b y a different unit. 4.0 Cooling Water System and Intake Structure North Omaha has three CWI Ss that withdraw once
- through cooling water from the shoreline of the Missouri River. Each CWI S is located in a separate screenhouse with a trash rack with 3 ” spacing
. The screenhouse s for Units 1 and 2 and for Units 3 and 4 each have 5 intake bay s, each with one pump 4 and one coar se mesh (3/8”) traveling screen . The screenhouse for Unit 5 has 6 intake bay s, with three pumps (84.6 mgd or 58,750 gpm each) and two screens per bay
. 5 The screens automatically rotate every 8 hours or when a pre
- determined head differential is reached. The design intake velocit y of the CWI Ss is 1.4 to 2.03 feet per second (fps). 6 In total, the facility has a design intake flow (DIF) of 758 mgd and an average actual intake flow (AIF) of 730 mg d which represents approximately

4% of the average river flow
. Thermal effluent is returned to the river adjacent to the CWISs. In 200 6 , North Omaha tested a new t ype of intake screen on one intake bay on Unit 5: the Beaudrey W ater Intake Protection ( WI P ) s creen. North Omaha replaced one of its standard coarse mesh traveling screens in Intake Structure No. 3 with an 8 foot diameter 6 mm mesh Beaudrey WIP screen . The facility placed the test screen, which was des igned to fit into the existing traveling screen well, at the screenwell bottom and sealed the remaining open area (formerl y occupied by the traveling screen) with steel plates to force all incoming water to pass through the screen
. The main reason North Omaha became interested in the WI P screen was the potential to eliminate debris carry over. (See Section 7.0 below.) Due to the debris and sediment issues, the facility performs a screen overhaul during each maintenance shutdown, including rebuilding the screen, resetting chains and tensioners, and replacing worn parts and seals; the process is expensive and time
consuming. The WIP screen is a wheel
- shaped, round screen which is divided into pie
- shaped chambers by

plates on the inlet side of the screen . A hy draulic pump and drive gear rotate the screen wheel twice per minute, where fish and debris impinged on one section of the wheel are vacuumed off as they rotate under a stationary scoop mounted over one section of the wheel. Fish and debris are vac uumed off via a

4 The pumps for Units 1
- 2 each have a capacity of 43.2 million gallons per day (mgd) (30,000 gallons per minute [gpm]). The pumps for Units 3
- 4 have a n average capacity of 5 3.3 mgd ( 37 ,000 gpm). 5 This CWIS w as built with the expectation that Unit 6 w ould eventually be constructed and has a tot al of 12 intake bays . Unit 6 w ould use the other 6 intake bays. 6 At normal river elevation; at low w ater, the range of through
- screen velocity changes to 3.64 to 5.67 fps.3 specially designed fish
- friendly

backwash pump where the impeller is designed to separate the water into pockets that provide a safe place for the fish to remain as the water is moved through the pump. The backwash flow then discharges thr ough a pipe to a collection tank that overflows back into the river. The through
- screen velocit y as operated was calculated to be 2.5 feet per second. As part of the screen evaluation at North O maha, Beaudrey conducted an impingement survival study of this pilot screen. The study and its results are described full y in a report provided by Beaudrey and EPRI titled “ Beaudrey Water Intake Protection (WI P) Screen Pilot
- S cale Impingement Survival Study
. ” 7 No biocides are used at North Omaha. 5.0 Impingement and Entrainment Information North Omaha has not collected impingement or entrainment information for its existing traveling screens. However, as described above, Beaudrey collected two ye ars of biological monitoring for the pilot WIP screen beginning in 2007
. During the first year, impinged fish were collected four times per month
. 8 At the end of the ye ar, facility

representatives determined that there were not enough fish impinged to provide a statistically significant sample size to examine the impingement survival rates. A second series of tests were developed, where fish common to the Missouri River 9 were introduced directl y in front of the screen and impingement survival rates were compared to a control group. Biologi sts used seine nets to collect fish from the river and other fish were purchased from local hatcheries. The screen testing concluded that the WIP screen has no effect on fish impingement mortality ; in other words, fish passing through the screen return ex hibited the same survival rates as fish that remained in the control test. North Omaha has not conducted an y entrainment or ambient sampling, but indicated that various other organizations have conducted ambient sampling of the Missouri River. 6.0 Cooling Tower Feasibility Facilit y representatives have not considered closed
- cy cle cooling for North Omaha. They

noted a number of problems associated with retrofitting a closed
cy cle recirculating s ys tem (CCRS): limited land availability and proximity

to an airport
. 10

7 See elsewhere in the record for the proposed rule. 8 Three sampling events were for one hour and the fourth was a 24
- hour collection. 9 Test species included bluegill, channel catfish, and fathead minnows. Approximately 2400 fish were introduced in front of the screen. 10 The airport is 2 miles from North Omaha.4

7.0 Debris Handling The facility

has had significant problems with debris in the past. Spring (with rising water levels carrying deposited materials) and fall (leaves and grasses) are the heaviest times of ye ar. Sticks, sand , gravel , and rocks eventually clog the condenser and require a shutdown for cleaning. Facility representatives noted that fine sand is the most troublesome, as it wears parts and clogs screen spray nozzles. The facility

has a permit from the Army Corps of Engineers for sed iment and debris removal. The facility

ty picall y overhauls the traveling screens every 3 to 4 ye ars. On the average, 4 screens are overhauled per ye ar at an annual cost of $586,000. Average river flow at the facility is 28,850 cubic feet per second (18, 646 mgd) with an average velocity

of 7 fps. 8.0 Repowering/Future Uses As noted in Section 4.0 above, North Omaha has CWI S infrastructure in place to add a Unit 6, but currently has no plans for expansion. 9.0 Cooling Ponds There are no cooling ponds on site. 10.0 Ownership OPPD is a public utility

that is owned b y 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 y ear 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 A recently

re - lined onsite a sh pond is used for bottom ash. Much of the bottom ash can be sold for beneficial uses, but this is not done on a consistent basis as of ye t. The pond is serviced every 10 y ears and was constructed as an in
- ground pond (with no berms). Most of the ash i s collected in hy drobins.5 Fly ash is handled dry

and stored at an onsite landfill. A significant portion is also sold for use in concrete, as minimal material has been added to the landfill in recent months. 13.0 Air Emissions Controls North Omaha Station utilizes the following air emission controls:
Boiler ID Type NO x control PM control Other control
NO1 Tangential
- fired Cold
- side electrostatic precipitator Ammonium Nitrate

Injection [Opacity]

NO2 Tangential
- fired (1) Low
- NO x burners ; (2) Over
- fire air Cold
- side electrostatic precipitator Ammonium Nitrate Injection [Opacity ]

NO3 Tangential
- fired (1) Low
- NO x burners ; (2) Over
- fire air Cold
- side electrostatic precipitator Ammonium Nitrate Injection [Opacity]

NO4 Tangential
- fired Cold
- side electrostatic precipitator Ammonium Nitrate Injection [Opacity]

NO5 Wall
- fired Low
- NO x burner s Cold
- side electrostatic precipitator

14.0 Additional Information Facilit y representatives stated that, based on the results of the WI P screen testing, they likel y would have pursued the installation of WI P screens at all intakes to comply with the 2004 Phase II rule. They did note that the calculation baseline might have been problematic to calculate due to low impingement rates. Facility representatives added that meeting entrainment requirements would be very difficult given the river conditions , as f ine mesh screens would require a significant expansion of the CWI S and that they question the feasibility of fine mesh screens in a high debris river
. Additionall y, the state permitting authority noted that the portion of entrained organisms is a small percentage of the total number of organisms in the river. Summer (March to October) is navigation season on this portion of the Missouri River. The Ar

my Corps of Engineers regulates the season and determines water releases from reservoirs upstream.6 Facilit y representatives stated that facilities in Nebraska that are not located on a major river (i.e., inland facilities) have been restricted by state re gulations from any further surface water withdrawals that would result in consumptive uses (except for domestic use)
. Facilit y representatives stated that they have been experiencing some problems in meeting effluent limitations guidelines for metal clean ing wastes. Service water is withdrawn from groundwater wells and treated by reverse osmosis before being used in the plant. Due to high ambient levels of iron (which is not removed by the reverse osmosis), the ash pond effluent has shown elevated iron l evels as well. Attachments Attachm ent A List of A ttendees Attachment B Aerial Photo s Attachment C North Omaha Facility Description Attachment D Engineering Diagrams Attachment E In formation on Debris Attachment F WIP Screen Presentation Attachment G S ite Visit Photos7

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 Greg Krieser , OPPD Ron Stohlmann, OPPD Timothy Yager, OPPD Mike Krumland, Nebraska Public Power District (NPPD) Joe Citta, NPPD Justin Reimers, NPPD Brian Hittle, Beaudrey8

Attachment B -- Aerial Photos Please see DCN 10
- 6521A accompanying this document Attachment C

—North Omaha Facility Description Please see DCN 10
- 6521B accompanying this document Attachment D

—Engineering Diagrams Please see DCN 10
- 6521C accompanying this document Attachment E

—Information on Debris Please see DCN 10
- 6521D accompanying this document Attachment F

—WIP Screen Presentation Please see DCN 10
- 6521E accompan yi ng this document Attachment G

— Site Visit Photos Please see DCNs 10
- 6521F through Q accompan ying this document