1 Site Description Report Sioux Power Plant 8501 North State Route 94 West Alton , MO 63386 March 4 , 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 under stand the 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 understand cooling water use and specific issues or technologies that can affect 316(b) compliance. As part of its site visit to the Labadie Power Plant, EPA also collected information on Ameren ’s Sioux Power Plant. 2.0 Facility Description Sioux is loc ated on the shoreline of the Mississippi River, approximately 25 miles north of St. L ouis. The facility began operations in 1967 on a 994 acre site and operates under NPDES permit MO0000353 ; the permit is due to expire April 15, 2009. 3.0 Electricity Generat ion and Transmission Sioux is a 993 MW facility with two coal

- fired generating units that ty pically burns a coal blend from the Powder River Basin and I llinois . The capacit y utilization rate (CUR) was approximately 66% in 2008

. Sioux schedules a major o utage approximately every 3 y ears for maintenance and upgrades. 4.0 Cooling Water System and Intake Structure Sioux withdraws water from the Mississippi River via a 1⁄4 mile intake canal just above the last set of locks and dams. The mouth of the intake canal is protected by a log boom. The CWIS has 4 intake bay s (designated as 1A, 1B, 2A, and 2B), each with a bar screen, single circulating pump and coarse mesh (1/2” mesh) traveling screen. The screens rotate once per shift or when a pre

- determined head diff erential is reached. The screens are washed with a high pressure spray that2 discharges back to the river via a discharge trough. 1 The design through

- screen intake velocit y is 1.4 feet per second (fps). The design intake flow (DIF) is 749 million gallons per day (mgd) and the average actual intake flow (AIF) is 619 mgd. The river elevation is controlled by the Arm y Corps of Engineers and is highest in the summer to allow for navigation. Water levels are reduced significantl y during non - navigational peri ods. During low water periods, possible pump cavitation is a concern. 5.0 Impingement and Entrainment Information Ameren conducted impingement studies at all of its Phase II facilities in 2005 and 2006. During the sampling period, Sioux conducted 24 hour i mpingement sampling every

other week for a ye ar for a total of 26 sampling events. Approximately

98% of the fish collected at Sioux were shad and drum. Many of the fish were collected between November and February and many

were moribund. The sampling es timated an annual impingement total of approximately 1.8 million fish. 2 The facility did not conduct any

source waterbod y characterization studies; there is ample publicl y available research on the Mississippi. 6.0 Cooling Tower Feasibility EPA did not coll ect any

information about CCRS at this site. 7.0 Debris Handling As with other facilities located on large rivers, Sioux experiences significant debris loading. In the past, traveling screens at Sioux have collapsed and debris has damaged the bar screens. Facility representatives stated that over the last 5 ye ars the facility

has lost an average of one generating day per y ear to debris or icing. Twice per year, the facility uses a crane barge to remove large debris from the trash racks. The traveling scre ens are inspected twice per ye ar and the CWI S is inspected once per ye ar by a diver. As needed, Sioux overhauls the screens during the plant’s regularly scheduled outages every three y ears. 8.0 Repowering/Future Uses

1 During periods of high debris, the screens may be rotated continuously. 2 Facility representatives noted that impingement rates may be higher than normal due to the intake canal; fish may enter the c anal as a resting place from the fast

- moving river.3 There are currently

no plans to expand generating capacity or make other significant operational changes at Sioux

. 9.0 Cooling Ponds There are no cooling ponds onsite. 10.0 Ownership Sioux is owned by

Ameren, an investor

- owned company

. 11.0 316(a) Sioux has a 316(a) BTU heat rejection requirement, but has had no problems meeting its limit. The facility has never had to change its operations or generation to meet thermal limits. 12.0 Ash Handling Sioux has a clay

- lined fl y ash pond, as well as a bottom ash pond. Fly ash is handled wet and sluiced to the pond. All of the bottom ash that is currentl y generated is sold, but some residual bottom ash remains in the pond. Ameren has an internal team that conducts inspections of all earthen dams and similar structures. Due to a dam failure at the Taum Sauk pumped storage facility in 2005, Ameren instituted rigorous inspections at all facilities. Facility representatives noted that Ameren’s inspections are more stringent than those conducted b y state agencies. 13.0 Air Emissions Controls EPA did not collect any

in formation about existing air controls at this site. However, facility

representatives indicated that scrubbers were currentl y being constructed at the site. 14.0 Additional Information Facilit y representatives stated that they had begun to evaluate intake te chnologies for compliance with the 2004 Phase II rule. 3 A number of technologies were evaluated:  A bar rack with 1” spacing and an approach velocity of 0.4 fps at the entrance to the intake canal for an estimated capital cost of $34 million ($2002)  Deplo ym ent of a 1⁄4” ye ar - round barrier net at the canal entrance yi elding an approach velocit y of 0.2 fps for an estimated capital cost of $29 million

3 This evaluation did not include technologies to address entrainment.4  Coarse mesh wedgewire screens on a bulkhead at the canal mouth (approximately

eight 7’ diameter screens) for an estimated cost of $61.5 million  Ristroph screens with an approach velocit y of 1.0 fps and fish return with scenarios for an expanded CWI S or existing CWIS and 21% flow reduction for an estimated cost of $63.4 million and $58 million, respectivel y Facilit y representatives also stated that restoration was an attractive approach, especiall y from a cost

- effectiveness standpoint. Facilit y representatives noted that Sioux is located in an area with significant navigation traffic. Additionally , since the facil ity is located in a lock and dam region, the water level is controlled by the Arm y Corps of Engineers; it can vary by as much as 7 feet.
Attachments Attachment A Ameren PowerPoint Presentation (March 4, 2009)5

Attachment A

— Ameren PowerPoint Presentati on (March 4, 2009) Please see the attached materials.