Site Description Report

Sioux Power Plant

	8501 North State Route 94

	West Alton, MO 63386

March 4, 2009

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
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.  As part of its site
visit to the Labadie Power Plant, EPA also collected information on
Ameren’s Sioux Power Plant.

Facility Description

Sioux is located on the shoreline of the Mississippi River,
approximately 25 miles north of St. Louis.  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.

Electricity Generation and Transmission

Sioux is a 993 MW facility with two coal-fired generating units that
typically burns a coal blend from the Powder River Basin and Illinois. 
The capacity utilization rate (CUR) was approximately 66% in 2008.

Sioux schedules a major outage approximately every 3 years for
maintenance and upgrades.

Cooling Water System and Intake Structure

Sioux withdraws water from the Mississippi River via a ¼ 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 bays
(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 differential
is reached.  The screens are washed with a high pressure spray that
discharges back to the river via a discharge trough.  The design
through-screen intake velocity 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 Army Corps of Engineers and is
highest in the summer to allow for navigation.  Water levels are reduced
significantly during non-navigational periods.  During low water
periods, possible pump cavitation is a concern.

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
impingement sampling every other week for a year 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 estimated an annual
impingement total of approximately 1.8 million fish.  The facility did
not conduct any source waterbody characterization studies; there is
ample publicly available research on the Mississippi.

Cooling Tower Feasibility

EPA did not collect any information about CCRS at this site.

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 years the facility has lost
an average of one generating day per year to debris or icing.

Twice per year, the facility uses a crane barge to remove large debris
from the trash racks.  The traveling screens are inspected twice per
year and the CWIS is inspected once per year by a diver.  As needed,
Sioux overhauls the screens during the plant’s regularly scheduled
outages every three years. 

Repowering/Future Uses

There are currently no plans to expand generating capacity or make other
significant operational changes at Sioux.

Cooling Ponds

	

There are no cooling ponds onsite.

Ownership

Sioux is owned by Ameren, an investor-owned company.

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.

Ash Handling

Sioux has a clay-lined fly 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 currently 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 by state agencies.

Air Emissions Controls

EPA did not collect any information about existing air controls at this
site.  However, facility representatives indicated that scrubbers were
currently being constructed at the site.

Additional Information

Facility representatives stated that they had begun to evaluate intake
technologies for compliance with the 2004 Phase II rule.  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) 

Deployment of a ¼” year-round barrier net at the canal entrance
yielding an approach velocity of 0.2 fps for an estimated capital cost
of $29 million

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 velocity of 1.0 fps and fish return
with scenarios for an expanded CWIS or existing CWIS and 21% flow
reduction for an estimated cost of $63.4 million and $58 million,
respectively

Facility representatives also stated that restoration was an attractive
approach, especially from a cost-effectiveness standpoint.

Facility representatives noted that Sioux is located in an area with
significant navigation traffic.  Additionally, since the facility is
located in a lock and dam region, the water level is controlled by the
Army Corps of Engineers; it can vary by as much as 7 feet.

Attachments

Attachment A		Ameren PowerPoint Presentation (March 4, 2009)

Attachment A—Ameren PowerPoint Presentation (March 4, 2009)

Please see the attached materials.

 During periods of high debris, the screens may be rotated continuously.

 Facility representatives noted that impingement rates may be higher
than normal due to the intake canal; fish may enter the canal as a
resting place from the fast-moving river.

 This evaluation did not include technologies to address entrainment.

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