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Site Visit Report

Meramec Plant

8200 Fine Road

St. Louis, MO 63219

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 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. Meramec was selected for a site visit due to its location on a 

large freshwater river.

2.0 Facility Description

Meramec is located on a 264 acre site about 20 miles south of St. Louis on the 

Mississippi River. The facility began operations in 1953 and employs roughly

230 people.

Meramec is owned and operated by Ameren. The facility’s NPDES permit 

(MO0000361) expired May 18, 2005.1

3.0 Electricity Generation and Transmission

Meramec consists of 4 coal-fired2generating units3and has a total generating 

capacity of 835 MW. The units were commissioned between 1953 and 1961 and 

range in size from 125 MW to 300 MW. The facility’s capacity utilization rate 

(CUR) is approximately 76%.

Scheduled major outages at each unit occur every 6 years and vary in length 

depending on the tasks to be performed.

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

business unit.

 

1 Ameren submitted its renewal application in a timely manner and awaits the renewal of its permit.

2 The facility’s coal comes via rail from the Powder River Basin in Wyoming.

3 Units 1 and 2 are identical.
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4.0 Cooling Water System and Intake Structure

Meramec has one CWIS that withdraws once-through cooling water from the 

Mississippi River. The shoreline CWIS has a design intake flow (DIF) of 674 

million gallons per day (mgd)4and an average actual intake flow (AIF) of 550 

mgd. The CWIS has a common trash rack5and 8 intake bays (2 per unit), each 

with a single circulating pump and coarse mesh (3/8” mesh) dual flow traveling 

screen.6 The screens are rotated every 8 hours and are cleaned with a high 

pressure spray wash. The screens rotate slowly with a head differential across the 

screens of 18 inches and switch to a faster speed when the differential reaches 

three feet; during high debris loading periods, the screens often operate 

continuously. The debris return is a trough in the deck of the screenhouse and 

discharges at the downstream end (approximately 20 feet above the water line on 

the day of the site visit). The design intake velocity of the CWIS at Units 1 and 2 

is 1.2 feet per second (fps) and 1.3 fps at Units 3 and 4.

Routine maintenance includes visual inspections, repair or replacement of screen 

parts (about once per month), and a backwashing of sediment in the intake bay.

Meramec discharges heated effluent to the river approximately 200 feet 

downstream of the CWIS.

In the 1980s, Meramec added flow straighteners inside the CWIS to improve the 

flow of water through the screens and into the pumps; previously, there were 

issues with eddies within the pump well, occasionally leading to the intake of air.

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, Meramec conducted 24 hour impingement 

sampling every other week for a year for a total of 26 sampling events. 

Approximately 96% of the fish collected at Meramec were shad and drum. The 

sampling estimated an annual impingement total of approximately 166,000 fish 

including moribund fish.

6.0 Cooling Tower Feasibility

Meramec has not considered retrofitting to a closed-cycle recirculating system 

(CCRS). Facility representatives noted that the surrounding area has become 

much more developed over time, leading to potential permitting issues. They

 

4 The pumps for Units 1 and 2 have a capacity of 64.8 mgd each, Unit 3 a capacity of 86.4 mgd, and Unit 4 

a capacity of 115.2 mgd.

5 The facility is in the process of replacing its bar rack; the new design will have additional design features 

to improve debris handling, much like the one installed at Labadie. The face of the trash rack will be flat 

and flush with the front of the CWIS and a mechanical trash rake will also be installed.

6 Meramec replaced all of its traveling screens between 1999 and 2004; dual flow screens were selected to 

reduce debris carryover.
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noted the facility is surrounded by a steep bluff to the north, a wastewater 

treatment plant, the Meramec River, as well as neighboring homes and a golf 

course.

7.0 Debris Handling

Meramec has had significant problems with debris in the past (especially with 

spring and fall leaf loads), including 5 unit shutdowns since 2000.

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 Facility

representatives noted that a major debris event typically leads to 4-5 screen panels 

being damaged.

At the facility, the Mississippi River has an average flow of 171,400 cfs (110,779 

mgd), with average and maximum silt levels in 2007/2008 of 288 mg/L total 

suspended solids (TSS) and 1,140 mg/L TSS, respectively.

8.0 Repowering/Future Uses

Currently, Meramec has no plans for re-powering or upgrades.

9.0 Cooling Ponds

There are no cooling ponds on site.

10.0 Ownership

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

11.0 316(a)

Facility representatives stated that Meramec currently has no problems meeting its 

thermal discharge requirements. However, they noted any 316(b) solutions that 

involve flow reduction may cause an increase in the discharge temperature (in 

addition to the lost generation) which could lead to exceedances in its 316(a) 

water quality limits.

12.0 Ash Handling

Fly ash is handled dry and facility representatives noted that virtually all of the fly

ash is sold for beneficial uses. Approximately 5% of the bottom ash is sold; the 

remainder is sluiced to an on-site ash pond. A large volume of bottom ash was 

used in reconstructing the embankment at its Taum Sauk pumped storage facility.

Ameren has an internal team that conducts inspections of all earthen dams and 

similar structures. Due to a dam failure at the Taum Sauk facility in 2005, 

Ameren instituted rigorous inspections at all facilities. Facility representatives 

 

7 Unit 3 was the most frequently affected unit, despite its position in the center of the screenhouse.
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noted that Ameren’s inspections are more stringent than those conducted by state 

agencies.

13.0 Air Emissions Controls

EPA did not collect any information on air emissions controls.

14.0 Additional Information

Facility representatives stated that they had begun to evaluate intake technologies 

for compliance with the 2004 Phase II rule. One approach was to adapt the 

existing dual flow screens with Ristroph buckets, dedicated fish return, and to 

expand the CWIS for an estimated cost of $84 million ($2004). Other options 

included a Ristroph screen and dedicated fish return paired with a 20% flow 

reduction8for an estimated cost of $73 million; bar rack barriers with 1” spacing 

with a reduced through screen velocity of 0.5 fps for an estimated cost of $7.6 

million; coarse mesh wedgewire screens9for an estimated cost of $76 million; and 

a fixed screen with a bar rack fitted with 1⁄2” mesh for an estimated cost of $9.2 

million. 

Facility representative reiterated concerns over fine mesh screens, as well as other 

aspects of the rulemaking. Please refer to Section 14.0 of the site visit report for 

Labadie for a discussion of these issues.

Meramec has two coal piles onsite. This second pile was intended to be dualpurpose: one, as overflow storage for Meramec’s use (or to re-sell to other plants 

along the Mississippi) and two, to provide a waypoint for loading bargetransported coal onto trains for transport to inland facilities (or vice versa). 

However, the coal unloading dock was decommissioned in 2002; the dock for 

offloading coal onto a barge is still functional.

Attachments

Attachment A List of Attendees

Attachment B Aerial Photos

Attachment C Site Visit Photos

Attachment D Ameren PowerPoint Presentation (March 4, 2009)

 

8 A flow reduction of 20% could be achieved by throttling back generation; a bulkhead wall would be 

constructed in front of the existing intake and 20 wedgewire screens would be installed.

9 A bulkhead wall would be constructed in front of the existing intake and 20 wedgewire screens would be 

installed.
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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

Mark Matthews, EPA Region VII

Kelly Meadows, Tetra Tech

Steve Whitworth, Ameren

Mark Litzinger, Ameren

Nancy Morgan, Ameren

Mike Smallwood, Ameren

Mike Bollinger, Ameren

Kirk Schweiss, Ameren

Tim Lafser, Ameren

Keith Myers, Ameren

John Beck, Ameren
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Attachment B--Aerial Photos
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Attachment C— Site Visit Photos

Please see attached materials.

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

Please see attached materials.