Document ID: EPA-HQ-OW-2008-0667-0002
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-11-05T05:00Z

Site Visit Report

	Barney Davis Power Station

	4301 Waldron Road

	Corpus Christi, TX 78418

March 3, 2008

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.  Barney Davis Power
Station (Barney Davis) was selected for a site visit due to its use of
fine mesh traveling screens and its large intake flows.

Facility Description

Barney Davis is located on a 2000 acre site in Corpus Christi, Texas. 
It withdraws water from the Laguna Madre estuary via a 1200 foot long
intake canal.  Heated effluent is discharged to a cooling pond west of
the facility, eventually flowing into Oso Bay.  The facility is owned by
Topaz Power Group and began operations of the first unit in 1974 and the
second unit in 1976.

The facility’s NPDES permit number is TX0008826, which expired on
December 5, 2006.  A permit renewal application has been submitted, but
the renewed permit is awaiting EPA approval and has not been issued by
the state.

Electricity Generation and Transmission

The facility has two natural gas-fired generating units, each capable of
generating 350MW.  The facility operates during times of high demand,
typically only in the summer; its capacity utilization is approximately
5%.  The facility has one scheduled outage per year, which typically
occurs during a time when demand is low.

Unit 2 is currently being upgraded to include a heat recovery steam
generator (HRSG) to increase its generating efficiency.  When completed
in 2010, the facility expects that its utilization will increase.  Unit
1 has no additional upgrades planned at this time.

American Electric Power (AEP) owns the switchyard and transmission
equipment.

Cooling Water Intake Structure

Water is withdrawn from Laguna Madre, a shallow estuary connecting to
the Gulf of Mexico with approximately 1 foot of tidal variation.  An
intake canal draws water to a shoreline intake structure adjacent to the
plant.  Boat traffic is blocked at the canal entrance.  Low currents and
predominant south to east winds cause broken or shed pieces of sea grass
(called wrack) accumulation along the western side of the Laguna Madre
that is drawn into the canal at the intake. A mechanical trash rack
(3.5” spacing between bars) screens debris, including extremely heavy
loadings from sea grasses.  Barney Davis was originally designed and
built with fine-mesh screens (single entry, double exit Passavant center
flow screens).  The screens are made of a semi-rigid polymer-based mesh
with 1mm by 2mm openings and typically must be replaced every 2-3 years.
 Impinged organisms are washed off the screens as the basket reaches the
top of its cycle into the trough and then into a holding well, where
they are pumped to a floating surface discharge in the cooling pond. 
One FTE oversees operation of the CWIS equipment. The facility cleans
the condenser tubes with Amertap balls which has allowed the facility to
avoid the use of chlorine and biocides.

Once a year (during the planned facility outage), Barney Davis performs
maintenance on the system.  They remove the baskets, inspect the chain
and all moving parts, and replace parts as needed.  They hydroblast the
exterior system to remove oyster shells and mussels as needed. Both the
screens and baskets are made locally.

Barney Davis’ uses four circulating pumps, each rated at 82,000 gpm
(equal to a design intake flow (DIF) of 472 mgd) and the design intake
velocity has been calculated as 1.15 fps.  There will be no increase in
cooling water flows due to the addition of the HRSG.  The condenser is
single pass and consists of titanium tubes.  

Impingement and Entrainment Information

The facility has recently conducted impingement and entrainment
monitoring and provided an interim report (see Attachment D).  A study
of organism survival was also conducted in 1977.  The facility did not
plan to make any operational or technological changes to comply under
the now-suspended Phase II rule; facility representatives believe that
the current configuration demonstrates compliance.  Representatives also
stated that a small number of fish species represent the bulk of the
impingement at the facility.

Cooling Tower Feasibility

Facility representatives noted that, due to the shallow depths in Laguna
Madre and summer weather conditions (heat and drought), the intake water
for Barney Davis can become hyper-saline (as high as 50 parts per
thousand).  Some stainless steel parts of the screen assembly have been
replaced with Teflon-coated parts to reduce the effects of corrosion. 
Facility representatives stated that the high salinity levels could be
problematic for operation of a cooling tower, as frequent blowdown would
be required and corrosion of equipment may be accelerated.  They also
noted that the high summer temperatures would likely result in a
significant increase in evaporation rates of the cooling tower. 
Facility representatives also stated that salt drift would be a concern,
as Barney Davis is located next to a military airfield used for training
pilots.  When questioned on the feasibility of dry towers, the facility
noted that the ambient summer temperature is typically 100 degrees F,
which, in their opinion, makes dry cooling problematic.

Additional Information

The facility is considering upgrades to its intake system to reduce sea
grass intake by deflecting the floating sea grass at the entrance to the
intake canal.  (See Attachment E.)

Attachments

Attachment A		List of Attendees

Attachment B		Aerial Photos

Attachment C		Proposal for Information Collection

Attachment D		Draft Interim Impingement and Entrainment Report

Attachment E		Wrack Control

Attachment F		Site Visit Photos

Attachment A--List of Attendees

Paul Shriner, EPA

Jan Matuszko, EPA

Kelly Meadows, Tetra Tech

Gary Eddins, Topaz Power Group

Nick Andrade, Topaz Power Group

Val Sepulveda, Topaz Power Group

Paul Jensen, PBS&J

Attachment B—Aerial Photos

Please see DCN 10-6500D accompanying this document.

Attachment C—Proposal for Information Collection

Please see DCN 10-6500A accompanying this document.

Attachment D—Draft Interim Impingement and Entrainment Report

Please see DCN 10-6500B accompanying this document.

Attachment E—Wrack Control

Please see DCN 10-6500C accompanying this document.

Attachment F—Site Visit Photos

Please see DCN 10-6500E-K accompanying this document.

 Of the 2000 acres, approximately 1100 acres are dedicated to the
facility’s cooling pond, with additional acreage loaned to the state
wildlife agencies and universities for hatchery rearing operations and
research.

 The generating units previously could burn either natural gas or oil,
but this flexibility was removed during recent upgrades.

 The trash rack uses traveling rakes to clear debris.  Seagrass loading
is the biggest concern, as facility representatives noted that as many
as 15 truckloads of seagrass may be removed per day and placed on land
at the site.  The facility designates a full-time operator for the
system at all times during its operation to constantly monitor debris
loading levels.  

 The screen mesh (cloth with Teflon inserts) is fitted onto a
chain-driven metal frame.  Each piece of screen material is attached to
one of 52 baskets to form a trough.

 The screens are rotated continuously (typically at the maximum rotation
speed) when the generating unit is operating.  Originally, the fish
return was an open channel to Laguna Madre, but operational difficulties
and predation by seabirds prompted moving the fish return outfall to the
cooling pond.

 Amertap sponge rubber balls are passed through single-pass condenser
tubes as needed to maintain heat transfer efficiency.   

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