Document ID: EPA-HQ-OW-2008-0667-0017
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-11-05T05:00Z

Site Visit Report

	Chalk Point Generating Station

25100 Chalk Point Road

Aquasco, MD

December 3, 2007

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.  Chalk Point Generating
Station (Chalk Point) was selected for a site visit due to its use of
fish barrier nets and its proximity to the Washington, D.C. area.

Facility Description

Chalk Point is located on 1160 acres along the Patuxent River and
employs approximately 250 people.  The facility is owned by Mirant
Corporation and began operations in 1964.

The facility’s NPDES permit (MD0002658) is up for renewal, as it
expired on January 31, 2007.  A facility representative stated that they
have not seen the latest permit language regarding section 316(b)
compliance, but assumed that the state would be making a best
professional judgment (BPJ)-based determination of best technology
available (BTA).

Electricity Generation and Transmission

Chalk Point has 11 generating units with a total generating capacity of
2400 megawatts (MW), making it the largest power producer in the state. 
Overall, the facility has a capacity utilization rate (CUR) of about
35%.  Units 1 and 2 (coal-fired units that began service in 1964 and
1965) generate 341 MW (net) each.  As baseload units, they are the most
commonly used units and have a CUR between 60-75%.  Units 3 and 4 are
among the largest cycling units in the Pennsylvania/New Jersey/Maryland
(PJM) electricity market.  Unit 3 was installed in 1975; unit 4 in 1981.
 These units generate 612 MW (net) when burning oil, or 582 MW (net)
when burning gas.  Seven combustion turbines (installed between 1967 and
1991) provide additional peaking power.  Two of these turbines are
“blackout” turbines, which can be used to provide startup power to
the baseload generating units in the event of a widespread power outage.
 The facility has a routine four week shutdown for maintenance each
year, which is coordinated with PJM.  It is also not uncommon for the
outage to last 5-6 weeks.

The facility burns bituminous coal from the Maryland, West Virginia, and
Pennsylvania area.  Coal is pulverized to a powder-like consistency and
is blown into the combustion chamber of Units 1 and 2.  Units 3 and 4
are capable of using either natural gas or fuel oil, but during the
ozone season (May through September) burn only gas.  These units use #6
fuel oil, which is delivered via a 50 mile pipeline from Piney Point. 
The facility’s use of oil is regulated by a consent decree with the
state regarding the sulphur content of the oil. The combustion turbines
burn gas or #2 fuel oil, which is trucked to the site.  

PEPCO owns the switchyard at the facility.

Cooling Water Intake Structure

Units 1 and 2 have separate intake structures, both located at the end
of an intake canal also known as Swansons Creek.  Two sets of barrier
nets at the end of the canal exclude organisms from the area of the
intake structure.  The nets were originally installed to prevent
juvenile blue crabs from clogging the condenser tubes.  The outer net
has a “stretch” mesh size of approximately 1.5 inches and is
primarily intended to exclude jellyfish and enable the inner net (mesh
size of 3/8”) to properly exclude other organisms.  The inner net is
changed twice a week in the fouling season.  Generally, four people in
two boats spend approximately two hours replacing individual sections of
netting.  The fouled nets are taken onshore, dried, and shaken to remove
any material.

The first layer of screening at the CWIS for Units 1 and 2 is provided
by a bar rack, which excludes large debris.  The CWIS also has 4
traveling screens per unit with a standard 3/8” mesh size and return
fish to the discharge canal via an open fiberglass trough.  The screens
were replaced in 2004 and are rotated approximately once per month. 
Units 1 and 2 have a total of 4 intake pumps, each rated at 125,000 gpm.
 Sodium hypochlorite is added at the inlet screen for biocide control. 
A one mile discharge canal returns heated effluent to the waterbody. 
There is a 20° F temperature differential at full load.  The long
length of the canal was intended to provide for some heat dissipation,
but it has ultimately not been as effective as originally hoped.

The total design intake flow (DIF) is 720 million gallons per day (mgd).
 The average intake flow is approximately 700 mgd.

The design intake velocity for the CWIS is 1.0 feet per second.

Chalk Point also has two natural draft cooling towers that serve Units 3
and 4.  The towers were installed to reduce thermal loading to the
receiving waterbody and withdraw makeup water from the discharge canal
of Units 1 and 2.  Typically, 2 of the 3 makeup water pumps (each rated
at 18,000 gpm) are operating, with the third as a backup.  Cooling tower
blowdown is sent to settling ponds, which then empties into the
discharge canal.

Boiler water is also withdrawn from the intake canal and is
demineralized and polished before being added to the boiler.

Impingement and Entrainment Information

To comply with the now-suspended Phase II rule, the facility stated that
it had intended to demonstrate that the barrier nets met the impingement
requirements; the facility also planned to demonstrate that the onsite
fish hatchery met the entrainment requirements of the rule.  Facility
studies have shown that the impingement reduction due to the barrier net
is over 80%.  This reduction was calculated based on population
fluctuations from year to year.  By looking at the most commonly
impinged species and comparing the estimated population changes in the
source waterbody, the reduction in impinged organisms was determined.

The facility has also considered other options for reducing impingement
and entrainment.  A representative from the Electric Power Research
Institute (EPRI) added that the barrier nets could likely be optimized
to improve their performance.  For example, some larvae pass through the
nets (i.e., they are smaller than the mesh size, but are not drawn into
the intake structure) and remain until adulthood, when they are too
large to bypass the nets and leave the intake canal.  These fish are
often eventually impinged, as they can not escape.  Another optimization
technique may be to enlarge the surface area of the nets and reduce the
through-net velocity to 0.5 feet per second, meeting the impingement
standards.  With respect to the cooling towers, facility representatives
stated that there is generally no flexibility to add any cooling water
flows to the towers, as they were purpose-built to service Units 3 and
4.  Similarly, they noted that expanding the shoreline intake structure
would be significantly more expensive and likely not provide any
incremental benefit over optimization of the barrier nets.  Maryland’s
Power Plant Research Program (PPRP) also conducted a study on wedgewire
screens at the intake structure and noted approximately a 65% reduction
in entrainment.  However, the screens were not considered further, as
the state assumed that the barrier nets and hatchery restoration would
be sufficient to comply with the Phase II rule.

Cooling Tower Feasibility

Chalk Point has two natural draft towers in place.  According to plant
staff, installing additional cooling towers would also be difficult, as
there is not sufficient usable space, despite the large site.  Facility
representatives stated that much of the unused acreage at the site is
wetlands, committed to other processes, or is owned by PEPCO.  They
added that existing uses (such as the coal pile or oil tanks) could be
relocated, but the site is very complex and has a large number of
existing pipes and power lines.  Additionally, they noted that much of
the nearby space is being used to construct a new scrubber for air
pollution compliance.  A representative from EPRI noted that state
permitting issues may also restrict land uses, including shoreline
development and forest protection regulations.  The facility has also
committed significant resources to wetland restoration nearby, including
observation areas.  A facility representative stated that any new tower
construction would likely use mechanical draft towers instead of natural
draft.

Additional Information

To comply with requirements of the Maryland Healthy Air Act, the plant
is in the process of upgrading its air pollution controls.  A selective
catalytic reduction (SCR) system is being installed on Unit 1 to reduce
NOx emissions; a selective auto-catalytic reduction (SACR) system is
already in place for Unit 2.  The plant is also installing a limestone
forced oxidation flue gas desulfurization (FGD) system to reduce SO2
emissions from units 1 and 2.  A single FGD absorber will scrub the flue
gases from both units.  Ground water will be used as the makeup water
source for the FGD system. 

Attachments

Attachment A		List of Attendees

Attachment B		Aerial Photos

Attachment C		Slideshow Presentation

Attachment A—List of Attendees

Paul Shriner, EPA

Jan Matuszko, EPA

Josh Hall, EPA

Ron Jordan, EPA

Erik Helm, EPA

Paul Balserak, EPA

Mary Smith, EPA

Richard Witt, EPA

Suzanne Rudzinski, EPA

Julie Hewitt, EPA

Kelly Meadows, Tetra Tech

John Sunda, SAIC

Shawn Konary, Mirant

Ann Wearmouth, Mirant

Greg Staggers, Mirant

Dave Bailey, EPRI

Also see DCN 10-6504A for an electronic copy of the sign-in
sheet.Attachment B—Aerial Photos

Please see DCN 10-6504C accompanying this document.

Attachment C--Slideshow Presentation

Please see DCN 10-6504B accompanying this document.

 The facility has operated a fish hatchery (the largest in the state)
for over 20 years.  The hatchery was originally used to raise striped
bass and is currently producing sturgeon and shad, based on direction
from the state fisheries agencies.  The facility’s NPDES permit
contains provisions for restoration via the fish rearing. The facility
had an agreement with the state that the continued operation of the
hatchery would be sufficient to meet the entrainment requirements of the
Phase II rule.

 Additionally, re-piping the towers to service Units 1 and 2 would
effectively take Units 3 and 4 out of service and greatly inhibit the
facility’s ability to meet peak generating demand.  The two pairs of
units also have different condenser designs, making such an operational
change more difficult.

 Mirant is also planning to install FGD systems at its Dickerson plant
(one absorber, using river for makeup water source) and Morgantown plant
(two absorbers, initially using ground water but will transition to
treated POTW effluent after 2010). 

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