Document ID: EPA-HQ-OW-2008-0667-1265
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-04-20T04:00Z

Site Visit Report

	Mercer Generating Station

	Lamberton Road

	Hamilton Township, NJ 08611

May 26, 2010

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.  Mercer was selected for
a site visit due to its proximity to EPA Headquarters and its location
on a large tidally influenced freshwater river.

Facility Description

Mercer is located on a 115 acre site outside of Trenton, along the
Delaware River, and began operations in 1960.  The facility is owned by
PSEG and employs approximately 125 people.  The facility’s NPDES
permit (NJ0004995) is due to expire on October 31, 2011.

Electricity Generation and Transmission

Mercer has two coal-fired generating units, each with a generating
capacity of 300 MW (600 MW total).  The facility typically uses eastern
bituminous coal from West Virginia.  The coal (delivered by barge) is a
premium grade with low sulfur content.  Mercer is a load-following
plant, with a capacity factor in recent years of approximately 50-70%.

The facility has routine maintenance outages approximately every 18
months.

Unit 3 is an old 8-turbine expander turbine generating unit (125 MW
total) that is rarely operated and will be decommissioned in 2015.

Cooling Water System and Intake Structure

Mercer uses a once-through cooling system and operates a shoreline CWIS.
 The intake structure is comprised of a trash rack/ice barrier followed
by coarse mesh traveling screens (1/2 by 1/4 inch mesh).  There are 4
screens, each with a single fixed speed circulating pump and a service
water pump, with a total design intake flow of 610 million gallons per
day (mgd).  The design through-screen velocity is approximately 1.5 feet
per second (fps).  The facility is permitted to use chlorine as a
biocide for up to three 20 minute cycles per day.  The facility is also
capable of redirecting heated effluent to the CWIS in the winter to
prevent ice formation.

As part of the requirements in their current NPDES permit, Mercer will
be installing new Ristroph screens with a new directional (i.e., will
discharge fish in the direction of the tidal current) fish return and
dual pressure spray wash next year.  The screens will be continuously
rotated from May to October.  The new screens will cost approximately $8
million.  PSEG selected the Ristroph screens over other designs due to
the familiarity from using them at other sites and known performance. 
Mercer will be required to conduct 2 years of verification monitoring
following the installation of the new screens.

Impingement and Entrainment Information

The facility conducted extensive impingement and entrainment studies in
the 1990s (one in 1991-1992 and another in 1998-1999) and did not find
significant impingement, even during the large shad runs each spring.

Cooling Tower Feasibility

The facility has not extensively studied a potential retrofit to
closed-cycle cooling.  Facility representatives noted significant
economic challenges (see Section 14.0), as well as space constraints;
the facility’s recently constructed air emissions controls occupy much
of the space near the facility.  Facility representatives also noted a
nearby highway that could be affected.  See Section 12.0 below for
information on other potentially available space.

Mercer has a wastewater treatment facility onsite and facility
representatives assumed that it would be capable of handling additional
flow from cooling tower blowdown if the site were required to retrofit
to closed-cycle cooling.

Debris Handling

Mercer does not have significant problems with trash or debris. 
Episodic debris events occur in spring, when accumulated woody debris is
flushed into the river.

Repowering/Future Uses

Facility representatives stated that there are no plans to expand the
facility; at present, Mercer provides PSEG with valuable fuel diversity
in its generating fleet.

Cooling Ponds

	

There are no active cooling ponds on site.  Two ash ponds are no longer
in service; see Section 12.0.

Ownership

Mercer is owned by PSEG, an investor-owned company. PSEG has fossil
plants in New Jersey, Connecticut, New York and Texas, plus nuclear
plants in New Jersey.

316(a)

Mercer is subject to thermal discharge limits (discharge temperature,
total heat load, and delta T) and has a 316(a) variance that was
developed in the 1990s.

Ash Handling

Bottom ash is used for roofing and other products, while fly ash is also
used for beneficial uses.

Mercer previously operated two ash ponds just northeast of the
generating units, but decommissioned these ponds in the 1990s.

Air Emissions Controls

Mercer is constructing a dry scrubber for each generating unit to
address SOx.  These units will become operational in late 2010.  The
facility also installed electrostatic precipitators in the 1990s to
collect dust and particulate matter.  In 2004, they added an SCR to
address NOx emissions.  By adding each of these control technologies,
the facility has greater flexibility in the types of coal that it can
use.  Facility representatives noted that PSEG is closing 2000 MW of
generating capacity as a result of compliance with air regulations. 
They added that new units are being added at some facilities, but that
the company will not recover all of the lost capacity.

Additional Information

In response to the now-suspended 2004 Phase II rule, facility
representatives stated that Mercer was likely to pursue the cost-benefit
test, given the low impingement and entrainment rates at the site.  They
noted that NJDEP was likely to be supportive of this, as they generally
consider Mercer to be a site with low biological impacts.

Facility representatives stated that the revised rule should contain a
site-specific option, as cooling towers are not a sensible choice for
facilities such as Mercer.  They believe that a cost-benefit test is the
most direct approach, but other options (such as pre-approved
technologies for certain categories of facility) may also be available. 
Facility representatives note that PSEG operates a number of facilities
that are only marginally profitable; a rule requiring closed-cycle
cooling could have a significant effect.

Merryll Reservoir is a large off-river reservoir upstream of the site
that was constructed by power plants in the area to provide supplemental
water supplies in times of extreme drought.

PSEG deployed a Gunderboom at another facility (Bethlehem Energy Center)
and experienced significant problems.  The first-of-its-kind fixed panel
barrier failed each season it was deployed for a variety of reasons.

Bergen is a sister station to Mercer and recently repowered to combined
cycle with cooling towers (with plume abatement); a nearby WWTP supplies
the makeup water for the towers.

Attachments

Attachment A		List of Attendees

Attachment B		Aerial Photos

Attachment C		Site Visit Photos

		

Attachment A--List of Attendees

Paul Shriner, EPA Headquarters

Erik Helm, EPA Headquarters

Tom Born, EPA Headquarters

Shari Goodwin, Tetra Tech

Kelly Meadows, Tetra Tech

Mark Strickland, PSEG

Carmine DeNicola, PSEG

Mark Schwartzkopf, PSEG

Attachment C—Site Visit Photos

Please see DCNs 10-6558B through L accompanying this document.

 EPA was unable to provide a copy of this report to the facility for
review prior to publication.

 Mercer is located in the freshwater portion of the Delaware River, but
does experience tidal surges of up to 7 feet.  Approximately 3 miles
downriver, the Delaware is generally considered to be tidal/brackish.

 The facility has 3 pulverizers to provide fuel to the generating units.
These units can also burn natural gas.

 Each circulating pump is rated at 105,000 gpm, while each service water
pump has a capacity of 875 gpm.

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