Document ID: EPA-HQ-OW-2008-0667-0013
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-11-05T05:00Z

Site Visit Report

	Seabrook Station

	626 Lafayette Road

	Seabrook, NH 03874

April 17, 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.  Seabrook Station
(Seabrook) was selected for a site visit due to its use of an offshore
intake location (with a velocity cap) and its large intake flow.

Facility Description

Seabrook is located near the town of Seabrook, New Hampshire,
approximately 2 miles from the Atlantic Ocean, the facility’s source
of cooling water.  The facility started construction in 1976, but due to
permitting delays, did not begin operations until 1990.  Seabrook is
owned by Florida Power and Light (FPL) and employs approximately 1000
workers.

The facility is located on a 900 acre site, of which approximately 600
acres is marshland.  The facility owns the marsh areas in order to
maintain a 3000 foot exclusion zone for security purposes.

Seabrook’s permit (NH0020338) expired in April 2007 and is currently
under an administrative extension.

Electricity Generation and Transmission

Seabrook operates one nuclear generating unit with a generating capacity
of 1250 MW.  The facility’s capacity utilization rate is over 90%; it
has a scheduled outage of 29 days every 18 months for refueling.

The facility’s switchyard is also owned by FPL.  Due to previous icing
problems, the switchyard equipment is gas insulated, reducing its total
footprint by approximately 4 times.

Cooling Water Intake Structure

Seabrook withdraws cooling water for its once-through cooling water
system from three offshore intake structures (approximately 7000 feet
from shore).  Water depth at the structures is approximately 60 feet and
the structures themselves are approximately 10-15 feet from the ocean
bottom.  The intakes are outfitted with 30 foot diameter velocity caps. 
The velocity caps have bar screens spaced 5 inches apart.  Facility
representatives estimate that the design intake flow is 0.5 feet per
second based on the design criteria for the intake structure.  Water is
drawn into a small forebay inside the screenhouse just prior to the
intake screens.  Seabrook’s traveling screens are a standard 3/8”
mesh and rotate when triggered by a sufficiently large head
differential.

The facility’s design intake flow is 684 million gallons per day (MGD)
and actual intake flows are 580 MGD.

Seabrook’s discharge is also offshore, although slightly closer to
shore than the intake structures.  The facility uses a series of
diffusers and has a discharge temperature limit of not more than a 5
degree change above the ambient temperature.

Seabrook uses chlorination 10 months per year to reduce biofouling.

Impingement and Entrainment Information

Seabrook has conducted annual monitoring since operations commenced in
1990.  Currently, the facility monitors impingement and entrainment
twice per week.

Most recently, the data has been used to develop a model that accounts
for changes in habitat between the sampling stations.  Facility
representatives noted that impingement events are often closely tied to
storms and impingement does not appear to be directly related to flow.

Facility representatives noted a paper presented at an American
Fisheries Society meeting that suggested the annual age-1 equivalent
losses at a power plant were comparable to only a few days of commercial
fishing.  They suggest that using an age-1 equivalent approach would
normalize the impingement and entrainment rates and would be an easier
regulatory approach to implement.

Cooling Tower Feasibility

Facility representatives stated that EPA Region I has requested
information via CWA Section 308 letters to inform the facility’s
permit renewal; the information requested is very similar to the
information that would have been submitted in the Comprehensive
Demonstration Study from the 2004 suspended Phase II rule.  (See
Attachment E.)  These documents were to be submitted in the summer of
2008 and included an analysis of alternative intake technologies and
conversion to closed cycle cooling.  The preliminary information from
the cooling tower study (at the time of the site visit) indicated that
54 cells would be required for a mechanical draft tower (occupying a
2700 ft by 200 ft area) and that there is no single parcel available
onsite that would provide sufficient space.  Additionally, facility
representatives stated that Seabrook is the largest local user of
freshwater, so cooling tower makeup water may not be available from
municipal sources.

Additional Information

Facility representatives stated that they had not formalized any plans
to comply with the now-suspended Phase II rule.  They faced initial
challenges in defining the facility’s calculation baseline due to the
offshore intake location, but opted to use comparable data from the
nearby Pilgrim Generating Station.  Facility representatives believe
that the facility was likely to be close to meeting the performance
standards.

Facility representatives stated that a facility should be given credit
for impingement and entrainment reductions for outage periods.  They
added that Millstone and Pilgrim have this type of arrangement.

Facility representatives stated that studying only the most abundant
species in future monitoring efforts may not reduce the burden, as many
of these species are not well-studied in the biological literature.

Facility representatives stated that early designs for the intake
structure were to use a shoreline intake that would withdraw from Browns
River and the adjacent marshlands.  Due to concerns over the biological
impacts, the intake structure was moved to an offshore location.

Seabrook has a small cooling tower onsite that provides emergency backup
cooling capacity in the event that the service water system (which also
withdraws from the ocean) is unavailable.

Attachments

Attachment A		List of Attendees

Attachment B		Aerial Photo

Attachment C		Slideshow presentation #1, April 17, 2008

Attachment D	Slideshow presentation #2, April 17, 2008

Attachment E		EPA Region I Supplemental Information Request

Attachment F	Seabrook Nuclear Power Station Proposal for Information
Collection (PIC)

Attachment G	Seabrook Station 2006 Environmental Monitoring in the
Hampton-Seabrook Area 

Attachment H	Saila, S. et. al. “Equivalent adult estimates for losses
of fish eggs, larvae, and juveniles at Seabrook Station with use of
fuzzy logic to represent parametric uncertainty.”

Attachment I	Site Visit Photos

Attachment A--List of Attendees

Paul Shriner, EPA

Jan Matuszko, EPA

Kelly Meadows, Tetra Tech

Al Legendre, FPL

Ron Hix, FPL

Paul Geoghegan, Normandeau Associates

Attachment B—Aerial Photo

Please see DCN 10-6514G accompanying this document.

Attachment C--Slideshow presentation #1, April 17, 2008

Please see DCN 10-6514A accompanying this document.

Attachment D--Slideshow presentation #2, April 17, 2008

Please see DCN 10-6514B accompanying this document.

Attachment E--EPA Region I Supplemental Information Request

Please see DCN 10-6514C accompanying this document.

Attachment F--Seabrook Nuclear Power Station Proposal for Information
Collection (PIC)

Please see DCN 10-6514D accompanying this document.

Attachment G--Seabrook Station 2006 Environmental Monitoring in the
Hampton-Seabrook Area 

Please see DCN 10-6514E accompanying this document.

Attachment H--Saila, S. et. al. “Equivalent adult estimates for losses
of fish eggs, larvae, and juveniles at Seabrook Station with use of
fuzzy logic to represent parametric uncertainty.”

Please see DCN 10-6514F accompanying this document.

Attachment I--Site Visit Photos

Please see DCNs 10-6514H-K accompanying this document.

 The original site design was for two generating units.  However, due to
extensive delays in permitting the facility, the original owner (Public
Service of New Hampshire) declared bankruptcy and did not pursue
completion of the second unit.  Facility representatives stated that
there are no plans to consider adding a second unit at this time, but
that the intake structure and other critical components were designed to
accommodate a potential second unit.

 The velocity caps are cleaned by divers twice per year; with the low
intake velocity, most cleaning is done while the facility is operating. 
To reduce biofouling, the metal components of the velocity cap are clad
with copper-nickel alloys.  The cement portions of the cap (e.g., the
intake tunnel) are cleaned with a rake.  During outages, a more
intensive cleaning is conducted, including silt removal from the intake
tunnel and camera inspections of the intake and discharge tunnels.

 The original design for the bar screens had bars with 16 inch spacing. 
However, due to the entrainment of a number of harbor seals, the
facility added additional bars in 1998 to exclude these organisms.  The
bars are still wide enough to allow seaweed and other debris to pass
into the intake tunnels and not clog the velocity cap.

 This forebay is demucked during each outage.

 During significant storms, the screens may be rotated continuously to
handle the debris load.

 The monitoring program at Seabrook costs over $1.2 million per year.

 Given recent public opposition to the rusting steel dome that was
originally constructed for Unit 2 and its visibility from the beach,
facility representatives assume that natural draft towers will not be
feasible from the perspective of local permitting.

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