Site Visit Report

	Danskammer Generating Station

	994 River Road

	Newburgh, NY 12250

April 16, 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.  Danskammer Generating
Station (Danskammer) was selected for a site visit due to its use of
fine mesh traveling screens and its large intake flow.

Facility Description

Danskammer is located on the western bank of the Hudson River at
approximately river mile 62 on the same site as the Roseton Generating
Station; both facilities are owned by Dynegy.  Approximately 250
employees work at the two sites.

The facility’s NPDES permit (NY0006262) was renewed in 2006 and
included requirements for intake technologies and flow reductions.

Electricity Generation and Transmission

Danskammer has 4 generating units.  Units 1 and 2 are each 55 MW
oil-fired peaking units that were built in 1951 and 1954 and typically
only operate in the summer and winter.  Units 3 and 4 are coal-fired
baseload units (135 and 235 MW, respectively) that were built in 1959
and 1967.  The capacity utilization for Units 1 and 2 varies depending
on the severity of weather; Units 3 and 4 operate at higher utilization
levels.  In 2006, the facility-wide capacity utilization rate was 48%.

The facility schedules its outages around the peak entrainment seasons. 
There are two short (1-2 week) outages per year, with one major outage
(4-6 weeks or more) every 4-5 years.

Cooling Water Intake Structure

Danskammer withdraws cooling water via a 450 foot long and 34 foot wide
intake canal.  The canal is relatively shallow -- as little as 8-10 feet
deep at low tide.  Intake bays for each unit are at the terminus of the
canal.

Units 1, 2 and 4 use standard 3/8” mesh traveling screens.  Unit 3 has
fine mesh traveling screens with a mesh size of 1/8” (3.2 mm) that
were installed in 1984.  When a unit is in operation, the traveling
screens are rotated continuously.  Units 1 and 2 share a common return
trough, and Units 3 and 4 share a second return trough.  Facility
representatives were unsure of the design intake velocity, but estimated
that it was approximately 0.5 feet per second; they also noted that the
intake velocity is dependent upon the number of circulating pumps in
operation.

The facility uses a once-through cooling water system with a design
intake flow of 457 million gallons per day.  As part of the 2006 permit
conditions, variable frequency drives (VFDs) were installed on Unit 4
(the largest unit) to enable reductions in intake flow when possible. 
Additionally, the permit required the continued use of a sonic deterrent
at the mouth of the intake canal, which targets outmigrating
young-of-the-year herring.

No biocides or other biofouling measures are in use at the facility.

Impingement and Entrainment Information

Danskammer conducted a number of studies in the 1980s on various topics,
including intake technologies, behavioral technologies, flow reduction
alternatives, and entrainment survival.  Since 1993, the facility has
also participated in jointly funded studies with other utilities along
the Hudson River for comprehensive monitoring.  Impingement data has
also been collected at Danskammer and Roseton since 1972.  The past 2
years of impingement and entrainment monitoring have indicated that the
species of concern may be changing from previous assessments.

Monitoring has indicated a distinct diel pattern in the abundance of
organisms in the river; nighttime impingement rates are definitively
higher, while entrainment rates also show a modest increase.

Facility representatives also noted the total population of organisms
appears to be lower than 4-5 years ago and that the species composition
has also changed.  In general, Danskammer has a higher rate of
impingement and entrainment than Roseton.  The facility has not seen an
increase in vegetative debris over that period, but facility
representatives did note that the presence of zebra mussels upstream has
led to reduced turbidity, which may eventually result in increased
vegetative growth.

The facility has NPDES permit conditions that require mandatory outages
during key entrainment periods for river herring, alewife, and eels. 
These conditions apply to individual units and include reductions in the
number of circulating pumps used while in operation.  The permit also
has tiered requirements, which increase the required reductions in
impingement and entrainment over time.

Cooling Tower Feasibility

As part of the facility’s NPDES permit renewal process, closed cycle
cooling was evaluated.  It was determined (with NYDEC concurrence) that
there was not sufficient space for cooling towers (with plume abatement)
on Danskammer’s property.  Facility representatives noted that a CSX
rail line bisects the property and steep slopes in other areas limit the
available space onsite.  NYDEC and Dynegy agreed that a patchwork of
cooling tower cells located in multiple locations was not a viable
solution, but noted that Roseton may have more flexibility for siting
cooling towers, as its property has a more open layout.

Additional Information

Facility representative stated that a barrier net installed at the mouth
of the intake canal was considered as one technology alternative.

Danskammer’s design is similar to that of the Lovett Generating
Station, located approximately 20 miles downstream.  Facility
representatives noted that the species composition at the two sites is
very different due to the salinity levels at each facility; Lovett
consequently has a longer peak entrainment season.  

Roseton is a dual fired facility (oil or natural gas) but has recently
been downgraded from baseload generating status due to market factors;
its capacity utilization is less than 10%.  Roseton’s intake structure
employs standard mesh (3/8”) traveling screens.  The traveling screens
also withdraw from a much deeper area of the river (27 feet) than at
Danskammer.

Facility representatives stated that the fine mesh screens have not
required any significant maintenance or upkeep, noting that the
continuous screen rotation likely resolves most clogging issues.  They
added that the fine mesh screen may also provide some operational
advantages, as less debris is carried over into the condenser.  Newer
screen panels are constructed of a carbon composite material, also
reducing maintenance requirements.

Facility representatives stated that Danskammer did not have a formal
plan for complying with the now-suspended Phase II rule.  At the time,
the facility was already conducting studies as part of its permit
renewal process, but noted that flow reductions and scheduled outages
were the most attractive options for reducing entrainment.  Facility
representatives stated that they were likely to use the standard
calculation baseline configuration.

Attachments

Attachment A		List of Attendees

Attachment B		Aerial Photo

Attachment C	Roseton and Danskammer Point Generating Station impingement
monitoring report 2006 (excerpt)

Attachment D	Danskammer Impingement Monitoring Program: 2008 First
Quarter Summary Report

Attachment E		Sample environmental data for Danskammer Unit 3

Attachment F		Normandeau species cutoff list for 2008

Attachment G	Danskammer Point fine mesh screen evaluation: 1986 study
(excerpt)

Attachment H	Danskammer Point fine mesh screen evaluation: 1988 study
(excerpt)

Attachment I	Estimates of impingement mortality for selected fish
species at the Danskammer Point Generating Station 1975-1980

Attachment J		A biological evaluation of modified vertical traveling
screens

Attachment K		Engineering Diagrams

Attachment L		Site Visit Photos

Attachment A--List of Attendees

Paul Shriner, EPA

Jan Matuszko, EPA

Kelly Meadows, Tetra Tech

John Carnright, Dynegy

Eric Shaw, Dynegy

Attachment B--Danskammer Aerial Photo

Please see DCN 10-6505J accompanying this document.

Attachment C--Roseton and Danskammer Point Generating Station
Impingement Monitoring Report 2006 Annual Progress Report (excerpt)

Please see DCN 10-6505A accompanying this document.

Attachment D--Danskammer Impingement Monitoring Program: 2008 First
Quarter Summary Report

Please see DCN 10-6505B accompanying this document.

Attachment E--Sample environmental data for Danskammer Unit 3

Please see DCN 10-6505C accompanying this document.

Attachment F--Normandeau species cutoff list for 2008

Please see DCN 10-6505D accompanying this document.

Attachment G--Danskammer Point fine mesh screen evaluation: 1986 study

Please see DCN 10-6505E accompanying this document.

Attachment H--Danskammer Point fine mesh screen evaluation: 1988 study

Please see DCN 10-6505F accompanying this document.

Attachment I--Estimates of impingement mortality for selected fish
species at the Danskammer Point Generating Station 1975-1980

Please see DCN 10-6505G accompanying this document.

Attachment J--A biological evaluation of modified vertical traveling
screens

Please see DCN 10-6505H accompanying this document.

Attachment K--Engineering Diagrams

Please see DCN 10-6505I accompanying this document.

Attachment L--Site Visit Photos

Please see DCNs 10-6505K-N accompanying this document.

 Danskammer’s location is at the edge of the tidally influenced Hudson
River; the water is slightly brackish and there are small tidal
variations (approximately 3 feet).

 Danskammer and Roseton Generating Station operate independently, share
no infrastructure, and are separate legal entities (including a distinct
allocation of land on the site).  Roseton, along with Indian Point and
Bowline, were part of the 1981 Hudson River settlement, an agreement
with the state and environmental groups on fish protection issues in the
Hudson River.  (Danskammer is not part of the settlement agreement.) 
Roseton’s permit (NY0008231) expired in 1992 and was administratively
extended; the permit is currently in the process of being renewed.

 Units 3 and 4 were originally designed as dual fuel units (coal and
oil) but were reconfigured in 1987 to use only coal.  Coal usually
arrives by boat from Venezuela, but rail is also a delivery option.  A
supply of approximately 30-40 days of fuel is stored onsite.  Over 85%
of the ash is sent offsite for beneficial uses.

 Side-by-side studies of impingement survival were conducted in the mid
1980s.  However, no comparative studies for entrainment have been
conducted.

 The facility typically documents any flow reductions using a measure of
organism density (organisms per unit flow) and reports this information
to NYDEC.  At this time, facility representatives are unsure of the flow
reduction due to the VFDs, as they have not calculated the frequency at
which the VFDs operate.  

 Studies in Lake Ontario suggest that sonic deterrents can be effective
with herring.

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