Document ID: EPA-HQ-OW-2008-0667-0003
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-11-05T05:00Z

Site Visit Report

	WPS Beaver Falls Generation, LLC.

	9644 Main Street

	Beaver Falls, NY 13305

April 1, 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.  WPS Beaver Falls
Generation (BFG) was selected for a site visit due to its use of a fine
mesh wedgewire screen and its large intake flows.

Facility Description

The BFG facility, owned and operated by Integrys Energy Services, Inc.,
is a mid-sized cogeneration plant located in Beaver Falls, NY. The
facility occupies a confined 5-acre site on the north bank of the Beaver
River and is bordered by other industrial facilities and residential
neighborhoods. BFG began operations in 1995 as a cogenerator producing
electricity to the grid and industrial process steam.  Integrys Energy
acquired the facility in May 2002.

Cooling and process water withdrawals from and wastewater discharges to
the Beaver River are currently regulated under SPDES Permit No.
NY0236101 most recently re-issued in May 2008. As discussed below, BFG
has altered its operations such that it is now considered a Phase III
facility under EPA’s 316(b) framework. Accordingly, BFG did not
initiate activities under the Phase II rule that included Comprehensive
Demonstration Study (CDS) preparation and technology evaluations. 
Beaver Falls discharges approximately 40 feet downstream from the
intake. 

Electricity Generation and Transmission

BFG operates a single combined-cycle generating unit consisting of one
combustion turbine, one heat recovery steam generator (HRSG) and one
steam turbine. The combustion turbine can be fired using either natural
gas or fuel oil (#2), although natural gas is currently used almost
exclusively due to more favorable market conditions and environmental
regulations. Fuel oil has been used for fewer than 200 hours over the
last 5 years, primarily to demonstrate compliance with air emissions
requirements.

When generating electricity for sale to the grid, BFG produces
industrial process steam for the adjacent pulp and paper mill by
capturing waste heat from the combustion turbine in the HRSG and
diverting the resulting steam to the mill, which returns all condensate
to BFG for reheating. Excess steam not diverted to the mill is used to
generate electricity with BFG’s steam turbine, which uses once-through
cooling water from the Beaver River.  Steam volumes delivered to the
mill vary based on mill operations.

BFG is contractually obligated to provide steam to the pulp mill
regardless of electricity generating activities. When the combustion
turbine is not in use, steam is generated with an auxiliary steam boiler
that does not require cooling water. 

BFG was originally designed as a baseload facility. BFG’s rated
electrical output is 95 MW, although facility representatives stated
that the maximum output peaks at approximately 90 MW depending on
climate conditions and steam diversion to the mill. Since 2002, on an
annual basis, BFG’s maximum capacity utilization rate has been
approximately 20 percent, reflecting an average generating time of 2-3
days per week.

, the facility may be required to shed load to comply with thermal
discharge limitations to the river, which restrict discharge
temperatures to 90º F, with a 5º ΔT for the receiving water mixing
zone. The copper-nickel condenser has a design rise of approximately
18-23º F. Summer river temperatures can reach as high as 80º F.

The facility has a routine 3-week plant-wide maintenance outage that
typically occurs during spring and includes cooling water system
inspection and maintenance. There is a planned outage in October 2008
for a control room upgrade.

Cooling Water Intake Structure

BFG operates one cooling water intake structure to provide non-contact
cooling water to one surface condenser for steam condensation. The
intake structure consists of 5 cylindrical wedgewire screens, a common
wet well and one circulating water intake pump operated at 100% (see
Attachment A).  A duplicate circulating pump provides backup.  The
design intake capacity of the system is 58 mgd based on the pump rating
and flow-through capacity of the screens; however, physical cooling
water system restrictions after the intake pumps and screens limits the
amount of water that can be circulated at the facility to less than 50
mgd. 

BFG has modified its system, however, by installing a pump restrictor
plate that limits the maximum intake flow to approximately 49 mgd. 
Facility representatives stated that this modification was made with the
expressed intent of reducing the design flow enough to reclassify BFG as
a Phase III facility rather than Phase II. The reduced flow capacity has
not resulted in any negative impact to facility operations.

The 5 cylindrical wedgewire screens are constructed with stainless steel
(304) panels and designed with 3-mm slot openings to exclude entrainable
objects from entering the system. Each screen is designed to maintain a
maximum through-screen velocity of 0.5 feet per second (fps) at an
intake rate of 9,800 gallons per minute (gpm), for a combined flow rate
of 39,200 gpm, or 56 mgd. As noted above, however, BFG has modified its
pump to limit flow to 49 mgd, which results in lower through-screen
velocities. Through screen velocities have not been specifically
measured since the pump modification.

The 5 wedgewire screens are installed in the river bulkhead along the
facility’s southern boundary and extend outward into the river flow.
The screens are arranged in series, one behind the other, and oriented
into the oncoming current. Each screen has a 48-inch diameter, extends
175 inches (nose to tail) and is mounted on a 36-inch stainless steel
intake pipe (see Attachment B).

River currents and volumes are normally more than sufficient to maintain
debris-free screens, with low water ambient currents averaging 2-3 fps
and providing approximately 4 feet of cover.  

To install the screens, the facility excavated an artificial channel in
the river and constructed a concrete bathtub adjacent to the bulkhead.
The concrete bathtub extends 7 feet below the natural riverbed and
approximately 12 feet below the mean river level. The artificial channel
has the effect of concentrating the river flow during low water months
and routing it past the intake screens, thus ensuring an adequate water
volume during low flow conditions.  

A protective grating is present on the upstream and outer bathtub walls
to prevent large floating debris and ice from damaging the intake
screens.  The downstream end of the bathtub is open.

Water withdrawn through the screens empties into a common wet well
approximately 13 feet deep directly below the main building. The single
circulating water pump draws water from the wet well through the
condenser and to the river discharge located downstream from the
facility. Because the wet well acts as an equalization basin, inflow is
relatively uniform across the 5 screen assemblies.

Screen faces are kept free of debris with an air burst cleaning system
that is manually triggered by facility staff. The original installation
included a timed airburst cycle but the facility determined the
automated cycles were longer and more frequent than necessary. During
“clean” water months—generally winter, spring and summer—days or
weeks may pass between airburst cycles. During high debris periods
(e.g., leaves), particularly fall months, the system may be triggered 1
or 2 times per day to remove leaves and debris. Leaf clogging is the
most routine maintenance issue relating to the CWIS.  BFG staff
indicated icing is not a problem since there is continuous water flow
over the screens and noted that they also use the airburst system to
prevent ice formation.   

Maintenance for the wedgewire screens involves removing them from the
water, checking for physical damage, and replacing damaged parts. Annual
maintenance is performed during the plant-wide maintenance shutdown. The
most common maintenance issue involves the 4-inch stainless steel mesh
hoses that inject compressed air into the screens for cleaning. These
hoses often require replacement each year after sustaining damage from
ice and large debris during the spring runoff.  Replacement of the
airlines and cables cost an estimated $3,000-$5,000.  Screens are also
visually inspected by a diver each year. Maintenance dredging of the
bathtub or upstream channel has not been necessary since the original
installation.  

Impingement and Entrainment Information

BFG has not conducted any biological evaluations that specifically
focused on impingement and entrainment impacts or wedgewire screen
performance relating to adverse environmental impacts. The most recent
biological study focuses on the thermal impacts from the facility’s
discharge. The facility has not documented any biological impacts
relating to CWIS operation. 

NYSDEC considers the cylindrical wedgewire screens to be BTA for
impingement and entrainment based on a best professional judgment (BPJ)
assessment, although no information is available that supports this
conclusion.  It was noted that the intake velocity of 0.5 fps or less
under the plant’s 9800 gpm operating intake flow would also have met
Phase 2 rule impingement requirements.  A limited number of species have
been observed in this stretch of the Beaver River. 

The facility representative stated that he believed the principal reason
3-mm wedgewire screens were selected for BFG was the concern over
organic debris being withdrawn into the wet well and circulating water
pump rather than the protection of aquatic life. 

Cooling Tower Feasibility

The facility representatives indicated that the size and configuration
of the 5-acre site would present challenges to siting a wet cooling
tower as part of a retrofit. The plant is located along the river, and
the river splits the hamlet’s population (roughly 500). They stated
that the proximity of residential areas across the street would present
aesthetic impact obstacles as well as drifting and icing issues. 
Facility representatives also expressed concern over noise associated
with cooling towers.  The facility is subject to a 57 decibel limit and
is currently running at 54 decibels.

Facility representatives also noted that if they were to design the
plant today, they would prefer to have included a cooling tower to
address 316(a) temperature issues, especially during the summer months
when river temperatures are high and water levels are low.

Other Information

BFG uses a ball cleaning system for its copper-nickel alloy condenser. 
No biocides are used at this facility. A chlorine system was installed
but never commissioned for use.

The Beaver River has a mean annual flow of 397 MGD.  The Beaver River
feeds into Lake Ontario approximately 20 to 25 miles away from BFG. 
There are multiple hydro plants above BFG.  There are two small dams
near BFG, where a trip from either dam has caused the intake water level
to drop at BFG.

Integrys Energy Group, parent company to Integrys Energy Services, also
owns three other Phase II facilities in Wisconsin, one of which is a
peaking unit.  Two units at one of these facilities have cooling towers.

The facility discharges wastewater downstream of the concrete wall
through 68 submerged diffusers.  

Attachments

Attachment A		List of Attendees

Attachment B		Aerial Photo

Attachment C		CWIS Line Drawing

Attachment D		Site Visit Photos

Attachment A--List of attendees

Paul Shriner, EPA

Jan Matuszko, EPA

Tim Havey, Tetra Tech

Edward Jordan, Integrys Energy Services

Mark Metcalf, Integrys Business Support

Attachment B—Aerial Photo

Please see DCN 10-6501A accompanying this document.

Attachment C--CWIS Line Drawing

 

Attachment D--Site Visit Photos

Photo 1. Downstream view.

 

Photo 2. Upstream view of screen area.

 

Photo 3. Air hose looking down to screen area.

 

Photo 4. Downstream view.

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 The facility also owns 5 non-contiguous acres (up the street) that it
uses for fuel storage.

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