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APPENDIX G

BTA REPORT


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Lafarge North America, Inc.

Ravena Plant Modernization Project

Cooling Water Intake System Technology and Operational Review

Prepared for:

Lafarge North America

1916 Route 9W

Ravena, NY 12143

Prepared by:

Henningson, Durham & Richardson

Architecture and Engineering, P.C.

One Blue Hill Plaza, 12th Floor

P.O. Box 1509

Pearl River, New York 10965

August 2, 2010


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TABLE OF CONTENTS

1.0 INTRODUCTION ............................................................................................................ 11.1 Regulatory Background.................................................................................................... 11.2 Objectives and Document Organization .......................................................................... 2

2.0 RAVENA FACILITY ....................................................................................................... 32.1 Existing Facility Description ............................................................................................ 32.2 Existing Cooling Water Intake Structure ......................................................................... 32.3 RPM Cooling Water Requirements.................................................................................. 42.4 Source Water Body and Entrainment and Impingement Studies ..................................... 42.5 Estimated Entrainment and Impingement ........................................................................ 5

2.5.1 Entrainment Losses ................................................................................................... 52.5.2 Impingement Losses ................................................................................................. 6

3.0 SITE-SPECIFIC ASSESSMENT OF BEST TECHNOLOGY AVAILABLE ........... 63.1 Intake Technologies ......................................................................................................... 73.2 Technologies and Measures Already in Use at the Ravena Facility ................................ 8

3.2.1 Offshore Intake and Traveling Screen ...................................................................... 83.2.2 3.2.2 Flow Reduction ................................................................................................ 9

3.3 Alternative Technologies and Operational Measures for the Ravena Facility................. 93.3.1 Exclusion Systems .................................................................................................... 9

3.3.1.1 Aquatic Filter Barrier (AFB) ............................................................................. 93.3.1.2 Wedge-Wire Screens ....................................................................................... 14

3.3.2 Separate and Remove Fish Handling Systems........................................................ 193.3.2.1 Ristroph-Modified Traveling Screens with Fish Return System ..................... 203.3.2.2 Fine-Mesh Traveling Screens with Fish Return System ................................. 25

3.3.3 Flow Management .................................................................................................. 283.3.3.1 Variable Speed Pumps ..................................................................................... 283.3.3.2 Closed Cycle Cooling ...................................................................................... 303.3.3.3 Alternative Cooling and Process Water Supply .............................................. 35

3.4 Site-specific Design, Mitigative Benefit and Cost of Practicable Alternatives ............. 37


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3.4.1 Wedge-wire screen.................................................................................................. 383.4.1.1 Engineering ...................................................................................................... 383.4.1.2 Adverse Impacts .............................................................................................. 413.4.1.3 Mitigative Benefit ............................................................................................ 413.4.1.4 Costs ................................................................................................................ 45

4.0 SUMMARY OF FINDINGS .......................................................................................... 465.0 TECHNOLOGY RECOMMENDATION .................................................................... 496.0 LITERATURE CITED .................................................................................................. 497.0 TABLES ........................................................................................................................... 598.0 FIGURES ......................................................................................................................... 71

LIST OF TABLES

Table 1. Lafarge Ravena Cement Facility Cooling Water Pump Specifications ...................... 61Table 2 Estimated Costs for Aquatic Filter Barrier at the Lafarge Hudson River Cooling

Water Intake Structure ................................................................................................ 62Table 3. Estimated Costs for Ristroph-Screen and Fish Return System at the Lafarge Hudson

River Cooling Water Intake Structure ........................................................................ 63Table 4. Lafarge facility Wedge-wire Screen and Hydroburst Design Specifications (Adapted

from Johnson Screens, June 7, 21010 memo)............................................................. 64Table 5. Lafarge Facility Wedge-wire Screen Estimate of Number of Fish Excluded and

Entrained Annually Based on average of results from 2004-2008 Long River Dataand a cooling water flow of 2.0 MGD ...................................................................... 65

Table 6. Lafarge Facility Wedge-wire Screen Biological Efficacy Estimates (2 MGD) ......... 66Table 7. Estimated Costs for Wedge-wire Screens with Hydroburst System at the Lafarge

Hudson River Cooling Water Intake Structure ........................................................... 67

Table 8. Summary of Mitigative Benefit and Practicability of Technologies Evaluated for theLafarge Hudson River Cooling Water Intake ............................................................. 69


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LIST OF FIGURES

Figure 1. LaFarge Ravena Facility Cooling Water Intake Structure Location .......................... 73

Figure 2. LaFarge Ravena Facility Cooling Water Intake Structure Plan Drawing................... 74

Figure 3. Generic Cylindrical Wedge-wire Screen (images provided by Johnson Screens) .... 75

Figure 4. Example of Airburst System Designed by Johnson Screens ...................................... 76

Figure 5. Conceptual Layout (Section View) of Lafarge Screen Assembly in Hudson River ... 77

Figure 6. Conceptual Layout (Plan View) of Lafarge Screen Assembly in Hudson River ....... 78

Figure 7. Model of Half Screen End View .............................................................................. 79

Figure 8. Model of Half Screen Top View .............................................................................. 80

Figure 9. Comparison of exclusion predictions for Turnpenny and Non-Turnpenny exclusionequations ..................................................................................................................... 81

APPENDICES

APPENDIX A Site PhotosAPPENDIX B - Source Water Body InformationAPPENDIX C Hudson River Utilities Longitudina River Survey (LRS)APPENDIX D Lafarge Closed Cycle Cooling Evaluation


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1.0 INTRODUCTION

Henningson, Durham & Richardson Architecture and Engineering, P.C., (HDR) was retained by

Lafarge North America (Lafarge) to develop a Cooling Water Intake System (CWIS) Technology

and Operational Review for the Ravena Plant cooling water intake system as required by the

New York State Department of Environmental Conservation (NYSDEC) for the DEIS for the

proposed Ravena Plant Modernization Project (RPM). This report provides the NYSDEC

requested review.

1.1 Regulatory Background

For regulatory purposes the RPM is viewed as a new water withdrawal. As explained in Chapter

12 of the DEIS there will be no discharge of cooling water from the RPM and as a result, the

intake is not subject to Section 316(b) of the Clean Water Act (CWA) (33 U.S.C. 1326(b)) and

6 NYCRR 704.5 which require cooling water intake structures to reflect the Best Technology

Available for minimizing adverse environmental impact. However, the RPM is subject to review

under the State Environmental Quality Review Act (SEQRA). Under SEQRA the plants water

withdrawal will be evaluated as to whether it is done in a way that minimizes impacts. This

evaluation will be guided by the Hudson River Estuary Action Plan which states that all new

withdrawals must minimize impacts. Thus, the overall objective is the same as under a BTA

determination, i.e., to minimize flow and install applicable technologies that will minimize

withdrawal of organisms.

It should be recognized that the existing Ravena facility is currently being reviewed under a

Department Initiated Modification (DIM) and is subject to Section316(b) and 6 NYCRR 704.5

because it has thermal discharge. As a result of compliance with the BTA requirements, theexisting facility will have required intake modifications in place prior to the RPM being

completed. The combination of the intake modifications that will already be in place and the

further flow reductions will be the basis for the RPM minimizing impacts due to water

withdrawal.


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NYSDEC has requested that Lafarge evaluate the proposed RPM with regard to minimization of

impacts through a review of the following technologies and operational measures:

Closed cycle cooling system with dry tower, wet tower, or hybrid tower technology;

Wedge-wire intake screens (both 1.0 mm and 2.0 mm slot width);

Aquatic filter barrier nets;

Ristroph traveling screens;

Fine mesh traveling screens;

Variable speed drive pumps; and

Alternative cooling and process water supply (feasible alternatives to eliminate the use ofHudson River water completely).

1.2 Objectives and Document Organization

The objective of this document is to provide a technology and operational review for the Ravena

facility cooling water intake system as required by the NYSDEC for the DEIS for the proposed

RPM. This document describes the engineering and operational parameters of the new facility,the Hudson River and fish community potentially subject to impingement and entrainment at the

facility, as well as the technologies and operational measures that could be capable of being

installed and implemented at the Ravena facility that would reduce impingement mortality and

entrainment. Each technology is evaluated in terms of engineering and operational feasibility,

potential for reducing entrainment and impingement (i.e., mitigative benefit), and cost among

other factors. Technologies that prove to be effective in each of these areas are further evaluated

in terms of site-specific design, operation, mitigative benefit, cost, construction time

requirements and potential adverse impacts that may result from their installation and operation.

The technologies are then compared according to their performance in each of these categories

and a recommendation for BTA is made.


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2.0 RAVENA FACILITY

2.1 Existing Facility Description

The current Lafarge facility at Ravena, New York is a manufacturing facility dedicated to the

production of Portland cement, the most common type of cement in general use and a basic

ingredient of concrete, mortar and grout. The facility is built on a 3,800 acre parcel. Of this,

800 acres is used for manufacturing while the remaining 3,000 acres is dedicated to quarry use.

The Ravena facility was originally constructed by the Atlantic Cement Company in 1962.

Lafarge proposes to modernize and expand its existing cement manufacturing facility in the

Town of Coeymans in Albany County, New York by constructing a state-of-the-art, energy

efficient, and economically and environmentally sustainable cement manufacturing plant. The

proposed modernization would replace the existing wet cement-making process at the facility

with a more energy efficient dry cement-making process.

2.2 Existing Cooling Water Intake Structure

For cooling and slurry makeup during cement production, the Ravena Plant relies on the reuse of

treated water from an on-site settling pond treatment system, water pumped from the quarry, and,

as a backup, water from the Hudson River. Water for cooling of equipment is recirculated within

the process to minimize use of water resources and to conserve energy.

Cooling water is currently withdrawn from the Hudson River at River Mile 134 via a 30-inch

diameter pipe. The withdrawal point is located in the main river channel approximately 80 feet

offshore1 (Figure 1; Appendix A, Photo 1). The pipe rises from the bottom where it forms a tee

approximately three feet from the surface at Mean Low Water (MLW) (Figure 2). The tee has anopening on each side covered by inch screen. Water is pumped from the Hudson using two

Layne, Northern Co. pumps with a rated capacity of 3,000 gallons per minute (gpm) per pump

1 Prior reports of the intake location indicate it to be approximately 150-ft off shore based on the engineeringdrawing provided in Figure 2; a survey conducted in July 2010 indicates that the as-built location is approximately80-ft from shore.


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(Appendix A, Photo 2). During typical operation, each of the pumps average approximately

830 gpm for an average combined flow of 1,660 gpm. Once the water has entered the landside

pumphouse, it is diverted to a US Filter traveling water screen fitted with 3/8-inch mesh

(Appendix A, Photo 3). The screens are typically rotated once every 24 hours. During periods

of high debris loading, rotation may take place more frequently. Fish and debris on the traveling

screen are removed by a pressure spray wash and exit through a collection tray (Appendix A,

Photo 4). A pipe from the collection tray conveys the spray wash and any debris and organisms

to a landside debris area (Appendix A, Photo 5). Organisms and debris small enough to pass

through the screen mesh, are conveyed to the clarifier (settling tank), where sand, silt, and other

gross impurities are removed.

2.3 RPM Cooling Water Requirements

The proposed project would require the withdrawal of up to 2.0 million gallons per day (MGD)

of water from the Hudson River.

2.4 Source Water Body and Entrainment and Impingement Studies

The source waterbody for the Ravena CWIS is the Hudson River, near the confluence with

Coeymans Creek. Water is withdrawn from the west shore of the Hudson River approximately

80 feet from the shore (Figure 1). Detailed descriptions of the Hudson River morphology and

land use, water quality, biological characteristics, life histories of selected species are presented

in Appendix B.

During the operation of the current Lafarge facility, no entrainment or impingement studies have

been required as part of the facilitys discharge permit. However, as is discussed later in this

report, data are available from local biological surveys that can be used to estimate entrainment

and impingement at the facility.


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2.5 Estimated Entrainment and Impingement

2.5.1 Entrainment Losses

The methodology utilized to calculate the entrainment losses at the current and modernized plant

is provided below. First, species, life-stage, and month-specific entrainment densities (D) were

calculated from the Hudson River Longitudinal Survey Program for each month from 2004

through 2008, representing the most recent five years of available data (refer to Appendix C for a

summary of the program methods):

where:

D = density (#/100m3) during weekm

C = number of individuals collected during weekm

m = week

q = sample volume (100 m3)

nm = the number of samples during weekm.

Entrainment densities were then used to estimate the total number of organisms entrained (E)

during each week and year under assuming 2.0 MGD for the modernized facility:

where:

E = total entrained during April through August

Q = facility cooling water flow (100 m3) for weekm.


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Under the modernized plant, assuming 2.0 MGD is withdrawn year-round, estimated entrainment

would be 866,110 organisms.

2.5.2 Impingement Losses

Given that the T-intake pipe is covered with -inch screen over each end, impingement, if it

occurs, would take place at this location. The likelihood of impingement occurring, however,

seems remote. Assuming a 75% open screen area and 2.0 MGD, calculated velocities at the

screen face are expected to be less than 0.2 feet per second (fps). The Environmental Protection

Agency has maintained that reduction of through-screen velocity to 0.5 fps would represent Best

Technology Available (BTA) for impingement, i.e., there would be no need to take additionalmeasures to reduce impingement losses because fish would be able to avoid impingement under

this condition (USEPA 2004). Because no site-specific data are available, and because

impingement is expected to be low due to the low through-screen velocities, impingement is not

estimated for the modernized facility and instead is expected to be very low.

3.0 SITE-SPECIFIC ASSESSMENT OF BEST TECHNOLOGY AVAILABLE

A site-specific assessment of BTA to minimize losses of organisms at the RPM facility is

presented herein. The analysis discusses the effectiveness, feasibility, and practicability of a

suite of potential intake technologies and operational measures considered for implementation at

RPM facility to reduce impingement mortality and entrainment. Each technology/measure is

described in detail, with examples, where available, of applications at power stations and other

facilities. The alternatives covered in this section include additional technologies and measures

that could be added to or replace the suite of existing features. Each alternative is evaluated with

respect to the existing aquatic community, water depth, available space within the facility,

bathymetry, recreational use of the area surrounding the facility and existing facility

infrastructure (e.g., intake location, technologies currently in place).


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3.1 Intake Technologies

Intake technologies that will be reviewed for the RPM may be separated into three groups based

on their method of reducing environmental impacts): 1) those that prevent or lower the potentialfor organism exposure to the cooling water system (exclusionary systems), 2) those that separate

and remove entrapped organisms at some point within the system, and 3) technologies that

reduce the amount of Hudson River water required by the facility (e.g. flow management or

retrofit of once-through cooling systems to cooling towers).

Exclusionary systems include physical barriers, which physically block fish passage, and

behavioral barriers, which alter or take advantage of natural behavior patterns to attract or repel

fish. The primary advantage of the exclusionary systems is that organisms are not handled

directly. Separation and removal systems include various screen systems that actively collect

fish for their return to a safe release location, and diversion systems, which divert fish to

bypasses for return to a safe discharge location.

The third group of technologies and operating measures involves reductions in Hudson River

cooling water flow. This approach involves determining the reductions in cooling water flow that

can be implemented without exceeding thermal discharge criteria or adversely affecting the

facilitys efficiency. Reducing the Hudson River cooling water flow rate directly reduces the

number of organisms drawn into the facilitys intake.

The following alternative cooling water intake system technologies are evaluated herein:

Exclusion Systems

1. Aquatic Filter Barrier

2. Wedge-wire Screens (0.5 mm, 1.0 mm and 2.0 mm)

Separate and Remove Fish Handling Systems

3. Ristroph-Modified Traveling Screens with Fish Return System

4. Fine Mesh Ristroph-Modified Traveling Screens with Fish Return System


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Flow Management

5. Flow Management/Reduced Flow Design (Variable Speed Drives)

6. Closed Cycle Cooling

i. Wet Cooling Towers

ii. Dry Cooling Towers

iii. Wet-Dry Cooling Towers

7. Alternative Cooling and Process Water Supply

This list of technologies covers all those requested by the NYSDEC in their correspondences

with Lafarge and includes an evaluation of 0.5-mm slot size wedge-wire screens as well.

Each of the technologies listed above is reviewed in the following section to determine the

feasibility and mitigative benefit resulting from its installation or application at the cooling water

intake system for the RPM facility. Those technologies that are found to be both feasible from an

engineering perspective and which are likely to provide a measurable degree of mitigative

benefit are further evaluated with regard to site-specific design, operation, mitigative benefit,

cost, construction time requirements and adverse environmental impacts that may result from

their installation and operation.

3.2 Technologies and Measures Already in Use at the Ravena Facility

3.2.1 Offshore Intake and Traveling Screen

Cooling water is currently withdrawn from the Hudson River at River Mile 134 via a 30-inch

diameter pipe. The withdrawal point is located in the main river channel approximately 80 feet

offshore. The pipe rises from the bottom where it forms a tee approximately three feet from the

surface at MLW (Figure 2). The tee has an opening on each side covered by -inch screen.

Once the water has entered the landside pumphouse, it is diverted to a US Filter traveling water

screen fitted with 3/8-inch mesh (Appendix A, Photo 3). The screens are typically rotated once

every 24 hours. During periods of high debris loading, rotation may take place more frequently.

Fish and debris on the traveling screen are removed by a pressure spray wash and exit through a


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collection tray (Appendix A, Photo 4). A pipe from the collection tray conveys the spray wash

and any debris and organisms to a landside debris area (Appendix A, Photo 5). Organisms and

debris small enough to pass through the screen mesh, are conveyed to the clarifier (settling tank),

where sand, silt, and other gross impurities are removed.

3.2.2 3.2.2 Flow Reduction

Based on the availability of source water from alternative onsite sources, the amount of cooling

water withdrawn from the Hudson River varies. As a result during much of the year, the amount

of Hudson River water withdrawn is considerably less than the design capacity of the pumps.

3.3 Alternative Technologies and Operational Measures for the RavenaFacility

3.3.1 Exclusion Systems

3.3.1.1 Aquatic Filter Barr ier (AFB)An Aquatic Filter Barrier (AFB) represents one type of exclusion system technology that could

be employed to reduce impingement mortality and entrainment at the Lafarge facility. There are

several operational considerations that would have to be evaluated prior to deployment at the

facilitys CWIS such as required intake flows, bottom type, water depths, commercial and

pleasure boat traffic, etc.

Gunderboom Inc. (Gunderboom ) has a patented Gunderboom Marine Life Exclusion

SystemTM

(MLESTM

) that is a relatively new type of barrier system, intended to screen all life

stages of fish by using a filtering fabric with a small pore size and a low filtration velocity. The

MLESTM

is comprised of polyester fiber strands pressed into a water permeable fabric mat and

has considerable potential for reducing ichthyoplankton entrainment. The MLESTM has an air

purge system installed between the filtering fabric layers to permit automatic cleaning of silt and

debris. The system is designed to completely surround the intake structure, away from the

shoreline, and to be fully sealed against the waterbody bottom and shoreline structures, so that all

intake water passes through the fabric at a low velocity (LMS Engineers 1997).


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Previous Application and Efficacy

The first and only full plant deployment of the MLESTM

was conducted at the recently de-

commissioned Lovett Generating Station, located on the Hudson River in Stony Point, Rockland

County, New York, starting in April of 2004. Pilot testing and limited scale deployment of the

MLESTM was begun at Lovett in the mid-1990s, which yielded significant reductions in

entrainment (up to 82% from 1999 to 2001), while essentially eliminating impingement at the

Lovett intake. Annual monitoring of the effectiveness of the full-scale (2004 to 2007) MLESTM

deployment at Lovett focused on six target taxa: striped bass (Morone saxatilis), white perch (M.

americana), river herring [Alewife (Alosa pseudoharengus) and blueback herring (A.

aestivalis)], American shad (A. sapidissima), bay anchovy (Anchoa mitchilli), and Atlantic

tomcod (Microgradus tomcod). System performance was assessed by comparing the density of

entrainable organisms behind the MLESTM with coincident density in adjacent, unprotected

areas. The most recent annual monitoring data available (2007) indicates >90% effectiveness at

excluding the target taxa, with >99% for bay anchovy (ASA 2007). Operational difficulties

associated with MLESTM

deployment at Lovett included tearing, overtopping and clogging of the

filter curtain; however, these difficulties were all addressed with subsequent design

modifications throughout the testing phase.

Feasibility of an AFB at the Ravena Facility

In order to reduce entrainment at the Lafarge CWIS, the installation of an AFB around the intake

could be implemented on a seasonal basis to exclude the eggs and larvae of target species during

the critical spring spawning period (April 1 through October 30). The basic design of the AFB

would incorporate a 280 300-ft boom that would be deployed in a semi arc configuration

around the intake pipe, with boom attachment points to the north and south of the intake

structure. The AFB would be maintained in place by the attachment of several anchor lines tothe boom and concrete anchors installed on the river bottom. The boom design would be similar

to the AFB that was installed at the Lovett facility, and would be scaled to fit in the available

space at the Lafarge CWIS.


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There are several challenges associated with the installation/deployment of an AFB around the

cooling water intake structure at the Ravena Plant such as: relatively shallow water depths in the

vicinity of the intake structure, close proximity of the intake structure to the pierhead line

(approximately 50-feet), and limited area (especially to the east) to deploy anchors and mooring

lines with adequate scoping distances necessary to secure the boom in place due to the

movements of commercial traffic at Lafarges docking and off loading areas. The final

engineering design of the AFB would reflect resolution of these issues obtained during a pre-

operational evaluation of the site conditions (i.e. bathymetric survey, hydrodynamic study, and

geophysical testing around the intake structure and surrounding area).

The conceptual design would be based on the requirement to maintain the AFB in place aroundthe intake structure while optimizing the filtration capabilities of the barrier system. It is

recommended that the through-fabric flows be maintained as low as is practical to minimize

clogging and stress on the barrier system.

Based on the anticipated hydrodynamics of the Hudson River at the location of the Lafarge

intake structure, and velocities associated with the flood and ebb tides in the vicinity of the

intake, it is recommended that the AFB design incorporate a straight shoreline configuration,

oriented north/south, and enclosing the intake structure. This semi-arc shape would take

advantage of the sweeping river currents flowing past the barrier and would help to keep any

debris that is in close proximity to the barrier moving up and down the river with the current.

This design would also reduce the probability of damage to the fabric due to contact with large

floating objects. In addition, this shape would facilitate the dispersal of organisms and

sediments that are dislodged from the fabric during routine air-burst cleaning operations.

To avoid presenting a perpendicular profile of filter fabric to the primary directional forces of

the river flow (north and south) which would increase the dynamic loading forces on the

anchors, mooring lines and filter barrier fabric, the conceptual design for the AFB also

incorporates hard transition structures at the north and south ends of the barrier system. These

structures would be fabricated from steel sheetpile and would be configured in a half moon


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shape or in the shape of an arc. The hard end structures would serve as transitional structures for

the terminal end attachments of the filter barrier. These structures would support the filter fabric

as it wraps around the structure to the terminal end connections, but would still allow the filter

fabric to rise and fall with the water elevation changes associated with tidal fluctuations of the

river. These attachment points would also allow the AFB to move with the anticipated effects of

commercial and recreational boat wakes. A second function of the hard end structures would be

to protect the AFB from direct impact of river currents and from debris (and the possibility of

any late season ice) moving down and/or upriver with tidal currents.

The filter fabric portion of the AFB would run in sections, parallel to the river flow (north and

south). The barrier would be approximately 112-160-feet long by approximately 10 to 15 feetdeep (exposed fabric area) and would span the distance between the two transitional end

structures. The AFB would have a two-layer fabric design and would be constructed in sections.

These sections would be made up of panels approximately 15-feet wide, with nylon webbing

sewn vertically along the edges to form the panel and provide structural integrity to the filter

barrier. The individual panels would be sewn together at the intersecting structural vertical

nylon seams with heavy nylon webbing that would run horizontally along the top and bottom of

the filter panels for the entire length of the AFB. The AFB would be maintained at the surface

by a flotation collar, sewn to the top of the filter fabric portion of the barrier and filled with

18-inch diameter foam flotation billets running end to end for the length of the barrier.

To maintain contact with the river bottom to ensure a positive seal of the filter fabric portion of

the barrier with the bottom contour, and to prevent infiltration of unfiltered river water, the AFB

would have an impervious skirt sewn to the bottom of the filter fabric. In addition to

maintaining a positive seal with the river bottom, the skirt would serve to protect the filter

portion of the barrier system from potential abrasive elements (such as rocks) on the riverbottom during periods of low water. The filter fabric panels running between the end structures

on the east side of the deployed AFB would be maintained in place by a series of concrete

anchors fabricated with attachment points for anchor lines. The anchors would be located at

appropriate distances away from the filter panels along the east of the deployed AFB. Mooring

lines would be sized to meet the maximum loading forces and would run between the anchors


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and the attachment points on the AFB; one line would be located just below the flotation hood

and one line would be located at a corresponding point along the leading edge of the impervious

skirt.

The MLESTM

would use an airburst cleaning system such as the AirBurstTM

system that has

typically been incorporated into the Gunderboom installations on the Hudson River. Each

individual fabric panel (15-feet wide) of the AFB would have an air-hose installed between the

panels which would run vertically up between the two fabric layers. The air-burst cleaning

system would be activated on a timed interval; a burst of air would be discharged sequentially

along the length of the AFB at the base of each panel that would rise up between the fabric

layers, dislodging any accumulated sediments. River currents flowing past the AFB would carry

the dislodged sediment away from the cleaned fabric panel. The air supply system to operate the

AFB air-burst cleaning system, compressor(s) and receiver(s) (storage capacity), would be

engineered as a stand alone system.

The capital cost estimates for installing the MLESTM

at the Lafarge CWIS are detailed in Table 2.

These costs cover the installation of a 160 of boom and include engineering design, fabrication,

on-site preparation, installation of the anchoring system, installation of the MLESTM, initial

system testing, and procurement and installation of the AirBurst

TM

system. Included in the totalcapital cost estimate is the installation of two sheet pile walls that would be used as north and

south attachment points for the MLESTM

.

This cost estimate is based on a three (3) year time period of installation, removal, and repair of

the MLESTM. It is assumed that the MLESTM would have to be replaced prior to the Year 4

installation. The costs for buying a new boom prior to Year 4 are not included in the capital cost

estimate discussed above, but would be approximately $300,000 - $350,000 based on 2010

dollars.

The total estimated capital costs for installation, removal, and repair of the MLES TM over a three

(3) year period would be approximately $1,036,750. Indirect contractor cost projections are

estimated to be $1,147,619 for a three (3) year period. These estimates include costs to prepare


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permit applications, conduct a preliminary bathymetry survey, a two year verification monitoring

program, assess the condition of the intake area where the MLESTM would be installed, a twice

per week boom performance assessment program for seven months each year during

deployment, and the annual costs for installation, removal, inspection, and shipping of the

MLESTM toGunderboom for repair.

The AFB installation option for the Lafarge RPM has the following disadvantages over a wedge-

wire screen intake system:

The AFB would be significantly more expensive than the wedge-wire intake system topurchase, install, maintain, and remove annually;

The AFB would be installed in April and removed in October of each year, leaving thefacility without a technology in place that would effectively minimize environmentalimpacts of the CWIS for the period from November through March;

The AFB would require annual installation, in-water maintenance during operation, andremoval and repair of the boom fabric and associated hardware at the end of eachseason. These additional operating and maintenance (O&M) costs would not be requiredfor a wedge-wire intake system; and

Limited by the current technology available to Gunderboom (i.e., pin firing or laser

firing) the nominal pore opening on the AFB would be 0.5 mm, the same opening as theslot size openings on the proposed wedge-wire screens. Hence the AFB would notprovide additional exclusion of entrainable organism beyond that which the wedge-wirescreen system would provide.

Based on the cost effectiveness of the AFB as compared to the wedge-wire screen alternative

recommended for installation at the Lafarge RPM, the AFB alternative is deemed impracticable

and is not advanced for further consideration or evaluation.

3.3.1.2 Wedge-Wire ScreensPassive wedge-wire screens utilize "V" or wedge-shaped, cross-section wire welded to a

framing system to form a slotted screening element that can be used to exclude debris and

fish from entering a cooling water intake system (Figure 3). The screens are fabricated


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using a single continuous wire wrapped spirally around an array of internal support rods,

producing a very strong cage-like structure with high percentage of open area for water flow.

The continuous slot is plug resistant because it widens inwardly. Screens can be produced with

various slot widths, generally ranging from about 0.5 to 10 mm, and in various cylinder

diameters and lengths to accommodate flow needs. Wedge-wire screens are installed in the

source water body such that debris and fish are not collected or directly handled or transported

by the technology and are typically engineered to have low through-screen velocities (typically

below 0.5 fps). These characteristics result in potentially high survival rates for fish (e.g., 100%

for juveniles and adult) that may come into contact with the technology.

Wedge-wire screens are generally designed to function passively; that is, to be effective, ambientcrosscurrents must be present in the waterbody to carry waterborne debris and organisms away

from the screens. In order for passive wedge-wire screens to reduce entrainment and

impingement, the following conditions must exist: (1) sufficiently small screen slot size to

physically block passage of the smallest life stages to be protected (2) low through-slot

velocity relative to the ambient cross-current flow to carry limited-mobility and non-motile

organisms off of the screen. Where these conditions are present, passive wedge-wire screens

may be an effective means of reducing impingement mortality and potentially entrainment.

Current velocities in the vicinity of the Lafarge facility are expected to be high relative to the

typical through-slot velocities associated with wedge-wire and other screen installations (i.e.,

0.5 fps). Predicted average river channel velocities at Castleton on Hudson (located less than 4

river miles north of the facility) and New Baltimore (located less than 2 river miles south of the

facility) are approximately 1.1 and 1.5 fps, respectively, such that typical current velocities

should be sufficient to sweep fish and debris off the screens should they encounter them

(estimated from Tides and Currents Pro Software).

Due to the potential for debris accumulation and plugging, wedge-wire screens are often installed

with an airburst backwash or other cleaning system. The airburst system includes a compressor,

an accumulator (also known as a receiver), controls, a distributor and air piping that directs a

burst of air into each screen (Figure 4). The air burst produces a rapid backflow through the


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screen; this air-induced turbulence dislodges accumulated debris, which then drifts away from

the screen unit (USEPA 2004). Screens of smaller slot sizes and areas with low current

velocities and high microbiotic activity may require more frequent airburst backwashes, diver

cleanings, and/or potentially other mechanisms (e.g., a brush-cleaning system) for cleaning the

screens. Passive wedge-wire screens operate most effectively in rivers and estuaries where

sufficient sweeping velocities carry away debris dislodged by the cleaning systems. Wedge-wire

screens have been installed in high-debris and low sweeping velocity areas. These installations

often involve brush cleaning systems and entrainment and impingement reductions are achieved

for those organisms with sufficient swimming ability to avoid or swim off the screen surface.


Wedge-wire screens have been effectively used at many water intakes throughout the United

States and in other countries. Large-scale deployments are limited to a few electrical generation

facilities while small-scale deployments number in the hundreds and can be found at many

industrial cooling water intakes and other non-cooling water intakes (agriculture,

aquaculture, etc).

The largest wedge-wire screen installation is currently located at the Oak Creek Power Facility in

Milwaukee, Wisconsin (Enercon 2010). This facility is capable of withdrawing 2.25 MGD from

Lake Michigan via an offshore intake located approximately 1.5 miles from shore. The offshore

intake is fitted with twenty-four (24), 8-foot diameter, 9.5-mm slot size wedge-wire screens. The

system was designed to provide a through-slot velocity of less than 0.5 fps with a 16% margin

against fouling. The intake tunnel measures 9,200 feet in length and was bored through the

bedrock. Due to the distance of the intake offshore, there is no airburst or other mechanical

cleaning system associated with this installation. However, because of the low productivity

characteristics of Lake Michigan and the copper-nickel alloy used to minimize zebra mussel

colonization, this system is expected to operate with reliability. The offshore intake and wedge-

wire screens were installed in 2009, such that long-term operational feasibility has yet to be

established for this facility. Notably, the old shoreline intake remains available for use in the

event that the wedge-wire screens are clogged by ice, debris and/or fish.


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Other large-scale installations of wedge-wire screens are at the J.H. Campbell Station on Lake

Michigan and the Eddystone Station on the tidal freshwater reach of the Delaware River (EPRI

1999). These facilities use large slot-width (6.4 mm to 10 mm) wedge-wire screens that are

capable of excluding larger juvenile and adult fish, but not eggs, larvae, and early juveniles. The

single unit at the J.H. Campbell facility is capable of withdrawing 576.0 MGD. While no data

are available for prior to installation of wedge-wire screens, studies indicate impingement was

eliminated after installation of wedge-wire screens. At Eddystone, two units withdraw over

500 million gallons of cooling water each day from the Delaware River. Over a 20-month period

prior to installation of the wedge-wire screens, it was determined that over 3 million fish were

impinged at this facility. Following installation of passive wedge-wire screens on both

Eddystone intakes, impingement was essentially eliminated.

Factors that will influence the biological effectiveness and operational feasibility of fine-slot

wedge-wire screens (such as bio-fouling, debris clogging, and ice formation) have not been

studied in detail. At both Campbell and Eddystone, periodic cleaning of the wedge-wire screens

is required, but no major operational constraints have been reported to date. An automatic

airburst cleaning system is used to minimize bio-fouling at Eddystone; the Campbell wedge-wire

screen assemblies are manually cleaned using water jets. Large water withdrawals require

multiple screen assemblies. These may take up considerable space on the bottom of the source

waterbody, potentially resulting in interference with navigation or other waterbody issues. In

areas where the screens may encounter fast moving submerged debris, deflecting baffles or

screen nosecones may be fitted to minimize potential damage.

There are many examples of wedge-wire screen installations for facilities withdrawing relatively

small volumes of water (


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cantilevered off the face of the intake structure and utilize passive cleaning and pressurized air

backwashes to keep the screens free of debris. More recently, BEC has forgone the seasonal

Gunderboom deployment because of operational issues associated with filter material

degredation and tearing.

The Athens Combined Cycle Generating Facility is capable of withdrawing up to 0.18 MGD

from the Hudson River near the Town of Athens at approximately River Mile 115 (19 miles

south of the Lafarge facility). This facility withdraws cooling water from two intake pipes

extending 580 feet from the western shoreline and approximately 24 feet below MLW, landward

of the federal navigation channel. The cooling water withdrawal point is 6 feet above the river

bottom. The openings of the pipes are covered with 3.2-mm slot size wedge-wire screens tomitigate impingement and entrainment with an air burst system to facilitate cleaning of the

screens.

The Charles Point Resource Recovery Facility, formerly known as Westchester RESCO, is

located at Charles Point on the east bank of the Hudson River near the Town of Peekskill, New

York at approximately River Mile 44 (Enercon 2010). This waste to energy facility is capable of

withdrawing 55.0 MGD from the Hudson River for use in its once-through cooling water system.

The intake utilizes 2.0-mm wedge-wire screens located 800 feet offshore. The eight (8) 54-inch

diameter screens are constructed of copper nickel alloy and arranged in four pairs on T-stands

approximately 5 feet above the river bottom. This wedge-wire screen system is utilizes an

airburst system that discharges twice daily and an annual dive team inspection to keep the

screens clean and operational. Frazil ice events have been reported for this facility on a

frequency of approximately every two to three years when extreme cold temperatures and low

river water levels occurred. The airburst system has been successful in clearing the frazil ice

from the screens.

The Brooklyn Navy Yard Cogeneration Facility withdraws 50.0 to 72.0 MGD of cooling water,

depending on season, from the East River and Wallabout Bay. This facility utilizes debris screen

panels to keep large debris out of the intake and 2-mm slot wedge-wire screens to mitigate

impingement and entrainment. Because of the debris load in the source water body, divers are


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contracted during spring, summer, and fall to clean both the debris and wedge-wire screen

systems. The debris screens are easier to clean because of their flat surfaces and larger mesh size

compared to the cylindrical wedge-wire screens with their small slot size.

To date, there has been no installation of wedge-wire screens with a slot size smaller than

2.0-mm on the Hudson River. However, smaller slot sizes are expected to be feasible for smaller

withdrawal facilities provided adequate cleaning systems and fail-safe measures (implosion

diaphragms) are incorporated in the designs.

Practicability at the Ravena Facility

It is expected that installation of wedge-wire screens at the Lafarge facility is feasible from an

engineering perspective. The ultimate design, however, would have to function in the relatively

shallow water depths in this area of the river (water depth is approximately 10.0-feet at MLW at

the current offshore intake location), have a cleaning system for debris loads, and have a build

height to accommodate seasonal ice flows and potentially boat traffic.

Evaluations of passive wedge-wire screens indicate the potential for this technology to reduce or

eliminate entrainment and impingement at cooling water intakes in a variety of marine, estuarine

and freshwater environments (EPRI 1999 and 2003). Based on studies to date, it appears that

passive wedge-wire screens could be used to replace the 3/4-inch mesh grating on the offshore

intake and have the potential to reduce or eliminate impingement and reduce entrainment

depending on what screen slot size is incorporated into the design.

Because this alternative has demonstrated biological effectiveness and appears to be feasible

from an engineering perspective, it will be advanced for a more detailed site-specific evaluation.

3.3.2 Separate and Remove Fish Handling Systems

Traveling screens have been used as barriers to debris loading and aquatic organism entrainment

at power generation facilities for decades. While these systems are effective at preventing larger

fish passage through cooling water intake systems, they generally lack the features needed to

protect fish once impinged. Traveling screens have been modified to collect impinged fish and in

concert with a return system can substantially increase survival of impinged organisms.


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Conventional traveling screens can be configured in a number of ways to increase cleaning

efficiency and reduce carry-over of debris, but all such arrangements are of limited value for fish

protection unless they incorporate specific modifications to reduce stress on impinged fish and

return them to the source waterbody with high survival. Generally, traveling screens are recessed

within the conduits carrying water to the condenser pumps, thus fish can become trapped in these

conduits, in which case the screens are the only pathway for return to the waterbody. This

evaluation of traveling screen modifications brings together the findings of various published

studies with the site specific features of the Ravena facility in order to assess feasibility.

A generic feature of all traveling screens modified for fish recovery and potentially increased

survival is the need for continuous operation to minimize the duration of impingement on thescreen surface and a fish return system that will return the fish to the source waterbody in a

location where they will not be easily subject to re-impingement on the screens. These

requirements impose increased costs to construct and maintain the fish return system and for

upgrades to accommodate increased wear and increased maintenance costs over the life of the

screens compared to conventional intermittent screen operation.

For this evaluation, two alternatives were considered that involve the alteration of the existing

traveling screen system at the Ravena facility. The first of these alternatives, replacement of the

existing conventional screens with a Ristroph-modified screen system and installation of a fish

return system would potentially reduce impingement mortality while the second alternative,

installation of a fine-mesh Ristroph system and installation of a fish return system could reduce

entrainment as well as impingement mortality.

3.3.2.1 Ristroph-Mod ified Traveling Screens with Fish Return SystemCooling water withdrawn from the Hudson River enters the Ravena facility and passes through aUS Filter traveling water screen system equipped with 3/8-inch mesh. The screen system is

typically rotated once every 24 hours, although during periods of high debris loading, rotation

may occur more frequently. Fish and debris are removed from the screens by a pressure spray

wash and exit through a collection tray. A pipe from the collection tray conveys the spray wash

and any accumulated fish and debris to a landside debris area.


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Replacement of the existing traveling screens with a Ristroph-modified screen system of the

same mesh size is the first alternative traveling screen modification considered for the Ravena

facility. Ristroph-type traveling screens are designed specifically to enhance survival of

impinged fish through incorporation of fish collection buckets on the lower edge of each screen

panel and low pressures screen washes to reduce stress when washing the fish off the screens.

The buckets are designed to reduce buffeting of the fish against the screen mesh. Impinged fish

are lifted in the buckets as the screens travel vertically and at the top of the rotation cycle are

gently washed with a low-pressure spray into a fish return system, which transports them to the

source waterbody at a location away from the intake. The return location is selected to minimize

recirculation of the returned fish and reduce the chance of re-impingement. A high-pressure wash

is used to remove debris from the screen after the low-pressure washing.


Conventional traveling water screens have been altered to incorporate modifications that

improve survival of impinged fish. Such state-of-the-art modifications minimize fish mortality

associated with screen impingement and spraywash removal. Screens modified in this manner

are commonly called Ristroph-type modified screens and have been incorporated into through-

flow, dual-flow, and center-flow screens.

Ristroph-type modified screens have been shown to improve fish survival and have been

installed and evaluated at a number of power facilities. Notable examples are the modified

Ristroph screen installations at the Indian Point Generating Station on the Hudson River and the

Salem Nuclear Generating Station on the Delaware River. Both of these facilities were retrofit

with modified Ristroph screens and extensive studies were done documenting the resulting

increases in impingement survival. Improvements have recently been made to the Ristroph

screen designs that have resulted in increased fish survival. The most important advancement in

state-of-the-art Ristroph screen design was developed through extensive laboratory and fieldexperimentation. A series of studies conducted by Fletcher (1990) indicated that substantial

injury associated with these traveling screens was due to repeated buffeting of fish inside the

lifting buckets as a result of undesirable hydraulic conditions. To eliminate these conditions, a

number of alternative bucket configurations were developed to create a sheltered area in which

fish could safely reside during screen rotation. After several attempts, a bucket configuration


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animals. For purposes of cost estimating, it was assumed that an 18-inch diameter HDPE

(high-density polyethylene) pipe would be used for the fish return line and the return flow would

be pumped into the river rather than fed by gravity. The return system would require

modifications to the existing intake building and the infrastructure at the site between the facility

and the river. Because it may be necessary to extend the return outfall beyond the site boundary

to prevent recirculation of fish, access to adjacent property could be a problem. It would be

necessary to bury the return pipeline or provide other provisions to avoid freezing in winter.

Location of the fish return in the Hudson River beyond the shoreline and beyond the existing

intake would require protection to prevent damage from ice and from large debris that can be

carried with flows in the river. A submerged outfall in the river would require

major construction.

Replacement of the existing traveling screens with Ristroph-modified through flow screens

would require modification to the existing screen housing. The existing support frames,

backwash headers and nozzles, and control systems would also be replaced. Removal of the

existing traveling screens, installation and completion of mechanical and electrical work of the

new Ristroph-type screens would require about four weeks to complete. Because there is only

one traveling screen system, operations at the Ravena facility would be impacted during

installation of the replacement screens. However, the existing debris and fish troughs could

temporarily remain in-place after the installation, allowing the facility to return to full operations

before initiating the installation of the new low-stress fish return system which would take

approximately two months to install and would be required to maximize the benefits of this

design alternative.

Operation and maintenance of the Ristroph-type screens would be similar to that of the existing

conventional screens. However, the modified screens would be rotated continuously year round.

Maintenance requirements for the circulating water pumps would not change; however, there

would be added maintenance costs for the new low-pressure spray wash pumps. Inspection and

cleaning of the fish/debris troughs would require additional labor.


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While replacement of the existing conventional traveling screens with Ristroph-type screens

would not reduce the number of fish impinged, it would potentially increase survival of some

impinged species. The potential increase in initial impingement survival at the screens would be

confounded by the fact that the fish return pipe would need to be over 250 feet long in order to

release the fish at a location in the river where the potential for re-impingement would be low.

Transport of fish in a return pipe this long may cause additional mortality of the impinged fish.

The overall increase in survival that would occur as a result of installation of a Ristroph-

modified screen system is unknown but assuming that initial survival could be increased to about

50% and that latent mortality was 15%, including the effect of the return pipe, then the

impingement survival would be about 43%. However, this increase in survival would only apply

to fish that were small enough to pass through the 3/4-inch mesh screen on the current offshoreintake and large enough to be impinged on the 3/8-inch traveling screen. Obtaining 43% survival

for this very small component of fish would result in an insignificant reduction in fish losses at

the facility and is thus not worth the considerable cost of the screens and the construction

required for their installation.

As discussed in Section 3.3.1.2, wedge-wire screens with 9.0 mm slot size would prevent fish

that would be impinged on a 3/8-inch traveling screen from entering the intake. Fish of this size

would not only be excluded from the intake by the wedge-wire screen but would also have

sufficient swimming ability to swim away from the screen, thus avoiding impingement. Thus, in

contrast to Ristroph travelling screens, the wedge-wire screens would eliminate impingement as

opposed to fractionally reducing impingement mortality.

The installation of a Ristroph screen system at the Ravena facility would cost an estimated

$450,000 for the screen panels, low-pressure wash screen wash system and the low-stress fish

return system, when engineering, contractor overhead, site work, and contingencies are included

(Table 3). Based on the large discrepancy in the efficacy and cost effectiveness between the

Ristroph-modified coarse-screen and wedge-wire screens alternatives, the Ristroph-modified

coarse-mesh screen alternative is deemed impracticable and is not advanced for further

consideration or evaluation.


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3.3.2.2 Fine-Mesh Traveling Screens with Fish Return SystemThe second traveling screen alternative considered for the Ravena facility is replacement of the

existing coarse-mesh screens with a fine-mesh Ristroph screen system. Screens with mesh sizesranging from approximately 0.5-mm to 5-mm mesh size are considered fine mesh. In addition

to increasing initial impingement survivability, fine-mesh Ristroph-modified screens can be

effective in reducing cooling water entrainment. Initially, this technology was developed for the

purpose of debris removal and its use as a means of reducing fish entrainment was a secondary

benefit (Fletcher 1990). Larvae and small juveniles that would otherwise pass through coarser

mesh screens (entrained) are impinged on the fine-mesh screens where they are washed off the

screen mesh surface into a fish return system and returned to the source waterbody.

When the probability of surviving the impingement process is greater than the probability of

surviving passage through the cooling water system (where they are subject to elevated

temperatures, pressure changes, and shear forces), then overall facility losses can be reduced.

However, when mortality of small fish on fine-mesh screens exceeds entrainment mortality, then

their installation may actually increase total facility impacts. A low-stress fish return system

would be required to return both the early and later life stages impinged and washed off the

screens to the river. Fine-mesh traveling screens are less likely to cause injury to larger fish

(de-scaling) during the passage from fish bucket to return trough in comparison to

conventional traveling screen mesh sizes (e.g., 9 mm to 10 mm) and therefore can also reduce

impingement mortality.


The results of post-impingement survival testing and evaluations of the influence of screen mesh

size have been variable. Laboratory studies conducted on freshwater larvae have found that post-

impingement survival is species-specific with some species exhibiting higher mortality while

other species experience relatively high survival regardless of screen mesh size or through-mesh

water velocity (Taft et al. 1981a, 1981b). Fletcher (1990) reviewed several larval screen

retention studies and noted that overall mortality did not correlate significantly with mesh size,


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but was more dependent on species and age (size). He also noted a direct relationship between

debris retention and mortality in which smaller mesh retained more debris, with a resultant

higher mortality due to the larvae becoming entangled in the debris.

At the AES Somerset Generating Station, located on Lake Ontario, 1.0-mm fine-mesh traveling

screens are used to reduce impingement mortality and entrainment. These screens are modified

with fish collection buckets and other measures to reduce fish impingement mortality and are

thus termed modified-Ristroph screens. Fish are lifted above the operating floor and gently

sprayed with water into a 15-inch return line, which transports them to two 10-inch diameter

underground pipes with flows maintained at 5 fps to 7 fps. These pipes merge into a 14-inch

discharge which extends 100 feet offshore in approximately 15 feet of water. A high-velocity

wash is used to remove debris from the screen after low-velocity washing.

McLaren and Tuttle (2000) conducted survival testing at AES Somerset over a four-year period

that included all four seasons. Fish were diverted from the fish return system associated with the

fine-mesh traveling screens and held for observation for 96-hour intervals. Following

observation, a screening table was used to differentiate between fish that would likely have been

impinged on conventional 9.5 mm mesh screens from smaller individuals which would have

been entrained. In many cases survival exceeded 80%, although the results were significantly

influenced by species, size, life stage, and season.

For the most frequently impinged species (alewife, gizzard shad, rainbow smelt, spottail shiner),

the 96-hour survival rates were highly variable. Alewife had the lowest survival rates, at nearly

0% during spring, but increasing to 45% in summer of 1989 following refinements to the

screening systems. Rainbow smelt also displayed highly seasonal variation in survivorship,

ranging from 1.5% during summer to 22% in fall, and as high as 95% in spring. Gizzard shad

survival ranged from 54 to 65%; however all other species (rock bass, white perch, white bass,

and yellow perch) exhibited survival rates exceeding 70-80% throughout the study. Less

frequently impinged species, such as centrarchids, lake chub, mottled sculpin, and trout-perch

generally exhibited survival rates approaching 100%, with the exception of trout and

salmon (42%).


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For most species, the survival of juvenile and smaller adult fish on the 1-mm mesh screens was

comparable to that of larger fish that would normally be impinged on 9.5-mm standard mesh

used in conventional traveling screen systems. Thus, the authors concluded that 1-mm mesh

screens effectively protect small fish that otherwise would be entrained and suffer mortality.


Under this alternative, the existing traveling screens at the Ravena facility would be replaced

with modified Ristroph screens with panels of 0.5, 1.0 or 2.0-mm mesh size. However, through-

screen velocities would increase due to the smaller open area associated with fine-mesh

screening unless the existing screen house was expanded. Higher through-screen velocities are

generally reported to result in lower on-screen impingement survival. The question of the

feasibility of a new fine-mesh screen system at the Ravena facility is primarily an issue of the

extent of the modifications necessary to the existing screenwell to accommodate the new screens

and installation of the associated fish return system. The existing screenwell could provide a

mounting location for the new traveling screens and the water, power and controls to operate the

system. Pending a detailed engineering analysis, it is reasonable to assume that the new Ristroph-

modified fine-mesh traveling screen system could be installed in the existing screen house and

connected to a fish return system like the one described for the AES Somerset facility.

Survival of impinged fish of the size impinged on the existing coarse mesh screens would likely

increase because the smoother surfaces of the fine mesh screens would reduce the potential for

de-scaling and abrasion. Entrainment would be reduced by varying degrees depending on the

mesh size with smaller meshes excluding more of the early life stages vulnerable to entrainment.

The excluded organisms would be impinged on the screens and their survival would be

dependent on all of the factors normally influencing impingement survival including the species

and site-specific factors discussed in preceding sections.

While fine-mesh screens could potentially provide reductions in numbers of organisms entrained,

the previously entrained organisms would now be impinged on the fine-mesh screens and the

ultimate reduction in entrainment losses achieved would depend on how well the organisms

survived on-screen impingement and return to the river via the low-stress fish return system.

There are no site specific data available regarding impingement survival of the species and life


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stages currently entrained at the Ravena facility. Examination of the impingement survival

results at AES Somerset, and taking into account the length of the return pipe that would be

needed at the Ravena facility, suggests that, optimistically, survival values on the order of 50%

might be achieved. In contrast, as discussed in Section 4.1.2.1, wedge-wire screens with the same

fine-mesh slot sizes would prevent fish from entering the intake, thus providing the same

reduction in numbers entrained but with close to 100% survival. As a result, for the Ravena

facility, efficacy of the wedge-wire screens in reducing entrainment is expected to be

considerably higher than fine-mesh traveling screens. Given that installation of wedge-wire

screens is estimated to cost less, (refer to Tables 3 and 7), the fine-mesh traveling screen

alternative is judged impracticable and not considered in more detailed evaluations.

3.3.3 Flow Management

3.3.3.1 Variable Speed PumpsReductions in cooling water flow directly reduce the numbers of organisms entrained and

impinged, and also lower the approach velocity at the intake screens, further mitigating fish

impingement mortality. Multi-speed pumps, continuously-variable-speed pumps, or

variable-speed drives fitted to existing single-speed motors can allow rapid adjustment of flowsto meet flow reduction objectives. Typically, at an existing facility with single-speed circulating

water pumps, water flow is regulated through installation of variable speed drive controls for one

or more of the circulating water pumps. The configuration of the existing intake structure can

generally remain the same with installation of the variable speed drives, although in some cases

significant modifications may be required. With any retrofit to variable speed pumping,

consequences to the cooling water discharge temperatures must be considered.


Flow reduction programs have been implemented at three power plants located on the Hudson

River in accordance with the terms of a 1992 Consent Order (CHG&E 1999). At each facility

different technological or management approaches have been used to meet the specified flow

reduction targets. For example, a flow reduction program consisting of limiting cooling water


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flow to three-pump operation until: 1) loads exceeded 1,000 megawatts; 2) compliance with the

applicable thermal limitations was in jeopardy; or 3) pump/facility reliability was at risk was

implemented at the Roseton Generating Station located on the western shore of the Hudson River

in Orange County, New York.

Dual-speed circulating water pumps were installed at Unit 2 at the Indian Point Generating

Station located on the eastern shore of the Hudson River in Buchanan, Westchester County, New

York. Each pump has a rated capacity of 140,000 gpm when operated at full speed and 84,000

gpm when operated at reduced speed. Six variable speed pumps were installed at Indian Point

Unit 3. Each Unit 3 pump has the same operating parameters as the Unit 2 pumps. The pumps

are adjusted periodically to maintain the minimum withdrawal volume required for efficient

facility operation. At full flow, the intake water approach velocity at Unit 3 is approximately 1.0

fps, at reduced flow it is approx. 0.6 fps (CHG&E 1999).

At Bowline Point Generating Station, located on the western shore of Hudson River in

Haverstraw, Rockland County, New York, flow reduction at Units 1 and 2 is achieved through

operation of the minimum number of re-circulating water pumps necessary for efficient facility

operation and throttling of water flow at the condenser, with due regard to ambient water

temperature, facility operating status and the need to meet water quality standards or other permitconditions. This results in a 20% reduction in water flow. During peak ambient water

temperature periods, two circulating water pumps are operated with no condenser throttling.

Under extreme conditions, three circulating water pumps are operated at each unit.


Extensive analysis of water needs and alternative sources have shown that the RPM will be able

to operate with a maximum withdrawal rate of 2.0 MGD, i.e., 75% less than the 8.0 MGD design

capacity of the existing facility. Thus, flow management alone should result in an approximate

75% reduction in entrainment and impingement losses.


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In order to assure that the flow will be less than 2.0 MGD new pumps will need to be installed.

The effectiveness of having these pumps be variable speed could be further evaluated in light of

their potential benefits, costs, and the potential to achieve similar results from using intermittent

operations of the pumps. However, in light of the potentially high effectiveness of flow

management and wedge-wire screens (see section 3.3.1.2) in reducing entrainment and

impingement, variable speed pumps would likely contribute minimal additional mitigation.

3.3.3.2 Closed Cycle CoolingClosed cycle cooling systems (cooling towers) can be used to reduce cooling water flows.

Cooling towers may be wet or dry, or a combination of the two, and use natural circulation or

mechanically impelled air flow to cool the water. Since they use the atmosphere for cooling,

closed cycle systems only require water as makeup for evaporative losses, elimination of solids

buildup, and leaks.

Converting a once-through cooling system to closed cycle is a complex and expensive process

that has been done infrequently, and is not possible at all facilities. Factors that may make

conversion to closed cycle cooling impracticable are lack of physical space to accommodate

towers, inherent design features of the turbine or condenser that would be incompatible with

closed cycle cooling, and interferences with existing infrastructure. Cooling towers typically

degrade facility performance and can have large environmental impacts of their own including

direct impacts such as blowdown toxicity, fogging, icing, salt drift and deposition, evaporative

water loss, fan noise, wildlife impacts, land use issues, and indirect impacts such as increased

fuel use and air emissions.

Wet Cooling Towers

With wet cooling towers, the majority of the heat transfer from the water to the atmosphere occursthrough evaporation. A typical wet tower consists of a base section about 45 feet high supporting fill

material and a large array of baffles. Headers with spray nozzles are arrayed above the fill. Water

is pumped up to the headers and sprayed along the top of the fill. It then flows in thin films down

over the thousands of square feet of fill surface to a basin located beneath the tower. The collected

water is channeled into a sump where recirculation pumps are located.


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A large space that allows air to enter is provided between the bottom of the fill and the basin. Air

flows upward through the fill, making close contact with the extensive water surface. A large air

flow is required to provide adequate cooling. Air flow is increased either by the use of fans or

towers that create a chimney effect. Towers using fans are called mechanical draft towers and

those using a chimney effect are called natural draft towers. Natural draft towers are usually circular

with a large hollow hyperbolic structure (the tower) built above the fill. The chimney effect draws

air through the fill, reducing the noise and eliminating the power loads associated with the fans that

are required to increase air flow in mechanical draft towers. Mechanical draft towers are typically

constructed as rows of separate cells. The center of each cell is open, and a large fan at the top of

the cell draws air through the fill material. Mechanical draft cells are typically much lower than

natural draft towers, usually 40-60 feet in height. However, they require a larger installation area.

The evaporation caused through the heat transfer process in wet cooling towers leads to several

undesirable environmental effects including plume formation, drift, evaporative water loss, and

concentrated discharges (blowdown). Plumes are the result of the vapor added to the air in the heat

rejection process condensing into visible moisture droplets. They can cause fog, icing, and

significant visual impacts, in addition to the visual impacts of the towers themselves. Drift is the

entrainment of droplets of cooling water directly into the air. While the quantity of water contained

in these droplets is orders of magnitude smaller than the quantity of vapor which results from the

evaporation process, these droplets contain dissolved and suspended minerals in makeup water and

other substances that are absent from the vapor. Drift from mechanical draft towers is deposited

over a more concentrated area than that from taller natural draft towers and can have more

deleterious local effects.

Dry Cooling Towers

Dry towers, which work like a large automobile radiator, keep the cooling water contained in tubes

and do not expose it to the air. The warm water flows through the tubes around which air flows and

removes heat. Thus, the air is heated without having absorbed any additional moisture. Heat transfer

tends to be much less efficient per unit of surface area than that which occurs with the direct contact


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between water and air in wet towers. Therefore, dry towers are much larger than their wet tower

equivalents. Total reliance on convection requires much greater volumes of air for cooling, so more

fans are required than by mechanical draft wet towers.

Due to the higher capital costs, lower unit efficiency (a result of a higher cooling water temperature)

and higher power requirements (a result of larger fans being needed), dry towers are usually used

only where water is in such short supply that the make-up water required for a wet tower would

represent a significant environmental impact.

Wet-Dry Towers

In a few special situations, systems have been built with both wet and dry cooling elements. Wet-

dry towers combine evaporative and convective cooling to allow the higher efficiency of

evaporative cooling, while reducing some of its environmental impacts. The formation of plumes

and the associated icing and fogging events can be reduced, but usually not eliminated. Visual

impacts due to the structures, evaporation, drift, blowdown, sludge formation and noise would

remain essentially like those of the associated wet tower component.


In a closed cycle cooling system the water is circulated continuously in a mostly closed loop.

The system is not considered completely closed, though, as some water is evaporated in thecycle. Furthermore, a portion of the water must be discharged (blowdown) from the system to

remove dissolved solids that build up in the cycle as a result of water evaporation. Makeup

water therefore must replace the water lost in this system. Makeup water flows are typically

much less than once-through flows and this can result in a considerable reduction in number of

organisms entrained and/or impinged at a facility.

Lafarge intends to incorporate the use of wet mechanical draft cooling towers in its RPM to

condense the steam generated in the proposed heat waste heat power generating facility. While

the wet system would provide a reduction of more than 90% in the cooling water flow as

compared to a once-through system, wet-dry or dry towers could provide additional reductions.

Appendix D provides a detailed analysis of the water requirements, costs, and impacts on power

generation of the wet-dry and dry-tower alternatives. This information is used in the

practicability evaluation of these two alternatives presented below.


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The proposed wet mechanical draft cooling tower for the RPM facility consists of two cells.

Water will be pumped to the top of the tower where it will be distributed evenly throughout the

cooling tower fill medium, which essentially creates a large surface area for the water to be

spread out over. The water flows downward through the fill towards the cooling tower basin.

Air is also pulled across the cooling tower fill by a fan mounted at the top of each cell. The air

facilitates cooling of the water and a portion of the water is evaporated. Circulating water pumps

are located in the cooling tower basin, which pump the water back to the steam turbine

condenser and then back to the top of the cooling tower. A makeup water pump and a blowdown

pump are also required to supply water to the cycle and discharge water from the basin. The

cooling cycle is designed to operate at 5 cycles of concentration which is typical for a cooling

tower.

Water consumption of the heat rejection system can be reduced by using a wet-dry mechanical

draft cooling tower as opposed to a wet tower. A conventional wet-dry cooling tower has a tube

bundle at the top of the cooling tower to which the circulating water is pumped. The water flows

downward through the tube bundle as air is drawn across the tubes, thus removing a portion of

the heat from the circulating water without any evaporation occurring. The circulating water

then flows from the tube bundle into the wet section of the cooling tower, where the water is

distributed over the cooling tower fill and empties out into the tower basin. Because the watertemperature is reduced in the dry section of the tower, less heat needs to be rejected to the

atmosphere in the wet section of the tower and total water evaporation is therefore reduced.

Cooling tower blowdown is also reduced as a result of the lower evaporation rate and the

required quantity of makeup water is therefore also reduced. It is noted, though, that during hot

weather the amount of water conserved is minimal as most of the heat is still rejected through

evaporation in the wet section of the tower. As ambient temperatures drop, though, overall water

conservation will increase. On average, wet-dry cooling towers can reduce water consumption

by 15% to 30% on an annual average basis. At the Ravena facility, when compared to a standard

wet mechanical draft cooling tower, a wet-dry cooling tower provides a reduction in water

consumption of approximately 23% on an annual average day resulting in an overall annual

reduction in water consumption, but water conservation is expected to be minimal during very

hot summer days.


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The dry cooling option evaluated would utilize an air cooled condenser (ACC), thus no makeup

cooling water would be required. Steam exhausts from the steam turbine directly through a duct

to a steam distribution header. The steam would travel down the header and be distributed

through a series of finned tube bundles. Fans located at the bottom of the A-frame shaped heat

exchanger draw in air from the bottom and out over the finned tube bundles. By passing ambient

air over the finned tube bundles, the steam is condensed and returned to the plant feedwater

cycle. The system is therefore completely closed as no circulating water is utilized and no water

losses are attributed by the ACC during normal plant operation.

Installation of either a wet-dry or air cooled condenser for cooling of the proposed waste heat

recovery plant would be feasible. Appendix D describes how these two alternative coolingsystems would operate while providing conceptual designs including water balance diagrams and

costs associated with both the wet-dry and air cooled condenser alternatives.

While the wet-dry and air cooled condensers are both feasible, they cost considerably more than

the proposed wet tower and reduce revenue from the plant by reducing the plants efficiency.

The wet-dry tower would cost approximately $1.3 million in capital costs and cause a net

revenue reduction over the life of the project of almost $2 million. Use of an air cooled

condenser for this application increases the capital cost of the facility by approximately $3

million over that of a standard wet cooling tower system. Furthermore, use of an ACC would

result in more than a 1.5 MW reduction in net power output on an average annual basis due to

increased steam turbine backpressure. This decrease in net generation is significant, resulting in

a net revenue reduction of approximately $10 MM.

The wet-dry tower would reduce the already low water use of the wet tower by about 23% on an

annual aver

App G - BTA Report

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Transcript of App G - BTA Report