FIRSTLIGHT POWER RESOURCES, LLC.

MOUNT TOM STATION

NPDES PERMIT NO. MA0005339

COOLING WATER INTAKE STRUCTURE

INFORMATION DOCUMENT

JANUARY 2008

Prepared by:

Kleinschmidt

Ene \Wte Resource Consltants
FIRST LIGHT POWER RESOURCES, LLC.

MOUNT TOM STATION

NPDES PERMIT NO. MA0005339

COOLING WATER INTAKE STRUCTURE INFORMATION DOCUMENT

JANUARY 2008

Prepared by:

Kleinschmidt

Ener \Wter Resource Consltants
FIRSTLIGHT POWER RESOURCES, LLC.

MOUNT TOM STATION

NPDES Permit No. MA0005339

COOLING WATER INTAKE STRUCTURE INFORMATION DOCUMENT

TABLE OF CONTENTS

INTRODUCTION ........... 

,,..... .., ..... 

.......... ....... .... ..... 1

1.0 COOLING WATER SYSTEM............... . ;................ ....... ........ ....... ............ ............ ............ 2

SOURCE W A TERBODY FLOW...................................................................................... 3

Hydraulic Zone of Influence................................................................................... 3 2.2 Anual Mean and 7QlO Flow of Connecticut River .............................................. 3

VELOCITY INFORMATION............................... ..... 

................. ....... 5

TECHNOLOGY ASSESSMENT INFORMATION.......................................................... 6

Description of MTS Cooling System...................................................................... 6

Proj ected Retirement Dates..................................................................................... 6

3 Boiler, Condenser, CWIS, and Effuent Treatment Operations.............................. 6 4.4 Mechanical Draft Cooling Towers.......................................................................... 8

Natural Draft Cooling Tower.................................. ....................... ....................... 11

Non-water Environmental Impacts of Mechanical and Natural Draft Cooling

Towers................................................................................................................... 

Use of "Grey" Water............................................................................................. 12

Flow Reduction................................................................... "................................. 13

Fish Return System Upgrade........................ ................. ....................................... 15

Traveling Screen Upgrades (Ristroph, Dual-flow) with Fish Return System ...... 17

Barrer Nets...... 

............................. .................,..... ..... .............,.... 

..... ..................... 18

Electric Fish Barrer....................................... ..................,....... ............................. 19

Cylindrical Wedge Wire Screens............... ........................... .................. .............. 20

Expanded Intake.................................................................................................... 22

CWIS Relocation.............................................................................. .................... 23

OTHER INORMA nON REQUESTED........................................ ................................ 25

REFEREN CES ................................................................................................................. 26

LIST OF APPENDICES

Appendix A Figures

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FIRSTLIGHT POWER, LLC.

MOUNT TOM STATION

NPDES Permit No. MA0005339

COOLING WATER INTAKE STRUCTURE INFORMATION DOCUMENT

INTRODUCTION

The current National Pollutant Discharge Elimination System (NPDES) permit for Mount

Tom Station (Permit No. MA0005339) expired September 18, 1997. Since Mount Tom Station

(MTS) applied for a permit reissuance in a timely manner, the permit was administratively

continued until a new one is issued. Pursuant to Section 308 of the Clean Water Act (CW A)

the United States Environmental Protection Agency s Offce for the New England Region (EPA)

requested specific information regarding the MTS in order to develop cooling water intake

structure (CWIS) limits for a new permit in a letter dated January 7 2005. This information

request was consistent with the EP A' s Phase II Rule for CWISs under CW 3l6(b). In

response to 3l6(b) requirements, MTS developed and submitted a Proposal for Information

Collection (PIC), as well as the three reports required by 40 C. R. 122.2l(r)(2) (3) and (5), to

the EP A and Massachusetts Department of Environmental Protection (MADEP) in September

2005. Revisions to the PIC and the "Cooling Water System Data, 40 CFR 122.2l(r)(5)" report

were submitted to EPA and MADEP in October 2006.

On September 11 , 2007, the EP A sent a letter to FirstLight Power Resources, LLC

(FirstLight) pursuant to 308 ofthe CW A to clarify and update certain information submission

requirements for MTS, related to the Station s application for reissuance of its NPDES permit.

The information requirements in question pertain to the MTS CWIS regulated under Section

316(b) of the CWA.

1 CW A g308(a) authories EP A to require the owner or operator of any point source to make reports and provide

informtion as may reasonably be required to.. . "carr out the objectives of. ..(the CW A), including but not limited

to: (1) developing or assisting in the development of any effuent limitation, or other limitation, prbhibition. .. or

standard of performnce under (the CW A)... ; (2) determning whether any person is in violation of any such

effuent limitation, or other limitation, prohibition or effuent standard,... or standard of performnce; (3) any

requirement established under this section; or (4) carring out section.. . 1342.. .of (the CW A). ..

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1.0 COOLING WATER SYSTEM

Information requested regarding the cooling water system at MTS was previously

provided in the final drafts of the "Cooling Water System Data Report, 40 CFR l22.2l(r)(5)"

(Kleinschmidt 2006a) or the "Proposal for Information Collection" (Kleinschmidt 2006b)

submitted to EP A in October 2006. The "Cooling Water System Data Report" provided a

description of the cooling water system (Section 1.1), its relationship to the CWIS (Section 1.1),

the number of days per month the cooling water system operated during 2000-2004 (Section

1.2), and typical seasonal changes in operation ofthe system (Section 1.2).

As indicated in Section 2.3 of the PIC (Kleinschmidt 2006b), the design intake flow for

MTS is 133.2 MGD (million gallons per day). Based on data contained in Discharge Monitoring

Reports (DMRs) for 2000-2004, the average daily cooling water flow used by MTS is

approximately 85.4 MGD (see Table 2 of PIC). Therefore, approximately 64. 1 % of design

intake flow is used by the MTS cooling water system.

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SOURCE WATERBODY FLOW

Hydraulic Zone ofInfluence

In order to determine zones of influence and velocity magnitudes for MTS intake

and discharges to the Connecticut River, a two-dimensional steady state analysis was

prepared. The National Center for Computation Hydroscience and Engineering

(NCCHE) computer program NCCHE2D was used, in conjunction with the mesh

generator, in computing the zones of influence. The NCCHE2D model is a twodimensional, depth-averaged, unsteady, turbulent flow model with non-uniform and nonequilibrium sediment transport capabilities (Figure 1).

Bathymetric survey data was collected for the breadth of the Connecticut River

both upstream and downstream of the CWIS and discharge pipe using a single beam

fathometer. The distance of surveyed information was suffciently separated from the

area of study to eliminate any influences from boundary '?onditions on the upstream, and

downstream end. The upstream boundary condition was set as a constant inflow equal to

the flow during the day of bathymetric survey, whereas the downstream boundary

condition equaled the water levels observed for this river flow. A constant withdrawal

and discharge back to the river of 5.84 m /s (cubic meters per secopd) was added at the

location of the intakes, and a short diversion wall was added to the discharge. Due to the

resolution of the model, the diversion wall was set to match the field conditions as closely

as possible while meeting the three-meter grid size. Roughess values for the channel

were set to 0.025 (Maning s), and the model was run until it was able to converge on a

solution for steady state flows.

Anual Mean and 701O Flow of Connecticut River

In Section 2.3 of the PIC, it was demonstrated that MTS uses less than one

percent of the Connecticut River anual mean flow (approximately 9 264 MGD) based

upon USGS records of flow from the Montague City, MA gauge (No. 01170500).

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As reported by EPA in the public notice (June 15 2007 to July 14 2007) fact

sheet for the draft NPDES permit for the Holyoke Water Pollution Control Facility in

Holyoke, MA, the 7QlO ofthe Connecticut River in Holyoke is 1 775 cubic feet per

second (cfs), or 1 147.2 MGD. The Holyoke Water Pollution Control Facility is located

approximately 8.4 miles downstream ofthe MTS CWIS, and there are no major inputs or

outputs between the locations of the two facilities.

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VELOCITY INFORMATION

The through-screen velocity, as well as the corresponding equations used for the

calculations, at the MTS intake screen at minimum ambient Connecticut River surface elevations

was published in Section 2.3 of the "Cooling Water Intake Structure Data 40 CFR l22.2l(r)(3)"

(Kleinschmidt 2005). In that document, the through-screen velocity at the CWIS ofMTS was

reported to be 1.7 fps. Further refinement of the calculations used to obtain that value, it was

determined that the actual velocity is 1.6 fps. The design flow (cfs) equation used to calculate

the through-screen velocity:

Velocity at Screen Screen Width (I) x Low Water Depth (I) x Open Area

where:

screen width is 10 feet;

design low water depth is 13 feet;

% open area is 50. 66% (Petrovs, 2005); anddesign flow per screen is 47 500 gpm(105. 83 cft)

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TECHNOLOGY ASSESSMENT INFORMATION

The following sections provided responses to the information requests of Attachment A

Technology Assessment Information of the September 11 , 2007 letter from EPA.

Description ofMTS Cooling System

A detailed description of the MTS cooling water system was provided in the

Cooling Water Intake Structure Data Report, 40 CFR l22.21(r)(3)" (Kleinschmidt 2005)

and the "Cooling Water System Data Report, 40 CFR 122.2l(r)(5)" (Kleinschmidt

2006a) originally submitted to EP A in September 2005 (revisions to the Cooling Water

System Data Report were submitted in October 2006). These reports included

information on the cooling water intake structure and related equipment; the discharge

pipe; a cooling process flow diagram; all pumps used in the cooling system; equipment

for adding disinfectant to cooling water; and a calculation of the through-screen velocity

at the intake structure.

All equipment related to the cooling system at MTS is original to the plant (built

in May 1960), with the exception of one screenwash pump which was replaced in kind in

2005. Beyond that, no major upgrades or repairs, other than routi e maintenance, to the

other cooling system equipment has occurred since January 2001.

4.2 Proiected Retirement Dates

As of current, there are no projected retirement dates for MTS operations and

CWIS components.

4.3 Boiler. Condenser. CWIS. and Effuent Treatment Operations

Information regarding CWIS operation and effuent treatment operations was

previously submitted to EPA in the "Cooling Water Intake Structure Data Report, 40

CFR 122.21 (r)(3)" (Kleinschmidt 2005) and the "Cooling Water System Data Report, 40

CFR 122.21(r)(5)" (Kleinschmidt 2006a).

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In regards to boiler and condenser operation at MTS, the boiler is a Riley water

tube boiler, and is equipped with an economizer, rotary air preheater, convection

superheater, boiler heating surface, waterwall heating surface, and convection and high

temperature reheaters. Most of the steam is generated in the furnace which is completely

enclosed with waterwalls. The safe working pressure of the boiler is 2 150 pounds per

square inch gauge (psig), and it is normally operated at a pressure of 2 100 psig.

Feedwater enters the boiler at the economizer inlet at a temperature of

approximately 460 o , and its temperature is raised to approximately 520 of when it exits

the economizer and enters the drum. From the drum, the water flows to the distribution

headers at the bottom of the furnace and rear cavity. As water absorbs heat from the

combustion of the pulverized coal, it rises and returns to the boiler drum. The steam and

water in the drum are both at the same temperature, approximately 640 o

From the boiler drum, the steam flows through th convection superheater where

its temperature is raised to approximately 800 of. After traveling through two additional

superheaters, the steam exits through the boiler main steam nozzle at a pressure of

approximately 1 950 psig and 1 000 of toward the main turbine. The steam traverses

through multiple stages and sections of the turbine before entering he condenser.

The condenser is a Worthington surface condenser with dual water boxes and has

a capacity of 681 ,000 pounds of steam per hour. In the condenser, the steam is

condensed to water at a pressure of 0.25- 25 pounds per square inch absolute (psia)

depending on river water temperature and the cleanliness ofthe condenser. The

condensing water is supplied by the two Worthington circulating water pumps with a

capacity of 45 000 gpm each. Once condensed, the water is pumped through the air

ejectors to the de aerator where any non-condensable gasses are removed. From the

deaerator the water flows to the boiler feed pumps where the pressure is raised to 2,400

psig for feeding to the boiler prior to entering the economizer.

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4.4 Mechanical Draft Cooling Towers

The use of mechanical draft cooling tower at MTS would effectively transform

the current once-through cooling system into a closed loop cooling system. Conversion

to closed loop cooling would reduce the intake flow from the Connecticut River about

97%, and reduce entrainment and impingement accordingly. The design intake flow of

the current once-through cooling system is 92 500 gpm.

A mechanical draft cooling tower designed to remove the thermal load of the

current MTS CWIS would require the use of eight cells. Each cell would include a fan

with a 200 horsepower (hp) motor to provide the air flow required to obtain the thermal

performance. Water would circulate through the cooling tower in a direction counter 

the air flow induced by the fans located on top of the cell. The water would collect in the

concrete cold water basin and be recirculated through the turbine condenser where it

would condense the turbine exhaust to a liquid state for pumping back to the boiler. The

currently installed condenser at MTS would have to be ev luated for the additional

cooling tower head requirements. If the current condenser is not designed for the

additional cooling tower head requirements, a new condenser would need to be installed

thereby adding to the capital, as well as the operational and maintenance, costs for

implementing this technology.

The overall "foot print" required for this cooling tower is approximately 169 feet

long by 110 feet wide. The total height, including fans, is approximately 56 feet. The

major components required to be added to MTS to implement this technology include the

following: cooling water basin, pumps and piping, valves, make-up water system, motor

starts and controls, and possible retrofit to the condenser tubes (or entire condenser).

Modifications to the current plant processes include rerouting of cooling water

piping, trenching, foundations for the cooling tower location, modification to the existing

CWIS to accommodate cooling tower make-up flow and modifications to the installed

condenser or outright replacement.

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The capital cost to install the cooling tower at MTS is estimated to be $ 58.4

milion based on EP A capital cost formulas for a plume abatement cooling tower. This

estimate does not include costs for installing a fire protection sprinkler system (if

insurance requirement), additional demineralizer requirements, or modifications to the

current condenser, ifneeded. Although it is diffcult to estimate the length of the outage

required to make the conversion from once-through cooling to the closed cycle system, if

it is assumed that a minimum outage of four weeks would be required, the cost of lost

generation could exceed $4 million. In addition to capital and lost generation costs, the

annual O&M costs for the cooling tower could approach $ 5.3 million. The added cost of

operating the cooling tower fans and pumps alone would approach $600 000 annually

based on historical plant capacity factor and a $.04/kW -hr cost of electricity. A few of

the assumptions used to establish the above costs include: using inert fiberglass

composite tower materials, wet bulb temperature of76 o , use of existing circulating

water pumps, and suffcient land area available which would allow for a installation of

the cooling tower in the vicinity of the plant.

Use of a mechanical draft cooling tower would reduce the current design intake

flow by approximately 97% (92 500 gpm vs. less than 2 500 gpm). The volume of intake

water required for this type of cooling tower would consist of only make-up due to

evaporation, blow-down and drift losses. For a 8-cell unit mechan cal draft cooling

tower, there would be a drift component of approximately 1-2 gpm. Evaporation would

contribute to the bulk of the make-up water requirements. An estimated 1 670 gpm (2.4

mgd) would be required to make-up for evaporative losses to the atmosphere. In

addition, blow-down would account for approximately 740 gpm. Blow-down is required

to remove solids from concentrated cooling water which is caused by recirculating the

cooling tower water multiple times in order to reduce river water intake volume.

Typically, water can be recirculated 3-5 times through the cooling system without

causing substantial negative effects on performance. To be conservative, it was

determined that cooling water would be recirculated three times for this application at

MTS. As water is lost due to evaporation, the solids in the cooling water increase in

concentration. This can have an adverse effect on equipment life and performance.

Therefore, a portion of water is removed for blow-down, and replaced with clean makeup water to maintain concentrations of different solids in the cooling water at a

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predetermined level. During cold weather months, the plant engineer should maintain the

design water flow rate and heat load in each cell of the cooling tower. Ifless water is

needed due to temperature changes (i. , the water is colder), one or more cells could be

turned off to maintain the design flow in the other cells. This could reduce plant

operating costs of the cooling tower.

Currently, MTS is permitted to discharge cooling water directly to the river under

the normal once-through cooling system operation at a maximum temperature of 102 o

During cooling tower use, thermal discharge limits would be minimal as the cooling

tower water is mostly re-circulated and requires water from the river to make-up for that

lost to evaporation, drift and blow-down. The only water not lost to atmospheric

conditions would be the blow-down water. Depending on chemical composition, the

blow-down water may have to be treated prior to release. If the entire blow-down

volume was discharged directly to the river, the thermal discharge ofless than 1 000 gpm

would be a decrease in comparison to the currently discharged 92 500 gpm. The

postulated 105 of blow-down temperature could be routed through a new heat exchanger

to reduce the temperature to the current 102 of permitted discharge maximum.

As described in Section 3. , the through-screen velocity at the MTS traveling

screens has been determined to be 1.6 fps under current operations: Converting to closed

loop cooling through the use of mechanical cooling towers as described above, and

utilizing the current intake structure for the source of the make-up water could result in

intake velocities of 0. 08 fps. This includes the 2 500 gpm cooling tower make-up

requirements flowing through the current traveling screen or a similarly sized screen.

The addition of the cooling tower may require either modification to the turbine

condenser or a complete replacement. Modifications may include changing the

condenser tubes to a new material due to the water chemistry ofthe cooling tower water

as it is recycled. Additionally, the current condenser may not be sized to handle the head

required to circulate the water through the cooling tower. If this is determined to be the

case at MTS, then the condenser wil need to be replaced with the closed loop cooling

option. The effciency ofthe plant wi1likely be impacted since the plant is being

retrofitted with a cooling tower and not originally designed for a cooling tower. Summer

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conditions may result in a higher backpressure to the turbine/generator. This would result

in a lower turbine output. Making up for this loss in capacity may not be practical.

Currently, the MTS site has suffcient space along the northern sector of the plant

to accommodate installation of the closed loop cooling system. However this area is

under a consent order by the MADEP to be clear-cut and capped due to a historical plant

ash handling process. If allowed under the capping agreement, a cooling tower could

potentially be constructed on this parcel of land. However, it is less likely that a cold

water basin could be installed on the capped site.

Natural Draft Cooling Tower

Natural draft cooling towers are usually considered for power plants with water

needs more than twice (greater than 200 000 gpm) the volume ofMTS' s design flow

(92 500 gpm). The natural draft cooling towers framework includes very large concrete

structures, upwards of 500 feet high and 400 feet wide at the base. Normally, natural

draft cooling towers are incorporated into the original plant design and not added in as

retrofits. As a retrofit, a natural draft cooling towers would result in a substantial drop in

overall plant effciency and a new condenser would be required along with the cooling

tower. A natural draft cooling tower would increase the anual O&M costs several times

over the mechanical draft cooling tower costs. There are several elements that make it

disadvantageous for use at this site. The natural draft cooling towers is more than twice

as long and almost eight times the height of the mechanical draft tower. The much larger

size would require significant changes to the current site layout that would result in

additional impacts to endangered species habitat (state endangered dragonflies). The

added height would also increase visual impacts. And finally, costs of natural draft

towers are higher when compared to mechanical draft cooling towers.

Non-water Environmental Impacts of Mechanical and Natural Draft Cooling

Towers

Several negative factors to either the mechanical or natural draft cooling tower

options include space, visual and noise pollution, environmental hazards, cost and overall

plant effciency. The overall height of the cooling tower would make the tower visible

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from the river as well as any housing in the area, thereby negatively influencing

aesthetics of the local area. Additionally, the noise generated by the fans constantly

operating during the summer months would increase noise pollution in the area as well.

The plume generated during cooling tower operation can create hazards in the

local environment. Under certain conditions, the water vapor contained within the stream

of saturated exhaust air exiting the cooling tower condenses upon contact with cooler

ambient air and may produce fogging or icing hazards to its surroundings. The increased

fogging and icing hazards due to the vapor plumes may produce dangerous conditions for

local roads, major highways (i. e. 1-91), as well as air and river navigation.

The height of the tower and generated plume can also obstruct migratory paths of

birds, and can often unintentionally cause mortality. There is a nesting pair of bald

eagles immediately adjacent to the MTS property. In addition, there are 28 species of

birds listed as endangered, threatened, or special concern in the state of Massachusetts

three of which are also federally listed.

The use of cooling towers can also increase the amount of solid wastes generated

by a facility. Recirculation of cooling tower water can increase the concentration of

certain chemical constituents, thereby requiring the blow-down to e treated in a

wastewater treatment system. The concentrated pollutants removed from the blow-down

add to the amount of solid waste generated by the facility.

The industry standard is to install cooling towers immediately adjacent to the side

of the boiler house where the steam turbine is located. Such a configuration is most

effcient because it reduces pressure losses. However, this typical configuration is not

possible on the MTS site because of existing site constraints.

Use of "Grey" Water

Grey" water, or reclaimed water, refers to treated municipal wastewater, which

can provide an additional source of water for cooling and processing at electric

generating facilities. While this may provide a good alternative for cooling tower make-

- 12 -
up water, the volume required for most once-through cooling facilities cannot be satisfied

through the use of local grey water supplies. The Holyoke Water Pollution Control

Facility (HWPCF) is the closest municipal wastewater treatment facility, located

approximately 8.3 rivermiles downstream from MTS, and has a design flow of 17.

MGD. With the design flow oftwo-pump operations at MTS as 133.2 MGD, the

HWPCF could only provide a maximum of 13 percent of the flow required to operate the

current once-through facility. However, ifMTS were converted to a closed loop cooling

facility, the HWPCF would likely be able to provide a suffcient volume of cooling water

to MTS, however engineering a piping system to deliver the water 8.3 rivermiles

upstream may not be a feasible or cost-effective solution.

Flow Reduction

Flow reduction is a potential method of reducing entrainment and impingement.

MTS normally operates one circulating water pump during the winter and spring seasons

(November to April) and two pumps during the summer and fall seasons (May to

October). Two pumps are used to maintain plant operating effciency and plant load due

to the elevated Connecticut River water temperatures during those months.

Considering the MTS currently maximizes one pump operation and has a high

operating capacity factor over the last five years, any additional flow reduction will be

difficult to realize without affecting electrical load and delta T through the condenser. In

order to further reduce water intake during the summer months, when two pump

operation is utilized, and maintain permitted maximum outflow temperature of 102 o

electric generation would have to be reduced. To keep the plant cooling based on one

pump operation it is postulated that during the months of July and August the plant would

have to reduce its electric output by approximately 37%. Additionally, the plant output

would have to be reduced by 21 % during the months of June and September. This would

allow for one pump operation year round. Since the plant operates with one pump during

the cooler months (Nov-April) this would result in a 47% reduction in flow during the

May to October months. However, this drop in production would cost the plant

approximately $4 million per year in lost revenues using $.04/kWh. As a result, flow

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reduction is not considered a viable alternative to reduce impingement further beyond

that already realized due to current operations and presence of the electric fish barrer.

The use of variable frequency drives (VFD) for controlling motor speed, and

therefore pump flow, is a potential method of reducing cooling water flow at times oflow

load operation. Installation of the VFDs on the circulating water pumps would require

temporarily disabling the pumps when the final tie-in of the VFDs is accomplished. It

was assumed that only one circulating water pump would be removed from service

during the installation and that the work will be accomplished while the plant only

requires one pump operation in order to avoid performing the work during a scheduled or

forced plant shutdown.

Pump costs vary significantly depending on capacity and materials. There are

other variables to consider when changing to a VFD system, such as whether reducing

motor speed wil impact the pump performance sufficiently to warrant installation of a

new pump. Plant performance and equipment may also b impacted. IfMTS needed to

replace the circulating water pumps to meet flow reduction measures, capital costs could

be expected in the range of $400 000 for each pump, excluding motors.

However, it is anticipated that reduced flow from VFDs ab )Ve that already

achieved would provide only a fraction of the additional water flow reduction desired.

Typical plant operation now includes maximizing one pump operation. With one pump

operation, a maximum of 70 MGD of intake water is withdrawn from the river versus the

two pump design flow of 133.2 MGD. Due to the current CWIS configuration of

separate pump bays, the intake velocity remains 1.6 ips during both one-pump and twopump operation. However, ifVFDs are installed and implemented, the intake velocity

could be reduced to approximately 0.80 ips during two-pump operation with both pumps

operating at half-speed. In order to further reduce the intake velocity to 0. 5 ips or less

larger screens would have to be incorporated into an expanded CWIS. The system

changes required to obtain reduced flow in the summer would result in a minimal

reduction of flow, unless the NPDES permit allowed a higher discharge temperature. 

addition, the use ofVFDs would have to be evaluated as to the potential power loss due

to condenser cooling water delta T limitations. If the permitted 32 degree delta T limit

- 14 -
for one-pump operation was allowed during the summer period, an increase in the

maximum temperature cooling water outfow to 115 of would be needed. This increase

in discharge temperature would allow one-pump operation to continue throughout the

year and result in a summer time reduction in design flow of 47% (133.2 mgd versus 70

mgd). The postulated reduction in water requirements would be closer to 33% based on

recent, 2000 to 2004, actual flow data. One-pump operation would result in significant

power reduction during the warmer summer months. Overall, this would decrease

cooling water usage by approximately 27% compared to most recent flow data.

Additional reductions may be available in the cooler winter months with an additional

increase in the delta T. Again, any changes in delta T limits would result in a reduction

in power generation or the need to replace the entire condenser as well.

To reduce flow velocities at or below 0.5 fps and cooling water flow reductions

approaching 90%, VFDs would have to be utilized in conjunction with new larger

screens, which would require expanding the CWIS. Since state and federally listed

endangered mussel species (yellow lampmussel, eastern p'ondmussel) inhabit the

Connecticut River in the vicinity of the MTS, and several endangered, threatened, and

special concern dragonfly species inhabit the riparian zone in the vicinity ofMTS

expanding the CWIS will likely cause adverse environmental impacts to the habitats of

these already stressed organisms. In addition, the resulting system temperature changes

may likely require that the turbine condenser be replaced.

Fish Return System Upgrade

Upgrading the current fish retur and screen spray wash systems at MTS wil

likely reduce impingement mortality by ensuring that trapped organisms removed from

the traveling screens are safely returned to the Connecticut River alive. Under the current

operating scenario, the traveling screens are cleaned with the screen wash system. Water

for the screen wash system is provided by one 250 gpm, 70 psi rated screen wash pump.

When the screen wash pump operate, it withdraws water from the discharge side of the

circulating water pumps, where water temperatures can be as high as 32 of warer than

the Connecticut River water temperatures.

- 15 -
The pressure spray from the screen wash pumps is directed outward towards the

screen and washes debris and organisms into an adjacent debris trough. The spray water

also serves to sluice away the screened material. The debris and spray water is directed

into a smooth, half-open sluiceway to a point immediately outside of the switchyard. 

this point, there is a large drop-off into a culvert. Sluiced material travels down the

culvert into a partially open manway. A pipe from the manway discharges the debris to

the Connecticut River at a point downstream of the CWIS.

There are two issues to address with the current fish return and spray wash system

in order to decrease impingement mortality at MTS. One issue involves the temperature

of the spray wash water. Organisms acclimated to Connecticut River water temperatures

can become thermally shocked when subjected to the higher water temperatures of the

screen spray wash system, especially in the winter months when the temperature

difference can be as high as 32 of. To reduce the potential for thermal shock to

organisms, the spray wash system could be designed so that supply water comes from the

intake side, rather than the discharge side, of the circulating water pumps. Through

consultation with MTS operations personnel, the infrastructure to change the system over

is in place, however it is not currently used since the spray wash pressure was not high

enough to effectively remove impinged debris and organisms from the traveling screens.

MTS is currently developing a solution to address both the temperature and pressure

issues of the spray wash system.

The second issue with the current fish return system involves the path in which

organisms removed from the traveling screens must successfully traverse to be returned

to the Connecticut River. As described above, the sluiceway is not enclosed, and

therefore organisms are subj ected to weather and predation by other larger organisms as

they are sluiced toward the manway. The entrance to the manway is elevated

approximately 4 inches above the surrounding ground. Organisms capable of entering

the manway are ensured a safe return to the Connecticut River as the discharge pipe from

the manway to the riverbank is underground.

MTS has begun investigating alternative solutions for upgrading the fish return

system to ensure the safe return of impinged organisms to the Connecticut River. While

- 16-
impingement mortality would be reduced by approximately 40%, no benefit to

entrainment will be realized through these technology upgrades.

Traveling Screen Upgrades (Ristroph. Dual-flow) with Fish Return System

The existing traveling screens at MTS do not have any Ristroph-type of fish

handling buckets. Ristroph traveling screens have been used at several power plants in

estuarine, river and ocean settings. The screen lips are typically enlarged and cup-shaped

such that fish carred up the screen face during screen rotation are submersed in water

and gently washed into the fish return trough using a low pressure spray directed either

from within the screen outward or from outward toward the screen face. Ristroph screens

have a smooth mesh (flat wire) screen and a non-metallic basket formed to significantly

reduce vortexing within a canted basket which results in less injury to fish, although

through-screen velocity will slightly increase with this design. Ristroph traveling screens

are designed to operate continuously.

The cost of retrofitting Ristroph screens for the two traveling screens at MTS

would be approximately $2 million. This cost is based on installation of new screens

with fish buckets, additional spray water for the fish retur and a 500-foot long fish

sluiceway that returns fish and debris to the river. This costs does not include

modifications to the intake structure to accommodate the larger screens. O&M costs

would be approximately $144 000 based on full load plant operation, and are not reduced

to account for current fish screen O&M costs.

Dual-flow traveling screens have more available through-flow screen open area

for a given intake flow compared to standard, single through-flow traveling screens. The

dual-flow screens are oriented parallel to the direction of intake flow and use an "outsideto-inside" (or inside-to-outside) flow pattern to ensure that debris is always maintained on

the upstream side. The interior space between the upward and downward moving screen

panels is closed off on the upstream side, so screened water exits toward the pump

(downstream side of screen). In this manner, both sides of the screen are filtering flow

and debris and organisms that are larger than the traveling screen mesh size will not be

carred-over into the pump bay.

- 17 -
Dual-flow traveling screens that are two times as wide as the existing throughflow traveling screens, with fish buckets were analyzed. Costs assume there is sufficient

space available between the existing screen location and the curtain wall to modify the

intake structure to accommodate the larger screens. Capital costs would be

approximately $2.5 million, not including potential changes to the intake structure. Also

changing the screen configuration may impact pump suction flow conditions which

would require hydraulic model testing at an additional cost. O&M costs for the dual-flow

screens would be similar to the Ristroph-type screens described above.

Barrer Nets

Barrer nets have been applied at several large power plants (EPRI 1999) to

reduce impingement. Important factors to be considered include mesh size, through-net

velocity, debris loading, ice, freshet flows and seasonal deployment consistent with

timing of expected impingement.

The most effective mesh size must be determined. A mesh size of 3/8-inch was

evaluated in the costs below. Ultimately, the mesh size selected must be able to exclude

the fish most likely to be impinged at MTS and be sized large enough such that

biofouling and debris loading do not become unmanageable, thereby adding significantly

to O&M costs. Conversely, river currents assist in dislodging debris that accumulates on

nets, which may reduce O&M costs.

Through-net velocity is directly related to the size of net required and affects the

cost of the net. EP A evaluated a through-net velocity of 0.06 fps (EP A 2004b). This

corresponds to an approximate barer net length of 172 feet at an assumed average water

depth of 20 feet for MTS. The total capital cost for the installation of a net this size at the

MTS intake is approximately $45 000. This cost includes installing two barrer nets

between evenly spaced pilings and two spare replacement nets. It is recommended the

net be installed between evenly spaced pilings for added support due to river currents.

Based on operating experience of an installed barrer net in the Connecticut River

upstream ofMTS, the estimated O&M cost to clean the nets and replace a portion of the

- 18 -
nets each year is $101 000 and perhaps even higher because of high levels ofleaf debris

in the river during the fall. The O&M cost is also based on operation for 240 days/year 

account for ice formation in the river during the winter months and spring freshet. O&M

costs wil be considerably higher for operation based on durations longer than 240

days/year. Because the existing traveling screens would be maintained in this scenario

the $80 000 is an incremental amount ofO&M and not replacement of the current

traveling screen O&M costs. Installing a barrer net does not require a plant shutdown so

there would not be any costs associated with lost generation.

4.12 Electric Fish Barrer

An electric fish barrer has been installed and operated at MTS since 1960. The

normal mode of operation is to have the electric fish barrer turned on. The Model 2A240 Electric Fish Control Unit is a pulse-generator that supplies power to an electric fish

screen located at the entrance of the CWIS. The screen consists of an electrode system

comprising insulated and grounded electrodes submerged in water. The pulse generator

uses an electric circuit which charges a capacitor bank to a preset voltage, and

automatically discharges stored energy through a series of Ignitron tubes into the water.

A special circuit controls the pulse repetition rate by triggering the ignitron, and can be

adjusted to compensate for local water conditions and various species of fish. The

system is powered with 110/130 Volt, 60 cycle, 1 phase A.C. supply.

In theory, the pulses of energy discharged into the water are sensed by

adultjuvenile fish approaching the CWIS entrance and evoke certain avoidance reactions

by the fish. Essentially, this technology relies on the fish's capability to sense and swim

away from the electrical pulses in the water column to avoid entering the CWIS.

Therefore, while impingement abundance may potentially be reduced, there is no

entrainment relief realized from the electric fish screen since larvae act as passive

particles in the water column and do not possess the ability to swim at this life-stage. 

2006-2007, the effciency of the electric fish screen was studied during the impingement

monitoring program at MTS. Between September 2006 and May 2007, eight sampling

events were conducted on days following routine impingement sampling to observe

potential differences in impingement abundance with the electric fish screen off (normal

- 19 -
operation at MTS is to have the screen on). Statistical comparison ofthe two data sets

revealed no significant differences in the number of organisms impinged with the electric

fish screen variable. Therefore, since this technology is not effective at reducing neither

entrainment nor impingement, it is not considered BT A for reducing adverse

environmental impacts at MTS.

Cylindrical Wedge Wire Screens

Cylindrical wedge wire screens are designed to reduce impingement and

entrainment by physical exclusion and by exploiting hydrodynamics (EP A 2002). In

order to effectively reduce entrainment, the mesh of the screens must be appropriately

sized to physically exclude organisms typically susceptible to entrainment in the vicinity

of the station. Screen mesh sizes range from 0.5 to 10 mm, however 1.0- 0 mm mesh

screens are most commonly used to effectively reduce entrainment. Evidence at the

Logan Generating Plant (Logan) located on the Delaware River indicated that installation

of I-mm cylindrical wedge wire screens reduced entrainment by 90 percent as compared

to conventional traveling screens (EP A 2002). While no impingement data were

available for Logan, retrofitting wide-mesh wedge wire screens at Eddystone (located on

Delaware River) generally eliminated impingement.

While cylindrical wedge wire screens have proven effective at reducing

impingement and entrainment at the facilities mentioned above, site-specific conditions

may enhance or reduce the effectiveness of this technology. In general, cylindrical

wedge wire screens are best utilized in a high flow environment where passive flows will

aid in moving fish and larvae past the screens or flush them off the screens mechanically.

It is generally thought that this technology wil work best when ambient flows are

sufficiently high to promote self-cleaning, although automated flushing (hydroburst)

systems are commonly used to aid cleaning. In the case ofMTS, the amount ofleaves

present in the river during the fall season will likely require frequent cleaning ofthe

wedge wire screens, thereby increasing O&M costs for that time of year. Consultation

with MTS operators also indicated that the amount of water celery (VaWsneria

americana) removed from the traveling screens during late summer is considerable, and

- 20-
therefore will require additional maintenance and cleaning effort for that time of year as

well.

Additional site-specific considerations include design intake flows and location.

Since the design of cylindrical wedge wire screens serves to reduce intake velocities

more screens are required to maintain the supply of water to facilities with larger design

flows. If suffcient space and depth are unavailable in the waterbody to install numerous

screens, then the use of this technology will not be feasible. Interference with navigation

due to installation of submerged equipment may present public safety issues, especially

when hydroburst systems are employed for cleaning the screens. When the screen

cleaning occurs with the airburst system, significant quantities of bubbles rise to the

surface of the water body potentially creating hazards for smaller water craft. Danger to

boaters and MTS liability may be eliminated by cordoning off the area with buoys or

pilings, however a rather large area will require protection due the size and location of the

screens needed for the MTS. The frequency with which the airburst system is used

depends on the debris load in the water column and the growth rate of algae and other

sessile organisms.

At MTS, the cylindrical wedge wire screens would be installed by piping from the

existing 8-foot diameter CWIS intake pipe to a connecting sheet pile wall in front of the

intake (acting as a common plenum), and then to the screens at a point further offshore.

The depth of the Connecticut River in front of the CWIS to mid-channel is 15 feet deep

(MLWL). At this depth, multiple numbers and sizes of wedge wire screens can be

installed in a manifold arangement to manage the 92 500 gpm design flow. Generally,

costs for these screens increase with larger quantities of smaller diameter screens that

could be replaced by smaller numbers of larger screens, so the largest possible screen

arrangement is evaluated for costing.

At a depth of 15 feet and a flow of92 500 gpm, three, 6-foot diameter T-screens

could be installed with an overall length of approximately 20 feet each. This size screen

requires a 12-foot depth at the point of installation. A distance of250 meters east ofthe

CWIS was used in the cost calculations due to the higher river currents occurrng at this

point compared to at the CWIS. The estimated capital cost for this option utilizing 1/8-

- 21 -
inch mesh cylindrical wedge wire screens as established in the EP A' s Technical

Development Document and adjusted for site-specific conditions at MTS is

approximately $7 million. A minimum two-week shutdown for installation and testing

could exceed $2.0 million in lost generation. These costs are based on 304 stainless steel

wedge wire T-screens (for freshwater environments), a connecting sheet pile wall in front

of the intake (acting as a common plenum), pre-stressed concrete cylinder underwater

piping and new airburst screen cleaning systems. Capital costs will increase if a preengineered structure is needed to house the new air-burst system equipment on shore.

The majority of the O&M costs are associated with the air burst system. It is

estimated that the annual O&M cost for the MTS intake will be $32 000 for 1/8-inch

mesh screens. These O&M costs include periodic cleaning and inspection, O&M for the

air burst system, and power costs for operation of the air compressors.

In addition to debris-loading and navigational issues, endangered species in the

vicinity of the MTS CWIS may prevent this technology from being feasible. Installation

of the new screens in the water body would likely impact yellow lampmussel habitat in

the benthic environment of the river.

Expanded Intake

An expanded intake concrete structure with sheetpile walls could be installed in

front of the existing 8-foot diameter intake pipe at MTS. The new intake area "plenum

acts as a surge volume between the offshore intake and the circulating and river water

pumps to reduce the velocity below 0.5 fps at both the intake pipe and in the intake

structure. The new structure would house either the two Ristroph or dual flow traveling

screens, as described above in Section 4. 10. Capital costs were estimated to be

approximately $6 milion. A six-week shutdown for installation ofthe expanded intake

could exceed $6 milion in lost generation. This assumes the existing circulating water

pumps could continue to operate until the sheet pile side walls are installed.

The habitats of a number of endangered species will be impacted if construction

occurs within the riparian zone along the Connecticut River. Endangered mussel and

- 22-
dragonfly species, as well as the shortnose sturgeon, inhabit areas in the vicinity of MTS

and likely will require further study prior to conducting any construction activities in

these areas.

4.15 CWIS Relocation

Intake location can have an effect on impingement and entrainment if the intake

can be located in an area of decreased biological productivity. Offshore intakes can be

located in these areas of reduced biological productivity and achieve reduced levels of

impingement and entrainment from baseline conditions. An offshore intake design, such

as cylindrical wedge wire screens or velocity caps could reduce impingement by reducing

velocity at the inlet point and/or provide impingement protection equivalent to that of the

existing screens with a fish return system. However, relocating the intake further

offshore may not be warranted at MTS as the distribution of fish eggs and larvae and

adult fish is not likely to be suffciently different than that at the current intake location.

A study performed by Kynard et al (2003) in the vicinity?fMTS indicates that larger

numbers of fish will be impinged the further away from the shoreline and the closer to the

channel the intake is placed. In addition, the hydraulic zone of influence modeling

completed for the current intake location (Section 2. 1) indicates that the current zone of

influence is small and localized thus relocation of the intake would most likely not reduce

impingement nor entrainment impacts.

The installation of offshore intakes is predicated on the premise that productivity,

fish abundance and the occurrence of fish eggs and larvae diminishes as one moves

further away from the shore line littoral zone. Siting decisions incorporating offshore

intakes located some distance from near shore areas and embayments based on

comparative onshore-offshore ecological data include: the St. Lucie plant with an intake

(and velocity cap) 1 200 feet offshore, the D.C. Cook plant located on Lake Michigan;

the Fort Calhoun Station on the Missouri River; and, Seabrook Station which utilizes an

intake (and velocity cap) located in the Atlantic Ocean 1.3 miles offshore from a nearby

estuary where entrainment of mollusk larvae was of concern.

- 23 -
As noted here, offshore intakes are typically installed in conjunction with

velocity caps. While limited, existing data suggests that the velocity cap provides some

benefit for reducing impingement as they elevate the intake opening off the bottom and

create velocity vectors that may act as behavioral cues eliciting avoidance reactions by

fish.

Impacts from the construction and operation of offshore intakes are also factors to

consider as one evaluates the relative effcacy and cost of offshore intakes. An offshore

intake would require a significant increase in the amount of biocide needed to control

fouling in the intake structure and within a long intake tunnel. The effects of continuous

chlorination on fish eggs, larvae, juveniles, and adults entrained within an offshore intake

system could be considerable. Biofouling control for an offshore intake would also result

in additional resources (personnel, materials, and labor costs) required to maintain desired

reliability. For example, divers must periodically inspect and clean exterior portions of the

offshore intake. The environmental impacts from construction of an offshore intake would

also have to be evaluated in fuher detail and would require significant permitting from a

number of state and federal agencies. Impacts would include . at minimum, a displacement

of benthic flora and fauna due to dredging and other activities associated with construction

increased turbidity during the period of work, and limits to navigation in the area of

constrction.

- 24-
OTHER INFORMA TION REQUESTED

The final request from EP A to FirstLight Power includes providing the combination of

existing and proposed technologies and operational measures to be implemented at the Station

for which MTS believes the location, design, capacity, and construction reflect the Best

Technology Available (BTA) for minimizing adverse environmental impacts. A number of

technologies were assessed for MTS and many (mechanical draft cooling towers, cylindrical

wedge wire screens, expanded intake, CWIS relocation) were determined to have the potential to

impact endangered species. Others (use of grey water and natural draft cooling towers) were

determined to be technically infeasible, while flow reduction scenarios and variable speed pumps

did not provide any additional benefits as MTS is currently maximizing its flow reduction

potential. Thus FirstLight Power believes that upgrading the fish return and spray wash systems

reflect BT A for minimizing adverse environmental impacts. Observations during the current

ongoing impingement study at MTS suggest that very low numbers of fish are impinged. 

those, approximately 40 percent of the fish removed from the traveling screens are alive

following impingement. Redirecting the supply of water for the screen spray wash pumps to an

ambient source may increase survival following impingement, thereby reducing impingement

mortality. In addition, upgrading the existing fish return system to ensure fish removed from the

traveling screens are safely returned to the Connecticut River will also reduce adverse

environmental impacts due to MTS operations.

While this combination of upgrading existing technologies may not reduce entrainment at

MTS, other technologies suitable for reducing entrainment were ruled out for application at

MTS. There are no current entrainment data available for MTS to accurately quantify their

potential impact; however MTS has plans to conduct an entrainment monitoring program

beginning in early 2008. Review of316(b) entrainment information indicates that impacts to

ichthyoplankton fauna due to entrainment at steam electrc generating facilities which typically

withdraw less than 5 percent of the anual average daily flow of the river are minimal. MTS

typically withdraws an average of 1.4 percent of the Connecticut River mean annual flow.

- 25 -
US EP A (United States Environmental Protection Agency). 2002. Case study analysis for the

proposed section 3l6(b) phase II existing facilities rule. February 2002.

US EPA. 2004. National Pollutant Discharge Elimination System-Final Regulations to

Establish Requirements for Cooling Water Intake Structures at Phase II Existing

Facilities; Final Rule. Federal Register Vol. 69, No. 131 (Friday, July 9):41 576- 693.

US EP A. 2004a. Regional analysis document for the final section 316(b) phase II existing

facilities rule. EPA 821- 02-003. February 2004.

US EP A. 2004b. Technical Development document for the final section 3l6(b) phase II

existing facilities rule. EPA 821- 04-007. February 2004.

US FWS (United States Fish and Wildlife Service). 1978. Entrainment impact estimates using

the equivalent adult approach. FWS/OBS-78/65. Washington, D. C. 14 pp.

- 27-
REFERENCES

EPRI (Electric Power Research Institute). 1999. Fish Protection at Cooling Water Intakes:

Status Report. EPRI Report No. TR- 114013. Palo Alto, CA.

EPRI. 2000. Technical evaluation of the utility of intake approach velocity as an indicator of

potential adverse environmental impact under Clean Water Act Section316(b ).EPRI

Report No. 000731. Palo Alto, CA.

EPRI. 2002. Cooling System Retrofit Cost Analysis Report. EPRI Report No. 1007456.

Palo Alto, CA.

EPRI. 2003a. Evaluating the Effects of Power Pfant Operations on Aquatic Communities

Summary of Impingement Survival Studies: Technical Report. EPRI Report No.

1007821. Palo Alto, CA.

EPRI. 2003b. Enhancement Strategies for Mitigating Potential Operational Impacts of Cooling

Water Intake Structures, Approaches for Enhancing Environmental Resources: Technical

Report. EPRI Report No. 1007454. Palo Alto, CA.

EPRI. 2004. Extrapolating Impingement and Entrainment Losses to Equivalent Adults and

Production Forgone: Technical Report. EPRI Report No. 1008471. Palo Alto, CA.

EPRI. 2005. Entrainment Abundance Monitoring Technical Support Document. EPRI Report

No. 1011280. Palo Alto, CA.

Handy- Whitman Index of Public Utility Construction Costs, Whitman Requardt and Associates

Baltimore, Maryland.

Hogarth, W. , and K.L. Nichols. 1981. Brunswick steam electric plant intake modifications to

reduce entrainment and impingement losses. In B Dorn and J.T. Johnson eds.

Advanced intake technology for power plant cooling water systems. 272-282 pp.

Kleinschmidt Associates. 2005. Cooling Water Intake Structure Report 40 CFR 122.21(r)(3).

Prepared for Holyoke Water Power Company. Holyoke, MA. 14 pp. plus appendices.

Kleinschmidt Associates. 2006a. Cooling Water System Data Report 40 CFR 122.21(r)(5).

Prepared for Holyoke Water Power Company. Holyoke, MA. 8 pp. plus appendices.

Kleinschmidt Associates. 2006b. Proposal for Information Collection. Prepared for Holyoke

Water Power Company. Holyoke, MA. 59 pp. plus appendices.

NUSCO (Northeast Utilities Service Company). 1986. The effectiveness of the Millstone Unit 

sluiceway in returning impinged organisms to Long Island Sound. 18 pp.

Taft, E.P. 2000. Fish protection technologies: a status report. Pages 349- 359 in LWisniewski

editor. Power plants & aquatic resources: issues and assessment. Environmental Science

& Policy 3 (Supplement 1). Elsevier New York.

- 26-
APPENDIX A

FIGURS
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""1 '7-.

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. ,P "" 

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\\\\\ .. , \ \ \ \, \\\\\\ .. \. .. \.. .. , \. . \ \,\, ,\, , ,.. .. .. \ \, \ ..\,, \ \ \. , \ .. \ \ \, \ , \ \ \ \ . \ \ \. .. \ \. \ ,, \ \ \ \ , \. .. \ \. \. \ \. \\ \, ,\, \. . \. \\ \.

115

756

397

718

038

359

679

000

Figure 1. Hydraulic Zone of Influence output for Mount Tom Station.