# 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

- 1 -

### 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). ..

- 1 -

### 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.

- 2 -

### 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).

- 3 -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.

- 4-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)

- 5 -

### 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). - 6 -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 o

### f 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 o f. 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 o f 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.

- 7 -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.

- 8 -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 - 9 -

### 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 o f blow- down temperature could be routed through a new heat exchanger to reduce the temperature to the current 102 o

### f 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 - 10-

### 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

- 11 -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

- 13 -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 o f 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 o

### f 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 o f. 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 underwaterpiping 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.
CWIS Relocation 4.15 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 

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