Docket OW-2002-0049 DCN#: 6-50460 Young,J., W.Dey, S. Jiizks, N. Decker, M. Daley, and J. Camriglit,ASAAnalysis and Dynegy Evaluation of Variable Pumping Rates as a N&f Reduce Entrainment Mortalities 

### EVALUATION OF VARIABLE PUMPING RATES AS 

### A MEANS TQ REDUCE ENTRAINMENT MORTALITIES

John Young William Dey StevenJinks Nancy Decker ASA Analysis & Communication, hc. Washmgtonville,

### NY

Martin Daley John Camright Dynegy Northeast Generation Newburgh,

### NY



### Abstract We evaluatedthe potential of a load-based flow strategy (vary flows with generating load to use minimum flow sufficientto meet specified thermal characteristics) to meet the USEPA proposed entrainment reduction targets (60% to 90%) for the Roseton Generating Station. Actual generatingloads from 1999­ 2001 were used as the operation schedule. Operatingrules that would minimize flowswhile keeping discharge temperaturesbelow a maximum of 20” to 40” 

### C and 

### AT below 15”to 3Q” C were used to predict cooling water use. These strategieswould have reduced cooling water use by 63% to 

### 70% from the full withdrawal capacityofthe station. Stripedbass entrainmentnumbers would be reduced 

### fkom 71% to 75% from a hll-flow full-operationbaseline condition. When expected entrainment survival at the Roseton Station was factored into the analysis,potentialreductions of stripedbass losses increasedto 89% to 91%. For facilities that vary the generating loads to meet peak loads, a load-basedflow strategy appearsto be a viable option to approach or meet the reduction targets ofthe proposed new regulations. The achievable reductions were not highly sensitiveto the thermal design criteria, which should allow plant operatorsto find a set of thermal criteria that reduce entrainment and still allow efficient operation of the facility. The ultimate utility of load-based flow strategies to achieve compliancewith entrainmentreduction targets will depend on the final definition of “baseline” conditions. Ifbaseline is defined as the full capacity of a station to entrain fish (hllflow and full generation)then a load-based flow strategy can be an important component to achieving compliance. However, ifbaseline becomes defined by past operating levels and practices, then it is unlikely that a load-based flow strategy could achieve the additionalreductions required, especially for facilities that already operate at reduced flows as a matter ofpractice. Stationsin this situation would be left to choose between closed cycle systems, or application for site-specific conditions.

### Introduction The new regulations that the United StatesEnvironmentalProtection Agency OJSEPA) has proposed for 93 16(b)of the Clean Water Act will pose distinct challengesto operators of electric generatingfacilities to meet criteria for reducing entrainment and impingement mortality. A number of technologies are currently available that can eitherreduce the numbers of fish that are impinged,by keeping them away from the screens through physical exclusion or behavioral means, and/orto improve the survivalrates of fish that are impinged. However, for entrainmentmortality, there are far fewer options. Physical exclusion systems, such as the Marine Life Exclusion System, are currentlybeing tested, but even if exclusion systems are successfblin some locations be applicability may not be universal. Behavioral exclusion is not effective because most entrainable stages do not have swimmingcapabilities or a behavioral repertoire sufficientto escape the flow into a power plant intake. Thus, reducing the coolingwater flow is the primary means for reducing entrainment. We explored the potential of variable speedpumping as a means to meet entrainment reduction goals at an existing power station on a tidal river. ’ The Roseton Generating Station is situated on the west shore of the Hudson River, 105

### kmupstream from the Battery, a setting that, according to the proposed Phase I1 regulations, would require a reduction of entrainmentbetween 60% and 90% ofbaseline levels. The station, which began commercial operation in 1974,has two 600-MW oil/gas-fired generating units that use Hudson River water for condenser cooling. The single intake structure contains four circulatingwater pumps that draw through 8 intake bays. Six of the bays are fitted with conventional 

### 9-mm mesh traveling screens, and two have dual-flow screens. The four pumps feed cooling water into a single inlet conduit that servesboth units. Dependingupon generating loads and river water temperatures, the plant may be operatedwith 2 pumps (1,584 m3/min), 3 pumps (2,124 m3/min),or4 pumps (2,424 m3/min). Under full generation and full flow, the design AT for the station is 

### 9.8”C. Although the Roseton Generating Stationwas originally constructed as a base-load facility, its recent use has been to follow the daily and seasonal demand patterns. 

### In this mode its generating loads can vary substantiallybetween peak and off-peak periods. If cooling water use could be matched closely to the generating load, then entrainmentnumbers could be reduced. Because a substantialbase of entrainment abundanceinformation exists for the Roseton Station, it is possible to quantitatively assess the potential of a variable flow strategy to approach 

### or achieve the USEPA’s target reduction levels. 

### In addition, the Roseton Station also has a large amount of data on entrainment survivalrates for key taxa, therefore it is possible to assess the contribution entrainment survival provides towards meeting USEPA’s target reduction levels. Availability of site specific entrainment abundance and survival data provides a reasonable and defensible basis for the design ofprudent operating rules that would guaranteethat flow reductions do not actually exacerbate entrainmentmortality. 

### Methods The Roseton Generating Station is an excellent site for evaluation of variable pumping rates due to the amount of infomation available. Although an evaluation could be conducted on a theoreticalbasis using hypothetical abundancepatterns and entrainment survival rates, the Roseton Stationpossess a large base of empiricalinformationwhich makes the evaluationprocess highly relevant and establishesthe groundwork for additional evaluation that could ultimately lead to renewed dischargepermits. The available data included:

2

### Seasonal and daily operating pattern In the post-deregulation electric generating industry, it is very difficult to predict future operating patterns. Plant operations are no longer determinedby demand patterns within a utility's service territory,which are relatively predictable in the short term, but are now determinedby the market. Rather than attempt to predict future operations ofthe Roseton Station, we used the 1999-2001 actual operation patterns as examples ofhow the station operates, and might be expectedto operate in the future. The Roseton Station varies its generation to match seasonal and daily load changes, thus hourly information on the intake temperature, coolingwater flows, and generating load for each unit were used to establish the operating pattern for evaluation (Figure 1). 

### Density of 

### entrainable life stages Entrainment densitieswere sampled from May through July from 1983-1987using a net-in-barrel pumped sampling systemwith a 0.5 

### mm mesh net at a rate of approximately 1 m3/min. (Figure 2). Sampling location was in the discharge seal welljust prior to the point where the conduit entered the river. Samplingwas conducted on a variable frequency, from 1to 7 days per week. On each sampling event, 24 l-hour samples were collected and analyzed. During laboratory analysis, ichthyoplantkonwere identified to species where possible, and subsamples ofkey taxa were measured to the nearest 0.1 

### mm. The data were used to estimate the density (number of organismsper m3)of each 1-mm length interval during each hour of each day sampled. The densities on bunsampled days were interpolatedbetween sampled days on an hour and length interval basis. The final expected density pattern was then developed from the average density over the 1983-1987 annual patterns (Figure 3). For this evaluation, only data on stripedbass were used, but the results would be similar for other taxa whose temporal pattern is similar to striped bass. 

### Mortality of 

### entrained organisms Entrainment mortality studies were conducted from 1976-1980. Samplingwas conducted with pumped larval flumes, and rear-draw and pumpless systems (EPRI 2000). Samples were collected from the intake to establish the level of samplingmortality, and simultaneouslyfrom the discharge. Initial survival in samples was used to estimate a logisticregression equation (Sokal and Rohlf 1995)to predict survival as a function of length of organism and dischargetemperaturerange. For this evaluation, only the data for 1980were used because the most advanced sampling techniques were used in that year and the sample size was relatively large (1252 individuals). Thepredicted logistic regression curves for discharge samples collected at temperatures < 30°C, and the intake samples (Figure 4) were used to estimate the mechanical component of entrainmentmortality accordingto Abbott's formula: Mechanical mortality = 1

- (Survival in discharge samples) / (Survival in intake samples) Because few larvae were collected under higher dischargetemperatures,laboratory thermal tolerance data were used to estimate the thermal mortality component based on lower and upper temperature thresholds. If the predicted exposure temperature was below the lower threshold (TL)then thermal mortalitywas 0. Temperatures above the upper threshold (TU) were assumed to result in 100% mortality. Between TLand



### 3TU

~ mortality rate was linearly related to temperature. The TLand TUvalues were estimated as functions of ambienttemperature, exposure temperature, and transit time (CentralHudson et a1 1999). The mechanical and thermal components ofmortality were assumed to be independent: EntrainmentMortality = 1
- (1

- Mechanical Mortality)(1

- Thermal Mortality) 

### Evaluation

### Process There are five distinct steps in the evaluationprocess; Set hourly generating load and inlet temperatures. The actual 1999-2001data were used to establish these values. Use ofpast operating data essentiallymakes the evaluation an analysis of the theoretical entrainmentlevels in these years ifthe flow reduction strategyhad been followed. The calculation baseline for comparisonwas 365-dayper year operation at full flow (2,424 m3/mh),with an assumed 100%mortality 

### of entrained organisms. Use operating rules to establish cooling water flow and discharge temperatures. The basic procedure ofthe load-based flow strategyisto use the minimum coolingwater flow required to maintain dischargetemperature and AT within specifiedbounds. We examined a range of maximum hscharge temperatures from 20" to 40" C in increments of 5"C, and AT from 

### 15" to 

### 30°C in incrementsof 

### 5°C. The analysis was conducted as ifthe station operators would, on at least 

### an hourly basis, adjust cooling water flows to match the current generation load. The AT for a given generating load, and transit time through the cooling system, are inverselyproportionalto cooling water flow. Analysis was conducted for fill-flow full-generation, and for actual flows and generation Estimate numbers of organisms entrained. Entrainment numbers were estimated as the product of the estimated hourly densities and the hourly cooling water flows. The goal to reduce entrainmentwas aided, for some later life stages, by the offset in daily generationload and entrainment density (Figure 5) in whch highest entrainment densities occurred at night when generating load and cooling water flow were lowest. Calculate mortality component. The numbers dying in each hourly interval was calculatedby adjusting the total number entrained by the hourly projected mortalityrate. The mortality rate is the combined effect of mechanical and thermal mortality calculated for each length interval. Estimate percentage reduction from baseline. The hourly estimatesof numbers entrained and number killed were summed for each year. The totals from the load-based flow strategy were compared to the full-flow full-generationbaseline. Estimatesbased on actual flows were also calculated for comparison. Percent reductions were calculated as: %Reduction = 100x (BaselineNumber Killed

- StrategyNumber Killed)/ Baseline Number Killed For the baseline number killed, 100% entrainmentmortality was assumed. For the strategy number killed, both the empirically-basedestimates, and a 100%mortality assumptionwere used. 

### Results The load-based flow strategy, if implemented during 1999-2001,had the potentialto reduce flows substantially fiom baseline levels (Figure 6). Over all sets of operating rules, flows would have been

4reduced from 63% to 70%, with higher reductions occurring at higher ATs and lowermaximurn discharge temperatures
. For stripedbass, a load-based flow strategywould have resulted in substantialreductions in entrainment and entrainmentmortality at the Roseton Generating Station. For numbers entrained, the average annual reduction was on the order of 75% from the full-flow full-generationbaseline (Figure 7). This reduction was higher than the reduction in flows due to the additional protection resulting fiom the diel pattern in entrainment. Stripedbass densities in the vicinity of the intake are at their lowest at the time when generation, and need for cooling water, is highest. The percentage reduction was relatively insensitive to the maximum dischargetemperature or maximum AT. The range ofreduction in entrainmentwas approximately7 1% to 75% under all combinationsof maximum dischargetemperature and maximum AT. Reductions were near the high end of the range at the highest ATs and extreme values of maximum dischargetemperature (20" or 40°C). The wide range of conditions that produced relatively similar reductions in entrainmentprovides considerable latitudein finding plant operation schemes that will allow reasonably efficient operation and also decrease entrainment. When entrainment survival estimates for stripedbass were factored into the analysis, the reduction from baseline levels of entrainmentmortality (which are based on an assumption ofno survival) reached approximately90% (Figure 8). As with numbers entrained, the percent reduction was relatively insensitive to the operatingrules, ranging fiom about 89% to 9 1% across all combinationsof maximum discharge temperature and maximum AT. 

### In contrast to the pattern for numbers entrained,the percent reductions of numbers llledwas highest at intermediatevalues of maximum dischargetemperature. 

### Discussion The analysis shows that, for plants such as Roseton that have highly variable operations, a load-based flow strategy could approach or achieve the reductions of entrainmentrequired under the USEPA's proposed regulations. The actual reductions achieved for any taxon would depend upon the timing of the presence 

### of entrainable life stagesrelative to the generating demand on a seasonal, and perhaps daily, basis. Particularly for taxa whose peak densities occur outside the seasonal generatingpeaks, load-based flows could be sufficientto achievecompliance. For taxa that could be expected to exhibit moderate to high levels of entrainment survival, such as striped bass, a strong base of entrainment survivalinformation would provide a safetymargin for potential compliance, or could bring the reduction levels closer to or within the required levels for compliance. Thus stations that entrainrelatively hardy taxa, but have no site-specific information on survival, might consider conducting carefully designed and executed entrainment survival studies in order to be able to include survivalin the assessmentprocess. This evaluation was only ofthe biological potential for load-based flows to reduce entrainment, i.e. does entrainment occur at a time when flow could be reduced below maximum levels, and could flow be reduced enough to achieve compliancewith the reduction targets. The results were encouraging in that a wide range of operating rules (use minimum flow to staybelow a maximum discharge temperature and maximum AT) would meet the target levels of entrainmentreduction. However, significant additional evaluation is necessary before a load-based flow strategycould be considered for implementation. The operatingrules must still be evaluated for operational feasibility and economic implications on a site-specificbasis. To the



### 5extent that these rules would cause departures from a facility’s design operating state, there may be reduced generating efficiency, or additionalrisks of equipment failure. Existingpumps, or pump control equipment may need to be replaced, and the facility’s compliancewith 

### $3 16(a) standards or thermal water quality criteria also must be considered. USEPA’s final definition of “baseline” conditions will be crucial to determiningwhether a load-based flow strategywill be a viable means to achievethe required percent reductions of entrainment. If, as suggested in USEPA’s original proposal (USEPA 2002), ‘‘baseline”is interpreted as the fullpotential of a power station to entrain and kill fish, then a load-based flow strategy may allow many non-baseload stationsto achieve compliance, even without consideringthe issue of entrainment survival. However, ifbaseline is interpreted as past operatingpractices, as has been recently suggestedby USEPA (USEPA 2003) and advocated by some parties (Super 2003), then a load-based flow strategy will likelynot be sufficientto achieve compliance at stations that already operate at reduced flows on a seasonal basis. This interpretation would essentiallypenalize stations like Roseton by requiring them to reduce entrainment 60% to 90% below their already-reduced levels, while stations that historically operate at full flow year-round, regardless of generatingload, would have their full entrainmentpotential as the yardstick for measuringpercent reductions. One way USEPA can apply its reduction criteria fairly and equitablyto all stationswould be to establishfull-flow, full-generation, 100% mortality as the baseline for all facilities. Then any design features, operatingpractices, or technology innovations that reduce the numbers entrained and/or demonstrablyincrease their survival rates would be part of the overall compliancepackage for the facility. If USEPA takes a load-based flow strategy out ofthe compliance optionsby improperly defining the calculationbaseline, then the only options available to many stations will be either closed-cycle cooling or a site-specificdetermination ofBest Technology Available. Given only these 

### two choices, existing facilities that operatewell below maximum capacity are likelyto seek a site-specific determination far more often than USEPA may have anticipated. 

### Literature Cited EA Engineering, Science & Technology (EA). 1984. Roseton and DanskammerPoint Generating Stations EntrainmentAbundance StucZles 1983Report. Prepared for Central Hudson Gas & Electric Corporation, Poughkeepsie,NY. Electric Power Research Institute (EPRI). 2000. Review ofEntrainment Survival Studies: 1970-2000. Palo Alto, CA. Central Hudson Gas & Electric Corporation, ConsolidatedEdison Company ofNew York, Inc., New York Power Authority, and Orange & Rockland Utilities, Inc. 1999. Draft Environmental Impact Statement for the Renewal of StatePollutant Discharge Elimination SystemPermits for Bowline Point 1 & 2, Indian Point 2 & 3, and Roseton 1 & 2 Steam Electric Generating Stations. Poughkeepsie,NY. Sokal, R.R. and 

### F.J. Rohlf. 1995. Biometry. Third Edition. W. H. Freeman and Company. New York. 887 p.. Super, R. 2003. An Overview ofFlow Reduction Technologies for ReducingAquatic Impacts at Cooling Water Intake Structures. Presentation at “A Symposiumon Cooling Water Intake Technologiesto Protect Aquatic Organisms.” May 6-7,2003. Arlington, VA.

6United States Environmental Protection Agnecy (USEPA). 2002. National Pollutant Discharge Elimination System--ProposedRegulationsto Establish Requirements for CoolingWater Intake Structuresat Phase 

### I1 Existing Facilities. Federal Register April 9,2002 (Volume 67, Number 68), pp 17121-17170. USEPA. 2003. National Pollutant Discharge Elimination System--ProposedRegulations To Establish Requirements for CoolingWater Intake Structures at Phase I1 ExistingFacilities; Notice ofData Availability. Federal Register: March 19,2003 (Volume 68, Number 53), pp 13521-13587.

# s 700

600

n



# - I 500 C 

## .- 0 .c, 

# g 400 S 

# 8

L 300 3 0 I 

## 5 200 

# 9 I00

0 1 1 1 1 1 1 1 1 1 1 1 1 1 l I I I I I I l I I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 I8 19 20 21 22 23 24 Hour Figure I Typical diel generating load at the Roseton Generating Station during May-July.



### 8 I

# --- I-=­ 

### 1

w

Figure 2 Net-in-barrelcollection system used for entrainment abundance sampling. (From EA 1984)

94 .E+OI

I.E+OO

e9



### E 1.E-01

- Q) Q 

### 5 Q 

### ,E 

# 2 1.E-02

- S Q 

# i!
I.E-03

.

1.E-04

- , , 8 I I I I I I I 1 I I

Figure 3 Seasonal pattern of entrainment density (# per m3) of striped bass, white perch, American shad, and river herring (all life stages combined) at the Roseton Generating Station basedon 1983-1987 data.1 .oo
0.90
0.80


### a 0.70 

## .- S 

# -E 0.60 3 0.50 S 

# .- 0 0.40 

### ! LL 0.30
0.20
0.10
0.00 0 5 10 15 +intake n = 514 Discharge c 30 n = 655 

# c
Discharge 30-33 n = 97

0 Discharge> 33 n = 6

20 25 30 35 40 Length (mm) Figure 4 Initial survival as a function of length from entrainment samples collected at the intake, and at the discharge sampling locations at temperatures 30°C, 30°-33"C, and > 33°Cat the Roseton Generating Station, 1980.Q)



# .- 2 Yolk-sac Larvae

I.5



# - 3 

# 3 E (II 

# S I 0
rc1 

### $
.c, 

# - (II 

# B 0.5

0 I 2 3 4 5 6 7 8 9 IO I1 12 13 14 15 16 17 18 19 20 21 22 23 24 Hour Figure 5 Dailyvariation in density of entrainable striped bass life stages and generation load at the Roseton Generating Station. (Relative density values above 2 were cut off in order to improve resolutionin 0-2 range.)



### 12Re !ductionfrom

Full Flow Baseline

urn Disci hai Target

Figure 6 Percent reduction from full-flow baseline of total cooling water flow under 1999-2001 operations at the Roseton Generating Station due to a load-basedflow strategy. Maximum discharge temperatures rangefrom 20" to 40°C and maximumATfrom 5"to 15°C.



### 13

### Re!ductionfrom Full Flow Baseline

30 Maximum 

### AT Discharge T'emperature Target 20

Figure 7 Percent reduction from full-flow baseline of numbers entrained under 1999-2001operations at the Roseton Generating Station due to a load-based flow strategy. Maximum discharge temperatures range from 20" to 40°C and maximumAT from 5"to 15°C.

44Reduction from Full Flow Baseline
MaximumAT DischargeTemperature Target :igure8 Percent reduction from full-flow baseline of numbers killed under 1999-2001 operations at the Roseton Generating Station due to a load-basedflow strategy. Maximum discharge temperatures range from 20"to 40°C and maximum AT from 5"to 15°C.

15