MEMORANDUM

Tetra Tech, Inc.

10306 Eaton Place, Suite 340

Fairfax, VA 22030

phone 703-385-6000

fax 703-385-6007

TO: Lisa Biddle, EPA

FROM: John Sunda and Kelly Meadows

DATE: February 12, 2013 

SUBJECT: Analysis of Cooling System Baseline Trends Using EIA Electricity Generator Data

Data from the annual US Energy Information Administration (EIA) Form 860 survey was analyzed to 

determine the distribution of system type and age of electricity generator cooling systems to characterize 

industry trends in the usage of cooling system types for large electric generators. These trends are useful 

in the evaluation of the net impact of various regulatory requirements that affect the selection of cooling 

system type. Specifically, the results of this analysis can help identify reasonable estimates of what 

portion of “new units” (as defined in the 316(b) existing facility rule) would be designed and constructed 

with closed-cycle cooling or the equivalent in the baseline.

1

The most recent available data is from the 2011 Form EIA-860 survey. The file identified as 

“EnviroEquipY2011.xls” includes data specific to cooling systems. Form EIA-860 “collects data on the 

status of existing electric generating plants and associated equipment (including generators, boilers, 

cooling systems and flue gas desulfurization systems) in the United States, and those scheduled for initial 

commercial operation within 10 years of the specified reporting period.” The survey includes requests for 

data concerning “associated cooling systems.” The survey instructions define a cooling system as “an 

equipment system that provides water to the condensers and includes water intakes and outlets, cooling 

towers and ponds, pumps, and pipes. Identify a single plant cooling system, not separate systems, unless 

systems are physically separated, e.g., have separate water intake and outlet structures, where each system 

can be operated independently.” (EIA, 2013) The data from the spreadsheet tab “cooling” was reviewed

and found to include a separate row for each associated cooling system, with many plants reporting 

multiple systems. This analysis treats each system equally.

Data on cooling systems are required only from plants with a generating capacity of 100 MW or more.

The exclusion of cooling systems for generating systems less than 100 MW limits the scope of this data to 

 

1

In this case, baseline refers to what cooling system type would have been constructed in the absence of the existing 

facility rule or closed-cycle cooling requirements for new units. 
larger plants that might typically require an intake flow of 60 to 120 mgd if operating a once-through 

cooling system. As a result, this analysis should include most Phase II generators and also many Phase 

III generators that operate flow reduction technologies such as closed-cycle cooling. The Proposal TDD 

Exhibit 4-3 indicates that about 25% of in-scope generating facilities have design intake flows of 2 to 100 

mgd. Thus, there should be a considerable amount of overlap with the 316(b) questionnaire database since

many of those facilities use closed-cycle cooling.

The EIA Form 860 database also includes a much larger universe of facilities since it includes facilities 

that would be considered out of scope for 316(b).

2 The data evaluated includes 1,640 cooling systems that 

are currently operating and is 80% larger than the EPA in-scope estimate of 912 cooling systems (see

Proposal TDD Exhibit 4-8). Since the EIA database is limited to cooling water systems, it is similar to the 

316(b) questionnaire database in that it does not include generating facilities that do not use cooling 

water, such as combustion turbines, solar, or hydropower. By including a larger scope of cooling water 

using generators, this data is especially useful for estimating 316(b) compliance trends for new units since 

it includes the full range of system design and water sources both in-scope and out-of-scope that would be 

available to new units.

The analysis evaluated only those systems currently operating and those being constructed or planned. 

These are identified as:

 OP - Operating (in commercial service or out of service less than 365 days)

 CO - Units under construction

 PL - Planned (expected to go into commercial service within 10 years)

An important data element used in the analysis was the actual or projected “in-service” year of the 

cooling system. This date is specific to the cooling system and may not necessarily be the same “inservice” date of the generating system. For example, the “in-service” date of a retrofitted cooling system 

should be the date the retrofitted system began operation, provided the design is substantially different. 

For repowered systems where no changes were made to the cooling system, the “in-service” date will 

likely be recorded as the start date for the original cooling system.3 Thus, the data reflects the cooling 

system perspective only and there is no way to distinguish a cooling system associated with new Phase I 

units from those associated with stand-alone/greenfield or repowered units at existing facilities.

In the analysis, the cooling systems were grouped by in-service date by decade; pre-1950, 1960s, 1970s, 

1980s, 1990s, 2000-2011(present), and future (under construction and planned). The database included 

codes for the numerous cooling system configurations and tower types listed in Tables 1 and 2. Table 1 

presents the number of cooling systems that fall within each group. Table 2 presents the distribution of 

cooling system types that began operation within each timeframe. Table 3 collapses many of the cooling 

 

2 Out-of-scope systems include those that do not withdraw water from a surface water or withdraw less than 2 mgd.

3

For example, the Bartow plant in Florida completed a repowering project in 2009 where an entirely new combined 

cycle plant was built adjacent to the existing coal plant, which was demolished once the new system was completed. 

At this plant, the cooling system design and configuration did not change but many components such as the intake, 

pumps and piping were replaced and rerouted. Even though the project was completed in 2009, the 2011 EIA data 

for this plant continue to report an “in-service” date of 1958. Thus, it appears that a facility’s EIA survey response 

for this section of the survey won’t change from year to year, so it is unlikely the year in-service data field would be 

updated unless major changes to the cooling system design occurred.
system types into groups that would be relevant to the 316(b) regulation. The last row in Table 3 also 

shows the distribution of existing cooling systems by age.

The database also included the “Design Cooling Water Flow Rate at 100 percent Load at Intake.” The 

average design intake flow per cooling system type and timeframe is shown in Table 4. The average 

design intake values are consistent with expected values with closed-cycle being roughly an order of 

magnitude smaller than once through. 

Baseline Analysis of Closed-Cycle Cooling

Of the cooling system types reported in the database, those that are likely to comply with a requirement to 

reduce flows commensurate with a closed-cycle system include:

 Recirculating with pond/canal (impoundment)

 Recirculating with forced draft tower(s)

 Recirculating with induced draft tower(s)

 Recirculating with natural draft tower(s)

 Recirculating with forced draft hybrid tower(s) with dry cooling

 Recirculating with induced draft hybrid tower(s) with dry cooling

 Dry cooling

 Other4

The data in Table 3 clearly show a steady trend toward the use of closed-cycle cooling, especially after 

the enactment of the Clean Water Act in 1972. During the 1990’s, 84% of new cooling systems were 

likely to be compliant with a requirement for a closed-cycle recirculating system. The increase to 94% in 

the 2000’s likely reflects the influence of the Phase I 316(b) rule, which was finalized in 2001. Present 

day data indicate that 98% of new cooling systems are likely to be compliant. This indicates that the 

baseline compliance value of 50% used in the new unit cost analysis in the proposed rule5 was likely too 

conservative (low). A more reasonable value for new construction would be somewhere between 83% 

and 98%. The value of 83% represents 316(b) BPJ determinations prior to Phase I and should likely be 

the minimum for greenfield or stand-alone units at existing facilities since Phase I would not apply to 

these units. The value of 98% may be too high since the basis for this number likely includes many Phase 

I systems that are required to use closed-cycle cooling. The midpoint value of 90%6 may be a reasonable 

estimate for stand-alone or greenfield new unit baseline compliance with a closed-cycle cooling 

requirement.

Conclusion

 

4

The individual data for those systems categorized as “other” were reviewed and it was determined that none used 

surface water as the source and so were deemed compliant as well.

5 This value of 50% was based on existing facility compliance data from EPA’s 2000 technical questionnaire and 

did not incorporate recent trends. A value of 50% is consistent with the compliance estimate in this analysis for all 

existing cooling systems regardless of age, but may not be appropriate for characterizing new units.

6 This value is consistent with EPA’s assumption that 70% of new unit capacity is regulated under Phase I. Since 

closed-cycle cooling is required under Phase I, the 3% non-compliant portion (100%-97%) must only be associated 

with the 30% existing facility component. Thus, 3% (3 of 100) becomes 10% (3 of 30).
A review of the EIA data shows a clear trend towards the use of closed-cycle cooling in recent years for 

new facilities, and presumably also for new units. As a result, EPA may wish to revise the previous 

estimates of baseline compliance for new units using the more recent data. Due to the higher rate of 

expected baseline compliance, is that the estimated economic impact (and benefits) of closed-cycle 

cooling requirements for new units are much smaller than previously estimated.

References:

EIA. EIA Form 860 Annual Electric Generator Report – Instructions. Accessed January 2013.

EIA. Database Spreadsheet: “EnviroEquipY2011.xls” Accessed January 2013.

EIA. Database Spreadsheet: “LayoutY2011.xls” Accessed January 2013.
Table 1

EIA Form 860 Generator Cooling System Type Counts by In-service Date

Existing Cooling Systems Under 

Construct

ion

Planned Existing 

Total

Future 

Total

In-service Dates 1920-

1949

1950-

1959

1960-

1969

1970-

1979

1980-

1989

1990-

1999

2000-

2011

2012-

2022

2012-

2022

1920-

2011

2012-

2022

Once-through Freshwater 33 182 138 96 20 6 11 0 1 486 1

Once-through Saltwater 5 51 62 43 11 10 4 0 0 186 0

Once-through Pond/Canal 3 7 17 21 3 0 5 0 0 56 0

Recirculating with Pond/Canal 2 5 21 36 22 1 3 1 0 90 1

Recirculating with Forced Draft 

Tower(s)

2 21 26 64 59 20 116 5 5 308 10

Recirculating with Induced Draft 

Tower(s)

0 28 35 59 41 49 153 13 16 365 29

Recirculating with Natural Draft 

Tower(s)

0 0 11 34 39 6 2 3 0 92 3

Recirculating with Forced Draft 

Hybrid Tower(s) with Dry Cooling

0 0 0 0 0 0 2 1 0 2 1

Recirculating with Induced Draft 

Hybrid Tower(s) with Dry Cooling

0 0 0 0 0 0 2 0 0 2 0

Dry Cooling 0 0 0 1 2 7 42 0 12 52 12

Other 0 0 0 1 0 0 0 0 3 1 3

Total 45 294 310 355 197 99 340 23 37 1640 60
Table 2

EIA Form 860 Generator Cooling System Type Distribution by In-service Date

Existing Cooling Systems

Under 

Constructio

n

Planned Existin

g Total

Futur

e 

Total

In-service Dates 1920-

1949

1950-

1959

1960-

1969

1970-

1979

1980-

1989

1990-

1999

2000-

2011 2012-2022 2012-2022

1920-

2011

2012-

2022

Once-through Freshwater 73% 62% 45% 27% 10% 6% 3% 0% 3% 30% 2%

Once-through Saltwater 11% 17% 20% 12% 6% 10% 1% 0% 0% 11% 0%

Once-through Pond/Canal 7% 2% 5% 6% 2% 0% 1% 0% 0% 3% 0%

Recirculating with Pond/Canal 4% 2% 7% 10% 11% 1% 1% 4% 0% 5% 2%

Recirculating with Forced Draft Tower(s) 4% 7% 8% 18% 30% 20% 34% 22% 14% 19% 17%

Recirculating with Induced Draft Tower(s) 0% 10% 11% 17% 21% 49% 45% 57% 43% 22% 48%

Recirculating with Natural Draft Tower(s) 0% 0% 4% 10% 20% 6% 1% 13% 0% 6% 5%

Recirculating with Forced Draft Hybrid 

Tower(s) with Dry Cooling 0% 0% 0% 0% 0% 0% 1% 4% 0% 0% 2%

Recirculating with Induced Draft Hybrid 

Tower(s) with Dry Cooling 0% 0% 0% 0% 0% 0% 1% 0% 0% 0% 0%

Dry Cooling 0% 0% 0% 0% 1% 7% 12% 0% 32% 3% 20%

Other 0% 0% 0% 0% 0% 0% 0% 0% 8% 0% 5%

Total 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100%
Table 3

EIA Form 860 Generator Cooling System Type Distribution by In-service Date

Existing Cooling Systems

Under 

Constructio

n

Planne

d

Existin

g Total

Futur

e 

Total

In-service Dates 1920-

1949

1950-

1959

1960-

1969

1970-

1979

1980-

1989

1990-

1999

2000-

2011 2012-2022 2012-2022

1920-

2011

2012-

2022

Once-Through (including Once-through 

Pond/Canal) 91% 82% 70% 45% 17% 16% 6% 0% 3% 44% 2%

Recirculating Pond/Canal 4% 2% 7% 10% 11% 1% 1% 4% 0% 5% 2%

Recirculating Tower 4% 17% 23% 44% 71% 76% 80% 91% 57% 47% 70%

Recirculating Hybrid Tower 0% 0% 0% 0% 0% 0% 1% 4% 0% 0% 2%

Dry Cooling 0% 0% 0% 0% 1% 7% 12% 0% 32% 3% 20%

Likely 316(b) Compliant for Closed-Cycle 

Cooling1 9% 18% 30% 55% 83% 84% 94% 100% 97% 56% 98%

Cooling System Count 45 294 310 355 197 99 340 23 37 1640 60

Distribution of Cooling Systems2

3% 18% 19% 22% 12% 6% 21% 1.4% 2.3% 100% 3.7%

Includes only systems currently operating, under construction or planned in next 10 years

1

Includes Recirculating Towers, Dry Cooling and Other (all "Other" systems did not use surface water as source)

2 Distribution relative to total existing
Table 4

EIA Form 860 Generator Cooling System Average Intake Design Flow by Type and In-service Date

Existing Cooling Systems

Under 

Constructio

n

Planne

d

Existin

g Total

Futur

e 

Total

In-service Dates 1920-

1949

1950-

1959

1960-

1969

1970-

1979

1980-

1989

1990-

1999

2000-

2011 2012-2022 2012-2022

1920-

2011

2012-

2022

Units mgd mgd mgd mgd mgd mgd mgd mgd mgd mgd mgd

Once-through Freshwater 235 203 216 551 540 591 264 - 1 298 1

Once-through Saltwater 181 147 302 697 890 262 202 - - 378 -

Once-through Pond/Canal 568 303 259 676 393 - 441 - - 461 -

Recirculating with Pond/Canal 100 118 381 394 294 267 359 360 - 342 360

Recirculating with Forced Draft 

Tower(s) 4 47 38 70 51 32 24 3 2 42 2

Recirculating with Induced Draft 

Tower(s) - 27 31 60 17 12 17 9 73 25 44

Recirculating with Natural Draft 

Tower(s) - - 29 21 29 46 8 21 - 27 21

Recirculating with Forced Draft Hybrid 

Tower(s) with Dry Cooling - - - - - - 4 1 - 4 1

Recirculating with Induced Draft 

Hybrid Tower(s) with Dry Cooling - - - - - - 5 - - 5 -

Dry Cooling - - - 0 0 0 0 - 0 0 0

Other - - - 2 - - - - 4 2 4

All 235 167 204 338 168 80 37 24 32 181 29