Tetra Tech, Inc.

10306 Eaton Place, Suite 340

Fairfax, VA 22030

phone 703-385-6000

fax 703-385-6007

DATE: February 28, 2011

TO: Paul Shriner, EPA

FROM: Kelly Meadows, Tetra Tech

SUBJECT: Space Constraints for Cooling Tower 

The size of the property plays an important role in determining whether a retrofit to 

cooling towers is feasible. EPA previously addressed the issue of land availability for 

cooling tower retrofits in its final effluent limitation guideline (EL

facilities (39 FR 36186, October 8, 1974). In this ELG,

determined that “28 acres per 1000 megawatts (MW) generating capacity is ample land 

on which any existing plant can construct a mechanical draft c

36190.) The ELG also required a facility to consider relocating existing uses (such as 

parking areas), alternative cooling tower designs (e.g., natural draft towers, which require 

approximately 40% less land area), or the acquisi

of whether sufficient space is available.

early 1970’s, EPA collected new 

plant properties from site visits

memo then explores the uncertainty over land availability

retrofitting wet cooling towers on an existing facility. 

This memo primarily documents those sites EPA has v

proposed section 316(b) rulemaking, and is not intended 

However, the data collected suggests

(expressed in MW) to facility acreage

 

1 The ELG required that all existing facilities with a generating capacity of 500 megawatts or more would 

be required to retrofit to closed-cycle cooling. 

2

Portions of the final ELG (including the requirements to retrofit to closed

in 1976 in Appalachian Power Co. v. Train

1977 and modified in 1982) did not include requirements for reducing cooling flow. The Fourth Circuit 

remanded the retrofit requirements on the g

requirements; the Court did not specifically address the viability of the threshold for land availability.

3

See section 6 of the preamble.

MEMORANDUM

10306 Eaton Place, Suite 340

February 28, 2011

Paul Shriner, EPA

Kelly Meadows, Tetra Tech

Space Constraints for Cooling Tower Retrofits

The size of the property plays an important role in determining whether a retrofit to 

cooling towers is feasible. EPA previously addressed the issue of land availability for 

cooling tower retrofits in its final effluent limitation guideline (ELG) for steam electric 

facilities (39 FR 36186, October 8, 1974). In this ELG, 1the Agency stated that it had 

determined that “28 acres per 1000 megawatts (MW) generating capacity is ample land 

on which any existing plant can construct a mechanical draft cooling tower.” (See 39 FR 

36190.) The ELG also required a facility to consider relocating existing uses (such as 

parking areas), alternative cooling tower designs (e.g., natural draft towers, which require 

approximately 40% less land area), or the acquisition of adjacent land in its consideration 

of whether sufficient space is available.2 Since land uses have likely changed since the 

new data on the acreage and production capacity

site visits, regional offices, draft permits, and other sources. 

memo then explores the uncertainty over land availability3and other space constraints to 

retrofitting wet cooling towers on an existing facility. 

This memo primarily documents those sites EPA has visited in support of the 2011 

proposed section 316(b) rulemaking, and is not intended to provide a statistical analysis. 

the data collected suggests that power plants where the ratio of facility

facility acreage is equal to or exceeds 160 should have ample space 

 

The ELG required that all existing facilities with a generating capacity of 500 megawatts or more would 

cycle cooling. 

Portions of the final ELG (including the requirements to retrofit to closed-cycle cooling) were re

Appalachian Power Co. v. Train, 545 F.2d 1351 (4th Cir. 1976); the subsequent ELG (issued in 

1977 and modified in 1982) did not include requirements for reducing cooling flow. The Fourth Circuit 

remanded the retrofit requirements on the grounds that EPA did not adequately consider the benefits of the 

requirements; the Court did not specifically address the viability of the threshold for land availability.

The size of the property plays an important role in determining whether a retrofit to 

cooling towers is feasible. EPA previously addressed the issue of land availability for 

G) for steam electric 

the Agency stated that it had 

determined that “28 acres per 1000 megawatts (MW) generating capacity is ample land 

ooling tower.” (See 39 FR 

36190.) The ELG also required a facility to consider relocating existing uses (such as 

parking areas), alternative cooling tower designs (e.g., natural draft towers, which require 

tion of adjacent land in its consideration 

Since land uses have likely changed since the 

acreage and production capacity of power 

and other sources. This 

and other space constraints to 

isited in support of the 2011 

statistical analysis. 

facility size 

have ample space 

The ELG required that all existing facilities with a generating capacity of 500 megawatts or more would 

cycle cooling) were remanded 

(4th Cir. 1976); the subsequent ELG (issued in 

1977 and modified in 1982) did not include requirements for reducing cooling flow. The Fourth Circuit 

rounds that EPA did not adequately consider the benefits of the 

requirements; the Court did not specifically address the viability of the threshold for land availability.
to construct retrofit cooling towers.4

 EPA bases this ratio on the observation that 

approximately 95 percent of the 47 sites with a ratio of 160 and above would have 

sufficient acreage to retrofit mechanical draft5cooling towers. For the 25 observed sites 

with a ratio less than 160 MW per 1000 acres, as many as 20 percent of the facilities 

would likely be space constrained. This memo documents only the observations of each 

site visit team, and does not reflect a detailed engineering feasibility assessment for each 

site. For example, the configuration of the existing facility, topography, existing 

structures or uses, neighboring properties and uses, and other site-specific details may

constrain the potential locations for siting cooling towers. 

The table below summarizes the data collected (see Attachment A). EPA obtained most 

of the acreage data from facility’s stated property boundaries during site visits. Other site 

data was provided from facility permit applications, by EPA regions and state permitting 

authorities, or other site reports. This acreage includes the power block itself, 

transmission yards, parking areas, coal piles, and all other existing equipment or land 

uses.6 Next, the land area was normalized by dividing the acres by the facility’s 

generating capacity.

7

 In doing so, a ratio of acres per 1000 MW was generated for all 

sites, thereby allowing for a comparison of facilities of all sizes and types.

Facility Type Range 

(acres/1000 MW)

Average Ratio

(acres/1000 MW)

Median Ratio

(acres/1000 MW)

All Site Visit 

Facilities

7 – 6216 858 350

Sites With Retrofit 

Cooling Towers

160 - 6216 2235 1920

Sites With NonRetrofit Cooling 

Towers

83 – 5657 2318 1266

EPA also collected data on the facility size of plants with existing closed-cycle cooling 

systems (i.e. the cooling towers were not a retrofit). EPA was able (through basic 

internet searches) to find information on facility acreage for an additional 25 facilities 

with either partial or full closed-cycle systems. 

Facility Type Range 

(acres/1000 MW)

Average Ratio

(acres/1000 MW)

Median Ratio

(acres/1000 MW)

 

4 The analysis of acreage per 1000 MW only addresses electric generating facilities, as manufacturers may 

not generate any electricity or are otherwise engaged in other activities that will affect the applicability of 

such a ratio. 

5

Only mechanical draft towers were considered; natural draft towers would generally occupy a smaller 

footprint of acreage, and may pose additional flexibility if the site were required to retrofit to closed-cycle 

cooling.

6 EPA recognizes that some elements of the power plant may be owned by other parts of the facility’s 

parent firm (e.g., the transmission yard is sometimes owned by a sister company). EPA considers these 

areas to also be part of the facility’s property, as it is still under the parent firm’s control.

7 As stated in the 1974 ELG, [t]he size of the evaporative cooling tower is related to the generating capacity 

of the unit.” (39 FR 36189)
Partial CCRS 202 – 16,667 3077 1304

Closed-Cycle 

Cooling

117 – 5654 1285 850

Case Studies

Two facilities are worth discussing in greater detail as case studies for space constraints 

to cooling tower retrofits.

Brayton Point: Brayton Point Station in Massachusetts is currently constructing two

natural draft cooling towers as part of a closed-cycle cooling system retrofit. EPA 

Region I and Dominion Energy conducted thorough analyses on all aspects of the retrofit 

before Dominion Energy determined the final design. Space constraints at the site was 

not identified as a feasibility issue in retrofitting to cooling towers. In this analysis, 

Brayton Point’s ratio was 160 acres/1000 MW.

McDonough: McDonough Power Plant in Georgia converted an older coal-fired plant to 

closed-cycle cooling (with a wet cooling tower) in 2008 as part of a broader plan to 

repower the site to use multiple natural gas combined cycle generating units. To install 

the towers, Georgia Power demolished the adjacent Atkinson Plant to create space to 

construct the cooling towers. Georgia Power also faced a number of challenges in 

retrofitting the towers, including relocating maintenance buildings, burying cooling water 

pipes, and adding pump stations.8 According to data collected during the site visit, the 

ratio for McDonough (using the current coal-fired generating capacity and the original 

dimensions of the site) is 612 acres/1000 MW. However, given the construction of the 

two new combined cycle units on other parts of the property, the effective acreage of the 

McDonough site could be as little as 80 acres, making the facility’s ratio 163.

9

 

8

See EPA’s site visit report for this facility (DCN 10-6536) for a complete description.

9 Using aerial photos of the site, the footprint of the two new combined cycle units and the existing coal 

pile occupy a significant portion of the site. By approximating the remaining area that would be dedicated 

to the existing generating unit (and eventually the final combined cycle unit), a polygon approximately 

3500 feet by 1000 feet can be identified, resulting in an area of 80 acres.