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Site Visit Report

El Segundo Generating Station

301 Vista Del Mar

El Segundo, CA 90245

September 1, 2009

1.0 Background and Objectives

The Environmental Protection Agency (EPA) is in the process of developing 

316(b) cooling water intake structure requirements that reflect the best technology

available (BTA) for minimizing adverse environmental impact for all existing 

power plants and manufacturing facilities. As part of this process, EPA staff is 

visiting electric generators and manufacturers to better understand the cooling 

water intake structure (CWIS) technologies in use at facilities, including the sitespecific characteristics of each facility and how these affect the selection and 

performance of CWIS technologies. EPA is also visiting facilities to better 

understand cooling water use and specific issues or technologies that can affect 

316(b) compliance. EPA selected El Segundo Generating Station (El Segundo) 

for a site visit due to its ocean withdrawal location and to understand its 

repowering project in relation to cooling water needs.1

2.0 Facility Description

El Segundo occupies approximately 22 acres of a 33 acre oceanside site in the 

City of El Segundo and began operations in the 1950s. The facility is located 

immediately adjacent to Dockweiler and Manhattan State Beaches (to the west 

and north). Residential areas of the City of Manhattan Beach adjoin the 

property’s southern boundary, while a portion of a refinery lies to the east. The 

area is fairly hilly, with the facility’s switchyard located at an elevation several 

dozen feet above the generating units. See Attachment B for an aerial view.

The facility is owned by El Segundo Power (a subsidiary of NRG). The facility’s 

NPDES permit (CA0001147) expired May 10, 2005 and has been 

administratively extended pending renewal.

3.0 Electricity Generation and Transmission

El Segundo currently operates 2 natural gas-fired generating units (Units 3 and 4), 

which have a combined generating capacity of 670 MW. These units began

operation in 1964 and 1965, respectively. Units 1 and 2 were retired in 2002 and 

are being repowered. (See Section 8.0 for more information.) Units 3 and 4 have 

historically had high capacity utilization rates, but have dropped to approximately

10% in recent years. 

 

1 EPA provided a draft of this report to El Segundo but did not receive any comments from the facility.
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The switchyard is owned by Southern California Edison.

4.0 Cooling Water System and Intake Structure

The facility currently operates one offshore CWIS.2 The CWIS is comprised of a 

pipe located approximately 2600 feet offshore at a depth of 27 feet fitted with a 

velocity cap. Water is withdrawn from Santa Monica Bay through the velocity

cap (which is fitted with marine mammal exclusion bars) to a forebay onshore 

with a trash rack and 4 intake bays with one coarse mesh (5/8”) traveling screen 

each. Screens are washed twice per day or as needed, based on the head 

differential across the screen. Materials and fish removed from the screens are 

disposed in the landfill. The design through-screen velocity at the traveling 

screens is 2.0 feet per second (fps).

The design intake flow (DIF) for El Segundo is 399 million gallons per day

(mgd).

El Segundo uses both biocides and heat treatment for biofouling control. Sodium 

hypochlorite injection is used three times per day for 40 minutes each. 

Approximately every 6 weeks, the facility closes its discharge tunnel and 

recirculates the cooling water; it reaches approximately 125°F and serves to 

remove colonial organisms.

The facility’s discharge point is also offshore, at a distance of about 2100 feet.

5.0 Impingement and Entrainment Information

El Segundo conducted impingement mortality and entrainment monitoring in 

2006 and submitted a report to the state in January 2008. The sampling program 

included fish, invertebrates and crustaceans, and looked at various life stages of 

each. Two sampling stations recorded entrainment data, with ten additional 

stations serving as the source water control stations. In 12 entrainment sampling 

events (collected samples every 6 hours in a 24 hour period) representing normal 

operations, 420,000 larvae (in 66 taxa), 570,000 eggs, and 431 larval shellfish

were collected.

Impingement was recorded during 12 (one per month) events, plus an additional 4 

collections during heat treatments. During normal operations, 22 fish (9 species)

were collected, with no species being numerically dominant. During heat 

treatments, 916 fish (45 species) were collected. The total estimated annual 

impingement was 1527 fish. The study concluded that there is no adverse 

 

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For Units 3 and 4. The offshore CWIS for Units 1 and 2 is now retired, although the facility does 

continue to periodically operate one pump to move water through the intake and discharge tunnels to 

inhibit biofouling. Once repowering is complete, the intake tunnel for Units 1 and 2 will be sealed.
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environmental impact occurring as a result of the operation of the El Segundo 

facility.

6.0 Cooling Tower Feasibility

Facility representatives noted that El Segundo is located on a compact, urban site. 

As explained in Section 2.0, the facility is bordered by city streets and state 

beaches on either side. Residential areas and an adjacent refinery also limit 

available space nearby. El Segundo is also located approximately 2 miles away

from Los Angeles International Airport.

Materials provided by the facility estimated that a retrofit to wet or dry cooling 

would cost between $100-115 million.

El Segundo, along with all other coastal once-through cooling facilities in 

California, was recent evaluated by the State Water Resources Control Board as 

to the potential to retrofit the facility to closed-cycle cooling. A report3prepared 

for the California Ocean Protection Council (OPC) and State Water Board in 2008 

identified several obstacles that would likely influence the feasibility of cooling 

towers at El Segundo: the compactness of the site, the likely need for plume 

abatement, and the proximity of residential areas. Because of these obstacles, the 

report concluded that a retrofit to closed-cycle cooling was not feasible at El 

Segundo. 

7.0 Debris Handling

Facility representatives did not identify any significant problems with debris.

8.0 Repowering/Future Uses

Units 1 and 2 will be demolished and the new Units 5 and 7 (combined cycle) 

built in their place. The new units will be more efficient and flexible than the 

retired units allowing the facility to better respond to peak and load-based demand 

and have a combined generating capacity of 560 MW. The original design for the 

new units called for a once-through cooling system, but the facility amended its 

design to utilize a closed-cycle dry cooling system. Facility representatives noted 

that multiple factors influenced their decision to move towards dry cooling: 

financing for dry cooling was easier to obtain at the time of the design, they 

preferred the design over other tower designs, dry cooling would allow them to 

eliminate their NPDES permit, and dry cooling offered a greater degree of 

permitting certainty. In particular, facility representatives noted that an ongoing 

legal battle over the availability of emission credits within the South Coast Air 

Quality Management District has raised the possibility that no new projects would 

be able to obtain the necessary air permits, including facilities repowering with 

 

3 California’s Coastal Power Plants: Alternative Cooling Systems Analysis
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wet cooling towers. 4 In selecting dry cooling, El Segundo is eliminating 

approximately 200 mgd of water withdrawals.5

The repowering project is currently scheduled for completion in June 2011. 

However, facility representatives noted they are currently behind schedule for 

constructing the new units, as permitting delays (related to air emissions permits) 

have caused delays.

Facility representatives stated that they are open to the concept of repowering 

Unit 3 and 4, but that no plans are currently being made.

9.0 Cooling Ponds

There are no cooling ponds onsite.

10.0 Ownership

El Segundo is owned by NRG Energy, an investor-owned company.

11.0 316(a)

EPA did not collect any information regarding El Segundo’s thermal discharge.

12.0 Ash Handling

El Segundo does not use coal as a fuel and therefore has no ash ponds.

 

13.0 Air Emissions Controls

EPA did not collect any information regarding air emissions controls.

14.0 Additional Information

Facility representatives stated that they had not reached a definitive response for 

complying with the now-suspended 2004 Phase II rule. Facility representatives 

indicated they likely would have pursued repowering, as retrofitting cooling 

towers to a facility with a low utilization rate does not make sense.

 

4 The original cooling system was designed (and approved) to use once-through cooling, but concerns 

about the long-term risks associated with such an approach were raised within the company. Specifically, 

uncertainty regarding future 316(b) requirements (i.e., the possibility that the newly repowered units would 

be required to retrofit a cooling tower) led NRG to adapt its design. With a dry cooling system, the 

repowered units would be able to avoid many of the potential pitfalls that might accompany a retrofit wet 

cooling tower, such as additional permits that would need to be acquired. Facility representatives noted 

that a retrofit would likely have been more expensive, but did not conduct extensive studies on the 

implications for financing and feasibility for the various cooling system configurations. To better 

guarantee the future stability of the generating units, NRG opted to install dry cooling with the repowered 

units to avoid any potential future problems.

5 The estimated design flow for a once-through cooling system for the new units is 200 mgd.
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Facility representatives noted that the Long Beach power plant has also 

repowered and eliminated its once-through cooling. The existing cooling system 

had too many leaks and was replaced with dry cooling.

Attachments

Attachment A List of Attendees

Attachment B Aerial Photos

Attachment C PowerPoint presentation “El Segundo Power Redevelopment 

Project” (September 1, 2009)
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Attachment A--List of Attendees

Paul Shriner, EPA

Jan Matuszko, EPA

John Kemmerer, EPA Region IX

Tim Havey, Tetra Tech

Kelly Meadows, Tetra Tech

George Piantka, NRG

Alex Sanchez, NRG
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Attachment B--Aerial Photo

Please see DCN 10-6552A accompanying this document.

Attachment C—PowerPoint presentation “El Segundo Power Redevelopment 

Project” (September 1, 2009)

Please see DCN 10-6552B accompanying this document.