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Site Visit Report 

San Onofre Nuclear Generating Station (SONGS) 

14300 Mesa Road 

San Clemente, CA 92674 

September 2, 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. San Onofre Nuclear Generating Station (SONGS) was 

selected for a site visit due to its ocean withdrawal location, its fish return system, 

and because it generates a significant amount of power (as a percentage of the 

total) for the state of California. 

2.0 Facility Description 

SONGS is located on an oceanfront site near the city of San Clemente (between 

Los Angeles and San Diego) and began operations in 1968. The facility is located 

on land leased from the U.S. Marine Corps’ Camp Pendleton. SONGS is divided 

into two areas; the beachside portion (where the reactors and other power 

generation equipment are located) is approximately 84 acres,1

 while the upland 

portion (referred to as the Mesa Complex, across the freeway and home to 

administrative operations) is approximately 130 acres.2

 The facility is principally 

owned by Southern California Edison (SCE)3

 and employs approximately 3200 

workers. The facility’s NPDES permit (CA0108181) expires May 11, 2010 and 

facility representatives have begun preparing renewal application materials. 

 

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 Facility representatives stated that SONGS is the most compact nuclear power plant site in the U.S. By 

comparison, the Fort Calhoun Station, the smallest nuclear facility by rated output at 482 MW is located on 

660 acres of land, near Omaha, Nebraska. Source: 

http://www.nei.org/resourcesandstats/nuclear_statistics/usnuclearpowerplants 2

 The facility’s beachside main portion is located south of San Onofre State Beach alongside the Pacific 

Ocean. The San Diego Freeway (Interstate 5) and a high speed railway parallels the eastern boundary and 

separates the beachside main portion from the upland portion. 3

 SCE owns a 78.21% stake in the facility. 
2

3.0 Electricity Generation and Transmission 

SONGS operates two nuclear reactors (Units 2 and 3) with a total generating 

capacity of 2254 MW.4

 The facility is a baseload generator, with a capacity 

utilization rate (CUR) of 83% in 2006.5

Routine refueling outages occur approximately every 18 months. The facility has 

completed its Unit 2 steam generator replacement, which resulted in a 197 day 

outage. The process involved removal of portions of the containment wall of the 

reactor. The same procedure for Unit 3 is expected to occur this fall; however, 

the outage for Unit 3 is expected to last only 97 days. 

 

4.0 Cooling Water System and Intake Structure 

SONGS operates two submerged offshore intakes (one for each unit) to withdraw 

once-through cooling water from the Pacific Ocean.6

 Each intake pipe is fitted 

with a velocity cap7 and is located approximately 3200 feet offshore at a depth of 

32 feet. The through-screen velocity at the velocity cap is approximately 1.5 feet 

per second (fps). After water enters the intakes, it is then transported to a forebay 

onshore. The forebay is divided into two identical halves, one for each generating 

unit. 

Vanes and louvers angled at 30 degrees to incoming flow change the water 

velocity and guide fish to a quiet zone at the inland end of the forebay, where fish 

avoid the traveling screens and instead are collected in a fish handling chamber 

and periodically returned to the ocean via a fish elevator. The elevator is operated 

once per shift8

 and returns fish to a conduit back to the ocean approximately 1900 

feet offshore. Facility representatives noted that this system results in high 

survivability and that the survival rate varies depending on the species; a study in 

2006-2007 demonstrated that 71.6% of all fishes entrained were returned to the 

ocean via the Fish Return System (CDS 2008). 

The cooling water and remaining fish and debris then pass through a set of bar 

racks and a pair of vertical traveling screens; water first passes through the 1” 

 

4

 Unit 1 was retired in 1992 and is decommissioned. Units 2 and 3 began operations in 1983 and 1984, 

respectively. 

5

 The facility’s CUR was 90% in the late 1990s. It provides nearly 20% of the electricity to southern 

California. 

6

 The intake and discharge tunnels for Unit 1 still exist, but have been capped. The NPDES permit for this 

unit has been terminated. 

7

 The facility has not installed marine mammal exclusion bars that are found at other velocity caps. Facility 

representatives stated that obtaining approval to install them takes considerable time and they still have 

concerns over clogging from kelp. Approximately 30 Pacific harbor seals and California sea lions per year 

reach the forebay, where they are captured and returned to the ocean. 8

 The elevator is operated at a different time during each shift to discourage predation at the fish return. 
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mesh screens and then the 3/8” mesh screens.9 Screens are rotated manually or 

based on a pressure differential and are cleaned by a high pressure spray. Debris 

(including any impinged fish) is collected in a dumpster for disposal at a landfill. 

The through-screen velocity at the traveling screens is approximately 2.8 fps. 

Each unit has four circulating pumps, each rated for 298 million gallons per day 

(mgd); the total design intake flow (DIF) for SONGS is 2384 mgd.10 The 

facility’s average actual intake flow (AIF) is approximately 2400 mgd. The delta 

T for the condenser is typically 19-20oF. 

Facility representatives stated that the CWIS design is unique and was an 

expensive undertaking when the facility was built (approximately $200 million). 

In fact, the reactors are built adjacent to the CWIS. 

Unit 2’s discharge is located 6300 feet offshore at a depth of 50 feet; Unit 3’s 

discharge is 8600 feet offshore at a similar depth. Each generating unit has its 

own discharge pipe with 63 diffusers. 

5.0 Impingement and Entrainment Information 

SONGS has conducted studies of its velocity cap and facility representatives 

stated that, in conjunction with the fish elevator, impingement mortality has been 

reduced by 97%. Facility representatives stated that the velocity cap reduces the 

number of fish drawn into the intake structure by at least 90%. Initial studies of 

the fish elevator suggest that fish exhibit survival rates of 75-96% and further 

studies (spanning 11 years) indicated an average survival rate of 70%. Facility 

representatives noted that daily losses due to impingement are estimated to be 

0.15 tons while those due to sport fishing are estimated to be 12.4 tons. 

The facility also submitted a Comprehensive Demonstration Study to the San 

Diego Regional Water Quality Control Board, as required by the now-suspended 

2004 Phase II rule. Facility representatives stated that biological studies represent 

a snapshot of ambient conditions at the offshore intake location and are compared 

to measurements taken near the shore. Typically, spring is the season with the 

highest abundance of entrainable organisms, i.e., eggs and larvae. 

Facility representatives stated that the offshore sardine population has rebounded 

significantly with the establishment of state fishing regulations. A study in 2005-

2006 indicated a large difference in impinged fish at one intake (as compared to 

the other). In all, 3 species represent 97% of the fish impinged at both units. 

 

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 There are six pairs of screens in each half of the CWIS. Facility representatives noted that the first set of 

screens is constructed of a composite material and the second set is stainless steel. They added that 

improvements to the chain and bearings have resulted in these screens being in place for 13 years. 10 The facility’s service water system (which provides cooling for the auxiliary reactor systems) is 

withdrawn from the circulating water flow. 
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6.0 Cooling Tower Feasibility 

Facility representatives have studied closed-cycle cooling in detail, but maintain 

that it is not an appropriate solution for SONGS. Facility representatives stated 

that the facility could face significant obstacles in retrofitting to closed-cycle 

cooling, including finding a suitable location,11 obtaining PM10 offsets,12

obtaining construction permits, gaining approval from the Marine Corps to build 

towers,13 and to obtain permission from state regulators for a $3.12 billion 

expenditure.14 

An independent third-party feasibility study conducted by Enercon Services, Inc. 

of Atlanta, GA, concluded that the only space available for cooling towers would 

be on the Mesa complex. They noted substantial engineering challenges 

associated with cooling towers at the Mesa complex, including massive earth 

moving projects for the large piping required beneath the highway, building 

relocation, potential for flooding,15 an energy penalty of 191 MW, potential 

condenser replacement, and significant plume and visual impacts. Facility 

representatives also noted potential impacts to activities at Camp Pendleton, such 

as impacts to training areas, plume effects on flight operations, salt drift in 

residential areas, and noise and aesthetic impacts. 

As part of its process developing a statewide OTC policy, the California State 

Water Resources Control Board recently evaluated all coastal OTC facilities, 

including SONGS, to determine the feasibility of retrofitting each location with 

closed-cycle cooling. A survey report of all coastal facilities prepared for the CA 

Ocean Protection Council and State Water Board in 200816 concluded that, while 

a retrofit was technically feasible at SONGS, significant obstacles would have to 

be overcome. The report noted the site’s compact size and proximity to sensitive 

coastal habitats and high use transit corridors as factors that would likely require 

(1) additional consultation with resource agencies to secure the necessary permits 

 

11 Facility representatives stated that the towers could not be located at the beach site; the parking lots and 

other open spaces are not large enough for plume abated towers, which facility representatives noted need 

more space in order to prevent recirculation of the plume into the towers. In addition, facility 

representatives stated that the towers likely cannot be built near the state beaches and that spent fuel storage 

activities are required to remain within the power block. 

12 Enercon estimated that the towers would emit 827 tons of PM10 per year, but only 150 tons per year are 

available in the permitting process. 

13 Facility representatives noted that the Marine Corps has committed land in the vicinity of SONGS as 

natural habitat and green space; close-cycle cooling may impact the ability to continue to designate that 

space as natural. 

14 Facility representatives stated that they expect a 5% rate increase and a 17 month outage, adding that 

Diablo Canyon would likely cost approximately $4 billion. They noted that SCE recently struggled to gain 

approval for $700 million turbine improvements, which serve to add generating capacity; cooling towers 

would remove capacity from the grid. 

15 Facility representatives stated that, if the towers were built at the Mesa Complex, they would be at a 

higher elevation; should the facility lose power, the water in the towers would flow downhill, possibly 

flooding the plant. 

16 Tetra Tech, Inc. California’s Coastal Power Plants: Alternative Cooling Systems Analysis. February 

2008. This report was prepared under contract to the CA Ocean Protection Council. 
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to construct towers in sensitive areas, and (2) plume-abated towers to reduce 

potential safety hazards on nearby freeways. If the first condition could not be 

met, the report considered a Unit 3 retrofit infeasible due to lack of space; plume 

abated towers were still considered feasible for Unit 2, however. 

The 2008 report did not evaluate siting towers at the Mesa Complex in detail, 

citing the difficulty in constructing four 12-ft diameter tunnels beneath the 

railroad and the San Diego Freeway. Cost estimates were not developed for a 

Mesa installation, although the report notes that they would likely be significantly 

higher than a beachside installation. 

7.0 Debris Handling 

Facility representatives did not identify any significant problems with debris. 

They estimated that the facility disposes roughly 1 ton of seaweed and kelp (wet 

weight) per day. 

8.0 Repowering/Future Uses 

Facility representatives were not aware of any plans for repowering or adding new 

generating units. 

9.0 Cooling Ponds 

 

There are no cooling ponds onsite. 

10.0 Ownership 

SONGS is owned by Southern California Edison, an investor-owned company 

and subsidiary of Edison International. SONGS is jointly owned by SCE 

(78.21%), San Diego Gas & Electric (20%), and the city of Riverside (1.79%), but 

SCE maintains full operating management of SONGS. 

11.0 316(a) 

As noted in Section 4.0 above, SONGS uses an offshore discharge with diffusers. 

The discharge is designed to meet California’s thermal plan, which allows no 

more than a 4oF change within 1000 feet. Facility representatives noted that 

typical temperature changes are 1-1.5oF and that many other power plants in 

California do not meet the state standard. 

12.0 Ash Handling 

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

 
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13.0 Air Emissions Controls 

EPA did not collect any information regarding air emissions controls. 

14.0 Additional Information 

Facility representatives discussed intake technologies, as outlined in the 2008 

CDS, that have been considered for reducing impingement and entrainment at 

SONGS.17 Technologies that were considered but deemed infeasible by the 

facility’s analysis included variable speed pumps, an aquatic filter barrier, and 

relocation of the CWIS. SONGS determined that fine mesh modified or 

cylindrical wedgewire screens could be feasible (based on many assumptions; 

refer to CDS 2008), but would likely fall short of the performance criteria in the 

now suspended Phase II 316(b) rule. SONGS indicated the extensive footprint 

associated with wedgewire screens would likely have a substantial impact on 

offshore habitat. 

Facility representatives noted that spent fuel storage facilities (for all three units) 

are being constructed on the former site of Unit 1. 

Facility representatives stated that, as a preventive maintenance measure for 

biofouling, the facility conducts heat treatments where the direction of flow is 

reversed and heated effluent is discharged through the intake pipes.18 Prior to the 

heat treatment, operators slowly raise the temperature within the piping, herding 

fish towards the fish elevator; frequent operation of the elevator returns the fish to 

the ocean. Facility representatives noted that they often encounter large numbers 

of subadult and adult fishes during these events, especially in summer. They 

added that operators see resident fish in the forebay for weeks at a time. 

Facility representatives noted that SONGS is critical to the future of California’s 

energy needs, including plans for greenhouse gas emission reductions statewide. 

They noted that it is difficult to integrate renewable energy sources to the grid and 

noted that state analyses of grid reliability may be changing. They also noted that 

the wildfires in 2009 have delayed permitting for renewable energy projects. 

They added that the proposed California rule for closed-cycle cooling would 

require them to begin retrofitting in 2020, when state greenhouse gas goals will 

take effect, limiting the state’s ability to meet those goals. 

Facility representatives stated that the California Coastal Commission (CCC) has 

recently stated that, in its judgment, mitigation measures would be sufficient to 

qualify as “best technology available” for SONGS. 

Facility representatives stated that, under the 2004 Phase II rule, they were likely 

to pursue the cost-benefit test or restoration to meet the rule requirements. 

 

17 See Attachment D for detailed information on each technology. 18 Heat treatments are as frequent as every 6 weeks in summer, the high biofouling season. 
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Attachments 

Attachment A List of Attendees 

Attachment B Aerial Photos 

Attachment C PowerPoint Presentation “The Once-Through Cooling Rule for 

Existing Power Plants” September 2, 2009 

Attachment D Comprehensive Demonstration Study for Southern California 

Edison’s San Onofre Nuclear Generating Station 

 
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Attachment A--List of Attendees 

Paul Shriner, EPA 

Jan Matuszko, EPA 

Tim Havey, Tetra Tech 

Kelly Meadows, Tetra Tech 

David Asti, Southern California Edison 

Patrick Tennant, Southern California Edison 

Robert Heckler, Southern California Edison 

Robert Keller, Southern California Edison 
Copyrighted page/s removed. Copyrighted 

material is not available in Regulations.gov since 

it may not be reproduced without consent of the 

copyright holder. 

Please contact the EPA Docket Center, Public 

Reading Room to view this document. 

Address: 1301 Constitution Ave, NW 

Room 3334 

Washington, DC 20004 

Telephone: 202-566-1744 

Fax: 202-566-9744 

Email: docket-customerservice@epa.gov
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Attachment C--PowerPoint Presentation 

Please see the attached materials. 

Attachment D—Comprehensive Demonstration Study for Southern California 

Edison’s San Onofre Nuclear Generating Station 

Please see the attached materials.