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Site Visit Report

Scattergood Generating Station

12700 Vista Del Mar

Playa Del Rey, CA 90203

August 31, 2009 (revised August 16, 2013)

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 Scattergood Generating Station (SGS) for a site 

visit due to its location on the Pacific Ocean and its use of an offshore intake 

structure fitted with a velocity cap.

2.0 Facility Description

SGS is a natural gas–fired steam electric generating facility located in the Playa 

del Rey section of the City of Los Angeles and owned and operated by the City of 

Los Angeles Department of Water and Power (LADWP). The facility occupies 

approximately 56 acres of an industrially zoned site opposite Dockweiler State 

Beach and Santa Monica Bay. The city’s Hyperion Wastewater Treatment Plant 

lies adjacent to the facility’s northern property line, with Grand Avenue bordering 

to the south (industrial area). Residential neighborhoods in the City of El 

Segundo and Los Angeles abut the eastern and northeastern boundaries (see 

Attachment B). In addition, SGS is located approximately one mile south of the 

southern-most runway at Los Angeles Airport.

Elevations at the site vary significantly. The three generating units are situated at 

approximately 35 ft above sea level (asl) along the facility’s western boundary

with Vista del Mar. Water treatment ponds and tanks, parking areas, and smaller 

maintenance buildings are also located at this level. Immediately east of the 

generating units, the property rises sharply to approximately 100 ft asl, then 

gradually rises to 155 feet at the eastern property line. This upper portion is 

occupied by the switchyard, storage tanks, and two small cooling towers that 

provide bearing cooling water using potable water.

Wastewater discharges to and water withdrawals from Santa Monica Bay (Pacific 

Ocean) are covered under NPDES Permit No. CA0000370, which is administered 

at the state level by a regional water board. Order No. 00-083, issued by the Los 

Angeles Regional Water Board, expired on May 10, 2005 but has been 
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administratively continued to the present. The facility had been previously 

notified that a reissued permit was delayed pending the outcome of the State 

Water Board’s ongoing once-through cooling policy development. At the time of 

EPA’s site visit it was unclear when the NPDES permit would be reissued. 

Power generation began in 1958 with the commissioning of Unit 1. Unit 2 

followed in 1959 while Unit 3 was commissioned in 1974. All units remain 

available for service.

SGS has a single two to three week outage annually and an eight to ten week 

outage every few years for major projects.

3.0 Electricity Generation and Transmission

SGS currently operates three conventional steam turbine units (Unit 1, Unit 2, and 

Unit 3) with a combined boilerplate generating capacity of 820 MW (Table 1). 

Facility representatives noted that the capacity utilization rate (CUR) at SGS has 

consistently trended downward over recent years as more modern and efficient 

sources have come online in the region, including an expanded renewable 

portfolio to meet state greenhouse gas objectives. However, depending upon 

federal and state climate legislation, greater dependence on these local plants for 

base load energy supply and the balancing of new intermittent renewable 

resources may be necessary if LADWP is required to undertake an early

divestiture of its coal resources.

Table 1 – SGS Rated Capacity

Unit Rated capacity

(MW) 2008 CUR

Unit 1 180 31%

Unit 2 180 15%

Unit 3 460 18%

SGS total 820 20%

Units 1 and 2 are conventional natural gas while Unit 3 is a supercritical natural 

gas unit. Energy efficiencies for SGS’s three natural-gas fired units are typical for 

units of this type and age. Under peak conditions, Units 1 and 2 can operate at 

approximate efficiencies of 33% (9,500 BTU/kWh) while Unit 3 is slightly more 

efficient at 37% (9,200 BTU/kWh).

LADWP representatives noted that capacity utilization rates are an inexact metric 

for determining a particular facility’s importance to the overall system. Although 

SGS’s CUR is relatively low, it occupies a critical position in LADWP’s overall 

generation and transmission plans during peak periods. The existing transmission 

system is limited in its ability to move electricity between the northern and 

southern sections of LADWP’s service areas during high demand periods. The 

physical location of SGS, along with LADWP’s other coastal units, enables 

LADWP to maintain a proper balance in the system without compromising 
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service. This is particularly notable since LADWP is its own balancing authority

and as mentioned in Section 10 of this report, as a vertically integrated utility 

responsible for its own generation, transmission, and distribution of electricity, 

does not rely on the energy market for power purchases to supply its energy

needs. Therefore, the role of its coastal plants, serve a critical function in 

providing local resource adequacy, reliability, and system stability.

4.0 Cooling Water System and Intake Structure

Units 1-3 use ocean water for condenser cooling in a single-pass configuration 

(“once-through cooling”). SGS operates a single combined intake structure to 

serve all three units; water is divided after secondary screening to dedicated 

tunnels to each unit’s condenser. Water is withdrawn from Santa Monica Bay

through an intake located approximately 1,600 feet from shoreline, terminating at 

a depth of approximately 29 feet. The intake pipe rises 13 feet above the sea floor 

and is fitted with a circular concrete velocity cap 32 feet in diameter (Figure 1). 

There is a 5 foot vertical gap between the top of the intake pipe and the bottom of 

the velocity cap. In February 2009, SGS installed vertical exclusion bars spaced 9 

inches apart on the velocity cap to reduce entrapment of large organisms (sea 

lions, sea turtles, etc.). Facility representatives indicated that the modification has 

noticeably reduced entrapment between the intake riser and the forebay. 

Figure 1 – Offshore Intake and Velocity Cap

The intake structure’s onshore portion consists of 8 screen bays arranged in a 60° 

arc that draw water from a common forebay. Unit 3 is served by four of the 

screen bays, with 2 each dedicated to Units 1&2. Primary screening is achieved 
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with vertical bar racks spaced 5 inches apart (4-5/8 inch opening) to remove large 

debris. Secondary screens for smaller debris consist of vertical traveling screens 

with 3/8-inch by 3/4-inch mesh openings (Figure 2). Screens are rotated once 

every 8 hours, at a minimum, and washed with a high pressure spray to remove 

collected debris, which is deposited in collection baskets for disposal in a landfill.

Figure 2 – Onshore Intake Structure
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Estimated intake velocities were calculated using the maximum intake flow and 

total screen area at MLLW: 

 1.5 fps at velocity cap opening

 6.8 fps in the intake pipe

 0.6 fps approach to screens for Units 1&2

 0.7 fps approach to screens for Unit 3

Four circulating water pumps, each rated at 39,000 gpm (56 mgd), serve Units 

1&2. Four additional pumps serve Unit 3, with each pump rated at 47,000 gpm 

(68 mgd). The SGS design intake flow (DIF) is 344,000 gpm, or 495 mgd, 

although the peak intake capacity is used infrequently throughout the year. Data 

provided by SGS representatives shows the average daily intake flows from 2005 

through 2008 (Table 2).

Table 2 – Average Annual Intake Flows

Year Average Annual Intake Flow (mgd) Percentage of DIF

2005 294 59

2006 316 64

2007 271 55

2008 315 64

A direct correlation between flow and generating capacity utilization cannot be 

easily made since generating CUR do not account for startup/shutdown periods, 

nor do they account for “hot standby” periods during which units are held in a 

near-ready state without generating electricity but still require cooling water 

withdrawals. 

SGS conducts periodic heat treatments (approx. every 8 weeks) to control 

biofouling (e.g., mussel growth) in the cooling water system. During heat 

treatment control gates on the intake and discharge tunnels are closed while a 

bypass gate is opened allowing all water to recirculate through the system until 

the temperature has reached 115° F and has circulated for 100 minutes. 

Biofouling is also controlled through periodic chlorine (sodium hypochlorite) 

injections to the intake flow. Chlorination for each unit occurs for 40 minutes 

once for each shift (3 times per day).

5.0 Impingement and Entrainment Information

Following the adoption of the Phase II rule, SGS initiated compliance activities 

by submitting a Proposal for Information Collection (PIC) in October 2005 that 

outlined plans to conduct a source water characterization study. Impingement and 

entrainment technologies would also be evaluated for their potential use at the 

site. The PIC identified fine-mesh traveling screens, cylindrical wedgewire 

screens, operational measures, and restoration as technologies that might offer 
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some benefit to SGS. These evaluations were not completed, however, due to the 

suspension of the Phase II rule. 

Facility representatives noted that LADWP evaluated the feasibility of using 

treated wastewater from the Hyperion facility as a replacement for ocean water at 

SGS, but concluded this water source was insufficient to meet cooling water 

needs. In addition, this alternate water source may be limited in the future 

because the state is advocating water reclamation, thereby reducing opportunities 

for reclaimed water from POTWs. Secondary issues included the elevated 

wastewater temperature coming from the Hyperion facility an the presence of 

ammonia which would be detrimental to the copper/nickel alloy condenser tubes.

At the direction of the Regional Water Board, SGS conducted a source water 

baseline characterization study during 2006 to determine the composition and 

abundance of all life stages of fish and shellfish that might be influenced by the 

intake structure. The study documented entrainable organisms in the vicinity of 

the intake and near the shoreline, but did not attempt to quantify any entrainment 

reductions. SGS collected monthly sampling every six hours in a 24 hour period 

at from ten source water stations located up and down the coast. SGS also 

conducted impingement and entrainment sampling as part of this study. They

collected weekly (four in a 24 hour period) impingement samples at the traveling 

screens1and entrainment samples from a single entrainment station in the 

immediate proximity of the CWIS (within 50-100 meters). The study was 

published in November 2007.

SGS has twice evaluated the effectiveness of the intake structure’s velocity cap in 

reducing impingement. Following a major storm in 1970 that destroyed the 

velocity cap, SGS operated for 4 years without the cap. Comparisons between the 

protected and unprotected system showed significant impingement reductions 

with the velocity cap in place. 

More recently, SGS conducted a study over four months during the winter of 

2007-08. During the study period, intake and discharge flows were reversed (i.e., 

the intake became the discharge and vice versa) such that the new “intake” was 

unprotected. Apart from the velocity cap, the principal difference between the 

intake and discharge is the distance from shore (1,600 vs 1,200 feet). At this 

location, however, the sea floor slopes gently away from shoreline and translates 

to a depth disparity of only a few feet. Thus, the species composition and 

abundance are substantially similar at each location. The study reported 

impingement reductions of more than 97 percent based on abundance, and 95 

percent based on biomass. A single species, pacific sardines, accounted for over 

94% of fish abundance.

Entrainment has not been studied in detail at SGS. The velocity cap study did not 

evaluate any potential entrainment reduction that might be achieved by the intake 

structure’s location at a point offshore. 

 

1 The impingement samples do not represent the intake location as the traveling screens are located after the 

long intake pipe. 
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6.0 Cooling Tower Feasibility

Facility representatives noted that the feasibility of cooling towers at the SGS 

location as been considered at different points, whether as part of a repowering 

project or to retrofit one or all three of the existing units. SGS has not conducted 

a formal cost and engineering feasibility analysis, however. 

A report prepared for the California Ocean Protection Council (OPC) and State 

Water Board in 2008 identified several obstacles that would influence the 

feasibility of cooling towers at the SGS location. Available space at the facility is 

limited and cooling tower placement would be complicated by the disparity in 

elevations. Siting cooling towers to either side of the generating units at the 30 

foot elevation would be difficult given the limited space, the presence of other 

structures (treatment ponds/tank) and potential air circulation interference due to a 

tower’s proximity to the steep slope east and south of the generating units. 

A more likely scenario would place cooling towers on the upper portion of the 

facility at the 100 foot elevation where the current, but significantly smaller

cooling towers for just the bearing cooling water, are located. Multiple towers 

could be configured in this area, although the elevation difference between the 

towers and condensers would require larger capacity circulating water pumps and 

might require modifications to the condensers to withstand higher pressures. 

Towers at this location would present a greater visible impact and might 

contribute to drift deposition on the adjacent switchyard. 

The potential for a large visible plume would likely require mitigation for at least 

a portion of the year. SGS’s proximity to the southernmost runway at LAX and to 

residential neighborhoods in El Segundo would seem to indicate that plume 

abatement technologies would be required. Noise abatement measures, such as 

low-noise fans or fan deck barriers would also be required to comply with local 

ordinances. The 2008 OPC study considered these obstacles but was able to 

configure cooling towers for all three units on the upper portion with plume and 

noise abatement technologies included. The initial capital cost for these towers 

was estimated at $160.4 million, excluding long-term costs such as operation and 

maintenance and energy penalty costs.

During the site visit, facility representatives cited many of the same obstacles as 

potential reasons why cooling towers were infeasible at the site. Space limitations 

and conflicts with local ordinances were the primary reasons why SGS does not 

consider cooling towers a practical alternative. Representatives noted that likely

local opposition to cooling towers is not reflected in local building and noise 

ordinances and would be a major concern. Other concerns that were not reflected 

in the OPC study were: (1) while the report suggests relocation of critical, integral 

site equipment (e.g. ammonia storage tanks for NOx compliance, or the switch 

yard) their costs and the associated outage time (e.g. replacement power costs) 

were not captured; (2) OPC concluded relocation of the switch yard was feasible, 

but is considered infeasible by LADWP for all sites evaluated; (3) the suggested 

siting location for the cooling towers was characterized as sufficiently large (with 

equipment relocations), however, it resulted in a less than desirable configuration 
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(roughly perpendicular to prevailing winds); and (4) the study assumes that the 

new towers could replace the need for the existing cooling towers for cooling the 

bearing (which would be required to be demolished to make room), but 

recognized that it was unknown whether the use of salt water for these systems 

could be tolerated. Most significantly, however, representatives noted that 

retrofitting the existing once-through cooling systems with cooling towers made 

little economic sense given the age and capacity utilization of each unit. In

addition, because SGS is a municipal utility, retrofit funds would require a rate 

increase and bond issuance that would have to be approved by the Los Angeles 

City Council. See Section 10.0.

7.0 Debris Handling

Debris is not a significant issue at SGS due to the intake’s deep offshore location.

Any debris captured on the bar racks or traveling screens is disposed of in a 

landfill. 

8.0 Repowering/Future Uses

LADWP is considering the possibility of repowering Units 1 and 2 or Unit 3 by

2015. The state’s final once-through cooling policy will likely influence the 

options selected for any repower project.

9.0 Cooling Ponds

SGS does not use cooling ponds for condenser cooling.

10.0 Ownership

LADWP is the largest municipally owned utility in the country with a service 

population of approximately 4 million people. LADWP maintains a total 

generating capacity of approximately 7,200 MW from diverse portfolio of fossil, 

hydroelectric, renewable, and nuclear units. SGS is one of three LADWP-owned 

facilities on the California coast that continues to use once-through cooling 

(together with the Harbor and Haynes Generating Stations). 

As a vertically integrated utility, LADWP owns and operates the generating, 

transmission and distribution systems that provide electricity to a dedicated 

customer base. This transmission system is not limited to the City of Los 

Angeles, but extends into Nevada, Utah, and Arizona. The system is used to 

import power to all locations (LADWP owned and power exchanges with other 

utilities). This differs from many investor owned utilities, such as Pacific Gas & 

Electric or Southern California Edison, which must rely on the open market to 

procure a significant portion of their electricity needs. 

LADWP must obtain approval from the Los Angeles City Council to implement 

any electricity rate increases. LADWP is in the process of developing a new IRP 

and is currently soliciting input from the public on this new guidance document. 
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This new 2010 IRP will help set the course that LADWP will take in determining 

the best path to take for repowering the existing OTC facilities.2

11.0 316(a)

Thermal discharges to surface waters are governed by the state’s Thermal Plan 

(1972), which creates separate requirements for new and existing thermal 

discharges to ocean waters. As an existing thermal discharger, SGS is subject to 

the Thermal Plan’s narrative requirement that any thermal discharge must ensure 

protection of identified beneficial uses. This requirement is incorporated into the 

existing permit as a temperature limitation of no more than 100° F during normal 

operation and 135° F during heat treatments. The facility does not have a 316(a) 

variance for thermal discharges and has complied with the existing limitation 

during its most recent permit cycle. 

12.0 Ash Handling

SGS does not generate any ash.

13.0 Air Emissions Controls

Each unit at SGS employs selective catalytic reduction to minimize NOx 

emissions.

14.0 Additional Information

Facility representatives noted that an ongoing legal battle over the availability of 

emission credits within the South Coast Air Quality Management District have 

raised the possibility that no new projects would be able to obtain the necessary

air permits. This would include facilities retrofitted with wet cooling towers. 

SGS’s current NPDES permit, adopted in 2000, does not contain any numeric or 

narrative limitations regarding impingement or entrainment due to cooling water 

withdrawals. The permit carries over findings from previous permits that 

essentially concluded the SGS cooling water system represented the “best 

technology available” for compliance with 316(b). Although these determinations 

were made prior to the adoption of the state policy on once-through cooling, 

future studies will determine whether this statement is still accurate or whether 

other technologies are available that would represent “best technology available” 

with costs that can be borne by industry. SGS is required to conduct semi-annual 

impingement monitoring coinciding with scheduled heat treatments. 

In addition to once-through cooling water, SGS discharges a small volume of 

wastewater from several low volume waste streams. These low volume wastes 

consist of cooling tower blowdown, boiler blowdown, floor drains, and settling 

basin discharges, and are commingled with once-through cooling water prior to 

 

2 At the site visit, facility representatives indicated that earlier drafts of the report included costs of between 

$35 and 310 million for cooling towers at Scattergood.
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discharge through the main outfall. All wastewater is discharged to Santa Monica 

Bay through a submerged conduit terminating at a point 1,200 from shore.

Metal cleaning wastes (chemical and non-chemical) are typically captured in 

portable Baker tanks and treated offsite. 

SGS must comply with both water quality-based and technology-based effluent 

limitations for its wastewater discharge to Santa Monica Bay. In 1988, the State 

Water Board granted a variance to the total residual chlorine water quality 

standard for biofouling control in the cooling system. EPA granted a similar 

variance for the total residual chlorine effluent limitation applicable to steam 

electric facilities. It is not clear if these variances will be revisited in any future 

permit reissuance.

Attachments

Attachment A List of Attendees

Attachment B Aerial Photos

Attachment C Facility Flows

Attachment D Alden Report for Phase II Compliance (December 2003)

Attachment E Addendum to Alden Report for Phase II Compliance (May 2007)

Attachment F Impingement Mortality and Entrainment Study (November 2007)

Attachment G Impingement Mortality and Entrainment Study Appendices 

(November 2007)

Attachment H Revisions Requested by LADWP
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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

Michael Hanson, LADWP

Hamid Nejad, LADWP

Peter Rudd, LADWP

Kim Burmahln, LADWP

Susan Damron, LADWP

Dipak Patel, LADWP

Dawson Dong, LADWP

Ian Guthrie, LADWP

Katherine Rubin, LADWP

See also Attachment A (DCN 10-6545A accompanying this document) for the sign-in 

sheet.
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Attachment B—Aerial Photos

See also DCN 10-6545B accompanying this document.
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Aerial View Looking West

Ground View Looking North

Aerial View Looking Northeast
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Attachment C--Facility Flows

Please see DCN 10-6545C accompanying this document.

Attachment D--Alden Report for Phase II Compliance (December 2003)

Please see DCN 10-6545D accompanying this document.

Attachment E--Addendum to Alden Report for Phase II Compliance (May 2007)

Please see DCN 10-6545E accompanying this document.

Attachment F--Impingement Mortality and Entrainment Study (November 2007, Revised)

Please see DCN 10-6545F accompanying this document.

Attachment G--Impingement Mortality and Entrainment Study Appendices (November 2007, 

Revised)

Please see DCN 10-6545G accompanying this document.
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Attachment H—Revisions Requested by LADWP

In their comment letter on the proposed rule, LADWP requested that EPA make certain revisions to the 

Scattergood site visit report in addition to their previous comments. These revisions are below.

1) Replacement for the first paragraph of section 14.0 (Additional Information).

Instead of 

“Facility representatives noted that an ongoing legal battle over the availability of emission credits 

within the South Coast Air Quality Management District have raised the possibility that no new 

projects would be able to obtain the necessary air permits. This would include facilities retrofitted 

with wet cooling towers.”

the text should read

“Permits from the AQMD for repowers of the existing units are viable since emission offsets are 

available on a megawatt for megawatt replacement of existing boilers with new, advanced gas 

turbine units.”

2) Edits to the last paragraph of section 2.0 (Facility Description)

Instead of

“SGS has a single two to three week outage annually and an eight to ten week outage every few 

years for major projects.”

the text should read

“SGS has a single two to three week outage for each unit annually and an eight to ten week outage 

for each unit every five to seven years for major projects.”

3) Edits to the first sentence of section 3.0 (Electricity Generation and Transmission)

Instead of

“SGS currently operates three conventional steam turbine units (Unit 1, Unit 2, and Unit 3) with a 

combined boilerplate generating capacity of 820 MW (Table 1).”

The text should read

“SGS currently operates three conventional steam turbine units (Unit 1, Unit 2, and Unit 3) with a 

combined generating capacity of 820 MW (Table 1).”
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4) Revisions to the first sentence of second paragraph of section 3.0 (Electricity Generation and 

Transmission)

Instead of

“Units 1 and 2 are conventional natural gas while Unit 3 is a supercritical natural gas unit.”

The text should read

“Units 1 and 2 use a conventional natural gas-fired boiler while Unit 3 uses a supercritical natural 

gas-fired boiler.”