San Francisco Electrical Reliability Project
Frequently Asked Questions (FAQ)
(Note: The following questions and answers reflect the highlights of the Electrical Reliability Project.
For more details, please see the Electrical Reliability Project Description document.)
1. Why is the City of San Francisco planning to develop four combustion turbine power plants?
San Francisco is the most vulnerable part of California for power outages because of its location at the tip of a
peninsula and the age of existing power plants in the city. The development of the four small power plants
would ensure the closure of the city’s oldest power plant at Hunters Point, which would increase electric
reliability and lessen air pollution in San Francisco.
2. What is the urgency for this project?
The old power plant at Hunters Point (Unit 4) will not comply with air quality standards in 2005. PG&E has
obtained permission to operate the plant through 2005 in its existing condition using emission credits.
However, in 2006 PG&E will likely have to retrofit the plant with costly new emission control equipment to keep
it in operation. Completion of the four new power plants before 2006 will allow PG&E to retire Hunters Point
Unit 4 and avoid the costly retrofit that to be paid for by the ratepayers.
3. Will these generators ensure the shut down of the Hunters Point Unit 4?
The City has obtained a written commitment from the California Independent System Operator (ISO) that they
allow PG&E to shutdown Hunters Point No. 4 when the four combustion turbines (CTs) have been installed.
4. How did the City of San Francisco acquire the new combustion turbine generators?
The City of San Francisco and the State of California sued several power plant owners during the recent
energy crisis. The Williams Companies, Inc., the first party to settle, provided six natural gas power combustion
turbines (CTs) as partial compensation to settle this lawsuit. Due to this area’s vulnerability to power outages,
the City was able to obtain four of these gas turbines to improve electric reliability within San Francisco and to
facilitate the shutdown Hunters Point in 2005.
5. How will the costs of building the power plants be paid for, and who will pay?
The City will finance the construction of the power plants and recover the cost through a 10-year power
purchase agreement with the California Department of Water Resources (DWR). The DWR will pass through
these costs to ratepayers of California’s investor-owned utilities. The City will own the power plants debt-free
after 10 years.
6. What advantages do the new power plants provide?
 Lower probability of the loss of electric service to residents and businesses of San Francisco,
 Closure of the city’s oldest power plant, Hunters Point 4, before it is required to be retrofitted with costly
new emission control equipment,
 Quick start capability that enable the new plants to be operated only when needed rather than operating
around- the-clock as occurs now at the large power plants at Hunters Point and Potrero,
 State-of-the-art emissions control equipment that significantly reduces air pollution in San Francisco.
7. How does the City intend to construct the power plants?
The City will select a qualified firm to build the power plants through a competitive bidding process. The
resulting engineering-procurement-construction contract transfers all construction risks to the contractor.
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8. Where can these power plants be located?
The major consideration that the City is taking into account in choosing the location for the new power plants is
whether they make possible the shutdown of the oldest and most polluting power plant at Hunters Point – Unit
4. Hunters Point Unit 4 currently plays a critical role in meeting peak demand for electricity in San Francisco
as well as protecting the high voltage transmission system throughout the Bay Area. The California ISO, which
operates the statewide transmission system, has indicated that the new power generation needs to be located
on the 115 kV systems in San Francisco. In addition, the power plants must be relatively close to high volume
natural gas pipelines and on industrially zoned land.
Given these considerations, site selection focus has been around the Potrero and the Mission substations. The
area surrounding the Potrero substation is zoned industrial and has access to both high volumes of natural gas
and transmission lines. Property near the Mission substation is also under consideration due to the potential
for cogeneration to serve the downtown district heating system.
9. What environmental review is required before building these power plants?
The City of San Francisco will submit an Application for Certification (AFC) to the California Energy
Commission (CEC) for permitting these power plants. The CEC will review, in an open public process, all
environmental issues associated with the development of the power plants needed to comply with the California
Environmental Quality Act (CEQA).
10. How do the combustion turbines (CTs) differ from the power plants that are already located at
Hunters Point and Potrero?
The new CTs will be much cleaner. There are two types of power plants at Hunters Point and Potrero. One
type uses large natural gas boilers and steam turbines. Each of these sites has one of these plants that
typically run around-the-clock. These existing plants have outdated emission control equipment that will need
to be replaced soon if they are not shut down.
The other type of plant uses a jet engine that burns fuel oil. There are three plants of this type at Potrero and
one at Hunters Point. They do not have any emission control technology and operate infrequently. They are
limited in the number of hours they can run by the Bay Area Air Quality Management District (BAAQMD). The
old existing units are approximately 40% less efficient than the new combustion turbines. Compared to the new
natural gas powered CTs, the existing older oil-burning plants with no emission controls produce more than 20
times the emissions per kilowatt-hour.
11. Combustion turbines (CTs) make a lot of noise. How loud will these CTs be?
There are many ways to control noise. The City will control noise to make the power plants compatible with the
surrounding area.
12. How much land is needed?
When installed alone, each CT power plant requires approximately one (1) acre. If installed together on the
same site less land is required.
13. Will these new combustion turbine power plants be less polluting than the proposed Mirant Power
Plant?
Yes, the most significant differences between the City’s power plants and that proposed by Mirant are their size
and the amount of time they will operate. Mirant’s proposed Potrero No. 7 Power Plant is 540 MW. It is a
merchant power plant designed to operate at a high capacity factor, in the range of 80 to 85%, to recover its
investment. The City’s proposed CTs are 185 MW and expected to operate at a much lower capacity factor
resulting in significantly fewer air emissions.
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