PUBLIC HEALTH ASSESSMENT
AUSTIN, CITY OF-HOLLY STREET POWER
(a/k/a HOLLY STREET POWER PLANT)
AUSTIN, TRAVIS COUNTY, TEXAS
The Holly Street Power Plant is a natural gas/oil-fired steam electric generating facility in Austin, Texas. Residents of the East Austin neighborhood surrounding the facility have expressed concern about potential adverse health effects associated with the plant. The Texas Department of Health (TDH) was asked to evaluate the potential public health impacts of: 1) air pollution generated by the plant; 2) electric and magnetic fields associated with the plant; 3) noise levels near the plant; 4) polychlorinated biphenyls (PCBs) in water near the plant; 5) groundwater contamination; and 6) other hazards. Based on available information, we have concluded that currently, the Holly Street Power Plant poses no apparent public health hazard. Below is a brief summary of our findings.
Air Pollution
Although there was a general lack of ambient air data available for the neighborhood surrounding the Holly Street Power Plant, the Texas Natural Resource Conservation Commission (TNRCC) used an air dispersion model to predict potential air quality impacts from the facility. The model predicted that when natural gas was used as fuel, the predicted ambient air quality impacts are such that they would not pose a threat to public health. In the past, the Holly Street Power Plant periodically burned fuel oil containing 0.227% to 0.3% sulfur by weight. The TNRCC model predicted, that on the rare occasions when this fuel was burned (less than one-percent of the time), short-term sulfur dioxide concentrations could have been high enough to aggravate pre-existing respiratory conditions in sensitive individuals. In 1995, the City of Austin Electric Utility Department (EUD) voluntarily switched to transportation grade No.2 fuel oil with a sulfur content of 0.05% by weight. The sulfur dioxide levels that would result from burning this type of fuel pose no apparent public health hazard. The EUD also has agreed to only use fuel oil under emergency conditions.
Electric and Magnetic Fields (EMF)
The Holly Street Power Plant is a source of electricity; however, the plant itself is not the source of the electric and magnetic fields observed in the neighborhood. Electric and magnetic fields are associated with power lines, building wiring, lighting, and all electric appliances that may be found in the home. The power lines in the neighborhood are needed to provide electricity to homes and businesses. Magnetic field measurements near the power lines in the neighborhood adjacent to the Holly Street Power Plant were similar to the magnetic fields calculated for other power lines throughout the City of Austin. While there is considerable controversy pertaining to adverse health effects and exposure to electric and magnetic fields, we are reasonably certain that removing the plant would not reduce the magnetic fields in the neighborhood unless the power lines also were removed or de-energized.
Noise
Prior to the abatement activities performed by the EUD, day/night average noise levels measured near the plant during a preliminary assessment exceeded levels normally deemed acceptable by the United States Housing and Urban Development Authority (HUD). Although these levels were below those normally reported to result in physiologic changes or hearing loss in adults, they were well within the range of values reported to interfere with cognitive development in children. Preliminary "fade away" noise level measurements suggested that Metz Elementary School may have been subject to unacceptable noise levels.
Between 1994 and mid-1996, the EUD took significant measures to abate the effects of the noise from the facility on the surrounding community. In general, these measures resulted in reductions in noise levels that would be perceived by the human ear as a reduction in loudness of one-half (operating at 220 megawatts [MW]). Areas with sound levels considered unacceptable are now confined to the plant boundaries. There continues to be a small area immediately surrounding the facility where noise from the facility (operating at a 400+ MW output) could reach levels considered normally unacceptable; however, these sound levels have not been associated with adverse health outcomes. The EUD has soundproofed approximately two-thirds of the 107 homes and businesses in this area.
Available information indicates that abatement measures have reduced the noise at Metz Elementary school to levels below those associated with adverse effects on cognitive development. Although the noise measurements observed at Metz were made while the plant was operating at a 94 MW power output, the measurements were taken while Holly Unit 4 (the unit that most impacts the Metz School) was operating. While available evidence suggests otherwise, it still may be possible that higher power output levels at Holly (such as those that might occur during peak demand months) could result in higher noise levels at Metz. In Austin, children begin school during the month of August, one of the peak months for electrical generation. Since we could not predict with any degree of certainty the magnitude of this response, we recommended that the City EUD reevaluate noise levels inside Metz Elementary school with the plant operating at a high power output.
In response to this recommendation, on August 9, 1999, the City of Austin EUD took noise level measurements inside portable classroom four at Metz Elementary School with the Holly Power Plant units operating at a power output of approximately 496 MW (Unit 1, 73 MW; Unit 2, 90 MW; Unit 3, 193 MW; and Unit 4, 140 MW). With the air conditioning unit in the classroom turned off, the average sound levels measured inside the classroom were below those associated with adverse effects on cognitive development [personal communication].
Polychlorinated Biphenyls (PCBs)
There have been several incidents involving polychlorinated biphenyls (PCBs); however, we were not able to identify a completed exposure pathway for this contaminant. Therefore, it is unlikely that residents have been exposed to PCBs. Although PCBs have not been found in Town Lake, if they were released into Town Lake, fish could become contaminated. Fish sampling data collected in 1985 and 1995 from this area did not show PCB contamination.
Groundwater Contamination
We reviewed groundwater monitoring data reports collected from 11 on-site monitoring wells. During all sampling events available in these reports, benzene, ethylbenzene, toluene, and xylene all were reported below their respective minimum detection limits (MDLs). The levels of total petroleum hydrocarbon (TPH) found in groundwater were very low and infrequent; therefore, it is unlikely that TPH in the groundwater represents a public health threat. Since human exposure to groundwater is unlikely, groundwater was eliminated as a possible exposure pathway.
Other Hazards
The Holly Street Power Plant stores fuel in aboveground
storage tanks. Over the last 25 years, the facility has experienced several
fuel oil spills ranging in size from 50 gallons in 1992 to an upper bound estimate
of 20,000 gallons in 1974. In 1993, 200 gallons of #5 fuel oil, released from
an improperly closed section of the fuel oil transfer piping, ignited and burned
for approximately 30 minutes. The fire produced a thick black smoke visible
for miles. Because the fuel storage tanks are near residences and play areas,
the possibility of a fire does present a potential public health hazard. The
City of Austin EUD has taken deliberate proactive measures to further minimize
risk to the surrounding community.
ATSDR PUBLIC HEALTH CONCLUSION CATEGORIES
| CATEGORY A. URGENT PUBLIC HEALTH HAZARD 1 This category is used for sites where short-term exposures
(<1 yr) to hazardous substances or conditions could result in adverse
health effects that require rapid intervention. Criteria: Evaluation of available information2 indicates that site-specific conditions or likely exposures have had, are having, or are likely to have in the future, an adverse impact on human health that requires immediate action or intervention. Such site-specific conditions or exposures may include the presence of serious physical or safety hazards, such as open mine shafts, poorly stored or maintained flammable/explosive substances, or medical devices which, upon rupture, could release radioactive materials. |
CATEGORY B.
PUBLIC HEALTH HAZARD 1 This category is used for sites that pose a public health hazard due to the existence of long-term exposures (>1 yr) to hazardous substances or conditions that could result in adverse health effects. Criteria: Evaluation of available relevant information2 suggests that, under site-specific conditions of exposure, long-term exposures to site-specific contaminants (including radionuclides) have had, are having, or a re likely to have in the future, an adverse impact on human health that requires one or more public health interventions. Such site-specific exposures may include the presence of serious physical hazards, such as open mine shafts, poorly stored or maintained flammable/explosive substances, or medical devices which, upon rupture, could release radioactive materials. |
CATEGORY C.
INDETERMINATE PUBLIC HEALTH HAZARD This category is used for sites
in which "critical" data are insufficient with regard to extent
of exposure and/or toxicologic properties at estimated exposure levels.
Criteria: The health assessor must determine, using professional judgement, the "criticality" of such data and the likelihood that the data can be obtained and will be obtained in a timely manner. Where some data are available, even limited data, the health assessor is encouraged to the extent possible to select other hazard categories and to support their decision with clear narrative that explains the limits of the data and the rationale for the decision. |
CATEGORY D. NO APPARENT PUBLIC HEALTH HAZARD 1 This category is used for sites where human exposure
to contaminated media may be occurring, may have occurred in the past,
and/or may occur in the future, but the exposure is not expected to cause
any adverse health effects. Criteria: Evaluation of available information2 indicates that, under site-specific conditions of exposure, exposures to site-specific contaminants in the past, present, or future are not likely to result in any adverse impact on human health. |
CATEGORY E. NO PUBLIC HEALTH HAZARD This category is used for sites that, because of the
absence of exposure, do NOT pose a public health hazard.
Sufficient evidence indicates that no human exposures to contaminated media have occurred, none are now occurring, and none are likely to occur in the future. |
1 This
determination represents a professional judgement based on critical data which
ATSDR has judged sufficient to support a decision. This does not necessarily
imply that the available data are complete; in some cases additional data may
be required to confirm or further support the decision made.
2
Such as environmental and demographic data; health outcome data; exposure data;
community health concerns information; toxicologic, medical, and epidemiologic
data.
The Texas Department of Health (TDH), Bureau of Epidemiology, was asked by citizens to evaluate the potential public health impacts of hazardous substances and harmful physical agents associated with the Holly Street Power Plant. This Public Health Assessment addresses the specific concerns raised by residents living near the facility which include: a) the potential human health impacts of hazardous substances originating from the site, b) electric and magnetic fields associated with power lines originating from the site, and c) noise generated from the site. TDH is authorized by the State of Texas through the Health Risk Assessment Act of 1988 (Chapter 503, Health and Safety Code) to conduct health risk assessments of toxic substances and harmful physical agents. TDH has prepared this public health assessment under a Cooperative Agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). ATSDR is an agency of the U.S. Department of Health and Human Services whose mission is to prevent exposure, adverse human health effects, and diminished quality of life associated with exposure to hazardous substances from waste sites, unplanned releases, and other sources of pollution present in the environment.
The TDH first began preparing this public health
assessment in 1994; however, in 1995 the Austin City Council voted to retire
the plant in stages, closing two generators by December 31, 1998, and the other
two by December 31, 2005. Due to the announced retirement of the plant, the
completion of the public health assessment was put on hold. The plant's first
generator was shut down in September 1998; however, two months later the Electric
Reliability Council of Texas asked the city to reopen the generator and urged
the city to keep the facility operating because of the possible statewide shortage
of electricity during peak periods of energy use. In 1999, TDH was asked to
reopen its investigation of Holly.
The 22-acre Holly Street Power Plant site is located
in the eastern portion of Austin, Travis County, Texas. The site is bordered
by Holly Street to the north and Town Lake to the south. The Holly Street Power
Plant, a natural gas/oil-fired steam electric generating facility, consists
of four steam turbine generating units (Units) capable of generating a combined
total of 540 megawatts (MW) of electricity. This capacity represents 22% of
Austin's Electric Utility Department's (EUD) total electric generating capacity.
The Holly Street Power Plant is the only plant located inside the 69 kilovolt
(KV) system of transmission lines that serve the central areas of Austin. The
main purpose of the plant is to maintain reliable service at high electric loads,
to stabilize power distribution on the 69 KV system, and to compensate for the
loss of other power plants, transmission lines, and electrical utility substations.
The Holly Street Power Plant was constructed in
the late 1950s and opened for operation in 1960 with the completion of Unit
1 and the Longhorn Dam. The dam, which was built by the City of Austin EUD to
provide cooling water for the plant, created Town Lake. Units 2, 3, and 4 came
on line in the years 1963, 1965, and 1974, respectively. Units 3 and 4 are the
largest units, together contributing approximately 65% of the plant's total
generating capacity.
The plant uses natural gas for fuel, but can be
switched to fuel oil if gas supplies are interrupted. According to city personnel,
emergency use of fuel oil is rare and the last time that it was used during
an emergency was during the winter freeze of 1989-90. Historically, #2 and #5
fuel oils have been stored on the site in five above ground and one below ground
fuel-oil tanks. The above ground tanks, located on the southern portion of the
site adjacent to Town Lake, historically had an estimated storage capacity of
8.8 million gallons. The city has discontinued using the below ground tank and
has disassembled two of the larger above ground tanks.
There have been numerous spills or upsets associated
with the Holly Street Power Plant. Below is a list of events currently known
to the preparers of this report. These events were compiled from information
provided by the U.S. Environmental Protection Agency (EPA), the Texas Natural
Resources Conservation Commission (TNRCC), and the City of Austin.
Spills
On March 18, 1994, TDH staff conducted a site
visit at the Holly Street Power Plant which included a tour of the plant and
associated facilities, a drive through the surrounding neighborhoods, and a
meeting with the Plant and Environmental Managers. TDH representatives included
John F. Villanacci, Ph.D., Betty Atkins, R.N., M.P.H., Richard Beauchamp, M.
D., Kathryn Evans, M.P.H., and Judy Henry, M.S. Approximately two hours were
spent on and around the site.
The plant is situated in the East Austin neighborhood just north of Town Lake and east of IH-35. Town Lake forms the southern/eastern boundary of the site and the remaining boundaries are shared with residential properties and neighborhood recreational facilities. The surrounding neighborhood is densely populated and is made up of primarily low-income single family dwellings. Numerous residences are very close to the site, with the closest house approximately 100 feet from the fence on the west side of the plant. Metz Elementary School is approximately three to four blocks northwest of the plant. There are numerous churches within ½ mile of the plant.
The site is bordered to the north by Metz Park
and Recreation Center, which includes a playground, basketball courts, picnic
facilities, and a public swimming pool. The southern part of the site, where
the Holly Street Power Plant's fuel storage area is located, is bordered on
the west by a baseball field and on the east by Town Lake.
All facilities associated with the operation of
the Holly Street Power Plant are contained within a fence that has locked gates.
A guard was stationed at the only public entrance (on Holly Street) and public
access to the site is restricted.
The plant is located on the northern portion of
the site and consists of four separate steam turbine generating units, which
operate independently. Each of the four units burns natural gas in a boiler
that heats water to generate steam. The steam is used to spin a turbine in a
generator, creating electricity. The units were constructed separately between
1960 and 1974. According to the plant manager, this type of generator can be
expected to last at least 30 years, and up to 40 or 50 years with optimal maintenance.
The number of units operating at any given time
depends on system demand. During the site visit, two of the generators were
operating and two were down for maintenance. We were told that all four units
were used last year from the beginning of the summer until Thanksgiving. The
units were designed to operate continuously, but they are often cycled on and
off due to variation in demand.
When natural gas is unavailable to meet the operating demands of the plant, fuel oil is burned. The environmental manager indicated that fuel oil is used infrequently (approximately 1% of operating time in the last five years) and that it was last used to operate the plant in October 1993. The City has phased out the use of #5 fuel oil and has reduced the total amount of on-site fuel oil reserves in response to citizen concerns about both the March 1993 on-site fire and the pollution associated with burning #5 oil.
We walked around the Holly Street Power Plant
property where five above ground storage tanks and one underground storage tank
were located. Four above ground fuel tanks are approximately 40 feet high and
100 feet in diameter and one is approximately 40 feet high and 60 feet in diameter.
We saw wellheads of the four monitoring wells that encircle the underground
storage tank.
The tanks were built in 1974 and have a fuel storage
capacity of approximately 8.8 million gallons (roughly nine days of operation).
Fuel stores at the time of our visit included more than one million gallons
of #2 fuel oil and more than one million gallons of #5 fuel oil. The #5 fuel
oil has been moved off the site and the City has disassembled two of the larger
above ground tanks (which had a storage capacity of two million gallons each).
Total reserve capacity has been reduced to approximately four days of operation.
The area around the tanks is encircled by a clay
berm that is approximately two feet thick. Inside this berm, we saw blackened
areas associated with the March 1993 fire that was caused by a leaking fuel
line from one of the above ground tanks. The fire burned fuel oil that had leaked
out of one segment of the line. According to the plant manager, only the fuel
remaining in the fuel line burned. Fuel in the tanks was not in danger of igniting
because closed safety valves prevented additional fuel from leaking into the
lines from the tank. The fire appeared to have been contained within the berm
area.
During our site visit, we noticed that the noise
level varied a great deal depending on wind direction and speed. According to
plant personnel, the sound levels increase markedly when a unit is brought on-line.
Since our site visit, the City of Austin EUD has taken steps to reduce noise
from the plant. The specific actions taken by the city are described in the
Environmental Contamination and Other Hazards
section of this report.
The area surrounding the site is predominantly residential. Most of the residences are single family dwellings. Schools, parks, churches, and playgrounds also are in the immediate area. The 1990 census indicates that 3,389 households are within approximately one mile of the Holly Street Power Plant on the north side of Town Lake. Approximately 70% of the houses were built before 1960. This area had a 1990 census population of 9,931. Approximately 87% of the population is of Hispanic origin, 5% are of African American origin, and less than 1% are Indian, Eskimo, Aleut, or Asian. Six percent of the total population are under the age of 5 and 14% are over the age of 65. Thirty percent of the primary householders have lived in the same house since 1969 or earlier. Fifty-seven percent of the primary householders have lived in the same house since 1979 or earlier.
The TDH Cancer Registry Division maintains cancer incidence and mortality data for Texas. We analyzed cancer incidence data for the zip code area surrounding the site. Data for 1989-1992 were used. These data are presented in the Health Outcome Evaluation Section of this report.
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