Health Consultation:
USX Duluth Works Saint Louis River NPL Site
Duluth, St. Louis County, MN
CERCLIS # MND039045430
August 13, 1998
Prepared By:
The Minnesota Department of Health
in Cooperative Agreement with the
Agency for Toxic Substances and Disease Registry
FOREWORD
This document summarizes potential public health concerns associated with the U. S. Steel
Duluth Works portion of the Saint Louis River National Priority List (NPL) Site in Duluth
Minnesota. This document is based on a formal site evaluation prepared by the Minnesota
Department of Health (MDH). A number of steps are necessary to do such an evaluation, and
include the following:
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Evaluating exposure: MDH scientists begin by reviewing available information about
environmental conditions at the site. The first task is to find out how much
contamination is present, where it is found on the site, and how people might be exposed
to it. Usually, MDH does not collect its own environmental sampling data. We rely on
information provided by the Minnesota Pollution Control Agency (MPCA), U.S.
Environmental Protection Agency (EPA), and other government agencies, businesses,
and the general public.
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Evaluating health effects: If there is evidence that people are being exposed—or could
be exposed—to hazardous substances, MDH scientists will take steps to determine
whether that exposure could be harmful to human health. The report focuses on public
health—the health impact on the community as a whole—and is based on existing
scientific information.
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Developing recommendations: In the evaluation report, MDH outlines its conclusions
regarding any potential health threat posed by a site, and offers recommendations for
reducing or eliminating human exposure to contaminants. The role of MDH in dealing
with hazardous waste sites is primarily advisory. For that reason, the evaluation report
will typically recommend actions to be taken by other agencies—including EPA and
MPCA. However, if there is an immediate health threat, MDH will issue a public health
advisory warning people of the danger and will work to resolve the problem.
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Soliciting community input: The evaluation process is interactive and ongoing.
Typically, MDH begins by soliciting and evaluating information from various
government agencies, the organizations responsible for cleaning up the site, and the
community surrounding the site. Any conclusions about the site are shared with the
groups and organizations that provided the information. Once an evaluation report has
been prepared, MDH seeks feedback from the public. If you have questions or
comments about this report, we encourage you to contact us.
Please write to:
OR call us at:
Community Relations Coordinator
Site Assessment and Consultation Unit
Minnesota Department of Health
625 Robert St. N., Box 64975
St. Paul, MN 55164-0975
(651) 201-4897 or 1-800-657-3908
(toll free call—press "4" on your touch tone phone)
Introduction
The Minnesota Department of Health (MDH) was requested by the Minnesota Pollution Control
Agency (MPCA) to complete a Health Consultation on issues of concern for public health at the
U.S. Steel - Duluth Works (USX) “Superfund” (National Priorities List; NPL) site in St. Louis
County, Duluth, Minnesota. The site is extremely large and contains large deposits of
contaminated and non-native soils and sediments as a result of operations on the site.
Furthermore, there is a large amount of contaminated sediment adjacent to the site in the St.
Louis River. The sediments include elevated concentrations of mercury, PCBs, and other
compounds which can be ingested by aquatic organisms. There is an MDH Fish Consumption
Advisory in effect for the entire lower St. Louis River (including regions upstream of the site)
for mercury and polychlorinated biphenyls (PCBs).
A Community Workgroup (CWG) initiated by MPCA has been involved in discussions
associated with the cleanup of this site since 1995. MDH has regularly attend the monthly CWG
meetings, as has MPCA and representatives of US Steel. Carl Herbrandson, MDH staff, toured
portions of the site in June 1997 and April 1998. MDH has reviewed documents on file at
MPCA offices, reviewed independent research reports on the St. Louis River Bay region, and
had discussions with MPCA staff and community members as part of our information gathering
process. MDH has also reviewed historic site activities and steelmaking processes.
There is a large amount of environmental data available on the USX site. Unfortunately, data on
specific activities or locations at the site are not easily found. During the file review for this
health consult, MDH was unable to locate information about mercury contamination on the site,
the cleanup of mercury from the ‘meter shop’, or a significant amount of data on the
groundwater springs known as Seep 1 and Seep 2. To a certain extent this is to be expected due
to the sheer volume of files on this site. However, MDH recommends that data submitted by
USX or their consultants be organized into reports containing associated references and that the
transfer of data as attachments to letters be limited. Since the review of data for this health
consultation was completed, MDH has received data described as an incomplete Phase 2
investigation (received by MPCA from USX on July 8, 1998). This data will be reviewed at a
later date.
To facilitate cleanup, the most contaminated areas of the USX site were identified as operable
units (OUs). Cleanup of these disconnected operable units has been, in general, guided by the
Record of Decision (ROD) of February 22, 1989 (MPCA 1989). United States Environmental
Protection Agency (EPA) concurrence on the ROD was not obtained (EPA 1989). EPA has had
no involvement on this site since their review of the ROD.
Given the size and the current dormant condition of the site it is easy to overlook that this site
was historically an integrated operation where use of one area may have led to contamination of
adjacent areas. MDH has attempted in this health consultation to identify data gaps which need
to be filled for us to be able to make confident statements about health risks which may be
associated with areas of the site and the site as a whole. The identification of data gaps should
not be confused with identification by MDH of specific health risks. MDH emphasizes that
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these data gaps represent uncertainties which, at this point, make qualitative or quantitative
health risk analysis not possible. MDH views the uncertainty about environmental conditions
over large areas of the site as one of the most important issues (along with sediment remediation
and the long term maintenance of remediated areas) remaining to be investigated which could
potentially impact public health. As mentioned above, USX has recently made new data
available which may address some of these remaining issues.
This health consultation discusses data gaps which MDH has identified at this time. For the
purposes of this document MDH did not review information or issues concerning the demolition
of facilities, demolition landfills, the current condition of remediated operable units on site, or
any data which has been submitted to MPCA since June 1, 1998. This health consultation by no
means contains discussion of all issues related to health which could be associated with the USX
site.
Health consultations are used by MDH to disseminate information and MDH positions to the
public and interested parties. In order to do this in a timely manner, MDH does not discuss all
issues of concern but attempts to focus on a few important issues. Future health consultations
can focus on other issues related to public health and this site.
Site Background
The USX site is a 640 acre plot on the St. Louis River about 8 miles southwest of downtown
Duluth, MN (Figure #1). US Steel operated a steel mill on the site until the 1970's. The site was
designated a Superfund site in 1984. The USX site is listed with the Interlake Duluth Tar site as
the St. Louis River Site on the National Priority List and is also listed separately as a RCRA Site
(MND981098577, MND980615710). Preliminary environmental data on the site was primarily
contained in two documents: 1) Plans Submitted Pursuant to Part IV and Part V, Task A to
Exhibit A March 26, 1985 Response Order by Consent (Barr 1985); and 2) Remedial
Investigation Final Report - December 1986 (Barr 1986). Remediation of the site began in the
1980's and is continuing. Areas containing open tar, tanks, and buildings have been remediated.
Some of the areas containing tar have been treated on site, others have been removed and the tar
used as fuel. Tanks and products inside them have been removed from the site. Buildings have
been demolished and moved to demolition landfills both on site and off site.
MDH has written two previous health consultations on the USX site: 1) Health Assessment for
St. Louis River Site, Duluth, MN (MDH 1989) which contains information about both the USX
site and the Interlake site; and 2) Health Consultation on Contaminated Sediments: St. Louis
River/U.S. Steel-Duluth Works (MDH 1995).
Operations on-site
US Steel began operation of a steel mill in the Morgan Park area of Duluth, Minnesota in 1915.
The facilities on-site included coke ovens, a coke by-products plant, open-hearth and blast
furnaces, a blooming mill, a billet mill, and a merchant mill. Storage facilities for ore, coal, and
limestone were also located on-site. In 1922 a continuous rod mill, wire mill, nail mill, pot
annealing equipment, staple and woven fence machines, nail cleaning, bluing and coating
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facilities, rod and wire cleaning facilities, and galvanizing facilities were added. From 1918
until 1929 benzene and toluene were also produced on-site. Operation of the steel mill continued
until 1975 when open hearth and blast furnaces were shut down. The coking plant ceased
operations in 1979 (MPCA 1989).
Waste Stream
MDH has reviewed steelmaking procedures to obtain information about the possible
contamination of the environment, however; MDH does not have direct information about all of
the processes and waste at the Duluth Works site.
There are three general processes which are performed at an integrated steel mill. 1) Coal is
converted into coke; 2) iron is removed from ore; and 3) steel is made from iron and coke. The
steel is then processed and formed into useful products such as sheets, shell steel and wire.
Coking ovens remove volatile compounds from coal leaving a solid carbon which is used as fuel
in ironmaking processes and as a carbon source. Tar, oils, and hydrocarbon based gasses are byproducts of the process. Gases are generally recycled for use as fuel in the coking ovens. Upon
removal from the coking ovens, large amounts of water are used to quench the hot coke. This
operation generates waste water containing ammonia compounds, coke breeze and other
contaminants.
Large amounts of limestone are used in the ironmaking process to remove acidic ores from iron.
Coke is used to reduce iron ore to iron. The primary waste products from this stage of
production are slag and hydrogen sulfide and sulfur dioxide gases.
In the final steelmaking process, carbon is added to the iron to make steel. Forming the steel into
useable products entails rolling and often annealing the hot steel. Large amounts of oil are
needed to lubricate rollers and, in some processes, to quench the steel. Acids are used to remove
oxidized steel. The primary wastes from this operation are steel scale, acid / metal solutions,
oils, greases, solvents, and grindings from rollers (typically high chromium steel).
Waste Deposits
Tar and ‘non-native’ soils and sediments are the major uncontainerized waste products which
have been identified on-site. Loosely defined, non-native materials are materials which were not
found on the site prior to it’s development. Typical identified non-native materials at the USX
site are slag, coke fines, flue dust, mill scale, and coke. Often the identified wastes have been
mixtures of these primary contaminants.
Eighteen areas containing waste deposits were identified in the Record of Decision (MPCA
1989). These areas appear to have been identified by visually determining the presence of waste
deposits. Response actions appear to have been restricted to remedial actions at locations where
soft tar deposits were found, remedial action on containerized wastes, and dressing of some
dredged spoil (dredged sediments which are deposited on land) areas. Areas containing large
amounts of non-native materials as well as some dredged spoil areas were designated for
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monitoring.
The coke plant was located on the northern side of the site (see Figure #2) just south of Steel
Creek. During operations waste from the coke plant was discarded into the creek. Over the
years of operation, the creek was dredged to allow continued water flow. Some dredged spoils
were deposited north of the creek in an area now designated Operable Unit K (OUK). Over the
years a considerable amount of open water was filled in over the entire length of the creek (see
Figure #3) and in the delta area, presumably by waste products. It should be noted though that
nitrogenous wastes (such as ammonia which is formed in large quantities as a by-product of coke
production and is typically reclaimed and sold for use as fertilizer) were likely discarded in
quantities which could have increased terrestrial plant growth as well as algae growth in the
creek and river.
The wire mill pond, OUP, is presumed to have been used as a settling pond for waste from the
wire mill and other product finishing mills. It is possible, though, that on-site sewers and other
on-site facilities discharged materials into the wire mill pond. A considerable amount of open
water in the wire mill pond was filled in over the years (see Figure #4). Material which MDH
would expect to be found in areas filled in or containing sediment dredged from the pond include
scale, oils, cutting oils, zinc, copper, nickel, and possibly PCBs and mercury. Non-native
materials were observed by MDH on the southwestern side of the pond in April 1998 (MDH
1998). This waste was presumed to be dredged spoils from the wire mill pond.
During demolition, elemental mercury was found in and adjacent to a meter shop on the site. A
review of PCA files has revealed communication about the find and cleanup, but MDH has been
unable to locate reports on the magnitude and extent of the contamination or post cleanup
environmental sampling results.
Maps of the site on file at MPCA (Barr 1986; MPCA 1989) identify two seeps on site (see
Figure #2). One is SW of the old pumping house and the other is SE of the demolition landfill in
the southeastern corner of the site. Information about the PAH contamination of the seeps is
available and shows some PAH contamination. However, MDH could not determine if all
contaminants in the seeps of potential health concern have been identified. Furthermore, MDH
did not find any groundwater study which may have identified potential sources or other
locations on-site where groundwater contamination may be close to or at the ground surface.
Sampling of sediments in the St. Louis River was undertaken in 1993 and 1994 by MPCA in
conjunction with the United States Environmental Protection Agency. The purpose of the study,
often called the Mudpuppy Study, was to determine contaminants in the river and the toxicity of
those contaminants to aquatic organisms. The 1993 study included sampling of areas adjacent to
the wire mill pond outlet and the Steel Creek delta (MPCA 1997).
Chemicals of Concern
Polycyclic aromatic hydrocarbons
A detailed discussion of environmental PAH contamination and toxicity is included in the MDH
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Health Assessment on this site dated June 27, 1989 (MDH 1989), and further discussion is
contained in the July 20, 1995 MDH Health Consultation (MDH 1995). It is not our intent to
repeat these discussions. However, in summary the following points should be noted:
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PAHs are formed by incomplete combustion of organic material and are ubiquitous in the
environment. Typical sources of PAHs in the environment are vehicle exhaust, tobacco
smoke, wood burning, and charcoal grilled foods.
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Average human PAH intake is estimated at 1 - 14 µg/day (ATSDR 1994).
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There are hundreds of compounds which are classified as PAHs. Some have been
designated as cancer causing PAHs (cPAHs). Other PAHs have not been shown to cause
cancer (nPAH). Human health effects caused by exposure to some PAHs have not been
determined. Total PAH (tPAH) is a measure of the concentration of all PAHs analyzed.
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Health risk cannot be determined from data describing exposure to concentrations of
unidentified or summed cPAHs, nPAHs, or tPAHs. Health risk is typically estimated by
summing the risk from each individual PAH compound.
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Environmental exposure to PAHs is always in the form of exposure to mixtures of many
different PAHs. The relative toxicity or cancer risk of different mixtures is different.
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It is estimated that there are 1,500,000 cubic yards (yd3) of non-native materials on-site
(exclusive of sediments in the St. Louis River). These materials contain up to 50,000 mg
/ kg tPAH, however in most areas the PAH concentration is considerably less. cPAH
concentrations in samples designated as ‘non-tar soils’ range from 14 to 3,000 mg/kg
(MPCA 1989).
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Potential exposure to PAHs from the USX site is likely limited to dermal exposure to
soils and sediments, and ingestion of soils and suspended sediments; however it is
possible that some exposure could come from ingestion of contaminated fish.
PAH contamination on-site is not confined to a single area, but appears to be greatest in the areas
of the coke plant, the wire mill pond, and regions affected by them including: Steel Creek
upstream from the outlet control structure, dredged deposits from the creek, filled in areas
between the outlet control structure and the railroad tracks, the creek delta which extends into
the St. Louis River, dredged deposits from the wire mill pond, and the sediments in the river
itself. A large amount of PAH containing tar and non-native soils were stabilized in Operable
Unit J (OUJ) in 1997. Other deposits containing high concentrations of tar have been removed
from the site. Still, areas with high levels of PAH contamination and possibly tar deposits
remain in the confines of Steel Creek, especially above the outlet control structure (Barr 1986;
MPCA 1989).
Mercury
During demolition and cleanup elemental mercury was found on-site. It may have been
associated with high current electrical switches in a meter shed. During the review of data for
this health consultation, MDH was unable to locate data on soil analysis for mercury at the USX
site. It is our understanding that information on levels found in soil is contained in documents
presented to PCA by USX on about July 8, 1998. MDH will review these data in a future health
consultation.
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Huge quantities of coal were used at the Duluth Works site during operation of the steel mill.
Coal was used as a fuel and also for making coke. Mercury is an impurity found in coal.
Currently nationwide, the greatest source of environmental mercury pollution is coal (EPA
1997). While mercury vapor is released from burning coal, quenching of coke or cooling of
exhaust by water spray can remove some mercury from air emissions and concentrate it in waste
water or sludge. Therefore, MDH believes that it is appropriate to test all areas of the site which
could have been affected by the waste stream for mercury contamination. At this point there is
not enough information available on the magnitude and extent of mercury contamination on-site
to characterize the mercury contamination on-site, or the health risk which may be associated
with it.
Mercury is a neurotoxin which accumulates in animal tissue. It is a public health concern in both
its elemental and organic (e.g. methyl mercury) forms. In the environment elemental mercury
can vaporize and be transported over long distances, or it can be changed by bacteria in water
and soil into methyl mercury. Methyl mercury is of particular health concern due to its enhanced
bioavailability relative to elemental and inorganic mercury, it’s ability to traverse the blood-brain
barrier, and it’s potential to accumulate in sensitive tissue (e.g. nervous, fetal) in humans.
Furthermore, methyl mercury bioconcentrates in organisms which are highest on the food chain
as it is readily taken up, but only very slowly excreted, by animals. Immature animals have been
shown to excrete mercury at even slower rates than adults.
MDH is concerned about any addition of mercury into the environment due to its toxicity and to
the high levels of mercury which are already found in environmental media, fish, and wildlife.
Performance criteria and detection limits for mercury in water were set in the Response Action
Plan (RAP) for the wire mill pond at 0.2 parts per billion (ppb). MPCA’s current surface water
criteria 6.9 parts per trillion (ppt) for mercury reflects a new understanding of the accumulation
and toxicity of environmental mercury. Furthermore, MDH notes that the Great Lakes Initiative
has classified mercury as a ‘zero emissions’ contaminant due to the exceedance of their standard
of 1.3 ppt in background samples in many areas of the Great Lakes Region. While it is MDHs
understanding that some sampling for mercury has occurred in Steel Creek, the OUJ RAP does
not appear to require mercury sampling. Data from the previously mentioned Mudpuppy Study
(MPCA 1997) as well as other data available from MPCA has shown elevated concentrations of
mercury in sediment adjacent to the outfalls of the wire mill pond and Steel Creek.
Polychlorinated biphenyls and chlorinated organics
PCBs are typically found in transformers and large capacitors which were manufactured prior to
the mid 1970's. Prior to the 1970's PCBs were also found in some lubrication oils used in
industry, as well as in cutting oils. Other chlorinated organic compounds, such as chlorinated
dibenzodioxins (dioxins) and chlorinated dibenzofurans (dibenzofurans) can be formed in small
quantities during the burning of organic fuels. During the 1970's research showed that PCBs
which had been discarded were accumulating in the environment and were not being degraded at
a significant rate. PCBs were also found to accumulate in the tissue of animals and to
bioconcentrate in organisms at the top of the food chain. In 1977 production of PCBs in the
United States stopped. A sensitive endpoint for PCB toxicity has been shown to be the
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development of the human nervous system. Human exposure to PCBs is a public health issue of
concern to MDH.
PCBs were found in 5 of the 271 oil-containing transformers on site at the USX site (Barr 1986).
These transformers were disposed of in accordance with state and federal regulations.
MDH does not know if any of the oils historically used in the production processes at the site
contained PCBs. MDH has seen data from sediment samples taken from the Saint Louis River
near the wire mill pond and Steel Creek by MPCA staff and USX representatives in 1993. While
these data showed no detection of PCBs, MDH has not been able to locate the original data and
does not know what detection limits were applied to these analyses.
Samples were also taken from St. Louis River sediment at locations adjacent to the wire mill
pond outfall and the Steel Creek delta during the 1993 Mudpuppy Study. These samples were
analyzed for many compounds including PCBs, dioxin (specifically 2,3,7,8tetrachlorodibenzodioxin), and dibenzofuran (specifically 2,3,7,8-tetrachlorodibenzofuran). All
three compounds were found at concentrations above sediment quality criteria (SQC) which are
based on ecological effects. These levels may also exceed levels of health concern for
individuals eating fish feeding in these areas, or minimally, contribute to the contamination of
fish in the St. Louis River. The highest concentrations measured in surficial sediments adjacent
to the site were 190 µg/kg tPCB, 13 ng/kg dioxin, and 13 ng/kg dibenzofuran (dioxin toxic
equivalency factor of 0.1) (MPCA 1997). MPCA ecological screening values for sediment are
1.8 µg/kg tPCB and 1.2 ng/kg dioxin toxic equivalents. These data have been reviewed and
published by the EPA and MPCA (MPCA 1997).
Hexachlorobenzene (HCB), another chlorinated organic compound, has also been found in
elevated concentrations in sediments adjacent to the site. HCB is of concern to MDH because of
its ability to concentrate in organisms at the top of the food chain (e.g. piscivores and humans).
MDH staff will be reviewing available studies to evaluate human health effects which could
potentially be associated with exposure to PCBs, dioxins, dibenzofurans, and HCB
contamination in St. Louis River sediments or ingestion of contaminated fish. No samples of
fish tissue from this area of the river have been analyzed for these chemicals of concern.
MDH emphasizes that these Mudpuppy data were from a single sampling event on the river,
analyzed samples were taken from homogenized cores at depths ranging 30 centimeters, and this
contamination has not, to our knowledge, been confirmed in another sampling event. However,
since these compounds were identified in the sediments adjacent to the site and since there may
be some conflicting data, MDH believes that sampling should take place to establish the
magnitude and extent of any sediment contamination with PCBs, dioxins, dibenzofurans, and
HCB.
Typically, while PCBs accumulate in fish and sediment they are not found in measurable
concentrations in water. PCBs are generally transported from contaminated sites to sediment
attached to small particles or organic material. If the water contains oil or even a significant
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amount of solvents, PCBs can move in groundwater or surface water. Therefore, sampling of
surface water, groundwater, and seeps on the site for oil, grease, and solvents may be important.
MDH is unaware of any requirement in the RAPs performance criteria covering Steel Creek and
the wire mill pond to sample for these contaminants. Furthermore, MDH has not been able to
locate any data on testing of seeps on the site for these contaminants.
Metals
Zinc is often a major contaminant found near steel mills. Zinc can be a by-product of steel
production and it is also used at mills in galvanizing and other plating processes. While it is a
nonnative material, the toxicity of metallic zinc is very low. Therefore, MDH does not expect
zinc contamination to be associated with a human health risk at the site. Very high levels of zinc
have been found in sediments in the St. Louis River adjacent to the site (MPCA 1995; MPCA
1997). Zinc in sediment would be expected to have ecological effects at much lower
concentrations than the concentrations at which it may affect human health. Therefore, MDH
expects cleanup criteria for zinc will be set by evaluating the ecological risk.
Chromium is a contaminant associated with steel mills which may be a byproduct of production
or it may be a machining waste from the rollers in a forming mill. Chromium in its reduced form
is not very toxic. Therefore, MDH does not expect chromium contamination to be associated
with a health risk at the site. Very high levels of chromium have been found in sediments in the
St. Louis River adjacent to the site (MPCA 1995; MPCA 1997). Chromium in sediment would
be expected to have ecological effects at much lower concentrations than the concentrations at
which it may affect human health. Therefore, MDH expects cleanup criteria for chromium will
be set by evaluating the ecological risk.
Lead, cadmium, nickel, and copper are also metal contaminants which may be associated with
steel mills. Lead, cadmium, and nickel may be impurities in the ore which is refined in the
ironmaking process. Cadmium and nickel are often used in metal plating processes. Copper
may have been used in the manufacture of wire. All four of these metals can be associated with
toxic effects in humans. Direct ingestion of water and sediment containing any of these four
metals could be of concern to MDH depending on concentration and the frequency of exposure.
Furthermore cadmium has been shown to accumulate in fish and therefore ingestion of cadmium
exposed fish may be of concern to MDH. While these heavy metals have been found at levels
above PCA sediment criteria levels (MPCA 1995; MPCA 1997), due to limitations in the
available data on the magnitude and extent of contamination, as well as uncertainties
surrounding the potential for exposure (e.g. sediment depth of contamination, fish consumption),
MDH cannot determine if there could be a health risk associated with their presence in these
sediments at this time.
Acids and solvents
Acids and solvents have historically made up a significant portion of the waste from steel mills.
They are typically recycled if possible, and unuseable sludge or solutions are discarded. Under
some conditions these by-products can contaminate soil and groundwater near a facility.
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MDH is unaware of any environmental sampling for solvents on the USX site. Groundwater
contamination is not currently a direct concern to MDH because there are no known receptors
downgradient from the site. However, there is some indirect concern because contaminated
groundwater can discharge into the river, surface water on site, and to surface seeps. Seeps
noted in previous sections of this document demonstrate the potential for contaminated
groundwater on the site to contaminate surface and subsurface soils. Monitoring of water quality
and enforcement of water quality standards in the St. Louis River, Steel Creek, the wire mill
pond, and other surface waters on the site should insure against significant pollution from
groundwater discharging directly to surface waters.
Soil contamination is of concern to MDH due to the possibility of exposure of humans to large
deposits of acid or solvents on-site. MDH has not identified areas of the site where acid and / or
solvent disposal activities took place. If historical records are not sufficient to identify disposal
locations, a groundwater study could be valuable in identifying these areas. It is expected that
some leaching of large waste deposits has occurred at the USX site. A survey of groundwater
contaminants in monitoring wells could help to identify locations which may be of concern for
human exposure on-site.
Benzene and toluene
Benzene and toluene were produced on the site from 1918 to 1929. Furthermore, benzene is a
by-product of coke production and as such could have been a contaminant in the waste stream
from the coke plant. Human exposure to benzene is of concern to MDH primarily due to its
classification as a human carcinogen. MDH is concerned to a lesser degree about human
exposure to toluene due to its more limited association with health risk. Typically, benzene and
toluene are rapidly degraded in the environment. However, there are conditions under which
degradation of these compounds may be limited. MDH is unaware of any attempts to locate
environmental impacts from the historic benzene production on the site or to analyze for benzene
in the waste stream from the coke plant or other areas of the site.
Discussion / potential human exposure and data gaps
Public health can be protected at hazardous sites either by removing the hazardous material or by
removing or limiting the potential for human exposure to the hazardous material. Currently the
site is presumed to have restricted access. In reality, easy access is available at numerous points
along the northern boundary as well as from the river (east). MDH has not toured either the
western or the southern boundaries of the site.
MDH has seen evidence of use of the site by the public both along the railroad tracks and on top
of OUK (MDH 1998). During a site visit in April 1998 MDH observed Operable Units A, J, K,
and P. These operable units appeared to be in good condition. MDH believes that under current
conditions human exposure to contaminants on remediated operable units is unlikely. However,
weathering could change the condition of these operable units; therefore, routine inspections of
these OUs should be required. Furthermore, MDH recommends changes in the detection /
performance limits for OUJ and OUP to address uncertainties about current leaching of
chemicals of concern (e.g. mercury) from these OU’s.
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Operable Unit K contains an estimated 89,000 cubic yards of dredged materials. Dressing of this
operable unit was completed in 1992. The EPA typically requires a formal five-year review of
areas where contaminated materials are left on site (EPA 1989). The RAPs for OUJ and OUP
require a similar review. While MDH understands that MPCA staff inspect the OUs regularily,
MDH does not believe that the inspection of OUK, OUA, and other OUs (beside OUJ and OUP)
is required. Furthermore, we have been unable to locate any documents evaluating the
effectiveness of the remedies in these OUs. A five-year review process of all areas where
contaminants are left on-site should be followed to assure that changes in conditions can be
monitored and evaluated(EPA 1989).
MDH is concerned about the potential for chemicals of concern to be transported from areas of
contamination via groundwater. As discussed in a previous section existing seeps on-site
suggest the possibility of surface water and soil contamination at locations remote from source
contamination.
Large areas of the site have not been sufficiently investigated to allow characterization of
possible exposure to contaminants and associated health risks. MDH has reviewed documents
describing known contamination hotspots or operable units on the site. However, most of the
site has not been included in any designated operable unit. Large areas of the site are likely free
from contaminants at levels of health concern. However, given the amount of industrial activity
which has historically occurred on the site, a significant amount of sampling of these undisturbed
or reputedly clean areas will be necessary before these individual areas can be characterized with
regard to health concern.
As discussed in the 1995 MDH Health Consultation, exposure to contaminants in the St. Louis
River may occur by ingestion of water and suspended sediments, dermal exposure to water and
sediments, and ingestion of contaminated fish. MDH has issued a fish consumption advisory for
the lower portion of the St. Louis River including areas adjacent to the USX site. The advisory
is for mercury and PCB contamination. The USX site is not the only site which is suspected of
discharging these two contaminants into the river. However, there is some evidence (see
Mudpuppy discussions above) which suggests that the site may have contributed to the mercury
and PCB contamination in the river.
Mercury does not degrade, and PCBs are not believed to undergo significant degradation in
sediments. While PCBs in sediment can be covered by clean sediments, given their
hydrophobicity they are typically cycled through bacteria, invertebrates, and fish and often
remain in the mobile segment of sediments over a long time period. Furthermore, storm events
or changing river channels can expose previously covered deposits potentially supplying a large
source of contamination to the river system and possibly exposing humans.
This document does not cover all possible concerns which MDH might have about the USX site,
but it represents an outline of known data gaps which we believe must be filled in prior to a
qualitative or quantitative appraisal of the potential health risk which may be associated with
exposure to contaminants on-site.
10
Conclusions
!
A steel mill was located on the 640 acre USX site from 1915 until 1979. The site was
listed on the NPL in 1984. Two major waste streams have been identified: 1) waste
from the cokemaking, ironmaking, and possibly the steelmaking processes were
discarded into the vicinity of Steel Creek, and 2) waste from the wire mill and other
product mills was discarded into the wire mill pond. It is estimated that there are
1,500,000 cubic yards (yd3) of non-native materials on-site (exclusive of sediments in the
St. Louis River). A Record of Decision was signed by the MPCA in 1989.
!
Contaminated hotspots have been designated as operable units, but environmental data on
most of the site, exclusive of the remediated operable units, has not been obtained or has
not been available to MDH. MDH views the uncertainty about environmental conditions
over large areas of the site as a potentially significant health concern. MDH is
particularly concerned about data gaps on the following:
P
the possibility of remaining unidentified hotspots or areas of large contamination
containing:
N
tar / PAHs
N
mercury
N
solvents
N
acids
N
benzene
P
groundwater or non-saturated zone contamination, contaminated seeps, and
contaminated surface water pools or wetlands
P
PCB and chlorinated organic compound contamination
P
mercury contamination of groundwater, surface runoff, and sediments
!
Benzene was manufactured on the site and was a waste by-product and yet its location in
the waste stream has been unidentified and typically, environmental samples from the site
have not been analyzed for benzene. Typically, benzene will degrade rapidly in the
environment; however, under some conditions benzene degradation may not occur.
!
The exposure and release of contaminated soils and sediments by storm events or
changes in creek and river channels is of concern to MDH.
!
More generally MDH is unaware of any required, scheduled review process for
evaluating the condition of contaminated and non-native materials left on-site. For
instance, the typical five-year review of areas where contaminated soils have been left
on-site has not been instituted for all operable units.
Recommendations
!
Completion of a historical use investigation to guide subsequent more intensive
environmental investigations and sampling of potential hot-spot areas (PAHs, mercury,
oils [PCBs], solvents, acids)
!
Environmental investigation and sampling of non-hotspot areas of the site to determine
the likelihood and extent of contamination of areas not included in the current operable
units
!
Mercury recommendations:
P
Sampling of identifiable waste streams for mercury
11
Environmental mercury sampling of soil, non-native materials, and sediment
throughout the site
P
Detection and performance levels lowered to reflect levels of concern identified
in the MPCA surface water criteria
PCB and chlorinated organic compound recommendations
Investigation of PCB use on-site
P
Environmental sampling for PCB contamination in likely locations as determined
by historical use and waste stream investigations
P
Confirmatory sampling for dioxins, dibenzofurans, and HCB in sediments and at
other points in the waste stream
P
Sampling of water, sediments, and soils include analyses for solvents, oils, and
grease
Groundwater recommendations
P
Compilation of data on the identified seeps (Seep 1 and Seep 2)
P
Compilation of data from existing on site monitoring wells
P
Continued and expanded sampling and analyses (including mercury, solvents,
oils, and grease) of surface water and water from monitoring wells on site
P
Monitoring groundwater leaching from OUJ and OUK
P
Investigation of the feasibility of a groundwater study to locate as yet unknown /
unidentified areas of contamination on site
Benzene recommendations
P
Identification of possible sites of benzene contamination (see historical use
above)
P
Environmental sampling for benzene in appropriate waste streams (e.g. coke
production, ironmaking)
Establishment of a formal review period for review and evaluation of remediated areas of
the site
Utilization of the community as an important resource during the investigation and
cleanup of this site.
P
!
!
!
!
!
This Health Consultation was prepared by:
Carl Herbrandson, Ph.D.
Toxicologist, Site Assessment and Consultation Unit
Minnesota Department of Health
12
References
Agency for Toxic Substances and Disease Registry. (1994) Toxicological Profile for Polycyclic
Aromatic Hydrocarbons (PAHs). ATSDR, Atlanta, GA.
Barr Engineering, Inc. (1985) Plans Submitted Pursuant to Part IV and Part V, Task A to Exhibit
A March 26, 1985 Response Order by Consent. Report. Barr Minneapolis, MN. May 24,
1985.
Barr Engineering, Inc. (1986) Remedial Investigation Final Report and Appendicies. Barr
Minneapolis, MN. December 15, 1986.
United States Environmental Protection Agency, (1989) Memo Concerning: Draft comments on
the USX site Record of Decision. From: Norm Niedergang, EPA, Chicago, IL. To: Gary
Pulford, Minnesota Pollution Control Agency. August 30, 1989.
United States Environmental Protection Agency. (1997) Mercury Study Report to Congress.
EPA, Office of Air Quality Planning and Standards, Office of Research and
Development. EPA-452/R-97-003. December 1997.
Minnesota Department of Health. (1989) Health Assessment for St. Louis River Site, Duluth,
MN. MDH, St, Paul, MN. June 27, 1989.
Minnesota Department of Health. (1995) Contaminated Sediments: St. Louis River/U.S. SteelDuluth Works. MDH, St, Paul, MN. July 20, 1995.
Minnesota Department of Health, (1998) Memo Concerning: Personal USX site visit notes.
From: Carl Herbrandson, MDH, St. Paul, MN. To: USX File, April 22, 1998.
Minnesota Pollution Control Agency. (1989) Record of Decision. Declaration, Administrative
Record Index, Summary of remedial alternative selection. Gerald L. Willet,
Commissioner MPCA, St. Paul, MN. February, 22, 1989.
Minnesota Pollution Control Agency. (1995) Sediment sampling database, USX Site. MPCA St.
Paul, MN.
Minnesota Pollution Control Agency. (1997) Survey of sediment quality in the Duluth / Superior
Harbor: 1993 sampling results. Mary Schubauer-Berigan and Judy Crane MPCA, St.
Paul, MN. March, 1997.
14