IOWA CITY FORMER MANUFACTURED GAS PLANT SITE
IOWA CITY, JOHNSON COUNTY, IOWA
The Iowa Department of Public Health (IDPH) has prepared this Health Consultation at the requestof the U.S. Environmental Protection Agency (EPA) Region 7 office. IDPH was asked to evaluatewhether soil, air and water contamination at the Former Manufactured Gas Plant site in Iowa City,Iowa, poses a hazard to public health. The information reviewed in preparation of this HealthConsultation was current at the time of writing. Any future sampling data or other site-related information later forthcoming could alter the contents of this Health Consultation.
The Iowa City Former Manufactured Gas Plant (FMGP) site is located at 505 Burlington Street, inIowa City, Johnson County, Iowa. A coal gas production facility occupied the site from the mid-nineteenth century until the 1930's. In subsequent years, all coal gas production equipment wasremoved, and later the site was put to varied uses, including a utility company storage area and abus garage (1). The FMGP site lies in an extensively developed, mixed commercial and residentialarea. It is bounded on the north and east by single and multi-family residences, and on the south andwest by small commercial firms. According to the year 2000 Census, approximately 62,000 personsreside within the city limits of Iowa City, and about 2500 of these live within one square mile of the FMGP site (2).
In 1983, a three-story 54-unit apartment building, known as the Iowa-Illinois Manor, wasconstructed on land where the FMGP once stood. The apartment building occupies about half of the1.6 acre site; the remaining area is a concrete parking lot used by the approximately 150 tenants. Only small areas of landscaping and grass exist on-site. Tenants of the Iowa-Illinois Manor arealmost exclusively university students, from 19-21 years of age, with an average tenancy of 1-2years. According to apartment management, no small children have ever lived at the Iowa-Illinois Manor (1).
Contaminants of concern at this site include polyaromatic hydrocarbons (PAHs), volatile organiccompounds (VOCs) and various inorganic compounds which were used in the coal gasmanufacturing process. PAHs are formed during the partial combustion of organic material such ascoal, and these compounds are found at many coal gas manufacturing sites. VOCs are componentsof the light fraction of tar generated by coal gasification. VOCs such as benzene, toulene,ethylbenzene and xylene (BTEX) are typically found at former manufactured gas sites. Benzene isregarded as being the most hazardous of these compounds as it is a known human carcinogen. Leadand arsenic are also of concern at the FMGP site as they were sometimes used in coal gasmanufacturing process. Cyanide is also of potential concern as it was known to be used at the Iowa City FMGP (1).
Site investigations at FMGP have been ongoing since 1988. Several site assessments and sitecharacterizations have been undertaken since that time, the latest being completed in July 2001. Ahealth consultation for this site was completed in 1997 by the Iowa Department of Public Health. The 1997 health consultation concluded, based on available evidence, that the Iowa City FMGP siteposed no apparent public health hazard. (3).
Monitoring wells have been installed in the shallow aquifer underlying the site (10-20 feet below ground surface). Groundwater sampling conducted over the years has consistently demonstrated that site-related contaminants, principally PAHs and VOCs, are present in shallow groundwater (1). Most recent results from the 2000-2001 sampling indicate that benzene is present at concentrations ranging from non-detectable to 2800 µg/L and PAHs exist at levels ranging from non-detectable to over 8,000 µg/L (micrograms of contaminant per liter of water). However, no private wells exist in the area, and by law all single and multi-family residences within the city limits are connected to the Iowa City municipal water supply. That supply is obtained from the Iowa River at an intake approximately 1.5 miles up-gradient from the site, and from deep wells (~1500 feet) in the Jordan aquifer. No measurable amounts of contaminants that could have originated from the FMGP site have been found in either of these water sources (1).
PAH compounds were present in on-site surface soil (0-6") from non-detectable to 59 µg/kg (micrograms per kilogram of soil). The highest detection of PAH was found at an adjacent off-site location (460 µg/kg) but could be attributable to another source. BTEX compounds were not found in the on-site surface soil. The highest off-site concentration was benzene at 7.8 µg/kg. Highest amounts of lead and arsenic in surface soil on-site are 61mg/kg (milligrams per kilogram of soil) and 7.1 mg/kg, respectively (1).
Subsurface soil (6-10' interval) sampling revealed much more of contaminants that could be the result of past FMGP operations. Up to 125,000 µg/kg PAHs exist in this deeper soil layer. Benzene was found at concentrations as high as 10,200 µg/kg. Xylenes were present up to 44,900 µg/kg. Inorganic arsenic and lead were also detected in subsurface soils. Highest subsurface lead concentration onsite was 230 mg/kg; arsenic was found at a concentration of 23 mg/kg. Cyanide was also present in the subsurface zone at concentrations up to 625 mg/kg (1).
Residents of the apartment building have expressed concerns about possible health effects fromexposure to site-related contaminants (4-6). Of particular concern to these residents is the possibilityof vapors from subsurface soil contamination entering the apartment building. The BTEXcompounds are considered to be volatile, and it is possible for these compounds to evaporate fromcontaminated soil or water and exist as a vapor. These vapors can migrate through the soil and enterstructures such as apartment buildings which have been constructed over the contaminated soil. Airquality within Iowa-Illinois Manor has been tested several times, results are given in Tables 1 and 2.
Under the auspices of the Region 7 EPA, a community meeting was held in Iowa City on September8, 1999. The purpose of the meeting was to inform the public of ongoing site monitoring and toanswer any questions regarding the site. Attendees included one Iowa-Illinois Manor tenant,representatives of local government and responsible parties, and state and federal environmental staff (4-6).
|Date||Background||1st Apt.||2nd Apt.||3rd Apt.||Crawl Space|
|ATSDR EMEG*||12.8 µg/m3|
Concentrations given in µg/m3 (micrograms per cubic meter of air). These were 8-hour samples collected on the days indicated.
* Comparison values are concentrations of contaminants at or below which no adverse health effects would be expected to occur. The Environmental Media Evaluation Guideline (in this case, 12.8 µg/m3 for benzene) is an intermediate-level health-based concentration for continuous exposures lasting up to 364 days.
Concentration ranges for other volatile compounds measured within individual apartments at the Iowa-Illinois Manor were as follows: ethylbenzene, 1-5 µg/m3; toulene, 8.1-37 µg/m3; xylenes, 4-18 µg/m3. The intermediate-level comparison values for these compounds are 1000 µg/m3, 400 µg/m3, and 3040 µg/m3 for ethylbenzene, toulene, and xylene, respectively.
Concentrations given in µg/m3. 27 Oct-99 results were 8-hour samples collected on the days indicated; 16-Mar-00 results were 24-hour composite samples. Comparison values do not exist for many of the PAHs; however, the ATSDR intermediate-level comparison value for napthalene (a PAH) is 10 µg/m3.
There are no completed exposure pathways from inhalation of volatile compounds that mayinfiltrate through soil and enter the apartment building. Air quality monitoring has been conductedseveral times in crawl spaces and in individual apartments, and results indicate that concentrationsof BTEX and PAHs are not at levels sufficient to cause adverse health effects. None of the reportedconcentrations found within the Iowa-Illinois Manor apartments exceed ATSDR health-basedguidelines; in fact, concentrations of the volatile BTEX compounds, including benzene, were from4-20 times lower than established comparison values.
There are no completed current or future exposure pathways relating to ingestion of contaminatedwater at this site due to all residences being connected to the local municipal water supply. Themunicipal water supply has not been effected by contamination from the FMGP site. Furthermore, itis illegal to construct or use a private well within the Iowa City city limits, so future groundwateruse in the immediate vicinity of FMGP and the existence of possible human exposure pathways is not an issue.
Surface soils (0-6") from the site have not revealed any levels of contamination from PAHs, VOCsor metal compounds that should be of health concern. Reported concentrations of these compoundsare below health-based guidelines, for both long- and short-term exposures. Additionally, few areasof bare or potentially bare soil exist on-site. The overwhelming majority of the space is taken upwith the apartment structure and adjoining parking lot. Thus, contact with surface soil would be infrequent at best.
Subsurface soils do in fact contain high levels of site-related contaminants, primarily PAHs andVOCs. Exposure to these compounds at the high concentrations found underneath the FMGP sitewould result in a substantial health hazard. However, the depth of contaminants, generally in the 6-10 feet range, precludes human contact unless any excavations into the deeper soil zone (i.e, futureconstruction) are performed on-site. This scenario is unlikely since the area is already extensively developed.
Children's unique physiology and behavior can influence the extent of their exposure and thereforetheir susceptibility to hazardous chemicals. Children and adults may differ in their capacity to repairdamage from chemical assaults. Children also have a longer remaining lifetime in which to expressdamage from chemicals. And they are more likely than adults to misjudge possible environmentalhazards and less likely to avoid these hazards.
Based on available evidence, it is unlikely that children have been or are now being exposed tocontaminants from the FMGP site, either through ingestion or inhalation pathways. Highestconcentrations of site contaminants are found in the lower soil depths and are not accessible. Noprivate wells are in use and the municipal supply has not shown presence of any contaminants fromFMGP. Air in crawl spaces and in apartments within the Iowa-Illinois Manor shows noconcentrations of volatile compounds and PAHs that would be a health concern.
- Contamination at the Iowa City Former Manufactured Gas Plant site currently poses noapparent public health hazard.
Air quality testing within the Iowa-Illinois Manor apartment has not revealed any potential foradverse health effects to the tenants. Contaminated soil does exist, but at depths greater than six feet,and is not accessible unless extensive future excavations of on-site soil are undertaken.
- Re-evaluate need for further protective actions should any excavations be done at the site.
- Representatives from IDPH and EPA will participate in a public availability session for the FMGP site in Iowa City during February 2002. Copies of this health consultation will be made available to residents and local officials.
- Site Characterization Report for the Iowa City Former Manufactured Gas Plant Site.Prepared for Mid-American Energy Company, by Montgomery Watson Harza. Des MoinesIowa. Project No. 1911345.051801. Nov 2001.
- Data provided by State Library of Iowa Information Center. Des Moines Iowa. Jan 2002.
- Agency for Toxic Substances and Disease Registry. Health Consultation for Iowa CityFormer Manufactured Gas Plant Site. CERCLIS No. IAD 984591172. April 1, 1997.
- Iowa City Press Citizen. "EPA: Gas site poses no risks." Thursday September 9, 1999.
- The Gazette. "Final pollution tests set of Iowa City Site." Thursday September 9, 1999.
- The Daily Iowan. "Energy company monitors complex." Thursday September 9, 1999.
Hazardous Waste Site Health Assessment Program
Iowa Department of Public Health
ATSDR Regional Representative
Office of Regional Operations, Region VII
Office of the Assistant Administrator, ATSDR
ATSDR Technical Project Officer
Division of Health Assessment and Consultation
Superfund Site Assessment Branch
This health consultation was prepared by the Iowa Department of Public Health, Hazardous WasteSite Health Assessment Program, under a cooperative agreement with the Agency for ToxicSubstances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation began.
Technical Project Officer, SPS, SSAB, DHAC, ATSDR
The Division of Health Assessment and Consultation, ATSDR, has reviewed this healthconsultation, and concurs with its findings.
Chief, SPS, SSAB, DHAC, ATSDR