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Management of Air Releases



The Wisconsin Department of Natural Resources (DNR) requested advice from the Departmentof Health and Family Services (DHFS) regarding potential human health issues related to airreleases from investigations and remediation at the Ashland former manufactured gas plant(MGP). Environmental actions at former manufactured gas plants have caused airborne releaseselsewhere that adversely affected human health. The Ashland MGP site is very close to homesand an elementary school. Air management and action levels at the Ashland MGP site shouldfocus on benzene releases and be designed to protect both occupational and public exposures. DHFS recommends adjusting the perimeter and work zone action levels for volatile organiccompounds and adding monitoring of particulates. Compound-specific air sampling should beconducted along the perimeter when the worst contamination is encountered. Additionalparameters should be considered for worker zone air monitoring. A 24-hour telephone hotlineshould also be established to help address community concerns.


A manufactured gas plant (MGP) operated at 300 St. Claire Street, Ashland, Wisconsin, from the1880s until 1947. Environmental investigations in the 1990s revealed extensive contaminationfrom volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in theChequamegon Bay sediments, groundwater, and soils beneath Kreher Park. The former MGPsite is located on a clay bluff immediately above the park and is associated with contaminants insediments. In 1995, the Wisconsin Department of Health and Family Services (DHFS) evaluatedthe contamination at Kreher Park and concluded that SVOCs in Chequamegon Bay sedimentspose a public health hazard to people who come in contact with coal tar slicks released fromaffected sediments and recommended that people avoid direct contact with contaminatedsediments and tar slicks (1). In 1999, DHFS evaluated SVOCs in fish from Chequamegon Bay atKreher Park. DHFS found that SVOCs are not a health concern for people who eat these fishdaily (2). Current investigations at Kreher Park and at the former MGP site (currently owned byXcel Energy) are attempting to clarify the relationship between contamination at these locationsand the sources.

Contaminated soils, sediments, and groundwater at MGP sites typically contain a complexmixture of coal tars and inorganic wastes. Such coal tars are represented by 500 to 3000 separatesemi-volatile aromatic compounds of three to six benzene rings, phenolics, volatile aromaticcompounds of single and double benzene rings, and inorganic compounds of sulfur and nitrogen. Additionally, MGP oxide box wastes contain high concentrations of sulfoxides and metalcyanides. Contaminant conditions depends upon the location and method of disposal of MGPwastes, as well as the depth and confinement of perched water and groundwater aquifers atindividual sites. Coal tar contaminants in soils, sediments, and surface water at former MGPsites can be substantial and can represent a human health concern for people who come intodirect contact with the contaminants. Furthermore, the airborne releases of volatile chemicals arecommon when the affected media is uncovered at former MGP sites, for example, during siteexcavation and remediation.

The URS Corporation has proposed to search for a buried pipe in an area immediately adjacent tothe former MGP site, on the north side of St. Clare Street, which is owned by Xcel Energy (3).This investigation was estimated to take five days and was planned to start on September 17,2001. The work plan describes excavating a trench, up to 60 feet long and 10 feet deep, in orderto discover this buried pipe. The work might result in encountering non-aqueous phase liquids(NAPL) or pure products of MGP wastes. Such NAPL wastes, if encountered, will be stockpiledand disposed. Airborne releases are likely during the investigation. In anticipation, the URSCorporation work plan described air action levels for the work area. The URS on-site workerbreathing zone action levels for total VOC exposure durations greater than one minute are: (1)> 15 parts per million (ppm) - workers use respiratory protection; (2) > 75 ppm - increaseworker respiratory protection; and (3) > 150 ppm - halt site activities and exercise emissioncontrols. URS Corporation does not propose compound-specific action levels.


Investigations and remedial actions at former MGP sites have shown that air releases can besignificant and can adversely affect human health. Elsewhere in Wisconsin, DHFS hasresponded to odor and health concerns from people who live or work in homes and businessesadjacent to a MGP undergoing investigation and remediation. Many MGP sites have beenremediated without health complaints, even though strong odors have been released. However,MGP odor complaints and inhalation exposures have been linked to immediate reports of acute,but reversible, symptoms. In one instance, workers of a bank adjacent to a MGP site undergoingcleanup reported they breathed smelly air from the site and shortly afterwards developed headaches, sore throats, coughing, body aches, and headaches. Several of the bank employeesreported they soon after developed flu-like symptoms (fever and chills). At another site,employees of a commercial facility were exposed to dust and odors escaping from an adjacentthermal desorption process that was treating MGP waste soils. Several workers complained oftar odors, headaches, and an unpleasant taste in their mouth. Indoor air tests revealed thepresence of trace amounts of benzene, toluene, and unpermissible levels of xylenes. The sourceof the exposure was traced to the untreated MGP soil staging area and was blamed partly onunseasonably warm and windy conditions. Although a number of MGP remedial actions havebeen successfully undertaken over the past several years, health and environmental agencies inother states have reported similar inhalation exposures and subsequent health symptoms inpeople who worked or lived near the MGP sites undergoing an investigation or cleanup. Suchhuman health concerns may also be encountered during excavations and remediation at theAshland former MGP site.

DHFS recognizes that airborne releases and odor problems from investigative or cleanup actionsat MGP sites vary. Factors that affect these releases or problems include:

  1. encountering NAPL, coal tars, or pure MGP wastes;
  2. minimizing excavations to small-sized or limited, open face areas;
  3. ambient temperatures during excavation:
    1. cold weather-timed actions minimizes volatilization and airborne releases;
    2. cold weather-timed actions reduces non-worker exposures because windowsand doors in nearby homes are usually closed, and spectators are less likelyto spend time watching actions at the site;
  4. remote site location with no nearby homes or businesses resident or workers; and,
  5. rigorous air management actions.

A particular concern at the Ashland MGP site is the close proximity of homes and a school. Houses east of the Xcel Energy property are within 100 feet of the planned trench. Theplayground of Our Lady of the Lake Catholic School is within 200 feet of the planned trench.

The most malodorous compounds released during investigation and excavation of MGP sites arenaphthalene and sulfur-based compounds. Those compounds typically have odor thresholdconcentrations that are much less than concentrations known to cause human health effects. However, people with respiratory conditions tend to be more sensitive than the generalpopulation.

People with existing respiratory ailments can be affected by airborne releases from MGP-affectedmedia. In Wisconsin, nine percent of children and seven percent of adults suffer from asthma. Ten percent of older adults and five percent of all adults have emphysema or chronic bronchitis(4). Therefore, some nearby residents and students are likely to suffer from such respiratoryailments. Those individuals are the most sensitive to effects from airborne releases that cancome from planned actions at the Ashland Lakefront/NSP site.

Airborne releases from the investigation or remedial excavation of MGP sites often includesbenzene, a known human carcinogen and a sensitive trigger for air management. Consequently,MGP air management decisions and action levels should focus on the potential for a benzenerelease. The total VOC action levels proposed by URS are apparently intended to protectworkers, but are well above occupational exposure guidelines for benzene. For benzene, theACGIH time-weighted average (TWA) for benzene is 0.5 ppm, the NIOSH TWA is 0.1 ppm, andthe OSHA TWA is 1.0 ppm. Furthermore, the ACGIH 15 minute short-term exposure limit forbenzene is 2.5 ppm, and the NIOSH immediately dangerous to life or health limit is 500 ppm.

Where schools or homes are near a MGP work site, such as in Ashland, air managementconsiderations should consider public as well as occupational exposures. DHFS recommendsperimeter air monitoring in addition to worker breathing zone monitoring. Based on theoccupational guidelines, DHFS recommends the following preliminary action levels.

Preliminary Action Levels
URS Action Level(ppm) Recommended DHFS Action Level (ppm) Location Actions
-   15.0 total VOCs 0.1 total VOCs or 0.5 total VOCs perimeter   worker breathing zone worker breathing protection test for benzene initiate vapor control measures
worker breathing protection test for benzene initiate vapor control measures
-  -   150.0 total VOCs 0.5 total VOCs or 0.5 benzene or 5.0 total VOCs perimeter   worker breathing zone
worker breathing zone
halt site activities   halt site activities  halt site activities

ppm = parts per million

These preliminary DHFS action level recommendations take into consideration the closeproximity of nearby homes and the school, the small size of the area targeted for excavation, andthe short time frame planned for this investigation. Future MGP remediation action levels fromDHFS may be adjusted based on different circumstances or conditions.

Particulates should also be screened at the work area and at the perimeter because SVOCsadsorbed to particulates are an important route of distribution and human exposure. DHFSrecommends that the particulate action level be set at 1.0 milligram per cubic meter (mg/m3). Anexceedance of the particulate action level should initiate reduction of site activities andaggressive dust suppression.

Within DHFS, the Bureau of Environmental Health does not typically provide guidance onoccupational safety and protection measures. However, DHFS suggests that at MGP sitesundergoing remediation, the worker breathing zone is regularly screened for: (1) lower-explosivelimit; (2) carbon monoxide; (3) percent oxygen; (4) hydrogen sulfide; and (5) hydrogen cyanide. While significant releases of hydrogen cyanides are uncommon during the remediation of formerMGP sites, elevated metal-complexed cyanides are often found at such sites. Certainenvironmental conditions can exist at former MGP sites that allows release of hydrogen cyanide,and this calls for appropriate air monitoring.

Finally, when the investigators encounter product or NAPL conditions, air should be tested for afull screen of volatile organic compounds. Such quantitative data can provide valuableinformation that supplements the less sensitive data collected with handheld instrumentation. DHFS recommends upwind and downwind ambient air sampling that employs EnvironmentalProtection Agency methods TO-14 or TO-15, which uses Summa® canisters.

Public outreach is important prior to and during any MGP site remediation. This outreach avoidsproblems, alleviates concerns, answers questions, and addresses complaints. Public meetingsand fact sheets can improve the public's knowledge of anticipated odors and other air emissions,and as well as related issues. Special efforts should be made to identify and inform sensitivepopulations in the affected area. A 24-hour telephone number should be available to the publicand businesses so they can call with questions or complaints.


DHFS recognizes that children are especially sensitive to some contaminants. Children wereconsidered the most sensitive population when preparing in this health consultation. Childrenhave not been exposed to site-related contaminants, but because of the proximity of the proposedexcavation area to an elementary school, children could be exposed to contaminants at that time. The DHFS recommendations documented in this document are protective of children and youngstudents near the planned investigation site.


Environmental actions at former manufactured gas plants have caused airborne releases that canbe significant and can adversely affect human health. The Ashland MGP site is very close tohomes and an elementary school.


  1. Air management and action levels at the Ashland MGP site should focus on the potentialfor benzene releases.

  2. DHFS recommends preliminary action levels for managing releases of volatile organiccompounds and particulates. Worker zone air monitoring should include lower-explosivelimit, carbon monoxide, percent oxygen, hydrogen sulfide, and hydrogen cyanide. Quantitative air sampling should be considered when the worst contamination isencountered.

  3. In addition to the planned public outreach, a 24-hour telephone hotline should beestablished for the public.


  1. DHFS will continue to work cooperatively with DNR and the Ashland County HealthDepartment to ensure that public health concerns and issues are addressed about theAshland Lakefront/NSP site.

  2. DHFS will continue to respond to requests from the public and other agencies about the human health concerns and questions related to the Ashland Lakefront/NSP site.


  1. Memorandum from K Bro (Department of Health and Social Services) to J Dunn(Department of Natural Resources). Health Consultation on Exposure to Coal TarAssociated with the Manufactured Gas Plant site in the City of Ashland. October 23,1995.

  2. Agency for Toxic Substance and Disease Registry. Public Health Consultation - FishTissue Exposure Investigation, Contaminated Chequamegon Bay Sediments at KreherPark, Ashland, Wisconsin. Atlanta, GA: ATSDR. October 25, 1999

  3. URS Corporation. Correspondence to J. Dunn. Work Plan to Perform Pipe Investigation. Madison, WI: URS. August 17, 2001.

  4. Department of Health and Family Services, Bureau of Health Information. WisconsinFamily Health Survey - 1999. PHC-5281. Madison, WI: DHFS. July 2001.


Henry Nehls-Lowe, MPH
Bureau of Environmental Health
Division of Public Health
Wisconsin Department of Health & Family Services


This Ashland Lakefront/NSP public health consultation on Air Management Issues was preparedby the Wisconsin Department of Health and Family Services under a cooperative agreement withthe Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance withapproved methodology and procedures existing at the time the public health consultation was begun.

Gail D. Godfrey
Technical Project Officer, SPS, SSAB, DHAC

The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.

Richard Gillig

Table of Contents The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

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