MASON CITY COAL EPA Region 7 08/26/2002 GASIFICATION PLANT City: Mason City County: Cerro Gordo County IOWA Other Names: Coal Gasification Plant EPA ID# IAD980969190 SITE DESCRIPTION The Mason City Coal Gasification Plant site is located on approximately 2 1/3 acres in a commercial and residential area of central Mason City, a north-central Iowa community of 29,000. Mason City Coal Gasification Plant operated from 1900 to 1951, and was demolished in 1952. An electrical substation and a small storage building are all that remain on the site. During a 1984 sewer installation, oily sludges were discovered in subsurface soil at the site. Investigations by the current site owner, Alliant Energy Corporation (formerly Interstate Power Company), revealed three underground storage tanks containing oily sludge. The tanks and contaminated soil were exhumed and stored on the southeast corner of the site and covered with a membrane cap. Contaminated soil is also present in the north-central portion of the site. The site is situated on fill material consisting of sand, gravel, and construction rubble and debris, and is in direct contact with bedrock. Although the level of the water table fluctuates seasonally, the water table in the fill material is typically present at depths ranging from 8 to 10 feet below the surface. A portion of the groundwater flows through the fill and empties into Willow Creek, which is used for public recreational fishing. Eight Mason City municipal drinking water wells are located within 2 miles of the site. Approximately 98 percent of Mason City is supplied by the municipal drinking water supply. Site Responsibility: NPL LISTING HISTORY This site is being addressed through Federal and „ „ , , . . „ .. , .. Proposed Date: 01/18/1994 potentially responsible parties actions. Final Date: 12/16/1994 ------- Deleted Date: THREATS AND CONTAMINANTS The soil, on-site waste pile, bedrock, and groundwater are contaminated with polynuclear aromatic hydrocarbons (PAHs). Soil samples collected indicate that the soil is contaminated to a depth of 13 1/2 feet. A series of investigations between 1986 and 1993 by Interstate Power Company identified high concentrations of PAHs in samples of groundwater taken from the uppermost aquifer and in samples of Willow Creek sediment downstream from the site. Ingesting or coming into direct contact with contaminated soil or groundwater could pose a public health threat. CLEANUP APPROACH Response Action Status Initial Actions: In late 1988, the potentially responsible parties excavated three underground storage tanks and surrounding contaminated soil, moved them to the southeast corner of the site, and covered them with a membrane cap. Excavation and thermal treatment of contaminated soil and the waste pile was completed in November 1996. Groundwater: In late 1991, the potentially responsible parties began investigating the nature and extent of site contamination. This study was completed in 1994. Periodic sampling of groundwater will continue for a minimum of two years following removal of the contaminated soils and the waste pile. A final cleanup remedy was selected in September 2000 to address groundwater contamination. The remedy selected was monitored natural attenuation of groundwater. Site Facts: Interstate Power Company signed an Administrative Order on Consent with the EPA in October 1991. Under this order, Interstate Power Company agreed to determine the extent of contamination at the site and assist the EPA in evaluating cleanup options. In 1995, Interstate Power Company, Kansas City Power & Light Company, Bob McKiness Grading and Excavating, Inc., and the City of Mason City signed an Administrative Order on Consent with EPA for removal of source materials and ------- post-removal groundwater monitoring. ENVIRONMENTAL PROGRESS The removal of contaminated soil and several storage tanks has made the Mason City Coal Gasification Plant safe while groundwater monitoring continues. The groundwater remedy at the site recognizes that natural attenuation of the contamination is occurring and is an acceptable remedy. Groundwater monitoring will be conducted for an extended period of time to verily the on-going effectiveness of this remedy. ------- SITE REPOSITORY ^ ^ Mason City Public Library Superfund Records Center 225 2nd Street S.E. 901 N. 5th St. Mason City, IA 50401 Kansas City, KS 66101 Mail Stop SUPR (913)551-4038 REGIONAL CONTACTS SITE MANAGER: Diana Engeman E-MAIL ADDRESS: engeman.diana@epa.gov PHONE NUMBER: (913)551-7746 COMMUNITY INVOLVEMENT COORDINATOR: Beckie Hiines PHONE NUMBER: (913)551-7003 E-MAIL ADDRESS: himes.beckie@epa.gov STATE CONTACT: Johanshir Golchin PHONE NUMBER: (515) 281-8925 MISCELLANEOUS INFORMATION STATE: IA 076B CONGRESSIONAL DISTRICT: 02 EPA ORGANIZATION: SFD-IANE/SUPR MODIFICATIONS ------- |