The Moberly Former Manufactured Gas Plant (FMGP) site is located at 501 Franklin Street in the city of Moberly, Missouri. The address of the gas works, during its time of operation, was 509 Dameron Street. The geographic coordinates for the site are 39° 25' 21" north latitude and 92° 26' 26" west longitude. The site is approximately one acre in size and located within the Ameren Service Center. The entire service center encompasses approximately three acres and is located in a light commercial/residential area within the city limits of Moberly. An old alley separates the FMGP site from the rest of the Ameren service center on the west.
FMGP structures are still present at the site. The main gas plant building was still present in 2002 but has since been removed. The gas regulator station remains in the southeast comer of the site and is still in use for natural gas distribution. The governor house is still present, but not in use. The electric plant building in the center of the site is now used as a warehouse to store tools and equipment, including some power substation equipment for Ameren. Transformers and other electrical distribution equipment are stored in the open in several areas of the FMGP site. Structures associated with the production of gas are still present in the subsurface.
The Moberly FMGP was in operation as early as 1875 and continued until 1935. Gas production at the Moberly FMGP ranged from 6.5 million cubic feet in 1886 to 61 million cubic feet in 1929. Previous investigations reported that an estimated 120,000 gallons of coal tar was generated. Ownership of the site changed to Union Electric in 1983. Union Electric is now known as Ameren. The service center is currently used by Ameren for gas and electric service distribution.
EPA completed a Preliminary Assessment (PA) on the Moberly FMGP site on September 1991. The assessment found a potential for a release of site contaminants to groundwater due to former practices of burying tar and purifier wastes on-site. Circumstantial evidence indicated possible surface soil contamination. Additional site assessment was not conducted, and the site record was eventually moved to a list of archived sites in CERCLIS.
In 1999, the Missouri Department of Natural Resources (MDNR) Hazardous Waste Program initiated an Integrated Site Investigation/Removal Site Evaluation (SI/RSE) for the site and requested that EPA remove the site from its archived status. After the state initiated the SI/RSE, Ameren expressed its desire to conduct the invasive field activities on the site. Ameren conducted a sampling investigation of surface and subsurface soils, groundwater and surface waters under state oversight in 2000.
Analytical results documented the presence of coal tar residuals in surface soils throughout the site at concentrations above Superfund Chemical Data Matrix (SCDM) health-based benchmarks for soil exposure, Missouri Any-Use Soil Levels (ASL) and the EPA's Region 9 Preliminary Remedial Goals (PRGs) for Industrial Soil. High concentrations of carcinogenic polycyclic aromatic hydrocarbons (PAHs) were found in the northern portion of the site in the vicinity of the old gas plant building and the gas relief holder, where samples showed concentrations as high as 1,200 parts per million (ppm) benzo(a)pyrene. Coal tar was found in the subsurface in numerous places, including several subsurface structures. Highest concentrations of volatile organic compounds (VOCs) and carcinogenic PAHs were found in soil from the relief gasholder tank, where tar-saturated soil is present within two feet of the surface. Benzene was present at 152 ppm and benzo(a)pyrene was present at 3,000 ppm in a soil sample from that location.
Toxicity Characteristic Leaching Procedure (TCLP) analysis indicated soil within the gas relief holder tank is a characteristic hazardous waste based on the characteristic of toxicity for benzene. Soil that appeared to be saturated with coal tar was also visually observed in six of the soil borings during the SI/RSE sampling event. The investigation confirmed the presence of subsurface FMGP structures, some containing coal tar, and concluded that the soil in the vicinity of the below-grade tar handling structures was impacted by coal tar to a depth of approximately 20 feet
No release to ground water or surface water was found.
Following the state-lead investigation, Ameren agreed to enter into negotiations with the state to conduct removal activities under the state voluntary cleanup program. When Ameren and the state were unable to reach agreement on an enforcement Order, the site was referred to EPA by MDNR by letter dated June 27, 2005. An administrative record containing all relevant documents will be compiled for the Site.
Ameren has requested the opportunity to respond to Site conditions via the non-time-critical process. The EE/CA, dated February 2007, indicates the need for further response actions at the Site.
It is anticipated that EPA and Ameren will enter into a second AOC for implementation of the response action.
