West Lake Landfill

In 1939, a limestone quarry and crushing operations began at the site. Beginning in the early 1950s, as quarrying operations progressed, excavated areas were used as landfilling and disposal pits. Municipal solid waste, industrial wastes and construction and demolition debris were disposed in these areas. In 1973, around 8,700 tons of leached barium sulfate from the Manhattan Project, a World War II nuclear bomb development program, and other material from the Hazelwood Interim Storage Site was mixed with approximately 38,000 tons of soil and transported to West Lake Landfill. This soil and waste mixture was used for landfilling operations. Up to this point, all waste materials and radiologically impacted materials (RIM) were disposed at the site before state solid waste landfill regulations existed. Once state solid waste landfill regulations were implemented in 1974, the facility was permitted to continue landfilling operations on portions of the site.

In the mid-1970s, MoDNR and the Nuclear Regulatory Commission investigated reports indicating radioactive material had been transported to a local landfill. Initial site assessment and investigation results showed the uranium ore processing residues radiologically contaminated two of the former disposal areas at the site. Based on initial investigation results and the site’s past disposal of RIM and industrial wastes, the site was identified as a potential Superfund site under the Comprehensive Environmental, Response, Compensation and Liability Act of 1980 (CERCLA). CERCLA allows federal and state governments to clean up hazardous waste sites and seek reimbursement from responsible parties or to force responsible parties to perform the appropriate remedial measures. Other disposal areas at this site are identified in Superfund documents as the Former Active Sanitary Landfill (also known as the Bridgeton Sanitary Landfill), the Inactive Sanitary Landfill and the Closed Demolition Landfill. Bridgeton Landfill stopped accepting wastes Dec. 31, 2004, which was the last operating facility to receive sanitary waste at the site.

CERCLA cleanups follow a multi-phase process. After a site has gone through initial assessment and investigation, that information is used to evaluate the potential risks posed by the site. The Hazard Ranking System is used to numerically “score” the site. Sites that score at or above an established number of points qualify for cleanup under Superfund and are proposed for listing on EPA’s National Priorities List. As a result of historical assessments, EPA ultimately placed West Lake Landfill on the National Priorities List in 1990, making it a Superfund site.

Operable Units

In order to address contamination more effectively, EPA divided the site into three operable units (OUs). Each operable unit reflects areas which are expected to have different cleanup needs or area characteristics.

• OU-1: This operable unit consists of the former landfill areas containing typical sanitary landfill wastes and RIM transported from the Hazelwood Interim Storage Site (referred to as Area 1 and Area 2 in investigation reports). OU-1 also includes other property impacted by RIM residuals. Site investigations indicate RIM impact on two neighboring properties, identified as the Buffer Zone and Crossroads Lot 2A2.
• OU-2: This operable unit consists of former waste disposal areas that are not impacted by RIM. These disposal areas and expected contaminants were considered typical for solid waste landfills. 
• OU-3: This operable unit includes potential off-property groundwater impacts resulting from past permitted and unpermitted landfill operations at the site. 

Under EPA oversight, the responsible parties performed investigations of air, soil, sediment and groundwater contaminants and exposure pathways, which could pose current or future risk to human health and the environment. After assessing the potential risks, a health risk assessment was performed to determine if remedial action was needed. The health risk assessment uses current and predicted future land use scenarios on the property and in the immediate vicinity of the site to prepare remediation recommendations to protect the public and the environment.

OU-1

The potential contaminants of concern identified for the health risk estimate process include the following:

• Radiological contaminants: radionuclides within the natural decay series of uranium 238, uranium 235 and thorium 232 
• Inorganic chemicals: antimony, arsenic, barium, beryllium, chromium (+6), cobalt, lead, mercury, nickel, thallium, uranium (metal), vanadium and zirconium
• Pesticides and polychlorinated biphenyls (PCBs): aldrin/ dieldrin and PCBs frequently referred to by their former commercial product names (aroclor 1242, 1248 and 1254)
• Semi-volatile and volatile organic compounds: benzene, chlorobenzene, 1,1-dichloroethane, 1,4 dichlorobenzene, ethylbenzene, naphthalene, and pentachlorophenol

The results of OU-1 investigations and risk assessment concluded that potential exposures to on- or off-site workers or the public from radionuclides at the site are within or below EPA’s acceptable cancer risk range, based on current site use and conditions. Due to an expected future increase in radium-226 levels, resulting from decay of thorium-230, potential future risks to theoretical on-site storage yard workers, off-site building users to the north, and farmers to the north and west were projected to exceed EPA’s acceptable cancer risk range. Therefore, the risk assessment indicated remedial actions were appropriate to provide for long-term protection of public health from actual or threatened releases of hazardous substances into the environment.

OU-2

The potential contaminants of concern identified for the health risk estimate process include the following:

• Carcinogenic (cancer causing): arsenic, benzene, vinyl chloride
• Noncarcinogenic (non-cancer health impacts): chloride, fluoride, iron, manganese, total dissolved solids and total petroleum hydrocarbons

The streamlined investigation report and risk assessment for OU-2 concluded that using EPA’s presumptive remedy approach for municipal landfills was appropriate. The OU-2 record of decision includes using applicable sanitary landfill requirements to close the former municipal landfill sites in place. Two of the landfill areas are currently designated to be closed under MoDNR oversight, according to state solid waste landfill closure and permitting regulations. One area is designated to be closed under EPA oversight, according to federal and state requirements.

OU-3

OU-3 was discovered through information compiled from OU-1 and OU-2 investigations. Groundwater samples collected from monitoring wells located within both the unconsolidated Missouri River alluvial unit and the bedrock units, demonstrated potential site impacts to groundwater at and near the site. Based on initial assessment results, EPA concluded that a separate operable unit investigation was appropriate for investigating groundwater beneath and downgradient of OU-1 and OU-2 areas to assess the nature and extent of impact from past landfill operations. OU-3 contaminants of concern are being identified through the ongoing remedial investigation and associated risk assessment process. Well location surveys are being conducted as part of the OU-3 remedial investigation to locate nearby wells and determine potential current site-related risks to well users.

Following a remedial investigation and feasibility study, the agency with oversight responsibilities will recommend a preferred remedy and present the proposed plan for public comment. Following the public comment period, the agency with oversight responsibilities will decided on a final remedial action and issue a record of decision (ROD), explaining which cleanup alternatives will be used considering study results, public comments and community concerns. Each operable unit (OU) is proceeding through the cleanup process separately, with the focus of each OU described below. Work on each of these operable units is ongoing to finalize a plan to address potential site hazards. 

OU-1

The remedial investigation and feasibility study for OU-1 began March 3, 1993, when EPA signed the administrative order on consent. Following the required public notice and opportunity for comment, EPA decided on a remedial action and issued the ROD for OU-1 in May 2008. Based on additional information obtained after issuing the ROD, EPA determined the West Lake Landfill is not a typical municipal landfill due to the presence of radiologically impacted materials (RIM). Additional evaluation of remedial alternatives was appropriate. Through this review process, EPA determined an amendment to the original remedial action was needed for the remedy to be protective of human health and the environment.

In 2018, following the required public notice and opportunity for comment on the revised remedial plan, EPA issued an amendment to the 2008 ROD, explaining the amended remedy. The remedial actions for OU-1 include focused excavations (removing contaminated material containing RIM above eight-foot depth and specified radioactivity levels), capping (constructing an appropriate surface cover to prevent contact with remaining RIM and landfilled waste) and institutional controls on land use. These actions are designed to protect humans or other organisms from coming into contact with, or being harmed by, contamination at the site.

OU-1 is currently in the remedial design phase of the CERCLA process. EPA and the responsible parties agreed to add remedial design work to the existing settlement agreement, which was added through the May 6, 2019, third amendment to the administrative order on consent. The remedial design phase includes pre-construction site investigations and planning activities in preparation for remedial action at the site. Monitoring and safety planning are essential components of remedial design that evolve as the project moves into remedial action. For OU-1, the safety-planning document is referred to as the emergency response plan. The phases for design of the OU-1 remedy are outlined in section 6 of EPA’s statement of work, which is included in the amendment to the settlement agreement and order. OU-1 also requires preparing an excavation plan document, which describes how total radioactivity will be calculated to show conformity with requirements of the ROD. The remedial design plan will describe the boundaries of the planned excavation, how excavated material will be transported and the disposal method.

MoDNR and EPA continue to review additional documents submitted by the responsible parties. This agency review and approval process can take a substantial amount of time due to the size and scope of these documents. Links to site documents and data are provided in the Site Documents and Links tab.

OU-2

The remedial investigation and feasibility study phase for OU-2 began Dec. 14, 1994, when EPA signed the administrative order on consent. The remedial investigation report was revised in September 2005 and feasibility study report was revised in June 2006.  Following the required public notice and opportunity for comment, EPA decided on a remedial action and issued the ROD for OU-2 in July 2008.

EPA selected separate remedies for each disposal area and retained regulatory authority for the Inactive Sanitary Landfill. EPA deferred closure of the Bridgeton Sanitary Landfill and Closed Demolition Landfill to MoDNR for oversight under state regulatory authority. MoDNR’s Waste Management Program oversees closure and post-closure of former waste disposal areas. The final remedial actions were selected considering study results, public comments and community concerns. The remedy was selected with the intent to protect humans or other organisms from coming into contact with or being harmed by contamination typically found in municipal landfills.

OU-2 is currently in the remedial design phase of the CERCLA process. EPA and the responsible party agreed to add remedial design work to the existing settlement agreement, which was added through a third amendment to the administrative order, signed in 2008. The remedial design phase includes pre-construction site investigations and planning activities in preparation for remedial action at the site. The phases for design of the OU-2 remedy are outlined in EPA’s Oct. 7, 2008, OU-2 statement of work.

Interim Remedial Actions

On Dec. 23, 2010, the responsible party reported that the Bridgeton Sanitary Landfill was experiencing elevated temperatures in some gas extraction wells. Landfill extraction well gas testing indicated the presence of elevated hydrogen, carbon monoxide and reduced methane concentrations, which indicated the presence of an exothermic (heat-generating) subsurface reaction event in the South Quarry portion of the Bridgeton Sanitary Landfill. On May 13, 2013, the state of Missouri and Bridgeton Landfill entered into an order of preliminary injunction, to address the subsurface smoldering event. The agreed order included a phased sampling program in Bridgeton Landfill near Area 1 of OU-1, to identify potential locations for installing a barrier between RIM and the existing smoldering event. EPA later took the lead regulatory role in the investigation and approved the investigation results in April 2017. As a result of sampling during the investigation, the previously defined boundaries of Area 1 were expanded to include areas of RIM discovered during the interim action investigation. 

Following a brush fire on the property on Oct. 24, 2015, EPA ordered the responsible parties to perform a time-critical removal action. EPA signed the administrative order for removal action on Dec. 9, 2015, which resulted in installing a non-combustible landfill cover, additional site investigations to confirm RIM impacted areas were covered and other planning and reporting requirements. In September 2021, EPA concluded that all work required under this order had been fully performed, with the exception of any continuing maintenance, monitoring and reporting obligations.

The responsible party also developed a baseline air monitoring program as part of an EPA’s order on consent for removal action, dated April 16, 2014. In a follow-up order on consent for removal actions, dated  April 28, 2016, the responsible party implemented engineering controls within portions of the Bridgeton Landfill to prevent potential impacts to OU-1, Area 1. These controls included:

• Inert gas injection plan
• Installing ethylene vinyl alcohol cover over the north quarry area of Bridgeton Landfill
• Installing a system of temperature monitoring probes in the north quarry area of Bridgeton Landfill
• Installing a heat extraction system in the neck area of Bridgeton Landfill, based on the work plan document MoDNR conditionally approved Dec. 4, 2015
• Two sulfur dioxide ambient air monitors and monitoring for one year
• Action documents and reporting requirements, such as submitting monthly activity reports, monitoring results and a final action report when the action was complete

The required ambient air sulfur dioxide monitoring was completed Aug. 24, 2017. In August 2023, due to the stable conditions observed in the monitoring data, EPA approved a reduction in monitoring and reporting requirements. This approval provides for reinstating greater monitoring and reporting requirements if future observed subsurface conditions suggest increased heat generation within the landfill. Routine monitoring of subsurface conditions are being performed at the site. For more information about the Bridgeton Landfill events, visit the department's Bridgeton Sanitary Landfill webpage.

Off-site Monitoring

In addition to the EPA lead investigations, MoDNR and DHSS have performed air testing and data review to assess the potential impact on off-site human health. On Feb. 2, 2013, MoDNR and DHSS staff conducted radiological surveys and collected deposition dust samples near the site, using odor as a wind direction indicator. The upwind and downwind readings were compared for differences in radiological readings. From Nov. 4-6, 2015, MoDNR and DHSS staff conducted radiological surveying and sampling near West Lake Landfill. The investigation report was released in two phases, interim reports and final reports. The interim reports described the investigation and presented immediately available data. The final reports supplemented the interim report with laboratory sample results and investigation conclusions. Links to these reports and data are provided in the Site Documents and Links tab.

OU-3

OU-3 is currently in the remedial investigation and feasibility study phase of the CERCLA process, which began Feb. 6, 2019, when EPA signed the administrative order on consent. The respondents are performing groundwater investigations based on the EPA approved work plan. A risk assessment for OU-3 will be performed once the groundwater investigation has concluded.

The agencies and responsible parties involved are working to close out and delete this site from the National Priorities List, EPA’s list of the highest priority hazardous waste sites in the nation needing remedial investigation and cleanup actions.

OU-1

After the remedial design phase is complete, the following activities will occur:

• The parties will continue to negotiate a consent decree and settlement agreement for implementing and constructing the remedial action
• The remedial action phase will begin, which involves the actual construction or implementation phase of site radiological contaminant removal process
• Operation and maintenance of the remedial action will be initiated as remedial actions are implemented and completed
• Long-term stewardship will continue for institutional controls put in place to protect human health and the environment from radiological contamination that remains in OU-1 after radiological contaminant removal

Activity and use restrictions will be established to prevent future exposure risk from contamination remaining within the former landfills after partial removal of RIM wastes. The baseline risk assessment assumes the property will only be used for restricted industrial or commercial purposes in the future. Institutional controls on future land use are expected to limit excavations or other on-site activities, which could result in exposures to remaining landfilled materials. Based on this assumption, site redevelopment may be restricted for thousands of years.

OU-2

After the remedial design phase is complete, the following activities will occur:

• The parties will continue to negotiate a consent decree and settlement agreement for implementing and constructing the remedial action
• The remedial action phase will begin, which involves the actual construction or implementation of the remedy
• Operation and maintenance of the remedial action
• Long-term stewardship will continue for institutional controls put in place to protect human health and the environment from the waste that is left in place

Since disposed wastes will be left in place when the cap is installed, the remedy will include activity and use restrictions to ensure the cap is protected and unacceptable exposure to contamination does not occur in the future. As proposed in the baseline risk assessment, the potential future risk estimates assumed that the property will only be used for commercial and industrial purposes. Future activities in the OU-2 area will be limited according to regulatory use restrictions established by the final remedy. 

OU-3

If a remedial action is determined to be necessary after the remedial investigation and feasibility study phase is complete, the following activities will occur:

• Developing a proposed remedial plan, allowing for public review and comment before preparing the record of decision
• The parties will negotiate a consent decree and settlement agreement for planning, implementing and constructing the remedial action
• Developing a remedial design, followed by constructing and implementing the remedial action
• Operation and maintenance of the remedial system
• Closeout and removing the site from the National Priorities List
• Implementing long-term stewardship of institutional controls established to protect human health and the environment from contamination that remains after remedial action

The outcome of ongoing groundwater investigations will determine what action will be required in the future. Future actions will be documented in a record of decision when the investigation and feasibility study are complete.

The administrative record for the West Lake Landfill includes all documents and data used and produced to develop cleanup alternatives and support the remedy for the site. The record also includes the community involvement plan, site fact sheets and site updates. EPA maintains the administrative record in electronic files in a records collections webpage. To improve accessibility to information, EPA created a site dashboard to summarize site activities. The EPA dashboard contains interactive site maps providing boring and monitoring well locations. The EPA webpages offer links to reports and other documents which provide additional detail on information on this webpage. EPA's Westlake Landfill site documents and data webpage also provides links to final technical reports and other key project documents.

Reports, Data and Regulatory Documents

OU-1

• Administrative Order on Consent for Remedial Investigation/ Feasibility Study, Docket No. VII-93-F-0005, March 3, 1993 - EPA
• Proposed Plan: West Lake Landfill Site Operable Units 1 and 2, June 2006 - EPA
• Record of Decision: West Lake Landfill Site Operable Unit 1, May 2008 - EPA
• Unilateral Administrative Order for Removal Action, Docket No. CERCLA-07-2016-0002, Dec. 9, 2015 - EPA
• Proposed Record of Decision Amendment West Lake Landfill Superfund Site, Feb. 6, 2018 - EPA
• Record of Decision Amendment West Lake Landfill Site Operable Unit 1, September 2018 - EPA
• Third Amendment to Administrative Settlement Agreement and Order on Consent, Docket No. VII-93-F-0005, May 6, 2019 - EPA

OU-2

• Administrative Order on Consent for Remedial Investigation/ Feasibility Study, Docket No. VII-94-F-0025, Dec. 14, 1994 - EPA
• Remedial Investigation Report West Lake Landfill Operable Unit 2, Revised September 2005 - EPA
• Feasibility Study Report: West Lake Landfill Operable Unit 2, June 2006 - EPA
• Proposed Plan: West Lake Landfill Site Operable Units 1 and 2, June 2006 - EPA
• Record of Decision: West Lake Landfill Site Operable Unit 2, July 2008 - EPA
• Statement of Work Remedial Design West Lake Landfill Site Operable Unit 2, Oct. 7, 2008 - MoDNR
• Third Amendment to Settlement Agreement and Order on Consent, Docket No. VII-94-F-0025, Oct. 16, 2008 - EPA
• First Agreed Order of Preliminary Injunction, Case No. 13SL-CC01088, May 13, 2013 - MoDNR
• West Lake Landfill: Radiological Survey, May 16, 2013 - MoDNR
• Bridgeton Sanitary Landfill: Radiological Air Sampling, June 2013 - DHSS
• Administrative Settlement Agreement and Order on Consent for Removal Action - Preconstruction Work, Docket No. CERCLA-07-2014-0002, April 16, 2014 - EPA
• West Lake Landfill Vicinity: Radiological Survey and Sampling Nov. 4-6, 2015 Interim Report, January 2016 - MoDNR
• Bridgeton/ West Lake Landfill Radiological Sampling November 4-5, 2015 Interim Report, January 2016 - DHSS
• Administrative Settlement Agreement and Order on Consent for Removal Actions, Docket No. 07-2016-0005, April 28, 2016 - EPA
• Bridgeton/ West Lake Landfill Radiological Sampling November 4-5, 2015 Final Report, May 2016 - DHSS
• Health Consultation: Evaluation of Exposure to Landfill Gases in Ambient Air, Bridgeton Sanitary Landfill, Aug. 11, 2022 - DHSS

OU-3

• Administrative Settlement Agreement and Order on Consent for Remedial Investigation/ Feasibility Study, Docket No. CERCLA-07-2018-0259, Feb. 6, 2019 - EPA

Additional Information Sources:

• Administrative Records Collection: Westlake Landfill - EPA
• Bridgeton Landfill Reports and Updates - DHSS
• Bridgeton Sanitary Landfill - MoDNR
• Hazard Ranking System (HRS) - EPA
• Superfund: CERCLA Overview - EPA
• Superfund: National Priorities List (NPL) - EPA
• Superfund Cleanups - MoDNR
• Superfund Site Investigations - MoDNR
• Westlake Landfill Site Documents and Data - EPA
• West Lake Landfill Dashboard - EPA
• West Lake Landfill Documents - Nuclear Regulatory Commission

Contaminants of Concern