Solid Waste Management Program
Subsurface Smoldering Event - Bridgeton Sanitary Landfill
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Reinforced Concrete Pipes | Subsurface Smoldering Event | West Lake Landfill | Overview
Updated May 20, 2013
In April 2012, the Solid Waste Management Program contracted with landfill fire and slope stability technical experts, Stark Consultants Inc., Timothy D. Stark, PhD, principal, and Hammer Consulting Services, Todd Thalhamer, principal, to confirm the presence of a subsurface smoldering event at Bridgeton. The subsurface smoldering event reaction has caused increased odors to be generated from the decomposition of waste above the level expected through routine decomposition, rapid settlement - more than expected for waste decomposing at depth, heat in gas extraction wells and increased generation of various landfill gases including hydrogen. To date, all landfill data indicates the smoldering event is contained in the solid waste cell and has not impacted the adjacent radioactive cell.
This reaction, a subsurface smoldering event or smoldering fire, is a violation of Missouri’s Solid Waste Management Law and regulations. On July 23, 2012, the Solid Waste Management Program issued a notice of violation, or NOV, to Bridgeton/Republic for violating the section of the law (260.210.1.(4) RSMo) that prohibits the storage or disposal of solid waste in any manner that creates a public nuisance or adversely affects public health. Data provided by landfill staff indicated a subsurface smoldering event has and continues to occur in the landfill. The subsurface smoldering event has created odors that are migrating off-site and have resulted in numerous odor concerns. These odors continue to cause a nuisance. If emissions from the subsurface smoldering event are not controlled or conditions intensify further, these emissions could potentially pose a risk to public health. The department issued a Request for Proposal for air sampling and laboratory analytical services to evaluate current conditions as they change around the landfill. The department contracted with SWAPE LLC to conduct air sampling and laboratory analytical services to assist in collecting and evaluating the air quality and emissions surrounding the landfill property. (Photo of the comprehensive air sampling event.)
Bridgeton/Republic continues work to identify the materials causing the subsurface smoldering event. Currently, Bridgeton/Republic staff meets two or more times per month with the Solid Waste Management Program, St. Louis County Department of Health and/or the Pattonville and Robertson Fire Protection Districts. The meetings provide for review of any odor concerns received, analysis of Bridgeton/Republic’s corrective action measures including data such as well temperatures and leachate output, use of odor neutralizing agents, daily landfill cap inspections, upgrading of the methane gas collection system, leachate constituents and review and supplement of the facility’s operations and maintenance program and incident management plan. Additionally, these meetings provide for a review and assessment of the physical landfill property and odors.
Note: Landfill leachate is generated from liquids existing in the waste as it enters a landfill or from rainwater that passes through the waste within the facility.
The Missouri Department of Natural Resources ordered Republic Services, owner of the Bridgeton Sanitary Landfill, to research, plan, design and take corrective actions to address the subsurface smoldering event and associated odors. Republic Services has provided corrective action option plans for review and approval by the department. (See Construction Schedule website for links to these plans and associated documents.)
Once Bridgeton/Republic's plans are approved by the department, Republic Services is responsible for implementing 
those actions timely to address the subsurface smoldering event and associated odors being generated from their permitted facility.The department’s responsibilities consist of analysis of corrective action plans, requiring modifications, granting approval and performing oversight of such plans to ensure compliance by the property owner.
In addition, the department is requiring Republic Services to timely implement alternatives with consideration given to minimizing disruption to nearby residences and businesses surrounding the landfill. Republic’s experts and the department‘s experts continue to monitor the elevated temperatures within the compacted waste mass.
Temperature Monitoring Probes and Interceptor Well Plan
Bridgeton/Republic has installed temperature monitoring probes, or TMPs, for two purposes:
- As a way to track the movement of the subsurface smoldering event towards the narrow area of the landfill that lies between the North and South quarries.
- To monitor and determine the impact that the operation of the Gas Interceptor Well Plan has on the heat and gasses generated by the subsurface smoldering event.
Note: A temperature monitoring probe, or TMP, consists of thermocouples set in a vertical column every 20 feet in depth in the waste mass. The TMP then provides for measurement of subsurface waste temperatures.
To minimize or stop movement of subsurface heat from the South Quarry to the North Quarry, additional special purpose, interceptor gas wells are being installed by Republic Services Inc. There are two rows of gas interceptor wells. The first row of wells is planned approximately 50 feet north of the first line of temperature monitoring probes (TMPs 7R, 8, and 9). The second row of interceptor wells are being installed 50 feet north of the first row of wells, and staggered in between the first row of wells. The interceptor wells are specially designed gas extraction wells that operate to create a low pressure area vacuum curtain or “wall” that allows the landfill gasses and the heat associated with the subsurface smoldering event to safely be destructed through the landfill’s gas collection and control system. As designed, the gas interceptor well plan will result in temperatures at TMPs 7R, 8 and 9 continuing to rise as the heat and gasses move towards the interceptor wells. For this reason, it is expected the temperature range at these TMPs (7R, 8 and 9) will be outside the range normally encountered in a sanitary landfill. Additionally, TMPs are being placed to the 
north of the gas interceptor wells to monitor and determine if heat passes through the gas interceptor wells. (See map of TMPs and gas interceptor well locations. Photo: Top photo included in the TMP section is of gas interceptor wells and the second photo above is a gas interceptor well in the foreground and a row of TMPs in approximately the center of the picture.)
Based upon landfill-specific operating parameters, listed in the Clean Air Act’s New Source Performance Standards and the department’s experience overseeing landfills, the following values are considered guidelines for interpreting temperature data.
| Normal operating temperature | <131 degrees Fahrenheit |
High operating temperature (Clean Air Act requires additional extraction well monitoring to be conducted within this range) |
>131 degrees Fahrenheit to ~160 degrees Fahrenheit |
Temperature range not normally encountered |
>200 degrees Fahrenheit |
- Bridgeton Sanitary Landfill - Temperature Monitoring Probe Installation Plan. (9/14/12)
- Bridgeton Sanitary Landfill – Expanded Temperature Monitoring Probe and Gas Interceptor Well Installation Plan. (2/6/13)
- Bridgeton Sanitary Landfill – January Temperature Monitoring Probe Report. (1/15/13)
- Bridgeton Sanitary Landfill – February Temperature Monitoring Probe Report. (2/27/13)
- Bridgeton Sanitary Landfill - March Temperature Monitoring Probe Report. (4/5/13)
- Bridgeton Sanitary Landfill - April Temperature Monitoring Probe Report. (5/7/13)
- Bridgeton Sanitary Landfill - Weekly Temperature Monitoring Probe Report to 5/9/13. (5/14/13)
- Bridgeton Sanitary Landfill - Gas Interceptor Well Temperature Report 4/8/13 to 4/23/13. (5/7/13)
- Bridgeton Sanitary Landfill - Weekly Gas Interceptor Well Temperature Report to 5/12/13. (5/14/13)
Other Information about Landfill Subsurface Smoldering Events and Fires
Federal Emergency Management Agency United States Fire Administration National Fire Data Center:
