Missouri Risk-Based Corrective Action for Petroleum Storage Tank Sites: On-Site Landfarms - PUB2207

There are two general types of landfarms: off-site landfarms and on-site landfarms. Because of a decision between the Missouri Department of Natural Resources’ Water Protection Program and the department’s Environmental Remediation Program, the general permit for landfarms (MO-R401) will no longer be issued. This fact sheet will inform you about the requirement of constructing on-site landfarms only.

Landfarms that are operated off-site of the property on which a petroleum spill occurs will be required to obtain a site specific permit from the Water Protection Program. A land disturbance permit may be required for the construction of landfarms. Contact the Water Protection Program at 573-751-1300 for guidance or questions regarding a site specific landfarm permit or a land disturbance permit.

On-Site Landfarms

The Environmental Remediation Program will continue to provide oversight for any on-site landfarms, which do not accept waste from off-site sources regardless of owner. These on-site remedial actions will not be required to obtain a permit from the Water Protection Program, provided that these activities do not result in a discharge to waters of the state. In the event that a discharge is detected or contamination is found off-site, a site specific permit from the Water Protection Program is required. 

What types of contaminated soil can be landfarmed?

Only soils contaminated with gasoline, diesel fuel, fuel oil, kerosene or aviation fuel and having a TPH concentration of less than 2,500 ppm dry weight, may be placed in a treatment cell. This does not include soils contaminated with used oil, as described in 10 CSR 25-11.279. Find out more about resource recovery in the rules of the Department of Natural Resources located on the Secretary of State’s website.

What are the treatment cell requirements and specifications?

Treatment cell construction and operation shall comply with all guidelines and regulations of the Solid Waste Management Program, Air Pollution Control Program, Water Protection Program and Environmental Remediation Program.

Treatment cells shall be located within the property boundaries of the cleanup site.

The treatment cell shall not be located within a wetland, or the 10 year floodplain of a classified stream, as defined in 10 CSR 20-7.031

The treatment cell shall be located at least:

• 50 feet from property line
• 250 feet from any surface waters
• 500 feet from any caves, sinkholes, private water supply wells, lakes or intakes, and 1,000 feet from any public drinking water supply wells, lakes or intakes.

The treatment cell shall be surrounded by a two-foot berm to contain contaminated soils, stormwater and exclude water run-on.

The treatment cell shall be lined with a petroleum resistant liner or impermeable layer (see below).

• Contaminated soils shall be spread within the treatment cell to a depth greater than 18 inches but less than 24 inches to allow tilling without compromising the integrity of the liner.
• The treatment cell shall be limited to 5,000 cubic yards of soil from the on-site facility only.
• Discharge of stormwater from the treatment cell is not permitted. If discharge occurs, then a site specific landfarm permit shall be required through the Water Protection Program.

Can there be a stormwater discharge from the landfarm?

No, discharges to waters of the state are not permitted and are a violation of the Missouri Clean Water Law. The landfarm should be constructed so that the run-off from a 25 year, 24 hour storm event can be contained. In the event that a discharge is detected or contamination is found off-site, a site specific permit from the Water Protection Program may be required. 

How do I go about proposing a landfarm as a corrective action for my cleanup?

The corrective action plan should contain information regarding the landfarming of petroleum contaminated soils. This should include the following:

• The volume of soils to be landfarmed
• Analytical data from the soils to be landfarmed
• A description of the soil type and texture
• Grain size analytical data
• Submittal of all information of the tank closure or excavation activities
• A site map that shows where the cell will be located. This map should include any property boundaries, topography and slope, surface water bodies, wetlands, any existing stormwater runoff controls (i.e. berms, collection basins), planned runoff controls, and the 100 year floodplain.
• Cleanup levels should be stated
• A description of the sampling/monitoring plan. This should include the landfarm sampling locations, sampling type (grab or composite), the frequency of sampling, and the analyses to be performed.
• A soil application plan. This should include the native soil properties, the substrate preparation (i.e. compaction), under liner material, lift thickness, and tilling frequency, depth and method.
• Any bio enhancements that may be used. This would include the type of any nutrients and the rates of application (i.e. C:N:P ratio)
• Any additional stockpiled soil shall be placed on and covered by 12 ml plastic until it is placed in the landfarm. You must have Environmental Remediation Program approval before stockpiling additional soil. 

How must I construct the liner for my on-site landfarm?

The treatment cell shall be lined with a petroleum resistant or 12 ml plastic liner or a liner consisting of soils having a permeability coefficient of 10^-7 cm/sec or less with a compacted thickness of at least 12 inches. The liner shall be placed and maintained so as to form a seal that effectively keeps stormwater in the cell. A 12 inch layer of material (such as limestone fines, etc.) that will not tear the liner and have a discernable color difference from the petroleum contaminated soil being treated shall be placed on top of the liner. The petroleum contaminated soil will then be placed upon this. Any plastic liner shall be removed upon termination of the landfarm. 

What guidance is available for constructing a landfarm?

Chapter 5 from a technical bulletin for the construction of landfarms is available on the U.S. Environmental Protection Agency’s website.  

How do I terminate the on-site landfarm?

Soil removed from the land farm should be managed in accordance with the Missouri Risk-Based Corrective Action (MRBCA) for Petroleum Storage Tanks, Guidance - PUB2187. Since there are two versions of this guidance currently in use, information that explains which version of the guidance document would apply to your site, is available on the Department’s website.

Soil must be sampled and may be removed if it complies with the applicable Tier 1 Risk Based Target Levels (RBTLs) for the applicable land use and applicable exposure pathways. As an alternative to determining the appropriate RBTLs, the site owner may instead remediate soils to comply with the Default Target Levels (DTLs). If soil will be remediated to DTLs, confirmation sampling is still required prior to removing the soil from the landfarm. In either case, the site owner shall submit sample analysis along with the proposed end use to Water Protection Program and Environmental Remediation Program for approval prior to removal.

The sampling frequency shall be one composite sample per 100 cubic yards of soil and composed of soil from no more than four separate locations collected from depths no less than 12 inches.