Dense Nonaqueous Phase Liquids (DNAPLs)
- Policy and Guidance
- Chemistry and Behavior
- Environmental Occurrence
- Detection and Site Characterization
- Treatment Technologies
- Conferences and Seminars
- Additional Resources
Ex Situ Land Treatment
Land treatment units (LTUs) use naturally occurring soil microbes and sunlight to treat hazardous waste. This is accomplished by applying the hazardous waste directly on the soil surface or incorporating it into the upper layers of the soil in order to degrade, transform, or immobilize the hazardous constituents. LTUs rely upon the physical, chemical, and biological processes occurring in the topsoil layers to contain the waste. Because of this, the units are not required to have liner systems or a leachate collection and removal systems. Before hazardous waste can be placed in a LTU, operators must complete a treatment demonstration to demonstrate the unit's effectiveness and ability to treat the hazardous waste. Once operational, operators must monitor the unit (unsaturated zone monitoring) to ensure that all hazardous constituents are being treated adequately. Unit closure consists primarily of placing a vegetative cover over the unit and certifying that hazardous constituent levels in the treatment zone do not exceed background levels (U.S. EPA Web site).
4.13 Land Treatment
Remediation Technologies Screening Matrix and Reference Guide, Version 4.0.
Federal Remediation Technologies Roundtable, 2003
Brief overview of land treatment, including description, applicability, and limitations.
Bioremediation Using the Land Treatment Concept
D.F. Pope and D.E. Matthews.
EPA 600-R-93-164, 28 pp, 1993
Describes the use of land treatment technologies for the remediation of contaminated solid materials, the basic processes that drive land treatment applications, and the process parameters with respect to the efficiency or failure of the applications. Suggests design and operation criteria and identifies treatability, loading rates, and cleanup levels for contaminants commonly related to the wood preserving and petroleum industries.
Permit Applicant's Guidance Manual for Hazardous Waste Land Treatment, Storage, and Disposal Facilities (Final Draft)
U.S. EPA, Office of Solid Waste.
EPA 530-SW-84-004, 668 pp, 1984
Provides guidance on information needed for a permit application for different types of hazardous waste facilities, including a chapter on land treatment units.
Permit Guidance Manual on Unsaturated Zone Monitoring for Hazardous Waste Land Treament Units: Final Report
U.S. EPA, Office of Solid Waste and Emergency Response.
EPA 530-SW-86-040, 101 pp, 1986
Provides guidance on unsaturated zone monitoring at hazardous waste land treatment units and covers subjects such as soil-core and soil-pore-liquid monitoring; equipment selection, installation, and operation; sampling procedures; and data evaluation.
Project Summary: Evaluation of Volatilization of Hazardous Constituents at Hazardous Waste Land Treatment Sites
R.R. Dupont and J.A. Reineman.
EPA 600-S2-86-071, 10 pp, 1986
Presents the results of a laboratory study on the flux rates from soil of seven volatile constituents: benzene, ethylbenzene, p-, m-, o-xylene, and naphthalene.
Although coal tars and heavy oils tend to be resistant to biodegradation, land treatment of creosote wastes from wood preserving operations has been implemented at Superfund sites. The approach generally has been less successful in treating soils saturated with creosote than soils with residual levels. As with all land treatment remedies, a pilot treatability study is required to show that the waste can be degraded in a timely fashion.
Bonneville Power Administration Ross Complex, Vancouver, Washington
Within the 250-acre BPA Ross Complex lies the Wood Pole Storage Area East, a 4.2-acre site formerly used to store treated transmission poles before distributing them to points throughout the Pacific Northwest. Historically, these poles were treated off-site with PCP and/or creosote. While in storage, contaminants (heavy PAHs and PCP) dripped from the poles onto surface soils. PAHs were detected in soils from the surface to a maximum depth of three feet at concentrations as high as 193 mg/kg. PCP was detected as a surface contaminant, with the highest level detected at 140 mg/kg. The selected remedy for the Wood Pole Storage Area was ex-situ bioremediation with geochemical enhancements (UV light, ethanol, and hydrogen peroxide). The remedial action objectives or targeted cleanup level was 1 ppm MTCA Method A for PAHs and 8 ppm MTCA Method B for PCP. During the fall of 1994 a temporary treatment facility (tent) was erected and a total of 2,300 cubic yards of material was excavated and stockpiled. Soil treatments were concluded on November 30, 1995. Of the 2,300 cubic yards excavated from the pole yard, about 700 cubic yards failed to meet the targeted cleanup level even though contaminant levels were reduced by 80% for both PAHs and PCP. After treatment, this material was placed in thin layer in the southwest corner of the pole yard. A clean cap—6 inches thick and totaling 3,000 cubic yards—was then applied over the entire 4.2 acre pole yard. With completion of the clean gravel cap on January 8, 1996, there are no restrictions on surface use anywhere in the Wood Pole Yard. Institutional controls to prohibit digging will be maintained only for the southwest corner of the yard that contains the residual contamination.
Brown Wood Preserving, Live Oak, FL
Contact: (2007) David Keefer, 404-562-8932, email@example.com
The Brown Wood Preserving Superfund Site was operated by several different companies as a wood-treatment facility where creosote and PCP were used in pressure treatment processes. The removal activities involved the removal of ~15,000 tons of creosote sediments/sludge, treatment of 200,000 gallons of lagoon water, and the dismantling, decontamination, and disposal of the entire plant facility. The creosote sediments/sludge were shipped to the hazardous waste landfill in Emelle, AL. The removal cleanup criteria for the contaminated soils was 5,000 mg/kg total creosote substances. Contaminated soils exceeding certain lower contaminant levels (between 100 mg/kg TCICs and 5,000 mg/kg total creosote substances) were to be biodegraded in an on-site lined land treatment area (LTA), a 4-acre clay-lined area surrounded by earthen berms. The LTA has a one (1)% slope to the northwest where a subsurface drainage system drains out under the berm into a gravel lined swale that leads down to the retention pond. The clay for the liner came from the borrow pit which was subsequently shaped and clay lined to use as the retention pond for collection of water/leachate from the LTA. A 6-inch lift of contaminated soil from the on-site stockpile was added to the LTA approximately every three months, until all the contaminated soil was in the LTA. Confirmation soil sampling verified the achievement of the soil cleanup performance goal, with contaminant levels below 10 µg/kg in the LTA.
The site is located partially in the City of Baxter and partially in the City of Brainerd, MN. The Mississippi River flows about 3,000 feet east of the site. Burlington Northern operated a railroad tie treating plant on the site between 1907 and 1985. The process consisted of pressure treatment using a heated creosote/coal tar or creosote/fuel oil mixture. These compounds were detected in site soils and sludges. Based on the results of a 1984 bioremediation feasibility study, a full-scale land treatment system comprising a 4-foot base of clean backfill, a 100-ml high-density polyethylene liner, and a leachate collection system was constructed along with a lined staging area for temporary storage of sludge and contaminated soil. Between 1,100 and 1,500 cubic yards of soil were added to the treatment area each year, totaling 14,000 cubic yards of contaminated soils. About 7,000 cubic yards of soils were excavated from different parts of the site and placed in the treatment area. Performance standards for the soils treatment were based in part on significant reductions in total extractable hydrocarbons.
Due to time limitations of the earlier study, several years of full-scale treatment had been completed before it became evident that a "plateau" effect would limit the extent of biodegradation of the total extractable hydrocarbons. The rate of biodegradation of total extractable hydrocarbons continued only to a concentration that was slightly above the target treatment goal; hence, the target treatment goal for total extractable hydrocarbons could not be met. The performance standards also were based on a qualitative toxicity standard measured by the Microtox analysis, which indicated that the treated soil had not been rendered nontoxic, although significant reductions in toxicity were achieved. An evaluation of the monitoring data indicated that the residual creosote constituents were biostabilized despite the higher than expected residual total extractable hydrocarbon levels and toxicity levels. EPA and the MPCA decided to cap the treated material in place.