Cost and Performance Report: Land Treatment at the Scott Lumber Company Superfund Site Alton, Missouri

Table of Contents

• Executive Summary
• Site Information
• Matrix Description
• Treatment System Description
• Treatment System Performance
• Treatment System Cost
• Observations And Lessons Learned
• References
• Appendix A-Treatability Study Results

Preparation of this report has been funded wholly or in part by the U.S. Environmental Protection Agency under Contract Number 68-W3-0001. It has been subject to administrative review by EPA headquarters and Regional staff and by the technology vendor. Mention of trade names for commercial products does not constitute endorsement or recommendation for use.

Executive Summary

This report presents cost and performance data for a land treatment application of contaminated soil at the Scott Lumber Company Superfund site (Scott Lumber), located near Alton, Missouri. From 1973 to 1985, this company operated a wood treating facility that preserved railroad ties with a creosote/diesel fuel mixture. As a result of these operations, soil at the site was contaminated with polynuclear aromatic hydrocarbons (PAHs), which were major components of the creosote/diesel mixture used at Scott Lumber.

An Action Memorandum was signed on July 10, 1987, which specified the construction and operation of a land treatment unit (LTU) as a removal action for treatment of PAH-contaminated soils at the site. Contaminated soil was excavated and stockpiled on site. Land treatment was performed from December 1989 through September 1991, and approximately 15,960 tons of soil were treated in the LTU. The soil in the LTU was cultivated and irrigated on a weekly or biweekly basis. Ammonium phosphate fertilizer was added to the first lift to adjust the nutrients in the soil. No nutrient adjustments were made to the second lift. Site demobilization was completed in September 1991.

Action levels established by EPA for soil at the site were 14 mg/kg for benzo-a-pyrene (BAP) and 500 mg/kg for total PAHs.

Land treatment at the Scott Lumber site reduced levels of both BAP and total PAHs to below the soil action levels. In Lift 1, BAP concentrations were reduced from 16 to 8 mg/kg, and total PAH concentrations were reduced from 560 to 130 mg/kg. The most rapid decreases in total PAH concentrations in Lift 1 occurred within the first 6 weeks of treatment. In Lift 2, concentrations were reduced from 23 to 10 mg/kg for BAP and from 700 to 155 mg/kg for total PAHs. The land treatment system was operated for 6 months for Lift 1 and 3 months for Lift 2.

The total removal action costs were approximately $4,047,000, including approximately $1,292,000 in costs incurred by the land treatment contractor.

Table of Contents | Forward to Site Information

Site Information

Identifying Information

Scott Lumber Company Superfund Site
Alton, Missouri
CERCLIS #: MOD068531003
Action Memorandum Date: 7/10/87

Treatment Application

Type of Action: Removal Action
Treatability Study Associated with Application? Yes (see Appendix A)
EPA SITE Program Test Associated with Application? No
Operating Period: 12/89 - 9/91
Quantity of Soil Treated During Application: 15,961 tons

Background

Historical Activity That Generated Contamination at the Site: Creosote wood treating
Corresponding SIC Code: 2491B (Wood Preserving Using Cresote)
Waste Management Practices That Contributed to Contamination: Surface Impoundment/Lagoon; Spill

Site History: The Scott Lumber Company Superfund (Scott Lumber) site is located within Oregon County in south-central Missouri, approximately one mile east of the town of Alton, Missouri, as shown in Figure 1.

From 1973 until 1985, Scott Lumber operated a wood treating facility that preserved railroad ties with a creosote/diesel fuel mixture. A plan view of the site is shown in Figure 2.

Figure 2. Plan View of SLC Site [4]

The process consisted of treating wood using several retort tanks. Waste management practices at the site included discharging creosote contaminated sludge generated during the wood treatment process to an unlined storage lagoon located on site. In addition, an estimated 300 or more gallons of preservative were released during one spill incident, and the direct discharge of creosote waste into the soil was suspected. The creosote sludge was classified as a K001-listed waste by EPA. [1]

Site investigations conducted by EPA indicated that the site was principally contaminated with polynuclear aromatic hydrocarbons (PAHs), which are the major components of the creosote/diesel mixture used in the wood preserving operations. Most of this contamination was located within or near the wood treatment area of the site. [1]

Three phases of cleanup activities were conducted at Scott Lumber in response to a July 10, 1987 Action Memorandum. Phase I occurred in 1987 and involved the decontamination and removal of surface debris and sludge at the site. Phase II occurred from July to September 1988 and involved the excavation and stockpiling of contaminated soil identified at the site. Phase III occurred from 1989 to 1991 and involved the on-site land treatment of contaminated soil. [1] This report focuses on Phase III of the cleanup activities.

Regulatory Context: Action levels for the soil at the site were established by EPA and approved by the Agency for Toxic Substances and Disease Registry in 1987. The action levels were 14 mg/kg for benzo-a-pyrene (BAP) and 500 mg/kg for total PAHs. [1,2]

Total PAHs refer to the 16 constituents listed in Appendix B of this report.

Remedy Selection: Three methods were considered for remediation of PAH contamination at the site: 1) excavation and off-site disposal; 2) encapsulation with on-site disposal; and 3) land treatment. On-site land treatment was determined to be the best alternative because it was the most cost-effective method for permanently eliminating the identified contaminants at the site, and it was an innovative treatment technology. [2,4]

Site Logistics/Contacts

Site Management: Fund Lead

Oversight: EPA

On-Scene Coordinator: Bruce A. Morrison
U.S. EPA - Region 7
Emergency Planning and Response Branch
25 Funston Road
Kansas City, Kansas 66115
(913) 551-7755

Treatment System Vendor: Christina Cosentini
Remediation Technologies, Inc. (ReTeC)
1001 S. 24th Street W., Suite 105
Billings, Montana 59102
(406) 652-7481

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Matrix Description

Matrix Identification

Type of Matrix Processed Through the Treatment System: Soil (ex situ)

Contaminant Characterization

Primary Contaminant Group: Polynuclear Aromatic Hydrocarbons (PAHs)

PAHs were found in the water and sludges of the unlined storage lagoon and soil at the site. PAH concentrations were measured as high as 0.326 mg/kg in lagoon water, 12,400 mg/kg in sludge, and 63,000 mg/kg in soils. [4]

Concentrations for individual PAHs in untreated soils, prior to excavation, are shown in Table 1.

Table 1. Containment Characterization [4]

Matrix Characteristics Affecting Treatment Cost or Performance

The major matrix characteristics affecting cost or performance for this technology and the values measured for each are presented in Table 2. A particle size distribution of soils at Scott Lumber, using U.S. standard sieves, is shown in Table 3.

Table 2. Matrix Characteristics [9]

Table 3. Particle Size Distribution [9]

Site Geology/Stratigraphy

Unconsolidated soils near the ground surface primarily consist of a cherty clay interspersed with dense clay. Chert is a biochemical rock that consists of fibrous chalcedony, quartz, and silica. The total thickness of the unconsolidated soils that overlie the area's porous limestone is not known. [4]

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Treatment System Description

Primary Treatment Technology Type

Land Treatment

Supplemental Treatment Technology Types

None

Land Treatment System Description and Operation

Construction of the land treatment unit at Scott Lumber began in 1989 and involved the following activities:

• Site Preparation;

• Construction of a clay liner in the land treatment area;
• Construction of berms, run-on swales, monitoring wells, and lysimeters around the land treatment area;
• Installation of a subsurface drainage system in the land treatment area;
• Construction of a water retention pond; PLI Installation of an irrigation system for the land treatment area;
• Construction of a fence around the land treatment area;
• and PLI Placement of contaminated soil in the land treatment area.

The locations of the land treatment area, contaminated soil stockpile area, and water retention pond, as well as the subsurface drainage layout, are shown on Figure 3.

Figure 3. LTU at Scott Lumber [1]

Site preparation activities included removing three buildings from the proposed land treatment area and relocating sawdust and scrap wood debris at the site prior to regrading the surface topography. While regrading, a new area of subsurface creosote-contaminated soil, approximately 100 feet in diameter, was discovered near what was once the retention pond.

Approximately 5,000 tons of contaminated soil were excavated from this area and added to the stockpile of soil to be remediated. The area was backfilled with clean fill material. [1,2]

Construction of a clay liner in the land treatment area involved the compaction of the top 1 foot of in-situ soil and the addition of a compacted 2-foot clay layer. The in-situ and fill clay layers totaled 3 feet. To inhibit fluid permeability within the clay layers, the compacted clay surface was broken up and loosened between placement of 6-inch lifts, and soil moisture was maintained at 1% to 4% greater than the optimum determined by the Modified Proctor Test. Perimeter berms were constructed around the LTU to the same specifications as the clay liner. [1,2]

An underdrain system was constructed above the clay layer to collect and drain water to a retention pond. The system consisted of a 9- to 10-inch thick sand layer containing a drainage pipe network consisting of HDPE perforated pipe 1.5 inch thick by 12 inches wide wrapped in a geotextile membrane. The HDPE pipe was connected to 6-inch header pipes placed within the top 6 inches of the clay liner. These header pipes were also perforated and drained to the retention pond. Each header pipe was surrounded by gravel backfill and covered with a geotextile membrane. Figure 3 shows the subsurface drainage network within the LTU. [1 and 2]

A retention pond was constructed in the southeast corner of the LTU to receive the potentially contaminated LTU runoff water collected by the underdrain system. It was lined with a 40-mil HDPE liner that overlay a 3-inch sand cushion, and had a storage capacity of approximately 1 million gallons. When the capacity of the retention pond was exceeded during rainy periods, excess water was discharged to the Alton Wastewater Treatment Plant located adjacent to the site.[2]

A 2- to 4-inch layer of topsoil was placed on top of the underdrain layer to guard against tilling damage and to decrease the leaching potential of contaminated soil. A cross section of the LTU, showing the location and thickness of individual soil layers, is presented in Figure 4. [2]

Figure 3. LTU Cross Section [2]

LTU Operation
Contaminated soil from the stockpile area was placed in the LTU in 2 lifts. The first lift was placed into the treatment area in December 1989, and treatment occurred from May to November 1990 (6 months). This lift consisted of approximately 9,000 tons of soil and averaged 9 inches in thickness. The remaining stockpiled soil was placed on the LTU in December 1990 and May 1991, and treatment of the second lift occurred from May to August 1991 (3 months). The second lift consisted of approximately 7,000 tons of soil and averaged 7 inches in thickness. [1 and 2]

After the first lift of soil was placed in the treatment area, a portable irrigation system was installed. The irrigation system consisted of a 4-inch aluminum pipe placed along the base of the southern LTU berm. Water was pumped from the retention pond, through this line, to a moving wheel lateral line. The lateral line was manually rolled east to west at 40-foot intervals along the southern berm pipe, and water was distributed to the LTU from the lateral line through impulse sprinkler heads spaced every 40 feet. During the summer months, the LTU was irrigated approximately once a week. [2] The irrigation activities for the first lift began during the first week of June 1990, and for the second lift during the third week of May 1991. [8]

Following placement of each lift in the LTU, large rocks and debris were removed from the contaminated soil, utilizing an alternating series of cultivating and rock and debris collecting activities. Cultivation broke up the soil and brought rocks, wood, and other debris to the surface, where they were collected with a tractor-mounted Anderson Rock Picker. The rocks and debris collected that were greater than 3 inches in length were placed in a designated stockpiling area for segregation and decontamination. [2] The tilling activities for the first lift began during the first week of June 1990, and for the second lift during the third week of May 1991. [8]

Treatability study results indicated that sufficient indigenous microorganisms existed in the soil at this site to support biodegradation. [4] Approximately 200 pounds per acre of granular, ammonium phosphate fertilizer was applied to the first lift to obtain a ratio of soil organic content to nitrogen to phosphorus of 100:2:0.4. No nutrient adjustments were necessary for the second lift. [2]

Each lift was cultivated to aid the aerobic bioremediation process. The soil was cultivated using farm equipment (chisel plow, tiller, or subsoil ripper) for specific soil conditions. For example, the subsoil ripper was used to break up thick, compacted, silty clays, and the chisel plow was used for routine soil cultivation. Each lift was cultivated approximately once a week while rock and debris removal was occurring, and twice a week when no rock and debris removal took place. [2]

Soil samples collected in October 1990 indicated that total PAH concentrations were approximately 130 mg/kg and BAP concentrations were approximately 8 mg/kg and treatment of Lift #1 was complete. Treatment of Lift #2 was completed in August 1991, and final concentrations were reported to be 155 mg/kg for total PAH and 10 mg/kg for BAP. Site closure was completed in the autumn of 1991; activities included the disposal of debris at the Butler County landfill, regrading portions of the site, seeding and fertilizing the site, and demobilizing office trailers and equipment. [1]

Health and safety requirements for this operation included compliance with the permissible exposure limit for PAHs set by the Occupational Safety and Health Administration.

Groundwater Monitoring
Groundwater monitoring was conducted throughout operation of the LTU. The groundwater monitoring program was conducted to detect any migration of PAHs from the LTU to the groundwater. Four shallow groundwater monitoring wells screened between 30 and 35 feet below ground surface were installed in each corner of the LTU. Two deep monitoring wells screened between 95 and 100 feet below ground surface were installed in the northwest (upgradient) and southeast (downgradient) corners of the site. Shallow wells were based on the depth to the groundwater, while deep wells were based on depths of nearby private wells.[8]

Before placement of the compacted 2-foot clay layer, four groundwater lysimeters were installed inside the perimeter berms to monitor contaminant migration through the clay liner. To minimize the development of a migration route, the lysimeter collection tubes were laterally trenched to locations outside the LTU. [2]

Operating Parameters Affecting Treatment Cost or Performance [1,2]

The major operating parameters affecting cost or performance for this technology and the values measured for each during this treatment application are listed in Table 4.

Table 4. Operating Parameters [1,2,9]

Timeline [1,2,6]

The timeline for this application is presented in Table 5.

Table 5. Timeline [1,2,6]

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Treatment System Performance

Cleanup Goals/Standards

Action levels for the soil at the site were established by EPA. The action levels were 14 mg/kg for benzo-a-pyrene (BAP) and 500 mg/kg for total PAHs. [1 and 2] Total PAHs refers to the 16 PAH constituents listed in Appendix B to this report.

Additional Information on Goals

Action levels for soil at the site were based on McClanahan's relative carcinogenic risk of BAP compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin, as well as action levels previously approved by the Agency for Toxic Substances and Disease Registry for cleanup of soil at similar sites. [2]

Treatment Performance Data

Between April and November 1990, EPA collected soil samples from a 5,000-square foot subplot within Sampling Area F shown on Figure 5.

Figure 5. Sampling Locations [1]

This subplot measured 50 feet north/south by 100 feet east/west and was located on the east side of Sampling Area F. Three 50-ml aliquot samples were collected every two weeks during treatment of the first lift from quadrants north, south, and east. These samples were analyzed for total PAHs by GC/MS analytical Method 3230.2A, an EPA Region 7 modification of a CLP analytical method for extraction and analysis of water and solids for semivolatile organic compounds. [7] Samples were collected within Sampling Area F because it was conveniently located near the decontamination and office areas, was out of the way of most facility operations, and the marker flags placed within the subplot could be lined up with permanent markers on the adjoining berm. [2 and 5]

The individual PAH analytical results by sample date for Lift #1 are presented in Appendix B by subplot location. Average concentrations were calculated for each PAH constituent measured in the three Subplot F quadrants, as shown in Appendix B, by sample date. Total PAHs were calculated for each sample date by summing the analytical results for all 16 PAH constituents shown in Appendix B. The averages of the total PAH concentrations were calculated and plotted against each sample date, as shown in Figure 6, and average BAP concentrations were plotted against each sample date, as shown in Figure 7.

In Lift #2, concentrations were reduced from 23 to 10 mg/kg for BAP and from 700 to 155 mg/kg for total PAH. Initial BAP and total PAH concentrations for Lift #2 were collected in May 1991. [1]

Figure 6. Total PAH Concentrations During Treatment of Lift No. 1 (based on Appendix B)

Figure 7. BAP Concentration During Treatment of Lift No. 1 (based on Appendix B)

Groundwater monitoring was conducted on a quarterly basis during operation of the LTU. No data are available on the results of groundwater monitoring.

During initial soil loading and LTU system start-up, air monitoring of PAHs was conducted using NIOSH Method 5515. Gilian pump monitors placed on equipment used during the cultivating and loading operations detected airborne PAHs at concentrations as high as 6.8 g/m3 during an 8-hour sampling period. [2]

Performance Data Assessment

A review of analytical data for treatment of soil in Subplot F of Lift No. 1 indicated that average total PAH concentrations decreased from 560 to approximately 130 mg/kg within 6 months of treatment, and the average BAP concentration decreased from 16 to approximately 8 mg/kg in the same time frame. A rapid decrease in average total PAH and BAP concentrations occurred within the first six weeks of the treatment, when the average total PAH concentration decreased from approximately 560 to 190 mg/kg, and the average BAP concentration decreased from approximately 20 to 12 mg/kg. The action level for total PAH was reached after a few days of treatment, and, for BAP, within the first 6 weeks of treatment.

A review of the analytical data for a 3-ring PAH (phenanthrene) shows a reduction from 65 to 5 mg/kg (92%) over a 6-month time frame, while data for a 5-ring PAH (indeno(1,2,3-cd)pyrene) shows a reduction from 19 to 6 mg/kg (68%) over the same period. These data show that biodegradation is faster for PAH constituents with fewer benzene rings (in this case, biodegradation for phenanthrene was faster than for indeno(1,2,3-cd)pyrene).

A review of air monitoring data for PAHs indicated that the maximum concentration measured was less than the permissible exposure limit set by the Occupational Safety and Health Administration.

Performance Data Completeness

Soil samples were collected during treatment of a small area that represented slightly greater than 1% of the total LTU area.

Subplot F was sampled on a 2-week basis during treatment of the first lift to monitor treatment performance. Soils in Lift No. 1 were assumed to be homogeneous with respect to PAH concentrations. Subplot F was selected for sampling because of ease of accessibility, proximity to the decontamination area, and the ability to leave marker flags on the subplot.

Constituent-specific analytical data for the 16 PAHs of interest during this cleanup are only available for treatment of the first lift.

Performance Data Quality

Laboratory analytical data are accompanied by statements certifying that the data have met all quality assurance requirements unless otherwise indicated in the data packages. Duplicate samples were collected from each quadrant and are included in each data package. [6]

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Treatment System Cost

Procurement Process

The removal activities at Scott Lumber were financed by EPA. EPA contracted Remediation Technologies, Inc. to conduct the land treatment activities at the site. [1]

Treatment System Cost [1]

Total removal action costs at Scott Lumber were approximately $4,047,000. Because little information was provided on the specific elements included in these costs, a breakdown of these costs into the elements of an interagency Work Breakdown Structure (WBS) was not completed at this time. Actual costs for treatment activities (i.e., those incurred by the land treatment contractor) are shown below by year:

The $1,292,000 in total costs for treatment activities corresponds to approximately $81/ton of soil treated, for the 15,961 tons of soil treated in this application.

Additional costs at Scott Lumber were incurred by the ERCS contractor ($1,666,000); TAT ($207,000); EPA Direct ($187,000); EPA Indirect ($395,000); laboratory analyses - CLP ($254,000); and ERT/ERU ($46,000).

Cost Data Quality

Total cost information was provided by the EPA On-Scene Coordinator (OSC) for this project, and includes cost for several activities. The specific cost elements included in each activity are not available at this time.

Vendor Input

Costs for similar operations were estimated by the treatment vendor to range from $50 to $100 per cubic yard of soil treated for quantities in excess of 3,000 cubic yards [21]

Back to Treatment System Performance | Table of Contents | Forward to Observations and Lessons Learned

Observations And Lessons Learned

Cost Observations and Lessons Learned

• Total removal action costs were approximately $4,047,000, including approximately $1,292,000 in costs incurred by the land treatment contractor.
• The discovery during construction of the LTU and resulting excavation and treatment of an additional 5,000 tons of contaminated soil added approximately $65,000 to the contractor costs and delayed the construction of the LTU by one month.
• The OSC indicated that contract expenditures were minimized during this remediation because the ERCS contractor project manager was not required to be present on site during routine bioremediation activities.
• The OSC identified calculating volume, rather than mass, as a preferred method to quantify the amount of soil to be treated in the LTU. Weighing truckloads of soil was more costly than surveying soil stockpiles or using overflights to determine volume.
• The treatment at Scott Lumber was completed using 2 lifts; the system was constructed using a clay liner and underdrain system.

Performance Observations and Lessons Learned

• The cleanup goal for total PAHs at Scott Lumber was established in terms of the sum of the concentrations for 16 specific polynuclear aromatic hydrocarbons. Cleanup goals for this application were specified as 500 mg/kg for total PAHs and 14 mg/kg for benzo(a)pyrene, one of the 16 specified PAHs.
• The cleanup goals were achieved within 6 months for Lift #1 and 3 months for Lift #2.
• Land treatment at the Scott Lumber site reduced total PAH concentrations from 560 to 130 mg/kg, and BAP from 16 to 8 mg/kg, in Lift #1. In Lift #2, concentrations were reduced from 700 to 155 mg/kg for total PAH and from 23 to 10 mg/kg for BAP.
• The most rapid decreases in PAH concentrations in Lift 1 occurred within the first 6 weeks of treatment.

Other Observations and Lessons Learned

• This was one of the early applications of land treatment of creosote-contaminated soil at a Superfund site.
• A laboratory/demo-scale treatability study conducted using site soils demonstrated the feasibility of bioremediation for treatment of creosote-contaminated soils at Scott Lumber.
• Additional information provided by the OSC and Contracting Officer concerning the procurement and contracting processes at the Scott Lumber site (and other removal action sites) is provided in Reference 10. Reference 10 is available from the U.S. EPA National Center for Environmental Publications and Information (NCEPI), P.O. Box 42419, Cincinnati, OH 45242; (fax orders only - (513) 489-8695).

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References

1. Federal On-Scene Coordinator's Report, Scott Lumber Company Site, non-NPL, Alton, MO, July 10, 1987 - October 1, 1991. Bruce A. Morrison, U.S. Environmental Protection Agency, January 15, 1993.
2. On-Site Bioreclamation of Creosote-Contaminated Soil at the Scott Lumber Site. Bruce A. Morrison, U.S. Environmental Protection Agency. Paper 92-27.04, from the Air and Waste Management Association Conference, 85th Annual Meeting and Exposition, June 1992.
3. Memorandum Request for Exemption from the $2 Million Limitation at the Scott Lumber Company Site, Alton, MO. Morris Kay to J. Winston Porter, U.S. Environmental Protection Agency, 15 July 1988.
4. Final Report, Feasibility of Biological Remedial Action at Scott Lumber Company Site, Alton, MO. Ecology and Environment, Inc., March 1988.
5. Personal communication, Bruce A. Morrison, U.S. Environmental Protection Agency, 11 April 1994.
6. Analytical data reports: 4/19/90, 5/31/90, 6/14/90, 6/28/90, 7/12/90, 7/26/90, 8/9/90, 8/23/90, 9/6/90, 9/20/90, 10/5/90, 10/18/90; provided by Bruce A. Morrison.
7. Standard Operating Procedure; Extraction and Analysis of Water and Soils for Semivolitale Organic Compounds, September 21, 1989.
8. Memorandum; Response to Information Request for Scott Lumber Site, Bruce Morrison to Linda Fiedler, U.S. EPA, January 5, 1995.
9. Letter from Christina Cosentini to Linda Fiedler, Scott Lumber information request, February 3, 1995.
10. Procuring Innovative Treatment Technologies at Removal Sites: Regional Experiences and Process Improvements, U.S. EPA, Publication 542/R-92/003, August 1992.

Analysis Preparation

This case study was prepared for the U.S. Environmental Protection Agency's Office of Solid Waste and Emergency Response, Technology Innovation Office. Assistance was provided by Radian Corporation under EPA Contract No. 68-W3-0001.

Back to Observations and Lessons Learned | Table of Contents | Forward to Appendix A - Treatability Study Results

Appendix A - Treatability Study Results

Identifying Information

Site Identifying Information
Site Name: Scott Lumber Company
Site Location: Alton, Missouri
CERCLIS #: MOD068531003
Action Memorandum Date: 7/10/87

Type of Treatability Study
Laboratory/Demo-Scale of Soil Bioremediation

Treatability Study Strategy

The purpose of this treatability study was to assess the feasibility of bioremediation for creosote-contaminated soil by: (a) growing a microbial culture capable of degrading PAHs; (b) demonstrating that the site soil was not toxic to the microbes; and (c) evaluating the relative biodegradability of PAH constituents.

Three test runs were completed during this study. The overall philosophy of conducting the three runs was to measure system performance under differing conditions of soil and creosote loadings and reloadings. As shown in Table 1, Run No. 1 received an initial creosote loading of 1% and no additional loadings. The purpose of this run was to observe the biodegradation of PAH constituents with no soil present. In addition, after microbes were killed (Week 4), Run No. 1 was used as a control run to assess the potential for PAH removal by processes other than biodegradation. Run No. 2 received an initial creosote loading of 0.5% and then was reloaded with 0.5% creosote at 2 and 4 weeks. The purpose of this run was to investigate the potential enhancement of biodegradation of higher-molecular-weight PAHs by the addition of more easily degraded, lower-molecular-weight PAHs. Run No. 3 received the same creosote loadings as Run No. 2 but was also loaded and reloaded (at times of creosote loading) with 10% clean soil. The purpose of this run was to investigate the potential inhibition of biodegradation due to possible soil toxicity. [4]

Table A-1. Schedule for Loadings and Reloadings Used in Treatability Study [4]

Creosote for Soil Loading (%)*

*All volumes are in weight/volume percentages

Treatment System Description

Bioremediation System
Description and Operation
The bioremediation system consisted of three aqueous bioreactors and related equipment. The bioreactors used were 10-20 liter plexiglass vessels, which were aerated and mixed using humidified air. The three bioreactors were placed in a walk-in environmental chamber which was kept at a constant temperature of 30 C. [4]
Microbial cultures used in this study were grown using sludge from the site and a nearby publicly owned treatment works (POTW). System operation involved loading the bioreactors with an aqueous slurry of clean soil from the site, creosote, inorganic nutrients, and microbial cultures. The three bioreactors were loaded and reloaded with varying quantities of soil and creosote. Bioreactors were maintained at a pH of 7.0 using sulfuric acid, and operated for approximately 6 weeks. [4]

Procurement Process
Ecology Environment, Inc. was tasked by EPA Region VII through a Technical Assistance Team (TAT) Zone II contract to perform the treatability study as a Technical Assistance Project (TDD No. TPM-8801-001).

Treatment Performance Results

Treatment Performance Data
Treatment performance data were collected for oxygen uptake rate, PAH constituent content, solids content, and organic carbon content. Oxygen uptake was measured to indicate microbial activity levels. Microbial respiration was the only mechanism for consuming dissolved oxygen in the bioreactors. A gas chromatograph coupled with flame-ionization detector (EPA Method 610) was used to measure the concentrations of PAH constituents. Solids content was analyzed by measuring the concentrations of dissolved solids (DS) and volatile suspended solids (VSS). DS measurements indicated the amount of inorganic nutrients and creosote present in the bioreactors, and VSS measurements were used as a rough estimate of the microbial community size. Results from organic carbon analyses yielded values for both soluble organic carbon (SOC) and total organic carbon (TOC). These measurements indicated the amounts of dissolved and total creosote, respectively, in each bioreactor. Samples for each of these parameters were collected from the bioreactors by dipping a beaker into the solution and collecting liquid free of froth and organic sheen.
Data on the oxygen uptake rate for the 3 runs, as a function of time, are presented in Table 2. Data on the concentrations for both individual and total PAH constituents for the 3 runs, as a function of time, are presented in Table 3. The DS, VSS, SOC, and TOC concentrations for the 3 runs, as a function of time, are presented in Figures 1-4, respectively [note - Bioreactor 1 shown on the figures corresponds with Run No. 1, Bioreactor 2 with Run No. 2, and Bioreactor 3 with Run No. 3]. [4]

Performance Data Assessment
The oxygen uptake data indicate that a microbial culture capable of degrading PAHs was grown during this study. Oxygen was actively consumed in each of the bioreactors, and rates of oxygen consumption increased significantly after reloadings in response to substrate addition. Run Nos. 2 and 3, which were reloaded during the run, experienced the greatest increases in oxygen consumption rates. Since creosote was the only organic substrate present and no physical or chemical mechanism was identified for oxygen consumption, the uptake of oxygen in the bioreactors was attributed to biodegradation of PAHs. VSS results show that the size of the microbial community (biomass) increased over the course of the study in proportion to creosote reloading, indicating that a microbial community capable of degrading PAHs had been established.
In addition, the oxygen uptake data, which showed comparable results for Run No. 3 (which included loading and reloadings with 10% soil) as for Run Nos. 1 and 2, indicate that site soils were not toxic to the microbial community.
However, with respect to the biodegradation of PAHs, the results of the treatability study did not establish the relative biodegradability of PAH constituents. PAH analytical data from the 3 runs are not consistent with data for the creosote loadings and reloadings.

Table A-2. Oxygen Uptake Rate (mg/L/min) [4]

For example, Run No. 1 (the 1% creosote loaded on Day 0, containing 90% PAHs) corresponds with an expected PAH concentration of 9,000 mg/L, while only 855 mg/L of PAHs were measured. However, the data indicate that PAHs are biodegraded using the microbial cultures in this study, and that bioremediation appears to be feasible for creosote-containing soils at Scott Lumber.

Performance Data Quality
The PAH analyses included matrix spike test quality control efforts. [4]

Table A-3 PAH Data [4]

Observations and Lessons Learned

Performance Observations and Lessons Learned

• A microbial culture capable of degrading PAHs was grown during this study, as shown by data for oxygen uptake rate and VSS.
• Soils from the Scott Lumber site were shown to be not toxic to the microbial community.
• While the treatability study did not establish the relative biodegradability of PAH constituents, the study showed that PAHs are biodegraded using the microbial cultures in this study and that bioremediation appears feasible for creosote-containing soils at Scott Lumber.
• The treatment vendor indicated that results for DS, SOC, and TOC analyses were inconclusive with respect to microbial activity in the 3 runs.

Other Observations and Lessons Learned

• This technology was selected as the full-scale remedy and successfully implemented at the Scott Lumber Company site. The full-scale treatment application met the established cleanup levels.
  

Figure A-1. Dissolved Solids Data []

Figure A-2. Volatile Suspended Solids Data []

Figure A-3. Soluble Organic Carbon Data []

Figure A-4. Total Organic Carbon Data []

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