SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM SEDIMENTS REMEDIATION ACTION TEAM MEETING

DoubleTree Hotel
Wilmington, Delaware
September 12-13, 2000

WELCOME AND OPENING REMARKS
Richard Jensen, DuPont Corporate Remediation

Richard Jensen, co-chair of the Remediation Technologies Development Forum (RTDF) Sediments Remediation Action Team, opened the meeting by welcoming participants. (Attachment A lists the meeting attendees. Attachment B presents Jensen's introductory materials.) Jensen provided an overview of goals and agenda items for this meeting. He said that a new meeting format would be tried: the meeting would focus on a single topic--in situ treatment--and would include several presentations, a brainstorming session, and discussion period that was aimed to identify one or two collaborative pilot demonstration projects. Jensen said that in situ treatment was chosen as the meeting's topic because an informal poll revealed that Action Team members were most interested in this topic. (The next workshop may deal with assessment of natural attenuation or with reactive confined disposal facilities [CDFs], both of which also scored high on the poll.)

STATUS REPORT ON THE NATIONAL ACADEMY OF SCIENCES (NAS) STUDY
Kelly Madalinski, U.S. Environmental Protection Agency (EPA) Technology Innovation Office

Kelly Madalinski noted that NAS is in the process of preparing a report. The report, mandated by Congress, will be delivered on November 30, 2000, to the legislative body and EPA. In March 2001 it will be published and distributed. For more information, RTDF members can contact Dennis Timberlake or visit http://www.nas.edu. Madalinski said that EPA is looking forward to seeing the report's recommendations.

INTERSTATE TECHNOLOGY AND REGULATORY COOPERATION
Richard Jensen, DuPont Corporate Remediation

Jensen talked about an organization called the Interstate Technology and Regulatory Cooperation (ITRC). (His presentation materials are included as Attachment C.) Made up of state regulators, the organization is a state-led national coalition dedicated to achieving better environmental protection through innovative technologies. ITRC members collaborate to create and distribute guidance on innovative technology. The organization was founded in 1995 in conjunction with an initiative started by the Western Governor's Association; it is now made up of more than 30 states and the District of Columbia, multiple federal partners, industry participants, and other stakeholders. ITRC's mission is to provide a reliable network among members of the environmental community and, through this network, focus on innovative technologies, help regulators build their knowledge base, help regulators save time and money when reviewing environmental technologies, guide technology developers in collecting performance data to satisfy the requirements of multiple states, and save technology vendors the time and expense of conducting costly duplicate demonstrations. ITRC produces technical and regulatory guidelines, technical overviews, case studies, decision trees, and reference guides, as well as training courses. The organization has worked with the RTDF in the past to produce effective training courses on natural attenuation in groundwater, as well as permeable reactive barriers.

Jensen said that ITRC has been hesitant about working on sediments related issues. Recently, however, ITRC has become convinced that the issue of sediments is important to many states. Thus, ITRC is working to create a work group to address sediments issues. The role of the new sediments team will be decided at ITRC's national meeting in October 2000 (in San Antonio). The work group is expected to initiate activities in 2001. Rich DeWan of the New Jersey Department of Environmental Protection will probably lead the new team. Jensen said there will be opportunities for the RTDF and ITRC to work together on assessment white papers and training programs.

NATIONAL RESEARCH COUNCIL(NRC)/NAS PANEL ON THE REMEDIATION OF NAVAL FACILITIES
Ralph Stahl, DuPont Corporate Remediation

Ralph Stahl said that a new NRC/NAS panel was formed in April to evaluate remediation efforts at Naval facilities. Stahl said that he serves on the panel as the sole "ecotox" expert. Danny Reible, another RTDF Action Team member, also serves on the panel. The panel was given four or five tasks. Mainly, they are to study how (in the context of either the Comprehensive Environmental Response, Compensation, and Liability Act or other regulatory constructs) the Navy can alter remedies based on new information or changes in policy--changes that affect the current regulatory approach, which the Navy considers very rigid. One of the main panel issues will be sediments. The panel is also working on a performance matrix that explains how to determine whether remediation goals have been achieved. The Navy is considering remedial goals from the "changing the ROD" and ecological perspectives. (Until recently, the Navy has not made it a priority to consider whether remediation has improved a site's ecological environment.) The panel's goal is to submit a report to the Navy by the end of 2001. Stahl added that much of what is in the Action Team Assessment Subgroup's white papers will feed into the Navy's report. For more information, RTDF members should contact Dennis Timberlake or go to the NAS Web site (http://www.nas.edu).

EPA GREAT LAKES NATIONAL PROGRAM OFFICE (GLNPO) GRANTS
Kelly Madalinski, EPA Technology Innovation Office

Madalinski talked about the Great Lakes region. He said that there are 42 areas of concern in this area, but that many of these areas are no longer a threat to human health or the environment. Madalinski said that GLNPO awards grants for field demonstrations in the Great Lakes region. (GLNPO is separate from EPA's national headquarters and EPA Region 5.) In 1998, 1999, and 2000, $1.35 million in grant money was spent on sediment issues for assessment, characterization, and remediation in the Great Lakes. Madalinski said that grants are given through a matching system: GLNPO provides a grant and a local, state, or federal agency provides some type of matching funds. This year awards range from $30,000 to $250,000. In the past, EPA has awarded grants of over $500,000 depending on what the project is, who the stakeholders are, and what they contribute. The only limitations are that projects must take place within, or be directly applicable to, the Great Lakes watershed. Also, the sponsor agency that applies for a grant must be a nonprofit organization. (The sponsor could be a state, local, or federal agency such as the Navy or the Army Corps of Engineers.)

Madalinski described the process that is involved with applying for a grant. First, he said, a pre-proposal should be submitted. Pre-proposals for upcoming projects, Madalinski said, are due by December 2000. Pre-proposals should be 3 to 5 pages long and should include a general concept, objectives, a budget, and a description of the partners involved. GLNPO screens pre-proposals and then requests full proposals (10 to 20 pages) from qualifying applicants. Grants are awarded in August or September. The office typically offers 10 grants each year.

Madalinski described projects that GLNPO is considering. For example, he said, GLNPO has expressed some interest in demonstrating a reactive cap. Another idea would be to perform demonstration projects on assessment technologies. Madalinski said that one possible GLNPO field demonstration may involve a CDF project that has already been funded through an assistance agreement with the Army Corps. This project focuses on three pilot-scale demonstrations: phytoremediation, bioremediation, and a technology that has yet to be determined. The site, which is in Milwaukee, Wisconsin, is contaminated with polycyclic aromatic hydrocarbons (PAHs) at levels as high as 500 parts per million (ppm). Madalinski suggested that RTDF could act as a technical liaison at this site, providing input and oversight.

Madalinski said that the RTDF Action Team might want to consider applying for a GLNPO grant. Obtaining such a grant would allow the RTDF to move into the field, which it has been struggling to do for the last few years. Anyone interested in more information should visit www.epa.gov/glnpo or send an e-mail to Madalinski or GLNPO.

OVERVIEW OF IN SITU TREATMENT TECHNIQUES FOR CONTAMINATED SEDIMENTS
Kelly Madalinski, EPA Technology Innovation Office

Madalinski said that EPA had a student from Oregon State University produce a report on in situ treatment technologies for sediments. EPA is interested in in situ treatment because it is less expensive than present treatment techniques and it reduces handling and exposure. Another advantage of in situ treatment is that it results in less suspension and volatilization than other options.

Madalinski said that types of in situ treatment include:

• Biological
  • Microbial degradation
  • Addition of oxygen, nutrients, microorganisms
• Chemical
  • Destruction (e.g., oxidation or dechlorination)
  • Addition of permanganate, hydrogen peroxide, potassium hydroxide
• Immobilization
  • Encapsulation and/or reduction of solubility, mobility, or toxicity
  • Addition of cement, fly ash, limestone

When EPA began its study of in situ treatment, Madalinski said, it looked at literature like the 1994 Assessment and Remediation of Contaminated Sediments Program (ARCS) report and a 1997 National Research Council (NRC) report. These reports presented a fairly discouraging outlook. The ARCS report indicated that in situ treatment is suitable only for small-scale application; the report also noted that only limited guidance materials are available on feasibility, design, and implementation. The 1997 NRC report, which cited two demonstration projects, concluded that the state of design was nonexistent and that in situ treatment had few proponents.

Madalinski said that the EPA Technology Innovation Office wanted to improve knowledge of specific aspects of in situ treatment. Toward this end, EPA composed a comprehensive white paper about the state of the practice, one that included theory and design, current use and deployment, existing performance data, advantages/limitations, research gaps, and areas of potential promise. The paper documented a study that was funded by the National Network for Environmental Management Studies and conducted by Oregon State University's Jon Renholds. In the study, Renholds gathered information from project documents, reports, and communication with field practitioners. Renholds finished his report in September 1998. It can be found at www.cluin.org under "Publications and Software."

Madalinski said that Renholds study, which was completed in three months, did not include bench-scale projects. (Its focus was on pilot- and full-scale projects.) It also did not emphasize current research activities. Its geographical focus was on the United States and Canada. The study assessed the following projects:

Madalinski gave details on three of the projects assessed in the study:

• At the Hudson River site, General Electric studied the aerobic biodegradation of some chlorinated biphenyls. Test cells consisted of six caissons that were 6 feet wide and 8 feet deep. The amendments varied (including nutrients such as phosphate and oxygen) and the mixing was periodically changed. There was biodegradation associated with intermediate chlorobenzoates. Questions remain about the feasibility of implementing the process.

• At the Fox River site, the source of contamination was a bridge (later removed) that was painted with lead paint. The contamination was treated in situ and the site passed a toxicity characteristic leaching procedure (TCLP) test. Coffer dams were used to maintain an inward hydraulic gradient. Phosphate, magnesium oxide, and limestone were used in the treatment. Five hundred tons of sediment were treated and removed. It was estimated that the actual treatment cost between $30,000 and $40,000.

• The Manitowoc River project was by most accounts unsuccessful. As part of this project, cylinders were driven into the sediments and a slurry of cement and fly ash was injected and mixed within the cylinders. Resuspension became a problem when it was found that the sediments were 3 to 4 feet above river bottom; the result was a semi-solidified structure.

Madalinski said that in situ treatment is still innovative and has not had many applications. In most of the studies Renholds looked at, none of the projects met the target goal, performance criteria, or treatment goal. In situ treatment has limitations--it lacks process control, implementability, saturated anaerobics at ambient temperatures, and bioavailability.

Madalinski said that further research on delivery mechanisms is necessary. Micro-encapsulation, which involves using a polyvinyl alcohol matrix, is one delivery mechanism of interest. The Monsanto Corporation has also developed a "biological carpet." EPA's Superfund Innovative Technology Evaluation program emphasizes sediment management alternatives. The EPA laboratory in Cincinnati is publishing a journal article on the release of hydrogen from in situ treatment. The laboratory is also studying zero-valent iron.

IN SITU SEDIMENT TREATMENT TECHNOLOGY (LIMNOFIX)
Brian Senefelder, Golder Associates, Inc.

Introduction

Brian Senefelder's presentation materials are available as Attachment D. Senefelder opened his presentation by saying that the Limnofix in situ sediment treatment technology was developed and patented by Environment Canada through the National Water Research Institute in Burlington, Ontario. Golder Associates has worked with Environment Canada since the early 1990s. In 1995, Golder Associates received a license to assist Environment Canada with the commercialization and full-scale application of the technology.

Senefelder said that the Limnofix treatment technology remediates contaminated sediments by injecting oxidants, nutrients, or flocculents into contaminated zones. These materials alter the physical, chemical, and biological properties of contaminated sediments. To date, Senefelder said, Golder Associates has not injected engineered bacteria. Rather, indigenous bacteria have been used.

Senefelder said that the Limnofix technology can be used to oxidize sulfides, reduce sediment toxicity, control eutrophication, alter the redox of the sediment, and enhance natural biodegradation of organic contaminants. Most of the work done to date has been performed on sediments contaminated with benzene, toluene, ethylbenzene, and xylenes (BTEX); sulfides; TPH; and PAHs.

Senefelder said that the technology has been used--in pilot-scale and full-scale applications--in both fresh and marine environments. The process is applicable at sites such as petroleum-processing plants, steel mills, pulp and paper mills, and manufactured gas plants where there are coal-tar contaminants. The technology attempts to enhance bacterial breakdown of organics, as well as remove sulfides. So far, the technology has been shown to work best on organic compounds.

Senefelder stressed the importance of performing adequate site characterization. In several projects, it has been necessary to go back and perform more extensive site characterization studies. Pilot-scale testing has generally taken place in small areas or test plots 50 to 100 meters long. For both pilot-scale and full-scale sites, it is important to have a monitoring plan.

Deployment and Monitoring Activities

Senefelder explained how Limnofix is deployed. Treatment chemicals are stored on a ship in 500-gallon tanks. Then, once the ship is positioned above contaminated sediments, the chemicals are pumped through an injection boom (below the water surface) directly into the sediments. Senefelder said that this equipment configuration has been used to deploy materials in areas that have water depth ranging from 2 to 22 meters. The injection tines penetrate half a meter. At sites in Canada, work crews have shown that they can treat about 1 hectare (2 acres) per day.

Usually, after treatment materials are deployed, small-scale reactors are set up and gas production is monitored as an indicator of remediation. (Gas generation volume is plotted over time.) Senefelder said that long-term treatment and monitoring activities included: (1) analyzing samples from control areas, (2) analyzing the toxicity of samples, (3) adding calcium nitrate as an oxidant, (4) adding organic amendments, (5) running the Microtox® test, and (6) monitoring acid volatile sulfides.

Field Sites in Ontario

Limnofix was applied to the Hamilton Harbor and St. Mary's River sites, two Great Lakes areas of concern in Sault St. Marie, Ontario. At Hamilton Harbor, the primary contaminants were sulfide, TPH, and PAHs. At the St. Mary's River site, a steel mill and a paper mill disposed of wood wastes and sulfide (free sulfide and acid volatile sulfide), leaving these chemicals in the river sediments. In Hamilton Harbor, calcium nitrate was used as an oxidant; in the St. Mary's River, ferric chloride solution was the treatment used. (Most applications have moved away from the use of ferric chloride, because it is corrosive and dangerous to handle.)

During the field demonstration, Environment Canada monitored worker exposures to volatile organic compounds and sulfides. Health and safety standards for respiratory protection were not exceeded.

Not much has happened since the pilot tests were conducted. In Hamilton Harbor, an industrial accident took place: a crane in a boat slip fell into the treatment area, causing resuspension of contaminated sediments from other areas.

Field Sites in Hong Kong

In 1999, Senefelder said, Golder Associates began work on a site at the old Hong Kong airport. While land there was being reclaimed, a problem arose in a discharge canal named Kai Tak Nullah. The canal had historically received municipal and industrial wastewater, leaving very large concentrations of sulfides in the sediment and promoting methane generation due to anaerobic conditions. The amount of air traffic in the area made it necessary to mix and inject calcium nitrate at night from a barge. Concentrations of hydrogen sulfide were reduced by more than 90% in 30 days.

Field Sites in Bangkok

Senefelder said that Golder Associates has also worked in Bangkok: there, they have been involved with the treatment of khlongs (canals) into which untreated municipal and industrial wastewater has been discharged. In these cases, there are issues of sediment toxicity, odor, and corrosion from the hydrogen sulfide generated by the contaminants.

Field Sites in Massachusetts

On a full-scale basis in the United States, Golder Associates has teamed with ReTec and Massachusetts Electric on an intertidal cove site contaminated with coal tar, PAHs, and free product. The site is in Collins Cove, in the northern part of Salem, Massachusetts. The cove, which is in a residential area, has intertidal sediments and a 9-foot tidal change. At the site, a former manufactured gas plant (managed by Massachusetts Electric and Boston Gas) has contaminated the sediments with coal tar. The sediment depth is shallow, but there are isolated pockets of coal tar at depths greater than 12 inches. In 1998, Golder Associates was awarded some work on a full-scale application based on a feasibility study. The area of treatment encompasses 60,000 square feet, or an acre and a half. Massachusetts Electric has installed an onshore ground-water interceptor trench to collect contaminated ground water with very low pH, as well as free-phase coal tar. The PAHs at this site are mostly lower-molecular-weight PAHs, primarily naphthalene and 1- and 2-methyl-naphthalene.

Because of the intertidal situation, Senefelder said, a simplistic approach was taken. The remediation effort used three 1,500-gallon tanks of calcium nitrate solution, stored onshore. From the storage tanks the solution was pumped into a 300-gallon tank on a tractor with a chisel plow. The solution was pumped through injection tines, which are spring-loaded so that they pop up when they hit bricks and boulders. The operating situation was unusual, because the project had high public visibility. Massachusetts Electric communicated with the public about the project; meanwhile, the project went through a year and a half of permitting through the Salem Conservation Commission, the State of Massachusetts, and the Army Corps of Engineers.

Senefelder said that the calcium nitrate was applied three times each year. (Application took place in the warmer months, when there is more biological activity.) Each application took three days: each day, 1,500 gallons of calcium nitrate were injected. During this period, wash-out of the oxidant became an issue. The area was smoothed over after every application to keep the oxidant in the sediment. In areas that were inaccessible by tractor, the oxidant was injected manually.

After two years of treatment and six applications, Senefelder said, there has been a fairly significant PAH reduction. Studies of benthic organisms suggest that remediation is moving in the right direction. Nitrate is not being washed out at the rate predicted. This year more chemistry and biological tests will be done to assess the situation.

Golder Associates has now observed less free-phase coal tar at the site. After the first treatment application, there was gas generation in the sediments; this shows that bioremediation is occurring. Positive redox values have resulted from the addition of nitrate. There is a reduction of volatile organics.

ELECTROCHEMICAL REMEDIATION OF SEDIMENTS
Joe Iovenitti, Weiss Associates

Joe Iovenitti introduced his topic as "electrochemical remediation of sediments," noting that electrochemical geo-oxidation is one type of technology that falls under this category. (His presentation materials are included as Attachment E.) Iovenitti began by describing his company's background in the area. Weiss Associates has been in business for 20 years, he said, and is headquartered in California. It is an environmental consulting firm with a technology division. Through that division, the company has worked with other firms on remediation technologies. For example, he said, Weiss Associates has a German partner named P2 Soil Remediation, Inc., a company that has also been in business for about 20 years and has remediated about 2 million metric tons of soil in Europe. Iovenitti said that P2 Soil Remediation, Inc. also has a joint venture in using direct-current electricity in subsurface activity with a U.S. firm called ElectroPetroleum, Inc.

Iovenitti said that soil and ground water, along with sediments and pore water, behave as electrochemical cells when two electrodes are placed in the ground and a direct current is passed through them. Electrochemical remediation technologies can mineralize contaminants and enhance the mobilization of metals. Such technologies work very fast--in one case, electrochemical remediation removed 168 pounds of mercury in approximately 26 days. PAHs have been remediated in approximately 70 to 100 days. Iovenitti said that electrochemical remediation can be conducted in situ or ex situ. In its simplest form, it involves pulling power from a local utility line; the power is passed through DC/AC converters, then run through electrodes. This generates redox reactions in the subsurface, remediating the site.

Iovenitti described the five major electrokinetic mechanisms that are involved with electrochemical remediation: electro-osmosis, electrophoresis, electromigration, electroresistivity, and electrolysis. Electro-osmosis occurs when an electric field causes movement of water through fine-grained soils. Electrophoresis is the movement of colloids and bacteria through a solution in an electric field. Electromigration is the movement of ions (again, in an electric field). If the power applied to a system is increased, electroresistivity heating results. When power is increased, there is a breakdown of water at the electrodes that results in electrolysis. Iovenitti said that electrochemical remediation has geotechnical applications other than remediation, such as dewatering earthen dams or clay layered soils.

Iovenitti spoke of two processes in detail: electrochemical geo-oxidation, which involves the destruction of organics, and induced complexation, which involves the enhanced mobilization of metals. Both of these are electrochemical remediation technologies that work in soil. When they are applied to ground water or pore water, other, related electrochemical technologies are used, but Iovenitti did not discuss these.

Iovenitti said that electrochemical remediation technologies are proven in Europe. They are seen as the next generation in electrokinetic treatment, because they directly induce redox reactions in the subsurface. This allows organics to be destroyed and enhances the mobilization of metals (and radionuclides that behave as metals) through the induced compensation mechanism. In induced compensation, electro-osmosis, electromigration, and electrophoresis take place. These happen at the formation scale. At the pore scale, it is believed, electrolysis takes place.

If one were to look at electrical energy input, Iovenitti said, one would see electrochemical geo-oxidation at the low end of the power spectrum and in situ vitrification at the high end. In between, the electrokinetic processes of electro-osmosis, electromigration, and electrophoresis operate. Increasing power produces electrolysis; further increases cause in situ vitrification. Induced compensation seems to operate in the region between the destruction of organics, electrochemical geo-oxidation, and the beginning of electrokinetics. When induced compensation is applied to metals, there is an under-optimization for the creation of redox reactions and mass transport, but both take place.

Iovenitti said that induced redox reactions occur when electrodes are placed in sediment and a low-voltage, low-amperage coupled DC/AC field is sent to the electrodes. This generates an induced polarization (IP) field. IP is a 50-year-old process used extensively by the mining industry to explore for sulfide masses. Miners use IP by putting a high-energy pulse into the subsurface, then looking for decay. In electrochemical remediation, a low-energy pulse--that is, one with very low voltage and amperage--is put into the system, and the IP field is kept active. This makes the soil behave as a capacitor. When soil behaves as a capacitor, it discharges electricity. This creates an aggressive environment in the pore space, where redox reactions then take place. This can happen ex situ or in situ. These reactions take longer in coarse-grained material than in fine-grained material. Fine-grained material, however, has more reaction sites, so reaction rates for the destruction of organics or the enhanced mobilization of metals are inversely proportional to grain size. Reactions are much faster in clay and slower in gravel. As mentioned, the reactions occur at the pore scale and at all interfaces in the soil-water-contaminant system. The process involves no pumping or adding of chemicals--just running electricity through the electrodes.

When power is run through the DC/AC converters to the electrodes, voltage and amperage follow each other. When one spikes independently, it means that the soils are discharging electricity. (High voltage, out of phase with amperage, indicates that electricity or voltage is coming from somewhere else. The only place it could be coming from is the soil.)

At the pore scale, Iovenitti said, every soil particle acts as an electrode in which oxidation occurs at one end and redox occurs at the other. In electrokinetics, there has to be an increase in power to increase the mass transport and cause electrolysis. When this takes place, water is broken down; acid is created at one electrode and a base is created at the other. Chemicals have to be added to counter this. When electrochemical geo-oxidation is operating, on the other hand, a near-neutral condition exists.

Iovenitti said that electrochemical geo-oxidation is depth-independent. As long as a bore hole can be drilled, an electrode can be placed in the subsurface. Iovenitti presented several case studies from Europe in which the technology proved effective.

Iovenitti said that electrochemical geo-oxidation is ISO 9001-certified, meaning that the ECC has approved its quality assurance/quality control process. Electrochemical geo-oxidation destroys organics in situ, without any transport needed. The process significantly enhances the mobilization of metals. Remediation times are generally on the order of months. Preliminary cost estimates range from $120 per yard for 3,000 cubic yards to $30 per yard for 100,000 cubic yards. The technology can be applied ex situ as well as in situ, but the latter is favored, because at least 500,000 tons of sediment are needed for ex situ applications. Although soil resistivity is an intensive parameter that does not change depending on volume, the soil resistance is an extensive parameter. When operating in situ, the process has an "infinite" amount of earth working in its favor. This means that redox reactions can be induced with low power, something that cannot be done with a small sample. Iovenitti said that electrochemical geo-oxidation has been proven in Europe on a commercial basis; his company would like to collect the additional data that are needed to have it qualified.

In closing, Iovenitti expressed interest in establishing a public-private partnership to demonstrate, evaluate, and deploy electrochemical remediation. He asked the RTDF Action Team to consider such a partnership.

MEMBRANE DELIVERY TECHNOLOGY
Henry Tabak, EPA National Risk Management Research Laboratory (NRMRL)

Henry Tabak talked about the multi-faceted research that is being performed at NRMRL. This research involves developing a protocol for the study of bioavailability through research on absorption and desorption. NRMRL is also evaluating aerobic and anaerobic biodegradation of PAHs in surface and subsurface sediments. Tabak added that the Environmental Engineering Department at the University of Cincinnati is studying membrane- and gel bead-assisted in situ bioremediation.

Tabak opened his presentation by noting that sediments are the ultimate sinks for a wide variety of contaminants. Sediment contamination is widespread: 10% of all sediments underlying surface waters pose a risk to fish, humans, and wildlife. Many metals and persistent organics that enter water resources accumulate to high levels in sediments. Some contaminants are released slowly, because they are covalently bonded to soil sediment particles. Different solvents have to be used to desorb contaminants from entrapment; doing this requires much strategy.

In some cases, sediments can be remediated via natural attenuation, a process where chemicals are degraded by indigenous bacteria or made biologically unavailable. Remediation can also occur through in situ capping, in situ confinement, and in situ treatment. The latter involves using biostimulation (introducing nutrients, co-metabolites, or bio-inducers) to enhance bioremediation. Another technique that exists is bioaugmentation, which utilizes cultures that have been specialized to treat particular organic substrates. Solidification and stabilization methods, Tabak said, can be used to encapsulate or reduce contaminants' mobility and toxicity.

Tabak said that there are some problems associated with in situ biological treatment. For example, mass transfer limitations, a lack of mixing, minimal lateral movement of pore water, and slow desorption can cause problems. Insufficient oxygen permeation (which creates anaerobic conditions) is another issue of concern. Also, low temperature and slow diffusion of active organisms and contaminants are both unfavorable environmental conditions. (Tabak mentioned slow diffusion of active organisms because the mixture of organisms is critical to in situ biological treatment--indigenous organic matter often competes with introduced organisms.)

Tabak highlighted in situ bioremediation work that was performed in Hamilton Harbor, Ontario, a site that is contaminated mainly with metals, sulfides, oils, and organics. Investigators working at this site learned that bioremediation could be stimulated through chemical injection of oxidants and nutrients. They also found that 70% of oil and 68% of PAHs were biodegraded in 197 days.

On the Hudson River, Tabak said, researchers investigated PCBs and found that these chemicals can be anaerobically dechlorinated to mono and dia compounds, which can then be biodegraded to chlorobenzoates. Investigators also found that adding peroxide caused oxygen, nitrogen, and phosphate to form. Accelerated PCB degradation proved that rates with and without bio-augmentation were the same.

Tabak also said that the EPA laboratories in Gulf Breeze, Florida, have conducted new research on the micro-encapsulation of mircroorganisms. In the soil slurry systems studied in this research, capsules were dissolved in 30 minutes and contaminants were completely biodegraded in 30 hours.

Another remedial technique that Tabak described was a "biological carpet" studied at the Monsanto laboratories. Monsanto's researchers inoculated nylon carpet with microorganisms, nutrients, and activated carbon. The nylon carpet was later connected to a geotextile, then laid on contaminated sediment with the nylon on the bottom. The nutrients in the nylon attracted contaminants into the carpet, where biodegradation occurred. No large-scale tests of this technology have been conducted, due to a lack of funding.

Tabak emphasized that the availability of electron acceptors and nutrients must be considered when natural processes are used as a remedial strategy and indigenous microorganisms are involved. He said that methanogenic organisms are present in both aerobic and anaerobic zones, but that they are much more common in the latter. A variety of reactions take place between the zones, such as denitrification, manganese reduction, iron reduction, and sulfate reduction.

Tabak said that the availability of dissolved oxygen decreases sharply with sediment depth. Sediments are re-entrained by flow and mixing, exposing shallow buried contaminants absorbed into the sediment particles. The sediments, due to their high levels of organic carbon, can serve as a reservoir for hydrophobic contaminants like PAHs.

Tabak said that EPA has been very successful in degrading PAHs in New York Harbor sediments. At this site, anaerobic conditions prevailed and sulfate reducers were very active. (It is still not known if sulfate reducers are directly involved in the transformation of PAHs, but it is thought that they enable other microorganisms to degrade PAHs.) EPA has demonstrated that PAHs can be degraded anaerobically, provided that certain conditions exist, certain acceptors are present, and there is the right mixture of microbial consortia, particularly in subsurface sediments.

Contaminant bioavailability, Tabak said, can be reduced through bioconcentration or biodegradation processes. Bioconcentration involves organisms consuming contaminants. In contrast, biodegradation involves desorption, sorption on cells, and sorption on dissolved organic colloids. These processes can occur in situ or ex situ. Tabak stressed that in situ approaches are significantly cheaper and less labor-intensive.

Tabak said that EPA is developing a systematic, multilateral protocol for in situ bioremediation. The protocol can be applied to sediments contaminated with persistent organic compounds. It can be used to quantify natural recovery rates, contaminant bioavailability, natural and enhanced ex situ biodegradation rates, and environmentally attainable and acceptable pollutant endpoints. The protocol's purpose is to achieve in situ bio-observation of contaminated sediments.

Before closing, Tabak described two experiments, both of which are being conducted to access the effects of biodegradation. In these experiments, modified respirometric bioreactors are being used to control redox potential, temperature, and pH. The experiments are being conducted in large microcosms containing intact sediment core samples. Researchers are testing the findings of bioreactor studies by applying desired redox conditions to the systems using hollow fiber membranes. Sediment samples are collected periodically to determine contaminant concentration. Conclusions from the experiments are as follows:

• Membranes can be used to deliver various agents for effective biotreatment of PAHs in sediments.
• Various redox conditions can be created by varying the oxygen concentration in the gas flowing through the membranes.
• Biofouling of membranes is minimized by surface modification (deposition of inert metals by electroless plating) and pressure pulsing.
• Membrane reactors were operated at various pH and redox potentials.
• Two-ring PAHs were mineralized (biotransformed) to greater extents at high pH (8.0) and high redox potentials.
• The extent of PAH bioconversion decreased with greater ring sizes, although four-ring PAHs were converted to a greater extent than three-ring PAHs.
• Aerobic biodegradation rates for naphthalene were highest, followed by denitrification and then sulfate-reducing conditions.
• Naphthalene was not biodegraded under anaerobic conditions.
• The proposed membrane system can be used to achieve in situ biorestoration of PAH-contaminated sediments.
• By delivering various agents or combinations of agents, one can accelerate biorestoration rates for PAH-contaminated sediments.

Tabak's presentation materials are included as Attachment F.

IN SITU STABILIZATION OF PAHS: LESSONS FROM NATURE
Upal Ghosh, Stanford University

Upal Ghosh opened his presentation by noting that he and his colleagues are trying to address the ubiquitous problem of sediment contamination and its complexities, including continual long-term effects on ecosystems. (His presentation materials are included as Attachment G.) Ghosh devoted his discussion to a project being performed on PAH-contaminated sediments from Milwaukee Harbor. Ghosh and his colleagues are trying to treat the harbor sediments in a CDF. He said that the Milwaukee Harbor project has four objectives: (1) determine how and where PAHs are bound to sediment, (2) determine what accounts for binding or sequestration of hydrophobic organic compounds in sediments, (3) evaluate how binding properties affect treatment efficiency, and (4) prepare the site for beneficial reuse.

Ghosh said that a unique technical approach--based on techniques that Stanford University developed to look for life on Mars--was implemented to study the harbor sediments. First, samples were analyzed at the subparticle scale by: (1) evaluating PAH location using infrared microspectroscopy, and (2) analyzing elemental composition through coal petrography. Then, particle separation and desorption studies were performed to determine the density and classify the size of the particles. Further analysis of PAH desorption was performed using a process known as Tenax®, along with thermal programmed desorption. In addition, biological assessments were performed on the sediment.

Ghosh said that the analyses revealed that the harbor sediments consist of silica and black particulate. Approximately 5% of the sediment was shown to be derived from coal. The smooth surfaces of the sediment's sand grains did not appear to have PAHs attached. The PAHs showed a tendency to attach only to coal particles.

Ghosh said that the release of PAHs from sediments was also studied. The results showed that 40% of the PAHs were released within a few days. Investigators learned that PAHs were released most readily from clay silt particles. Other sediment types released the PAHs more slowly. Bonds that formed between PAHs and coal particles proved to be very strong.

Ghosh said that investigators were able to evaluate the thermodynamics of PAH release through thermal programed desorption studies. They found that PAH release and diffusion rates are influenced by temperature. (Particles were sliced with a diamond knife. Investigators found that PAH diffusivity is extremely low at ambient temperatures.)

Ghosh then described the treatment approach that was used to remediate the harbor sediments. It involved using an aerobic bioslurry treatment process. Through this process, a portion of the contaminated material in the sediment was managed and treated. (Whole-soil chemistry tests and earthworm studies indicated that the treated materials were non toxic.) Some of the sediment, however, was not treated. Some consideration is being given to using the nontreated sediment as fill material if toxicity tests prove that earthworms can inhabit it.

In conclusion, Ghosh said that the studies performed on the Milwaukee Harbor sediments uncovered some interesting information that might help determine future remedial strategies at the site. That is, researchers found that coal from manmade sources acts as a strong sequestering particle. Thus, the best remedial strategy may be to sequester the PAH contaminant. PAHs have been proven to transfer from the harbor sediment to coke material. The research suggests that, for Milwaukee Harbor, it may be best to investigate how to deploy a cap and identify the biological effects of such a remedial strategy.

METABOLIC BIOMARKERS AS INDICATORS FOR ANAEROBIC IN SITU REMEDIATION OF BTEX AND PAHS
Craig Phelps, Rutgers University

Phelps outlined the three main goals of his work: identify potential bio-indicators for anaerobic BTEX and PAH degradation, demonstrate the specificity of these bio-indicators for active pollutant metabolism, and validate the bio-indicators' effectiveness in the field.

Phelps defined bio-indicators as chemicals that "demonstrate that active biodegradation is taking place at a site." Phelps said that good bio-indicators have four important properties: they are formed during active biodegradation of the target component, they are not normally found in the environment, they are water-soluble, and they are biodegradable." To identify bio-indicators, Phelps said, it is necessary to look at the basic pathways of degradation.

Phelps described the metabolic pathway for anaerobic toluene degradation. To verify that certain compounds in the pathway can be used as bio-indicators, Phelps constructed microcosm experiments with contaminated sediments. He measured the relative abundance of metabolic products observed in enrichment cultures that were fed mixtures of toluene and xylene.

Extraction of the microcosms led to the detection of four metabolites in enrichment cultures amended with toluene and xylene. 2-methyl benzylsuccinate (2-MBS) was chosen as the best biomarker, because it was produced in much greater concentrations than the other metabolites. 2-MBS was detected in denitrifying sediment microcosms during active toluene degradation, but not in microcosms that could not biodegrade toluene.

Phelps said that he has worked on sites in New York and New Jersey. The procedure he and his colleagues have developed has been tested with samples from the contaminated waters of Onondaga Lake and the cleaner waters of Blue Mountain Lake, New York.

Phelps said that he performed his most comprehensive tests on a manufactured gas plant site in New Jersey. The plant at this site had operated for 40 years before being shut down in 1951. All of the surface and subsurface structures had been removed during remediation of the soil. The site currently houses a natural gas regulating station. A contaminant pool extends northward from its source, through a residential neighborhood. Pollutants include BTEX, PAHs, styrene, phthalates, ethers, and chlorinated solvents.

Phelps described the extraction process used at the site, then summarized the results. 2-MBS was only detectable in two wells near the source of the plume, where toluene and xylene concentrations were relatively high. None was detected outside the plume or far downgradient within the plume.

Phelps also found 2-naphthoic acid (2-NA) at several points within the contaminant plume. The highest concentrations of 2-NA were found near the source of contamination. The concentration of 2-NA generally declined with distance from the source. Very low levels of 2-NA were present far downgradient in the plume.

To conclude, Phelps said his methodology indicated that both 2-MBS and 2-NA can be detected in the groundwater from a petroleum-contaminated aquifer. He added that the presence of 2-MBS and 2-NA correlate well to the probable areas of anaerobic toluene and naphthalene biodegradation. Both compounds can be useful biomarkers of in situ anaerobic biodegradation.

Phelps's presentation materials are included as Attachment H.

IN SITU CAPPING AS A FACILITATOR FOR IMPROVING IN SITU TREATMENT TECHNOLOGIES
Joseph Jersak, Hull & Associates, Inc.

Joseph Jersak's presentation materials are included as Attachment I. Jersak briefly introduced the various methods used to manage contaminated sediments, including ex situ and in situ options. Ex situ management typically involves removal (e.g. dredging) followed by sediment treatment (if appropriate) and subsequent disposal. In situ management options include natural recovery, capping, and treatment (by invoking chemical, biological, and/or immobilization processes). Jersak then briefly outlined National Contingency Plan criteria, noting that sediment-management option(s) ultimately chosen for a site would need to be evaluated against, and would need to be collectively consistent with, such criteria.

Jersak briefly outlined advantages as well as limitations associated with in situ treatment techniques in general (relative to sediment removal as the comparative remedial approach). Advantages of in situ treatment generally include: minimal environmental/habitat disturbance, minimal sediment exposure and handling, minimal losses of volatile organics, eliminating the need for sediment disposal facilities, and, consequently, lower costs. Limitations associated with in situ treatment generally include: a relative lack of process control typically slow biodegradation rates, potential environmental impacts of treatment chemicals and re-suspended sediments on the overlying water column, challenges in documenting treatment effectiveness, and potential sediment loss and re-distribution through erosion during sediment treatment.

In parallel fashion, Jersak then briefly outlined advantages as well as limitations associated with in situ capping techniques, again relative to employing the option of sediment removal. As with in situ treatment, advantages of in situ capping (regardless of whether granular or clay based capping material is used) generally include: minimal environmental/habitat disturbance, minimal sediment exposure and handling, minimal loss of volatile organics, eliminating the need for disposal facilities and, consequently, lower costs; another advantages is that in situ sediment caps are also relatively easy to install, repair, or replace, as needed. Limitations associated with in situ capping (again, regardless of what type of capping material is used) can include: some degree of sediment re-suspension during cap placement, bioturbation in and potentially through the placed cap, potential incompatibility of capping material with benthic organisms, and the fact that capping does not actively reduce contaminant mass within the encapsulated sediment mass. Additional limitations associated with in situ capping, particularly when granular materials like sands are used (instead of more cohesive and less permeable clay based materials) include: long-term diffusive and/or advective contaminant losses through the cap as well as erosional losses of capping material over time.

Jersak stated that a number of the limitations associated with in situ treatment and in situ capping may be overcome through combining the two technologies, particularly when using a relatively impermeable and erosion-resistant, clay based capping material. He then briefly described AquaBlok™ as such a clay based material. AquaBlok™ is a patented, composite-aggregate product, resembling small stones, which is generally comprised of a solid, dense core in combination with clay material (i.e. bentonite clay comprises a significant percentage of the clay material for typical product formulations, although formulations can instead include other clay minerals or clay sized materials as appropriate for specific project- and site-specific needs). Typical product use generally involves application of dry product masses through a water column and across the surface of contaminated sediments occurring in deepwater or wetland ecosystems. In a matter of days, the layer of initially discrete particles hydrates and expands, coalescing into a homogeneous, relatively cohesive, erosion-resistant, and low-permeability barrier between the contaminated sediments and the overlying water column.

By applying a relatively impermeable and resistant AquaBlok™ cap over the top of contaminated sediments, Jersak said, a more-or-less closed sediment system may be created (hydraulically speaking) such that the level of process control during implementing in situ treatment processes beneath the cap may be significantly increased, thus increasing overall treatment effectiveness. He first illustrated how such a hydraulically closed sediment system had been effectively created by AquaBlok™ capping of sediments in a large-scale laboratory testing column study. Jersak then gave several conceptual examples of how in situ treatment processes could be implemented within a variety of recharging or discharging hydrologic environments by using networks of reagent delivery and/or extraction piping systems. As a general example, he said, an integrated treatment approach may involve delivering or diffusing treatment reagents (such as oxidants, nutrients, chelators, pH adjusters, and/or microbes) into the sediment mass while inducing flow through sediments by concurrently extracting sediment pore waters and solubilized reaction products (including gases) from the sediment. A "funnel-and-gate-like" technique, involving a spatial configuration of relatively impermeable AquaBlok™ caps placed across selected portions of the sediment surface in combination with more permeable treatment "gates" placed over other selected areas, may be particularly effective where upwelling ground water conditions occur, and where natural ground water flow (along with entrained contaminants) could be directed through the sediment (beneath the cap) and ultimately through the treatment gates.

Jersak closed by saying that integrating in situ capping with in situ treatment may have other advantages in addition to increasing process control during in situ treatment. In particular, a general integration of these two technologies may also minimize potential environmental impacts associated with injecting treatment chemicals into sediments. Injecting treatment chemicals in an open (un-capped) sediment system may adversely impact the overlying water column; chemical injection through an already in-place cap using a "punch-like" injection device could greatly minimize diffusive chemical losses and also increase treatment effectiveness by keeping chemicals within the targeted sediment. Additionally, cap placement may also facilitate the monitoring of in situ treatment effectiveness by significantly minimizing confounding effects of naturally occurring processes like sediment erosion/deposition, contaminant fluxes, and bioturbation.

NEW TECHNIQUES FOR CONDUCTING IN SITU STUDIES
John Smith, Alcoa

John Smith described a site on the Grasse River in upstate New York. The site, a 6-mile stretch of the river flowing from an Alcoa facility to the St. Lawrence River, is part of the Great Lakes drainage basin. PCBs are present at concentrations ranging from 1 ppm to more than 1,000 ppm, with higher concentrations at depth. After three years of study, Alcoa has determined that the contamination is not confined to a localized area. Investigators have found that the PCB count is higher further downstream. Also it appears that PCB contamination is within the top 3 inches of the sediment and averages 15 ppm. Smith said that PCBs seem to be diffusing through the water column.

Smith said that various remedial technologies are being evaluated and negotiated by Alcoa and EPA Region 2. Options being considered range from in-place containment to dredging. He also said that a combination of these two approaches is being considered. Regardless of which approach is chosen, one thing is certain: material will be left behind in the river.

Smith said that evidence collected in the laboratory and the field suggests that PCB dechlorination is occurring at the Grasse River site. (BZ-4, a prime dechlorination product of Aroclor-1248 and -1260, has been detected. In addition, higher than expected biphenyl concentrations have been detected.) Smith said that Alcoa is interested in exploring the anaerobic activity that is destroying PCB mass at the site. Thus, he proposed initiating a 5- to 10-year monitoring study of in situ microcosms to determine the long-term fate of PCBs. The study would look at intrinsic natural processes, such as absorption and biodegradation. Enhanced processes of absorption and biodegradation would also be studied. He said that Alcoa would like to initiate the research activities by excavating some of the sediment, homogenizing it in a slurry reactor, and filling 100 to 150 2- to 4-inch tubes with the site's sediment. The tubes would be placed in the Grasse River; four or five would be removed once every year or two years and sliced every centimeter to see what is happening with depth and mass reduction. The tubes would be placed at the surface of the sediment with a half inch exposed, so some natural sedimentation would occur. Smith also suggested using a 6-inch particle broadcasting cap. If the results show that significant mass destruction is occurring, Smith said, regulators would probably be impressed by the efficacy of natural processes.

In closing, Smith said that he believes the RTDF's legacy should be to establish long-term monitoring programs. He feels that the group should address sediment heterogeneity in conjunction with concurrent laboratory studies. Smith stressed that in situ approaches require long-term monitoring data to prove or disprove effectiveness. Most of the technologies need to demonstrate long-term effectiveness. Alcoa would be receptive to collaboration if it decides to proceed with long-term monitoring projects at the Grasse River site.

ACTION ITEMS THAT RESULTED FROM THE BRAINSTORMING SESSION

The Action Team members held a brainstorming session. They identified the following as action items:

• Kelly Madalinski and his colleagues at EPA will set up a conference call with those interested in a Great Lakes field demonstration site.
• 
  Dick Jensen plans to establish teams of RTDF members to "go the next step" and discuss partnership arrangements, as well as the future of demonstration projects and possible sites for laboratory demonstrations.
• 
  Jensen suggested assembling a group to "iron out" issues that have been brought up about geochemical remediation processes.
• 
  Henry Tabak asked the group to narrow the choices for demonstration sites, prioritize contaminants, and decide if changes in bioavailability should be a remedial goal.
• 
  Jensen will convene a conference call with Joe Jersak and Brian Senefelder to discuss combining capping with chemical treatment for demonstration.
• 
  Jensen will convene a conference call with Tabak to talk more about what EPA is doing at NRMRL and how members of RTDF can integrate the research into their work.
• 
  Jensen will convene a conference call for anyone interested in geochemical oxidation of PAHs.

Attachment A: Final List of Participants

RTDF Sediments Remediation
Action Team Meeting

Double Tree Hotel
Wilmington, Delaware
September 12-13, 2000

Attachments B through I

Attachment B: Welcome and Opening Remarks (Richard Jensen)

Attachment C:
     Interstate Technology and Regulatory Cooperation
     Assessment of Monitored Natural Recovery (MNR) (Richard Jensen)

Attachment D: In Situ Sediment Treatment Technology (Brian Senefelder)

Attachment E: ElectroChemical Remediation of Sediments (Joe Iovenitti)

Attachment F: Membrane Delivery Technology:
     Introduction,
     Biorestoration Using Membranes,
     Gel Entrapped Microorganisms,
     Chemical Binding,
     Conclusions (Henry Tabak)

Attachment G: In Situ Stabilization of PAHS: Lessons From Nature (Upal Ghosh)

Attachment H:
      Metabolic Biomarkers As Indicators For Anaerobic In Situ Remediation of BTEX and PAHS,
     In Situ Bio-Markers (Craig Phelps)

Attachment I: In Situ Treatment using AquaBlok™ (Joe Jersak)