Road Map to Understanding Innovative Technology Options for Brownfields Investigation and Cleanup

The information presented below is intended to help brownfields stakeholders better understand the types of contaminants typically found at brownfields sites and the range of technologies that may be appropriate for assessing and remediating those contaminants during the various phases of a site cleanup.

What Are the Causes of Contamination at Brownfields Sites?

Section 101 of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) defines brownfields sites as “real property, the expansion, redevelopment, or reuse of which may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant.” Almost any former property, industrial or nonindustrial, where chemicals were used, produced, or reclaimed is a potential brownfields site. Over the operational history of the site or through its current use, contamination may have resulted from use, storage, or disposal of various products or chemicals. Some of the products commonly used or generated at the sites that may have resulted in contamination of structures, soils, or groundwater include the following:

A wide variety of chemical contaminants may be present at brownfields sites. The following tables present information on the sites, typical contaminants, and investigative and remedial technologies:

Seven general contaminant groups are included in Tables A-1, A-2, and A-3. Descriptions of the seven contaminant groups have been included at the end of this guide to provide supplemental information about them. In addition, supplemental information about treatment technologies described in Table A-3 also has been included at the end of this guide.

The information in this guide was obtained from various U.S. Environmental Protection Agency (EPA) sources. It is intended to provide general information on brownfields sites, contaminants, and technologies and is not intended to be all-inclusive. Contaminants and activities associated with common brownfields site types may not be relevant to every site. Additionally, investigation and remediation technologies may not be appropriate for the listed contaminants in all situations. Stakeholders should consult EPA or state officials, qualified professionals, and other sources of information when proceeding with redevelopment activities.

What Types of Contaminants Are Found at Brownfields Sites?

Various contaminants potentially may be present at brownfields sites. Table A-1 lists common brownfields site types, activities that may have lead to contamination over the operational history of these sites, and the contaminant groups typically associated with these activities. In this guide, contaminant groups are presented rather than the specific contaminants. Information about the contaminant groups is included below under What Are the Contaminant Groups Presented in Tables A-1, A-2, and A-3? Please note that if a contaminant group is listed, it does not imply that all the contaminants within a particular group are associated with each site type.

Agricultural Feed supply and other agricultural chemical distribution points may be contaminated with fertilizers, pesticides, and herbicides. Groundwater, drainage area sediments, soils, and nearby surface waters may be contaminated with pesticides and herbicides and could exhibit elevated levels of nitrate from fertilizer runoff. Contamination at agricultural sites may also arise from chemicals used to operate, clean, and maintain farm equipment such as fuel, oil, grease, and solvents.	x	x	x	x		x
Battery recycling and disposal Battery recycling and disposal facilities regenerate, reclaim, and dispose of used batteries. Many batteries contain toxic constituents such as lead, mercury, and cadmium. The metal in used batteries is separated from other battery constituents and processed for reuse. Lead-acid automobile batteries must be “broken” to reclaim the lead within. In battery breaking, the top of the battery casing is removed, the sulfuric acid solution inside is drained, and the lead components are separated from the casing. The remaining battery casing may be rinsed prior to disposal in order to remove residual lead oxide. Discarded acid and rinse water may be stored in lagoons or tanks. Chemicals may be released to soil and groundwater by leaking tanks or through spillage during the breaking process. Discarded casings may be buried. Any metal remaining on buried, discarded casings may leach into soil and groundwater. The extracted metal must be smelted prior to reuse. Particulate matter emitted by the smelter may contaminate nearby surface soil.						x
Chemical and dye manufacturing A wide range of chemicals are used and generated in facilities that manufacture, reformulate, and package various chemicals and dyes for commercial and industrial use. The types of contaminants released depend on the raw materials, processes, equipment and maintenance practices used. Environmental contamination resulting from chemical and dye manufacturing may persist in nearby or downstream surface waters or sediments long after operations have ceased. Moreover, chemical operations can change over time or involve multiple processes; therefore, the sites may be overlaid with several generations of wastes from a variety of products or processes. Many chemical facilities also have quality assurance and research laboratories that use small quantities of toxic chemicals that could contaminate isolated locations.	x	x	x	x
Chlor-alkali manufacturing Chlor-alkali plants produce a variety of chemicals, including chlorine, caustic soda, hydrochloric acid, sodium hypochlorite, sodium hydrosulfite, salt, hydrogen, sulfur dioxide, and spent sulfuric acid. Three basic processes are used for the manufacture of chlorine and caustic soda from brine: the mercury cell, diaphragm cell, and membrane cell processes. The mercury cell process uses elemental mercury as the cathode and produces mercury-contaminated wastewater, solid waste, and gaseous emissions. The process and waste streams must be carefully controlled to prevent the release of mercury to the environment. The diaphragm cell process may use lead or graphite anodes and asbestos diaphragms and may generate chlorinated hydrocarbons as a by-product. The membrane cell process is the most modern and has economic and environmental advantages. The primary by-product of the membrane cell process is dilute hydrochloric acid, which must be neutralized before it is discharged into the environment.	x		x			x
Cosmetics manufacturing Cosmetics are mixtures of surfactants, oils, and other ingredients. Cosmetics may contain mineral or metallic and nonmetallic additives. In sunscreen, for example, titanium and zinc are used as sun blockers. The color of makeup is determined by the concentrations and ratio of black or red iron oxide, titanium dioxide, and/or zinc oxide. Metal dyes are used in fingernail polish. The uses and concentrations of heavy metals play an important role in cosmetics production and a primary environmental concern at these site types.	x	x				x
Drum recycling Drum recycling facilities clean used drums for reuse. Soil and groundwater contamination at these facilities may result from leaking and spilling of residual chemicals and oils. The variety of chemicals stored in drums makes characterizing potential contaminants difficult. Contaminants could include acids, bases, corrosives, reactive chemicals, flammable materials, and oils. Spillage of paint, paint thinners, and solvents can also contaminate drum recycling facilities.	x	x	x	x	x	x
Dry cleaning The dry cleaning industry provides garment cleaning and related services such as clothes pressing and finishing. The dry cleaning process is physically very similar to the home laundry process except that clothes are washed in dry cleaning solvent instead of water. Dry cleaning sites may become contaminated because of leaks, spills, and improper disposal of solvents.	x	x
Gasoline stations Gasoline stations consist of pump islands, underground storage tanks (UST) for fuel, small storage areas, and service areas (which typically contain either hydraulic lifts or pits) for changing automobile engine oil and other maintenance activities. Gasoline and diesel fuel are transferred from bulk tank trucks to large USTs. Spills at the transfer areas and pumps along with overfilling of and leakage from the USTs are likely sources of contamination at gasoline stations. The primary contaminants of concern at gasoline stations include petroleum hydrocarbons; Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX); and fuel oxygenates such as methyl tertiary butyl ether. Service areas typically have small containers of ethylene glycol (coolant), hydraulic oils, lubricants, automotive batteries (lead and acid), and compressed gas especially acetylene and oxygen cylinders for welding operations. Surface soils may be contaminated because of historical spills or dumping of used lubricants, coolants, and cleaning solvents generated during service activities. Subsurface soils and groundwater, especially in the vicinity of USTs, may also be contaminated because of spills, overfilling, and leaks.		x		x	x	x
Glass manufacturing The glass industry consists of firms engaged in primary glass manufacturing and of others that create products using purchased glass. The primary contaminants associated with glass manufacturing are metals such as lead, arsenic, chromium, and others. Other chemicals used in the glass manufacturing process include hydrofluoric acid, sulfuric acid, and various organic and inorganic solvents. Contaminants may be released to the environment through spills and leaks of raw materials and plant maintenance waste as well as insufficiently treated air emissions.						x
Hospitals Hospitals use a variety of toxic chemicals for diagnostic and therapeutic procedures as well as for cleaning and sterilization. Hazardous materials used include chemotherapy and antineoplastic chemicals, formaldehyde, photographic chemicals, radionuclides, solvents, mercury, anesthetic gases, and other toxic or corrosive chemicals. These substances may be released to the environment through leaks and spills, improper disposal of wastes, and insufficient treatment of wasterwater. In addition, medical waste incinerators may release mercury into the air.	x	x				x
Incinerators An incinerator is an enclosed device that uses controlled flame combustion to thermally break down waste to an ash residue that contains little or no combustible material. Incinerators may accept specific wastes such as municipal solid waste, sewage sludge, or medical waste. Contamination from incinerators may be associated with storage and handling of waste materials prior to incineration as well as disposal of ash and other by-products of the combustion process.			x			x	x
Landfills, municipal and industrial Landfills are now restricted to household garbage, yard wastes, construction debris, and office wastes. Prior to 1970, however, landfills could accept industrial wastes. Therefore, older landfills are more likely to be contaminated with hazardous chemicals. Even modern landfills can contain a host of chemicals from household wastes such as oils, paints, solvents, corrosive cleaners, batteries, and gardening products. Illegal dumping at landfills can also cause serious contamination. Improperly designed landfills have a higher likelihood of surface soil and groundwater contamination and may trap explosive levels of methane gas and hydrogen sulfide in the soil.	x	x	x	x	x	x
Leather manufacturing Leather tanning is the process of converting raw hides or skins into leather. Hides and skins absorb tannic acid and other chemical substances that prevent them from decaying, make them resistant to wetting, and keep them supple and durable. Tanning is essentially the reaction of collagen fibers in the hide with tannins, chromium, alum, or other chemical agents. The most common tanning agents used in the United States are trivalent chromium and vegetable tannins extracted from certain tree barks. Alum, syntans (manmade chemicals), formaldehyde, glutaraldehyde, and heavy oils are also used as tanning agents.					x	x
Machine shops and metal fabrication The fabricated metal product industry has facilities that generally perform two functions: forming metal shapes and performing metal finishing operations, including surface preparation. Metal fabricators produce ferrous and nonferrous metal products. Machining and other metal working may generate waste metals, lubricants, cleaners, and other materials. These substances may impact soil, groundwater, and surface water if they are spilled, leaked, or improperly disposed.	x	x	x			x
Manufactured gas plants and coal gasification Manufactured gas has been produced as a fuel source from coal and oil since the early 1800s. Typically, coal or oil is heated and the resulting volatilized gases are distilled to produce natural gas. Depending on the process design, various by-products can be recovered, including anthracene, benzene, cresol, naphthalene, paraffin, phenol, toluene, and xylenes. Waste products from manufactured gas operations include coal fines, coal tar, cyanide salts, hydrogen sulfide gas, ammonia, and wastewater. Leakage and spillage from storage drums or tanks may contaminate surface and subsurface soils, sediments, surface water, and groundwater.		x		x	x	x
Marine maintenance Marine maintenance industry establishments engage in general painting and repair of ship or boat structures and engines or power plants. Activities may include painting, servicing engines, structural repairs, engine or power plant maintenance, electroplating, air conditioning and refrigeration service, electrical repair, and other cleaning and repair services. A number of chemicals may be used at marine maintenance facilities, including chemical paint strippers, blast media, antifouling paints, solvents, carburetor cleaner, cutting fluids, acids and alkalis, cyanide, heavy metal baths, fiberglass and reinforcement, resins, and mold release agents.	x	x				x
Metal plating and finishing Metal plating operations improve a product’s performance (for example its durability or corrosion resistance) or appearance. Metal components are first cleaned (using solvents and/or water-based detergents) to remove dirt and oils from manufacturing operations. The metal components are subsequently etched, plated, and finished in a series of vats or baths. Common plating metals include cadmium, chromium, copper, gold, nickel, silver, and their alloys. Spillage during plating and cleaning operations and leakage or overflows from storage tanks and process vats may contaminate concrete floors and underlying soils. Groundwater may also be contaminated by heavy metals, cyanide, and solvents.	x	x	x	x		x
Metal recycling and automobile salvage Automobile salvage yards recover usable parts, scrap metal, and other recyclable materials from old or wrecked automobiles. Nonrecyclable materials are stored on site or sent to a municipal landfill. Metal recyclers purchase metal from a variety of sources and sort and process the scrap metal for resale. Metals commonly salvaged by these facilities include iron, steel, copper, brass, and aluminum. Sites may contain non-recyclable wastes and contaminated materials. Contaminated “auto fluff”, a fibrous residue containing plastics, fabrics, and other materials, may be present at sites that perform shredding. Depending on the type of recycling operation conducted at a site, the surrounding soils may be contaminated with heavy metals, asbestos, polychlorinated biphenyls (PCB) oils, hydraulic fluids, lubricating oils, fuels, and solvents.			x		x	x
Munitions manufacturing and ordnance sites Ordnance sites typically include facilities that manufacture, assemble, store, or dispose of a variety of military munitions such as bombs, shells, grenades, mines, small arms ammunition, and specialty explosives. Potential contaminants in structures and surrounding property include di- and tri-nitro substituted phenols and benzenes, nitroglycerin, metals, ethers, formaldehyde, and ammoniated compounds. Unexploded ordnance (UXO) may be buried along with other waste materials. Groundwater may be contaminated with solvents such as formaldehyde and toluene. Furthermore, because of the age of some facilities, asbestos-containing materials may be found in abandoned buildings and demolition debris.						x	x
Mining There are three general steps in the mining process: extraction, beneficiation, and processing. Extraction of the mineral value from the rock or matrix is the initial step in the operation. Beneficiation is the processing of extracted materials to clean or concentrate the product either for use as a final product or in preparation for further processing. Beneficiation may involve physical (such as milling) or chemical (such as leaching) separation processes or both. Processing is conducted following beneficiation to further extract or refine the material and prepare it for specific uses. Processing may include a variety of operations such as smelting, refining, roasting and digesting. Chemical contamination at mining sites may result from acidic, metal-laden mine drainage. Spilled, leaked, or improperly disposed of petroleum, lubricants, and other industrial chemicals may also result in site contamination.	x				x	x
Painting and automobile body repair Paint shops and automobile body repair shops paint various plastic and metal products and fix truck and automobile body parts. Damaged automobile body parts are replaced or repaired with fillers and are then sanded, primed, and painted. The shops may use cutting torches, welding equipment, solvents and cleaners, fiberglass, various polymers and epoxy compounds, and sand or grit blasting. Gasoline and diesel from vehicle fuel tanks, solvents, cleaners, acids, and paints may be leaked or spilled, contaminating soils and groundwater. Typical contaminants include toluene, acetone, perchloroethylene, xylene, gasoline and diesel fuel, carbon tetrachloride, and hydrochloric and phosphoric acids.	x	x			x	x
Pesticide manufacturing and use A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. The term pesticide also applies to herbicides, fungicides, and various other substances used to control pests. Spillage, leakage, and improper storage or disposal of pesticides may result in their release to the environment. Sites may also be contaminated with properly applied but persistent pesticides. Because of the wide variety of pesticides and applications, facilities manufacturing or using pesticides may be contaminated with a broad range of chemicals.	x	x	x	x	x	x
Petroleum refining and reuse Oil production facilities consist of oil drilling, refining, storage, transfer, transport, and recycling facilities. Typical materials present at these facilities include crude, fuel, and motor oils as well as waste oils. Production processes at these facilities may contaminate soils with sludges, acids, and waste oil additives as well as co-contaminants such as PCBs when spills, leaks or improper disposal practices occur. In some cases,disposal pits may contain thick tarry sludges with very high pH values. Groundwater and deeper soil may be contaminated with metals and lighter oil fractions such as BTEX.					x	x
Pharmaceutical manufacturing The pharmaceutical industry manufactures bulk pharmaceutical intermediates and active ingredients, that are further processed into finished products. Chemicals used in the manufacturing process vary according to the desired product and the process type. Equipment must be thoroughly cleaned between processing operations for different products. VOCs are used as solvents at various stages of the manufacturing process. Because of the purity required for products, spent solvent is not usually reused in pharmaceutical manufacturing. It may be sold for nonpharmaceutical use or destroyed via incineration. The ten contaminants most commonly discharged in pharmaceutical wastewater are methanol; ethanol; acetone; isopropanol; acetic acid; methylene chloride; formic acid; ammonium hydroxide; N,N-dimethylacetamide and toluene.	x	x				x
Photographic film manufacturing and development Photographic film is coated with an emulsion containing light-sensitive silver halide crystals. Once film has been exposed, it must go through a series of chemical processes to bring out the images. Various chemicals are used as developers and fixing solutions, including hydroquinone, catechols, aminophenols, acetic acid, muriatic (hydrochloric) acid, and sodium or ammonium thiosulfate. Silver solutions are often generated during the photographic development processes.	x	x		x		x
Plastic manufacturing Almost all plastics are made from petroleum. Plastics are polymers, which are very long chains of molecules that consist of subunits (monomers) linked together by chemical bonds. Monomers of petrochemical plastics are not typically biodegradable. Wastes generated by the industry include polymers, phthalates, cadmium, solvents, resins, chemical additives, and VOCs.	x	x		x		x
Printing and ink manufacturing The printing industry consists of firms engaged in printing using one or more common processes such as lithography, letterpress, flexography, gravure, and screen printing. Contamination may result from spills, leaks, and improper disposal of excess chemicals and wastes, including ink constituents such as metals, cleaners, and solvents used during printing and production processes.	x	x			x	x
Railroad yards Railroad yards may consist of any combination of track and switching areas, engine maintenance buildings, engine fueling areas, bulk and container storage and transfer stations, and storage areas for materials used in track and engine maintenance. Materials used at railroad yards include diesel fuel, paint, solvents and degreasing agents, PCB oils, and creosote. Spills, leaks, or dumping of these compounds may contaminate soil and groundwater. Chemical spills and leaks during loading and unloading of tanker and freight cars can also contaminate a railroads yard. Because of the variety of chemicals used at and transported through railroad yards, virtually any type of chemical contamination could be present.	x	x	x	x	x	x
Research and educational institutions Academic institutions are often similar to small cities, as they may have research laboratories, automobile repair facilities, power plants, wastewater treatment plants, hazardous waste management and trash disposal activities, asbestos management activities, drinking water supply facilities, grounds maintenance activities and incineration facilities. Educational institutions typically generate small quantities of a variety of wastes, including inorganic acids, organic solvents, metals and metal dust, photographic waste, waste oil, paint, heavy metals, and pesticides.	x	x	x			x
Semiconductor manufacturing >The semiconductor manufacturing industry is a subset of the electronics manufacturing industry and produces integrated circuits or “chips.” Contamination on semiconductor chips is one of the primary reasons that they fail; therefore, chips are cleaned before and after many of the manufacturing steps. Chemicals used in the manufacturing process include various acids, ethylene glycol, hydroxide solutions, halogen gases, fluorocarbons, chlorine, and various organic solvents.	x	x				x
Smelter operations The primary use of smelting is to produce iron and steel from iron ore. Smelting is also used to extract copper and other base metals from raw ores. Contamination from smelting operations often takes the form of deposition of airborne metals, asbestos, and sulfur compounds in areas surrounding smelters. Contamination may also result from improper storage and disposal of raw ores or by-product slag.						x
Underground storage tanks A UST is a tank and any underground piping connected to a tank where at least 10 percent of the combined volume is under the ground. USTs often contain petroleum products, gasoline, or other chemicals. Faulty installation or inadequate operating and maintenance procedures can cause USTs to release their contents into the environment. The greatest potential hazard from leaking USTs is that petroleum fuels, fuel additives, or other hazardous substances can seep into soil and contaminate groundwater.	x	x			x	x
Vehicle maintenance Vehicle maintenance involves handling and managing a wide variety of materials and wastes, including oils, batteries, refrigerants, antifreeze, solvents, asbestos, and fuels. Improper management and disposal of wastes as well as leaks from fuel and waste storage containers may result in contamination of vehicle maintenance facilities.	x	x			x	x
Wood preservation Wood preservation sites typically consist of wood preparation facilities, chemical storage tanks, chemical treatment areas (including high-pressure vessels in many cases), drip or drying areas, and wood storage areas. Wood is treated with preservative chemicals either by dipping the wood into a chemical bath or by injecting chemicals into the wood under pressure. Storage tanks at wood preservation sites could contain creosote, pentachlorophenol, or chrome-copperarsenate (CCA) solutions for wood treatment. These chemicals could enter the environment if the tanks were overfilled or leaked. Contaminated water squeezed from wood during processing and retort sludge may have spilled on the ground, causing soil and ground water contamination. As treated wood is transferred from the treatment area to the drying area, chemicals may drip onto soil and contaminate the soil and groundwater. Likewise, drippage in drying areas, especially in older operations where pressure treatment may not have been used, could result in soil contamination. Runoff from site could also contaminate nearby surface waters.		x	x	x	x	x
Wood pulp and paper manufacturing The pulp and paper industry produces commodity grades of wood pulp, printing and writing paper, sanitary tissue, industrial-type paper, containerboard, and boxboard using cellulose fiber from timber or purchased or recycled fibers. The two steps involved are pulping and paper or paperboard manufacturing. Pulping is the process of dissolving wood chips into individual fibers using chemical, semichemical, or mechanical methods. Pulping is the major source of environmental impacts in the industry. Chlorinated organic compounds in pulp plant wastewater sludge are of particular concern because of their tendency to partition from effluent to solids. Improper treatment or disposal of wastes may result in contamination being released to the environment. Spills and leaks of process and waste chemicals are other common sources of contamination at pulp mills. Air emissions are also problematic at pulp mills, which are typically noted for their unpleasant odors.	x		x

What Technologies May Be Used to Investigate Contamination at Brownfields Sites?

Various analytical technologies may be used to investigate contamination at brownfields sites. Table A-2 contains information on analytical technologies that are available for investigating the contaminant groups presented in Table A-1.

What Technologies May Be Used to Remediate at Brownfields Sites?

Various treatment technologies may be used to remediate contamination at brownfields sites. Table A-3 contains information on treatment technologies that are available for remediating the contaminants presented in Table A-1. Descriptions of the remedial technologies are included at the end of this guide in What Are the Treatment Technologies Identified in Table A-3?

Table A-3. Technologies for Treating Contaminants Found at Brownfields Sites

Notes:
S and G indicate the media that can be treated using each technology type
S = Soils, sediments, and sludges
G = Groundwater, leachate, and surface water

What Are the Contaminant Groups Presented in Tables A-1, A-2, and A-3?

The following general contaminant groups are included in Tables A-1, A-2, and A-3:

Descriptions of the seven contaminant groups are included below to provide supplemental information about the characteristics and specific constituents of the groups.

Halogenated VOCs

VOCs are hydrocarbon compounds that evaporate readily at room temperature A halogenated VOC is a VOC that has a halogen (fluorine, chlorine, bromine, or iodine) attached to it. Locations where halogenated VOCs may be found include burn pits, chemical manufacturing plants and disposal areas, contaminated marine sediments, disposal wells and leach fields, electroplating and metal finishing shops, firefighting training areas, hangars and aircraft maintenance areas, landfills and burial pits, leaking storage tanks, radioactive and mixed waste disposal areas, oxidation ponds and lagoons, dry cleaning shops, grain storage sites, paint stripping and spray booth areas, pesticide and herbicide mixing areas, solvent degreasing areas, surface impoundments, and vehicle maintenance areas. Typical halogenated VOCs encountered at many sites include those listed below.

Nonhalogenated VOCs

A nonhalogenated VOC is a VOC that does not have a halogen (fluorine, chlorine, bromine, or iodine) attached to it. Locations where nonhalogenated VOCs may be found include burn pits, chemical manufacturing plants and disposal areas, contaminated marine sediments, disposal wells and leach fields, electroplating and metal finishing shops, firefighting training areas, hangars and aircraft maintenance areas, landfills and burial pits, leaking storage tanks, radioactive and mixed waste disposal areas, oxidation ponds and lagoons, paint stripping and spray booth areas, pesticide and herbicide mixing areas, solvent degreasing areas, surface impoundments, and vehicle maintenance areas. Typical nonhalogenated VOCs (excluding fuels, BTEX, and gas-phase contaminants) encountered at many sites include those listed below:

Halogenated SVOCs

SVOCs are hydrocarbon compounds with boiling points greater than 200ºC. A halogenated SVOC is an SVOC that has a halogen (fluorine, chlorine, bromine, or iodine) attached to it. Locations where halogenated SVOCs may be found include burn pits and other combustion sources, chemical manufacturing plants and disposal areas, contaminated marine sediments, disposal wells and leach fields, electroplating and metal finishing shops, firefighting training areas, hangars and aircraft maintenance areas, landfills and burial pits, leaking storage tanks, radioactive and mixed waste disposal areas, oxidation ponds and lagoons, dry cleaning shops, grain storage sites, pesticide and herbicide mixing areas, solvent degreasing areas, surface impoundments, vehicle maintenance areas and wood preservation sites. Typical halogenated SVOCs (excluding fuels and explosives) encountered at many sites include those listed below:

Pesticides are a subgroup of halogenated SVOCs. Typical pesticides encountered at many sites include those listed below.

Nonhalogenated SVOCs

A nonhalogenated SVOC is an SVOC that does not have a halogen (fluorine, chlorine, bromine, or iodine) attached to it. Locations where nonhalogenated SVOCs may be found include burn pits, chemical manufacturing plants and disposal areas, contaminated marine sediments, disposal wells and leach fields, electroplating and metal finishing shops, firefighting training areas, hangars and aircraft maintenance areas, landfills and burial pits, leaking storage tanks, radioactive and mixed waste disposal areas, oxidation ponds and lagoons, pesticide and herbicide mixing areas, solvent degreasing areas, surface impoundments, and vehicle maintenance areas and wood preservation sites. Typical nonhalogenated SVOCs (excluding fuels and explosives) encountered at many sites include those listed below:

Fuels

Fuels are a general class of chemicals created by refining and manufacturing petroleum or natural gas for use in combustion processes to generate heat or other energy. Fuels include nonhalogenated VOCs, nonhalogenated SVOCs, or both. Sites where fuel contamination may be found include aircraft, storage and service areas, burn pits, chemical disposal areas, contaminated marine sediments, disposal wells and leach fields, firefighting training areas, hangars and aircraft maintenance areas, landfills and burial pits, leaking storage tanks, solvent degreasing areas, surface impoundments, and vehicle maintenance areas. Typical fuel contaminants encountered at many sites include those listed below:

Metals and Metalloids

Metals are one of the three groups of elements distinguished by their ionization and bonding properties, along with metalloids and nonmetals. Metals have certain characteristic physical properties: they are usually shiny, have a high density, are ductile and malleable, usually have a high melting point, are usually hard, and conduct electricity and heat well. Metalloids have properties that are intermediate between those of metals and nonmetals. There is no unique way of distinguishing a metalloid from a true metal, but the most common way is that metalloids are usually semiconductors rather than conductors. Locations where metals and metalloids may be found include artillery and small arms impact areas, battery disposal areas, burn pits, chemical disposal areas, contaminated marine sediments, disposal wells and leach fields, electroplating and metal finishing shops, firefighting training areas, landfills and burial pits, leaking storage tanks, radioactive and mixed waste disposal areas, oxidation ponds and lagoons, paint stripping and spray booth areas, sand blasting areas, surface impoundments, and vehicle maintenance areas. Typical metals and metalloids encountered at many sites include those listed below.

Explosives

Most commonly, artificial explosives are chemical explosives manufactured for use as explosives and propellants. Sites where explosive contaminants may be found include artillery impact areas, contaminated marine sediments, disposal wells, leach fields, landfills, burial pits, and TNT washout lagoons. Typical explosive contaminants encountered at many sites include those listed below.

What Are the Treatment Technologies Identified in Table A-3?

Table A-3 contains information on treatment technologies for remediating brownfields sites. Descriptions of these remedial technologies are presented below.

Air Sparging involves injection of air or oxygen into a contaminated aquifer. Injected air traverses horizontally and vertically in channels through the soil column, creating an underground stripper that removes volatile and semivolatile organic contaminants by volatilization. The injected air helps to flush the contaminants into the unsaturated zone. Soil Vapor Extraction (SVE) usually is implemented in conjunction with air sparging to remove the generated vapor-phase contamination from the vadose zone. Oxygen added to the contaminated groundwater and vadose zone soils also can enhance biodegradation of contaminants below and above the water table.

Bioremediation involves use of microorganisms to degrade organic contaminants in soil, sludge, solids, and groundwater either in situ or ex situ. It can also be used to make metals or metalloids less toxic or mobile. When organic contaminants are being treated, the microorganisms break down contaminants by using them as a food source by cometabolizing them with a food source. Aerobic processes require an oxygen source, and the end products typically are carbon dioxide and water. Anaerobic processes are conducted in the absence of oxygen, and the end products can include methane, hydrogen gas, sulfide, elemental sulfur, and nitrogen gas. Ex situ bioremediation technologies for groundwater typically involve treating extracted groundwater in a bioreactor or constructed wetland. In situ techniques stimulate and create a favorable environment for microorganisms to grow and use contaminants as a food and energy source or to cometabolize them. Generally this process involves providing some combination of oxygen, nutrients, and moisture and controlling the temperature and pH. Microorganisms that have been adapted for degradation of specific contaminants are sometimes applied to enhance the process. For treatment of metals and metalloids, the process involves biological activity that promotes formation of less toxic or mobile species by creating ambient conditions that will cause such species to form or by acting directly on the contaminant. The treatment may result in oxidation, reduction, precipitation, coprecipitation, or another transformation of the contaminant.

Chemical treatment, also known as chemical reduction/oxidation (redox), typically involves redox reactions that chemically convert hazardous contaminants into compounds that are nonhazardous, less toxic, more stable, less mobile, or inert. Redox reactions involve the transfer of electrons from one compound to another. Specifically, one reactant is oxidized (loses electrons) and one reactant is reduced (gains electrons). The oxidizing agents used for treatment of hazardous contaminants in soil include ozone, hydrogen peroxide, hypochlorites, potassium permanganate, Fenton’s reagent (hydrogen peroxide and iron), chlorine, and chlorine dioxide. This method may be applied in situ or ex situ to soils, sludges, sediments, and other solids and may also be applied to groundwater in situ or ex situ chemical treatment using pump and treat technology. Chemical treatment may also include use of ultraviolet (UV) light in a process known as UV oxidation.

Electrokinetics is based on the theory that a low-density current will mobilize contaminants in the form of charged species. A current passed between electrodes is intended to cause aqueous media, ions, and particulates to move through soil, waste, and water. Contaminants arriving at the electrodes can be removed by means of electroplating or electrodeposition, precipitation or coprecipitation, adsorption, complexing with ion exchange resins, or pumping of water (or other fluid) near the electrodes.

For Flushing, a solution of water, surfactants, or cosolvents is applied to soil or injected into the subsurface to treat contaminated soil or groundwater. When soil is being treated, injection is often designed to raise the water table into the contaminated soil zone. Injected water and treatment agents are recovered together with flushed contaminants.

Both on-site and off-site Incineration involves use of high temperatures (870 to 1,200°C or 1,600 to 2,200°F) to volatilize and combust (in the presence of oxygen) organics in hazardous wastes. Auxiliary fuels are often used to initiate and sustain combustion. The destruction and removal efficiency of properly operated incinerators exceeds the 99.99 percent requirement for hazardous waste and can meet the 99.9999 percent requirement for PCBs and dioxins. Off-gases and combustion residuals generally require treatment. On-site incineration is typically a transportable unit; for off-site incineration, waste is transported to a central facility.

For In-well air stripping, air is injected into a double-screened well, causing the VOCs in the contaminated groundwater to be transferred from the dissolved phase to the vapor phase in air bubbles. As the air bubbles rise to the surface of the water, the vapors are drawn off and treated by a SVE system.

Mechanical soil aeration involves agitation of contaminated soil by using tilling or other means to volatilize contaminants.

Multi-phase extraction involves use of a vacuum system to remove various combinations of contaminated groundwater, separate-phase petroleum product, and vapors from the subsurface. The system typically lowers the water table around a well, exposing more of the formation. Contaminants in the newly exposed vadose zone are then accessible for vapor extraction. Once above ground, the extracted vapors or liquid-phase organics and groundwater are separated and treated.

Open burn (OB) and Open detonation (OD) operations are conducted to destroy excess, obsolete, or unserviceable (EOU) munitions and other items containing explosives, propellants, and other energetic materials. In OB operations, materials are destroyed by self-sustained combustion, which is ignited by an external source, such as a flame, heat, or a detonation wave. In OD operations, materials are destroyed by detonation, which generally is initiated by an energetic charge.

Permeable reactive barriers, also known as passive treatment walls, are installed across the flow path of a contaminated groundwater plume, allowing the water portion of the plume to flow through the wall. These barriers allow passage of water while prohibiting movement of contaminants by means of treatment agents within the wall such as zero-valent metals (usually zero-valent iron), chelators, sorbents, compost, and microbes. The contaminants are either degraded or retained in a concentrated form by the barrier material, which may need to be replaced periodically.

Physical separation processes use physical properties to separate contaminated and uncontaminated media or to separate different types of media. For example, different-sized sieves and screens can be used to separate contaminated soil from relatively uncontaminated debris. Another application of physical separation is dewatering of sediments or sludge.

Phytoremediation is a process in which plants are used to remove, transfer, stabilize, or destroy contaminants in soil, sediment, or groundwater. The mechanisms of phytoremediation include enhanced rhizosphere biodegradation (which takes place in soil or groundwater immediately around plant roots), phytoextraction (also known as phytoaccumulation, the uptake of contaminants by plant roots and the translocation and accumulation of contaminants into plant shoots and leaves), phytodegradation (metabolism of contaminants within plant tissues), and phytostabilization (production of chemical compounds by plants to immobilize contaminants at the interface of roots and soil). The term phytoremediation applies to all biological, chemical, and physical processes that are influenced by plants (including the rhizosphere) and that aid in the cleanup of contaminated substances. Phytoremediation may be applied in situ or ex situ to soils, sludges, sediments, other solids, or groundwater.

Pump and treat involves extraction of groundwater from an aquifer and treatment of the water above the ground. The extraction step is usually conducted by pumping groundwater from a well or trench. The treatment step can involve a variety of technologies such as adsorption, air stripping, bioremediation, chemical treatment, filtration, ion exchange, metal precipitation, and membrane filtration.

Soil vapor extraction (SVE) is used to remediate unsaturated (vadose) zone soil. A vacuum is applied to the soil in order to induce a controlled flow of air and remove volatile and some semivolatile organic contaminants from the soil. SVE usually is performed in situ; however, in some cases, it can be used as an ex situ technology.

For Soil washing, contaminants sorbed onto fine soil particles are separated from bulk soil in a water-based system based on particle size. The wash water may be augmented with a basic leaching agent, surfactant, or chelating agent or by adjustment of pH to help remove contaminants. Soils and wash water are mixed ex situ in a tank or other treatment unit. The wash water and various soil fractions are usually separated by means of gravity settling.

Solidification/stabilization (S/S) reduces the mobility of hazardous substances and contaminants in the environment through both physical and chemical means. The S/S process physically binds or encloses contaminants within a stabilized mass. S/S can be performed both ex situ and in situ. Ex situ S/S requires excavation of the material to be treated, and the treated material must be disposed of. In situ S/S involves use of auger or caisson systems and injector head systems to add binders to contaminated soil or waste without excavation, and the treated material is left in place.

Solvent extraction involves use of an organic solvent as an extractant to separate contaminants from soil. The organic solvent is mixed with contaminated soil in an extraction unit. The extracted solution is then passed through a separator, where the contaminants and extractant are separated from the soil.

For Thermal desorption, wastes are heated so that organic contaminants and water volatilize. Typically a carrier gas or vacuum system transports the volatilized organics and water to a gas treatment system, usually a thermal oxidation or recovery system. Based on the operating temperature of the desorber, thermal desorption processes can be categorized in two groups: high-temperature thermal desorption (320 to 560°C or 600 to 1,000°F) and low-temperature thermal desorption (90 to 320°C or 200 to 600°F). Thermal desorption is an ex situ treatment process. In situ thermal treatment is discussed below.

In situ thermal treatment is an in situ treatment process that uses heat to facilitate contaminant extraction through volatilization and other mechanisms or to destroy contaminants in situ. Volatilized contaminants are typically removed from the vadose zone using SVE. Specific types of in situ thermal treatment include conductive heating, electrical resistive heating, radio frequency heating, hot air injection, hot water injection, and steam-enhanced extraction. In situ thermal treatment is usually applied to a contaminated source area but may also be applied to a groundwater plume.

Vitrification involves use of an electric current to melt contaminated soil at elevated temperatures (1,600 to 2,000°C or 2,900 to 3,650°F). Upon cooling, the vitrification product is a chemically stable, leach-resistant, glass and crystalline material similar to obsidian or basalt rock. The high-temperature component of the process destroys or removes organic materials. Radionuclides and heavy metals are retained within the vitrified product. Vitrification may be conducted in situ or ex situ.