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1.1 EMERGENCE OF GEOENVIRONMENTAL ENGINEERING
Traditionally, geotechnical engineers have been responsible for (1) investigating subsurface conditions; (2) designing foundations for roads, buildings, machines, storage tanks, and offshore structures; (3) designing earthworks for dams, levees, roads, tunnels, and underground structures; and (4) investigating landmass problems such as landslides, slope stability, and subsidence (Taylor, 1948; Terzaghi and Peck, 1948; Lambe and Whitman, 1969; Peck et al., 1974). Geotechnical engineering was initially a loosely structured practice relying primarily on a few rules of thumb. After the 1950s, the practice of soil mechanics and foundation engineering grew tremendously throughout the world. The main contributors to this growth were Coulomb, Rankine, Darcy, Terzaghi, Casagrande, Taylor, Skempton, Bishop, and Peck. Through the work of these investigators, the practice of soil mechanics and foundation engineering became more rigorous, based on rational design approaches. As development of soil mechanics and foundation engineering continued, the practice of rock mechanics and engineering geology also evolved. Because all these topics proved interrelated, they were combined and renamed geotechnicalengineering in the early 1980s. Since then, geotechnical engineering has developed into an important and necessary specialty of the civil engineering profession.
Simultaneous with the growth of geotechnical engineering, the post-World War II economic boom of the 1950s led to rapid industrialization. In particular, chemical industries grew in number and increased the standard of living by producing a wide variety of products. Manufacture of these products required the production of tremendous amounts of organic chemicals while increasing the use of heavy metals. Mass production of these products also increased the quantity of wastes to be disposed of. Improper disposal practices and accidental spills of these chemicals have created numerous contaminated sites in the United States and throughout the world.
The onset of nuclear power plants and nuclear waste generated awareness of contamination problems and perhaps initiated the involvement of geotechnical engineers in environmental matters (Daniel, 1993). According to the National Environmental Policy Act of 1970, environmental impact assessments were required for any federal project that could affect the environment, particularly those involving the selection of nuclear power plant sites. Geotechnical engineers lead the detailed site investigations for these impact assessments. Another concern was the ultimate disposal of high-level radioactive waste, which can remain lethal for thousands of years. Geotechnical engineers played an important role in the investigation and characterization of suitable host soil and rocks for waste repositories. Geotechnical engineers also determined long-term performance of earth materials under realistic temperature and pressure, probable groundwater impacts, and potential risks. With increased attention, environmental concerns became a new aspect of geotechnical engineering.
One specific environmental event that increased attention was the widely publicized contamination at Love Canal in upstate New York. At this site, chemical wastes were buried in an old canal and covered with clayey soils. The chemicals seeped out slowly, contaminating the soil and groundwater. The health of the residents was adversely affected and the entire area had to be evacuated. This incident drew national attention to the effects of improper disposal and management of chemical waste. As a result, in the late 1970s and early 1980s, discussions began on the prevention and mitigation of such improper waste disposal practices. Also, as a result of this incident, new U.S. regulations for remediation of contaminated sites, in addition to the design of effective waste containment systems for newly created wastes, were promulgated. In 1970, the Resource Conservation and Recovery Act (RCRA) and its subsequent amendments addressed issues of disposal of newly generated waste. In 1980, the U.S. Congress passed the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), also known as the Superfund, to clean up contaminated sites in cases where the responsible polluting parties could not be identified or were incapable of paying for the cleanup. The geotechnical engineer's knowledge of earth material and groundwater became vital to the investigation, design, and actual cleanup of contaminated sites as well as the design of containment facilities.
Waste containment and remediation problems require an understanding of the physical characteristics of the subsurface and the ability to engineer it using the skills of classical geotechnical engineering. However, these problems also require an understanding of the chemical characteristics of the subsurface and the ability to engineer pollution control or removal using the skills of environmental engineering. A combined expertise of geotechnical engineering and environmental engineering is needed to address various aspects of such problems. In addition, knowledge of environmental regulations, hydrogeology, environmental chemistry, geochemistry, and microbiology is needed. Recognizing this fact, a new specialty of civil engineering known as geoenvironmental engineering (also known as environmental geotechnology and environmental geotechnics) emerged in the early 1990s. Geoenvironmental engineering encompasses the behavior of soils, rocks, and groundwater when they interact with contaminants and addresses problems of hazardous and nonhazardous waste management and contaminated sites.
Geoenvironmental engineering is evolving rapidly. Environmental laws and regulations that have a significant impact on geoenvironmental engineering are constantly changing. Environmental problems are numerous in all industrial and developing countries and will continue to grow with increased chemical waste generation and handling. For these reasons, geoenvironmental engineers will play a vital role in pollution control strategies, particularly in the design of effective and economical waste containment and remediation systems.
1.2 TYPES OF GEOENVIRONMENTAL PROBLEMS
Geoenvironmental problems may be grouped into three categories:
1. Contaminated site remediation: remediation of already contaminated soils and groundwater using in-situ barriers and in-situ or ex-situ treatment methods
2. Waste containment: safe disposal of newly generated wastes in engineered impoundments and landfills
3. Waste minimization by recycling: minimization of waste generation and disposal by recycling and using waste materials in various civil engineering applications, and beneficial use of closed waste disposal sites
A general overview of these problems with examples is provided in this section.
1.2.1 Contaminated Site Remediation
Until the early 1970s, environmental laws and regulations did not exist; therefore, chemicals were used and wastes were disposed of without proper consideration of potential impacts on public health and the environment. As a result, numerous sites have been contaminated by toxic chemicals. The U.S. Environmental Protection Agency (USEPA) estimated in 1997 that over 200,000 contaminated sites, where toxic chemicals pose unacceptable risk to public health and the environment exist in the United States.
The Wide Beach development site in Brant, New York, a 55-acre lakeside community development, is an example of contamination resulting from improper use of chemicals (USEPA, 1998b). From 1964 until 1978, waste oil containing polychlorinated biphenyls (PCBs) was applied to roadways in the community to control dust. In 1980, during the installation of a 1-mile sanitary sewer trench, soil from the roadways was excavated and used as fill in several residential yards. An odor complaint in the community led the regulators to discover drums containing waste oil with PCBs. Further investigation revealed that PCBs were present in soils from roadways and residential yards, in vacuum cleaner dust from residential homes, and in water from residential wells. An extensive remedial action, including the removal of drums and treatment of contaminated soils, cost more than $15 million.
The highly publicized Love Canal site, located in Love Canal near Niagara Falls in New York, demonstrated the consequences of improper disposal of wastes (usepa.gov). Between 1942 and 1953, over 20,000 tons of chemical waste was disposed of in an abandoned canal by a chemical manufacturing company. In 1953, the Niagara school board bought the property, despite a warning regarding the chemical waste present. A school was built and opened in 1955, with some buildings atop the waste-filled canal. By 1972, several homes with basements were built surrounding the school. In 1976, heavy rainfall in the area caused groundwater to rise. This rise caused subsidence of the waste-fill area, resulting in contamination of surface water. In addition, seepage of groundwater transported toxic chemicals into the basements of the surrounding homes. When children in the area fell sick in 1977 and 1978, the contamination was discovered. The Love Canal site was then evacuated and a state of emergency was declared. This incident drew national attention, initiating many environmental laws and regulations. Extensive remedial action at this site has been undertaken, at a total cost exceeding $200 million.
In addition to site contamination resulting from improper chemical use or waste disposal practices, spillage of toxic chemicals during handling, transportation, and storage have polluted soils and groundwater. Leaking underground storage tanks that contain petroleum products and other toxic chemicals are common occurrences. In 1995, the USEPA estimated that there are over 400,000 sites where soils and groundwater have been contaminated by leaking underground storage tanks. An example of such sites is the Fairfield Semiconductor Corporation site in San Jose, California, which operated from 1977 until its closure in 1983 (USEPA, 1998c). In 1981, an underground storage tank containing organic solvents failed, resulting in both soil and groundwater contamination by a mixture of solvents. An estimated 60,000 gal of waste solvents was released. Extensive remedial action was necessary, including removal of tanks, installation of slurry walls around the site perimeter to contain contaminated groundwater, extraction of contaminated groundwater, and treatment of contaminated soils. The remedial cost was over $4 million.
The role of geoenvironmental engineers in the remediation of contaminated sites, especially in dealing with contaminated soil and groundwater, is critical. Knowledge of soil composition, soil stratigraphy, groundwater hydraulics, and geochemistry can be applied to assess, develop, and implement effective remedial methods. In particular, geoenvironmental engineers have the capacity to lead subsurface investigations for the design of in-situ remedial strategies.
1.2.2 Waste Containment
Wastes are created that require disposal despite the best waste management practices. Such wastes include household garbage, mine refuse, highly toxic industrial by-products, and nuclear wastes. Proper disposal of these wastes in engineered waste containment facilities is crucial to protect public health and the environment.
Containment facilities for liquid wastes are known as surface impoundments, or more commonly, lagoons and ponds. These impoundments have to be lined properly at the bottom to prevent infiltration into the subsurface of their chemical constituents. In the past, because regulations on such linings did not exist, linings were not provided, resulting in several contaminated sites. An example of such a site is the Anderson Development Company (ADC) site in Adrian, Michigan (USEPA, 1998a). The ADC occupied approximately 12.5 acres of land, surrounded by residential areas. Between 1970 and 1979, the site was used for the manufacture of 4,4-methyl-bis(2-chloroamile) (MBOCA), a hardening agent used in plastics manufacturing. Process wastewaters were discharged to an unlined 0.5-acre lagoon. Later, contamination was found in the soils surrounding the lagoon. Because of the potential health hazard, the lagoon was closed and the contaminated soil was treated. Approximately $2.7 million was spent for completion of this project.
Containment facilities for solid wastes are known as landfills. In the early 1970s, wastes were disposed of in open ditches or pits, or piled above the ground surface. With no lining at the bottom, such disposal practices led to several contaminated sites. For instance, at a southern Illinois coal mine, liquid waste impoundments from coal processing were created within massive surface piles of coarse tailings (Reddy and Schuh, 1994). Waste constituents from the piles and impoundments have infiltrated the subsurface, causing groundwater pollution. A community in close proximity to the site drew the groundwater for drinking purposes. Because of the public health concerns, control of contamination at the source and the cleanup of groundwater became necessary, and remedial action, which includes closing the piles and impoundments and implementing remedial action, is expected to cost over $1 million.
Several Army bases also reportedly contain numerous unlined pits where toxic chemical wastes have been dumped, and soil and groundwater contamination has occurred as a result. For instance, at McClellan Air Force Base (AFB) near Sacramento, California, fuel and solvents were disposed of in several pits from the early 1940s until the mid-1970s (USEPA, 1998a,c). Later, an impermeable cap was constructed over the pits to reduce rainwater infiltration and subsequent leaching of contaminants into the groundwater. However, contaminants seeped out of the pits, contaminating the soil as well as the groundwater more than 100 ft below the ground surface. Corrective action involving groundwater treatment and soil remediation cost exceeded $3.8 million.
Newly generated liquid and solid wastes are required to be disposed of in engineered impoundments and landfills. All these containment facilities require liner systems that perform as both hydraulic and chemical barriers. In addition, these facilities must be located where hydrogeologic conditions are favorable. Upon reaching their waste storage capacity, the containment facilities should be covered properly to isolate the waste and to prevent infiltration of precipitation. The mechanical stability of liner and cover systems should also be ensured.
Excerpted from Geoenvironmental Engineering by Hari D. Sharma Krishna R. Reddy Excerpted by permission.
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PART I: BASIC PRINCIPLES.
1.1 Emergence of Geoenvironmental Engineering.
1.2 Types of Geoenvironmental Problems.
1.3 Book Organization.
2. RELEVANT ENVIRONMENTAL LAWS AND REGULATIONS.
2.2 Development of Laws and Regulations.
2.3 Federal Environmental Laws and Regulations.
2.4 State and Local Laws and Regulations.
2.5 Impact of Regulations on Geoenvironmental Practice.
3. CHEMICAL BACKGROUND.
3.2 Toxic Chemicals.
3.3 Inorganic Chemistry Background.
3.4 Organic Chemistry Background.
3.5 Nuclear Chemistry Background.
3.6 Chemical Analysis Methods.
4. COMPOSITION OF SOILS.
4.2 Soil Formation.
4.3 Soil Composition.
4.4 Soil Fabric.
5. SOIL PROPERTIES.
5.2 Geotechnical Properties.
5.3 Chemical Properties.
6. GEOCHEMISTRY BACKGROUND.
6.2 Inorganic Geochemistry.
6.3 Organic Geochemistry.
7. GROUNDWATER FLOW.
7.2 Hydrologic Cycle and Groundwater.
7.3 Aquifer, Aquiclude, and Aquitard.
7.4 Hydraulic Head and Aquifer Properties.
7.5 Groundwater Flow in Aquifers.
7.6 One-Dimensional Steady Flow.
7.7 Flow Toward a Pumping Well.
7.8 Pumping and Slug Testing.
7.9 Two- and Three-Dimensional Groundwater Flow.
8. CONTAMINANT TRANSPORT AND FATE.
8.2 Transport Processes.
8.3 Chemical Mass Transfer Processes.
8.4 Biological Process (Biodegradation).
8.5 Contaminant Transport and Fate Modeling.
PART II: REMEDIATION TECHNOLOGIES.
9. SUBSURFACE CONTAMINATION: SOURCES, CONTAMINANTS, REGULATIONS, AND REMEDIAL APPROACH.
9.2 Sources of Contamination.
9.3 Types of Contaminants.
9.4 Relevant Regulations.
9.5 Other Considerations.
9.6 Remediation Approach.
10. CONTAMINATED SITE CHARACTERIZATION.
10.2 General Methodology.
10.3 Preliminary Site Assessment.
10.4 Exploratory Site Investigation.
10.5 Detailed Site Investigation.
10.6 Expedited or Accelerated Site Characterization.
11. RISK ASSESSMENT AND REMEDIAL STRATEGY.
11.2 Risk Assessment Procedures.
11.3 USEPA Procedure.
11.4 ASTM Procedure.
11.5 Other Risk Assessment Methods.
11.6 Remedial Strategy.
12. IN-SITU WASTE CONTAINMENT.
12.2 Vertical Barriers.
12.3 Bottom Barriers.
12.4 Surface Caps or Covers.
12.5 Groundwater Pumping Systems.
12.6 Subsurface Drains.
13. SOIL REMEDIATION TECHNOLOGIES.
13.2 Soil Vapor Extraction.
13.3 Soil Washing.
13.4 Stabilization and Solidification.
13.5 Electrokinetic Remediation.
13.6 Thermal Desorption.
13.10 Soil Fracturing.
14. GROUNDWATER REMEDIATION TECHNOLOGIES.
14.2 Pump and Treat.
14.3 In-Situ Flushing.
14.4 Permeable Reactive Barriers.
14.5 In-Situ Air Sparging.
14.6 Monitored Natural Attenuation.
PART III LANDFILLS AND SURFACE IMPOUNDMENTS.
15. SOURCES AND CHARACTERISTICS OF WASTES 605
15.2 Sources of Wastes.
15.3 Classification of Wastes.
15.4 Waste Characterization.
15.5 Environmental Concerns with Wastes.
15.6 Waste Management Strategies.
15.7 Engineered Waste Disposal Facilities.
16. LANDFILL REGULATIONS, SITING, AND CONFIGURATIONS 635
16.2 Federal Regulations.
16.3 State and Local Regulations.
16.4 Siting Methodology.
16.5 Site Permit Application.
16.6 Landfill Configurations.
17. WASTE CONTAINMENT LINER SYSTEMS.
17.2 Low-Permeability Soil Liners.
17.3 Geomembrane Liners.
17.5 Geosynthetic Clay Liners.
17.6 Geonets and Geocomposite Drains.
17.8 Interface Strengths among Various Liner Components.
17.9 Manufacturing and Construction Quality Assurance.
17.10 Estimation of Leakage through Liner Systems.
17.11 Performance of Liners in Waste Containment Systems.
18. LEACHATE COLLECTION AND REMOVAL SYSTEMS AND LINER DESIGN.
18.2 Design Criteria.
18.3 Leachate Generation and Management.
18.4 Containment System Liner Design.
19. FINAL COVER SYSTEMS.
19.2 Purpose and Design Criteria.
19.3 Regulatory Minimum Requirements.
19.4 Design Procedure.
20. GAS GENERATION AND MANAGEMENT.
20.2 Gas Generation Mechanisms.
20.3 Gas Characteristics.
20.4 Gas Production Rates.
20.5 Gas Migration.
20.6 Gas Collection Systems.
20.7 Gas Flaring and Energy Recovery.
21. GROUNDWATER MONITORING.
21.2 Regulatory Requirements.
21.3 Groundwater Monitoring Systems.
21.4 Detection Monitoring Program.
21.5 Assessment Monitoring Program.
21.6 Corrective Action Program.
22. SURFACE IMPOUNDMENTS.
22.2 Regulatory Setting.
22.3 Liner Systems.
22.4 Surface Impoundment Design.
22.5 Cover Design.
22.6 Closure and Postclosure Care.
PART IV: EMERGING TECHNOLOGIES.
23. BENEFICIAL USE OF WASTE MATERIALS: RECYCLING.
23.2 Types and Evaluation of Waste Materials.
23.3 Fly Ash.
23.4 Blast Furnace Slag.
23.5 Foundry Sand.
23.6 Papermill Sludge.
23.7 Municipal Sludge.
23.8 Incinerator Ash (Sewage Sludge Ash).
23.11 Scrap Tires.
23.12 Demolition Debris and Recycled Concrete.
23.13 Wood Wastes.
24. END USES OF CLOSED LANDFILLS.
24.2 Various End Uses of Closed Landfills.
24.3 Design Considerations.
24.4 Case Studies.
25. BIOREACTOR LANDFILLS.
25.2 Types and Advantages of Bioreactor Landfills.
25.3 Regulatory Issues.
25.4 Bioreactor Design.
25.5 Bioreactor Landfill Operations and Maintenance.
25.6 Case Studies.
25.7 Research Issues.
26. SUBAQUATIC SEDIMENT WASTE: IN-SITU CAPPING.
26.2 Relevant Terminology and Definitions.
26.3 Site Evaluation.
26.4 Cap Design.
26.5 Construction and Monitoring.
26.6 Regulatory and Economic Considerations.
26.7 Case Studies.