EPA /500/SW-677 JANUARY 1978 l .*». ------- An environmental protection publication (SW-677) in the solid waste management series. Mention of commercial products does not constitute endorsement by the U.S. Government. Editing and technical content of this report were the responsibilities of the Systems Management Division of the Office of Solid Waste. Single copies of this publication are available from Solid Waste Information, U.S. Environmental Protection Agency, Cincinnati, Ohio, 45268. ------- UPGRADING HAZARDOUS WASTE DISPOSAL SITES Remedial Approaches This report (SW-677) was written by Donald G. Farb U.S. ENVIRONMENTAL PROTECTION AGENCY 1978 ------- ------- TABLE OF CONTENTS Page EXECUTIVE SUMMARY 1 INTRODUCTION 3 CONTROL AND DECONTAMINATION TECHNOLOGY 5 Infiltration Controls 6 Cover Materials 6 Grading and Contouring 10 In Situ Grouting 11 Other Infiltration Barriers 17 Excavate and Bury at a New Site 17 Leachate Plume Management 21 Leachate and Contaminated Groundwater Treatment 29 Soil Manipulation 31 Soil Flushing 31 In Situ Chemical Detoxification 33 Microbial Innoculations 33 DECISION ANALYSIS 35 REFERENCES CITED 36 LIST OF TABLES 1. Cost for Various Sanitary Landfill Liner Materials 8 2. Infiltration Barrier Costs 16 LIST OF FIGURES 1. Cross Sectional View of Landfill with Layered Cover 9 2. Potential Drainage Pattern for Area Fill 12 3. Potential Drainage Pattern for Trench Fill 13 111 ------- LIST OF FIGURES (cant.) Page 4. Injected Soil Grout Curtain 15 5. Effective Hazardous Waste Management - Disposal Phase 19 6. Groundwater Pumping 22 7. Effect of Differing Coefficients of Transmissibility upon the Shape, Depth and Extent of the Cone of Depression 24 8. Cost of Gravel-Packed Wells Finished in Sand and Gravel 25 9. Cost of Shallow Sandstone, Limestone, or Dolomite Bedrock Vfells 26 10. Cost of Tubular Vfells Finished in Sand and Gravel 27 11. Monthly Cost of Vfells and Pumping Systems 28 12. Well Point Dewatering System 32 IV ------- EXECUTIVE SUMMARY Groundwater contamination problems, resulting from the indiscriminate disposal of potentially hazardous wastes, are seldom so uncomplicated that one site restoration technique will adequately serve to correct the contamination problem. Such contamination is typically the result of waste disposal practices which have led to an accumulation of solids, liquids, sludges, discarded containers, and miscellaneous debris. Therefore, more than one remedial procedure may be required to abate a groundwater contamination problem. Such procedures include: - infiltration controls cover materials grading and contouring in situ grouting - waste excavation and burial at a new site - leachate plume management by groundwater pumping - leachate and groundwater treatment - soil manipulation soil flushing ^in situ chemical detoxification microbial innoculations Of the above techniques, excavation represents the most reliable abatement procedure, but also potentially the most expensive and most objectionable from a citizen acceptance point of view. Groundwater pumping techniques may provide acceptable near-term control, however, such techniques do not address the real problem, eliminating the source of contamination. Without effecting some control on the source of contamination, groundwater pumping and treatment may be required for an indefinite period. Infiltration control techniques, especially grouting and special cover materials, represent potential means of achieving adequate control with minimum citizen opposition and at a reasonable cost. However, such approaches are currently viewed as high-risk technologies due to the absence of case histories which adequately demonstrate their technological and economical feasibility. Finally, the pollution abatement potential of soil manipulation ------- techniques has been successfully demonstrated. However, the applica- bility of these techniques is limited to specific contaminants that are susceptible to the soil manipulation approach, such as chemical spills. The final decision on which restoration approach(es) should be used should be based on an analysis on the following: - type of contaminant and its characteristics - levels of contamination - areal extent of contamination - quantity of contaminant at the source - technical feasibility of potential restoration methods - economic feasibility of potential restoration methods - institutional and political constraints, such as public opposition - tangible and intangible costs of taking no action and thus abandoning the resource The science of cost/benefit analysis of groundwater resources is in its infancy, especially the art of predicting intangible costs. Since economics and social/institutional issues are expected to play a major role in the decision process, it is important that the development of cost analysis techniques be adequate for its role in the decision process. ------- INTRDDUCTIOSI An increasing number of groundwater contamination incidents, resulting from the indiscriminate land disposal of potentially hazardous wastes, is being brought to the attention of the U.S. Environmental Protection Agency. Such incidents are typically revealed only after some public health or property damage has occurred. The number of incidents identified to date is considered to be only the "tip of the iceberg," and many incidents remain to be identified.^ Further support of this observation is found in the Report to Congress on Waste Disposal Practices and their Effects on Groundwater* which concluded that: Waste disposal practices have contaminated groundwater on a local basis in all parts of the nation and on a regional basis in a few heavily populated and industrialized areas. For every waste disposal facility documented as a source of groundwater contamination, there are thousands more which are sited, designed, and operated in a similar manner. Many of these potential sources are receiving hazardous wastes. Knowledge is especially lacking with regard to locations of potential sources of ground- water contamination and the severity of documented cases. Monitoring of potential sources of groundwater contamination is almost nonexistent.2 These findings suggest that an unknown number of disposal sites are currently contaminating, or will in the future contaminate, ground- water resources and drinking water supplies. The origin of toxic chemical contamination of groundwater resources may be a municipal landfill, a chemical spill, an exposed chemical stockpile, or the direct discharge of a hazardous residual to land by lagooning, land spreading, landfilling, and open dumping. Regardless of the origin, the events leading to the contamination of the ground- water resources are the same; free liquids, usually water, leach readily available waste constituents vertically through the unsaturated profile *0ffice of Solid Waste Management Programs and Office of Water Supply. Washington, U.S. Environmental Protection Agency/ 1976. ------- to the zone of saturation. Movement in the water saturated zone is horizontal with the rate of flow determined by the gradient of the aquifer and its permeability. Although it has been assumed that contaminants migrate laterally near the water table, recent research indicates that the contaminants mav disperse at several levels in the aquifer and migrate at levels. ' Restoration procedures are defined as techniques employed to restore the quality of the groundwater resource by isolating the waste material from leaching liquids or by collecting and treating leachate containing potentially hazardous constituents. The following will examine several remedial procedures to correct contaminating disposal sites. ------- CONTROL AND DECONTAMINATION TECHNOLOGY The traditional public health approach to disease control, breaking the vector-pathway-host transmission cycle, has a parallel in the control of a contaminating waste disposal site. In the case of a contaminating disposal site, the vector or carrier is principally water, the pathway is a groundwater resource, and people or other groundwater users (plants and animals) are the hosts. The agent in this case is not a biological agent, but rather a toxic chemical leached from the waste. The vector, water, originates from a number of sources, including: precipitation . groundwater intrusion . moisture from the waste material direct disposal of liquid wastes decomposition of organic material Once contaminated by leachates, the quality of the water supply may be considered polluted if the contaminant(s) imparts odors, tastes, or other physical or chemical characteristics that exceed a permissible level as defined by drinking water standards, industrial processing water requirements, or the requirements of other water users. Remedial measures, the set of pollution control measures taken to mitigate the contamination problem, are typically applied only after public health or property damage has been detected. In the traditional public health case, control measures are applied at the weakest point in the disease transmission cycle. Oftentimes, the weakest link is the disease vector. Eliminating the vector, water, in the case of a contaminating waste disposal site does not represent a vulnerable point of attack, since water is indigenous to the waste and soil, and is a byproduct of the decomposition process. For example, if buried refuse contains less than 60 percent moisture, it will be difficult for micro- organisms,-to perform the decomposition desired in a sanitary landfill. However, controlling the vector's pathway, that is, stopping infiltration into the disposal area and exfiltration from the disposal area to the water resource, and/or attenuating the toxicity of the chemical agent may be acceptable means of controlling the environmental and public health impact of contaminating disposal sites. Specific means of achieving these ends include: ------- . Infiltration controls liners and covers grading and contouring in situ grouting . Excavation, treatment and burial of the waste at a new site . Croundwater pumping and treatment Soil treatment contaminant flushing and treatment AD Hity detoxification rnicrobial innoculation The ensuing discussion will examine the technological and economic feasibility of each measure. Finally, decision analysis will consider the option of abandoning the contaminated water resource and providing an alternate water supply. Infiltration Controls Cover materials. Current practice calls for the control of infiltration by covering disposal areas with fine textured soils and compacting the cover to minimize the percolation rate. On-site soil is commonly used for cover material. This approach may lead to increased recharge by creating a source of artificial recharge: Even with compaction, top cover material may have a higher permeability than undisturbed soil. . A highly compacted subbase may lead to the buildup of a greater hydrostatic head in the deposition area; without relief, this head will contribute to the exfiltration process. The cumulative effect of these factors is increased groundwater recharge and a shallower zone of saturation, oftentimes raising the water table into waste deposition area. The artificial water table and exfiltration will continue to exist as long as the top cover allows infiltration. ------- Capning the site with an impermeable material may provide adequate infiltration control. Synthetic materials such as polyvinyl chloride (PVC) , polyethylene (PE) , coated polypropylene, and chlorinated poly- ethylene, such as Hypalon, have been recommended and proposed for capping existing landfills.0' 7 '8 However, actual field experience with such a capping material is very sparse. New Castle County, Delaware, has capped a ten-acre section of a county landfill with a coated polypropylene (approximately 20 mils) .9 The material, prepared in rolls 10 feet by 1000 feet, was installed by slowly unrolling it across the face of the landfill. Successive sheets were overlapped to provide a shingled effect; field splicing of adjacent sheets was not attempted. Cost of the liner material was less than $0.60 per square yard. Cost estimates for other liner materials are indicated in Table 1. The major question yet to be answered is whether or not the liner material will lose its physical integrity and break down before the refuse is sufficiently decomposed and the threat of leachate contami- nation has subsided. Controls such as liners favor the development of an anaerobic environment which also increases the waste decomposition time. Secondly, the integrity of the synthetic cap may be further threatened by subsidence, which occurs after cap emplacement. Such subsidence may tear the liner or break the bond that splices together adjacent sheets of liner material. If additional subsidence threatens the integrity of the liner, excavation and repair will be required to avoid ponding and infiltration. However, the potential for subsidence is much less in an older landfill. In humid regions, normal settlement of a sanitary landfill seems to be exponential with time, with most of the total settlement completed in three years. 1® Therefore, the use of a synthetic liner to control infiltrate at an abandoned landfill site may present less of a technological risk than at a recently completed landfill. The subject of liner integrity and splice integrity under landfill conditions is being examined by Haxo under contract to the EPA's Solid and Hazardous Waste Research Division (SHWRD) , Cincinnati, A layered cover consisting of a layer of natural materials with very low permeabilities, for example montmorillonite clay, followed by a layer of a highly permeable material, such as sand, and finally a layer of topsoil, has been proposed as a means of creating an infiltration barrier and diversion system (figure 1) .12 Effective diversion of precipitation ------- Table 1 COST FOR VARIOUS SANITARY LANDFILL LINER MATERIALS* Material Asphalt sprayed on polypropylene fabric (100 mils) Soil-bentonite (9.1 lbs/yd2) Soil-bentonite (18.1 lbs/yd2) Soil-cement with sealer coat (6 inches) Installed cost"1" ($/sq yd) Polyethylene (10 - 20* rnils§) Polyvinyl chloride )10 - 30* mils) Butyl rubber (31.3 - 62.5* mils) Hypalon (20 - 45* mils) Ethylene propylene diene monomer (31.3 - 62.5* mils) Chlorinated polyethylene (20 - 30* mils) Paving asphalt with sealer coat (2 inches) Paving asphalt with sealer coat (4 inches) Hot sprayed asphalt (1 gallon/yd2) 0.90 - 1.17 - 3.25 - 2.88 - 2.43 - 2.43 - 1.20 - 2.35 - 1.50 - 1.44 2.16 4.00 3.06 3.42 3.24 1.70 3.25 2.00 (includ earth cover) 1.26 - 1.87 0.72 1.17 1.25 * After: Haxo, H.E., Jr. Evaluation of liner materials. U.S. EPA Research Contract 68-03-0230. October 1973. + Cost does not include construction of subgrade nor the cost of earth cover. These can range from $0.10 to $0.50/yd2/ft of depth. * Material costs are the same for this range of thickness. 5 One mil = 0.001 inch. Source: Geswein, A.J. Liners for land disposal sites - an assessment. U.S. Environmental Protection Publication SW-137. Washington , U.S. Government Printing Office, 1975. 66 p. ------- FIGURE 1 CROSS SECTIONAL VIEW OF LANDFILL WITH LAYERED COVER ------- may be achieved by providing sufficient sloping to avoid the buildup of a hydrostatic head at the interface of the impermeable layer. Precipitation infiltrating the topsoil will be conducted vertically through the highly permeable layer and, upon encountering the less permeable layer, move laterally along the interface of the two layers, discharging at the toe of the landfill into a surface runoff water collection system. In addition to improving the drainage, the approach also increases the stability of the slope: If the slope under study is underlaid with a highly pervious gravel layer, the flow net consists of vertical flow lines and horizontal equipotentials. Under this seepage condition, the energy of the free water in the soil is consumed harmlessly as it flows vertically downward to the gravel, and thence outward to the toe of the slope. •* As a final observation, in humid regions it has been noted that leachate migration from a disposal site will still continue and contain a greater concentration of contaminants, if infiltration is reduced but not eliminated.-^ Therefore, it becomes important to completely stop infiltration, not simply reduce it, to eliminate exfiltration. Grading and Contouring. The most economical technique to decrease infiltration is to grade, contour and vegetate the landfill cover. Grading and contouring work costs will vary widely depending upon the nature of the material and task. The objective of reshaping and grading the site is to fill subsidence depressions and create runoff patterns with shorter slopes which discharge to lined (concrete, plastic or corrugated metal) swales and troughs. The relationship between rainfall and peak runoff may be represented by the rational formula: Q=CIA. Where Q is the peak discharge in cubic feet per second (cfs), C is the runoff coefficient, I is the rainfall intensity in inches per hour, and A is the drainage area in acres. The formula assumes that a maximum rate of runoff is produced when rainfall is maintained for a period of time equal to the time necessary to reach maximum flow. The time lag between the beginning of the rainfall and maximum runoff is defined as the time of concentration (tc). The potential for head buildup and infiltration may be reduced by decreasing t.,. In other words, increasing the \*> steepness of the slope and decreasing the slope length will reduce the time of concentration. 10 ------- An empirical formula for the time of concentration in hours is: fcc = °'00013 ITOS5' where L is the length of the basin area (feet) S is the average slope of the basin -.^ expressed as a dimensionless number Increasing the steepness of the slope will, however, increase the erosion potential. Therefore, slope erosivity becomes an upper limit for determining the optimum slope. The erosion potential may be calculated by several formulae. A modified Musgrave Equation has been extensively used by the Soil Conservation Service, Department of Agriculture:^6 „ 1.35 0.35 E = 0.91KCP -^ ~2Ti where, E is the sheet erosion in metric tons per year K is the soil erodability factor C is the cover factor R is the rainfall factor S is the percent slope L is the length of slope in meters Values for factors K, C, and R are available from the Soil Conservation Service. Potential surface configurations to facilitate runoff are illustrated in figures 2 and 3. The objective in each case is to shorten the length of slope, minimize erosion, maximize runoff and provide for the collection of runoff. In situ grouting. .In situ grouting is the process of injecting low viscosity binding/cementing agents into a porous medium, such as soil, to form an impervious barrier. Several grouting agents have been used to seal porous strata, including: cement, epoxy resins, liquid glass (silicate grouts), poly isocyanate, acrylic amide, chrome-lignin, and urea formaldehyde. The grouting concept has been used for a number of years by the mining and oil industries to seal off highly permeable strata. Pipeline companies have used grouting materials to effectively 11 ------- Plan View with Contours Lined Drainage Troughs ' Cross-Section along M' Figure 2 Potential Drainage Pattern for Area Fill 12 ------- Fi gure 3 Potential Drainage Pattern for Trench Fill Plan view with contours lined troughs Perimeter Collection ^ Network iross 13 ------- seal the walls of underground caverns used for liquified petroleum gas storage.17 Grouting has been recommended by the EPA as a means of sealing inactive and abandoned underground mines to eliminate mine drainage.18 Underground grouting has been proposed to stem the migration of leachates from radioactive waste burial sites.19 In recent years methods have been developed to seal saturated zones (below the water table) without impairing the grout's curing process. It has been found that grouting materials are stable over extended periods of time and behave similar to concrete, becoming harder and more stable with age, and are resistant to acids at pH 4.19i20 Companies with long standing experience in underground grouting report that grouts may be injected (under pressure) to depths in excess of 30 meters and seal strata 10 to 12 meters thick.2^'^^Grouting agent viscosities range from 1.5 to 300 centipoises. Short set time formu- lations will achieve 85% of the desired strength in 30 minutes; total strength is reached in 24 hours. Gel times or set times may be shortened to achieve stoppage of flowing water, or gel times may be extended up to six hours to permit maximum induction (flow into the interstices of the porous strata). Due to their transmissivity properties, unconsolidated strata consisting of fine textured materials, clays and silts, are not as effectively grouted as coarse textured strata, such as sand. Soil textures equal to or larger than a 200 mesh screen usually have excellent grouting properties. With finer textured soils, injection points must be closer together to achieve an effective seal. Impervious grout curtains may be constructed around the perimeter of a specific area, such as a contaminating disposal site, to retard the flow of groundwater through the area (figure 4). In this instance, injection points are drilled through the unsaturated overburden and into the water-bearing strata. Grouting materials are injected into the saturated strata as the injection system is withdrawn. Spacing of successive injection points would be determined by the viscosity of the grouting material and the permeability of the strata. Such an approach may be entirely feasible for contaminating disposal sites located in abandoned sand and gravel pits. However, the absence of actual case histories precludes an adequate assessment of this technique. Field work needs to be conducted to evaluate in situ grouting"s potential to seal the bottom as well as the sides of a contaminating disposal site. 14 ------- Figure 4 Injected Soil Grout Curtain HOLES IMPERVIOUS (SROl/T CURTAIN Source: Wantland, Lloyd T., Halliburton Services, Pittsburgh, Pa. 15 ------- TABLE 2 Infiltration Barrier Costs Total Slurry Trench $6/sq ft $370,000 Imper-Wall $4/sg ft $240,000 Grouting $15/sq ft $900,000 Concrete Wall $6.75/sq ft $400,000 Source: Atwell, J.S. Identifying and correcting groundwater contamination at a disposal site. Presented at the Fourth National Congress on Waste Management Technology, Atlanta, November 1975. 32 p. 16 ------- Material costs for grouting materials are indicated in Table 2. Other infiltration barriers. In situations where the water table exists at or near the surface, slurry trenches, emplaced steel plates, an Imper-wal]^'technique may provide an adequate barrier. A slurry trench involves excavating a narrow trench and replacing the excavated material with a bentonite slurry. Excavated soil is subsequently added as a cap on the trench. The use of steel plates involves the driving of successive and overlapping steel plates to the desired depth; thus creating a curtain to the lateral flow of water. Imper-wall is the trade name for a technique which involves driving an I-beam to a desired depth and grouting the void space created during extraction of the beam. The beam has a steel pipe attached to its full length. As the beam is extracted, a cementitious sealing material is continuously injected through the pipe. A continuous barrier is created by overlapping successive injection points. Excavate and Bury at a New Site The concept of excavation and burial involves the complete removal of the source of contamination and transport to a new location for final disposal. The approach is applicable to chemical spill sites as well as landfills. Treatment of a liquid effluent and possibly contaminated groundwater resources may also be required as part of the problem's solution. (Techniques for treating effluent and groundwater resources will be discussed later on.) The decision to employ an excavation and burial method of site restoration may not be based as much on the state-of-the-art as on the: . economic feasibility of an alternative restoration technique . availability of a suitable disposal site (landfill, incinerator, etc.) for excavated material size of the excavation problem . public acceptance of the excavation process. Other constraints, related to the cleanup of spilled material, as identified by Lindsey, include: . availability of transportation availability of cleanup funds 17 ------- suitability of temporary storage facilities citizen concern . local, State, Federal regulations covering the transportation and disposal of spill materials.22 If these considerations do not represent overriding technical and economic constraints, the approach may be the most reliable method of eliminating a source of groundwater contamination. Open pit and strip mining techniques may be suitable for excavation purposes. Excavated material must be transported by methods consistent with existing State and Federal regulations governing the shipment of hazardous wastes. The Department of Transportation has proposed rules which state that the transportation of hazardous material shall be conspicuously labeled. •* The burial of excavated hazardous residuals will require specific attention to the location and design of the disposal site. Recommen- dations for the engineered disposal of hazardous residuals may be found in Landfill Disposal of Hazardous Wastes, Land Disposal, Technology for Industrial Wastes, and work by Barr. '6'25These recommendations include (figure 5): waste pretreatment, where feasible disposal site infiltration and exfiltration barriers leachate collection and treatment systems saturated and unsaturated zone monitoring site registration and controlled access . episode or contingency and maintenance plans. Although not explicitly written for the purpose of disposing of residuals excavated from contaminating disposal sites, their recommendations are nonetheless applicable to such wastes. If the contamination consists of a small spill, and it is not practical to dedicate a plot of land as an engineered disposal site, it may be feasible to ship the spill cleanup materials to a licensed hazardous waste management facility. Information on such facilities may be obtained from EPA Office of Solid Waste Management Programs, Hazardous Waste Management Division publications or from State solid waste management officials. Disposal costs at such facilities range from $1.00 to $30.00 per drum depending upon the nature of the waste.2^ Decisions to use such facilities should be made only after consulting with the proper facility licensing authority. 18 ------- LLJ U) U) h- CO in co < H I 5 « co -J B § S S§ S < tu UJ g CO 19 ------- In a 1970 case history involving 1.5 million cubic yards of -9 buried refuse, excavation, hauling, and burial costs were as follows: excavating and loading $0.50 per yd hauling 1.95 landfilling at new site .50 -, ^ Total (1970 dollars) $2.95 per yd (one yd of compacted refuse is equal to approximately 800 Ibs.) In a second site restoration case, projected excavation and burial costs have been estimated to be: $6.75 per ton for removal and disposal at a site 10 miles from the existing landfill (figure includes $1.25 per ton for effluent and leachate controls) . $12.00 to $16.00 per ton to remove and incinerate waste (range due to variations in incinerator design), includes credit for sale of recovered energy at a rate of $4.00 per ton of refuse.* 30 A study conducted by the U.S. Army Materiel Command of a contaminated site where potentially hazardous materials were disposed of over a large area for many years, determined that complete excavation and restoration of contaminated soil is technically and economically infeasible. In this situation, in situ soil treatment techniques may offer the greatest potential for proper restoration. Efforts of Virginia officials to move Kepone, a pesticide, contaminated waste and debris to another geographic area for disposal met with stiff opposition from concerned citizens and public officials. As a result, a specially designed landfill was constructed for part of the waste near the contaminated site. The site, with a capacity of approximately 7300 cubic yards was lined with 30 mil reinforced PVC * The value of recovered energy is tied to the current value of competing energy sources, coal, oil, and gas. As the cost of other energy sources increases, the value of energy recovered from refuse also increases. 20 ------- liner (approxinrt ly 200 feet by 150 feet) and capped with 15 mil non-reinforeed PVC. Cost of the bottom liner was estimated to be approximately $10,000 (approximately $3.00 per yard). Site design also included a network of perforated corrugated PVC pipes (4") under the bottom liner to facilitate the detection of liner failure and leachate movement. Clean fill was placed on the bottom liner to protect it from rupture during the filling operation. The emplaced wastes were covered with a 4-foot layer of soil to protect the PVC cap. Finally, the PVC cap was covered by 4 feet of soil, graded, and seeded. Location of the site and its contents have been registered with local officials. The cost of additional cleanup work involving the removal, treatment (incineration) and replacement of soil (1000 foot radius at a depth of one inch) around the Kepone contamination site has been estimated to be $1.5 million.32 In the final analysis, the decision to excavate and ship the source of contamination to a new site may be largely determined by the economics and by citizen acceptance of the proposed cleanup plan. Leachate Plume Management When moisture from infiltration and other sources saturates the soil and refuse beyond field capacity, accumulated liquids will flow under the influence of gravity and hydrostatic pressure in the path of least resistance. Exfiltrate or leachate is the solution of leached waste constituents that migrates from the disposal site. The gradual escape (exfiltration) of leachate may occur as surface seepage at the toe of the disposal site, if the subcase of the burial site is highly impermeable. Or, leachate may move vertically through the unsaturated profile and enter the groundwater regime. Surface seepage of leachates may be handled by installing lined collection ditches and basins at the discharae points and treating the collected effluent. Treatment methods for leachate will be discussed later in this section. Exfiltration of leachate into water table aquifers represents a more difficult restoration problem. In this situation, continuous groundwater pumping may be required until the source of contamination is controlled and groundwater quality restored (figure 6). Factors that affect such groundwater cleanup efforts include: 1. Aquifer permeability (the quantity of water that will flow through a cross sectional area in unit time under a hydraulic gradient of unity). - A well in an aquifer with-a low 21 ------- Figure 6 Groundwater Pumping CO 22 ------- 1. Aquifer permeability (the quantity of water that will flow through a cross sectional area in unit time under a hydraulic gradient of unity). - A well in an aquifer with a low permeability will have a cone of depression with a smaller radius of influence than a similar well in a more permeable aquifer (figure 7). Therefore, control of leachate movement in aquifers of low permeability will require more wells and closer spacing to achieve the desired overlapping cones of depression. 2. Type of contaminant - Contaminants that tend to migrate at or near the bottom of the aquifer will require higher Pumping rates and deeper wells than contaminants that tend to migrate near the water table. 3. Attenuative capabilities of the saturated and unsaturated profiles - Sorption properties of the saturated and unsaturated strata as well as the dispersion potential (i.e., how rapidly leachates are diluted by groundwater flow) will, first of all, determine if and when down gradient water supplies will become contaminated. Secondly, attenuative properties will partially dictate where wells should be installed in order to achieve optimum plume control at minimum costs. For example, arsenic ions and chlorinated hydrocarbons tend to be held by soil particles, whereas chloride and fluoride ions readily migrate. 4. Source of contamination - Without affecting some control on the source of contamination, leachates will continue to be a problem. The source of contamination may be controlled by excavating the waste material and disposing of it in a non- leaching environment, or capping the disposal area, thereby creating a non-leaching environment on-site. (The afore- mentioned approaches were discussed in detail earlier.) Groundwater pumping has been applied as a control technique in several cases because it has been found to be the most economical procedure. Representative well and pump costs for Illinois wells (1964-1966), as reported by Gibb and Sanderson and Gibb, are presented in figures 8 - 11.33,34 Without controls to limit further infiltration, leaching and groundwater contamination will continue until the source of contamination is depleted, and dispersion re-establishes groundwater quality. With infiltration controls or excavation of the waste, groundwater quality should tend toward recovery as pumping continues. It is feasible to estimate the recovery period for a contaminated aquifer. The estimate requires knowledge of the infiltration rate, 23 ------- Figure 7 a TJ 10- 20- (A) hRodius- 18,000 ft- Transmissibility • 10,000 gpd/ft Radius • 40,000 ft • s-2.5ft- Transmissibility - 100,000 gpd/ft 20- EFFECT OF DIFFERING COEFFICIENTS OF TRANSMISSIBILITY UPON THE SHAPE, DEPTH AND EXTENT OF THE CONE OF DEPRESSION, PUMPING RATE AND OTHER FACTORS BEING THE SAME IN BOTH CASES. t the coefficient of transmissibility (T) is a measure of permeability (T = permeability X aquifer thickness) Source: Ulric, G.P., and R.P. Singer. Water well manual. Berkeley, Premier Press, 1973"156 p. 24 ------- Figure 8 ICO 80 6C "i r ~~i r ", • i" i '../"•Fit COST ES'lllATt Ass-jr, _-t 1C". Vt I i % --h =- I 10 fVit Des r> . > • t ' d - 20C gc". Wc'l j. j-Ktcr - 8 ic!-t:<; ' nblc I) Gra-f i ,Mck j-inulbs = (• '-,c •.-•. -.hick Bore },")! ; d'aTieter = 20 inc c^ 30' CO::FISS-.CE LIMITS 6rJ 80 100 700 DEPTH CF W'LL fJ) lil FEET 1000 Soxorce: Gibb, J.P., and E.W. Sanderson. Cost of municipal and industrial wells in Illinois, 1964 - 1966. Urbana, Illinois State Water Survey, Circular 98, 1969. 22 p. 25 ------- Figure 9 30 20 10 8.0 6.0 4.0 -7 3.0 £ 2-0 1 1 1 1 1 SAMPLE COS1 ESTIMATE Assumpt ions : _ Dolomi tc Wei 1 Well depth - 290 feet Desired yield - 500 gpm Well diameter •= 10 inches Estimated We) 1 Cost: Expected range $3300 - SA3 - "Best fit" $3700 W u .c. .c. J.C • 0 - .- 57 .7 0. 8d 81 83 . dl.li7l , / y" ' ' *••*=% / ^ t / / / / _ / / / n '-*-/ /*/ / (table 1) 00 I/X A// / /Zl //' /// / A/< ' 't// 7/° * // J S f ' / / °/y \7/° r« V / — BO DIA '/ / o \ / ,/* ' |/ TTO^ METE 1 / f o / BC RS 5-2 8 , RE IN k -12 HC U LE Ch — BEST FIT LIKE — BOS CONFIDENCE ES LIMITS 0.8 0.6 0.4 0.3 1)0 60 80 100 200 '.00 600 800 1000 2000 DEPTH OF WELL (d) III FEET Coat of ohallou uandntane, limeatona, or dolomite bedfoak ualle Source: Gibb, J.P., and E.W. Sanderson. Cost of municipal and industrial wells in Illinois, 1964 - 1966. Urbana, Illinois State Water Survey, Circular 98, 1969. 22 p. 26 ------- Figure 10 100 80 60 1)0 20 10 8 6 I> 2 As sum We Oe We Es t im Ex "B V.C.* l 1 1 i 1 { SAMPLE COST ES"IM^TE }t ions : 1 depth = 90 fe.jt > i red yield = 50 gpn I diameter =» 6 'riches i Jted Well Cost: >ected range $23:0 - $32 •st fit" S30SO J.C.- ^-» • 8oOdC 850d \J % *f .299 D.37 ^ ~" "< 3 _ " ^ ^ f • & ?3 „- f- 9. l~ table I) 00 - .. • ^ BOTTO ~DIAMET 1 OORE :RS IN s i^.tc ."I*- ..." ^^ .[^ &£^ " — - — — ( HOL INC 6-10 EST f Oi, CO T LI JFIOE NE HCE LI •III S 20 1)0 60 80 100 200 DEPTH OF WELL (d) IN FEET WO 600 1000 Coat of tubular i-'elle finished in sand and gravel Source: Gibb, J.P., and E.W. Sanderson. Cost of municipal and industrial wells in Illinois, 1964 - 1966. Urbana, Illinois State Water Survey, Circular 98, 1969. 22 p. 27 ------- Figure 11 Monthly cost of wells and pimping systems EQUIVALENT MONTHLY COST OF WELL ANO PUMPING SYSTEM IN DOLLARS s Source: Gihb, J.P. Cost of domestic wells and water treatment in Illinois. Groundwater, 9(5):40-49, Sept. - Oct. 1971. 28 ------- measurements of groundwater levels, permeability, runoff, and evaporation.15 in addition, an unknown contamination potential may remain in the landfill or disposal area, and will continue to contribute leachate migration if a hydrostatic head remains in the disposal area. Leachate and Contaminated Groundwater Treatment Leachate treatment or groundwater treatment involves upgrading the quality of the exfiltrate to a point where it may be discharged without further damage to the environment. Recycling leachate back to the disposal site by well-point injection or spray irrigation does not constitute a recommendable treatment approach. Major weaknesses with this approach include: Many hazardous constituents of industrial waste leachates (e.g., heavy metals) do not degrade and will remain in solution unless steps are taken to precipitate them out . The acidic properties of such leachate will accelerate the release of additional hazardous constituents . Without exfiltration controls, recycled leachate will contribute to the hydrostatic head in the disposal area and provide a continuing threat to the quality of underlying water resources. Due to the high inorganic chemical and stable organic chemical nature of industrial waste leachate, tertiary wastewater treatment and water purification techniques are proving to be successful leachate treatment techniques. Studies conducted by the Army Materiel Command indicate that reverse osmosis and carbon coagulation are the most feasible means of removing pesticide and nerve agent by-products from contaminated groundwater.31 Liskowitz _et al., studied the leachate treatment potential of several readily available sorbent materials (activated alumina, activated carbon, fly ash, bottom ash, illite, kaolinite, zeolite, Cullite, and vermiculite).35 Leachates from calcium fluoride sludge, metal finishing sludge, and petroleum sludge are passed through columns of sorbent materials to determine the attenuative characteristics of each sorbent. Although no single sorbent material was found to be completely effective in removing all toxic ions from the leachates, two or three different sorbent materials could be combined to reduce leachate constituents to acceptable levels. Activated alumina, illite, and activated carbon proved to have the most versatile sorbent properties. Work is continuing in an effort to develop a leachate/ sorbent matrix for a greater number of industrial wastes. 29 ------- be completely effective in removing all toxic ions from the leachates, two or three different sorbent materials could be combined to reduce leachate constituents to acceptable levels. Activated alumina, illite, and activated carbon proved to have the most versatile sorbent properties. Work is continuing in an effort to develop a leachate/ sorbent matrix for a greater number of industrial wastes. Packaged physical-chemical waste water treatment units are now available for treating sanitary landfill leachate. Such leachate treatment systems include the following features: - equalization - aeration - chemical addition with flash mixing - controlled flocculation - clarification by sedimentation - dissolved organic removal by carbon adsorption - pressure filtration with programmed backflushing - breakpoint chlorination - pH adjustment.^^ Models with throughput capacities up to 300,000 gallons per day (gpd) are available. Operating costs for a 100,000 gpd unit are approximately ?0.20 per 1000 gallons. Leachate treatment units have been installed at landfills in New Jersey and Pennsylvania, and a pharmaceutical manufacturing plant in Indiana. ' Such units have shown better performance characteristics if additional aeration is provided prior to the treatment routine. High ammonia (NH^) levels also tend to reduce the treatment efficiencies of such units. Jorgensen found that clinoptilolite, a silicate material similar to zeolite, had good ion exchange potential for removing NH^ from wastewater with high concentrations of competitive calcium and sodium ions. ° Extended aeration and steam stripping may also facilitate the removal of NH^. Sludges and other residuals generated from the treatment of leachate should receive treatment and disposal by methods which assure that their toxic constituents will not resolubilize and constitute an environmental threat. If the potential for resolu- bilization exists, ultimate land disposal should follow the recommen- dations for the secure disposal of hazardous industrial wastes as described earlier.24,6,25 30 ------- Incineration of the resultant sludges may be feasible if the wastes are amenable to thermal destruction or recovery. A review of the operating characteristics and hazardous waste destruction potential for 11 incinerator designs has been published by the U.S. EPA Office of Solid Waste Management Programs.39 Soil Manipulation Site restoration may be achieved by: flushing the contaminant from the soil, _in situ contaminant detoxification, or microbial degradation of the contaminant. These approaches are often practical, if the depth of contamination is fairly shallow and the areal extent of contamination is relatively small. Therefore, chemical spills and contamination resulting from sludge dumping or land spreading are likely sources of contaminations for these restoration techniques. Soil flushing. Soil flushing is the process of flooding the area of contamination and collecting the seepage with a series of shallow well points (figure 12). This elutriation or washing process is most successful when the contaminant(s) is readily soluble in water. Slightly acidic solutions may be used to manipulate the soil pH, and thereby accelerate the flushing of certain contaminants, such as metal hydroxides. Elutriate collected by pumping the shallow well points should be properly treated if it does not meet existing discharge standards. Depending upon the nature of the contaminant, precipitation, adsorption, and/or chemical oxidation may be viable treatment techniques. Packaged wastewater treatment and water purification units offer several physical and chemical treatment modalities necessary to successfully remove many chemical contaminants. Treated and clarified elutriate may be recycled in the flushing process. Packaged treatment units for treating sanitary landfill leachate may be applicable.36 Precipitation with ferric sulfate (Fe2(SC>4)3) and lime (CaCC>3) has proven to be effective in removing arsenic flushed from contaminated soil.l^'^As noted earlier, several readily available sorbent materials, singularly or in combination, may provide satisfactory contaminant removal.35 Toxic and/or readily soluble hazardous precipitates, and contaminated sorbents should be disposed of in a manner that will avoid the recurrence of similar contamination problems (see: "Excavate and Bury at a New Site"). 31 ------- Figure 12 Saturated sand . Sub-soil WELL-POINT DEWATERING SYSTEM. Source: Ulric, G.P., and R.P. Singer. Water well manual. Berkeley, Premier Press, 1973. 156 p. 32 ------- In situ chemical detoxification. In situ chemical detoxification is the process of flooding or injecting the contaminated area with a medium that will detoxify or otherwise render the contaminant harmless. The approach is restricted to those contaminants that are readily degradable, have non-toxic breakdown products, and/or are convertible to insoluble precipitates. Heterogeneous mixtures of chemical wastes represent a more difficult problem because of the inhibitory influence of other constituents. For example, sodium hypochlorite (NaOCl), at 2500 parts per million (ppm) available Cl~, has been successfully used to detoxify cyanide contamination resulting from the indiscriminate dumping of industrial wastes (Sara, 1976). Metal complexed cyanides were not as susceptible to chlorination. Further discussions on the feasibility of chemically detoxifying specific hazardous materials may be found in "Recommended Methods of Reduction, Neutralization, Recovery, or Disposal of Hazardous Wastes, Oil and Hazardous Materials Technical Assistance Data System - OHM TADS and the "Chemical Hazard Response Information System (CHRIS).42'43'44 Microbial innoculations. The concept of using microorganisms to achieve site restoration through biodegradation may be applicable if the waste material is an organic compound. The ability of bacteria, fungi, and other microorganisms to degrade organics has been recognized for many years. Weisberg, et_al., examined the hazardous waste disposal practices of the petroleum refining industry and found that landspreading of refinery wastes has been practiced successfully for many years. Almost any hydrocarbon can be attacked by microorganisms, however straight chain hydrocarbons are more susceptible to microbial decomposition than branched or cyclic compounds.^Susceptibility also decreases as viscosity and molecular weight increase. Many microorganisms are able to form special enzyme systems that are capable of breaking down certain enzyme-inducing hydrocarbons, such as pesticides.48 Genera most capable of metabolizing hydrocarbons are largely aerobic; Pseudomonas, Achromobacter, and Alcaligenes are most frequently found in petroleum contaminated soil (Ellis and Adams, 1961). Facultative anaerobes associated with hydrocarbon decomposition include species from the genera Aerobacillus and Bacillus. Schwendenger seeded oil contaminated soil with Cellulomonas sp. and achieved improved hydrocarbon decomposition rates. Practices such as aerating, fertilizing, and manuring have been found to be 33 ------- Schwendenger seeded oil contaminated soil with Cellulomonas sp. and achieved improved hydrocarbon decomposition rates.46 Practices such as aerating, fertilizing, and manuring have been found to be beneficial to the decomposition process. For sites contaminated with oily wastes, Schwendenger recommends in situ biodegradation; to remove the contaminated soil merely defers the ultimate problem of proper disposal. Finally, it should be noted that microbial decomposition pay be more time consuming than other restoration approaches. Therefore, if a real and immediate public health or other environmental danger exists, physical and/or chemical restoration techniques will provide more timely results. 34 ------- DECISION ANALYSIS In the final analysis, contamination problems are seldom so simple that one decontamination technique will adeauately restore the contaminated site. Contamination problems are typically the result of disposal practices which have led to an accumulation of the waste material, discarded containers, miscellaneous debris, not to mention contaminated soil and groundwater. Therefore, proper management of these contaminants and restoration of the environment may reauire the use of more than one decontamination procedure. For example, groundwater pumping and treatment may be required in addition to _in situ treatment or excavation and burial. Specifically, the restoration decision should consider the following factors: 1. type of contaminant and its characteristics (organic, inorganic, toxicity, solubility, mobility, etc.) 2. level of contamination (soil and/or groundwater) and concentration 3. areal extent of contamination 4. quantity of contaminant at the source 5. technical feasibility of treatment and restoration methods for each contaminant 6. economic feasibility of treatment and restoration methods 7. institutional and political constraints, such as public acceptance of the selected restoration approach 8. cost of abandoning the resource and taking no action to restore the site. 'The cost of abandoning the contaminated land and groundwater resources should consider both tangible and intangible costs. Shuster examined the tangible costs (corrective measures, avoidance, litigation, and the provision of an alternative water supply) associated with six cases of water well contamination and found that costs ranged from $7,000 to $2,000,000.49 jn four other cases, the tangible costs associated with ungradino a contaminated drinking water supply or providing an alternative water supply, ranged from $50,000 to $300,000.50 Intangible costs (convenience, esthetics, social welfare, and psychic costs) are not easily estimated. Predictino intangible costs for land and groundwater resources is a relatively new science; reliable indices for such costs need further development. 35 ------- REFERENCES CITED 1. Lazar, Emery. Damage incidents from improper land disposal. Proceedings; the National Conference on Management and Disposal of Residues from the Treatment of Industrial Wastewaters, Washington, D.C., Feb. 3-5, 1975. Rockville, MS., Information Transfer, Inc. 15 p. 2. Office of Solid Waste Management Programs and Office of Water Supply. The report to Congress - waste disposal practices and their effects on groundwater. Washington, U.S. Environmental Protection Agency, 1976. (In preparation.) 3. Personal communication. Hans Mooij, Environment Canada, to D.G. Farb, Office of Solid Waste Management Programs, Dec. 22, 1975. 4. Personal communication. W.H. Walker, Geraghty and Miller, Inc., to D.G. Farb, Office of Solid Waste Management Programs, Sept. 1975. 5. McKinney, R.E. Microbiology for sanitary engineers. New York, McGraw-Hill Book Co., Inc., 1962. 293 p. 6. Farb, D.G. Land disposal of industrial wastes. Proceedings; the National Conference on Management and Disposal of Residues from the Treatment of Industrial Wastewaters, Washington, D.C., Feb. 3-5, 1975. Rockville, Md., Information Transfer, Inc. 19 p. 7. Personal communication. David Miller, Geraghty and Miller, Inc., to D.G. Farb, Office of Solid Waste Management Programs, Apr. 6, 1976. 8. Wehran Engineering Corp. Engineering report - Scientific, Inc. chemical waste processing facility and Kin-Buc sanitary landfill. Middleton, New York, 1975. 51 p. 9. Personal communication. W.L. Garrett, E.I. duPont Co., Inc., to D.G. Farb, Office of Solid Waste Management Programs, July 1975. 10. Salvato, J.A., W.G. Wilkie, and B.E. Mead. Sanitary landfill leaching prevention and control. Water Pollution Control Federation Journal 43(10): 2084-2100, Oct. 1971. 36 ------- 11. Haxc, H.E., Jr. Evaluation of selected liners when exposed to hazardous wastes. Presented at the Hazardous Waste Research Symposium on Residuals Management by Land Disposal, Tucson, Feb. 2-4, 1976. 12 p. 12. Personal communication. Paul Rhue, Geraghty and Miller, Inc., to D.G. Farb, Office of Solid Waste Management Programs, Apr. 6, 1976. 13. Cedergren, H.R. Seepage, drainage, and flow nets. New York, John Wiley and Sons, Inc., 1967. 489 p. 14. Personal communication. Dale Kosher, Office of Solid Waste Management Programs, to D.G. Farb, Office of Solid Waste Management Programs, Apr. 7, 1976. 15. Chow, V. Handbook of applied hydrology - a compendium of water resources technology. New York, McGraw-Hill Book Co., 1964. 1418 p. 16. Office of Air and Water Programs. Methods for identifying and evaluating the nature and extent of nonpoint sources of pollutants. U.S. Environmental Protection Publication 430/9-73-014. Washington, U.S. Government Printing Office, 1973, 261 p. 17. Lenahan, Torn. There is a place for grouting in underground storage caverns. Bulletin of the Association of Engineering Geologists, 10(2): 137-144, 1973. 18. Office of Water and Hazardous Materials. Inactive and abandoned underground mines water pollution prevention and control. U.S. Environmental Protection Publication 440/9-75-007. Washington, U.S. Government Printing Office, 1975. 338 p. 19. Personal communication. B.G. Taylor, Applied Nucleonics Company, to D.A. Rodgers, Contracts Management Division, Jan. 19, 1976. 20. Personal communication. Robert Jensen, Air Frame Manufacturing and Supply Co., North Hollywood, Calif., to Robert Landreth, Solid and Hazardous Waste Research Division, Feb. 23, 1976. 21. Personal communication. L.T. Wantland, Halliburton Services, to D.G. Farb, Office of Solid Haste Management Programs, Jan. 1976. 37 ------- 22. Lindsey, A.W. Ultimate disposal of spilled hazardous materials. Chemical Engineering 82(23): 107-114, Oct. 27, 1975. 23. Metcalf, J.C. Hazardous materials labelling and placarding systems - state-of-the-art. Washington, D.C., Office of Solid Waste Management Programs, 1975. (Unpublished report.) 24. Fields, T., Jr., and A.W. Lindsey. Landfill disposal of hazardous wastes: a review of literature and known approaches. U.S. Environmental Protection Publication SW-165. Washington, U.S. Government Printing Office, 1975. 36 n. 25. Barr Engineering. Chemical waste land disposal facility demonstration grant application - Minnesota Pollution Control Agency. U.S. Environmental Protection Publication SW-87d, 1975. 178 p. (Available through National Technical Information System [NTIS] as PB~ 249 77). 26. Farb, D.G., and S.W. Ward. Information about hazardous waste management facilities. U.S. Environmental Protection Publication SW-145. Washington, U.S. Government Printing Office, 1975. 130 p. 27. Leshendok, T.V. Hazardous waste management facilities in the United States. U.S. Environmental Protection Publication SW-146.2. Washington, U.S. Government Printing Office, 1976. 61 p. 28. Foster D. Snell, Inc. Potential for capacity creation in the hazardous waste management service industry. U.S. Environmental Protection Agency, 1977. (In preparation; to be distributed by National Technical Information Service, Springfield, Va.) 29. Personal communication. G.B. Seaborn, Minnesota Pollution Control Agency, to D.G. Farb, Office of Solid Waste Management Programs, Feb. 17, 1976. 30. Niessen, Walter. Preliminary feasibility study - leachate control strategies for Llangollen Landfill, New Castle County, Delaware. West Chester, Pa., Roy F. Weston, Inc., 1974. 60 p. 31. Bass, S.H., Jr. Review and command assessment of the installation restoration program. U.S. Army Materiel Command. Edgewood Arsenal, Maryland, 1976. 129 p. 38 ------- 32. Memorandum. Wilson Talley, Office of Research and Development, to the Assistant Administrators, U.S. Environmental Protection Agency, March 29, 1976. 33. Gibb, J.P., and E.W. Sanderson. Cost of municipal and industrial wells in Illinois, 1964-1966. Urbana, Illinois State Water Survey, Circular 98, 1969. 22 p. 34. Gibb, J.P. Cost of domestic wells and water treatment in Illinois. Groundwater, 9(5): 40-49, Sep.-Oct. 1971. 35. Liskowitz, J.W., et al. Capabilities of selected sorbents for removal of leachate contaminants from industrial sludges. Presented at the Hazardous Waste Research Symposium on Residuals Management by Land Disposal, Tucson, Feb. 2-4, 1976. 20 p. 36. Personal communication. C.E. Janson, Met Pro Systems, Inc., to D.G. Farb, Office of Solid Waste Management Programs, Jan. 13, 1976. 37. Personal communication. Bernard Stoll, Office of Solid Waste Management Programs, to D.G. Farb, Office of Solid Waste Management Programs, Feb., 1976. 38. Jorgensen, S.E. Recovery of ammonia from industrial wastewater. Water Research 9(12): 1187-1191, Dec. 1975. 39. Scurlock, A.C., A.W. Lindsey, Timothy Fields, Jr., and D.R. Huber. Incineration in hazardous waste management. U.S. Environmental Protection Publication SW-141. Washington, U.S. Government Printing Office, 1975. 104 p. 40. Personal communication. Thomas lezzi, Rohm and Haas, to D.G. Farb, Office of Solid Waste Management Programs, March 17, 1976. 41. Personal communication. Martin Sara, Danes and Moore, to D.G. Farb, Office of Solid Waste Management Programs, Feb. 1976. 42. Ottinger, R.S., et al. [TRW Systems Group] Recommended methods of reduction, neutralization, recovery or disposal of hazardous wastes, vols. I - XVI. U.S. Environmental Protection Publication 670/2-73-053. Washington, U.S. Government Printing Office, Aug. 1973. (Available through National Technical Information Service, Springfield, Va.) 39 ------- 43. Office of Oil and Hazardous Materials. Oil and hazardous materials assistance data system - OHMTADS. U.S. Environmental Protection Agency. Washington, U.S. Government Printing Office, 1974. 9 p. 44. U.S. Coast Guard. Chemical hazards response information system. Department of Transportation Publication CG-446-2. Washington, U.S. Government Printing Office, 1974. 2 volumes. 45. Jacobs Engineering Co. Assessment of industrial hazardous waste practices, petroleum refining industry. U.S. Environmental Protection Agency, 1977. (In preparation; to be distributed by National Technical Information Service, Springfield, Va.) 46. Schwendinger, R.B. Reclamation of soil contaminated with oil. Journal of the Institute of Petroleum 54(535): 182-197, July 1968. 47. Ellis, Roscoe, Jr., and Russell Adams, Jr. Contaminating soils by petroleum hydrocarbons. Advances in Agronomy, 13: 197-216, 1961. 48. Rogers, C.J., and R.E. Landreth. Degradation mechanisms: controlling the bioaccumulation of hazardous materials. U.S. Environmental Protection Publication 670/2-75-005. Washington, U.S. Government Printing Office, 1975. 14 p. 49. Shuster, K.A. Gas and leachate generation and control in landfills. Presented at the University of Wisconsin Continuing Engineering Short Course, Madison, March 29-31, 1976. 50. Personal communication. A.B. Giles, Office of Solid Waste Management Programs, to D.G. Farb, Office of Solid Waste Management Programs, March 1976. ya!512 SW-677 40 ft U. S. GOVERNMENT PRINTING OFFICE : 1978 260-880/18 ------- |