3Selection of sites for Waste Disposal facilities Receptor related attributesPopulation with in 500 mDistance to nearest drinking wellUse of site by nearby residentsDistance to nearest office buildingLand useCritical Environment
42. Pathway related Attributes Distance to nearest surface waterDepth to ground waterType of contaminationPrecipitationSoil permeabilityBed Rock PermeabilityDepth to bed rockSusceptability to erosion and runoffClimatic factors relating to air pollutionSusceptibility to seismic activity
53.Waste and related attributes ToxicityRadioactivityIgnitabilityReactivityCorrosivitySolubilityVolatility
64.Waste Management related attributes Physical stateWaste quantityWaste compatibilityUse of linersGas TreatmentLeachate TreatmentSite securitySafety measures
8Site investigation criteria Sub Soil Investigation: type of soil, depth of GWT and bedrock, permeability of various strata, strength parameters, extent of availability of liner materialsGround Water / Hydro geological Investigation: Depth of GWT, GW flow direction, Baseline GW quality parametersTopographical Investigation: To compute the earth work quantities preciselyHydrological Investigation: To estimate the quantities of runoff for appropriate design of drainage facilitiesGeological Investigation and Seismic Investigation: to delineate the bedrock profile beneath the landfill base
9CriteriasubcriteriaSignificanceSoilPermeabilityRelease of pollutants- Low permeability requiredpHTendency of soil to aborb heavy metals- high pHCation exchange capacityAbility of soil to attenuate some contaminats- High cation exchangeSurficial soilAffect degree of attenuation-surficial soil with low permeability
10CriteriasubcriteriaSignificanceGeologyBedcrop and outcroppingCarbonate rocks susceptible to solutionFractured rock-pollution migrationMass permeabilityControl migration of contaminantsFaultsRelease of pollution
11CriteriasubcriteriaSignificanceGround waterAquiferWith low potential use preferredGround water qualityPoor groundwater quality- best suitable locationGround flow systemSites where direction of GW flow away or flow is upward
12CriteriasubcriteriaSignificanceMonitoring aspectsSites that are easy to monitorSlopeSlope of groundSlopes greater than 15% or 22% is preffered
14Hydrogeological aspects of selection of waste disposal sites CONDITIONS AT THE SITEPROVISION OF DATA FOR DESIGN AND MANAGEMENT OF WASTE DISPOSAL FACILITIES
15Assessment of regional and local geology Assessment of local surface hydrologyIdentification of main hydrogeological units (aquifers,aquiclude etc)Ground water mechanismsLocal structural featuresMeasuring GWL and hyraulic gradientEstimating hydraulic conductivityGround water chemistrySurface and ground water receptors of contaminationPresent and future development of GWCharacteristics of materials present in saturated and unsaturated zones
18Changes Occurring in a Waste Dump Biological ChangesDuring the aerobic decomposition, carbondioxide is the principal gas produced.Once the available oxygen has been consumed, the decomposition becomes anaerobic and the organic matter is converted toCarbondioxideMethaneTrace amounts of ammoniaHydrogen sulfideMany other chemical reactions are also biologically initiated therefore it is difficult to define the condition that will exist in any waste dump at any stated time.
19Chemical ChangesThe chemical reactions that occurs in a waste dump areDissolutionSuspension of waste materialsBiological conversion products in the liquid percolating through the wasteEvaporation and vaporization of chemical compoundsSorption of volatile and semi volatile organic compounds into the waste materialDecomposition of organic compoundsOxidation-reduction reactions affecting metals and the solubility of metal salts.The dissolution of biological conversion into the leachate is of special importance because these materials can be transported out of the waste dump with the leachate.
20Physical Changes The important physical changes in waste dumps are Lateral movement of gases in the wasteEmission of gases to the surrounding environmentMovement of leachate within the waste and into underlying soilsSettlement caused by consolidation and decomposition of the waste.
22SUBSURFACE DISPOSAL TECHNIQUES Deep wellsInjection wellsMine ShaftsEntrenchmentLandfills
231.Deep-well DisposalIn rock (not soil), isolated from freshwater aquifers; waste is injected into a permeable rock layer hundreds to thousands of meters below the surface.Deep-well injection of oil-field brine has been important to control water pollution in oil fields for many years.
24USESPetroleum industries- recovery of oil and for brine waste
252.INJECTION WELL DISPOSAL Deep-well injection system -- disposal in sandstone or fractured limestone capped by impermeable rock and isolated from fresh water. Monitoring wells are a safety precaution.Disposal of hazardous wasteHazardous liquid waste placed in well confined geological formations that are deep below earths surface
27Deep well injection directly introduces liquids into a deep aquifer in the subsurface environment via pressurized wells.CLASS I WELLS - used for disposal of hazardous and non-hazardous industrial or municipal wastes.CLASS II WELLS - used for injection of oil field brines and other hydrocarbon wastes.CLASS III WELLS - used for solution mining processes.CLASS IV WELLS - those which historically disposed of radioactive wastes (this is no longer done).CLASS V WELLS - used for any activity not mentioned above, such as geothermal steam mining operations.
29Parameters- Construction of deep wells Low pressureLarge area extentHigh porosity and permeabilityNature of aquiferSeperation from freshwater horizonGeological strataType of waste
303. MINE SHAFTSSolidified waste packed in non breakable containers ( concrete cylinders, drums)These are transported down the shafts placed in chambersChambers sealedIndefinite life- unless corroded from insideSites chosen – Salt, potash and gypsum deposits
314.Entrenchment Modified landfill method Refuse placed in trenches & buriedTrenches- 3m deep, 1mwide, 10m longMonitored for 24 monthsIf made in clayey soil- no problems of GW contamination & odour problemSites can be used for vegetable production
34The components of the engineered landfill are Liner systemLeachate collection and treatment facilityGas collection and treatment facilityFinal cover systemSurface water drainage systemAn environmental monitoring systemA closure and post closure plan
35PHASES OF LANDFILL PROJECT 1. Siting 2. Designing 3. Construction 4. Operation 5. Closure of landfill
361. SITING A LANDFILL Topography Alluvial/ sedimentary formations suitableBase above saturation zonePrevent standing waterPrevent erosion and runoffExcessive sloping (1% but less than 10%)
38Air qualityMonitoredControlledAvailability of transport systemConvenient transport facilitiesHydrogeologyLow permeability ( not exceed 107 cm/s)Texture of soilFine grained soil – low Leachate penetration
392. DESIGNING-Landfill Section Depending on:Topography of the areaDepth of ground water tableAvailability of suitable daily cover material.1.Above ground landfillsAbove ground landfills are used in those areas where GWT is high.-Used when terrain is unsuitable for excavations
402.Below ground landfillsuitable for areas where adequate cover material is available and GWT is not near the surface.Solid waste dumped in trenches excavated in soilTrenches-Length :100 to 300mDepth: 3 mWidth :5 to 15 mSide slope : 2:1
413.Above and below ground landfill-------- 4.Slope landfill 5.Valley landfills
42Implications of Disposal Above, On and Below Ground Surface Above Ground LandfillsAdvantageDrainage of leachate is by gravity.Thickness of unsaturated zone belowthe landfill is large.Landfill is conspicuous and thus cannotbe ignored.Poor surface drainage due tosettlement of final landfill surface canbe avoided.Inspection of the entire facility i.e. finalcover, leachate collection system andgas collection system is easier.DisadvantageThey alter the land usepattern of the area.They have more surface areaexposed to elements of naturesuch as wind, rain and requiresignificant erosion controlmeasures.
43On and Just Below Ground Surafce DisadvantageLeachate collection throughregular pumping.Require good surface waterdrainage measures iflocated in low lying areasand are closer to groundwater table than aboveground landfills.AdvantageMore waste can be stored per unit land area in comparison to above ground landfills.Efficient use can be made of the excavated material but using it as landfill cover.Productive use of the flat landfill surface can be made on completion of landfill.Long term slope stability and erosion control requirements are not very critical in such landfills.
44Landfills Deep Beneath the Earth’s Surafce Wastes can also be dumped in underground openings, tunnels or caverns, however the cost of construction in such cases is extremely high.If the disposal is in soil where water table is high, the waste would always be surrounded by ground water and, irrespective of the multiple barriers used for waste isolation, the potential of ground water contamination would always be high.
45If waste is disposed in strong competent rock: the very low permeability of the rock mass coupled with multiple barriers layers ensures long term containment of the waste.Such disposal techniques are adopted for extremely hazardous wasteWaste disposal deep beneath the ground surface has the least impact on the land use pattern.
46Landfill LayoutA landfill site will comprise of the area in which the waste will be filled as well as additional area for support facilities. With in the area to be filled, work may proceed in phases with only a part of the area under active operation.
49The main design phase includes Design of liner, leachate collection and TreatmentGas Collection and TreatmentCover SystemLandfill StabilitySurface Water DrainageEnvironmental Monitoring
50a. Phase:-sub area of the landfill.consists of cells, lifts, daily cover, intermediate cover, liner and leachate collection facility, gas control facility and final cover over the sub-area.designed for a period of 12 to 18 months.b. Cell:-volume of material placed in a landfill during one operating period usually one day.
52c. Daily cover:--It consists of 15 to 30 cm of native soil that is applied to the working faces.Purpose of cover :To control the blowing of waste materialsTo prevent rats, flies and other disease vectors from entering or exiting the landfillTo control the entry of water into the landfill during operation
53d. Lift:--It is a complete layer of cells over the active area of the landfill.-Typically each landfill phase is comprised of a series of lifts.-Intermediate covers are placed at the end of each phase; these are thicker than daily covers and remain exposed till the next phase is placed over it.e. Bench:--A bench is a terrace which is used when the height of the landfill exceeds 15 to 20 m.f. Final cover layerThe final lift includes the cover layer.applied to area after all landfill operations
56g. Leachate Collection Systems To prevent migration of leachate generated inside a landfill from reaching the soil and ground water beneath the landfill.Function of leachate collection facility:Remove leachate contained with in the landfill by the liner system for treatment and disposal.Control and minimize leachate heads with in the landfill.Avoid damage to the liner system.Landfill liner comprise ofCompacted claysGeomembranesGeosynthetic clay linerCombinations
57h. Gas Collection Systems The uncontrolled release of landfill gas, methane contributes to the green house effect.Landfill gas can migrate laterally and potentially cause explosions.Landfills are therefore provided with gas collection and processing facilities.The rate of gas production varies depending on the operating procedure.The decision to use horizontal or vertical gas recovery wells depends on the design and capacity of the landfill.
58Reasons why landfill operated in phases Progressive use of the landfill area such that at any given instant of time a part of the site may have-a final cover,-a part being actively filled,-a part being prepared to receive waste and-a part in an undisturbed state.Minimizes the area required for landfill operations- concentrates waste disposal activities within prepared areas.Reduces leachate generation by keeping areas receiving waste to a minimum.Enables progressive installation of leachate and gas control.Allows clean surface water runoff to be collected separately.
593. Construction & Operation Design Process Site DevelopmentConstruction ScheduleMaterial and Equipment RequirementEnviornmental Control During OperationClosure and Post Closure Programmes
601. Material requirementMaterial requirement plan for the construction of various phases of the proposed landfill -preparedMaterials may be required forGranular material for ground water drainage, leachate drainage blanket, gas venting and collectionClay, sand, synthetic membrane for the liner system and final cover systemSuitable fill for internal and external bundsBase course and sub base course materials for haul roadsSuitable material during site operations for daily coverSuitable soils or granular or screened material for pipe work zone, drainage and protection layers above the barrier layerSub soil and top soil for restoration layers
612.Equipment Requirement The type, size and number of equipment required will depend on the size of the landfill and maneuverability in restricted spaces.Equipments are required at the landfill siteFor excavating, spreading and leveling operations crawler tractors/dozers are requiredCompactors/rollers for compactingWheeled loader-back hoes for excavating, trenching, loading and short hauling
623. Environmental control during operation Carried out to minimize the impact of the landfilling operation on the nearby residents. This can be done by:Providing screens in the active areasPresence of birds at the landfill site (nuisance if the landfill is being constructed near the airport)over come by:Use of noise makersUse of over head wiresUse of recording of the sounds made by birds
63Problems of wind-blown paper, plastics etc overcome by Portable screens near the operating facesDaily removing the accumulated materials on the screenDust control can be achieved by spraying waterProblems of flies, pests, mosquitoes and rodents can be controlled by :-placing daily cover-by eliminating stagnant water.
644.Closure and post closure plan A closure and post closure plan shall be made to ensure that a landfill will be maintained for years in the futureA closure plan includesLandfill cover and landscaping of the completed site.Long term plans for the control of runoff, erosion, gas and leachate collection & treatment.
65Post closure plan includes Routine inspection of completed landfill.Maintenance of surface water diversion facilities, landfill surface grades, the condition of liners.Maintenance of landfill gas and leachate collection equipment.Long term environmental monitoring plan so that no contaminants is released from the landfill site.