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<br /> the N.S}.State Legislature at press A produced, will the leachate be contained
<br /> Skinner notes that "secure" landfills by the clay and (when used)plastic barri- Why has there been so little
<br /> fail in three basic ways: ers? Knowledgeable sources contend that research on the effects of
<br /> tf • Operating methods may allow too the effects of many chemicals on clay aggressive chemicals on the
<br /> ,much liquid to enter the landfill prior to soils are not well understood; moreover, barriers landfillers use to
<br /> closing.R ' fall,too many buried liquids, designers and operators of chemical land- contain them?Says Earl Jones:
<br /> Cand the hues volumes of water used to fills have failed to date to incorporate "These things (hazardous waste
<br /> h t occasional chemical fires at the site much of what is known into their routine landfills) have grown up from
<br /> arca common avenues through which practice. Cif dumps, and the operators
<br /> cxcess water will enter the fill; The need for transfer of technical Jr P , P
<br /> L • Leachate collection systems may information from the soils research field fust don't have the mt?n@ " The
<br /> contain design or installation .defects to the hazardous waste disposal field is Old City dump mentality of"out
<br /> which result in excess leachate; critical,according to D. Earl Jones.Jones of sight, out of min has been
<br /> • Consolidation,a result of several fac- is chief of architecture and engineering carried Over, he says, ®neo the
<br /> tors including lack of compaction of con- for the Federal Housing Administration far more comp eX ®e of ti xic
<br /> tents,pumping out of leachate,and corro- and a member of ASCE's Expansive Soils waste,disposal.
<br /> sion of drums,may result in local or gen- Research Council. While taking pains to
<br /> era)subsidence of the clay cap. point out that he is not an expert on haz-
<br /> The solutions to these problems,Skin- ardous waste disposal, he believes recent
<br /> ncr says, are only "semi-solutions. You information in, his field of expertise— pounds into the soil to stabilize its miner-
<br /> avoid excess leachate by not burying liq- soils research—about the chemical prop- alogical makeup; at the same time, re-
<br /> uids. This depends on the compliance of erties of expansive clays is of urgent con- ports Jones, the process significantly in-
<br /> operators requiring government sur cern to operators of chemical landfills creases the soil's permeability.
<br /> veillanee, - rict precautions to prevent (see box, next page). The implications for hazardous waste
<br /> rainwater from collecting
<br /> __in open pits, Chemicals that eat clay disposal site operators are serious: the
<br /> and other measures.bolutions to the oth- impermeability of the clay blankets used
<br /> er problems are equally costly,and some Research performed by a Denver firm i–n–ffi-e–se-1—andfills can be reduced by_exW-
<br /> require perpetual monitoring and mainte- has demonstrated that expansive clays of sure to strong caustics. And, says Jones,
<br /> nance. For Skinner s sr. erratic of failure the sort often used in chemical landfills t este acts may not be limited to expan-
<br /> modes for landfills,see Fig. 2. can be permanently altered by the use of sive clays. "Chances are," he says, "the
<br /> If,despite the best efforts of designer, strong caustics. This firm stabilizes foun- clay (used in these landfills) will be
<br /> operator,and regulator,excess leachate is dation soils by injecting various com- expansive, but whether it is or not, the
<br /> r
<br /> 0101verlinerBenchmarksinitial cap slope®11%
<br /> pressure relief
<br /> Telltale monitor Synthetic liner
<br /> r'.
<br /> Topsoil Sand dram layer
<br /> Overlmer A --
<br /> ,,.,�,. \\ French drain i
<br /> \ y Bulkwaste:sludges,debris,
<br /> contaminated soils ..a.1
<br /> \� Stand pipe
<br /> Arnot stone \
<br /> stecage
<br /> French drain
<br /> V Daily alkaline
<br /> \ Drummed waste backfill
<br /> Berm slope(external) \\
<br /> \ `SulxelI berm
<br /> Maximum leachate level \ L
<br /> Potentiomeiric surface \\
<br /> (level may veryp \
<br /> Berm slope(internal) \\ *
<br /> e 'I
<br /> Basal liner®1 x 10-'m'/s
<br /> Syntt�ticmambrane Telltale Isyer inert aoltlf•et.
<br /> In-situ clay @ 1x10-'m'/s
<br /> Fig. I This hazardous waste landfill,based on design concepts design, or lower than the highest possible groundwater level, or j
<br /> meorporated in two proposed landfills in western New York State, potentiometric surface.Some designers maintain that the higher level is
<br /> Ocludes a number of state-of-the-art features.An internal berm enhances preferable because it produces higher head outside the fill than inside,
<br /> structural stability.Drums are placed vertically in tiers, with bulk wastes making infiltration of water more likely than exfiltration of leachate. N. Y.
<br /> added, then backfilled.Any leachate penetrating the bottom synthetic State environmental engineer Peter Skinner likens a disposal site floating
<br /> .net,•ay be detected by monitoring the gravel telltale layer.An on a high groundwater level to a "clay barge,-such an arrangement may
<br /> elaborate drainage system collects gases and liquids for removal and jeopardize secure containment of the chemical wastes inside. (Diagram
<br /> Treatment. The maximum leachate level may be set higher,as in this courtesy Peter N.Skinner.)
<br /> July 1981 Civil Engineering-ASCE 61
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