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ANco I a-9 U a� W C.a i W ' G� r • 1 l ti Toxic leachate collects in an elementary school 6 parking lot adjacent to Love Canal. Today's I hazardous waste disposal sites are more Low-permeability clay barriers, used by landfill operators c contain sophisticaPed, butl7itics say they may still be hazardous wastes, can be rendered highly permeable by certain less secure than they are designed to be. aggressive chemicals, recent research shows. That's only one of the troubles that beset toxic waste dumps, some of which have had to close or undergo extensive remedial work as a result. Here's a review of some of those problems and of the implications of the new findings about the vulnerability of clay liners. ALLEN tNORRISON of effects ensued: toxic pools formed at permeable. Assistant Editor the surface, subsidence exposed buried To put the situation in context, let's IVIL ENGINEERING wastes, contaminated groundwater even- first take a look at current practice in haz- tually entered basements of surrounding ardour waste disposal. A state-of-the-art WHEN 240 FAMILiEs had to evacuate their homes, and run-off collected on adjacent chemical landfill is likely to look like the surface areas,as pictured above,and con facility is -Iayered e multiin i-, internally Typically, inttech homes adjacent to the Love Canal chemi di- cal -cal waste dump in the summer of 1978,it taminated local sewers. vided for enhanced structural stability, focused national attention for the first Are today's landfills better? and includes one or more synthetic mem- time on the dangers of improper disposal Chemical landfill operators insist that branes. Waste deposited will be a mix of of hazardous chemical wastes. It became suddenly apparent that the technolo y of the state-of-the-art today is far advanced, drummed and bulk waste, with a maxi- " but critics c secure"landfilling of chemicals is still inbut that the "secure" mum of 15% liquids in the drums. The its infancy, landfill is still more dream than reality. bulk waste may consist of sludges,debris, Love Canal was filled with chemical Now a new c in in t e armor o e contaminated soils, and other materials. wastes from the Hooker Chemical Com- "secure" landfill appears: researchers are At least 10 ft (3 m) of compacted clay peony beginning in the late 1940x, ata finding that the clay liners typically used will lie beneath the deepest point of exca- art, if t a in these landfills may be vulnerable to the vation, and several feet more will Com- time when the state-of-the-art, chemicals which can prise the overliner or cap. Backfilling and served at all,consisted chiefly of contain- effects of cert long the wastes in steel drums and dump- modify compacted clay soils that were of placement of successive tiers of waste will f ing them in the nearest available pit low permeability, rendering them highly contentstpriorecompaction tto closing. Otherfeatures where the natural unconsolidated soil was ' provide for leachate and gas collection supposed to offer low permeability. and in-situ monitoring. ' What happened at Love Canal has been In a paper published in ASCE's recent j compared to an overflowing bathtub. A new chink in the armor of the volume The Hazardous Waste Dilemma { Rainwater combined with the large 66secure"landfill has appeared: Issues and Solutions,and-in an interview amounts of liquids already contained in researchers are finding that the with CE, environmental engineer Peter the trench(both free and in drums,which clay liners typically used in Skinner discussed the design and con subsequently corroded) to create large these landfills may be struction of such landfills and the perfor volumes. of leachate. Hooker claims to vulnerable to the effects of mance problems which can crop up.Skin- have capped the trench,and that the cap certain chemicals which can ner, who prepares technical information was later removed by another party, butfor the this claim is in dispute. The leachate modify compacted clay soils al's envie nmental litigat on,helped build mi rated alon two ermeable hocizontaT that were of low permeability, the state's case against Hooker Chemical � Lgrs: through a top layer o si t, c ay, renderi t e highly Company and is the author of a"limits to and fine sand, and through a lower layer permeable. landfills" bill pending in both houses Of of dessicated clay. In addition,a number 0360-0556/61/Ooo7-0060/$010 60 Civil Engineering-ASCE July'198',