Environmental cut-off for deep excavations

In an underground fluid impervious barrier wherein a narrow trench in the earth formed by slurry trench excavation has a plastic sheet embedded in backfill material filling said trench, the improvement in said plastic sheet comprising,

• A. at least a pair of primary wall panel elements, each one of said pair of primary wall panel elements comprising,
• (a) a pair of spaced apart primary tubular channel members having facing surfaces and oppositely facing surfaces, respectively, and a dimension transverse to the direction of said slurry trench excavation which is substantially equal to the width of said slurry trench excavation,
• (b) a plastic sheet spanning the space between said tubular channel members and having lateral ends which are sealingly joined to said facing surfaces on said spaced apart tubular members, respectively,
• (c) means forming a slot in each of said oppositely facing surfaces or primary tubular channel members of said pair of primary elements and,
• B. a secondary wall panel element in the trench space between said pair of primary wall panel elements, said secondary wall panel element comprising:
• (d) a pair of spaced apart rigid secondary members larger in width than said slot and smaller than any internal dimension of said primary tubular members telescoped in said primary tubular channel members,
• (e) a plastic sheet having vertical lateral ends and means sealingly joining said vertical lateral ends to respective ones of said rigid secondary members and,
• C. means sealingly filling the space between the telescoped primary and secondary tubular members.

In an underground pollution control barrier comprising a narrow slot in the earth formed by slurry trench excavation, a backfill material filling said narrow slot and flexible plastic sheet barrier means embedded in said backfill, the improvement comprising,

• a plurality of the primary flexible plastic sheets and rigid plastic channel members and, a plurality of secondary flexible plastic sheets and rigid plastic secondary members, constructed as as follows:
• a pair of vertical spaced apart rigid plastic channel members having mutually facing first surfaces and oppositely facing second surfaces,
• a primary plastic sheet spanning the space between said first surfaces, said primary plastic sheet having lateral ends which are sealingly joined to said first surfaces,
• means forming a slot in each said oppositely facing surfaces,
• first and second spaced apart vertical rigid plastic secondary members, said first and second rigid plastic members having mutually facing third and fourth surfaces, respectively,
• a secondary plastic sheet spanning the space between said mutually facing third and fourth surfaces and having lateral ends which are sealingly joined-to said facing third and fourth surfaces, respectively,
• each said rigid plastic secondary member being of a size as to telescopically receive in one of the first named pair of spaced apart channel members with said second flexible plastic sheet passing through said means forming a slot.