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26 27 Identification of Defects Seams shall be inspected by the geomembrane installer and the owner’s representative before,during, and after field seaming to identify all dirty and wrinkled areas and any defects . Evaluation of Defects i. Each suspect location (both in geomembrane seam and non-seam areas) shall be non- destructively tested . Each location which fails non-destructive testing shall be marked, numbered, measured, and posted on the daily installation drawings and subsequently repaired . ii. Defective seams, tears or holes shall be repaired by capping or cutting out the defective seam and re-seaming . Single seams in excess of 20% of their length requiring repair should be entirely removed and re-welded . iii. Each patch or capping shall extend a minimum of 150 mm (6 inches) in all directions beyond the defect . iv. All repairs shall be located, measured, non-destructively tested, and recorded . Geomembrane Penetrations Any structure or containment area built from man-made materials (metal, concrete, etc .) shall not allow protrusions, pinch points, or movement of the supporting structure that might damage the geomembrane and adversely affect the ability of the geomembrane to perform its containment function . All pipes, drains, fitting, etc ., which are to be installed beneath the geomembrane, should be in place and ready to be covered with the geomembrane before geomembrane deployment . If possible, avoid cutting the geomembrane at details by using factory fabricated pipe boots that can be seamed to panels in the field . The following directions provide additional details for handling geomembrane penetrations: i. Pipes Whenever possible, avoid slitting geomembrane panels for piping details until a prefabricated pipe boot is ready for immediate installation . Cuts made in the geomembrane for clearance over penetrations should always be made as small as possible to minimize patch work . Generally, it is preferred to let the geomembrane straddle a relatively small protrusion (for later detail work) provided that a rag or towel is taped over the pipe to avoid damage to the geomembrane . Factory prepared pipe boots should fit snugly but not require excessive force to pull over a pipe . If a pipe boot feels overly snug but workable, try applying either talc powder or using compressed air with a nozzle to float the boot sleeve over and along the pipe . Pipe boots should never be used if the force required to install them stresses or weakens the boot . When properly installed, the pipe boot will lay flat against grade surrounding pipe without leaving pockets that may become stressed during or after placement of backfill . Pipe boot aprons should be seamed to the parent geomembrane using one of the repair techniques described in the Seaming Section above . Proper leak proof sealing of pipe boots should be verified by non-destructive methods . The pipe boot sleeve should be attached to the pipe using butyl tape between the pipe and boot and two stainless steel band clamps . When cover materials are not used (see section 3 .01 .F below), splash pads or additional geomembrane layers shall be used for all inflow pipes to prevent long term wear and damage to the geomembrane caused by the direct impact of the inflow on the geomembrane panels . The pads should be welded on top of the geomembrane panels and tested according to sections 3 .01 .C and D, respectively . Common splash panel sizes are 1 .2 to 1 .8m (4 to 6 ft) in all directions . However, larger sizes may be required depending on the amount of inflow pipes and the height to the discharge point . ii. Concrete Where bonding a geomembrane to concrete (or masonry) is required, the concrete surface should be smooth, clean, dry, and free of any sharp protrusions or rock in the backfill . Geomembrane to concrete seals shall be accomplished with mechanical anchors (e .g . fasteners, termination bars) . An approved sealant is placed between the geomembrane and the concrete surface to ensure sealing . The geomembrane fixed to a concrete structure must be on firm soil subgrade that will not deform and stretch the geomembrane . Compacting of the soil subgrade around such structures must be performed with particular care so excessive differential movement between the concrete and soil subgrade does not occur . iii. Drains The geomembrane shall be mechanically fastened to the concrete structure at the location of water discharge . This detail requires the installation of a concrete base or structure at the location of the drain . Where water enters or exits the geomembrane area, e .g ., ponds, reservoirs, and canals, this point must have proper geomembrane termination so as not to damage the geomembrane . The area of inflow must be anchored with a trench of a depth or attached to a structure as designed by the Project Engineer or Design Professional . The geomembrane is installed and then anchored to the concrete prior to the covering with soil . iv. Aerators Geomembrane design in lagoons with aerators should require ballast, e .g . precast concrete slab, on the geomembrane to prevent uplift and to provide a pad to support the aerator when the water level is lowered . Many examples exist of geomembrane damage due to an aerator settling on the geomembrane or where the geomembrane was lifted into the aerator . Other aerator damage is frequently evidenced as cuts in the geomembrane along a specific elevation on the side slope where the aerators have been pulled to shore for maintenance . Geomembrane sheets are easily damaged by the sharp edges of a 6 mm (0 .25 inch) thick stainless steel plate of an aerator . Cover Materials When placing cover material or initially filling the containment area, it is important to ballast the geomembrane into the perimeter anchor trench before covering or filling . The anchor trench or perimeter shelf area should be the last area covered to complete the cover process . Under all operating conditions, protection of the geomembrane will be required . Care should be taken when covering the geomembrane to prevent any damage . At no time will construction equipment be allowed to operate or drive directly on the geomembranes . Any damage to the geomembrane should be repaired prior to proceeding with cover material placement . Costs associated with repairs are the general contractor’s responsibility . The cover material shall be placed as soon as practical, in conjunction with or upon completion of the geomembrane installation or as the installation progresses to minimize traffic on the geomembrane and damage . Access roads for clean soil cover should be maintained to provide 0 .3 m (12 inch) minimum and for heavier equipment on haul roads a minimum of 0 .45 m (18 inch) preferable between the excavation equipment and geomembrane at all times . Some geomembrane Installation Instructions Page 7 of 9 Installation Instructions Page 8 of 9 InterWrap.com CANADA | USA | EUROPE | INDIA | CHINA CANADA | USA | EUROPE | INDIA | CHINA InterWrap.comPDF Image | GEOMEMBRANES
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