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directly below each overlap of geomembrane that is to be seamed to <br />prevent buildup of moisture between sheets and prevent debris from <br />collecting around pressure rollers. <br />d. Aemove seaming sheets and excess geomembrane trimmed to provide <br />required overlap. <br />3. Use conventional extrusion welding as a secondary method for seaming <br />between adjacent panels and as a primary method of welding for detail and <br />repair work. <br />a. Purge heat-degraded extrudate tram barrel of extruder under the <br />following conditions: <br />t, Prior to beginning a seam. <br />2. Whenever extruder has been inactive. <br />b. Place a smooth insulating plate or fabric beneath hot welding apparatus <br />aher usage. <br />c. Use clean and dry welding rods or extrudate pellets. <br />d. Complete grinding process without damaging geomembrane according <br />to MANUFACTUREA's instructions no more than one (11 hour prior to <br />seaming operations. <br />e. Prevent exposed grinding marks adjacent to an extrusion weld. Do not <br />extend exposed grinding marks more than one-quarter 11/4! inch from <br />seam area. MANAGER and CERTIFYING ENGINEEA may request that <br />any and all abraded areas be covered with extrudate. <br />Extrusion weld all cross seam tees to a minimum distance of four (41 <br />inches on each side of the tee. <br />g. Far extrusion welds, the edge of the top sheet shall be beveled by <br />grinding the edge of the sheet to approximately a 45 degree angle. <br />Extrusion welds can not be placed on previous extrusion welds. <br />C. Seaming Procedures <br />1. General Seaming Procedures <br />a. Areas to be seamed shall be cleaned and free of moisture, debris, or <br />any marking on the geomembrane. <br />b. Use a flat board, a conveyor belt, or similar hard surface directly under <br />the seam overlap to achieve proper support if required. <br />c. Cut tishmouths or wrinkles at the seam overlap along the ridge of the <br />wrinkle in order to achieve a flat overlap. The cut fishmouths or <br />wrinkles shall be seamed and any portion where the overlap is <br />inadequate shall then be patched with an oval or round patch of the <br />March 26, 1996 Section 02776.0 <br />01776.0-17 Geomembrane <br />Revision 4 <br />