GEOSYNTHETICS AND WELDED GAS RESISTANT MEMBRANE INSTALLATION QUALITY PLAN

Transcription

1 GEOSYNTHETICS AND WELDED GAS RESISTANT MEMBRANE INSTALLATION QUALITY PLAN SEL Environmental Ltd Stormer Hill Works Mill Street Tottington Bury BL8 4AT Page 1 of 14

2 INDEX INTRODUCTION 1.0 MATERIAL DELIVERY 2.0 SUB GRADE PREPARATION 3.0 HANDLING AND PLACEMENT 4.0 PREPARATION FOR GEOMEMBRANE INSTALLATION 5.0 METHOD OF INSTALLATION 6.0 GEOMEMBRANE SEAMING 7.0 SEAM TESTING GEOMEMBRANES 8.0 REPAIR PROCEDURES 9.0 HAND OVER Page 2 of 14

3 CONSTRUCTION QUALITY ASSURANCE INTRODUCTION This manual addresses the Quality Control Program developed and utilised by SEL s Membrane Installation Personnel to assure the quality of workmanship and the installation integrity of geosynthetic systems. SEL recognises that careful and specific documentation for the installation is required to substantiate this Quality Control Program. Page 3 of 14

4 1.0 MATERIAL DELIVERY An SEL representative shall be present, whenever possible, to observe and assist in material delivery, unloading and storage on site. Their duties will include the following:- Check the material delivered for damage and shall mark any damaged areas and record on QA sheet SELQA.001. Ensure the area designated for storage is clean and fit for the purpose. Collect and check data including roll batch numbers, roll size and delivery vehicle details and record on SEL QA Sheet SELQA.001. Page 4 of 14

5 2.0 SUB - GRADE PREPARATION Earth Works The Client s earthwork contractor or groundworker shall be responsible for preparing to the correct formation level and maintaining the subgrade in a condition suitable for installation of the geosynthetics unless specifically agreed otherwise. In cases where no site specific formation guidelines exist, the following general guidelines shall be followed. Surfaces to be lined shall be smooth and free of debris, roots, and angular or sharp rocks and protrusions. All fill shall consist of well-graded material, free of deleterious material that may cause damage to the geosynthetics. The subgrade shall be compacted in accordance with design specifications. The Client s Earthwork Contractor or groundworker shall protect the subgrade from desiccation, flooding, and freezing. Protection, if required, may consist of a thin plastic protective cover ( or other material as approved by the Engineer ) installed over the completed subgrade until such time as the installation of the geosynthetic system begins. On completion of the subgrade preparation, SEL s supervisor will issue to the client / main contractor a subgrade acceptance form SELQA.002. Any repairs to the subgrade are to remain the responsibility of the earthworks contractor or groundworker. Liner Anchorage System (if applicable) The anchor trench shall be excavated by the Earthwork Contractor to the levels and widths shown on the design drawings prior to the placement of the geosynthetics. Corners in the anchor trench shall be slightly rounded to minimise sharp bends in the synthetics Page 5 of 14

6 3.0 Handling and Placement All geosynthetics shall be handled in a manner to ensure they are not damaged. The following special handling requirements shall be adhered to : On slopes, the geosynthetics shall be secured in the anchor trench and then dispensed down the slope in such a manner as to continually keep the materials in sufficient tension to minimise folds and wrinkles. In presence of wind, all geosynthetics shall be ballasted with sandbags, each being tied together if necessary. Geosynthetics shall be cut using an approved cutter. If the material is being cut in situ, special care must be taken to protect other materials from damage. Care shall be taken not to trap stones or excessive dust that could damage the components. Page 6 of 14

7 4.0 Preparation for Geomembrane Installation Panel Layout Layout drawings shall be produced and recorded on QA sheet SELQA.003 to indicate the panel configuration and general location of seams for the project. Identification Each panel used for the installation shall be given a numeric or alpha - numeric identifier. This panel identification number shall related on QA Sheet SELQA.003 to a manufacturing roll number that identifies the resin type, batch number, and date of manufacture. Page 7 of 14

8 5.0 Method of Installation The method and equipment used to install membranes must not damage the geomembrane or the supporting subgrade surface. No personnel working on the geomembrane will wear shoes that can damage the geomembrane or engage in actions which could result in damage to the geomembrane. Temporary anchoring, which will not damage the membrane, will be carried out with the use of sand filled hessian bags should prevailing weather conditions dictate. The geomembrane will be installed in a manner to minimise wrinkles. Page 8 of 14

9 6.0 Geomembrane Seaming Each seam shall be indicated on QA Sheet SELQA.003. Seaming information including seam number, welder ID, test pressures and test duration will be maintained on QA sheet SELQA.004. Personnel All personnel performing seaming operations shall be trained in the operation of specific seaming equipment being used and will qualify by successfully welding a test seam. An SEL foreman will provide direct supervision of the seaming operations to verify proper welding procedures are followed. Hot air wedge welding consists of placing a heated wedge, mounted on a self propelled unit, between two over - lapped sheets such that the surface of both sheets are heated above the membranes melting point. After being heated by the wedge, the overlapped panels pass through a set of pre - set pressure rollers which compress the two sheets together to form the weld. The fusion welder is equipped with a temperature readout device which continuously monitors the temperature of the wedge. Extrusion Welding Extrusion welding consists of introducing molten resin along the edge of the seam of the two overlapping sheets to be welded. Pre heating of laps and the molten polymer causes some of the material of each sheet to melt resulting in a homogeneous bond between the molten weld bead and the surfaces of the sheets. Hot Air Welding. In areas inaccessible to the previous noted forms of welding or where site conditions dictate, overlap welds may be affected with the use of proprietary hot air guns and hand rollers. The equipment used must be specifically designed for the purpose with multi-stage variable adjustment on both heat and blower settings. The overlapped membrane is heated to softening point and fused Page 9 of 14

10 together using the hand rollers to form a homogeneous fusion welded joint over a minimum width of 50mm. Weather Conditions Many factors, such as the geomembrane temperature, humidity, wind, precipitation, etc., can affect the integrity of seams and must be taken into account when deciding whether or not welding should proceed. Test seams, are required prior to daily production seaming to determine if the weather conditions will effect SEL s ability to produce quality seams. Additional non - destructive and destructive testing of production seam substantiate the decision made on any day given. Page 10 of 14

11 7.0 SEAM TESTING - GEOMEMBRANES Hot Air Wedge Welds The welded seam created by a hot air wedge welder is composed of a primary seam and a secondary track that creates an unwelded channel. This unwelded channel allows the completed weld to be tested by inflating the sealed channel with air to a predetermined pressure usually 2 bar for 5 minutes duration and observing the stability of the pressurised channel over time. Extrusion Welds If requested prior to membrane installation, spark testing can be used for non - destructive testing of extrusion welds. After seam preparation, but prior to welding, a length of copper wire can be embedded into the seam over its entire length, after the completed weld has cooled the suitably adjusted spark tester ( 10 Kv / mm ) shall be passed over the extruded weld, any sparks observed indicate a seam failure, these should be marked on the seam. For repair at a later stage and then retested. Hot Air Welded Joints Hot air welded joints may be tested using the Air Lance Method. A compressed air source will deliver 55 psi minimum to a 5mm nozzle. The nozzle will be directed to the lip of the field seam in a near perpendicular direction to the length of the field seam. The nozzle will be held 100mm maximum from the seam and traversed at a rate not exceeding 12m per minute. Any loose flaps of 3mm or greater will require repair. Destructive Testing The purpose of destructive testing is to determine and evaluate seam strength. These tests require direct sampling and thus subsequent patching. Therefore, destructive testing should be held to a minimum to reduce the amount of repairs to the geomembrane. Page 11 of 14

12 Destructive test samples shall be performed randomly, and only if specified in writing prior to membrane installations commencing. The specification should include the required frequency of sampling. Destructive samples should be taken and tested as soon as possible after the seams are welded ( the same day ), in order to detect possible problems in a timely manner. The project QA Co-ordinator will observe all destructive testing and record date, time, seam number, location, and test results on SEL Destructive Testing Form. All destructive test locations with pass / fail designation will be marked on the liner with permanent white markers. Page 12 of 14

13 8.0 Repair Procedures Any portion of the geomembrane or geomembrane seam showing a flaw, or failing a destructive or non - destructive test shall be repaired. Several procedures exist for repair and the decision as to the appropriate repair procedure shall be made by SEL s Project Supervisor. Procedures available for repair : Patching - used to repair large holes, tears, and destructive sample locations. All patches shall extend at least 150 mm beyond the edges of the of the defect. Grinding and Welding - used to repair sections of extruded fillet seams. Spot Welding - used to repair small tears, pinholes, or other minor localised flaws. Capping - used to repair lengths of failed extrusion or fusion welded seams. Removal of a bad seam and replacement with a strip of new material seamed into place. Repairs of whichever nature will be recorded on QA sheet SELQA.005 Page 13 of 14

14 9.0 HAND OVER ON COMPLETION Areas of completed installation will be inspected by S.E.L. s representative in conjunction with the clients representative or QA Co-ordinator. Following a successful inspection, QA sheet SELQA.006 will be completed and handed to the Client. Page 14 of 14