General
To ensure that complete water tightness is achieved, installation is carried out by our own personnel who have completed a minimum 12 months in-house intensive training programme. All matters relating to material specification and thicknesses are agreed prior to contract. All construction details are agreed prior to commencement of work.
Requirements in Respect of the Installation Surfaces
All surfaces on which the lining is to be installed must be prepared so that no damage to the lining is possible. The surface shall be free of all rocks, sticks, stones, roots, sharp objects or debris of any kind. The surface should provide a firm unyielding foundation for the membrane with no sudden, sharp or abrupt changes or breaks in gradient. No standing water or excess moisture shall be present. The surface must be constructed to allow the necessary compaction: 90% proctor with a surface tolerance of ±25mm for plastic materials, 80% proctor and ±50mm for rubber materials. If after inspection of the surface to be installed to, it is deemed unsuitable, sand blinding or a approved geotextile may be required as a protection layer.
Water Table
The water table level should be established and if higher than the base of the excavation, adequate drainage should be installed to prevent water pressure build-up below the liner.
Transport and Storage of the Sheet
The liner is provided in rolls or panels weighing up to 1.5 tonnes. On site is should be stored on a flat area, in the open.
Installation of Geomembranes
Before installation work begins, all surfaces to be lined must be approved by a Butyl Products Group Site Supervisor. The installation of the sheet is carried out in three steps:
- Positioning and unfolding of the rolls or panels.
- Welding of joints.
- Connections to concrete structures, pipe penetrations, sumps, anchor trenches etc.
The lining work is carried out in accordance with an agreed installation programme. On site progress of the installation work, as well as the climatic and working conditions are recorded, and on completion a layout plan is prepared to record the location and sizes of each roll or panel of geomembrane.
Positioning of Geomembrane Rolls / Panels
Positioning of individual panels / sheets is undertaken by machinery and/or hand. Special care is necessary not to damage the surface to be lined. After unrolling the geomembrane, panel overlaps are adjusted so that a suitable lap is achieved for the welding process. The geomembrane is checked before, during and after welding for any damage.
Environmental Conditions Limiting Geomembrane Works
No welding can be carried out where temperatures are below 0C or above 40C or in wet / damp conditions that will affect the integrity of the welding process. Deployment of geomembranes during high winds can become dangerous. Installation procedures may be ceased if wind speed exceeds 20mph.
Joining of Rolls / Panels
For Plastics: Wide wedge with open air channel, extrusion welding and hot air.
For Rubbers: The hot platen vulcanising system is employed. All welds are 100% inspected / tested.
Testing of the Weld Joints
The non-destructive test of each weld is carried out by our operatives. The test procedures are as follows:
- For wedge welding the joint is air pressure tested.
- For extrusion the joint is spark tested.
- Vulcanised joints are air lance or vacuum box tested.
For destructive testing, a check of the welded joints mechanical properties is carried out by taking samples of a joint from installation in progress and checking the welds’ bonding strengths in tensile and peel.
Construction Details
We enclose illustrations of our standard fixing details. we will recommend designs for any special detail that a project may require and submit them for approval by the project designers prior to commencement on site.
Protective Cover
All materials that are to be placed on top of the liner will be inspected. If deemed unsuitable, a non-woven geotextile may be recommended as a protective layer. Installation of cover materials should be carried out after acceptance of the inspected and tested liner. Any cover materials should be placed with a suitable machine (excavator bucket, front loader) always pushing out and running on at least 500mm thickness of the deposited material and not travelling directly on the lining. The cover material shall be spread in a manner to ensure that the liner maintains good contact with the contours of the ground and no over-tensioning or bridging of the material occurs. Should the cover placement operation cause damage to the liner, our engineers should be informed immediately. They will carry out any necessary repairs and advise on actions to prevent recurrence.
Contamination Protection Gas / Hydrocarbons (Gas Membranes Only)
Inspection and testing would be carried out as detailed above for all gas / hydrocarbon installations protection but given the need for follow on trades to access all areas of the installed geomembrane, the contractor should maintain some form of quality control routing to ensure the geomembrane will not be damaged or compromised. Access is permitted for machinery following discussions on best practises. In addition to the requirements detailed above for the ‘install guidelines for geomebranes’, gas / hydrocarbon projects would need to take into consideration the following:-
- Geocomposites and components need to be correctly installed to ensure that gas venting design will work.
- All gas venting, components, materials and extraction equipment should be installed by competent persons and following design criteria based on the acceptable configuration for the type of containment or concentrations. Components should be fit for purpose and connected and sealed to venting mats or outlet set / boxes. Components should be installed by trained lining operatives although suitably trained bricklayers and ground workers may install, often prior to geomembrane works commencing but always following manufacturers guidelines.
- Gas venting layout plans should be consulted prior to installation. Alteration can be made due to a lift pit, internal wall, stairwell, door or window being in direct line of a particular venting run: specialist advice should be sought prior to altering this detail.
Positioning of Geocomposite (Gas Membranes Only)
Geocomposite can be installed into a 30mm recessed grip to provide a flush finish with the formation. It may also be installed directly on to the prepared surface following consideration for sufficient concrete cover. The composite can also be buried within the formation, therefore eliminating detailed preparation and interphase at installation times.
Perimeter Sealing (Gas Membranes Only)
Perimeter sealing can be carried out by jointing the DPC with welding or gas adhesive tapes or sealing to the external primed perimeter beam or provide an upstand. Sealing to internal walls, sumps, thickening and lift shafts can also be sealed in this way. All porous surfaces should be primed and gas tape applied within the specified timeframe. Penetration through the geomembrane should be sealed by either using welding techniques, gas resistant tapes and purpose built shrouds and this would include columns, wind posts, dock levellers and pop-up pipe details. Gas tape sealing should be covered, i.e loaded, within a reasonable timeframe to prevent ambient conditions affecting its short term performance.
Drawings
The client shall provide a large scale construction drawing for the project, so that Butyl Products Group can indicate a proposed panel layout for all phases of the project.
Health & Safety – General Statement of Policy
Our policy is to provide and maintain safe and healthy working conditions, equipment and systems of work for all our employees and to provide such information, training and supervision as needed for this purpose. we also accept our responsibility for the health and safety of other people that may be affected by our activities. The general statement of policy is supported by 17 sections of detail in the full Health & Safety Policy which is available on request.
Risk Assessment and Method Statements
Site specific Risk Assessments and Method Statements are prepared for each contract.
