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11. SOILS IN CONTACT WITH GEOSYNTHETICS

The CQA procedures defined in this section are only intended to ensure that the installation of these materials does not damage the geomembrane and other geosynthetics. Additional CQA procedures may be necessary to ensure that systems built with these materials will be constructed in such a way as to ensure proper performance.

Motorized equipment will not be allowed directly on the geosynthetics. However, All Terrain Vehicles with tire pressures less than about 55 kPa are acceptable provided they do not turn sharply, or accelerate or brake suddenly. They must not be operated on a liner containing wrinkles that can be folded over.

Drainage and protective cover soils should be placed at the coolest time of the day when there is minimum wrinkling in the geomembrane.

Soil will not be dumped directly on the geosynthetics. It will be dumped on an associated haul road and then spread onto the geosynthetics.

The soil must be spread in such a way that wrinkles in the geomembrane are dispersed and not folded over. Extreme wrinkles (those that may fold over) will be cut and seamed flat.

Soil should be spread over the edge of seams, not such that it can penetrate under the loose flap of a seam and cause a peeling force.

The geomembrane must be fully supported by the subgrade at the time of placing the cover soil.

Cover and subgrade soil should not contain stones or rocks or other items that might damage the geomembrane.

Equipment will not be allowed over the geosynthetics until the minimum specified thickness of cover soil has been placed. In the absence of such figures in the Project Specifications the soil shall be a minimum of 50 cm thick for low pressure tracked equipment, and 1 m thick for wheeled vehicles.

Soil on slopes will be placed from the bottom of the slope upwards.

It may be appropriate to require an electrical leak location survey on the geomembrane, after placement of the cover soil. Experience has shown that about 65% of leaks in a geomembrane are caused during cover soil placement. At this stage all installation damage will probably have been done, but it will still be practical to expose and repair the geomembrane.