Polypropylene - Cold Temperature Installation
LOCATION: Northwest Territories TIMEFRAME: Winter-Spring 2001 & 2002 SCOPE OF WORK: Supply, fabricate & install 32,000m2 of 40 mil polypropylene for collection dam PROJECT PARTNERS: Owners: BHP Diamond Mine Engineer: EBA Engineering Consultants Ltd. Contractor: Layfield Environmental
Project Name: EKATI Diamond Mine, Misery Site Dams
Owner: BHP Diamond Mine
Locaton: Canadian Arctic
Engineer: EBA Engineering Consultants Ltd., Edmonton, Alberta
Materials: 40 mil Polyproylene geomembrane, GCL, non-woven geotextile
During the winter and spring months of 2001 and 2002, Layfield was involved in the supply, fabrication, delivery and installation of over 32,000m2 of 40 mil polypropylene for the King Pond Dam, Waste Rock Dam and Seepage Collection Dam. The 40 mil unsupported polypropylene (UPP) geomembrane was being used in the cores of two 15-meter high rock filled dams. Layfield was awarded the project in late 2000 and by January 2001, Layfield had fabricated enough 40 mil UPP to start phase one of the project, which was, located 300 km north of Yellowknife, NWT. In addition to the 40 mil UPP which was the primary geomembrane on the upstream side of the dam, a GCL was used as a secondary liner and was placed on the downstream side of the dam facing. The project was installed in two phases between January 2001 and 2002.
The construction called for a frozen key trench that was constructed at the Misery Site of the EKATI Diamond Mine. The dam was designed to be a zero discharge mine water runoff collection dam. The engineer specified a Layfield 40 mil Polyproplyene liner based on its durability, excellent cold temperature properties and the ability to install the material in extreme sub zero temperatures in the Canadian Arctic. In addition to the polypropylene and the GCL, a heavy weight non-woven LP16 geotextile was used as an upstream cushion.
The 40 mil UPP geomembrane was selected as the primary liner due to its flexibility and ease of handling in extremely cold temperatures. Layfield fabricated custom panels that ranged in size of 330 m2 to 3300 m2 base on the location of deployment in the dam core.
Layfield was the only geomembrane installation company that did not submit an alternate geomembrane option from the original design. Layfield was very comfortable with the design that utilized the UPP. Layfield is the largest manufacture and fabricators of thin gauge flexible geomembrane liners in Canada. Layfield prefabrication all of 40 mil UPP into custom panels for the rock filled dams. The ability to prefabricate the 40 mil UPP into custom panels from roll stock under controlled conditions resulted in a decrease of field welding under adverse winter conditions. The 40 mil UPP was installed ambient temperature below –30°C during various stages of the installation of the key trench and upper sections of the dam.
When temperature dropped below –40°C, installation of the UPP geomembrane was halted to ensure that no damage occurred to the geomembrane. Construction was resumed once the Engineer on site felt the geomembrane could be installed without sacrificing the integrity of the geomembrane.
Monitoring of the dam has taken place since the initial installation and there has been no seepage observed at the lower level of the dam.