Geomembranes Welded for Large Tailings Ponds in Kazakhstan

Author: Silke Landtwing, Manager Corporate Communications, Leister Switzerland

Things to know about Kazakhstan

Kazakhstan has an area of 2'724'900 km² / 1'052'084 mi² and is the ninth largest country in the world. The country stretches from the Caspian Sea in the west to the Altai Mountains on its eastern border with China and Russia. Its largest metropolis, Almaty, is an important commercial hub. Moreover, Kazakhstan is one of the richest countries in the world when it comes to raw materials. Thus, oil and gas production and mining are the country's main sources of income.

44 percent of the total area of Kazakhstan is covered by sand and gravel deserts, 28.5 percent by steppes and forest-steppes.

As you can guess from the thumbnail of this blog post, the tailings ponds of the gold mines are located in the Kazakh steppe. Since there is usually strong winds blowing here, the workers weigh down the geomembranes with sandbags before welding.

Leister’s distributor, RIKAZ, in Kazakhstan

Leister’s distributor, RIKAZ, is a multi-brand trading and service company founded in 2010. RIKAZ offers Leister’s professional equipment for plastic welding, modern geosynthetic waterproofing materials and innovative polymer technologies for industrial and civil engineering in Kazakhstan.

RIKAZ is very successful in Kazakhstan through its distribution of Leister equipment for plastic welding and the matching geomembranes. This is because Leister's high-quality automatic welding machines, heat guns and testing equipment are in great demand in Kazakhstan for civil engineering, especially in mining and quarrying.

Kazakhaltyn commissions RIKAZ to build huge tailings ponds

Kazakhaltyn Mining-Metallurgical Concern JSC (KZAL) is one of the oldest companies in Kazakhstan's gold industry and is known for mining and processing gold ores. The history of the company begins in 1932, after the discovery of gold reserves in the northern part of Kazakhstan. During its heyday from 1970 to 1980, annual production here was six to seven t / 225,055 oz of gold. Over the past 80 years, the company has produced approximately 350 t / 11,252,761 oz of gold.

When large tailings ponds were to be built for gold mines near Aksu, Zholyimbet and Bestobe, RIKAZ received an order from Kazakhaltyn to seal them with geomembranes. This was a major order: The total area of the tailings ponds was approximately 150 ha/370.66 ac. In addition to the sale and delivery of the required Leister equipment and massive quantities of geomembranes, the contract also included laying and welding the geomembranes.

What are Settling Ponds and What are They Used for?

In the gold mines, gold particles are washed out of the soil. Pollutants, such as lead, arsenic, cadmium or mercury, are released in the process. The water contaminated with these pollutants is collected in so-called settling ponds. By sealing the settling ponds with tightly welded geomembranes, the polluted water is isolated and no pollutants enter the soil or groundwater. The contaminated water from the settling ponds is filtered and then reused. The pollutants left on the ground after filtering, usually trapped in sludge, are then professionally isolated and disposed of.

More than 150 ha or 370.66 ac of geomembranes installed

RIKAZ has installed geomembranes for the soils in the tailings ponds totalling over 150 ha / 370.66 ac. This corresponds to an area of 210 football fields.

The geomembranes used were 1-2 mm (or 39-79 mil thick) AGRU brand material. The geomembranes were mainly overlap welds with the Leister’s GEOSTAR G7 automatic welding machine. The GEOSTAR G7 is equipped with the Leister Quality System (LQS for short) where important welding parameters like speed, temperature and joining force, as well as the geographical coordinates of the weld, are seamlessly recorded via GPS and documented in a log. This means that RIKAZ can provide proof of the weld quality.

Quality Assurance Through Weld Seam Inspection

As mentioned in the previous section, the geomembranes for the settling ponds were overlap welded.

This creates a test channel. This is filled with air after welding in order to check and guarantee the tightness of the weld seam with the Leister compressed air tester.

Strong Wind and High Temperature Fluctuations

According to Vadim Shostik, Sales Manager at Leister Technologies AG, it was technically challenging to weld the 1-2 mm or 39-79 mil thin membrane correctly: "Especially the difficult environmental conditions like strong steppe winds and big changes in temperature. They were a big challenge." Under such conditions, it is crucial to carefully match the welding parameters (temperature, speed and joining force) in order to achieve a high-quality weld.

GEO-Technical Sales Engineer, Eddie Weiser, Leister Technologies AG, travelled to Kazakhstan to advise RIKAZ on the selection of Leister automatic welding machines and to assist in setting the correct welding parameters on the GEOSTAR G7 and GEOSTAR G5. In order to guarantee a tight weld, welding must be carried out in the so-called welding window. Read more in the technical article "LQS for Quality Improvement in Geomembrane Projects" by Eddie Weiser on Leister-Stories.

LQS Improves the Quality in Geomembrane Projects

The welding work was made even more difficult by the drastic changes in temperature. In summer, the mercury in the Kazakh steppe rises up to 40°C / 104 °F during the day. At night, the temperature hovers around freezing. Such temperature fluctuations have an effect on the quality of the weld seam. This is because when it is cold at night, the geomembrane contracts, which puts about twice as much stress on the weld seam as when it expands in the heat of the day.

In order to ensure a long-term, tightly weld seam, most of the welding work has to be completed at night during the summer. For this purpose, the GEOSTAR automatic welding machines had to be provisionally equipped with special LED lamps, which illuminated the welding zone in the dark.

Unfortunately, anyone who thinks that the welders had it easier in the winter is mistaken. In winter, the temperature here is -20°C to -30°C or (-4°F to -22°F) at night and still rises above freezing during the day. In addition, the onset of winter in this region is often very sudden, so quite different from what we know in Switzerland, for example.

Which Leister Equipment was Used?

RIKAZ employees were welding details such as this T-joint with Leister’s WELDPLAST S2 manual extrusion welder.

Here is a list of Leister’s automatic welders, extrusion welders, heat guns, and testing equipment that RIKAZ has used to seal the settling ponds:

Welding machines

• ASTRO (This automatic welding machine is no longer in production, but is still used successfully in many places. Its successor is the GEOSTAR G7).
• COMET
• TWINNY T
• GEOSTAR G5
• GEOSTAR G7
• GEOSTAR G7 LQS

Leister manual extruder

• WELDPLAST S2
• WELDPLAST S4 (GEO version) is used to extrude welding wire with a diameter of 5 mm (0.2 in.).

Leister heat gun (hand-held unit)

• TRIAC ST

Leister testing equipment

• EXAMO 300F for peel, pull and shear force testing
• COUPON CUTTER 500 for punching test pieces conforming to standards
• Compressed air tester or leak tester to test the weld seams durability

RIKAZ and Leister have been working together with a successful partnership since 2013

Vadim Shostik sums it up: "RIKAZ is very successful in Kazakhstan and is considered a reliable partner throughout Central Asia. As far as our cooperation is concerned, RIKAZ is a one-stop shop: Service, technical support, user training, repair services and spare parts. What Makes our Partnership Great RIKAZ actively helps us test new developments. RIKAZ recently tested a new set of rollers for the Leister TWINNY T5 and TWINNY T7 automatic welding machines. This was done under rough conditions. The feedback has been positive, by the way."

We’d like to thank RIKAZ for a successful partnership and for their great cooperation. We look forward to completing many other exciting projects together in the future.