The Indonesian island of Bali is one of the world’s most well-known tourist destinations. It provides critical economic vitality to the province, with tourism accounting for more than 70% of its economy. Much of the island’s success is rooted in the natural beauty of its coastlines and forested mountain slopes. However, just 9km from the Ngurah Rai International Airport is the largest landfill in the country.

Sarbagita Regional Landfill’s traditional waste disposal practices—accepting upwards of 1.400 tons per day—led to the development of over-loaded mounds of waste. These mounds began to dominate the landscape.

Complicating matters, the 30-ha site was estimated to have less than two years of space left.

Health officials worried about the stability of the waste slopes and on the impact the exposed waste might have on local water. Tourism officials worried that the large footprint of the landfill, readily seen from the air by arriving visitors, would impact Bali’s reputation as a place of beauty.

To resolve these concerns, the Ministry of Public Works and Public Housing set forth on an ambitious plan to fully revitalize Sarbagita. Their vision was to create a modern waste-to-energy facility and, through the installation of a geosynthetic capping system, transform the large landfill space into green slopes.

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GREENING BALI’S LARGEST LANDFILL WITH GEOSYNTHETICS

The revitalization design of Bali’s largest landfill used Secugrid® 80/20 R6 geogrids for slope reinforcement and a Bentofix® X2 NSP3300 geosynthetic clay liner (GCL) for the cap. Both materials were engineered by the international geosynthetics manufacturing and design company NAUE.

The slopes greatly needed reinforcement to protect the waste from potential landslide.

The high-strength Secugrid® geogrid panels were extended back into the waste at key benches on the slope and in the middle slope zone. A mesh facing was installed on the face of the 10m-high prepared slopes and a tier of gabion baskets were installed at the slope toe to create the composite reinforcement system.

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Geomembranes and GCLs are typically used for landfill caps to prevent fluid migration into the landfill, thereby reducing or eliminating post-closure generation of leachate and the associated treatment costs. The cap is also designed to trap and properly vent the gases generated during decomposition of organic wastes. Similarly, the closure system can prevent the seep of any fluids from the refuse body to the landfi ll surface. Often, GCLs are added beneath the geomembrane to form a composite lining system. In this case the Ministry of Public Works and the designer decided to use a multi-component GCL and selected for the cap the polyethylene extruded coated Bentofix® X GCL, which directly suited the project’s performance goals. This composite variety of GCL features an extruded polyethylene coating on one of the highly durable outer geotextiles.

Desiccation behaviour of geosynthetic clay liners in a laboratory test
Desiccation behaviour of geosynthetic clay liners in a laboratory test, from NAUE. The coating on the Bentofix X GCLs has a dramatic and beneficial effect on performance.

The coating ensures a very high fiber pull-out resistance and increases the long-term internal shear strength of the GCL, which was a major benefit for the cap design on the slopes. Additionally, the coating increases the gas barrier performance of the GCL and further protects the bentonite core from desiccation or critical substances.

By fully encapsulating the landfill, the completed cap enables the safe and efficient restoration, revegetation, and possible reuse of the land. The total area of this first major phase of capping work was 5ha.

With this multi-geosynthetic design, Bali is restoring some of the hillside traditional beauty through a landfill modernization program. The work, which will be completed in 2019, exemplifies the province’s green engineering infrastructure goals.

Learn more about NAUE’s geosynthetics and projects around the world at www.naue.com.