Geomembrane-lined artificial lake secures snowmaking at Borșa Olympic ski slope

Overview

As part of the development of an Olympic ski slope in Borșa resort, Maramureș County, Romania, an artificial water storage lake was constructed. The wider project included the Olympic ski slope itself, along with artificial snowmaking and lighting systems. The lake was designed to ensure a sufficient water reserve for operating the snow installation during the ski season.

The lake is located on the right side of the slope, when viewed in the direction of descent, in the upper third of the ski slope, approximately 900 m downstream from the upper gondola station, at an elevation of 1,320 m.

Challenge

The lake site posed a few engineering and logistical challenges. The terrain is a slope with a northeast orientation and an average inclination of 25 percent. The excavation was extensive, with roughly 60 percent of the lake volume formed through cut operations. The average excavation depth was about 9 m, with a reduced depth of around 4 m at the downstream end.

The earth accumulation dam constructed to form the lake had a total height of 9 m, comprising 8 m of water elevation and 1 m of safety guard. The width at the crest measured 5 meters in the fill area. The lake geometry is relatively rectangular, with crest dimensions of 81 by 73 m and base dimensions of 47 by 23 m.

Approximately 30,000 m³ of locally excavated material were used in constructing the downstream dam body. The completed reservoir has a total capacity of 22,000 m³ of water and covers a surface area exceeding 5,000 m². Additional challenges included the high-altitude location, lack of access to roads, and seasonal weather conditions.

The geosynthetic installation took place within a very tight 14-day execution window. Adverse weather was a constant obstacle: negative temperatures, sleet, snow, strong winds, and blizzards interrupted installation work and placed heavy demands on the installation team.

Solution

The waterproofing of the lake was achieved through a multi-layer geosynthetic system installed on both the slopes and the base. On the slopes, the system comprised:

• a 25 cm gravel layer over the existing substrate, providing drainage and support,

• an 800 g/m² protective geotextile,

• a 2 mm double-sided rough GSE^® HD geomembrane,

• a 500 g/m² protective geotextile,

• a 10 cm gravel layer over the upper geotextile, supported by a triaxial geogrid and 10 cm high geocells.

At the base of the lake, the waterproofing included:

• a 25 cm gravel layer over the foundation soil for drainage and support,

• an 800 g/m² protective geotextile,

• a 2 mm double-sided rough GSE HD geomembrane.

This geosynthetic configuration ensures robust impermeability and protection of the GSE HD geomembrane, while also maintaining drainage and stability under load. The inclusion of triaxial geogrid and geocells provided confinement and reinforcement for the upper gravel layer, enhancing slope protection.

Despite adverse conditions, the installation team from Inoveco Expert completed the geosynthetic work within the planned 14 calendar days. The successful outcome was attributed to the team’s extensive experience, with more than 20 years of expertise in similar geosynthetic projects.

The artificial lake at Borșa now secures a reliable 22,000 m³ water reservoir for snowmaking operations, ensuring the functionality of the Olympic ski slope and supporting the development of winter sports infrastructure in Maramureș County.