WALO USA is a specialist in the field of hydraulic asphalt engineering, particularly in providing impermeable barrier systems for the construction and renovation of dam-faces, dam-cores, reservoirs, pumped storage and equalizing reservoirs, artificial lakes, irrigation systems, canals, river banks, landfill sites and coastal protection and flood alleviation schemes.

WALO® has now been in the business of providing hydraulic asphaltic barrier systems for the containment of water all over the world for more than 70 years. The company has focused on the constant improvement of processes such as horizontal and vertical laying of bituminous seals. By using the most modern machinery, WALO® has also produced results in the construction of landfill seal systems, biotopes, snow reservoirs and parks.

WALO® provides a complete service to its customers, both at home and overseas – from initial feasibility studies to designing, manufacturing and installing suitable materials to match their individual requirements for sealing systems in every kind of hydraulic application.

Reservoir Lining

WALO’s Dense Asphaltic Concrete (DAC) lining system is perfect for lining reservoirs, canals and irrigation systems as it is non-toxic, impermeable, very strong and still flexible enough to withstand the stress of large volumes of water being pumped in and out every day. 

Large ships travelling though canals cause powerful waves but canals lined with DAC can withstand the pressure they create. Long side slopes in these containment systems are not a problem either, as WALO® can line slope lengths of 130 yards or more using specially designed machines which have no need for regular joints – often a major problem for barrier systems.

Landfill Lining

WALO® has created a Dense Asphaltic Concrete (DAC) impermeable landfill barrier system, which is impermeable to methane and leachate, found in most solid waste landfill deposits. 

Leachate drainage from landfill cells is always a major concern for waste operators, who are under increasing pressure to prioritise environmental considerations. The application of DAC means that landfill sites can now safely house very toxic waste. This is because the resulting contained landfill cannot leach through the impermeable barrier into the groundwater. Many potential sites, such as old quarries, are dismissed out of hand as unsuitable for waste treatment as they have very steep walls. However, landfill designers and engineers looking for practical solutions for landfill lining find that DAC is very stable on slopes, even those as steep as 34º, which means even sites with very steep walls can be used for landfill. Thus more space can be created for contained landfill while still providing great protection for the environment. Very strong – yet very flexible – DAC is only 13.4 inches thick and provides decades of impermeable sealing service in the waste treatment industry.

Dam Face Lining

As well as providing Dense Asphaltic Concrete (DAC) linings to the waste industry, WALO® also provides hydraulic asphalt concrete impermeable barrier systems to the water and power industries, lining dams of every size from relatively small projects to major hydro electric plants. 

For example, many of Switzerland’s major power stations have large equalising reservoirs which have been lined by WALO® using exclusively designed machines built in the company’s own workshops. WALO’s DAC lining system provides a strong, flexible, non-toxic lining, which is thin enough to flex under extreme pressure without cracking, while being totally safe for human, animal and marine life. These factors make it perfect for water storage.

Other Applications

In addition to lining dam faces and cores, reservoirs, canals and landfill sites, Dense Asphaltic Concrete (DAC) is a very versatile product, useful in all kinds  of containment lining systems where an impermeable barrier is needed. 

For over 50 years DAC has been successfully used. WALO is at the forefront of technological advances in hydraulic technology, which has seen DAC being used for sealing sea defences, coastal groins, irrigation systems, river banks and even for creating snow reservoirs in ski resorts for the production of artificial snow.


We completed UHPFRC paving of a total of 4,600 yards or 580,000 sq feet on two parallel interstate highway bridges and achieved a breakthrough in fast UHPFRC Layer Paving under heavy traffic.

The overlay of 1.6 inches in most parts and 2.0 inches in the part of the girder close to the piers was completed on each bridge in 30 days.

This very fast execution was made possible by the use of a casting machine specially developed for the placement of fresh UHPFRC over varying widths and levels at the correct height, plus the use of a customized on-site mixing plant.

Dumpers, filled at our UHPFRC mixing facility, supplied the machine regularly and just in time with fresh UHPFRC. The UHPFRC had to comply with the requirements of tensile strain hardening material properties.

In addition, the fresh UHPFRC had to show thixotropic behavior as it was to be paved on slopes of up to 7%.

The whole project was a great success due to the scientific and technical collaboration between WALO®, FEDRO (clients & engineers) MCS (EPFL Prof. Brühwiler) and the material supplier.

Our unique selling proposition in teamwork with Scientists are UHPC-Systems based on evaluation, formulation, production on-site and paving machine technology.

Enhanced Techniques

DAC – at a glance


What is DAC?
DAC consists of high-grade aggregates, sands, fillers and bitumen and if needed, additives.


Where is it used?
DAC is used as an artificial sealing system in hydraulic engineering works. It is proven as an ideal solution for lining dams, central dam cores, reservoirs, canals, ponds, tailing lagoons and waste disposal sites.


What special qualities make DAC an ideal lining system?

  • is quick to lay (outputs of over 54,000 sq feet can be achieved on a daily basis).
  • is totally impermeable against very high pressure of water and liquids.
  • withstands large and rapid changes of water levels and temperature.
  • is relatively thin.
  • remains very flexible, even under extreme pressure.
  • is extremely stable, even on steep slopes (slopes up to 150 m long and gradients in excess of 1:1.6 can be achieved.
  • in some circumstances DAC can be placed nearly vertical adjacent to walls.
  • is very robust, so withstands traffic, rock falls or ice abrasion immediately after placing without the need for additional protection.
  • is environmentally friendly and non-toxic.
  • is resistant to ageing with proven longevity.
  • forms a totally impermeable barrier with no joints.
  • approved by Regulatory Bodies around the world.
Engineering Solutions

WALO® has world leading, established, technical engineering knowledge and the necessary modern specialist plant and equipment to provide a Dense Asphaltic Concrete (DAC) impermeable barrier system anywhere and for any situation. WALO’s DAC lining system, made from clean aggregates, fillers, sand and bitumen is installed using specialised laying and compaction techniques. Due to its high density, DAC is extremely resistant to chemical attack, while being very strong and still flexible.

Our Laboratory

For over sixty years WALO® has built on the services of its own laboratory to ensure consistent quality of both building materials and end products. The laboratory is engaged in the development and production of formulations as well as in quality control for the production of ready-mixed materials. The company also monitors application or installation work. WALO’s central Laboratory and its mobile laboratories are accredited test stations for bituminous building materials and surfaces, sealing coats for dam and landfill construction, fresh concrete and concrete, primary and secondary building materials and flooring systems.

nach oben