The Snowdonian Stwlan buttress dam near Blaenau Ffestiniog is a pumped storage hydroelectric power station. Constructed in 1963, the concrete dam utilized a unique double wedge joint between each buttress. These joints were never sealed properly creating seasonal freeze/thaw damage that ultimately lead to worsening spall damage of the structure itself. In 2000, manufacturers were invited to test their products in an extended two year trial. After multiple evaluations, Thinfilm Technology was selected to apply 100% solids coating that would eventually cover 2,050 sq.m. of concrete surface.