Laying of drains and sewers of all materials and nominal widths, in particular also > DN 1,200 and in depths > 5 m with the associated structures in open construction under aggravated conditions. 

Quality mark holders of group AK1 meet the requirements of groups AK2 and AK3.

Laying of drains and sewers of all materials in nominal widths ≤ DN 1,200 in open construction with the associated structures down to a depth of 5 m.

Execution area AK2 is a constituent part of execution area AK1.

Laying of drains and sewers of all materials in nominal widths ≤ DN 250 in open construction with the associated structures down to a depth of 3 m.

Execution area AK3 is a constituent part of execution areas AK2 and AK1.