The aim of the patrol is to check the filter well locations for sagging and loose or missing covers. For this purpose, the locations marked in the tables and overview maps must be visited and examined for possible damage to the well pipe or sagging at the GOK. The filter wells are to be inspected quarterly, semi-annually or monthly, in accordance with the determination. For the first patrol, a meaningful photo with location and surroundings must be taken of each filter well location. The work on site must be documented according to specifications and the photos must be labeled according to specifications. The filter well locations are not directly accessible by car and, due to the large number of locking systems at the opencast mines, are difficult to reach even via existing paths, so accessibility by foot must be observed.

Visual inspection of filter well locations, field exploration with GPS device, photographic and written documentation of the sites, approx. 3,050 sites in 25 different opencast mines, control in the cycles quarterly, semi-annually and annually