This Master’s thesis explores methods to reduce sediment filling in storm water basins in
order to facilitate maintenance. A study is conducted in a small residential area in Aalborg
that has a separated sewer system attached to a storm water basin. Tests are undertaken
to determine a effectiveness of gully pots for sediment reduction in storm water basin. It
is found that sediment samples from gully pots and the storm water basin contain similar
particle sizes. Furthermore, field measurements of the sediment build up in the gully pots
are carried out after a cleaning of the sewer system. It is concluded, that gully pots are
not sufficient to prevent sediment from filling the storm water basin, but they can prolong
the lifetime of the basin.
A pretreatment basin specialized in retaining particles by sedimentation is also examined.
The pretreatment basin is placed in front of the storm water basin. The purpose of the
pretreatment basin and storm water basin is to clean and retard the rainwater respectively,
before discharging it to the recipient. The pretreatment basin is studied using numerical
hydrodynamic models and experiments. On the basis hereof, a construction, that enhances
sedimentation in the pretreatment basin, is found. In order to make the pretreatment
basin easy to maintain it is drained between rain events, hence a strategy is determined
for the function of the basin during rain events. The strategy ensures good cleaning of the
rainwater at varying water levels in the basin.
Finally, the expenses for cleaning of a storm water basin versus cleaning of gully pots
and the maintenance of the pretreatment basin are estimated. This shows it is possible to
prolong the lifetime of storm water basins and thereby reduce expenses for maintenance
through implementation of the solutions determined in this thesis.
Niels