Dewatering is considered one of the most critical activities in infrastructure projects as it requires a proper set up and continuous maintenance throughout the duration of the project. Any interruption to the system will lead to the stoppage of construction activities.

One of the projects in Qatar was the Infrastructure Priority Package IPP at Education City/Qatar Foundation where dewatering was a major activity because the excavation for storm and sewer lines was four to five meters below water level. During the construction process, a dewatering system was set by installing 6” electrical suction pumps into drilled boreholes two meters lower than the trench level. As a result, the team had to find a way to drain the underground water. After investigating the surrounding area of the project, a drainage system was found related to the Public Work Authority of Qatar. After obtaining all the required permits, flexible hoses were connected for drainage and thus the underground water level was reduced and the construction activities were carried out in phases.. After some time, the system to which it was draining became oversaturated due to other adjacent projects who were draining their underground water to the same system. No new excavations could begin until the problem was solved. It was a big challenge since there was no float in the project schedule and couldn’t afford any delays. The only alternative was to build a temporary retention pond (a 20m x 20m was the only area that could be used), and this was located next to the excavation area. The idea of placing the pond close to the excavation site was to create a circulation process from excavation to the pond and vice versa. At the beginning, four boreholes of 400mm diameter were drilled at a depth of two meters lower than the excavation level, but the volume of water from the dewatering was larger than the pond volume and the seepage through boreholes was not enough. Therefore, the number of boreholes was increased to 12 and the process was completed. Maintaining this operation had allowed for the reduction of the underground water level so that the excavation was able to be completed. The storm and sewer line was then successfully erected, and the system was kept operational until there was enough height for backfilling above the pipes to prevent any uplift force caused by the underground water.

After completion of the works, the pumps were gradually removed and then subsequently, the retention pond. Facing such challenges during the construction process gave the team a lot of practical experience and information to share with colleagues.