FTSP INC.
OUR SOLUTIONS
Our Solutions to minimize the damage caused by floods in Semarang
INFILTRATION SYSTEM
Groundwater injection in the perfect solution for the Banger polder. The rainfall runoff that is collected in the sewer system is transported to the lowest areas of the Banger polder. There the water will be pumped to the water table that is located underneath the clay and silt ground layers. The depth of the sand a gravel layers vary in depth below the surface (according to a subsurface profile published in: ‘A Physical Study of the Effect of Groundwater Salinity on the Compressibility of the Semarang-Demak Aquitard, Java
island’. A schematisation of how the groundwater injection works, is presented in figure 7. An injection pipe is installed deeply into the groundwater reservoir. The rainfall runoff water is then pumped into the groundwater reservoir. The water will then re-saturate the ground. This way the depletion of the groundwater levels under Semarang can be counter acted to a certain extend. However, the biggest gain in the battle against the land subsidence, can be obtained by introducing restrictions for the local industries. By limiting the amount of groundwater that de local industry is allowed to withdraw, this problem can be prevented instead of counteracted.
SEWER SYSTEM
To solve the problems during the raining season a new above-ground sewer system has been designed. First the Banger polder has been divided into smaller areas. For each area has been calculated how much rain falls into that specific area. After mapping out how much rain falls in each area, the rainfall has been distributed over the different sewer paths in between the areas.
After the quantities have been determined a new sewerage system has been designed. This new sewerage system is based on the current sewerage system, but with this new system, the water can be directed to specific point in the Banger polder. At these points there are pumpstations that will pump the water back into the soil until the groundwater level. By pumping the water back to the groundwater level, the team hopes to accomplish a delay of the subsidence in Semarang while also solve the problems during the raining season.