The Simongan weir constructed in 1870’s, is a flood diversion weir made of bricks masonry. The weir is still utilized as not only a diversion weir but also an intake weir of municipal water and environmental flow to the Semarang river. This 130-year aged structure has been damaged through its lifespan and as a result, subsidence and cracks stand out on the structural surface at present. Thus it was proposed to reconstruct it as a gate-weir. However, the government of Indonesia decided to rehabilitate and conserve the Simongan weir as a heritage of Indonesian civil engineering considering its historical value and cultural landscape/primal scene of the Semarang city.
Prior to establishing a rehabilitation plan of the weir, the then design philosophy was reproduced by means of repair records, original river hydraulic conditions and results of weir body inspections. Through the study, it was verified that the then structure is structurally stable and hydraulically reasonable but it is necessary a rehabilitation work to maintain the stability of the weir based on the present river and weir conditions.
The rehabilitation plan was established to maintain the original weir shape, view and functions, to reserve the most of the original material such as then bricks and stone blocks and also to satisfy the present structural design criteria following the original design concepts. That is a repair of damaged portions and a reproduce of original design condition, i.e. reproduction of the efficiency of drain system and the hydraulic phenomenon on the weir.