Start of construction for the Fröbel School
31.08.2020 – GBO Gemeinnützige Baugesellschaft Offenbach mbH has started work on a new building for the Fröbel School on Mühlheimer Strasse on behalf of the City of Offenbach by excavating, analyzing the soil and searching for explosive remnants of war.
The all-day school with a focus on mental and physical-motor development is designed for 150 children and young people and the same number of teachers and support staff. It should be ready for occupancy by the 2021/2022 school year and replace an old building in the city center that has become too small.
This is the first time that the real estate company GBO from the Stadtwerke Group has acted as the client for a public school building. This procedure was chosen in order to shorten time-consuming coordination processes in the municipal committees and thus speed up construction.
OPG takes over project realization
GBO has commissioned its sister company OPG Offenbacher Projektentwicklungsgesellschaft mbH with the realization of the project. OPG has already implemented countless multi-million euro construction projects for the city, from the stadium to the harbor school.
The total cost of the new Fröbelschule currently stands at around 30 million euros. They will be largely financed by GBO via the capital market. The City of Offenbach, as the school authority, will rent the property from GBO.
Optimal teaching and supervision conditions
According to Mayor and City Treasurer Peter Freier, he is pleased that construction can now begin. The inadequate spatial conditions in the old building of the Fröbelschule in Nordend would soon come to an end. Peter Freier: "With the new building on Mühlheimer Straße, we are creating optimal teaching and care conditions for children with disabilities."
The start of construction was preceded by an extensive, repeatedly optimized planning process in which all specialist departments and the school itself were involved at an early stage, in addition to the municipal utility companies GBO and OPG. Paul-Gerhard Weiß, Head of the City Planning and Schools Department: "In terms of planning, a special school is not comparable to a regular school. Great attention must be paid to the different impairments of the pupils and the best possible room facilities must be created for each case in order to achieve optimal learning success."
Preliminary work with extensive soil investigations
Four construction phases are planned for the new building, including the outdoor facilities. Because the subsoil of the 10,000 square meter site is problematic, the actual building construction will be preceded by a first, three-month construction phase involving extensive preliminary work in the form of extensive soil investigations. At the same time, the soil will be probed for remnants of war. There was an anti-aircraft position here during the Second World War.
Because an oxbow of the Main used to flow here, the subsoil of the 5,000 square meter school building consists of an inhomogeneous mixture of silty sand, clay layers and groundwater. The soil is only stable at a depth of eight meters. In the course of improving the subsoil, around 1,000 so-called vibrating tamping columns must therefore be driven eight meters deep into the ground for the foundation.
Due to its proximity to Mühlheimer Straße, securing the excavation pit is also complex. The pit walls cannot be anchored back on this side for space reasons. For this reason, a bored pile wall will be installed parallel to the road. This involves drilling solid concrete piles with a diameter of 88 centimetres into the ground and connecting them with concrete walls.
Swimming pool for therapeutic purposes and school sports
With the exception of the planned swimming pool, which will be accessible not only for therapy purposes but also for Offenbach school sports via a separate entrance, the school building will not have a basement. Large quantities of earth will have to be removed for the swimming pool. In addition, the underground construction requires extensive sealing due to the groundwater. In order to prevent deeper components from floating up during the construction work, the groundwater must be lowered by pumping for months.
For this reason, the groundwater level at the shopping center on the opposite side of the street on the site of the former Thorer fur finishing company is regularly checked at the same time in order to prevent contaminated groundwater from flowing from there towards the Fröbel school grounds.
Three construction phases
The pumped-out groundwater is fed into the sewer system. For ecological reasons and to relieve the municipal sewer system, the surface water will be collected in an underground, three-metre-deep, 20.6 x 5.5-metre rainwater retention basin with a capacity of 173 cubic meters and then throttled and fed into the Kuhmühlgraben, which is around 100 meters away.
The first construction phase of soil improvement will be immediately followed by foundation work up to the top edge of the base plate from November this year. This second phase should be completed by the beginning of 2021.
The building construction work, which is estimated to take twelve months, will then begin in a third construction phase. The Europe-wide tender for the turnkey construction of the school building from the top edge of the floor slab ran until August 24. The school building is to be built according to the plans of Frankfurt architects Mey in a conventional design with a ceramic clinker façade. After the school opens, the outdoor area will be designed in the fourth and final construction phase.
August 31, 2020