In three stages, we built stormwater drains and a flooding area for Mustapuro, together with the required equipment and structures. Mustapuro’s main brook and side branch cross below the Itäväylä in three bridge drums, the smallest and largest of which were in poor condition. They were replaced with one larger drum, and the third, retained drum was rinsed. In addition, we built two new drums along the Itäväylä, which improved flood protection in the area. Floods were also prepared for by strengthening the Itäväylä roadside with wood piles, building a flood plain and reshaping the western side branch. When the new arrangements were ready, the drums and piping to be decommissioned were filled in.
Mustapuro is a valuable trout stream, and so the trout spawning time was taken into account in the construction and schedules. In addition, special attention was paid to the treatment of the water discharged into the stream during work. Trees and bushes were also planted and meadows established.
The two bridges to be renovated were the northern bridge over Sahaajakatu, which is an 85 metre long and 19 metre wide, continuous, three-span reinforced-concrete hollow slab bridge, and the southern bridge over the Itäväylä across Siilitie, which is a 70 metre long and 21 metre wide, continuous, reinforced-concrete box girder bridge.
We replaced the edge beams of both bridges and their handrails as well as the southern overhang on the northern bridge. The surfaces of the 1,120 m² deck of the southern bridge and 900 m² deck of the northern one were jet-cleaned with water, mouldings were made and all the surface structures were replaced. Below the bridges, the front walls of the earth supports were jet-cleaned and shotcreted. This was challenging on the Sahaajankatu bridge due to the large ground pressure on the embankment of the bridge, and therefore the work progressed in small sections at a time. All the concrete structures below both bridges were blast-cleaned and coated. Cracks were grouted, damage was patched and the bearings were serviced. In addition, the drainage of the bridges was renovated.
The repair of the bridges proceeded in three stages, which enabled the flow of traffic on the bridges and the streets below to go on without interruption throughout the work. Working on one of the capital’s most important thoroughfares brought special demands with it: On the Itäväylä, the amount of traffic is 35,000 vehicles per day, and the traffic is also busy under the bridges, where around 10,000 vehicles pass every day. In addition, there are plenty of pedestrians and cyclists in the area, especially on the bridge over Siilitie, which is located next to the Siilitie underground station.
In this challenging project, we also proceeded while keeping the nearby underground line in mind. Careful planning and professional execution were highlighted when, for example, the sheet piling of the support structures of the trenches and the piling work belonging to the bottom reinforcement were done in the vicinity of the underground tracks. The basic repair of the Sahaajankatu bridge was carried out in such a way that the car wash located under the bridge could continue to operate without interruption.
The Mustanpuro part of the contract was completed in summer 2023. The southern bridge over Siilitie and the northern Sahaajankatu overpass were completed during autumn 2023. The total value of the project was approximately 6 million euros, and the customer was the City of Helsinki.
