Excavation of cave facilities
The board of Helsinki Region Environmental Services Authorities HSY chose Lemminkäinen Infra Oy as the prime contractor for the excavation of cave facilities of Blominmäki wastewater treatment plant on 12 June 2015.
Information on earthworks and excavation of the wastewater treatment plant
After the completion of earthworks, Lemminkäinen begun with tunnel excavation on November 2015. The excavation and reinforcement work continue until January 2018. The tunnel excavation of Mikkelä rock began in week 39 year 2015.
The working hours of the excavation works on the wastewater treatment plant for the aboveground facilities are:
- open excavation, weekdays between 7.00—17.00
- stone crushing, weekdays between 8–18
- drilling, sheeting, loading and stone transport, weekdays between 7–18 and (between 18–22 when under 55dB)
Working hours in the tunnels are as follows:
- blasting works, weekdays between 7–22 and on Saturdays, provided it is not a public holiday, between 9–18
- aggregate transport on weekdays (Mon-Fri) and during weekends.
Lemminkäinen complies with the safety regulations and authority instructions on all its constructions sites. The contractor apologizes for any inconvenience caused by the construction work for the residents of the area and strives to do its best to keep the disturbance to a minimum and as short-term as possible.
According to the contract plan, a total of ca. 910 000 cubic metres of rock is to be excavated via three tunnels by the end of 2017. To reduce the total amount of aggregate transports, a part of the excavated materials is stored temporarily and crushed at Blominmäki according to the environmental permit granted for the crushing plant. At the moment, there are only few deposit sites for crushed aggregates but aggregate materials are constantly needed for construction projects in the Helsinki Metropolitan Area.
Monitoring of blasting work
Before and after blasting work, Kalliotekniikka Consulting Engineers Oy carries out structural building inspections and vibroprotection of sensitive equipment on the properties of the nearby area. Additionally, monitoring measurements will be conducted with continuous vibrographs in the nearest buildings during the entire blasting work period. The allowed vibration limits are based on the norms set by the Ministry of Employment and the Economy for the field of blasting work and defined by external experts. The excavation progress and size of one-time detonations are regulated according to the gained measurement results so that no damage will occur.