Data model based carbon footprint calculation guided the design solutions of Ruskeasuo depot

Ruskeasuo depot is one of the major infrastructure projects in the Helsinki Metropolitan Area, and both Skanska and Sweco have extensive responsibilities regarding its low-carbon solutions. Skanska utilised the carbon footprint calculation tool developed by Sweco for comparing its alternatives.

The Ruskeasuo depot project is part of the development plan of tram depots, the purpose of which is to prepare for the growth of the tram transport fleet in the Helsinki Metropolitan Area as well as the needs of the new light rails. Skanska has total responsibility for the project, in which it will build a tram and bus depot for 100 trams and 200 buses, comprising an area of nearly three football fields. The development stage of the depot, to be completed in 2024, was guided by the BREEAM Excellent environmental certificate and the Carbon Neutral Helsinki 2035 goal.

“However, the carbon neutrality goal of Helsinki was advanced by five years during the project, and we had to find new measures to complement those we had already agreed on,” says Skanska’s Project Engineering Manager Teemu Saarinen. A list with nearly 90 measures was collected through on-site workshops, comprising feasible emission reduction measures, and the best-suited measures were selected for implementation. “We were able to refine the plans so that the depot’s functionality has improved while the CO2 emissions have been reduced with more than 30 different measures.”

Skanska is executing the extensive project worth more than EUR 100 million through the combined forces of its infrastructure, building services and office buildings business units. Sweco also has extensive responsibilities in the project, for example in the areas of structural, energy and building safety engineering, fire safety planning and data model coordination.

Calculation of energy goals to support BREEAM certification

The BREEAM certification ensures that demanding energy and material efficiency goals were set for the depot project from the start. “Instead of district heating and cooling, geothermal heat was selected as the heating and cooling system of the depot,” says Sweco’s Project Manager of HVAC technology Jesse Kurkinen.

Due to safety reasons, the feasibility study supported using metal pipes instead of plastic and composite pipes for HVAC technology. “Safety in the depot area requires that the pipes are grounded in an extensive area,” Kurkinen explains. As cleaning and maintenance services take place in the depot area round the clock, it has to be possible to control all technology as needed and where needed. The ventilation and water services equipment, for example, can be controlled in different areas at different rates through an automated system. “The office premises and staff facilities are also equipped with carbon dioxide and moisture measurement sensors.”

The depot’s LED lighting is controlled space-specifically using a DALI system. “The lighting will be adjusted based on the premises’ rate of use and with presence and motion sensors,” says Sweco’s Project Engineer Ricardo Weibel Avendano. All employee parking spaces can be equipped with charging stations for electric cars, and the same will also be installed for each of the more than 200 bus spaces. A water recycling system conserving clean water has been connected to the washing equipment of buses and trams. “Thanks to this system, clean water is only used for rinsing.”

Basement facilities made with low-carbon concrete

Based on the emission calculation carried out in spring 2021, most of the Metropolitan Area Transport Ltd’s CO2 emissions come from fleet procurement and the construction of rail infrastructure and depots. To combat this, the Betoroc recycled concrete crush has been used at the depot, and the facades have been covered with spruce cladding. Lujabetoni’s low-carbon Luja-Vähähiilibetoni is another factor in reducing emissions.

“We have used the low-carbon concrete for the basement ceiling and walls and nearly all of the footings, and some has also been used for the columns,” says Mikko Huhtala, Sweco’s Project Manager of structural engineering. The depot will be built using a hybrid frame that combines concrete elements and cast-in-situ components. Element construction helps shorten the delivery schedule, and post-tensioned structures allow for long enough span distance. “The curving rail areas make it necessary to build load-bearing structures also in less than optimal locations.”

Sweco experts have also taken part in the research and quality assurance of Lujabetoni’s low-carbon concrete, for example by performing compressive strength tests on the test pieces of the concrete used for Nauvontie. “We also carried out the condition survey of the tram depot’s stone wall,” says Sweco Expert Noora Anttalainen.

Data model based calculation of carbon footprint sped up the comparisons

Many of the depot’s structural choices were grounded on a data model based comparison of carbon footprint, using a calculation method of the Ministry of the Environment. This was implemented flexibly during the structural engineering stage, with the help of an agile tool developed by Sweco. “A data model based carbon footprint calculation is a convenient tool for comparing the various engineering solutions, since it quickly shows whether a certain structural decision will take the project in the right direction,” Saarinen says.

After the carbon footprint comparisons, the raised floors that were originally designed to have a steel structure were decided to be implemented as concrete slabs cast on top of a crushed rock bed. Concrete usage was also optimised. “which reduced the demand for concrete,” says Sweco’s Chief Structural Engineer Kimmo Fabrin.

The data model based carbon footprint calculation was introduced in the project in early 2021, when the decisions regarding frame solutions had been made, but Skanska’s Saarinen believes that the tool could be very useful during projects’ early stages, too. “Calculating a project’s carbon footprint is already an important part of our work, and all tools facilitating this work during the planning stages are very welcome.”

Sweco is constantly developing new solutions for its customers’ needs, and a new data model based cost accounting tool will be published in the first half of 2023.

Images: Skanska ja Arkkitehtityöhuone APRT Oy

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