Environmentally Certified Ground Decontamination of Kvarnbyterrassen in Mölndal

Kvarnbyterrassen covers approximately 35,000 m² and is situated barely 1 km to the east of Mölndals Centrum, to the south of Gothenburg. For 180 years, this area has been the site of prolonged industrial activity. Prior to the decontamination work, the area was classed as one of the ten most-polluted areas within the Västra Götaland region.

The ground has now been decontaminated and Bonava (NCC Boende) has built 400 residential apartments on sloping ground overlooking Mölndal. The site is adjacent to a conservation-protected urban area and the Mölndalsån river. Sustainability has been a watchword that has permeated the project. The project has now received the world’s first CEEQUAL certification since the new stricter standards came into force.

Ceequal certification

CEEQUAL is a British certification system that assesses the sustainability work undertaken in ground and construction projects. It evaluates how well sustainability issues in a project have been handled, from the idea stage through to completion. A couple of years ago, NCC became the first in Sweden to work with CEEQUAL, when working together with Trafikverket on the E4 Rotebro project.

The certification of Kvarnbyterrassen is the first in the world to meet CEEQUAL’s new, more stringent requirements, including an assessment of the project’s overall sustainability strategy. This evaluates how work in the project has been performed in a wider context – looking at the surrounding community and not just at one individual project. The new requirements take into account the economic, social and environmental effects on a community level, in order to assess how the project contributes to a sustainable society. As a result, NCC has become the first in the world to receive CEEQUAL’s new “Sustainability Strategy & Performance Assessment” certification.

A CEEQUAL certification can be awarded for all or parts of a project’s phases. The certification for Kvarnbyterrassen includes all phases of the project: planning, design and production.

Decontamination

The planning for the coming decontamination work and building of housing began during 2007 and, in April 2011, the site decontamination work began. The implementation of the project was preceded by a long and intensive period that included land surveys, a series of inventories, risk assessment and remedial investigations, as well as the demolition of buildings.

The decontamination work involved the removal of 98 % of phthalate pollutants and 80 % of lead pollutants from the area.

The main principle was to sort the mass operatively by means of on-site sifting. The sifting process made it possible for 27,800 tonnes of the excavated mass to be reused within the project. This resulted in a significant reduction in transporting materials to and from the site.

Sustainability analysis

In parallel with the planning stage and execution, the decontamination project has also been used as a case study for a number of research and development projects. The overall aim is to increase knowledge of how to design sustainable decontamination projects in the future. Kvarnbyterrassen has also been used as a case study in SCORE, which is a sustainability tool developed by the FRIST skills centre at Chalmers University of Technology, where NCC has a leading role.

As part of an academic thesis, a comparative sustainability analysis of four decontamination alternatives was performed. It showed that the principle of on-site sifting that was applied at Kvarnbyterrassen was the most sustainable option. Amongst other things, it was possible to significantly reduce the need for transportation to and from the site by reusing the excavated material on-site. Transport was the primary concern of nearby residents – a social aspect of sustainability that was successfully managed. The level of resource efficiency achieved gave the project an environmental sustainability. 3D modelling had also optimised where the ground level would be, so as to be able to also manage remaining material in a resource-efficient manner.

The economic sustainability of the project has been evaluated as part of a cost-benefit analysis. This showed that the chosen alternative was the most advantageous, both for the project and socio-economically.