Land remediation and bulk materials management
After more than a century of industrial activity and gas production on site, soil and groundwater in Stockholm Royal Seaport need to be remediated before construction can commence. To reduce the number of transports associated with these measures, the project strives to remediate as much masses as possible on-site, known as in-situ remediation, and to manage excavated materials locally.
2023 Highlight:
Key figures:
- About one-third of the area has been remediated.
- To date, 1,050,000 tons of excavated materials have been reused. In 2023, the reuse rate was 80 per cent.
Land remediation
To understand the extent of the contamination and the levels to which the soil needs to be remediated, an environmental and health risk assessment is conducted. Subsequently, land remediation is carried out to a level that ensures soil poses no risk to human health or the environment. This also reduces environmental impact on surrounding aquatic environments.
Land remediation in Kolkajen–Ropsten began in 2019 to address contaminants such as tar and benzene, which were residues from gas production that was previously conducted at the site. The clay layer, which can be up to 15 metres thick, has been both remediated and strengthened. Below the clay lies a layer of friction soil, moraine, treated with persulfate to break down tar. Lime cement columns have been used to stabilise the clay. Regular sampling is conducted to ensure that contaminants remain at acceptable levels. In 2023, about 35,000 m3 of clay and 100,000 m3 of moraine were remediated. Land remediation began between the existing buildings in Gasverket East to remove old tar pipelines, a task carried out with considerable caution to protect the buildings of special cultural interest in Gasverket.
The expansion of Saltkajen in Värtahamnen is underway, partly to create a new land area in the water. For this project, 27,000 m3 of dredged masses and parts of the old quay are being reused as fill material.
Land remediation in Kolkajen
Bulk materials management
Various types of masses arise during site preparation works, such as soil, clay, and crushed rock, which need to be managed. The goal is to manage and remediate masses locally as much as possible. To facilitate this process, a local was established in 2018. The centre helps to reduce the amount of transports and manages excavated rock and contaminated masses. Sorting materials that are contaminated or of geotechnically poorer quality contributes to a higher degree of reuse. A rock crushing facility enables the reuse of remediated bulk materials directly on-site. In 2023, dry screening was complemented with a wet screening facility to improve the ability to sort soft excavation materials. All sorting takes place inside a hall building, reducing dust and noise.
The City of Stockholm collaborates with Stockholm Region and the Extended Metro Administration to receive and reuse bulk materials. To date, the Mass Consolidation Centre has handled 1,050,000 tons of rock and excavated materials, of which 540,000 tons have come from various construction sites in Stockholm Royal Seaport.
In 2023, 530,000 tons of rock and excavated materials were managed, the majority of which came from work to expand the Stockholm metro. Of all reusable material, 82 per cent has been reused in Stockholm Royal Seaport, while the remainder is stored for future needs. Throughout the lifetime of the project, 42 per cent of all excavated and rock materials have been reused, although in 2023 this figure increased to more than 80 per cent.
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Achievements for 3. Land remediation and bulk materials management
3.1 Reduce amounts of waste
- To date 29% of the area has been remediated.
- 1,050,000 tons of excavated materials have been reused in Stockholm Royal Seaport, which means that approximately 70,200 round-trip journeys have been avoided.
- The amount of construction waste in new construction varies greatly between the developers; from 25 to 158 kg/m² GFA. The average is 47 kg/m².
- in Stockholm Royal Seaport is 88 kg per person/year 2023.
- Pop-up Reuse has so far been visited by 39,000 people, since its launch in 2017. In 2023, it was visited by approximately 7,400 people, 20,700 items were given new owners, thus 3.1 tonnes have been recycled.