- Mass balance to be achieved
Soil remediation is based on site-specific guideline requirements that follow the Swedish Environmental Protection Agency’s guidelines and methodology. Local soil remediation and reuse of excavated materials on site is prioritized. In 2019, excavation work was mainly conducted in conjunction with road construction and detailed planning work, resulting in amounts of excavated materials being relatively small. In 2019 preparatory work and pilot studies were also carried out for the upcoming on-site remediation of Kolkajen. In 2020, this land is scheduled for remediation work and thus, pollution caused by the former gas plant at the site will be removed. The total area remediated to date amounts to 346,950 m², which is almost equivalent to 50 football pitches. The mass balance is about 41 per cent. The reason excavated materials cannot be reused is frequently due to the fact that there is excess mass, technical quality is poor, or that pollution levels are too high. See table 3.5.
Excavation work occasionally requires dewatering of ground water which needs to be purified before it is released into Lilla Värtan. Due to its relocation, the City Development Administration’s own water treatment plant was not operational in 2019. Instead, drainage water was purified with the help of contractors or managed externally. In 2019, the City Development Administration, in consultation with the Environmental and Health Administration and Stockholm Vatten och Avfall, produced new benchmarks that apply to drainage water that will arise in Stockholm Royal Seaport to further contribute to improved water quality in Lilla Värtan. In 2019, approximately 380 000 m3 of contaminated water was purified by contractors, an amount that would fill 152 Olympic swimming pools.
Table 3.5 Overview of remediated soil, mass balance and drainage water in public open spaces
Remediation of the Hjorthagen cavern car park is partially completed. All hydrocarbons have been absorbed by means of, among other things, archaeas (ancient microorganisms). Residual substances such as PFAS and PFOS are being removed via a carbon filter in conjunction with two storage compartments being emptied of water. The remediation is expected to be completed by 2021.
1 Area of remediated soil to 2016.
2 Purified drainage water in Stockholm Royal Seaport’s water purification project.
3 Up to March 2015.
4 March-December 2015.