Groundwater remediation of Dutch Railways site at Crailoo

In the past, wooden railway sleepers were treated with creosote at the Dutch Railways (NS) site in Crailoo. This has resulted in severe creosote contamination of the soil, down to a depth of up to 50 metres. NS wishes to remediate the contaminated soil at this site.Remediation was necessary to prevent any spreading of the contamination and ensure that local groundwater can continue to be used safely.

Remediation process
The groundwater was treated on-site (in situ) to ensure that operational activities could continue as normal. An assessment of the remediation options showed that In-Situ Chemical Oxidation (ISCO) using the Perozone© system and extraction using a high-pressure vacuum system would optimise the remediation yield.Checks and measurements were performed during the remediation process to maximise removal of the contaminated soil. The remediation work was completed according to schedule, and the competent authorities approved the results achieved.

Witteveen+Bos performed the following activities:

• Groundwater modelling to assess the spread of contamination and to identify effective measures to reduce contamination
• Design of remediation work and elaboration of the measures in an RAW-compliant contract
• Elaboration of tendering guidelines, including MEAT criteria and supervision of the tender procedure
• Environmental supervision and advice during the remediation process
• Preparation of an evaluation report on the remediation work