Large scale soil remediation of a chlor alkali site in The Netherlands

Description of assignment

TAUW offered the owner of the site support during the whole remediation and redevelopment process, which including soil and groundwater investigation, drafting a remediation plan, designing a new sewer system, permitting, budgeting, tendering, contracting, supervision and transfer of property to third parties.

In 2006, a decision was made to decommission a chlorine plant in the Netherlands. The site is located next to a shipping channel. Having been in production for over 50 years, the soil, pavements, foundations and sewage system were heavily contaminated, primarily with liquid mercury. The contamination was detected and delineated using an XRF-analyzer and camera probes, in combination with conventional techniques like coring, monitoring wells and inspection trenches.

Before performing remediation, a variety of goals and techniques were evaluated to select the best remediation alternative. The considered techniques vary from excavation, pump & treat and immobilization, to capping, thermal treatment and soil washing. Based on multi-criteria analyses it was decided that excavating the first 2.5 m of the soil (48,000 m3) was the most cost-effective remediation alternative. The excavated soil had to be treated on-site using a mobile soil washer. Because there was no risk of mercury spreading, it was sufficient to monitor the groundwater.

Collaboration

TAUW played an important role in the process at the outset and during remediation. This included communication with all involved parties, risk assessment, mercury treatment pilots, and assistance with contracting and tendering. Furthermore, a comprehensive health and safety plan was drawn up.

The main remediation works were executed in 2010 and 2011. The last remaining mercury contamination was remediated in 2019. All work was supervised by TAUW. Because target levels  could not be reached with the on-site treatment plant, most of the excavated soil was transported to a controlled landfill. Underground utilities were demolished at the same time as the remediation, and a completely new sewer system was installed. To cope with the large amount of soil and groundwater data, TAUW’s Enterprise Geographic Information System (TEGSIS®) was used for continuous monitoring.

Result 

The location has now been successfully re-developed into a new industrial area that is mainly home to sustainable companies.