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Date

2021-2025

Client

Province of North Holland

Location

Castricum

Status

Finished

Long-term soil remediation in a residential area

We all want the soil around us to be clean. However, occasionally action needs to be taken to remediate (i.e. clean) contaminated soil. Soil may be contaminated with volatile organic compounds (VOCs), for example, making remediation essential. This also applies when the soil presents other risks to health or to nature. And action also needs to be taken when there is the risk of the pollutants spreading further, as was the case in Castricum, specifically on the Duin en Bosch estate. When it was discovered that the soil on the site of a former psychiatric hospital was contaminated, the Province of North Holland asked Mourik to prevent further spread of the pollution through the groundwater. In 2021, we started on urgent in-situ soil remediation, focusing especially on the location where a dry cleaning facility had once been operating. The site is located next to a residential area and on the grounds of a residential mental health facility, meaning we needed to pay special attention to those living and working close by.

In-situ soil remediation using biodegradation

We applied a combination of remediation technologies to reduce the level of soil contamination. First, we excavated part of the soil on the grounds of the mental health facility and transported it off the site for processing elsewhere. This was the source of the contamination. Stage two was a pilot for in-situ remediation of the remaining contamination in the soil and groundwater. We have our own laboratory for analyses and we develop our own soil remediation and water treatment units. In this particular case, specialists from Orvion were also involved, providing independent verification at multiple points along the process. Orvion also specializes in biological solutions for soil contamination.


The final step in this process was full-scale soil remediation, which involved three phases of four months each, with interim measurements and adjustments. The process we chose for this is called ‘stimulated biodegradation’. This involves providing the groundwater under the soil with nutrients and good bacteria so that nature can do its work, biologically degrading the contamination, ‘digesting’ it as it were. With this long-term remediation method, we extract the contaminated groundwater from filters and then pump this into the remediation unit where we add the nutrients and bacteria. We then allow the treated water to infiltrate into the soil to disperse throughout the area. One of the advantages of biodegradation is that this method ensures the permanent destruction of the contaminants, meaning the remediation process does not need to be repeated. That’s a big plus in a residential area.

Stakeholder management and in-situ soil remediation

The location of the contaminated soil presented an additional challenge. A mental health facility is located on the west side of the site and there is a residential area to the east. This meant that we were carrying out this soil remediation project almost literally in the backyard of local residents. What’s more, residents of the mental health facility grow their own vegetables on the grounds. With such a situation, everyone on the team naturally must stay on their toes, extra attention needs to be paid to communicating with those living and working in the vicinity, and our people need to be accessible for answering questions. To keep local residents informed at all times and to keep disruption and nuisance to a minimum, we maintained intensive contact with all stakeholders, including the local authorities and staff operating the mental health facility. This we arranged through information meetings and newsletters, for example.

Monitoring the in-situ process

A project like this has many specific challenges. In addition to the complexity presented by the contamination, we need to have the right know-how of the required remediation methods – like in-situ soil remediation and biodegradation in this case. Stakeholder management is another good example, as well as having the combination of expertise required to offer an all-in-one soil remediation solution: environmental technology, test facilities, design and engineering, construction and operation of the remediation unit, laboratory work, and process management. And that’s where Mourik’s versatility is often the decisive factor. For situations like this where urgent remediation is required, this versatility is even more valuable and appreciated. We met the deadline by a wide margin. Thanks to our approach with its long-term results, the soil is once again completely free of contamination and local residents, including residents of the mental health facility, can once again enjoy a green neighborhood!

Contact

Leendert Groenewegen Van der Weiden

Leendert Groenewegen Van der Weiden

Operational Manager Environmental Techniques
Mourik Infra B.V. Voorstraat 67
2964 AJ Groot-Ammers
THE NETHERLANDS

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