The soil under the former Enka industrial site in Ede (NL) has become contaminated during the decades of industrial activities. The contaminants concerned included heavy metals, chlorophenols and chlorinated solvents. The Enka site is now being redeveloped into an attractive residential area. To enable the redevelopment, an extensive soil remediation was carried out. Subsequently, a start was made with the remediation of the groundwater. The area to be remediated was approximately 300 meters long and 200 meters wide.
In close cooperation with Vink Aannemingsbedrijf B.V. the site has now been successfully remediated. Harold van Buren, manager at Vink: “For this project, we needed the specialist knowledge of HMVT. After a few good meetings, we had a soled step-by-step plan with ultimately a beautiful result. This required good coordination. It was the task of HMVT to extract and treat the groundwater. We took care of the infiltration of the treated water. This process went very smoothly”.
Design and aim of the groundwater remediation
The approach to groundwater remediation on the ENKA site consisted of the extraction of contaminated groundwater and the subsequent infiltration of the treated groundwater. The original remediation plan envisaged for the installation of 2 extraction wells from which a water flow with a flow rate of 50 m3/hour would be extracted. HMVT proposed an optimization on this plan. The approach we suggested provides for the extraction of 30 extraction wells at different depth levels in the soil. This allowed the contaminated groundwater to be removed from the soil in a much more efficient manner. The water flow could thus also be limited to 40 m3/hour. After treatment the extracted water was infiltrated on-site via 8 infiltration wells.
The purpose of the groundwater remediation on the ENKA site is to reduce the contamination in such a way that the groundwater quality improves significantly and at the same time no further spreading of the contamination occurs (= ‘stable situation’).
Remediation and redevelopment cleverly coordinated
The redevelopment and remediation of the Enka site have been close coordinated. During the earthworks for the remediation of the top meters of the soil by Vink B.V, the various system for the groundwater remediation were installed. The wells and pipes for groundwater remediation are all located public spaces. After this process was completed it was possible to start building the houses. The water treatment plant was also located in an area that was to be redeveloped in the latest phase. All these measures enabled the redevelopment of the area to be started quickly, not restricted by the groundwater remediation.
Treatment of the groundwater
The treatment of the extracted groundwater was conducted on the basis of a precipitation coagulation technology. In this process the first step is to adjust the acidity of the extracted groundwater so that the heavy metals precipitate. Subsequently adding a flocculant creates “flakes” in which the contaminants are concentrated. The flakes settle in basins of the system.
The treated water was led back into the soil for infiltration via specifically designed sand filters. In this manner a circulation system was created in the soil in which the groundwater quality was improved during the remediation.
The groundwater remediation has been carried out and completed in the predicted 5 years. Currently, monitored of the groundwater is conducted to verify whether a ‘stable situation’ in groundwater has been created. The results look so promising that dismantling of the water treatment plant has now been started.
During the groundwater remediation the entire Enka site was redeveloped while retaining industrial heritage quality and hundreds of new homes. The clever combination of remediation and redevelopment has resulted in a beautiful new neighborhood for the municipality of Ede.