Problem

The problem of the subsoil of Utrecht is that several pollutions from different sources are mixed due to time. In total 180 million m3 groundwater is polluted with VOC's. Due to the mixing of the pollutions a single case approach is impossible. The total area of the subsoil that is polluted is approximately 700 Ha. The total area of redevelopment within Utrecht is 90 Ha and is mainly developed by closed and historical buildings, with wooden floors etc.

Location

In the Utrecht central station area the deeper groundwater will be remediated by a combination of ATES (Aquifer Thermal Heat Storage) and biological natural attenuation. This perfect opportunity for synergie between redevelopment, groundwater remediation, and energy storage (reduction of CO2) has resulted in an area-oriented approach.

Aim

The proposal has been made to set up a ATESt location to determine the impact of ATES on contamination. The transport and degradation of the contamination will be measured around a newly to be built ATES system at this test location using different methods. First, the impact of ATES on contamination can then be determined and, secondly, monitoring can be optimised.

Planning

The contamination concentration and the bacterial population will be measured regularly in the sources to be able to follow degradation in time. A more practical approach is to equip the sources with passive samplers that measure the average contamination concentration during the injection stage. An (average) concentration difference can be determined by equipping the sources with new samplers during the extraction stage and, therefore, the degradation rate can also be determined. A distinction will be made between concentration change due to degradation and due to dilution by using isotope analysis.

The impact of ATES on the redox condition in the water-carrying layer will be determined by installing observation wells with filters at different depths and sampling these regularly or by equipping them with passive samplers. The spread of heat/cold can also be determined if fibreglass cables are also installed when installing these observation wells.

Results

Expected in September 2012

Factsheet

Film: Utrecht - Beste Duurzaamheidsproject