sustainability case study

Stormwater design

Name & Location

Capgemini / Spie
Ratingen, Germany





Tenant Area

10,950 m²

Project Details

Within the category Sustainable Sites LEED has two Credits pertaining to storm water design. The aim of the Credits is to reduce the amount of stormwater directed to the municipal sewer and encourage the infiltration and retention of rainwater onsite. Infiltration of stormwater helps to restore groundwater resources and avoids unnecessary overflows in sewers. It also contributes towards the elimination of pollution in storm water runoff.

At this particular project site, as opposed to using the conventional stormwater sewer, the municipality provided a system of off-site stormwater treatment facilities. The system consisted of two sand filter basins and an extended wet detention pond, in which stormwater was cleaned and partly allowed to replenish the groundwater reserve. To be able to use the stormwater treatment system the project site was limited by the water authorities to a maximum of 15 l/(s x ha) discharge. Owing to this relatively small amount, the project site had to install an onsite retention sewer to buffer its stormwater outlet and avoid any overload of the filter facilities.

The onsite underground retention sewer is located next to the building’s underground garage. It has a diameter off 0.8m and is 70m long. The objective of the two LEED Credits were fulfilled and the project team was even able to achieve exemplary level, which was awarded with an extra point. Most of the project site’s stormwater run-off was collected onsite and filtered off-site at the described basins. Overload of municipal stormwater sewers and pollution of natural water bodies were avoided, while providing habitat for plants and animals.