Rainwater infiltration using DRAINMAX tunnels in Selm
| Project | LAFP Police Academy, container complex, Im Sundern 1, 59379 Selm – completed in 2026 |
| Client | LAFP, Selm site |
| Application | Rainwater infiltration |
| Product | INTEWA DRAINMAX® Tunnel |
Description
For a temporary container facility at the LAFP police academy in Selm, the rainwater was to be infiltrated directly onto the site. A particular constraint: according to the soil survey, only a few areas of the construction site were suitable for infiltration. A compact underground infiltration trench using the INTEWA DRAINMAX® tunnel system was therefore designed for the available location.
The system handles the rainwater runoff from 1,323 m² of connected area: 537 m² of roof, 294 m² of paving and 492 m² of water-bound traffic and pathway surfaces. The design was carried out in accordance with DWA-A 138-1 using KOSTRA-DWD-2020 data for Selm. The fine sand was assumed to have a kf value of 2 × 10⁻⁵ m/s.
Two parallel rows of tunnels were installed, comprising a total of ten DRAINMAX tunnel elements. The effective storage volume, including the gravel fill, is 27 m³. Following completion, the specialist contractor Peter Rudolf Garten- und Landschaftsbau particularly highlighted the quick and easy installation and rated the tunnel system more highly than traditional box systems in terms of installation.
Planning
| Parameter | Specification / Value |
|---|---|
| System | INTEWA DRAINMAX® Tunnel |
| Number of DRAINMAX tunnels | 10 × DM-T-1600-M/60 |
| Start/end caps | 4 (2 × DM-T-100-S/60, 2 × DM-T-100-E/60) |
| Configuration | 2 rows of tunnels |
| Effective storage volume | 27 m³ including gravel fill / edging |
| System dimensions | approx. 12.63 × 3.70 × 1.00 m (L × W × H) |
| Connected area | 1,323 m² gross / 1,033.5 m² effective for drainage |
| Substrate | Fine sand |
| Permeability coefficient kf | 2 × 10⁻⁵ m/s |
| Design rainfall | 90 min, 45.20 l/(s·ha), return period 5 years |
| Calculated drainage time | 6.18 h |
Feedback from the installation:
“Installation was very quick and easy. In our view, the DRAINMAX tunnel system is much easier to install than traditional box systems.” – Feedback in essence from Peter Rudolf, gardening and landscaping, following installation on 28 August 2026 |