Virumgaard. Retention basin on football field
Virumgård. Basin system with lake, underground attenuation basin and emergency overflow to playing field.
Virumgård land was parcelled out in around 1980 and provided with a separate sewer system.
The rainwater from the separate sewer system is passed via a sludge trap and an oilseparator to a wet basin. This basin is established as a low-bottomed, recreational lake overgrown with reeds. There is an outlet from the lake via a water brake to a stormwater drain which passes the rainwater out into Lyngby Lake. The lake has a storage volume of 1,450 m3. In the event of heavier rain, an overflow is activated to an underground attenuation basin (tunnel basin), made up of concrete elements from Perstrup, with drainage to a stormwater sewer. When the underground attenuation basin is full, the water level in the wet basin rises, at which point the rainwater is discharged via an emergency overflow to a nearby grassy area which is used as a playing field. The playing field acts as a dry basin. The local football club has permission to use this area for games on the understanding that the playing field will be flooded in the event of extremely heavy rain.
Niels Drisdal Hansen: "Trouble with the football people cannot be avoided entirely because the field is frequently flooded and it is not possible to play on it immediately after emptying. The football people are themselves responsible for maintenance of the playing field. Lyngby-Taarbæk Forsyningen is called after rainfall if there are any irregularities, e.g. if the drain pump stops working."
Finance
The lake (the wet basin) with an overflow to the playing field was constructed during the development of the site. The tunnel basin was constructed in 2008 when the basin volume of the lake was reduced when a new residential care facility was erected. This project also involved pipe rupture of a downstream stormwater sewer to a larger dimension as the sewer was increased to 45 l/s. Therefore, it is slightly difficult to provide information on establishment costs.
Operation and maintenance
Reeds are harvested in September every year on account of birds. The charges for this amount to DKK 80,000 -100,000 per year.
Catchment
Residential area of 14.8 ha (13.5 red. ha.)
Average annual precipitation: 650 mm
Average annual surface runoff: 75,000 m3
Hydrological reduction factor: 0.9
Initial loss: 0.6 mm
Hydraulics
Statistically estimated rainfall: Historical rainfall series SVK30221 Virum
Storage volume in basin: Lake: 1,450 m3, Tunnel basin: 400 m3
Drainage from basin: 45 l/s.
Anticipated overflow: 2-3 overflows per year to the playing field, 3,000 m3/year (some infiltration, the rest runs back to the system)
Treatment
There is a sludge trap and oil/water separator before the inlet to the lake and also before the outlet to Lyngby Lake.
There is some settlement as well.
Location
Sennepsmarken, DK-2830 Virum
GPS (Krak): Lat: N 55º 47.025' Long: E 012º 29.114'
Google Maps link: http://maps.google.dk/?ie=UTF8&ll=55.784018,12.48226&spn=0.004452,0.009613&t=h&z=17
Contact
Name: Niels Drisdal Hansen
Organisation: Lyngby-Taarbæk Forsyning
E-mail: dri@ltk.dk
Telephone: +45 45 97 60 73
Photos
