NL06 Werkendam

Bigger Does Not Mean Better in Werkendam

The sewer system of the municipality Werkendam in the Netherlands covers different drainage regions, one of which is Vervoornepolder that has a combined sewer system and is situated in the east of Werkendam. The municipality decided to extend the line utilizing HOBAS CC-GRP SewerLine and ShaftLine for a new sewer retention system.

The sewer of Vervoornepolder used to have four overflow channels. One of them was already equipped with a retention tank. However, calculations regarding sewer capacity showed that a new overflow was necessary. To minimize surcharges, the sewer would have had to be extended at various points. Unfortunately, this was not possible for the lack of soil coverage and inclination. Another option was a retention cellar yet this solution would not have met the required capacity. Plans had to be reviewed which led to the conclusion that it would be best not to extend the old sewer but to install a new retention system including new overflows in the surrounding.

The new retention system incorporates a pumping unit that pumps all wastewater into the old sewer if necessary. The line feeds through four overflows between the old and the new sewer. With this system, the retention sewer is only active in cases of heavy rainfall. During dry weather conditions or light rainfall the wastewater runs through the old sewer. This creates following advantages compared to an extended sewer system:
- During dry periods the flow rate is higher in smaller sewers so that deposits are kept to a minimum
- Less mud is stirred during heavy rainfalls and the overflowing wastewater is therefore cleaner

The retention sewer was fully designed by the municipality of Werkendam. One of the most important criteria for the choice of material was its weight. The soil around Werkendam contains high levels of peat which makes it prone to subsidence. The choice therefore fell on HOBAS CC-GRP SewerLine and ShaftLine since not only the products’ weight but also their smooth inner surface is highly advantageous for the application. Mud is prevented from depositing during reverse pumping from the new retention sewer into the existing one.

Reducing costs and inconvenience by short installation times:
- Light weight pipes; DN 1200 = 154kg/m, DN 1000 = 109 kg/m;
DN 800= 70kg/m.
- The standard 6 m pipe length facilitates installation considerably. A 6 m long DN 1200 pipe weighs 924 kg.
- Flexible FWC Couplings with rubber gaskets keep installation times short.
- Groundwater drainage is limited or can be avoided for HOBAS Pipes are easily laid.
- There are no delays during cold weather periods because HOBAS Pipes can be promptly installed at temperatures below 0°C.
- There is no need for heavy equipment such as telescopic cranes. A light mobile crane will do the job.

Hydraulic advantages:
- HOBAS CC-GRP Pipe Systems are completely leak tight.
- Pipe cleaning is not or hardly necessary due to the smooth inner surface of HOBAS Products.
- Less sedimentation due to the very low roughness coefficient (k = 0.01) of the inner pipe surface;
- No blind areas, with references to the good functioning of cleaning pumps, no 90 degree angles like in a concrete sewer storage system.

Resistance:
- HOBAS CC-GRP Pipe Systems are completely corrosion resistant to sewer gas and aggressive sewer fluids.
- They are furthermore abrasion resistant and easily pass the Darmstadt Test according to DIN 19565.

Other advantages:
- Comparably thin pipe walls (DN 2200 = 35.3 mm);
- HOBAS^® Couplings are guaranteed leak tight up to -0.8 bar.
- Compactness of the basin;
- A complete system solution was provided including manholes;
- HOBAS Products are compatible with and connectable to other materials (concrete, clay pipe, PVC, etc.);
- They have a lifetime minimum of 50 years.

Downloads

NL06SEL_Werkendam.pdf