Greening the rainwater drains for a factory and its grounds

For sustainability reasons, a client representing the manufacturing industry asked Volantis to identify and segregate the flows of stormwater on the grounds and roofs and disconnect them from the sewage system to the maximum extent possible. This may involve discharging the disconnected rainwater in the municipality’s separate system or otherwise allowing it to be absorbed by the soil and into the bioswales near the factory. Segregating stormwater and sewage will help us reduce the burden on the current sewage system, and thus reduce the kind of flooding we currently experience when it rains very hard.

Volantis realised this entire project, from the feasibility study to the functional design, and from the call for tenders to execution oversight.

The broad outlines of the project were as follows.

Step 1:
The first step taken was an analysis designed to help us determine whether the existing infrastructure in the grounds would allow us to disconnect a substantial percentage of the water. Among other things, we had to focus on the following water-bearing components and focus areas:

• Roofs
• Grounds
• Contamination
• Position of existing infrastructure and drainage gradient
• As-built drawings available to us
• Measuring the system and manholes
• Mandatory soil testing

Step 2:
We then looked into several variants, made choices and further detailed the draft design, adding a cost estimate to be included in the investment proposal (to obtain the necessary budget). When designing an infrastructure-related project, it is vital (and justified) that you budget more generously and allocate a greater budget to incidental expenditure than you would in a building construction project. After all, it is not always possible to get an exact idea of what is in the ground, least of all when you are dealing with grounds belonging to old factories. You are likely to run into snags, and it is a good idea to have a fallback plan just in case.

Step 3:
Step 3 involved adapting the draft design into a final, functional design, with functional specifications. In this project, we made a conscious decision to draw up functional descriptions with drawings and to submit these to the usual infrastructure contractors, along with an open budget. This allowed us to get started on this project soon afterwards, as part of a construction team, and aided by the infrastructure contractor’s expertise.

Step 4:
And so the execution of the plan began. Volantis oversaw the implementation of the project and was also tasked with supervision and commissioning.
It was quite the challenging job, with several setbacks and unforeseen situations, but we stood together as a team and successfully completed the project.

Upon the practical completion of the project, we had to carry out water pH tests, to demonstrate to the municipality that the disconnected had been reconnected properly, in accordance with the plan. We supplied additional evidence in the form of photos and as-built drawings, and that marked the completion of the project.

Result
The project resulted in some 100,000 square metres’ worth of floor area being disconnected from the sewage system, stormwater-wise, making them much greener. Some 75 million litres of water annually will no longer end up in the sewers.

The project presented some challenges, as well. For instance, several surprises were waiting for us hidden in the ground, such as pipes that were either in a different place than shown on the floor plans or not indicated on the floor plans at all. Unfavourable and slight height differences also caused some issues with regard to the disposal of the water. We were able to include the lower parts into this greening project by utilising pump station technology. In addition, planning was a challenge, since production and logistics had to continue as usual.