Martin Schwalm, managing director of Schwalm Kanalsanierung, Bad Hersfeld, on quality assurance in sewer inspection and repair work, the benefits of sewer registers and trends in the technical development of inspection tools.
Mr Schwalm, local authorities are keen to find economic solutions for preserving the value of the underground infrastructure. What should they therefore bear in mind even at the early stage, for instance, of commissioning cleaning services?
Good quality on economic terms is certainly achievable. It only becomes problematic if by affordable people mean cheap. Experience shows that the cheapest work is not done with the requisite care. Sliding price scales are another problem. They tempt people to set prices as low as possible in order to be in with a chance on open tenders. With restricted tenders it is at least possible to issue projects amongst companies that have excelled in the past through their careful work. I would advise every local authority to set up a sewer register. That enables targeted work and keeps costs low.
What efforts are being made in the industry itself to ensure the quality of the services provided?
A sense of tradition, self-criticism and keeping a check on your own work are key criteria for quality. Clients and contractors must doggedly work towards ensuring that quality wins the day. It can’t work without trust. And price alone is no basis for establishing that.
Can you demonstrate with an example how quality and a company’s own controls link in together to the benefit of the local authority client?
Yes, when doing video inspections the operator should see the sewer through the eyes of a layman. As an operator I clearly know whether what I see on the screen is a cobweb or a crack. However, I can’t expect that of anyone with an untrained eye. I must therefore produce comprehensible images, with no short or jerky panning of the camera. Our trade association specifies a speed of travel for the camera robot of no more than 15cm a second and requires that you work in a manner appropriate to the condition of the structure in question. On the one hand that is very exact, while on the other it needs to be properly interpreted. It is the operator’s responsibility to produce usable images.
As part of the switch to double entry accounting, many local authorities are now faced with the task of recording and evaluating public fixed assets. How important in this respect is the role played by the data collected, for instance, during systematic inspection of the sewers?
In contrast to plans, sewer inspections record the actual condition. That’s what makes them so important. The findings ideally get incorporated into a sewer register that documents the weak spots, i.e. places in the network, for instance, where a frequent need for cleaning can be expected, such as after heavy rain. Apart from this technical reason, however, the collected data is also of economic importance, as it helps the local authorities to plan their budgetary funds more accurately.
It is unreasonable every time a sewer is inspected to compute the data needed for the inspection all over again. What procedure do you therefore recommend for sewer network operators seeking to build up a reliable and expandable database of their network?
If you only perform sewer inspections on an ad hoc and chaotic basis, you will admittedly keep the inspection costs low, but you will get no overall picture of the facts of the situation. Yet a realistic overall picture is the very purpose of any sewer inspection. Systematic inspection of a network can be performed on a sewer line or area basis. Essentially, a strategy should be developed for how the whole of the inspection work is to be spread over a set schedule.
Sewer inspections and repairs involve filming, milling, brushing and flushing. In what direction is the development of new tools going?
Well, automation will continue to make advances. Specialists will therefore increasingly be operating machines. As a result, a more qualified workforce will be needed. For around four years now, this development has been taken account of by the introduction of vocational training for pipe, sewer and industrial service specialists. In general it can be expected that trenchless rehabilitation methods will continue to be refined. A key advantage of this method compared to opening the sewers up is that traffic lights, road closures and diversions are avoided. For who works out the indirect costs caused by the impact of such measures on traffic? For the local authorities the trenchless method means greater cost transparency.