Scottish Water is producing a computerised sewer model which will enable engineers to simulate storm run-off flows through the sewer system. Testing and inspection specialist IETG is instrumenting the sewers and gathering flow data so that assumptions put into the computer model can be verified.
'Scottish Water needs to make sure its synthetic rain behaves like real rain, ' says IETG team leader Ian Clayton.
IETG's monitoring will help Scottish Water gauge the effects of new urban development and delapidation in the sewer system.
Monitoring involves worming through pipes to points in the system that best lend themselves to being monitored: 'If flows are too low you get silt around the bottom of the tunnel which affects the sensors, while turbulence results in velocity disturbance, ' Clayton explains.
IETG's instrumentation team has installed expandable 14 steel rings that fit snugly inside the sewer pipe, gripping the wall. Rings are equipped with ultrasonic depth, pressure and velocity gauges, all of which are connected to batterypowered transmitters. These use mobile phone technology, powered by solar cells at pavement level, to relay data in real time to a computer at IETG's Leeds headquarters, from where it can be downloaded.
Impermeable surfaces have been mapped (red) to show engineers the total catchment feeding into Glasgow's sewers.
Blue dots show location of the flow monitoring.
Monitoring is set to stay in place for up to two years.
'We have to get in to the sewers when flows are low - we put most of them in at night when nobody's using their toilets or baths. The best time is between 3am and 5am.'