Lenz Military Base is next to Soweto at Lenasia. The site is about 2 km long and half a km wide. Historically it was used for manufacturing and storing of explosives, a combined exercise between the private sector and the Army. But now all bunkers are empty and abandoned. The only section still in use is the housing, the offices and the barracks, which is about a quarter of the site along the north side of the site.
SEM Solutions were awarded the contract for water management on this site in January 2000 as part of a performance contract with the Department of Public Works in Johannesburg. The aim of the contract is to reduce water consumption and to monitor the consumption thereafter. After the preliminary investigation, our report for implementation would include leak detection, pressure control, upgrade of certain fittings etc. but this does not reflect the potential of savings. That surprise only started to unfold in the next six months.
We started our investigation and implementation during 2001. First step was obtaining history consumption data from Rand Water:
(see visual in the article below)
Then we dug for drawings in the archives of the Department of Public Works in Johannesburg. Some dated back to 1950. But every little bit of information helped in putting the puzzle together. Dry hydrants on site for example related to the old mains of 1950, but the new mains were not documented. So we started pipe tracing on site. Fortunately pipes were steel and tracing could be done relatively fast.
Pipe tracing revealed 3 lines of mains along the length of the site. Two of these were supplying the bunkers at the back side of the site and one the front section that is still in use. And that became our strategy: to eliminate the two lengths of mains at the back and to only use the one length of main along the north side of the site.
Closing valves on these sections were fruitless and pipes had to be blanked off. Slowly but surely the consumption started to come down. Over December 2001 we built the first valve cabinet with our own water meter and pressure control valve. What a discovery to find that the Rand Water supply pressure is 2 000 kPa!
We divided the site in 4 zones, each with its own valve cabinet and water meter. Obviously this decision could only be made once the pipe routes were established and confirmed.
The first recordings from our main water meter were astonishing: A water consumption profile of a straight line at 110 m³/hr. That proofs the monthly consumption of ± 80 000m³:
(see visual in the article below)
After six months of hard work and hours of searching and digging etc. the consumption started to come down month by month.
(see visual in the article on the right)
From thereon it became maintenance and “fine tuning” to obtain further savings from 15 000m³ consumption per month to less than 10 000m³ per month. As the consumption started to come down, the consumption profile became more of a real profile, rather than just a straight line:
(see visual in the article below)
Although the zero-flow is still some 6 m³/hr or ± 4 000 m³ per month, which is still a loss of 60%, a consumption of 7 000m³ per month is less than 10% of the original consumption. The split in zero-flows amongst the zones are as follows:
Zone-1 = 1.0 m³/hr
Zone-2 = 1.5 m³/hr
Zone-3 = 3.0 m³/hr
Zone-4 = 0.5 m³/hr
To find these leaks will most probably mean replacing all pipes with new pipes. What is important, is that this magnitude of savings could be achieved without replacing the water mains. A GSM-type logger relays the daily consumption profile to our offices. Therefore any serious leak will be revealed within a day.
At a cost of R5.00/m³, the annual cost of water reduced from R5.3m to R550 000.
