How to protect HDB roof access to water tank

• Sembawang Town Council general manager Soon Min Sin said that there is “no foolproof method” to prevent water tanks from being sabotaged.
• Rooftop-access keys are under “strict control”, said Mr Soon. The Town Council will issue a copy of the roof-access door’s key to those carrying out maintenance and emergency lift-rescue work
• Other than the occasional spot check, the Town Council staff conduct checks on the rooftop once a month
• “Because the water tank is a sensitive asset, it has to be protected all the time,” said Prof Gunaratna. Mr Soon said that the Town Council is studying feasible ways to improve security such that maintenance or emergency work is not hindered.

The above are extracted from http://news.omy.sg/News/Local%2BNews/Story/OMYStory201105180041-245747.html

As I understood, they have came up with a countermeasure that only town council staff may hold the key (cannot be duplicated). If the service worker need to access the roof and water tank, the town council staff is suppose to accompany the worker to unlock the roof and water tank. The problem is whether the town council staff will stay with the service worker all the time while he carry out the operation.

If not,  the service worker may put special ingredient into the water tank.
If yes, what is preventing the town council staff from staying with the worker until work completion ?

I have come up with a procedure that may help the situation…

• When the service worker need to access the roof and water tank, he will need to go to the town council to draw the key.
• A town council staff will need to follow the worker to unlock the roof and water tank.
• The town council staff will need to stay with the worker until the operation for the water tank complete (This may not be easy to enforce).
• Once completed, the town council staff will need to inspect the water tank and take digital photo on the inside of the tank. He will then return the keys to town council.
• The town council staff will then submit an online form (attached the photo) to the HDB database.
• There will be another group of HDB inspectors who will check the HDB database for all the water tank completed work.
• HDB inspectors will be dispatched to the various location to do a final inspection on the water tank on the completed work. The inspector will need to go to the town council to draw the key.
• HDB inspector will inspect the completed water tank and make sure that there is no abnormality. He will need to take digital photo on the inside of the tank and submit it to the HDB database.
• A water sample of the water tank is also taken and tested at later time. This test may be done on a random sampling basis. Those samples that are not tested should be stored for at least 3 months.
• After inspection completed, the key will return to the town council.
• If there is too many inspection work, the HDB inspector may do a random check on a few selected water tank. This will depend on the workload of inspection.