In the old days, the main ammo dumps were located at:
Alexandra
Rifle Range Road
Seletar Camp
Sembawang with it's own harbor
These camps had deep bunkers dedicated to storing explosives & ammo, and not the small amounts stored for standby use with active units. Back then I heard that Spore only had enough ammo stored for 3 days of hostilities? With the congestion in Spore I doubt there is enough storage space in Spore for storing more for a prolonged war.
Many of them were set up by the British. I'm sure that some of them are now gone like the one at the Seletar camp which has become repurposed for civilian use, & probably the one at Alexandra, ...
In any war you need lots of ammo & for a small country like Spore which has plans for a population of 10 million, it's just not practical.