The site is one of a number around the capital the army is considering as bases for surface-to-air missiles to protect the London games from an aerial attack, the Ministry of Defence said.
It is the first time such missiles have been deployed in London since the end of World War II, shocking some residents at the Bow Quarter housing development, sited in a converted red-brick Victorian match factory.
Defence Secretary Philip Hammond first announced the plans in November, saying Britain would follow the precedent set by previous Olympics such as the Beijing games in 2008 where surface to air missiles were stationed a kilometre south of its showpiece stadiums.
The defence ministry said in a leaflet sent to occupants on Saturday it had chosen the former water tower in the Bow Quarter complex because it offered “an excellent view of the surrounding area and the entire sky above the Olympic Park.”
The tower was in fact “the only suitable site in this area for the HVM (High Velocity Missile) system,” it added.
In 2005, a day after London was named host city, four homegrown suicide bombers attacked three underground trains and a bus, killing 52 people.