[2] In 1958, Lee joined the City Council (later the Public Works Department) as an engineer and was responsible for drafting Singapore's first Sewerage Master Plan.

[4] From 1971 to 1972, Lee was the Permanent Secretary (Special Duties) of the Ministry of Health, succeeding Tan Teck Khim.

[6] In addition to banning bumboats, hawkers, and squatters from the area, Lee Ek Tieng also commissioned contractors to dredge the bed of the Singapore River by 1 metre (3 ft 3 in) and replace its mud and waste with sand.

[8] The entire operation, which ended up costing approximately S$300 million, was deemed a success, as evidenced by the return of fish and other sea creatures to the Singapore River.

"[12] In September 1978,[13] while he was still overseeing the cleaning of Singapore's rivers, Lee succeeded Lim Kim San as head of the Public Utilities Board (PUB).

After assuming leadership of the PUB, Lee made the production of reclaimed water one of his top priorities.

When the technology became more cost-efficient in the late 1990s, Lee greenlit the construction of a Bedok-based facility that would produce 2,200,000 imperial gallons (10,000,000 L; 2,600,000 US gal) of reclaimed water each day.

[15] Mindful that there was a "yuck factor" to reclaimed water, Lee christened the PUB's product "NEWater".

[17] Lee served as the managing director of the Government of Singapore Investment Corporation (GIC) from November 1989 to December 1997.