Murnane joined the Municipal Water Department in February 1920 and became the head of the department in 1925. Significantly, during his time, Singapore began importing water from
Gunong Pulai in
Johor (now part of
Malaysia). Under an agreement with the
Sultan of Johore, raw water began to flow on 2 June 1927 and, as a result, the "danger of a water famine in Singapore ... had practically disappeared". Filtered water from newly built
reservoirs and filters in Gunong Pulai began to flow on 31 December 1929. This water flowed by gravity to the
Pearl's Hill Reservoir about 33 miles away. At that time the population of Singapore was 525,000 and water consumption was 16.5 million gallons per day. The total project cost was $16.2 million, a tremendous investment which would cause Singapore water rates to be the highest in
Malaya. Arguably, the Gunong Pulai water supply project was the most significant public infrastructure project undertaken in water-scarce Singapore. It was reviewed favourably in 1928 by a visiting independent commissioner from
Burma who said it was the biggest municipal project he had heard of in the region. The Municipal Treasurer reported in 1930 that he found the project was managed to a very high standard in terms of financial controls. For photographs of the Sultan Ibrahim reservoir at Gunong Pulai, which was handed back by the Singapore
Public Utilities Board to Malaysia in 2011, including the commemorative plaque with the names of the key engineering staff, click through the footnote By 1938 Singapore needed additional water supply for the growing population and Murnane was responsible for the long term planning: 'many a water-works engineer spends his time carrying out the plans of his predecessor and thinking out the work to be done by his successor'. Murnane proposed a major $5.5 million investment which involved a new 39" duplicate pipeline from Gunong Pulai to Singapore, a doubling of water treatment capacity in the Johor reservoirs, and the building of a large
new permanent reservoir in
Seletar in Singapore. By this date water consumption in Singapore was 21 million gallons per day.
The Straits Times on 2 April 1939 has photos of construction work including one of Murnane supervising the works which involved 1,400 workers installing -ton lengths of pipe. Murnane was already planning a second major water supply project in Johor, this time tapping the Johore river near
Kota Tinggi. He oversaw a one-year experiment which demonstrated the river water could be turned into "pure sparkling drinking water". The municipality of Singapore either approved or was about to approve the project in 1941 but stopped because of the war. After the war Murnane made the case for the $40 million investment in the Johor river water supply project which was ultimately undertaken by his successor F. G. Hill. ==Reflections on Singapore water supply and comparisons with other cities in Asia==