Challenge
Development challenges that the Project tackled included: (a) insufficient capital investment to replace decaying infrastructure and to keep pace with rapid urban growth; (b) the frequent flooding that occurred in cities because of undersized drains and inadequate routine maintenance, (c) severe pollution of water courses, particularly in densely populated areas of cities, because there was no provision for wastewater collection and treatment; and (d) weak utility agencies.
Implementation of the project had also been challenging because:
• The project was technically complex, involving tunneling works which were often subject to unpredictable surface soil and groundwater conditions.
• The client was unfamiliar with the engineering technology and with Bank procurement procedures, repeated changes in the project management, high inflation costs or problematic performance of several contractors;
• The project site was located in the most densely populated central business district of the city with critical traffic management issues.
Solution
For 20 years, Nhieu Loc – Thi Nghe was a dark and smelly canal full of waste. Begun in 2002, the project was designed to address these issues. This involved the construction of a sewer interceptor under the canal, 8 kilometers long and 3 meters in diameter, to improve the canal’s drainage capacity, as well as strengthening of the canal’s embankments and installing over 60 kilometers of sewer lines.
Because the project is located in the central business district, construction work could only be done at night for the most part. The unpredictable relocation of existing underground water pipes – including a 2 meter diameter water main, power and telecommunication cables added to the challenge. The project applied tunneling works in Vietnam’s unpredictable sub-surface soil and groundwater conditions that had never been done before.
Results
The Project has had a transformational impact on the city, lifting the city’s urban face. Thanks to the Project, 96,000 households (400,000 people) now enjoy reduced flooding, and 240,000 households (1.2 million people), mostly poor, now have centralized wastewater collection. Fish are now returning to the Nhieu Loc Thi Nghe canal, proving that the water quality in the canal has been significantly improved.
Between 2002 and 2012, the project helped to install a 9 km wastewater interceptor with an inside diameter of 2.5-3.0m with a pipe-jacking technology that has been applied for the first time in Vietnam.
It also replaced and extended: i) 51km of combined primary and secondary sewers; and ii) 375km of tertiary sewers.
It also conducted: i) dredging, transportation and disposal of approximately 1.05 million m3 of sludge and excavated material to increase the hydraulic capacity of the canal; and ii) strengthening of 18km of canal embankments by concrete sheet pipe.
