Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...

Encouraged by its success in these two pilot schemes, PUB put out to tender the first of its two major
schemes to renovate the bulk of Singapore’s older sewers in six subsidiary projects. Phase 1 (valued at
U.S. $105 million) involved 420 km (261 mi) of sewer and was shared by three contractors: IPCO,
Johnson Pacific using InLiner, and L&M using Permaline.
The scale of the Phase 1 project established the three companies and encouraged new competitors to
target the Phase 2 released for tender from 2001. Phase 2, nearing completion and valued at U.S. $73
million involved 350 km (217 mi) of sewer and was shared by the three contractors from Phase 1 together
with new players PRS (now Sekisui) and Jetscan, who utilized the Multiliner system. The PUB sewer
renovation program from 1993 to 2005 involved an investment of almost U.S. $200 million and addressed
problems in 800 km (497 mi) of sewers. It commenced with two small-scale projects, initially managed
with outside expert experience and concluded with two substantial schemes that established a pool of
expert contractors. The issue of contracts on this scale had a major impact on unit length pricing. The
average pricing fell from S $550/m to S $205/m (U.S. $128 to U.S. $48 per ft) in the 10-year period since
1993. There were many technical developments employed in the period, including the use of pressure
inversion vessels, resin extenders, fast cure catalysts, fiber reinforcements, and innovative scheduling to
achieve product quality and cost reduction.
In 2006, Phase 3 was released and will continue until 2012. It involves sewers and private drain lines in
the Marina Barrage Catchment. As part of the Four Taps strategy, PUB has constructed a barrage across
the mouth of the Singapore River. This U.S. $226 million dam constructed across the mouth of the river
created Singapore’s 15 th reservoir in 2008. It took the top prize awarded in 2009 by the American
Academy of Environmental Engineers. The Marina Reservoir is used for flood control, water storage and
recreational facilities such as boating. It is important that is not polluted by sewage and PUB has
conducted a major investigation to identify sources of exfiltration and groundwater pollution. Phase 3
will address issues identified in 600 km (373 mi) of the public sewer and private drain line network in the
Marina area. Investment is expected to be in excess of U.S. $100 million.
Phase 4, which involves 1130 km (702 mi) of sewer, is also now under way and is expected to cost a
further U.S. $100 million. It is hoped that Phase 4 will be completed in 2012. The PUB Web site
currently lists 1,264 individual projects scheduled for 2010 to 2012 and the majority involve sewer
rehabilitation. In addition to gravity sewers, PUB has relined a significant amount of sewer force mains
using Sekisui’s Nordipipe product, and products from Insituform including the Kevlar reinforced liners,
InsituMain ® Pressure Liner and InsituMain ® Reinforced Pressure Pipe.
At the present time, PUB estimates that it has lined in excess of 1,100 km (684 mi) of the 3,400 km
(2,113 mi) network, i.e., about 30% of the wastewater collection system. In addition to CIPP (900 km
(560 mi), it has used some 120 km (75 mi) of spiral wound pipe and about 60 km (37 mi) of fold-andform
(mainly Ex-Pipe from Australian contractor Kembla Construction). About 150 km (93 mi) of
private sewers have been lined and some 9,000 top hats installed at private sewer connections.
PUB has carried out inspections of historic rehabilitation projects, typically after about 10 years in
service. Early installations at Paya Lebar, Kim Seng Road, and Bishan Street were found to be in
generally good condition with no major defects. However, some defects have been identified, for
example, a collapsed liner in Ubi Avenue and serious longitudinal wrinkling in Geylang Road.
Much of the early work tendered by PUB was water inversion and hot water cure; however, in recent
years, some steam curing has been undertaken and it is estimated that this method amounts to about 50%
of current work. Much of the air inversion steam curing is carried out on the private drain lines in the
Marina Catchment. UV curing has also been undertaken on one project to date. Design work is
undertaken by PUB staff and by independent consultants – particularly CPG Consultants, a local
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