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

All design and construction supervision is undertaken by external consulting engineers. GS considers its
role to be one of owner and facilitator, with expertise – it directs and delegates, but doesn’t do the work
itself. Supervisors are required to be certified PE welders and to monitor critical site activities at any time
of day or night. Monitoring of the cooling phase (of CIPP and fold-and-form) is considered especially
important as this is where contractors cut corners to save time.
The problems encountered relate to watertightness. GS’s aim is a watertight system, and after 15 years of
using CIPP, and some 15,000 watertightness tests, determined that it is an excellent long-term repair
method, but will not provide a permanently watertight system. This is due to problems of sealing ends at
manholes and of sealing the openings at lateral connections. CIPP can give a watertight pipe, but not a
watertight system. GS has switched its strategy to achieve complete system watertightness to aiming for
a 100% PE system, with welded joints throughout. When installing new pipe, only materials approved by
DVGW for gas use are allowed to be installed. This is the reason that, since 2006, PE rehabilitation
technologies have replaced CIPP at GS.
Nevertheless, it continues to use CIPP where extension of service life until PE replacement or lining is
undertaken is needed. GS’s view is that quality of installation has improved significantly since the 1990s,
especially in areas such as reopening of laterals. Testing has also improved so the overall QA/QC
approach is now credible and CIPP is considered to be a reliable repair method. In order to ensure the
quality of CIPP installation, GS requires that installers have a QA manual covering all processes and
submit it to GS in advance of undertaking any work. The supervising engineer is expected to monitor
adherence to the QA procedures set out in the manual and to prevent the contractor from cutting corners
with curing cycles, etc., in order to work more quickly. GS has noticed a reduction in prices of CIPP in
recent years and considers that this represents increased risk as contractors have to work more quickly in
order to make money, and this leads to cutting corners. GS would prefer to pay more and take less risk of
poor installation.
GS also has a policy of not rehabilitating pipe in condition class 2 or worse (Germany has five condition
classes, 0 to 4, of which 4 is the best and 0 the worst). Any sewer in classes 0 to 2 is replaced with open
cut. Rehabilitation with CIPP is only used for class 3 and 4 pipes. This is despite CIPP costing typically
one sixth to one quarter of the open cut price. Also, when CIPP is used in collectors with few lateral
connections, the lateral connections are diverted to manholes and old openings are lined over to avoid
problems of watertightness around the lateral connection junction. Manhole rehabilitation is also
undertaken, under a separate contract.
GS is a special case because of its watertight network policy. However, it was a leading adopter of CIPP
in Germany and is considered by its peers to be an expert client at a technical level, despite any
misgivings about the underlying policy. Therefore, its adoption of CIPP and its switch to PE is of
interest. As stated above, it now considers CIPP to be an excellent long-term repair technology with a
service life of 50 years and that can make individual pipes watertight. But it does not meet its
requirement of achieving a permanent, watertight network.
C.6 Technische Betriebe der Stadt Leverkusen (TBL)
TBL was interviewed in Leverkusen on November 2, 2010. The interview was conducted in German.
TBL is the technical service of the City of Leverkusen, Germany. The population served is 150,000. The
collection system is both separate and combined, with a total mains length of 660 km (410 mi) and
approximately 90,000 lateral connections.
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