2013 Water System Plan, Volume II - Seattle City Clerk's Office - City ...

The design engineer must carefully review the buried-to-aerial transition to ensure
the pipeline will be able to handle ground movement from earthquakes. In most
cases, a restrained joint with both rotational and expansion capabilities (e.g. a
double ball expansion joint fitting) is recommended. See also DSG section 5.8.4,
Seismic Design.
Freeze protection design must be considered. Potential options include one or more
of the following:
1. Insulation of the pipe;
2. Heat tape.
3. In case of a temporary change in the way the pipe is used resulting in low flows
consider installation of a system to allow a release of a small volume of water to a
location that does not cause an environmental impact or safety hazards
C. Temporary Supports during Construction
Supporting existing utilities during construction can be difficult, but is necessary to
ensure no damage occurs to the existing pipelines. Typically, the construction contractor
is responsible for supporting all existing utilities throughout construction. The
contractor must provide a support plan that is stamped by a Professional Engineer
licensed in Washington State. SPU engineering and Field Operations and Maintenance
will review temporary supports in the field and notify the contractor of deficiencies. SPU
Water Operations staff does not direct repairs.
The following is a list of cautions contractors must take to avoid damage to pipelines:
5.6.3.7 Casing
Contractors must not use chains to move or support any pipe materials because
it will damage the pipeline.
Contractors must not rest the pipe on any sharp or pointed objects, including
the bucket of any equipment, single point supports, or rods.
Pipelines must not be unsupported for a length longer than one stick of pipe or
one joint.
If the joints are not restrained, the contractor must ensure crew safety by
restraining the pipe from movement, which could separate the joints.
Pipelines must be supported in cradles or on wide support beams sufficiently
spaced so the pipeline does not sag and cause undue stress on the joints or
pipeline wall. This is especially important for cast iron with lead joints.
Do not expose more than one unrestrained joint.
Lead joint cast iron water mains must not be allowed to deflect while they are
exposed.
Water mains are installed in casings to protect the mains from excessive loads and to provide a
means of replacing the pipe beneath structures such as rail road tracks. Casings also reduce the
damage to facilities over the water main in the event of a leak or main break. Sometimes casings
5-22 SPU Design Standards and Guidelines