92 Ill. Adm. Code 530.510
Encasement
Section 530
Section 530.510 Encasement
a) Encasement of underground utility crossings where required is
intended to serve one or more of the following purposes:
1) To allow replacement of utility without future disruption of
roadway structure.
2) To allow installation of additional facilities without future
disruption of roadway structure.
3) To vent or drain leaks of volatile gases or liquids that might
occur under the roadway structure.
4) To serve as bridge or carrier through unstable soil structure.
5) To prevent cavitation under pavement structure from leaks of
pressurized liquids.
6) To allow ease of insertion and coating protection of utility
conductor or carrier.
7) To provide protection of utility conductor or carrier from
superimposed loads or "dig-in" damage.
b) Casing pipe shall be designed to withstand the load of the
highway and any other superimposed loads. The casing shall be continuous
either by one-piece fabrication or by welding or jointed installation approved
by the Department as defined in Section 530.30.
c) Underground utility crossings without encasement will
generally preclude future maintenance or repair in the area between ditch lines
or toes of slopes.