Page 405 - Shaping smarter and more sustainable cities - Striving for sustainable development goals

 Agreement on the positioning of apparatus within a shared trench together with the
reinstatement specification should be made between all interested parties (including the
relevant authority) as early as possible as part of the planning process
 A primary promoter should be identified to take overall responsibility as the agreed point of
contact with the relevant authority. The primary promoter would normally excavate the trench
and install its own apparatus. The secondary promoter/s would then install their apparatus in
the same trench. The primary promoter would then backfill the trench and reinstate unless an
alternative agreement has been made

 With regard to statutory noticing and permit requirements it is the responsibility of each party
to individually notify their own works".
Further information about UK practice is given in [b‐4]. This indicates that the local street authority
has ultimate responsibility for coordination among stakeholders if difficulties arise. "A street
authority should discuss any difficulties that the proposed works cause with the promoter and agree
an acceptable way forward. However, safety concerns, urgency or lack of co‐operation, may make
it necessary for the street authority to use its powers of direction [b‐5].

Similar coordination examples come from other Countries too. In Italy, the city managing body
notifies each request for trenching to a list of all utilities and other parties potentially interested,
requiring them to evaluate the opportunity to share the same path for the installation of their
cables/ducts. This is done to minimize disruption to the traffic and to minimize costs. In some cities,
after a road has been subject to trenching, it cannot be dug again before three years.

3.1.2 Utility Tunnel

A utility tunnel is considered an optimal solution to avoid underground crowding of utilities in
narrow Right‐of‐Ways.
Sections 4 and 5 of ITU‐T Recommendation L.11 [b‐28] provide details on safety in utility tunnels.
This Recommendation notes that
 many countries are interested in the joint use of tunnels and are aware of the advantages,
disadvantages and specific dangers they hold;

 the rules governing this type of ducting vary significantly from country to country;
 the importance of the joint use of tunnels increases with increasing density of population and
shrinking open spaces, i.e. in large towns.
Annex 1 of [b‐28] provides an example Safety Plan against outside risks such as incoming gas and
water and an example Safety Plan for risks inherent in tunnel ducts such as smoke and gas leakage

One of the major issues to be considered for the implementation of utility tunnels is that through
all phases of planning, financing, construction and operation, the cooperation and agreement of all
concerned parties should be ensured. The policies and practices of government, public and private
utility providers and the various regulatory bodies should be considered.

Generally, pressure lines, such as water, irrigation, district cooling, as well as power and
telecommunication cables, are installed within the utility tunnels. Gravity lines, such as wastewater
and storm water drainage are normally avoided in tunnels due to difficulties in ensuring the
minimum slopes necessary for gravity flow which might have implications for the tunnel grade/slope
and depth causing deeper excavations and higher costs. In addition, gas lines are sometimes avoided
in tunnels to reduce risks of explosion that may be caused by accidents and/or heat dissipation from
power cables.

ITU‐T's Technical Reports and Specifications 395