Specifications

NAIROBI OPERATIONAL HUB
UNOPS Building, UN Lane, Off UN Avenue Tel: [phone]
P.O Box 783,Village Market, 00621 E-mail: [e-mail]
Nairobi, Kenya Website: www.unops.org
UNOPS is ISO 9001 certified
B. Examine the areas and conditions under which the underground electrical services
are to be installed, and correct any unsatisfactory conditions detrimental to the
proper and timely completion of the work. The Contractor shall not proceed with the
work until all unsatisfactory conditions have been corrected in a manner acceptable
to the Engineer.
3.02 EXCAVATION AND BACKFILLING
A. Before commencement of the excavation, check the presence of any existing
underground service by means of appropriate tools and equipment. The Contractor
shall be penalized for damaging of any existing services in accordance with the rules
and regulations set forth by the Owner and described in Section 16050.
B. Carry out excavation and backfilling in accordance with the requirements of civil
works
3.03 DUCT BANKS INSTALLATION
A. The direct buried PVC ducts shall have a minimum dry sand cushion of 150 mm
and a minimum dry sand cover of 300 mm, over which 50 mm thick concrete tiles
shall be placed.
B. Depth for direct buried PVC ducts and PVC coated rigid steel conduits shall not be
less than 600 mm from finished grade level to the top of conduits.
C. Top of concrete encased duct banks shall be installed 600 mm minimum below
finished grade and shall connect manholes and handholes as shown and required on
site. Where a duct bank connects to a building, adapt the duct bank, at one meter
beyond the building exterior wall, to the building conduit with the required
couplings.
D. The concrete encasement surrounding the duct bank shall be rectangular in cross-
section, having a minimum concrete thickness of 75 mm beyond any surface of the
conduit. Interlocking spacers shall be used to secure a uniform spacing between
conduits of not less than 75 mm.
E. Trenches and duct banks shall be graded so that conduits will have a fall of at least
75 mm per 30 m towards the lower manholes or from the high point of the section
towards the manholes or from the building towards a manhole.