Section 3 Annex H
3. Seismicity
The Site falls within a stable seismic environment, rated 7 on the modified Mercali scale. (Loupkine: seismic zoning map of Keyna). Tremor intensities of Richter 5 have been experienced in this area in recent years without significant damage to any structure.
The "Kenyan Code of Practice for the Design and Construction of Buildings and other Structures in Relation to Earthquakes” (1973) confirms that damage will be negligible for "properly designed and constructed" buildings within a zone 7 categorisation.
4. Meteorological Data
The nearest full meteorological station is located at the Kenya Meteorological Department Headquarters at Dagoretti, some 6km to the west of the site.
A meteorological summary for Dagoretti is included under Annex L.
For the purposes of design of buildings, the Kenya Meteorological Department recommend wind gusts of 27 m/s for the Nairobi area.
Rainfall intensities are given in the Rainfall Atlas of Kenya. Figures for the Dagoretti Station are included. These are presented in the form of rainfall intensity - duration curves for return periods between 5 to 100 years.
5. Services
(a) Electricity. Power lines run along Upper Hill Road and through the site on to Lower Hill Road. There is a connection to the existing house on the plot. There is a pole mounted transformer located close to the disused entrance to the plot on Upper Hill Road.
(b) Water. A 62mm water main runs along Upper Hill Road with a 100mm main joining from Mara Road, pressure varies from 69Kpa to 483Kpa. Local residents report
low
water pressures but the supply rarely fails completely. Generally, to ensure adequate supplies, it is wise to install ground tanks and pumps to lift the water to roof tanks.
(c) Telephones. Telephone services manholes are located on Upper Hill Road adjacent to the power transformer referred to above.
(d) Sewerage. There is a 100mm diameter sewer running along Upper Hill Road, and a 225mm diameter main sewer lower down and parallel to` Lower Hill Road. Domestic sewerage from the existing property drains towards the sewer below Lower Hill Road.
(e) Surface Water Drainage. This comprises open ditches, some of them lined, with small culverts under the roads. Culverts are generally silted up and the ditches are poorly maintained and probably ineffective. The surface water from the area above Upper Hill Road runs in a dry water course over part of the site. This can be diverted and piped with access points, taken under Lower Hill Road, to discharge down the slope.
6. Design Standards
Buildings in Nairobi are generally designed to British Standards and in addition they must comply with the Nairobi City Council Building By-Laws.
A soil report summary is given under Para. 2 which should be used as a guide. All floors to be designed for a uniformly distributed live load of 5kN/m2 with a framed structure preferred.
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