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EIA NHDC Project Cap Malheureux

Feb 2011

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5 PROJECT ENVIRONMENTAL BASELINE

5.1 Topography and Landuse

The topography of the site is fairly flat. Elevation at the site is about 5m (amsl). Fig.5.1

provides a contour plan of the project site.

The project site originally belonged to the State, with no particular land use. The site is

covered with grass, bush and trees of no ecologic value.

5.2 Geology and Soils

5.2.1 Surficial Geology

The Geological Map of Mauritius indicates that the surficial geology in the region of the

project site consists of fresh lava flows of the Recent Volcanic Series. Fig. 5.2, an extract

from the Geological Map illustrates same.

5.2.2 Soil Type

The soil type obtainable at the project site and vicinity is of the Lithosol Group, in

particular of the T3 Rock land Family (Skeletal soil on hummocky bedrock), Fig. 5.3.

5.2.3 Soil / Percolation Investigation

Soil / percolation investigations at the project site was carried out during January 2010, to

obtain, inter alia, the following information:

Description of the soil profile down to a depth of 3m

Permeability of the soils

Water table levels

The investigation consisted of the following:

excavation of one trial pit;

determination of the rate of water percolation in the trial pit.

The location of the trial pit is given Fig.5.4, and the type of soils encountered are illustrated

in Plates 1(a) and 1(b) at the end of this Section.

Soil logs obtained at the trial pit are as follows:

0.0 – 0.5 m

Brown sandy SILT with fine roots. TOPSOIL.

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0.5 – 3.0 mFirm, mottled reddish and yellowish brown slightly sandy SILT and moderately

weathered rock. RESIDUAL SOIL

5.2.4 Percolation Tests

Percolation tests conducted at the trial pit indicate a permeability of 50mm/hr –

characteristic of a permeable soil.

5.2.5 Water Table

No standing water was observed in the 3m deep trial pit. Further, there was no sign of

gleying or grey mottling in the soil profile that would have indicated the occurrence of

water logging in the past.

Consequently, it may be safely concluded that any water table would be at a depth greater

than 3m at the location of the project site.

5.3 Climatic Conditions

The mean temperature ranges from 22oC in July (winter) to 30

oC in January (summer),

Fig.5.5.

The average winter rainfall over the region is of the order of 400mm and the average

summer rainfall 800mm, Fig.5.6.

Average wind velocity varies in the range 4 to 16 knots. However during cyclones, 3s gustsmay reach 275 km / h.

5.4 Hydrology / Drainage

There are no natural watercourses either crossing the project site or in the vicinity of the

project site.

Rainfall in the region is limited to rare events – mainly linked to cyclones during thesummer period.

As regards drainage, the percolation rate observed at the project site, as mentioned above,

indicate absence of sustained and substantial runoff, if any.

5.5 Hydrogeology

The project site is located in a zone that is already subject to saline water intrusion. No

groundwater exploitation is carried out in the region.

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5.6 Habitats of Flora and Fauna

The proposed site is covered with grass, shrubs and occasional trees comprising eucalyptus,

acacias and flamboyants. Plate 2 illustrates the vegetation cover available at the projectsite.

There is no flora and fauna of environmental interest on the project site. There are no

protected trees of any kind on the site.

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National Housing Development Corporation LUXCONSULT (Mtius) Ltd

Fig.5.2: Surficial Geology at and in neighbourhood of project site

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Fig.5.3: Soil Type at project site(Source: Giorgi, L., Borchiellini, S. and Delucchi L. (1999) La Carte Geologique de L’Ile Maurice au 1:50,000 – Le Schema Hydrogeologique, Water Resources Unit, Mauritius).

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Fig.5.4: Location of Trial Pit

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Fig.5.5: Summer and Winter temperatures (Mauritius)

Approximate Project Area LocationMean temperature

(January and July) 1961 - 1990

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Fig.5.6: Summer and Winter Rainfall (Mauritius)

Approximate Project Area Location Average Rainfall

(Winter and Summer 1961-1990

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PLATE 1

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Plate 1(a): Trial pit log profile to 3m depth

0.0 – 0.5 m

Brown sandy SILT with fine roots. TOPSOIL.

0.5 – 3.0 m

Firm, mottled reddish and yellowish brown slightly sandy SILT and

moderately weathered rock. RESIDUAL SOIL.

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Plate 1(b): Trial pit log profile to a depth 3m

0.5 – 3.0 m : Firm, mottled reddish and yellowish brown

slightly sandy SILT and moderately weathered rock.

RESIDUAL SOIL.

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PLATE 2

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