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10.6 Underground Water, Surface and lagoonar Waters
and Irrigation Water

The EIA report provides a review on the ground water and sensitive water bodies in
the vicinity of the Project site.

The review mentions the presence of small wells used for agricultural purposes and even provides a list of wells located within a5km radius of the Project Site52. The lack of impact analysis on the possible contamination of the underground water on the agricultural activities dependent upon water from these wells tends to confirm the lack of consideration towards the existing communities in the vicinity of the Site.

Furthermore the report fails to identify that:

í²ƒ The Project Site forms part of the Rivière Belle Eau Catchment zones and its ultimate connection to the marine environment of Petite Riviere Bay;
í²ƒ The aquifer within the Project zone is also exploited for potable water supply to various regions including Port Louis;
í²ƒ The presence of numerous springs downstream of the Project Site and their importance to the local communities.

The importance and pertinence of the above points can be assessed from the following sections.

10.6.1 Rivière Belle Eau

La Chaumière Site is within the catchment zones of Rivière Belle Eau. The catchment’s area Riviere Belle is estimated at 41.2km2 and coded V by the CWA.

Rivière Belle Eau springs in the Bosquet area although its catchment goes back as far up as Beau-Bassin. It receives water from a pond - erected at Le Bosquet - and into which the Bosquet Springs flows. River Bell-Eau is thereafter diverted into La Rosière canal and it is almost dry. Its catchment displays a number of springs such as Gros-Cailloux Springs, Trublet Springs and at least three other springs (not named) and which would normally contribute to the natural flows of the river, if they were not heavily tapped by riparian owners. Rivulet Cabot, the major tributary of River Belle-Eau, does not contribute to that natural flow as all its waters are diverted by Médine S.E. for the purpose of irrigation.

Upon approaching the sea, whatever is left of River Belle-Eau flows, carves its course due south west in the littoral sand formation of Petite-Rivière Bay53, with the formation of ponds of brackish water lined with reeds with a few scattered mangrove specimens.

During the rainy season the situation changes dramatically as the river swells considerably.

Petite-Rivière Bay is nowadays an important tourism development zone with the construction of Club Med Hotel. The Albion public beach has become an important recreational ground not only for the local inhabitants but also for the inhabitants of lower Plaine Wilhems.

10.6.2 Potable Water Supply and Springs in the
Vicinity of Project Site

The water resources of the Western Coast have been reviewed extensively in a study 54 financed under the Montagne Jacquot Environmental Sewerage and Sanitation Project. The relevant data pertaining to the Project Site and its immediate vicinity are given below.

The Curepipe Aquifer flows to the Western Coast both north and south of the
Corps de Garde Mountain. North of the Corps de Garde, Le Bosquet Service
Reservoir (storage capacity: 3 373m3) receives water from:

• Pierrefonds Tunnel;
• Le Bosquet and Petite Rivière bore-holes, whose aggregate yields fluctuate
seasonally between 4 800 m3/d and 5 400 m3/d;
• St Martin bore-hole which was specifically equipped to supply the Coromandel Industrial Estate with some 2 400 to 3 000 m3/d.

Le Bosquet Service Reservoir supplies potable water to Albion, Petite Rivière,
Pointe aux Sables, Richelieu, Coromandel, Cité Vallijee, Grande Rivière and
Caudan.

10.6.3 Springs

A number of springs also exist not far from the Project Site:
• St Antoine Springs (S8)
• Le Caprice Springs (S6)
• Gros Cailloux Springs (S2), at the head of Rivière Belle-Eau
• Tiabouc and Le Bosquet springs, situated within Gros Cailloux Estate.
St Antoine Springs with a safe yield of 10 000m3/d is used by Medine for irrigation purposes. This spring has been identified as a potential source of potable water for Port Louis.

The Gros Cailloux Springs with a normal flow of 141.6l/s (~12 000m3/d) is also an important source of water presently used for agricultural purposes.

10.6.4 Irrigation Water: Availability of Treated Effluent from St Martin Wastewater Treatment Plant

The St Martin Waste water Treatment plant treats the wastewater from the Upper Plaines Wilhems as well as the regions of Lower Plaines Wilhems such as Beau Bassin.

The St Martin Wastewater Treatment Plant has necessitated investments of more than Rs1 Billion and was funded in part by a grant from European Union (8th EDF) and by the Government of Mauritius (GoM).

The Plant has been designed to produce treated effluent suitable for irrigation purposes. The Plant has a design capacity of 69,000m3/d with a tertiary treatment
phase with disinfection using Ultra Violet Technology.

At present St Martin WWTP is treating about 25,000-30,000m3/d. The wastewater
flow will increase to the design flow in the future as Government of Mauritius is investing in sewer reticulations and household connections for the urban regions of Plaines Wilhems. This investment programme is estimated at Rs 3Billion.

Hence with a total investment of about Rs4Billion, St Martin WWTP will produce 69,000m3/d of treated effluent suitable for reuse as irrigation water. At present St Martin WWTP is already producing about 25,000-30,000m3/d.

Thus treated effluent from St Martin WWTP has the potential to replace underground water presently used for irrigation.

It must be noted that there are two major irrigation water conveyance systems in the vicinity of Site, namely: La Ferme Canal and Magenta Canal.

10.6.5 Potable Water Supply Potential

From the previous sections, it is apparent that with the coming into operation of the St Martin Wastewater Treatment Plant (capacity: 69,000m3/d) designed to produce treated effluent suitable for irrigation, the springs used for irrigation purposes at present have the potential to supply potable water to the fast developing areas of Albion and its vicinity as well as other potable water stressed areas of Lower Beau Bassin, Port Louis South and its environs.

For example the St Antoine Springs with a safe yield of 10 000m3/d has been identified as a potential source of potable water for Port Louis.

The Gros Cailloux Springs with a normal flow of 141.6l/s (~12 000m3/d) is also an important source of water presently used for agricultural purposes.

10.6.6 Conclusions

The review of the groundwater and surface water as given in the EIA report is severely flawed at best as it fails to report that the local aquifer is exploited not only for agricultural purposes but also as potable water supply.

Furthermore the EIA report does not recognize that in the event that the aquifer is contaminated due to activities pertaining to the operation of the proposed WTE Plant, the use of water from the aquifer for irrigation purposes will have to be discontinued as contaminants such as Dioxins and Furans as well as heavy metals will enter the food chain. This will threaten the livelihood of the vegetable
growers and farmers of the region.

The construction and operation of a hazardous landfill on such an important aquifer is a major threat to the future development and mobilisation of additional water resources and the risks of water pollution (underground and surface) has not been evaluated using reliable data contrary to the statements made in the EIA report.

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52 Annex 1 of the EIA Report
53 SIGMA and SOGREAH Consulting Engineers: Étude d'un Schéma Directeur d'Aménagement des Eaux à l'Ile Maurice. Étude Hydrologique. Volume 1. Hydrologie de Surface. September 1981
54 Waste Water Authority (1997): The study on sanitary, Technical and Economic Viability of the Reuse of treated Effluent for Irrigation Purposes – BRL Ingenierie

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