Water tunnel to increase national reliance on desalination

The proposed water tunnel aims at reducing the amount of groundwater abstracted – the process to take out the water – to reduce the impact on the water table, and increase the amount of reverse osmosis mixed into the blend

The share of groundwater in Maltese tap water is set to decline further as a result of a proposed 9km underground tunnel that will channel water from the Pembroke Reverse Osmosis plant to a reservoir in Ta’ Qali.

Groundwater accounts for 43% of Malta’s drinking water, down from over 50% before 2000.

The water supply consists of a mix of extracted water from the groundwater aquifer, and desalinated sea water through reverse osmosis.

The proposed water tunnel aims at reducing the amount of groundwater abstracted – the process to take out the water – to reduce the impact on the water table, and increase the amount of reverse osmosis mixed into the blend.

But this will also increase Malta’s dependence on the more energy-taxing reverse osmosis (RO) water.

The quality of Malta’s groundwater has been deteriorating over the years due to over-extraction and pollution from farms, necessitating that it be blended with RO water to reach EU standards.

A reply to a parliamentary question in 2008, before the reduction in energy tariffs in 2014, had established that while it cost €13 to derive one cubic metre of water from the water table, it cost the Water Services Corporation €49 to produce the same amount of desalinated water.

Groundwater, which today
accounts for 43% of drinking water, is cheaper to produce as it is less energy consuming.

An Environmental Impact Assessment for the Pembroke tunnel fails to quantify the increased energy costs which will come as a result of increasing reliance on RO water. According to the same EIA, since the infrastructural upgrade will involve the replacement of old pipes with new ones. The project is also expected to bring about a reduction in the current leakages, which are estimated at 200,000 cb.m per annum.

With less water being wasted, energy costs are also expected to decrease, the EIA states.

Energy costs will also be reduced by lower pumping and electrical costs through a design which relies more on gravitational flows than on pumping.

The EIA describes the extraction of groundwater as “unsustainable” and one which is “straining the Maltese aquifer systems”.

It refers to “the issue of uncontrolled illegal extraction which leads to increased salinity levels within the aquifer.”

Ironically the problems of over extraction are also the result of rampant private extraction from boreholes. In fact it is estimated that more water is extracted by private operators like farmers than by the Water Services Corporation, which is the only body licensed to extract this water.

The EIA concludes that groundwater is of “lower quality than RO water, since this originates from the water table and tends to possess higher impurity and nutrient levels.”

Moreover, aquifer deterioration is also the result of nitrates resulting from slurry from livestock farms and the use of fertilisers.

Better water quality water for central Malta

Presently the water supply which feeds central Malta, which includes major urban centres like Birkirkara, mostly consists of groundwater which is temporarily stored in the Ta’ Qali reservoirs.

On the other hand the water supply feeding the North Harbour area which includes Pembroke, St Julian’s, Sliema, Swieqi mostly originates from the RO plant in Pembroke.

Currently, the Pembroke RO directly feeds the North Harbour area (Sliema, St Julian’s, Swieqi and San Gwann areas), before going through the Ta’ Qali group of reservoirs.

That means that water distributed from the Ta’ Qali reservoirs is of inferior quality due to the low proportion of RO water in the blend. This will be resolved by supplying RO water directly to the Ta’ Qali reservoirs which will then feed the other reservoirs across Malta.

At Ta’ Qali, water will be blended with groundwater fed from the Naxxar reservoir and injected with a formulation of chemicals, to attain the desired blend.

This water will be then distributed to other reservoirs across Malta such as Fiddien, Naxxar and Qrendi. Neighbouring areas of San Gwann will be fed directly through the Misraħ Lewz, a reservoir which will be fed via the Ta’ Qali reservoir through another underground side-tunnel.

122,000 cb.m of construction waste

The project us expected to generate 122,000 cb.m of construction waste which amounts to nearly a tenth of construction waste generated in 2015.

The EIA concludes that most of this material cannot be recycled, and thus the impact is considered to be adverse and irreversible. 4,100 truck trips will be necessary to transport all the excavated waste during the 20-month excavation phase.

During the construction phase, natural areas including the Natura 2000 site in Pembroke may also be affected by noise disturbance and dust emissions.

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