INSIGHT: Why Jersey Water dropped its plans for La Gigoulande

Thursday 26 August 2021

A valley may have to be flooded after Jersey Water has dropped its plan to turn La Gigoulande Quarry and turn it into a reservoir...but why did they turn their backs on the "unique, once-in-a-lifetime" opportunity?

Last week, the company released its plan to meet an anticipated rise in demand for storage, primarily caused by climate change and an expected rise in the population.

But dropped from the report was the preferred option from its last ‘water resources and drought management’ plan of 2018 – using an existing hole at the St. Peter’s Valley quarry to store raw water. 

Using La Gigoulande was also the proposal it submitted to this year’s three-year bridging Island Plan, which will form the blueprint for planning policy from next year until 2025.

Pictured: La Gigoulande includes a 30m hole to the west of the site, which is partially filled with groundwater.

In October 2019, Jersey Water said: “The potential repurposing of La Gigoulande Quarry as a water storage reservoir, represents a unique, once in a lifetime, opportunity to secure a key piece of infrastructure for the benefit of the island that, if ignored, will never present itself again. 

“Filling the quarry with inert waste provides a temporary solution for solid waste management; filling the quarry with water provides a permanent water resource for the island for centuries to come.”

However, the Government has opted for waste over water at La Gigoulande, with the plan supporting the hole being filled in with inert material and the quarry also being controversially allowed to expand into a neighbouring field, MY966.

Now, in its latest water resources and drought management plan, Jersey Water is looking to increase capacity of the desalination plant, reduce leaks, improve efficiency, and extract more water from boreholes in St. Ouen’s Bay once they are free of a man-made contaminant once sprayed at the Airport.

Pictured: Jersey Water CEO Helier Smith: "We don't have the support of the States of Jersey or Granite Products for this".

But looking further ahead, the company say that flooding another valley, possibly Le Mourier in St. Mary, or extending an existing reservoir by heightening the dam, probably Val de la Mare, will be necessary to meet future demand for water.

Asked why the company was abandoning its plans to use La Gigoulande quarry, which it argues would hold almost as much water as Val de la Mare and go a long way to meeting the 42% increase in storage capacity that is needed by 2045, Jersey Water CEO Helier Smith said: “We thought there was an opportunity there to investigate its suitability as a reservoir for the future. We were obviously disappointed that that was not recommended within the bridging Island Plan, although we understand the reasons why not. 

“But the reality is, to use La Gigoulande as a reservoir would require the active support and involvement of both the current owners of the site and the States of Jersey, and at present - while we have a really good relationship with both - we don’t have their support for this.

“The other factor which is relevant is the current size of the hole wouldn’t be big enough to create a viable reservoir; it would require the hole to be much bigger than it currently is, and I understand that that is not the plan at the present, so there are technical and logistical aspects of the operation of the site that would prevent that from happening.”

The owner of the quarry, Granite Products, commissioned its own study for the Island Plan, which concluded that the “proposed storage volumes suggested [by Jersey Water] are not achievable”. 

The report, by engineering consultants, considered two approaches: allowing the existing 30m hole at La Gigoulande to naturally fill up with groundwater, and engineering the hole so it was isolated from groundwater. The first option could hold up to 225,000 m3 of water but this would be dependent on groundwater levels, which would be lowest at times of peak demand. 

There would also be a risk of seepage, contamination and overspilling, the consultants concluded.

They added that lining the hole with rock grout or concrete could store up to 240,000 m3 of water but would be expensive to do. The latter option, which would provide the most stable form of water storage, would also be technically complex.

If this option was chosen, the groundwater – which is currently supressed at the deepest part of the hole – would rise, causing “significant uplift pressure” on any lining. Therefore, groundwater pressure would have to be managed, which the report says would be a major engineering challenge. 

The proposed expansion of La Gigoulande into a neighbouring field, which is supported by the Island Plan, has been strongly opposed by islanders and some politicians, with Senator Kristina Moore lodging an amendment to remove support for it.

Pictured: The proposed expansion of La Gigoulande into a field to the south of the quarry has been strongly opposed by some islanders.

One resident, who wished to remain anonymous said: “I would think that most people, given the choice, would prefer the idea of a reservoir over filling in a hole in the ground with waste.

“Also, you can import aggregate but you cannot import water, so it would surely be of greater strategic benefit to the Island to use the site for water storage. Also, there is a question mark over the cost of importing aggregate, with some saying it could be the same price or even cheaper than on-island quarrying.

“Secondly, the Island Plan talks about the need for a ten-year “mineral landbank”. Well, Jersey has just 120 days of water stored so where is our “waterbank”?

“Do we import more aggregate or flood another valley? I think most Islanders wouldn’t want to see a place like Le Mourier Valley lost because of decisions made based on incorrect or out-of-date assumptions.”