Cavern wells, last vestiges of Alton Gas project, to be capped, site decommissioned by June

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The three wells drilled to support the ill-fated Alton gas underground storage project will soon be capped and the site decommissioned.

The cavern site was partially constructed on 80 hectares of property in a residential area of Brentwood Road, near Alton and between Stewiacke and Brookfield, in Colchester County.

The property was purchased by Alton Natural Gas Storage LP, a subsidiary of AtlaGas, several years ago, the wells were drilled and a building was constructed at the site to facilitate industrial, mechanical and electrical equipment, a nitrogen generator and compressor, three large water tanks and a brine storage tank, all surrounded by a chain-link fence.

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Controversial Alton natural gas project to be decommissioned

The cavern site was partially constructed but underground cavern development did not occur and the site was never put into operation.

To decommission the site, the company says Canadian Standards Association (CSA) standards will be followed in accordance with the 2021 decommissioning plan for Alton and under the oversight of the Nova Scotia Utility and Review Board, the regulator that approved the well decommissioning plan.

In the plan, the previously drilled hole at each of the three well locations will be plugged, filled with cement and capped. A service rig will be delivered by trucks to the cavern site in late May to do the capping work.

Once on site, the rig will be assembled and operations will take place approximately 12 hours per day, seven days a week from 7 a.m. to 7 p.m., for approximately three to four weeks.

Neighbours to the work site may see increased vehicle traffic and personnel as equipment moves to and from the location.

After years of sputtering between project starts and stops amid consistent opposition from environmentalists and the Mi’kmaq community at the river site and concerned property owners near the cavern site, several court cases and a bevy of high-profile protests, the company announced in October 2021 that the project would be terminated without a smidgen of salt brine discharged from the river and no caverns carved out.

In its decision to decommission the project, the company cited a repositioning to natural gas projects on the west coast of Canada and in the United States and a 2020 financial review that determined the project would be "economically challenged."

The economically challenged project had already cost the company in the range of $75 million, with an estimated $130 million allotted several years back to cover the project's first phase that included the river brining operation and the development of the caverns.

The goal of the first phase of the project was to draw nearly 10,000 cubic metres of water daily from the Shubenacadie River estuary at Fort Ellis and propel it through a 12-kilometre underground pipeline to the cavern site on Brentwood Road. There, the water would be pumped nearly 850 metres underground to flush out the salt beds to build the huge storage caverns.

The residue salt brine would be piped back to the estuary site for release into the river system, a gradual discharge of 1.3 million cubic metres of salt over a two- to three-year period.

Following all the well decommissioning work, the rig will be demobilized and trucked away, the company release said.

At the project's river site, activity to remove buildings and built features such as water storage ponds has been completed and restoration of the site is underway.

Restoration includes seeding the dike and regrading areas to promote natural reclamation and return the site to its original use as much as possible per the approved plan to decommission the Alton project.

That plan, unveiled by the company in December 2021, included an overall approach to "remove above-ground structures, leave buried components in the ground and reclaim land to equivalent land capability."

The plan included a public feedback phase.

The plan was that, pending regulatory approval to proceed, the "decommissioning and reclamation activities of the project" were to start in the spring of 2022 and follow a project abandonment plan created for a 2007 environmental assessment process.

The 16-hectare site (roughly the size of 40 football fields) on the Shubenacadie River estuary consisted of two buildings, a large pumphouse and a smaller electrical building, a channel dug in 2014 to divert river water, a replacement dike on leased Crown land, a gabion wall for water intake, two storage ponds and buried piping.

The company decommissioning plan was to salvage equipment, dismantle and remove the buildings, drain the ponds and regrade the land under the buildings and at the ponds to be consistent with surrounding conditions.

Components of the gabion wall above the high-water mark were tol be removed and the elevated dike will remain in place. The diversion channel, having already infilled naturally, was to remain and the company maintains that the development of a salt marsh in the abandoned channel is an asset for reclaiming the site.

Piping and valves buried at a depth of more than 1.2 metres below the surface were to remain abandoned in place and pipes that are above that depth will be removed.