A halt has been called to an attempt by Canada’s biggest oil refinery to avoid looming pipeline cost increases for switching Canadian East Coast natural gas markets over to imports from the United States.

The National Energy Board (NEB) rejected, as “premature,” a discounted toll “load retention service” that Maritimes & Northeast Pipeline (M&NP) proposed for delivering U.S. shale gas to Irving Oil’s 313,000 b/d Saint John plant in New Brunswick.

The ruling observed that during a lengthy review of the plan, “significant broad concerns and uncertainties were raised about the future of the natural gas market in the Maritimes and the impact on shippers, in particular those captive to M&NP.”

Devising solutions was postponed for a later, larger case. The NEB said “an examination of possible alternative toll and tariff approaches would be more fruitful when M&NP’s supply, markets and contract billing determinants post-2019 are known.”

The main “determinant” is declared intentions to plug and abandon Atlantic Canada’s aging, depleted and expensive subsea production networks: the ExxonMobil-operated Sable Offshore Energy Project (SOEP) and Encana Corp.’s Deep Panuke.

A target date of 2021 has been set for completing the cleanup by removing all traces of the facilities, with well plugging scheduled to start this year. SOEP intends to file a formal work application soon. Encana is recruiting cleanup contractors.

The provincial governments in New Brunswick and Nova Scotia have ruled out replacing offshore gas with supplies from wells on land. Both have enacted popular bans against “fracking” their shale deposits with horizontal drilling and hydraulic fracturing. Neither has responded to an earth sciences reminder, in a new geological atlas, that they have the shale resources to build a multibillion-dollar industry.

The supply loss confronts Canada’s Atlantic seaboard market with covering costs of switching to imports from the U.S. by reversing flows on M&NP. Expenses are expected include a high level of excess capacity.

M&NP chiefly delivered Canadian gas exports to New England. The combined gas consumption of New Brunswick and Nova Scotia, currently about 175 MMcf/d, is less than one-third of the M&NP system’s capacity.

The NEB rejected claims that M&NP had no choice but to grant the Irving refinery a reprieve from the looming cost increases because a bypass delivery route was available and would not require extensive construction or regulatory approvals.

The foiled deal rested on predictions that gas flows via a parallel conduit — Emera Brunswick Pipeline, built for exports from Repsol’s Canaport LNG terminal next door to the Saint John refinery — could be easily reversed for low-cost imports from the United States.

The NEB observed that evidence in the contested case showed that the rejected bargain would have given the refinery 13 years of delivery service for 65 MMcf/d for C$79 million (US$63 million) — which would have been a C$176-million (US$140 million) discount off current M&NP tolls.