British Columbia has amended the conditions of its environmental assessment certificate for the Trans Mountain pipeline expansion and told the federal government it still has concerns about its response to potential marine oil spills.

The changes announced in late February focus on the impacts of marine shipping and potential oil spills from ships related to the pipeline project.

The expansion is set to nearly triple the capacity of the existing 1,150-kilometre pipeline that carries 300,000 barrels per day of petroleum products from Alberta to B.C., which will significantly increase the number of tankers carrying oil for export.

In a letter relaying B.C.'s updated conditions, Environment Minister George Heyman and Energy Minister Bruce Ralston urged federal Natural Resources Minister Jonathan Wilkinson to adopt a series of recommendations that would address the province's concerns after it consulted with Indigenous nations, municipalities, government agencies and the public.

Those concerns would be most effectively addressed by Ottawa as part of the regulations and measures that fall under federal jurisdiction, Heyman and Ralston wrote in the letter, dated Feb. 24.

B.C. has made changes that are under its jurisdiction and sought to avoid duplicating existing federal regulations, the province said in a news release.

One of B.C.'s recommendations encourages Transport Canada to "expand the scope of its oversight" to include work done by the Western Canada Marine Response Corp., which responds to spills. In particular, it says Transport Canada's oversight should include shoreline cleanup, planning for sunken and submerged oil, co-ordinating volunteers, and managing wildlife and waste in the event of a spill.

"We strongly urge you to carefully consider these important recommendations, and to take action on them ... as soon as possible, so that the (Trans Mountain expansion) is operated in as safe a manner as possible," the ministers wrote.

Among B.C.'s new conditions is a requirement that Trans Mountain, a federal Crown corporation, provide a report on health risks in the event of a marine oil spill. It must identify measures to reduce human exposure and negative health effects and outline which authorities would be responsible.

Another condition requires Trans Mountain to provide a report with baseline data on B.C.'s shoreline in areas that could be affected by an oil spill, including Vancouver's English Bay and the Strait of Georgia. The report should include information on land use, infrastructure, flora and fauna, the order says.

The province has also amended a condition to require updates every five years on research Trans Mountain is involved with related to diluted bitumen and how the heavier, unrefined oil product could be cleaned up if spilled in water.

A Trans Mountain spokesperson said it is reviewing the changes to determine next steps.

Neither Wilkinson nor anyone from his Department of Natural Resources was available to comment on the provincial government's request.

Andrew Radzik, an energy campaigner with the Georgia Strait Alliance, said the province's changes are welcome, but gaps remain.

"If a spill happens, we've got better baseline data. So that's great, that's important. That's information that will inform spill response plans," he said in an interview.

"But they're not requiring shoreline spill response plans of a particular standard."

Instead, the province is relying on federal regulations on marine shipping and spill response that it has criticized for being too vague, Radzik said.

Transport Canada requires certified marine response organizations to treat 500 metres of shoreline per day and the Western Canada Marine Response Corp. has indicated it's working to increase its capacity to 3,000 metres.

But the existing regulations and emergency plans for the pipeline expansion lack some key detail, Radzik said, like what exactly it means to fully "treat" a shoreline.

The province shares jurisdiction along its shoreline and it could have amended the project's certificate to require more specific information or standards, he said.

On human health risks, Radzik said it's a step forward for B.C. to require an outline of the roles and responsibilities of different levels of government and the pipeline operator in reducing exposure after a potential spill.

However, it's not clear who would foot the bill for those health measures and what portion the province would have to pay, he said.

Asked why B.C.'s new conditions didn't include more specific requirements for marine spill preparedness and response, the Environment Ministry said the changes reflect certain criteria it had to follow in its review.

The opportunity for B.C. to change its environmental assessment certificate stemmed from a 2018 decision by the Federal Court of Appeal. It found the National Energy Board, since renamed the Canada Energy Regulator, had incorrectly excluded marine shipping from its assessment.

The regulator reconsidered the potential impacts, and the federal government used the subsequent report in 2019 to approve the pipeline expansion for a second time.

The B.C. Court of Appeal later decided that because the provincial ministers who issued the environmental assessment certificate had relied on the regulator's original assessment, they should have the opportunity to consider the later report and make changes, provided the issues related to differences between the two reports and fell under provincial jurisdiction.