Dene Tha' leaders are to meet Monday with Apache Canada Ltd. officials in the remote community of Assumption.
Sidney Chambaud, a band councillor, said they want more information about what happened and what the company is going to do about it.
"There are wildlife impacts and water and land impacts," Chambaud said in an interview Thursday.
"Right now within that area the trees, the vegetation and the soil are dead. The water is contaminated."
The Energy Resources Conservation Board has said the spill of water containing salt, oil and minerals was first reported on June 1, but the board didn't learn about its size until Tuesday.
Chambaud said the 42-hectare spill is so large it raises questions about how long the pipeline that carries water used in oil and natural gas operations had been leaking.
He said some band members believe the pipeline had been leaking since the winter, but no one noticed it until earlier this month.
"There are indications that the spill occurred earlier, during the winter season, but due to ice and snow it wasn't discovered."
Chambaud said water from the spill has leaked into a stream that runs through a small aboriginal community and onto land used by band members to hunt and trap.
Alberta Environment has monitoring crews outside of Zama City looking at the effects of the spill.
Staff was taking water samples for testing and checking animals. An assessment of vegetation is to begin later this week.
The department said crews were removing water from the spill area and storing it in tanks. Culverts were being plugged to stop the spill from spreading.
Nikki Booth, a department spokeswoman, said Alberta Environment and the ERCB are investigating what happened.
"Alberta has some strict environmental laws," Booth said. "If we believe the law has been broken charges can be laid. But at this point in time this incident is still under investigation."
The spill prompted the New Democrats to call on the provincial government to release a report into the safety of Alberta's network of oil and natural gas pipelines.
Alberta Energy commissioned the study last summer following major breaches of oil pipelines owned by Plains Midstream Canada.
One spill last June near Sundre fouled the Red Deer River after about 475,000 litres of oil spilled.
Earlier this year the province charged U.S.-based company over an April 2011 breach near the community of Little Buffalo in north central Alberta following a spill of 4.5 million litres of oil.
"This government can't be trusted to protect our air and water," NDP member Rachel Notley said of the Apache Canada spill.
"It took the government and the ERCB more than 10 days to confirm the volume and affected area of the spill, and that response is simply unacceptable."
An Alberta Energy official said Thursday the pipeline safety review report will be released in the very near future, but declined to elaborate.
Apache Canada officials could not immediately be reached for comment.
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