Marathon Petroleum's request to avoid covering a petroleum coke storage pit in southwest Detroit has been denied.
Detroit's Buildings department says the company failed to show that people living near the refinery would not be affected by emissions.
Petroleum coke — also called pet coke — is a byproduct of refining crude oil.
Marathon says the pit is surrounded by 30-foot-high walls and that it isn't necessary to install a covering to meet emission reduction requirements.
The city says refinery officials "offered no analytical data or air monitoring data of any sort that would conclusively show that there are no fugitive dust emissions from the coke pit, among other things."
Marathon spokesman Chuck Rice says the company is reviewing its "options in light of the city's decision."
Nearby residents long have complained about pollutants from the refinery.
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