Heavy rains and subsequent flooding last weekend caused Thunder Bay to declare a state of emergency earlier this week.
The request to the province is the first step in the process to apply for funding under Ontario's disaster relief assistance program.
Some homes and city structures were flooded and sewer systems overloaded as parts of the city got more than 100 millimetres of rain.
Roads and trails also were damaged by the heavy rain, including sections of the Trans-Canada Highway that were washed out.
Pump failures at Thunder Bay's new sewage treatment plant caused hundreds of basements to flood.
Residents are being asked to avoid flushing toilets or sending water down the drain until the situation is addressed, and to conserve water.
City official Darrell Matson said Thursday that crews still haven't been able to examine the crippled sewage treatment plant.
However, Matson said the pressure on it is easing somewhat because the water levels in city sewers are starting to decrease.