Should condo building project be maintenance & repair or a capital improvement?

I am a unit owner in a 40 unit condominium. Last year many of the first floor units experienced a severe sewerage backup event during one of the heavy rainstorms. The condo association is obtaining an engineering report to figure out the problem and hopefully solutions to the issue. In the meantime there is debate about whether the repair of the sewerage back flow issue would be considered maintenance/repair or if it would fall under the improvement category. The fear is that it will be a substantial cost to fix the problem. If treated as an improvement, 75% of the unit owners would need to agree to spend the money to repair/replace. If this is considered repair and maintenance then a vote would not be needed. Is fixing a sewerage backup issue considered maintenance or improvement? We know the condominium laws do not provide a description for either category. Thank you for your opinion!  Boston MA.