The City Council on Wednesday considers a proposal by councilors Matt O'Malley (West Roxbury/Jamaica Plain) and Michelle Wu (at large) to ban most plastic bags in Boston and to let stores charge 5 cents for paper or reusable bags - or plastic bags that can be composted.

O'Malley and Wu say the ban would reduce the scourge of plastic bags that now infest and clog local trees, waterways, vacant lots and storm sewers, reduce the amount of greenhouse gases created by their manufacture - and save the city money because it would no longer have to pay for dispose of an estimated 20 tons of plastic bags a month.

Under their proposed ordinance, stores could be fined up to $100 every time they're found using the thin plastic bags that would be banned. Store owners would be able to apply for a one-year hardship exclusion from the law - for example, if they had a large inventory of the bags when the ordinance goes into effect.

The council's Wednesday hearing begins at noon in its fifth-floor chambers in City Hall.

Proposed bag ordinance.

Report on bag hearings.