The Philadelphia City Council voted 13-3 to pass a bill Thursday that would decriminalize carrying small amounts of marijuana.

The ordinance, sponsored by Councilman Jim Kenney, would make possession of 30 grams or 1 ounce of the drug a civil penalty.

Currently, possession of that amount or less requires an arrest by police. Should the law be enacted, officers would confiscate the marijuana and issue a $25 fine, which could be paid right there online or by mail. If paid, the incident would be removed from the person's record.

Kenney told NBC10.com in May that Ordinance 140377 could cut down 17,000 hours of police time and save $3 million in booking and jail costs. The councilman added that it could take up to a year for a minor marijuana arrest to clear the city's criminal justice system.

Philadelphia's District Attorney, Seth Williams, has since 2010 sent those arrested for carrying 1 ounce or less of marijuana to a lower court without jail time.

Mayor Michael Nutter is not in favor of the proposal. His press secretary, Mark McDonald, said Nutter will consider the legislation and "will respond before the session in mid-September."

Approximately 4,000 people are arrested each year in Philadelphia for possessing small amounts of non-medical marijuana.

Representatives for the Philadelphia Prison System say the bill is unlikely to have a major impact on its inmate population. They estimate that fewer than 100 people in the Philadelphia Prison System are currently being held for simple possession.

If approved by Nutter, Philadelphia would join cities and states like Chicago, and Washington, DC who, in recent years, passed similar laws to decriminalize possession of small amounts of marijuana.

Kenney says he'll be sending a letter to Nutter urging him to sign the bill. Nutter could choose to sign or veto the bill at any time between now and Sept. 11 when the next city council session begins.