The bell is about to toll for Rikers Island, as the City Council plans to vote today on Mayor de Blasio’s polarizing plan to replace the scandal-scarred complex with four smaller, regional jails that will hold far fewer inmates.

The $8.7 billion proposal — which would put a mini-jail in every borough but Staten Island by 2026 — is expected to pass, as only 10 of the council’s 51 members are sure to vote no and roughly a dozen more are undecided.

De Blasio has made it a goal to reduce the number of inmates held in city jails as part of his vision for criminal-justice reform — and closing Rikers and building the new facilities is part of that.

The reduction in beds has some observers worried that dangerous criminals could wind up on the street because there is no place to keep them.

“We should be putting more people behind bars — not less,” said Councilman Robert Holden (D-Queens), who supports building a new prison complex on Rikers Island. “By cutting the prison population down with these smaller jails, the city is setting a very dangerous precedent. To put more killers and rapists out in public is playing Russian roulette with people’s lives.”

The proposal only got the final support that backers think it needed to pass thanks to a sweetheart deal hammered out earlier this week. The height of the new facilities will be reduced by an average of nine stories — thus slashing the combined number of beds in the jails by about a thousand, from 4,600 to 3,544.

Rikers, by comparison, can hold 15,000 inmates. There are about 7,000 defendants currently in the jail system, compared to 11,000 when de Blasio came into office in 2014. The drop has come amid a push by lawmakers and judges to reduce the number of pretrial suspects by giving low or no bail.

The mayor first announced plans to shutter Rikers in 2017 — though officials have yet to offer a concrete timeline for closing its 11 facilities on and off the 413-acre island.

The mayor believes the prison population can be trimmed to some 3,300 inmates by 2026 — the last time the city had this few prisoners was in the 1920s, when there were 3 million fewer people living in it.

Though the four-jail plan appears to be on the path to passing, opposition to the jails has come in many different forms — from those fearing criminals will run free to those not wanting unsightly jail towers in their neighborhoods.

Among the naysayers is Councilman Andy King (D-Bronx), who says replacing Rikers with more jails is a blow to the people who have to live near the new facilities.

“Something is wrong that we are pushing this through and disregarding the voices of New Yorkers when it comes to building borough-based jails,” King said at a City Hall rally Wednesday against closing Rikers.

“If we want to fix the criminal justice system, then let’s fix the criminal-justice system and be honest and true about us correcting that system — and not blame it on the brick and mortar of Rikers Island.”

Councilman Rafael Salamanca (D-Bronx) said he will vote no unless the city agrees to also close the Vernon C. Bain Center, an 800-bed floating barge used as a jail in his district, earlier than 2026.

The city’s correction officers, meanwhile, oppose the plan because they want Rikers Island improved now and don’t want to wait until 2026 for the new facilities to go up.

“My message to the Council is do today what you talking about doing in seven years,” Elias Husamudeen, president of the Correction Officers Benevolent Association, said. “Make the jails safer today.”

Despite the opposition, the council’s land use committee voted overwhelmingly Wednesday to green-light the proposal and send it to the council floor.

The four new jails are slated to be built on the site of the NYPD’s Bronx tow pound, at the now-closed Queens Detention Center in Kew Gardens and at the current sites of the Brooklyn Detention Complex in Boerum Hill and Manhattan Detention Complex in lower Manhattan.

Councilwoman Karen Koslowitz, who represents the area where the new Queens jail will go up, said this was the “hardest issue” she’s dealt with on the council.

“This was not an easy issue because people in my community that [I have worked with over the years] are angry because I’m voting yes on this,” she said.

She said she’s backing the measure because “it’s the humane thing to do.”

Council members also said they secured nearly $391 million in commitments for criminal justice-related reforms and community-based investments — $125.7 million of which is already budgeted.

Some $122 million will go toward projects ranging from affordable housing, health programs and new community centers.

If passed Thursday, the four-jail plan will head to de Blasio’s desk to be signed into law. Avery Cohen, the mayor’s spokeswoman, commented on the legislation: “Larger jails don’t mean safer cities. With crime at historic lows, New York City is proving firsthand that you don’t have to arrest and imprison your way to safety.”

Last week, the council’s land-use committee also backed a measure that would make it so Rikers could never be used to house a jail again after 2026 — by designating the island a public place. Those plans, however, face a lengthy land-use review process and, eventually, a full council vote.