– Saying that Detroit needed to rid itself of its vast collection of dilapidated houses, junk-filled lots and empty shops, a task force examining the city’s blight said Tuesday that the price tag for the cleanup would be at least $850 million, including the likely demolition of 40,000 buildings scattered around the city.

The price tag came in a report by the Blight Removal Task Force, a group formed to catalog and find ways for Detroit to rid itself of the decay that has become one of the bankrupt city’s defining features.

The task force also suggested that the city must deal with the hulking factories that dot Detroit — crumbling reminders of the manufacturing prowess of a city far larger, wealthier and more vibrant than it is now.

The report warned that demolishing industrial structures would add hundreds of millions more to the cost, in part because of the need to remedy environmental degradation that the buildings have left behind.

The report — perhaps the most elaborate survey of decay conducted in any large city — found that 84,641 parcels among the city’s more than 377,000 properties are plagued by blight. Of those, some 40,000 buildings or parts of buildings should be torn down, according to the study.

“Detroit needs to act aggressively to eradicate the blight in as fast a time as possible,” the report concluded. “Other cities contending with high levels of blight have never addressed more than 7,000 structures a year. At that pace, it would take Detroit more than 11 years to address” its decaying buildings and rubble-strewn lots.

Five-year goal to eliminate blight

The report added that “because blight creates more blight,” the city’s deterioration would continue “without swift remedies.” It called for eliminating blight within five years.

The survey grew out of a task force convened in September by the Obama administration, which was seeking options as to how Detroit might remake itself after it became the nation’s largest city to file for municipal bankruptcy.

Despite concerns about the cost, city, state and federal officials, along with foundations and private business leaders, backed the remedy.

Kevyn Orr, Detroit’s emergency manager, said Tuesday that the city’s problem with blighted buildings had been mounting since the Depression and had been the subject of multiple studies by previous administrations.

The current report, Orr said, was finally an answer. “This is an unprecedented time and an unprecedented day,” he said. “Here we are, 83 years later, with the tools to address it.”

The data — a compilation of gloomy statistics about the state of the city’s real estate — was gathered by 150 resident surveyors and volunteer drivers who divided the city into quarter-mile squares, which were nicknamed “microhoods.” The front of each property was photographed and surveyors filled out forms related to the condition of each property. The information was then uploaded via a live-stream feed and confirmed.

The study revealed that 30 percent of Detroit’s parcels of land are now uninhabited — a total of 114,000 vacant lots.

The report defined blight, generally, as properties that are deemed a nuisance; that have been vacant for five consecutive years or more without being kept up to code; or that constitute a health or safety threat.

Plans to pay for half the cost

About 22 percent of the city’s parcels are troubled by blight, the study found, and of those lots with buildings on them, the percentage rose to 30 percent, according to the survey.

City officials said Tuesday that they have plans for how to pay for about $450 million of the massive demolition effort. Some of that is already dedicated federal funding. The bulk would come from the city’s pool of money that officials hope a federal bankruptcy judge will allow them to spend fixing the city. Still, that leaves the city nearly $400 million short, without even considering tearing down the old factories.

Among properties held by private homeowners, 53,500 parcels — or 23 percent of all privately owned lots — were deemed troubled by blight. But a far higher percentage — 93 percent — of the nearly 27,000 publicly owned parcels were found to be suffering from blight, the survey found.