PHILADELPHIA - Years of urban decay are taking a serious toll on Philadelphia's once vibrant neighborhoods. Twenty-one buildings have collapsed since Thursday, and the city believes more than 3,100 others could fall down at any moment.
All of the buildings that collapsed were rowhouses in and around poverty-stricken North Philadelphia. All but two had been abandoned. As a result, only minor injuries resulted: Two men were hurt when a large wooden awning fell as they were walking by.
Experts are not sure exactly what caused the rash of building collapses but think it might have something to do with this summer's wet weather. Water can erode joints and weaken foundations, especially in houses with leaky roofs or inadequate downspouts.
''You would be surprised at how certain things such as having a downspout on your house, having your roof inspected - that is what keeps these properties from collapsing,'' said Andrea White of the city's Department of Licenses and Inspections.
The problem, though, was years in the making. Philadelphia's housing stock has been deteriorating for three decades, largely the result of a population exodus that cost the city 550,000 residents. Philadelphia is now down to 1.4 million people.
City officials said Philadelphia now has about 20,000 vacant lots and more than 30,000 vacant houses. Of those, more than 3,100 are classified as ''imminently dangerous,'' or in immediate need of demolition.
City inspectors plan to use helicopters Tuesday to assess the extent of the problem and look for telltale signs of buildings in danger, such as rainwater pooled on roofs and trees growing wild from the tops of houses.
The city also plans to step up demolition from about 30 buildings a week to as many as 60. The cost ranges from $6,500 to $11,000 per building.
''We're trying to get a better handle on what condition the buildings are in, which is why we're going to overfly the buildings. A lot of times you can tell if you can see the roofs,'' said Barbara Grant, a spokeswoman for Mayor John F. Street.
The mayor, who has been in office since January, made a $250 million blight-removal program one of the centerpieces of his campaign. It has yet to get off the ground, but aides promised the money will be in place by fall.
In the meantime, Licenses and Inspections has been using what it calls ''curbside demolition'': When an inspector determines a house is about to collapse, the city asks demolition companies to submit bids on the spot. The low bidder begins work immediately.
From her stoop across the street, Velma McDuffy watched intently Monday afternoon as an excavating machine tore into the remains of two collapsed rowhouses. The abandoned buildings caved in last week, adding another sad chapter to the gradual, decades-long decline of McDuffy's North Philadelphia neighborhood.
''I remember everybody that ever lived there,'' said McDuffy, a 42-year resident of the block, motioning toward what is now just a heap of rotted wood, insulation and bricks.
Tony Pullins was overseeing the cleanup in McDuffy's neighborhood. His company has lined up 10 or 15 demolition jobs, with the promise of many more to come.
''There's plenty of work. We'll be doing this for the next 10 years,'' he said.
Residents were thankful nobody was hurt. McDuffy said a busy bus stop is right in front of where the buildings collapsed.
An after-school center at the end of the row has been forced out until the city determines whether it is safe to go back.