"It became obvious that we could not continue to do assessments in the way we've done them in the past," Negrin said in an interview.
Until late last year, the BRT was out of the reach of the mayor, run by an independent board appointed by the city's judiciary.
But in December, after a series of Inquirer reports documented widespread mismanagement and cronyism at the agency, the board agreed to cede much of its authority to the Nutter administration. City Council has passed legislation that will replace the BRT with two new entities Oct. 1, contingent on voter approval in the May 18 primary.
Between now and then, Negrin said, the BRT's top focus will be cleaning up its data.
He said the agency too often gets basic facts about properties wrong, such as lot size or how many stories a home has. Some other data are too old to be reliable.
Such errors are compounded when used in modern mass-appraisal systems such as the one the BRT hopes to adopt as a replacement for its current set of inaccurate and inequitable assessments.
"It's your classic garbage-in, garbage-out scenario," Negrin said.
Given that, Negrin and Nutter said, the only fair thing to do is to keep property values at their current levels until the data can be corrected through a citywide reassessment.
The moratorium will have the effect of freezing property taxes through at least the 2011 tax year unless City Council raises the property-tax rate, which is highly unlikely.
There will be some exceptions, such as new construction and rehabilitated properties.
And, notably, the 18,000 city properties that received reassessment notices in 2009 will still be on the hook for their higher assessments.
