Nassau County executive Edward Mangano told members of the Long Island Real Estate Group that the county's "broken" property tax assessment system must be fixed and is the single greatest challenge facing his administration. Speaking at a March 3 meeting of the networking and philanthropic group at the Old Westbury Country Club, he said tax assessment is a priority for his new administration. "We have to reform that system," Mangano said. He explained to the 150 members in attendance that Nassau's assessment system generates about 100,000 tax grievances a year as well as nearly $100 million in refunds a year. As a result, he said, the county loses $250 million annually - about 10% of its annual budget - because of mistakes in taxing Nassau property owners. He said the county employs more than 300 people to correct assessment errors. Mangano said he favored a reduced scope for the Lighthouse in Uniondale, proposed by a joint venture of RXR Realty Corp. and New York Islanders owner Charles Wang. He said the administration would revisit Steel Equities' plan to acquire 100 acres in Bethpage formerly owned by the U.S. Navy. He said he supports an acceptable level of development at both sites that will bring much needed jobs. "In this struggling economy, we have to get real," Mangano said.