David Von Spreckelsen, a vice president of Toll Brothers, said the company won’t be able to build its proposed Gowanus Canal project if the government decides to clean the canal up. The canal was named a possible Superfund site this week, which would allow the Obama administration to provide federal money for the clean-up. Von Spreckelsen said if the government decides to clean the canal, Toll Brothers’ adjacent land will have a stigma of being located on a Superfund site, and no one will want to invest in the property. The developer also said the company could not afford to wait for the clean-up to be finished. Toll Brothers received approval for the project last month and is expected to break ground this year, but typical Superfund clean-ups take 15 years, Von Spreckelsen said.