Why did the cleanup of superfund sites began lag after 1995

Superfund was a United States federal law designed to clean up the sites that contaminated with hazardous substance and pollutant.

So, basically the Government collect funds from various companies that is seemed to be responsible for the substance and pollutant and use it to clean up the environment.

By 1995, the Government manage to collect about 4 Billion, but somehow the congress did not authorize to collect these fund without any clear explanation, and by 2003, the fund was empty