The Diesel Emissions Reduction Act (DERA) authorizes the U.S. Environmental Protection Agency (EPA) to allocate funds to states for the establishment of clean diesel projects that will reduce diesel emissions in areas of concern using cost-effective projects. The amount of funding available for allocation and the project requirements can change from year to year.
DERA Grants are now administered by the Iowa DOT
Their page is at https://www.iowadot.gov/dera.