A federal judge in Texarkana has approved an agreement between the U.S. government and the company responsible for cleaning up and monitoring one of Texarkana’s Superfund sites.

The final court action comes about 15 years after a government buyout of homes and the relocation of residents in the Carver Terrace subdivision. Carver Terrace was built on top of the Koppers wood treatment site, just south and west of downtown Texarkana.

U.S. District Judge David Folsom signed a “final consent decree” near the end of last month. The order approving it was unopposed by Beazer E...