The Justice Department has filed a consent decree in federal court in Salt Lake City that would fine the city of St. George $75,000 for dumping inadequately treated sewage wastewater into the Virgin River.

If signed by U.S. District Judge J. Thomas Greene after a 30-day public comment period, the decree would settle a federal lawsuit filed against the city last October.In addition to the fine, the decree includes the city's pledge to build a new sewage treatment facility by March 1, 1990, to bring its wastewater treatment system into compliance with federal Environmental Protection Agency guidelines.

The decree, which was worked out by St. George city attorneys and the U.S. attorney's office in Salt Lake City, will remain with the U.S. District Court clerk until the end of the 30-day period, which concludes March 28. At that time it will be formally filed and submitted to Greene to be signed.

The lawsuit contends that the city failed to meet federal deadlines for the construction of new treatment facilities.