City of Thornton v. City and County of Denver
Issued February 25, 2002

In 2000, Thornton filed a timely petition to the Water Court to invoke retained jurisdiction based on a stipulation that had been entered in an earlier proceeding regarding use of effluent for augmentation purposes by Denver, claiming that changes in the operation of the plant discharging the effluent had increased levels of contaminants, making the water supply unsuitable for Thornton’s normal use. The petition requested that the Water Court hold hearings on the necessity for modification of Denver’s Augmentation Plan. In the alternative, Thornton requested that the Water Court extend the period of retained jurisdiction until the resolution of another dispute between Denver and Thornton, which also concerned alleged injury to Thorton’s water supply by the use of the effluent as a substitute supply. The Water Court denied the petition without a hearing, noting that Thornton had stipulated to the use of the effluent by Denver. Further, the Water Court found that a better understanding of detrimental water quality effects of the effluent’s use in the augmentation plan was not intended to be the subject of the retained jurisdiction provision.

The Colorado Supreme Court overruled the Water Court, holding that the Water Court needed to address whether the actual operation of the augmentation plan, in comparison to the quality of supply it would otherwise receive, would cause injury. In the alternative, the Water Court should have extended the period of retained jurisdiction until the pending Denver exchange case could address the common water quality issues.

See the Supreme Court decision