US Army Corps of Engineers
Albuquerque District

Focus on Regulatory: Box Creek Reservoir

regulatory branch, Pueblo, Colo.
Published Nov. 8, 2018
A spring-fed wetland complex associated with Corske Creek (foreground) with historic placer mine tailings, and the remains of the historic Hallenbeck Ranch. (background).

A spring-fed wetland complex associated with Corske Creek (foreground) with historic placer mine tailings, and the remains of the historic Hallenbeck Ranch. (background).

A one-acre pond where Corske and Box Creek confluence with adjacent historic Box Creek placer mine tailings.

A one-acre pond where Corske and Box Creek confluence with adjacent historic Box Creek placer mine tailings.

The Southern Colorado Regulatory Branch of the Albuquerque District is located in Pueblo, Colorado. This office has been evaluating a request, by the city of Aurora, for an approved jurisdictional determination. The request is for an approximate 1,388-acre site known as the historic Hallenbeck Ranch. The ranch is located approximately 10 miles south of Leadville, Colorado. This site is anticipated to become the preferred alternative for future construction of a new reservoir within the Upper Arkansas River Basin.

Evidence of historic ranching activities can be found across the site. This included several historic structures, ditches, and old stream channels, which were used to grow hay. In addition to a long history of ranching activities, the site is the location of historic placer mining, where a significant amount of gold was removed from the site between the late 1800s and the early 1900s. Currently, several miles of mine tailing piles dominate the landscape, where natural stream channels once flowed, providing evidence of the magnitude of historic mining activities at the site.

Today, three main tributaries flow out of the mountains, to the west, and confluence on the project site, before flowing into the Arkansas River to the east. The city of Aurora has studied the ranch, and its surrounding areas, for years, to determine the extent of potential jurisdictional waters of the United States, as well as any 404 permitting that could be required, in order to build the reservoir. More than three miles of stream channel, along with undetermined acreage of abutting and adjacent wetlands, have been identified within the project area including several acres of potential fens. Fens are defined as low and marshy, or frequently flooded, areas of land.

If USACE determines that jurisdictional waters of the United States are present on the site, and the city of Aurora decides to move forward with the reservoir project, then Aurora will be required to apply for a standard individual permit, and USACE will be required to initiate an Environmental Impact Study.