Lower South Platte River Study

• Contractor Name: Colorado Water Conservation Board
• Loan Projects - Doc Type: Feasibility Study

Lower South Platte River Study
Colorado Water Conservation Board
' December 2001
' Permitting challenges will need to be addressed for developing any of the storage sites.
Wetlands issues will be most significant for the Julesburg Enlargement. At the Ovid site,
wetlands appear to be linked to the presence of irrigation water. If proved to be linked to
' irrigation, the Corps of Engineers may not view them as jurisdictional. At the Johnson site,
the wetlands appear to be isolated and not jurisdictional. At the Harmony West site, the fact
that the drainage channel flows into the Harmony Ditch may show no direct linkage to waters
of the U.S., thereby avoiding a jurisdictional wetlands issue. For several sites, it may be
possible to avoid federal involvement in permitting under Section 404 of the Clean Water
' Act. Further, more-detailed wetland surveys and consultation with the Corps of Engineers
will be required to make this determination.
The study team makes the following recommendations for implementation of a water
management project in the Lower South Platte River Basin:
' 1. Firmly establish the quantities of additional water needed in the Lower Basin to meet
augmentation and instream flow management objectives.
2. Conduct additional discussions with the North Sterling Irrigation District, Julesburg
Irrigation District, and co-owners of the Harmony Ditch relative to use of existing
' conveyance facilities to fill a new storage reservoir and potentially convey flow from
a new reservoir. Establish a"carriage charge"that can be used in the financial
analysis of a preferred project.
3. Working with the Groundwater Appropriators of the South Platte(GASP) and water
' users in the Lower Basin, establish a feasible sales price for water produced by a new
project and identify the basic framework of a contract for purchase of the water.
4. Conduct a feasibility-level study of the project, focusing on the alternatives identified
in Section 5 of the reconnaissance report. This study would include:
' • Geologic and geotechnical field investigations of the most-attractive storage sites,
including subsurface investigations of the most-promising sites.
' • Hydrologic studies to establish inflow design floods for dam and reservoir design.
' • Refinement of the NCWCD water availability studies, as needed, to support an
eventual water court filing for the project.
• Refinement of the reservoir and system operations studies, focusing on specific
alternatives and incorporating improved estimates of seepage, evaporation, and
' other potential losses.
GEI Consultants, Inc. ES-5 01002 Dec 2001 Lower South Platte River Study