Name of the Project
Gross Reservoir expansion project.

Location
Denver, Colorado, in the US.

Project Owner/s
Denver Water.

Project Description
The project is a major component of Denver Water’s long-term, multipronged approach to deliver safe, reliable water to the more than 1.4-million residents in the service area currently, and many of the projected 7.7-million who will call Colorado home by 2040.

The project will raise the height of the existing dam by about 40 m, which will allow for the capacity of the reservoir to increase by 9.5-million cubic metres.

The dam will be raised with what is called a downstream buttress raise, where the new concrete will be placed on the downstream face of the dam from the bottom up.

The existing dam surface will then be prepared for new concrete to be added, this will be using high-power water jets.

Crews will excavate rock at the base and abutments of the existing dam to prepare the foundation to support the expanded dam surface. Concrete will be produced in an on-site concrete batch plant from the locally sourced raw materials and conveyed to the dam site where it will be added to the structure using roller compaction.

In addition to the main dam expansion, a new auxiliary spillway will be added to process extreme flood events.

Additional modifications to accommodate potential flood events will be required at existing overflow outlets as well.

The final phase involves the removal of trees and brush from the new inundation footprint.

Potential Job Creation
Not stated.

Capital Expenditure
The estimated cost at completion is $464-million.

Planned Start/End Date
The project is awaiting a final approval from the Federal Energy Regulatory Commission. Provided the remaining federal approvals are awarded by the end of this year, the project is slated to be complete in 2025.

Latest Developments
Denver Water’s five-member board of water commissioners has approved a two-year, $4.5-million contract with joint venture Kiewit Barnard for the planning and preconstruction work during the final design phase of the Gross Reservoir expansion project.

Denver Water has said that if the team’s performance during the planning and preconstruction phase meets its expectations, a separate contract to build the dam may be signed.

Key Contracts and Suppliers
Kiewit Barnard (planning and preconstruction work for the dam).

On Budget and on Time?
Too early to state.

Contact Details for Project Information
Denver Water, tel +1303628 6348 or email grossreservoir@denverwater.org.