Denver Water - Cheesman Dam Upstream Control Project - Phase 1

Surface diving operations being conducted on dam

Cheesman Dam is a primary reservoir for Denver Water who provides the potable water to Denver, CO and surrounding areas. Completed in 1905, it was built by Italian Master Masons using finely set and mortared granite blocks. Cheesman was a technological masterpiece and landmark of civil engineering for decades to come.

The Upstream Control Project, Phase 1, encompasses the replacement of three internal gate valves with new hydraulic valves to be located on the upstream face of the dam. The first step is to to upgrade the existing bypass outlets. The original bypass outlets, tunneled through the canyon wall for integrity, will be enlarged to accept new stainless steel spool pieces, one weighing 29,000 pounds and two weighing 14,000 pounds. These spool pieces will be moved just inside the canyon wall and secured in place with anchor bolts, drilled into the native material, and securely grouted to provide a leak free seal. The new stainless steel valves will then be mounted to the spool pieces and protected by trash racks which prevent rubble from entering the intake system.

To operate these new valves, a control structure will be built on the crest of the dam. This new structure will house the hydraulic pump unit and the controls which will operate the valves. To connect the hydraulic tubing to the valves, holes will be drilled into the dam, exiting into the reservoir next to the gates. One side of the hydraulic tubing will be installed into the holes secured in place with grout, and the other side of the tubing will be connected to the gate.

The diver's work platforms on the reservoir will be "flexi floats", segment-able barge units lashed together. These barges will support both a Surface Diving Spread and a complete Saturation System. A staging area will be constructed on the reservoir shore for barge mobilization and support for the duration of the operation.

The initial project tasks will include using an ROV to collect data on the site surveys. This data will be used to design and fabricate custom tooling which will assist in removing the existing valve structure, enlarge the by pass opening, position the new spool pieces, and assist with rock drilling.

Project Updates

April 13, 2010: Getting started

All of the submittals are in, plans approved and the ice finally melting - time to get to work! The barges have been assembled and a shallow water dive station set onboard, Global is beginning work on the Auxiliary Level gate. You can see the spool piece that will be installed inside the existing inlet opening, it will be installed inside the rock opening and anchored in place with 64 anchor bolts. A new hydraulically operated gate valve will be attached to the end of the spool. The entire opening will then be protected with a steel trashrack.

Once the Auxiliary Level Gate has been installed the barge will be brought back to shore, the shallow water dive station will be removed and a Saturation Dive Spread will be installed. The Mid and Low Level Gates will then be installed, similar to that done on the Auxiliary Level.

July 9 - 14, 2010: Saturation System Departs Seattle

Friday at noon, Global's SAT III system began departing Seattle to begin mobilizing at the job site on Tuesday (7/13).

July 15 - 19, 2010: Cheesman barge mobilized for Saturation Diving

Global's saturation system has arrived and been assembled on the surface diving barge. Crews work diligently to ensure all systems are functioning properly with a series of tests and re-checks. The saturation dive crew is on schedule to be pressed in at 0000hrs on July 26, 2010.