Gross Reservoir’s September update details the work remaining after dam raising

Denver Water’s September update on Gross Reservoir makes clear that the major dam-raising milestone still leaves substantial construction ahead.

The utility topped out the roller-compacted concrete portion on June 3, raising the dam 130 feet above its former height. In the account updated September 15, Denver Water says roughly a year and a half of dam-construction work remains.

That work includes a protective layer of conventional concrete, a water gate, the spillway crest, a bridge over the spillway and the stilling basin.

The expansion is intended to nearly triple the reservoir’s storage and add about 25 billion gallons. Denver Water anticipates project completion in 2028, but says the timing of filling the enlarged reservoir will depend on available water.

The distinction between structural progress, project completion and filling matters to customers and capital planners. These milestones describe different kinds of readiness, and they need different evidence.

A dam can have reached its visible height while still depending on hydraulic equipment, finishing works and operating preparation. New storage becomes a water-supply benefit only when the completed facility can capture and manage available flows.

For other water owners, the update is a useful reporting model: name the completed work, describe the remaining interfaces and explain the conditions that control the start of service.

Reporting source: Denver Water, updated September 15, 2026. Sources reviewed September 30, 2026. Delivery implications are Infraday analysis.

Illustrative photograph; it does not document the announced work. Silicon Valley Clean Water treatment plant, Redwood City, September 2023; representative photograph. Photo: Pi.1415926535 / CC BY-SA 4.0. No editorial alterations; WordPress may resize or crop for display.