Gross Reservoir Expansion Project

Denver Water conducted a subsurface investigation program from June through Oct. 2018 to support design of the Gross Reservoir Expansion Project. This work took place in various locations on the south side of Gross Reservoir. The locations were chosen because they represent areas where knowledge of the subsurface conditions would inform work currently proposed on project features. Land disturbance from the investigation activities were minimal and caused no major disruptions to traffic activities around Gross Reservoir.

The subsurface investigation program included three types of activities described below:

Geophysical Survey is non-destructive testing of subsurface strata by introducing energy into the ground and receiving the energy reflections with geophones placed along the surface. The energy source is often pounding a sledge hammer onto a metal plate. The geophones receive information that is collected and then processed to produce estimate characteristics of the subsurface materials. No chemicals were used during the data collection process.


Test borings were gathered by a drill rig and varied in width and depth depending on the location and conditions. Extracted rock was placed in boxes and transported for additional analysis. The drill holes were grouted upon completion according to the Colorado Division of Water Resources’ Water Well Specifications.


Test pits were dug using backhoe equipment and range in depth from five to 15 feet. The final dimensions varied based on materials encountered. Upon completion of the excavation and documentation process, removed soil was returned to the test pit and returned to approximate original grade.

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