Thornton Transitional Reservoir

Project Overview

The Thornton Transitional Reservoir project was constructed to alleviate flooding from Thorn Creek during heavy rainfall events.  The scope included the construction of a diversion structure at Thorn Creek which conveyed stormwater into a drop shaft/deaeration chamber and transported it via tunnel to a rock quarry that was utilized as a reservoir.  A drain tunnel located at the midpoint of the main tunnel would then transport the stormwater to an existing MWRDGC deep tunnel for treatment.

The project presented some unique challenges.  The main tunnel was excavated from a portal located at the bottom of a 300 ft. deep active rock quarry.  This required significant coordination with the quarry owner to move personnel, materials, and equipment to and from the work site daily.  The drain tunnel was excavated from within the main tunnel and presented unique challenges with launching the TBM and removing the excavated spoil.