McCook Reservoir Rockwall Stabilization and Geotechnical Instrumentation

The project involves construction and operation of a floodwater storage reservoir at the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) Lawndale Avenue Solids Management Area (LASMA) in two stages.

Challenge

This project required the stabilization of the reservoir rock wall by means of surface preparation, scaling and installation of reinforcement and support construction. Project documents specified installation of multiple 300-350 foot deep automated in-place inclinometer (IPI), 175-foot angled multi-point borehole extensometers (MPBX), and vibrating wire piezometer (VWP) along the narrow high wall.
 

Solution

Based on the poor performance of existing instruments previously installed by others at McCook, GZA proposed to install Measurand Shape Arrays in lieu of the specified IPIs and MPBXs. This alternative still allowed the district to connect to the existing Automated Data Acquisition System (ADAS). The instruments will be used to monitor the stability of the open rock face during operation of the city’s combined sewer overflow system. GZA utilized cellular modems and existing McCook infrastructure to provide network connectivity and developed a hosted server that housed Canary’s multilogger suite software that managed the network, collected data, and provided a web interface.
 

Benefit

GZA’s instrumentation solutions were a key component in the rockwall stabilization project and enabled the contractor to monitor any changes in real time. Additionally, the proposed alternative reduced the specified borehole diameters and provided the district with a more reliable solution.