Tunnel and Combined Sewer Overflow Control

About this project

This project was designed as part of a Capital Improvement Program to control CSO discharges and to comply with state and federal environmental mandates.

This large storage tunnel 160 feet below ground runs approximately seven miles to effectively capture wet-weather overflows from 18 outfalls in various Michigan cities. The tunnel directs overflow during heavy rains and snow melts to local wastewater treatment plants and away from the rivers. The project scope involved developing a 30-foot diameter rock tunnel to provide 210 million gallons of CSO storage from 18 outfalls.

Sigma’s scope included the architectural, instrumentation and controls, mechanical and electrical engineering design for the entire system and civil/structural design for the outfalls and near surface diversion facilities. Services involved inflow/infiltration flows (I/I), sewer route selection, sewer material, plan views, construction techniques, specifications, and cost estimates.

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