Predicting Potential Groundwater Impacts on a Deep Tunnel CSO Control Project

Underground tunnel conveyance systems are a practical solution for storing large volumes of combined sewer overflow (CSO) with limited surface disruption during construction. Careful consideration during the evaluation and preliminary design phase of the project can help to mitigate risk and potential pitfalls during detailed design and construction. Early planning in the preliminary design phases can reap great project rewards, cost less, and lower risk during construction. This paper presents the principal groundwater protection elements for the development and constructability considerations of a CSO storage and conveyance tunnel project. Information presented includes the evaluation of the geology and hydrogeology of the tunnel alignment corridor, construction considerations, project considerations, geotechnical exploration program, risk management strategies, and modeled conclusions to protect a City's groundwater supply.