Managing Risk to Groundwater Wells during Pump Station and Pipeline Construction — The Walnut Lake Project

The Walnut Lake No. 1 project located in Oakland County, Michigan consists of a deep pump station and force main and serves to virtually eliminate sanitary sewer overflows. A critical element identified during the preliminary design phase was the need to protect adjacent private groundwater wells from possible loss of service and reduction in water quality due to a lowering of the ground water table. Installation of the pump station required excavation to a depth of 50 feet. To quantify the potential impact, a model of predicted dewatering radius of influence was developed and the location of nearby wells identified. A $200,000 water supply and well repair allowance was included in the bidding documents. A formal plan of action was developed to guide the team in quickly and cost-effectively resolving homeowner complaints. A total of ten wells were impacted during construction for a cost within the original allowance amount. This proactive approach successfully eliminated legal action, severe customer complaints, and health and safety issues.