The National Ground Water Association (NGWA) announced Golder as a recipient of the Outstanding Groundwater Remediation Project Award for 2020. The awards honor the best of the best in the groundwater industry recognizing innovation, research, safety, and outstanding projects of scientific and technological importance affecting the groundwater industry. This award is in recognition of the groundwater remediation work performed in close collaboration between Golder, S.S. Papadopulos & Associates, Inc (SSP&A), and Arcadis on the Rapid Response and Remediation of Wellfield with Perchlorate Project for the City of Evart, Michigan.
This project succeeded thanks to a 15-year history of collaboration between the consultant teams, key stakeholders, and the City of Evart, Joel Henry, Golders Senior Project Hydrogeologist. Thanks to the Citys willingness to try an outside-the-box solution with their own infrastructure and the states regulatory support, the City accomplished a remedial cleanup that could easily have taken years in the course of months. The project also recognizes the potential environmental consequences of brief or one-time events that can fly below the radar of traditional wellhead protection efforts.
In 2015, perchlorate was detected in the Citys municipal water supply. Investigations by Golder determined that the perchlorate source was fireworks launched during the annual 4th of July celebrations held for many years at the nearby county fairgrounds. Perchlorate is used in fireworks to provide oxygen needed for the rapid combustion during launch and detonation, and on average constitutes approximately 35% of a fireworks weight. The project demonstrated that perchlorate is not fully decomposed, as might be expected; rather, approximately 2% of the initial perchlorate mass remains unreacted and is environmentally dispersed. The study illustrated the significance of considering fireworks and other one-time activities in wellhead protection planning.
A plume of perchlorate-contaminated groundwater was delineated and estimated to have a volume of 900 million liters. Groundwater modeling by SSP&A predicted that purging 3.7 plume volumes (over 3.3 billion liters) was required to flush the contaminant mass from the aquifer and achieve a target concentration. To expeditiously reduce the contaminant mass, three municipal supply wells were disconnected from the Citys distribution network and re-dedicated to purging water to waste under a state-issued National Pollutant Discharge Elimination System (NPDES) permit. The remedial target was achieved within 18 months, and the wells have since been restored to supplying the City. With limited remedial construction and no infrastructure to decommission, the use of existing infrastructure resulted in substantial cost savings.
During remediation, the required firm capacity was maintained by the City of Evart and Arcadis by re-balancing the production schedules of the remaining supply wells, and by constructing an additional supply well. A pilot-scale ion-exchange treatment system was also evaluated by Golder as a contingency measure in the event that concentrations did not decline as predicted. With thoughtful planning and collaboration, the team accomplished the restoration of groundwater quality in an exceptionally short period of time.