Green or Gray? Choosing to Preserve Water Quality

The Portland Water District conducted a green-gray analysis to compare natural versus gray infrastructure for an EPA-granted filtration system to improve Sebago Lake's water quality. They ultimately chose to invest in forest-based natural infrastructure, including restoring riparian buffers and reforesting riparian zones. The decision offers financial saving of $12 million over 20 years in the baseline modelling scenario, with additional co-benefits from carbon sequestration and improved fish habitat estimated at $72 - $125 million. The USEPA granted a filtration avoidance waiver for the project, while the utility contributes up to 25% of the filtration cost in conservation easements, approximately $26,000.