Emissions from Evergreen’s systems are all treated in some fashion. Groundwater and LNAPL pumping systems are closed loop systems from which vapors are extracted from the system components themselves (no vapors are extracted from the subsurface) and are treated with either granular activated carbon or catalytic oxidation. The sewer vapor extraction systems both use biofilter beds to treat air that is removed from the sewers. All systems are permitted by Air Management Services who define emission levels that each system must meet. There are no odors observed from these systems’ emissions.
Other remediation processes such as excavation may create short-term odor simply by disturbing the subsurface and extracting the materials. Engineering controls (e.g. odor/dust suppressants and/or fans) can be used to minimize the transport of odors off-site during excavation activities.