Engineered Wetland Treatment System Provides Long-term Sustainable Groundwater Treatment System at Former Air Force Base
An Engineered Wetland Treatment System (EWTS) was constructed by the Air Force as a component of a long-term green and sustainable groundwater remediation system at the former Wurtsmith Air Force Base in Oscoda, Michigan. Historic waste disposal practices associated with two former military landfills resulted in the creation of a mixed chemical constituent groundwater plume that migrates off Air Force property, impacts private landowners, and discharges to a nearby recreational surface water body. As part of the overall site remedy and to prevent migration to the neighboring lake community, the Air Force is implementing a 400 gallon per minute (gpm) barrier groundwater pump and treat system that hydraulically controls the groundwater plume on-site and treats recovered groundwater in a sustainable on-site EWTS. Primary chemical constituents in the recovered groundwater which are treated in the EWTS include TCE, BETX, TOC, iron, manganese, ammonia, and phosphorous. The EWTS utilizes a series of natural and passive processes to treat recovered groundwater via cascade aeration, sedimentation pond precipitation of metals, and both free water surface (FWS) and submerged surface flow (SSF) wetlands for biological treatment. Treated groundwater is infiltrated back into the subsurface via a series of groundwater infiltration trenches.
As part of the EWTS installation, BB&E was responsible for preparation of design documents, work plans, and the requisite discharge permits; project quality control support; regulatory assistance; community relations support; and startup assistance. BB&E helped spearhead the use of the EWTS as part of the overall site remedy including conducting proof of concept cascade aeration pilot testing. Construction of the EWTS commenced in August 2010 and was completed in June 2011. Full-time operations of the EWTS commenced in October 2011. To date, based on system compliance monitoring, the EWTS is effectively treating recovered groundwater to meet the stringent State of Michigan Part 201 and Part 22 discharge requirements.