Atrium Lobby (Hyatt Regency Baltimore on the Inner Harbor)
Phytoremediation is designed to extract groundwater from the subsurface. The performance of a phytoremediation system may be evaluated by estimating the tree-stand withdrawal volumes using the diurnal fluctuations of groundwater and sap velocity measurements as indicators of transpiration. AECOM designed and constructed a multi-staged phytoremediation system to address dissolved phase residuals and provide supplemental hydraulic control at a former MGP site in New Hampshire. This system was installed after source control measures were completed. The overall objectives of the system included providing passive interception of the shallow groundwater thus reducing groundwater migration and using transpiration to degrade residual BTEX. Over 1,000 trees were planted over approximately 1.5 acres in three stages: 2002, 2005, and 2006. Long term groundwater elevations measured over the summers of 2009 and 2010 in several site monitoring wells were used to estimate daily withdrawal volumes through root uptake. Evaluation of 2009 hydrograph data indicates that withdrawal estimates may average 2,500 gallons per day. Over the summer of 2010, thermal dissipation probes were installed in select trees to estimate sap velocity; these data were interpreted and extrapolated to make estimates of site-wide withdrawals. Preliminary evaluation of the sap velocity data indicates volumes comparable to the hydrograph evaluation. This presentation will elaborate on the approaches to estimate total withdrawal amounts, comparing site values to literature values.
