Vegetative Treatment Area Performance and Design Recommendations Joshua W. Faulkner Biological and Environmental Engineering Cornell University

Vegetative Treatment Area (VTA) Function N Transformations, Sorption, Vegetative Uptake Surface Processes: Deposition, Infiltration, Volatilization NO -3 –N < 10 mg/L Zero Discharge

Shallow: 0.33 mg/L Deep: 0.06 mg/L

VTA with Restrictive Layer FRAGIPAN

WTD: 6 cm WTD: 26 cm

Surface of West VTA – lower water table Surface of East VTA – higher water table 7.5 hr11.5 hr19.5 hr9.5 hr13.5 hr17.5 hr 25.5 hr43 hr66 hr From: Faulkner, 2009

West VTA ShallowEast VTA Shallow 7.5 hr11.5 hr15.5 hr 19.5 hr23.5 hr41 hr 9.5 hr13.5 hr17.5 hr 21.5 hr25.5 hr43 hr From: Faulkner, 2009

Kim et al., 2006

Conclusions Elevated water table = increased concentrated flow paths = pollutant discharge A VTA design approach is needed in humid climates and soils containing a restrictive layer that accounts for likelihood of complete soil saturation

VTA Model FRAGIPAN ROOTZONE SUB-ROOTZONE Field 1 - Upslope Field 3 – Middle of VTA Field 2 – Wastewater Infiltration Field 4 – Downslope edge of VTA

Design Recommendations Based on Simulations Increased Ksat and slope increase subsurface lateral flow rates – effectively lowering water table Deeper soils – increases available storage Locate VTAs toward the top of a slope – two effects

Lastly…