INVESTIGATION OF RISING GROUNDWATER LEVEL OBSERVED AT MCMENAMINS EDGEFIELD IN TROUTDALE, OREGON

Located twenty kilometers east of Portland, McMenamins Edgefield is a resort complete with guestrooms, restaurants, vineyards, golf courses, and a spa. Over the past twenty years, head gardener, Kim Kincaid, has noticed an increase in the number of wet areas on the grounds of McMenamins Edgefield. The main elements of concern are production in the Syrah vineyard, mortality of trees surrounding the manor, and saturation of the wedding grove. Several changes have occurred over this twenty-year period that we hypothesized may be the cause of the rising groundwater level: 1) a golf course was constructed on the property in 1998 and expanded in 2007, 2) a neighborhood was developed on a hill up-gradient from the property in 1993, 3) an earth flow occurred in 1993, and 4) the Pacific Decadal Oscillation changed from a warm phase to a cool phase around 1996, resulting in increased precipitation. Site reconnaissance conducted in November 2012 ruled out the golf course and neighborhood development as potential causes of the rising groundwater level. Two soil cores, taken at depths of 1.5 meters, confirmed the presence of ML soils with redoximorphic features, indicating that the soil is poorly drained. The NRCS Soil Survey also specifies these soils can be poorly drained. We concluded that a combination of poorly drained soils and increased precipitation is most likely responsible for the increase in water level. Our recommendations include establishing five strategically placed monitoring wells to better define the subsurface stratigraphy and to observe the seasonal changes in water table depth across the property, increasing drainage in problem areas, and replacing dead trees with wetland facultative species.