GEOCHEMICAL AND SOCIOLOGICAL STUDY OF BACKYARD WELLS AND GARDENS IN UTAH VALLEY, UTAH

Ferreira (2013) documented elevated concentrations of As and heavy metals in the rivers that flow westward across the Wasatch Range and heavily-populated Utah Valley, Utah, to drain into Utah Lake. Within Utah Valley average fluvial As for Provo River (As = 0.342 mg/L) and American Fork River (As = 0.152 mg/L) exceeded the EPA standards for freshwater streams for acute exposure (As = 0.340 mg/L) and chronic exposure (As = 0.150 mg/L), respectively, which are not unusual for rivers affected by mine tailings. In Utah Valley it is not uncommon for urban residents to dig and maintain shallow (< 10 m) wells in their backyards, which is unusual in urban areas outside of developing countries. Since the rivers in Utah Valley are losing streams, the question arose as to the levels of As and heavy metals in these shallow wells. The objectives of this study are to determine (1) the concentrations of contaminants in backyard wells (2) the impact on home gardens of irrigation by backyard wells (3) the pathways for shallow groundwater flow (4) why the urban residents of Utah Valley dig backyard wells. The objectives were addressed by collecting water samples from 111 backyard wells in Utah Valley. Water temperature, pH, electrical conductivity and dissolved oxygen were measured on-site. Water samples are being analyzed for nitrate, phosphate and sulfate using the Hach DR-2700 Spectrophotometer and for As and 11 heavy metals (Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti, Zn) using the PerkinElmer Optima 8000 ICP-OES. Stable isotopes of hydrogen and oxygen are being measured using the Picarro Cavity Ringdown Spectrometer. In addition, well owners are being interviewed and garden plant samples (corn, lettuce, onion, squash, tomato) are being analyzed. Analysis of 41 wells thus far has shown that EPA drinking water regulations were exceeded in four wells for As, four wells for Cd, three wells for Fe, seven wells for Mn, and one well for nitrate. Maximum concentrations were As = 0.063 mg/L, Cd = 0.030 mg/L, Fe = 0.581 mg/L, Mn = 0.572 mg/L, and nitrate = 13.6 mg/L, compared with EPA regulations of As = 0.01 mg/L, Cd = 0.005 mg/L, Fe = 0.3 mg/L, Mn = 0.05 mg/L, and nitrate = 10 mg/L. Wells with elevated As and heavy metals tend to occur not near streams, but along the boundary between the groundwater recharge and discharge zones. Further results will be reported at the meeting.