The potential impact of septic tank soil-absorption systems on water quality in the principal valley-fill aquifer, Cedar Valley, Iron County, Utah - assessment and guidelines (RI-239)

By: J. Wallace and M. Lowe Nitrate can be used to identify potential deleterious effects of development using septic tank soil-absorption systems. We use a mass-balance approach to provide a valley-wide assessment of the potential impact of nitrate from septic tank soil-absorption systems on ground-water quality. Approximately 1,406 septic systems exist in Cedar Valley. Our calculations indicate the number of septic tank soil-absorption systems in Cedar Valley should not exceed 4,000, representing a valley-wide average septic-system density of about 27 acres/system (0.109 km2/system), to maintain an overall nitrate concentration of 6.5 ppm (6.5 mg/L). This allows a 1 mg/L degradation of water quality with respect to nitrate from the current background level of 5.5 ppm (5.5 mg/L). We also provide guidelines for site-specific evaluations of the effects of septic systems on ground-water quality for proposed subdivisions in Cedar Valley Other Information: Published: 1998 Pages: 1