Enteric viruses are responsible for a large number of ground-waterborne disease outbreaks every year. Septic tanks are the most frequently cited causes of ground-water contamination in disease outbreaks. Controlling the placement of septic tanks such that all viruses would be non-infective by the time the effluent reached drinking water wells would likely reduce the number of waterborne viral disease outbreaks. The study compares different geostatistical techniques (kriging, cokriging, and combined kriging and regression) that estimate virus inactivation rates in ground water. These estimates were used with the regional ground-water flow characteristics to estimate septic tank setback distances over a city-wide area. Combined kriging and regression, which eliminates the need for laboratory values of virus inactivation rates by using the linear regression relationship between temperature and inactivation rates, produced comparable results to the other two methods, yet reduced the cost of the analysis considerably.