The OFGWQ survey and follow-up studies have not been able to determine how
much groundwater contamination is due to septic systems or to animal manure. As nearly all farms in the OFGWQ survey had septic systems for sewage treatment, it was only possible to study their impact as a function of distance from the farm well. No significant correlation was observed (Rudolph and Goss, 1993). Fleming (1992) also found no impact of the distance from the septic system on the quality of well water. Together with the feet that specific point source contamination was not indicated on farms where multilevel wells were installed, these observations might suggest that septic systems were not a major source of contamination. However, nitrate plumes have been identified leaving the weeping bed of septic systems (Robertson et al., 1991) showing that they are a source of groundwater contamination by this mineral species, and even this could not be established through the sampling of farm wells in the OFGWQ survey. Other studies,which included analysis of wells on sub-divisions where several wells and septic systems can be in close proximity, have shown links between contamination and the septic systems(Turco, 1990).