In a study of water quality in Brunswick County, North Carolina, which has many septic tanks in the sandy soil( up to20 per hectare), Cahoon found high fecal coliform counts in the freshwater and seawater downstream from the dense residential sites.

• 北卡罗来纳州的布伦斯威克郡，就有许多兴建在砂质土壤上的化粪池（公顷最多可达20个）卡洪在那里所做的水质研究发现，高密度住宅区的淡水与海水下游，粪便大肠杆菌数都相当高。