Table 3. Water system failure (n = 326) cited in 293 waterborne disease outbreak reports in small drinking water systems in Canada and the United States (1971–2014), stratified by water source.
| Deficiency 1 | Description | Water Source | ||||
|---|---|---|---|---|---|---|
| Ground Water# (%) | Surface Water# (%) | Unknown# (%) | Other 2 # (%) | Total | ||
| Inadequate treatment | An existing water treatment system failed to provide adequate protection from contamination | 55 (28.8) | 13 (31.7) | 3 (3.3) | 3 (75.0) | 74 |
| Lack of treatment | No water treatment was used | 57 (29.8) | 9 (22.0) | 0 | 0 | 66 |
| Sewage contamination | Human sewage contaminated the water supply at any point in the water system | 21 (11.0) | 4 (9.8) | 3 (3.3) | 0 | 28 |
| Distribution system | Contamination entered through the distribution system e.g. cross connections, broken water main | 14 (7.3) | 1 (2.4) | 2 (2.2) | 0 | 17 |
| Source contamination | Contamination from surrounding land use, principally animal waste | 2 (1.0) | 3 (7.3) | 0 | 1 (25.0) | 6 |
| Weather events | Extreme weather events, such as heavy precipitation or prolonged drought, contributed to contamination | 2 (1.0) | 1 (2.4) | 0 | 0 | 3 |
| Unknown 3 | 31 (16.2) | 10 (24.4) | 82 (91.1) | 0 | 123 | |
| Other 4 | 9 (4.7) | 0 | 0 | 0 | 9 | |
| Total | 191 | 41 | 90 | 4 | 326 |
127 outbreak reports noted more than one deficiency
2Other water sources included a cistern (n = 1) and reservoirs (n = 2)
3Unknown was not reported
4Other deficiencies included contaminated water storage, point of use contamination, geological conditions (i.e. soil conditions that led to the contamination of ground water), well construction and contaminated filter sand