2017-05-10 CC Packet - Laserfiche WebLink

Home Browse Search

Discussion The concentration of the microbes/genetic material found during this one -day sampling effort is not unusual, especially given the pond can be accessed by water fowl and other wildlife. The high concentrations of Cryptosporidium related to the water sprinkler might be related to the small volume that could be collected directly from the sprinkler, or possibly some bird droppings directly in the samples taken. (More sampling would be needed to verify.) There were no detections of Legionella serogroup 1, which is the serogroup of most concern for human health. The subtype of the avian influenza virus was not determined. However, the presence of avian influenza virus is typical when water fowl are present on ponds. The detection of rotavirus and human Bacteriodales indicates that traces of human sewage are in the pond water. Again, this is not entirely unexpected, since stormwater runoff often passes over areas or objects where human fecal material might exist, such as trash containing soiled diapers, outdoor portable toilets, recreational vehicle dump stations, or other contaminated locations. In some cases, leaking underground sewage pipes have also contributed to the presence of human sewage in stormwater ponds or surface water. The source is not known in this case. Recommendations Given the results from this sampling, MDH would currently advise the City of Centerville to continue the practice of irrigating with the stormwater in the overnight hours when few people are using the park. The exposure of irrigated areas to sunlight in the morning hours, in addition to a longer time period before the public uses the park, will allow potentially harmful organisms to subside or become inactivated. If there are occasions when the source water pond is highly populated with water fowl, or if a public health alert related to bird flu has been issued, refraining from irrigation with the system until the water fowl population has moved away or decreased, or the public health alert has been lifted, may be appropriate. MDH is planning to continue to study questions related to water reuse and public health risks. If additional research causes a change in MDH's recommendations stated above, we will contact the City with our recommendations for operation of the irrigation system. We wish to thank the City of Centerville for the assistance as we work to learn more about water reuse systems in Minnesota. If you have questions or would like to discuss the results of the sampling further, please contact us at 651-201-4923 or nancy.rice@state.mn.us. Minnesota Department of Health Environmental Surveillance and Assessment PO Box 64975 St. Paul, MN 55164-0975 (651) 201-4899 health.risk(@state.mn.us www.health.state.mn.us 2/9/2017 To obtain this information in a different format, call: 651-201-4923. Printed on recycled paper. 4 103