Well Three Manganese Update

from the Water Utility

Manganese Sampling Update
August 11, 2006

Summary

The Water Utility has now collected and analyzed 1241 household samples for manganese in the Well 3, Well 8, Well 10, and Well 29 flushing areas, which are the four wells producing the highest levels of manganese in our water system. This number is about 85% of the total number of household samples we expect to collect during the flushing program in these areas. The results continue to show low levels of manganese at household taps (taken at outside hose-bib spigots). 88% of all samples were below the EPA aesthetic recommendation for drinking water of 50 parts per billion (ppb). 12% of the samples were above 50 ppb. 12 of the 1241 samples (1%) were above the EPA lifetime health advisory level of 300 ppb.

The 12 samples containing more than 300 ppb manganese were collected at 8 sites. None of these 8 sites was found to have water consistently above 300 ppb manganese. Further details about these samples can be found in the table included below.

Based on these results, Dr. Thomas Schlenker, Director of Public Health for Madison and Dane County rescinded the limited health advisory for infants and persons with liver disease in the Well 3 and Well 10 areas on July 17. Dr. Schlenker said, “levels of manganese that have been and are being measured indicate that tap water is acceptable for daily consumption for the entire population.”

Well 3 Flushing Area

The Utility has completed flushing in the Well 3 service area. In addition, we have received the lab results of all 394 samples from our post-flushing sampling in the area. All samples were taken at randomly selected sites in the area from hose-bib spigots.

326 out of 394 samples (83%) were below 50 parts per billion (ppb), the EPA aesthetic guideline for drinking water. 62 out of the 394 samples (16%) were between 50 and 300 ppb. Six samples (1.5%) were above the 300 ppb EPA Lifetime Health Advisory Level for drinking water.

The six samples containing more than 300 ppb manganese were collected at 4 sites. None of these 4 sites was found to have water consistently above 300 ppb manganese. Further details about these samples can be found in the table included below.