Over the past few days customers in our water system may have noticed a discoloration in the drinking water. It has been determined that slightly elevated levels of manganese is causing the discoloration. Preliminary sampling has indicated levels of manganese that are consistent with the appearance of color. Manganese is not a regulated constituent in water supplies and is deemed as a secondary standard by the EPA meaning elevated concentrations may result in discoloration and possible taste issues but does not pose a risk to health. All other routine water quality sampling has not indicated anything that is known to pose a risk to health. So while the water is discolored, the water is still safe.
The Acton and DeCordova areas are going to be the most affected but other customers in our service area may also notice this issue. The water may appear slightly brown, yellow, orange or green. House filters may stain black or brown. It is our understanding that in that situation the filter is only staining and the staining is not using up the filter.
It appears that as the temperatures have risen that Lake Granbury is beginning to de-stratify which is the process in which cooler water at the bottom of the lake becomes warm and rises into the upper parts of the lake. When this happens, manganese, which is found at higher concentrations at the bottom of lakes, is then stirred up into the upper level of the lake at which our raw water intake pumps are located.
This condition should be temporary and should clear up as the lake begins to settle. In the meantime we are searching for ways to better remove the manganese from the water with current treatment processes on hand. We will also be monitoring concentration levels along with our other routine water quality sampling. In the event there is an adverse change we will notify the public.