- Lake Forest Association (LFA) - Caretakers of Eastwood Lake in Chapel Hill, NC.
Water samples were collected beginning at 11:00 am on Thursday August 31, 2017, by Anthony Henage. The following results are very good.
#1 Dock 4 cfu
#2 Cedar Fork Creek 4 cfu
#3 Booker Creek 13 cfu
Caution level is individual reading above 400 cfu, or average above 200 cfu. CFU = colony forming units per 100ml.
Lake water temperature ranged from 78.5-79.5F(25.8-26.4C). The SECCI clarity reading was 22 inches, same as the previous test in July.
There was a light rain two days prior to the sample, less than 0.2 inch. These readings continue to be very good and consistent with the results we have gotten in previous years.
Fecal coliform is an indicator organism, and our testing is required by the health department because we allow swimming in the lake. We are very fortunate to have the consistently good results that we have been getting. Before OWASA built the Countryside wastewater pumping station our results were generally in the safe range but much more variable than they have been since it went online.
One informal correlation I have noticed, for any amateur (or professional) bacteriologists who may read this is that the higher cfu count is usually associated with the lower water temperature. My theory about that is: the bacteria we monitor lives in the gut of warm-blooded animals, and it dies in the water. The cooler water is fed from rainfall and springs and it carries the bacteria from the source to the lake, where it slows down and warms up. The lake is also diluting the bacteria by the simple geometry of volume, so the lower counts in warmer water may be the results of those two processes. Any other theories?