Water Test June 9, 2017 is OK

13 June 2017

Water samples were collected at 10 am on Friday June 9, 2017, after 3 days of no rain.  The following results are OK, consistent with the normal readings we have been getting for several years.

#1                        Dock                        12 cfu
#2                        Cedar Fork Creek    14 cfu
#3                        Booker Creek          20 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 76-77F(24.5-25C).   The SECCI clarity reading was 32 inches.

Between the LFA Spring Social on June 4 and this sampling on June 9, I measured 1.6 inches of rainfall at a location in the Eastwood Lake watershed.  No rain fell in the 72 hours prior to the sampling.  The testing protocol mentions that samples taken after a rainfall may be less accurate.  We learned in the years between Hurricane Fran and our last major lake restoration that the rate groundwater from rainfall in the watershed reaches the lake, and once there, the rate at which it passes through the lake and clears the system is dependent on several different factors.  Most important of these is how much rain, how long it persists, the dryness or saturation of the ground, and how full the lake was before the rain.

This water sampling was not part of our regular testing schedule.  We wanted to make sure we were seeing the predicted effect of sampling too soon after a rainfall.  These results confirmed that. Because we added an unscheduled test this year, our next scheduled test will be delayed approximately 10 days, weather permitting.  That will spread sampling intervals more evenly this year

The Eastwood Lake watershed is about 4.1 square miles.  It surrounds the lake on all sides, but most of the watershed extends North and West, out of the Lake Forest neighborhood in the direction of East Chapel Hill High School, Piney Mountain, Horace Williams Airport, and the Fire Station near the intersection of MLK Boulevard and Weaver Dairy Road. Prior to our last major lake restoration, we had a chronic problem of sewer overflows after hard rain.  OWASA was building a sewage “lift station” at Countryside, between Cedar Falls Park and Kenmore Rd.  This was completed in about 2005, and we have not had any major overflows since then. In general, sewers are not supposed to be affected by rain, storm drainage is a separate system altogether.

The increase in clarity (SECCI reading of 32 inches) indicates that we will probably not have an algae bloom at this time.  Algae blooms are common and normal, and while they may color the water and discolor bathing suits and towels, they do not normally present any health hazard.  Rainfall washing “nutrients” into the lake contributes to this.  As we have more development in our watershed, the size of the watershed does not increase, but more of the ground becomes “impervious” because of pavement and buildings.  That leaves less porous ground to filter out “nutrients” (animal waste, fertilizer).  The connection between clarity and nutrients is algae.

People who live close to the water need to be mindful about using “lake margin” type fertilizer, using it sparingly, making sure to “water it in”, and not apply it before an expected hard rain.  For more information on this: http://lakeforestassociation.org/taking-care-of-our-lake/.  Most, but not all, of the local landscape services are aware of this.

Chuck Henage

06.13.17 by Chuck Henage @ 3:40 am
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