Our plan was to perform more water sample tests of the treated areas of the lake then the minimum required.  The minimum would be one sample in each area, three weeks after treatment.  This period of time was determined by the experience of the chemical manufacturer and verified on six other lakes in Michigan.  Three weeks was the time frame for the chemical concentration to fall below 0.05PPM.  The 0.05ppm level is the threshold for getting the green light to perform general irrigation.

 

We had hoped to sample the water each subsequent week after the treatment and at two locations in the treatment areas.  With this data we could fine tune the watering restriction period, speculate how the Huron river affects the chemical treatment, and understand how concentration decays differently in canals, bays and the main lake. 

 

Due to unavailability of our applicator, we have only performed two of the five planned samplings.  Our first sampling was one week after the first application.  The results were 0.145ppm and 0.102ppm at the application initial dose of 1.2ppm.  Our second sampling was four weeks after the first application and two weeks after the second applications.  For the two samples that relate to the first application, the results were 0.025ppm and 0.049ppm.   This low level indicates a safe watering condition   The nearly double concentration of one sample over the other indicates that the river does carry some of the chemical from one area to another, but not significant enough to affect the watering restriction of the area receiving additional chemical.  The 0.025ppm is half of the threshold level but taken a week later than the three week expected restriction. In general, this value supports the three week average restriction for lakes in Michigan. 

 

The next two samples were from the second treatment area and they reported 0.55ppm and 0.080ppm.  This is above the safe watering level of 0.05ppm.  The concentration does indicate that we are on track for three week watering restriction since it is about one half of the concentration after the one week after treatment sample.

 

We are now into 5 weeks after the first application and three weeks after the second application.  A third water sample should be taken this week (around 7/29/03) to get confirmation of the three week water restriction for those affected by the second treatment area and to finish the decay curve of the first treatment area.

 

SeaPro does the chemical analysis at a cost of $100 per sample.  There is no reason why you can't get your own water sample tested should you wish more specific information.  The PLWHC will "publish" all the results after the final sampling in a flyer since this is when we anticipate that everyone can safely water their plants and gardens.

 

Thanks,

 

President of PLWHC