Even though the State does not require it, we are continuing to measure the herbicide residue after it was measured as less than 75 parts per billion, and the State declared the lakewater to be “safe to drink*.” We only sampled from two locations, because the cost of analyzing each sample is in excess of $100.00. We chose the two locations where we had found the highest concentrations of triclopyr in earlier tests, one from each end of the lake.
As expected, the concentration has declined significantly. Although the sites tested are where the chemical was applied, we believe that by this time the chemical has diffused throughout the lake, and that concentrations measured anywhere would be similar.
|Location||Applied||June 3rd||June 9th||June 15||June 21||June 28||July 28|
|0 days||1 day||7 days||13 days||19 days||26 days||56 days|
|Site 1||1.5 ppm||202 ppb||121 ppb||n/a||n/a||38 ppb||n/a|
|Site 2||1.5 ppm||930 ppb||127 ppb||n/a||n/a||66 ppb||13 ppb|
|Site 3||1.5 ppm||510 ppb||113 ppb||98 ppb||59 ppb||50 ppb||n/a|
|Site 4||2.0 ppm||85 ppb||n/a||n/a||n/a||47 ppb||n/a|
|Site 5||2.0 ppm||160 ppb||n/a||n/a||n/a||39 ppb||n/a|
|Site 6||2.0 ppm||145 ppb||n/a||n/a||n/a||42 ppb||n/a|
|Site 7||2.0 ppm||123 ppb||n/a||93 ppb||65 ppb||42 ppb||17 ppb|
|Site 8||2.0 ppm||332 ppb||n/a||88 ppb||n/a||40 ppb||n/a|
|Site 9||0.0||15 ppb||n/a||n/a||n/a||30 ppb||n/a|
|Site 10||0.0||n/a||n/a||31 ppb||n/a||0.0 ppb||n/a|
We plan to test the water at least once more, in late August, around 12 weeks after the chemical application.
* The State has determined that 75 ppb is a safe amount of triclopyr in drinking water. Nonetheless we do not recommend drinking from the lake – for a variety of other reasons.