Post date: Sep 01, 2014 5:1:57 AM
Pall Slow to Delineate Plume
In July 2002, Pall Life Sciences installed a new monitoring well (MW-81) in the parking lot behind Knight’s Steak House at 2324 Dexter, across from Veterans Park. The well was intended to establish the northern boundary of the dioxane plumes moving into the City in the vicinity of Veterans Park.
Readings taken during the well boring failed to show any 1,4-dioxane above the detection level of 1 ppb. The samples were taken about every 20 feet of depth: 31, 51, 71, 91, 131, 151.
However, the well was screened in a wet sand/gravel layer at 153-158 feet, which was deeper than the final reading location, a moist, slit/sand layer at 151 feet.
The well was not sampled until 11/7/02, when 126 ppb was found. A re-sample taken 11/26/02 gave a reading of 125 ppb. The data was not made public until early December.
Some are claiming that the high readings at MW-81 show that the plumes are moving much faster than expected, and therefore to stop the plume, normal safeguards must be bypassed.
SRSW contends that the sparse sampling during the initial boring of MW-81 failed to detect the dioxane that was already there. Had samples been taken at every five vertical feet in all wet layers, the 125 ppb in 153-158 range would have been found four months earlier.
Furthermore, a wet layer at 102-105 feet was not sampled during the boring. This wet layer is between two dry layers and could be an extension of the Evergreen aquifer. Even though this layer is relatively thin, a reading from it would help determine plume boundaries and pathways.
Ineffective well sampling and plume definition should not be an excuse to do an ineffective cleanup.