SRSW has completed its annual aggregation and analysis of the DEQ's Pall/Gelman dioxane sampling database through 2015 (as reconstituted by the DEQ from Pall's monthly submittals.) New Google Earth mashups incorporating the 2015 data depict the reality of the issue.
Here is a quick interactive map with dioxane plumes, PZ & wells with highest ever readings 2013-2015...
(download Google Earth mashups for more complete detailed information in 3D & 4D)
Of the 270 wells still sampled (of 517 locations total), 61 wells had their highest ever readings during 2013-2015. Of these 61 sample locations with highest ever readings, Pall proposes to reduce how often it samples them... by about 40%... 237/year to 144/year... with most reduced from quarterly to twice a year.
Some of the locations slated for reduced sampling are on the edge of the prohibition zone and are the last sentry wells before the dioxane spreads to homeowner wells without access to city water. This makes no common sense. If anything, wells that still have increasing level of dioxane and wells near the edge of the prohibition zone should be sampled more often, not less often.
(Note: several of the highest ever readings, those with highest ever reading dates in Feb & March 2013, may have been false positives because of poor QA/QC during the laboratory analysis.)