Past checks

One row per dated record at a landfill. The change is what the satellite record shows after that date, compared with control sites, with its 90% range. It is a screening indication that followed the date, never a cause. Colour never stands alone: every result has an icon and a label.

"Smallest drop the test could see" is the smallest drop this site's own passes would have caught 80% of the time; a real drop below it could have been missed. Terms are explained in How to read this site.