I am trying to use some interpolation tools for analytical data of concentrations of Benzene for monitoring wells. A decent amount of our values for Benzene are '<1' (not 0.943 or 0.345) because of how our sampling works here. Therefore, when I convert my excel tables to points, it classifies my Benzene column as a string and I can't use it as the Z value field. Is there anything I can do so I can still accurately run IDW (or a different interpolation tool) using my Benzene concentrations?
You need to clean up your data prior to loading it into QGIS. I would do this either by removing the data points by giving them a specific value (either something negative (e.g.
-9999) and set QGIS to remove them when running your IDW or an amouint agreed upon for describing a trace amount (e.g.
QGIS needs to know how you want to treat these values and it will only work with real numbers.