Not sure if this is the right forum to post this but I'll try anyway. For EPA Method 515.4 it is stated that the MDL must be 1/3 of the MRL. Our lab has set our MRL at the regulatory limits for the herbicides in the Safe Drinking Water Act. We are calculating our MDL by Part 136 appendix B using ongoing data collection of MRL values. Some of our analytes are coming out above the 1/3 limit. Has anyone come across this problem and if so what did you do to remedy it?