Did you know, MPCA rule 7080.2450 requires Individual Sewage Treatment Systems’, (i.e., septic systems’) owners to every 3 years or less: ”
assess whether sewage tanks leak below the designed operating depth and whether sewage tank tops, riser joints, and riser connections leak through visual evidence of major defects; and
measure or remove the accumulations of scum, grease, and other floating materials at the top of each septic tank and compartment, along with the sludge, which consists of the solids denser than water.”
You can do the measurements and inspections yourself or hire a pumping service to do it. See https://www.revisor.mn.gov/rules/?id=7080.2450. Talk to Merillee DeGroot, the Rice Co. Sanitarian, about how to make a dipstick for the measurements.