Check the low points linked to the symptom
Compare the outlet and sump condition with the level instrument and actual draw-down. This shows whether material at a low point, rather than a reading fault, is restricting useful operation.
Compare recent operating levels with the last draw-down before assuming that sludge alone caused the loss. A failed level instrument or changed inflow can give a similar symptom.
Choose the low points needed for the next task
Define the useful result before removal: reopening an outlet, recovering working volume or exposing a floor area for inspection. The site also identifies who controls isolation and whether another specialist follows the clean.
Sludge depth is rarely even across a tank floor. Samples, previous removal records and the position of sumps or outlets help identify where the dense material is likely to sit. Recovery can then focus on the actual collection zones while keeping the liquid above it as a separate estimate.
For the removal service, see tank sludge removal. If the symptom is lost working volume, compare it with the checks for reduced tank capacity.