Open lids carefully, check inlet and outlet baffles and tees, file fractures or deterioration

https://romeo-wiki.win/index.php/Hydro-Jetting_vs_Conventional_Septic_System_Cleaning:_When_as_well_as_Why_to_Use_Each

Open lids carefully, check inlet and outlet baffles and tees, file fractures or corrosion, and repair seals to stop groundwater intrusion and exfiltration that can overload the drainfield.