Broken septic tank cover.

An important part of the septic tank is the cover. A broken, cracked or Missing lid can present a serious health or safety hazard. Typically made from fiberglass, plastic or concrete, covers can break. Some popular septic tank additives actually cause corrosion from the hydrogen sulfide gas released in the tank during the digesting process that also eats away at the concrete or fiberglass cover. Age, abuse or many other things can cause a septic tank cover to fail. A compromised cover can allow sand, rocks and debris to fall back into the tank plus what any children decide to drop into that hole in the ground. Broken covers are a trap to animals and even people. At best it is a very unpleasant experience to fall into a septic tank. At worse it is a death sentence. Repair or replace all broken or cracked lids to at least the original strength. It is not worth the risk.
This is personal for us at TankTechsRx for Septic Systems because one of our children fell into a hole in the lawn that was the result of a broken lid over an abandoned cess pool no one knew was there. Fortunately, he was not seriously injured.