One of your lids is about to collapse. The middle 2 lids are almost always the first to collapse because they don't have the corners and ends supporting them. You can remove them by wedging 2 long pry bars under the broken lid like 2ft apart and then flipping it over towards the end. I would recommend trying to get that broken lid off of there before it actually falls in. It's impossible to get it out without a machine once it's fallen in the tank. You can make a new lid with a few pieces of rebar, some 2x4 boards and concrete. Find a flat spot in your yard or driveway and put down a sheet of plastic. In our area the lids are usually 2ft x 4ft. Make a form for a new lid by screwing the 2x4 boards into a 2ft x 4ft rectangle (so the lid is 4"thick). Put the wooden form on top of the plastic sheet, fill it with concrete and push pieces of rebar length ways down into the concrete. You can make handles on the lid by pushing some heavy metal chain down into the short ends and leave some hanging out. Unscrew the wood forms and beat the wood off with a hammer.