Sewage Lagoon - Deciphering an as-built drawing 1

[Kam.R]

I'm trying to understand some old and very damaged as-built drawings for a sewage lagoon (constructed in 1957). The actual lagoon is currently abandoned.

Any ideas what might be located in the clouded area? Nothing? Something to do with sludge drying?

Of particular interest, is if there might be underground pipes or trenches.

Thank you!

 

[JedClampett]

To my simple structural mind, it looks like a gravel road to get to the sludge drying bed to muck it out.

 

[bimr]

Probably an intermittent sand filter / leaching sand filter to dispose of the sewage. There may be laterals the length of the sand filter. The lagoon was likely built after the sand filter failed.