Rainbows in the Lehigh Valley Gorge

[TMo]

Sewage treatment...  Lovely topic.

I'm on to attempting to finishing that system of 3 clarifiers and the administration building for the facility.  Got the clarifiers out of cold storage and added a central shaft that will protrude out of the walking deck between the clarifiers.

   

 and considered how to fill them up prior to painting the "liquid" surface and adding realistic water to the top of the clarifiers.  My first thought was to get the plaster out and slough it off into the interior of the clarifiers, but guess what?  All out of plaster.  What else could I use as a fill?  How about coffee grounds?  Dribbled them in and then used the good old diluted white glue liberally applied to the coffee grounds to solidify them.  Although brown might be an appropriate color for at least one of the clarifiers, eventually the brown stuff is going to settle out and there should be relatively clean water in at least one of the clarifiers.  However, I think I should be able to paint the surface once it's dry before adding the Realistic Water.