Requiring solutions for Weatherproof Range-sensors

I’m using ultrasonic sensors right now from MaxBotix (MB-7137 TrashSonar I2C) on these type of containers:


Problem is, that on some exceptionally dirty containers, after a few weeks they already look like this:

Note: the contamination in this picture was sufficient to completely block out the signal and return invalid measurements.

I’ve though really hard about any solutions I could possibly implement to mitigate this. I already am using a weatherproof transducer that is actually designed for waste monitoring/. Due to energy constraints, I can’t add a little protective shield + Servo, and I’m afraid the placement on the container will matter little. Laser sensors I used were even worse.

I’m just hoping someone may have some smart and innovative idea for this kind ofapplication, before I settle on the fact that they will just have to get cleaned often by people to remain functional.

This is what the other large organizations are using sensor wise.

If you look at there enclosures they seem to mostly have this feature as far as where the transducer is placed. Do you think this design would have helped?