There may be some non-mechanical (back hoe, etc.) methods that could help reduce the muck.

One would be adding some microbial agents, and you could check the Pond Boss resource guide for that.

The other method may be to introduce aeration to the pond; this could be done with 110V electric or maybe solar or wind powered.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."