Flea Infestation in Yard

Has anyone ever experienced a flea infestation in their yard? We had to stop letting the dogs outside because they would come back in with 30-40 fleas each time (they take flea meds and wear collars). When I walk in the yard, my legs get covered with them. I’ve trimmed back the yard and treated it with bifen and it doesn’t seem to help much. My neighbor has piled up a massive pile of yard waste roughly 25’ x 5’ along our shared fence line so I’m thinking this might have something to do with it. Just curious if this was a localized thing for me or if it’s the time of year. Any advice or ideas?