well stench?

[Eway]

"...the smell was a mixture of apartment-building well stench, wet cement, mold,...."

What does "well" mean here? To emphasize that it's really a bad smell? Or that the apartment has a well (to obtain water) that stinks?

[melo]

Perhaps it is "wall stench"
Look up!
Melo

[boothling]

It might mean stairwell. The smell of the communal part of the apartment building - damp and sweat and perhaps worse, depending on the state of the building/inhabitants.