Stand on of the mentioned piers in-game and execute in Debug Console:
_b = nearestObjects [getPosATL player,["Piers_base_F"],500]; _i = 0; { _bp = _x buildingpos _i; while {str _bp != "[0,0,0]"} do { _mkr = createMarker [format ["%1-bpos",_bp],_bp];_mkr setMarkerSize [0.3,0.3];_mkr setMarkerType "mil_dot";_mkr setMarkerColor "ColorWhite"; _i = _i + 1; _bp = _x buildingpos _i; }; } forEach _b
This will mark all the building positions of nearby piers with a white dot. A few of them will be inside the non-enterable containers.