SEGMENT INFORMATION - Segment property, plant and equipment, at cost, less accumulated depreciation (Details) - USD ($)	Jun. 30, 2026	Sep. 30, 2025	Jun. 30, 2025
SEGMENT INFORMATION
Property and equipment, net	$ 52,944,409	$ 53,467,967	$ 54,090,651
Underground Infrastructure Construction
SEGMENT INFORMATION
Property and equipment, net	37,409,209		39,016,246
Industrial Construction
SEGMENT INFORMATION
Property and equipment, net	14,321,956		14,058,440
Building Construction
SEGMENT INFORMATION
Property and equipment, net	1,122,837		976,689
Operating Segments
SEGMENT INFORMATION
Property and equipment, net	52,854,002		54,051,375
Operating Segments | Underground Infrastructure Construction
SEGMENT INFORMATION
Property and equipment, net	37,409,209		39,016,246
Operating Segments | Industrial Construction
SEGMENT INFORMATION
Property and equipment, net	14,321,956		14,058,440
Operating Segments | Building Construction
SEGMENT INFORMATION
Property and equipment, net	1,122,837		976,689
Corporate
SEGMENT INFORMATION
Property and equipment, net	$ 90,407		$ 39,276