Preferentially converts 3,5-dichlorocatechol as opposed to other chlorinated catechols. Retains diminished activity toward non-chlorinated substrates. 3,5-dichlorocatechol + O2 = (2E,4E)-2,4-dichloromuconate + 2 H(+) Binds 1 Fe(3+) ion per subunit. Aromatic compound metabolism; 3-chlorocatechol degradation. Belongs to the intradiol ring-cleavage dioxygenase family.