May be of Hellenistic origin when cistern system went out of use.
For a general note on the cistern see Nb. ΟΕ III, pp. 246 ff.
Objects from B 586 various depths (no subdivision): S 2324-S 2330,
P 34894, ... Late 2nd-early 6th c. A.D ... Agora VI, p. 99 ... Agora XXI, p. 98 ... Hesperia Suppl. 4, p. 101.