They may fix damaged water channels on Chol Hamoed, but only if it is needed for the festival.

This law applies to an individual, but for the public, it is permitted even if it is not for the festival.

(Gemara): It is like the case of the bathhouse of Sachusa that became unusable and R. Abahu permitted them to fix it on Chol Hamoed.

If something involves toil and they left it until the festival to be fixed, they suggested that even if it for the public, it may not be done.

Nevertheless, it is permitted - if they do not fix it now, when people are not working and labor is cheap, they will never fix it.

The water channel in Tzipori split open. Chevraya thought that based on our Mishnah, it was permitted to fix it on Chol Hamoed. R. Yirmiyah prohibited it.

R. Pinchas: R. Yirmiyah only prohibited it because of the noise from using a hammer (which R. Yochanan ben Zakkai prohibited on Chol Hamoed).

The cemetery of Bar Mekatya became damaged on the festival. Rav Chuna wished to permit it because the Mishnah permits "all public needs".

R. Mana to Rav Chuna: Did Shmuel not teach in a Beraisa that one may only plaster up the cracks (but not completely fix it)?

The Mishnah had taught: (Fixing means that) they may clear out the dirt that fell into the channel.

This is like the Mishnah in Mikvaos that teaches about one who digs and hollows out a pipe.

The Mishnah had taught: One may carry out all public needs. The following are considered public needs - Judging monetary cases, cases of life and death, cases of lashes, redeeming captives, consecrations to the Temple, giving the Sota to drink, burning the Red Heifer, breaking the neck of the calf (if an unidentified person was found murdered), boring the ear of the Jewish slave; purifying the leper and removing the shoe from its mould, although it may not be returned to the mould.

The Mishnah had taught: They may mark the graves.

Question: Did they not mark them in Adar?

Answer: Rain fell since then and washed away the markings.