Talmud for Moed Katan 1:2

רַבִּי אֶלְעָזָר בֶּן עֲזַרְיָה אוֹמֵר, אֵין עוֹשִׂין אֶת הָאַמָּה בַתְּחִלָּה בַּמּוֹעֵד וּבַשְּׁבִיעִית, וַחֲכָמִים אוֹמְרִים, עוֹשִׂין אֶת הָאַמָּה בַּתְּחִלָּה בַּשְּׁבִיעִית, וּמְתַקְּנִין אֶת הַמְּקֻלְקָלוֹת בַּמּוֹעֵד. וּמְתַקְּנִין אֶת קִלְקוּלֵי הַמַּיִם שֶׁבִּרְשׁוּת הָרַבִּים וְחוֹטְטִין אוֹתָן. וּמְתַקְּנִין אֶת הַדְּרָכִים וְאֶת הָרְחוֹבוֹת וְאֶת מִקְווֹת הַמַּיִם, וְעוֹשִׂין כָּל צָרְכֵי הָרַבִּים, וּמְצַיְּנִין אֶת הַקְּבָרוֹת, וְיוֹצְאִין אַף עַל הַכִּלְאָיִם:

R. Elazar b. Azaryah says: It is forbidden to make an amah [an irrigation ditch (so called because it is a cubit (amah) wide and a cubit high)] ab initio on Chol Hamoed [(If it were never there, it is not made ab initio on Chol Hamoed, for doing so entails undue exertion)], and on shevi'ith, [for it gives the impression that he is digging the soil on shevi'ith]. The sages say: An amah may be made ab initio on shevi'ith, and the defective ones may be repaired on Chol Hamoed [If soil fell in and impeded the flow, this may be corrected, but they (the amoth) may not be made ab initio on Chol Hamoed. The halachah is in accordance with the sages.], and water obstructions in [drinking troughs] in the public domain may be cleared and they (the troughs) may be cleansed [of pebbles, chips, and clods that fell therein.] And it is permitted to repair the roads, the thoroughfares, and the mikva'oth, and to tend to all public needs. And it is permitted to mark graves [They would crumble lime and spill it on the grave to serve as a sign to the passersby not to pass through a place of uncleanliness.], and they would also go out for kilayim. [Messengers of beth-din would go out to see if the fields had been sown with kilayim (forbidden admixtures) and to uproot them. For they received their wage from the lishkah contributions, and they could be hired cheap on Chol Hamoed, for they were idle then.]

Jerusalem Talmud Shekalim