Fresh from his success in capturing the Erymanthian Boar, Hēraklēs is dealing with the death of two good men and a whole lot of Kentautai, so the next labour would have not only seemed unworthy of him, but also a punch below the belt. Hēraklēs must clear the dung from the stables of Augeias (or Augeas), a king of Elis in the western Peloponnesos who possessed an enormous herd of cattle. He must do this in a single day, and he must also do this alone. Those are the rules of the labour.

Before I recount the story, let us take a minute here to consider the implications: Hēraklēs is a man on a quest to purify himself of a terrible deed, the slaying of his family while in a haze induced by Hera. He is also the son of a God, Zeus, and thus in theory eligible for apotheosis, becoming a God. In order to achieve either, Hēraklēs must, however, perform his labours with honor and pride. Every labour must be something extraordinary that shows his worth. Shoveling dung from a stable does not qualify by a long shot and his quest-giver Eurystheus knows this full well. Diodorus writes on this in his 'Library of History':

"Upon the performance of this Labour he received a Command from Eurystheus to cleanse the stables of Augeas, and to do this without the assistance of any other man. These stables contained an enormous mass of dung which had accumulated over a great period, and it was a spirit of insult which induced Eurystheus to lay upon him the command to clean out this dung. [...] He accomplished the Labour in a single day, and without suffering any insult. Surely, then, we may well marvel at the ingenuity of Heracles; for he accomplished the ignoble task involved in the Command without incurring any disgrace or submitting to something which would render him unworthy of immortality." [4.13.3]

Before he left, Hēraklēs was not aware he would be able to compelte the task with honor, but left to do it anyway. Once he got to Elis, he introduced himself to Augeias and told him he would clean out the stables, if the king would sign over ownership of the cattle afterwards, or--alternatively, depending upon source--a portion of the land of Elis. Obviously, King Augeias was not happy with this arrangement; from Apollodorus' 'Library':

"Now Augeas was king of Elis; some say that he was a son of the Sun, others that he was a son of Poseidon, and others that he was a son of Phorbas; and he had many herds of cattle. Hercules accosted him, and without revealing the command of Eurystheus, said that he would carry out the dung in one day, if Augeas would give him the tithe of the cattle. Augeas was incredulous, but promised." [2.5.5]

With the deal done, Hēraklēs took Augeias' son Phyleus to witness the events that followed, and took to the stables. It was quite apparent the task would not be an easy one, especially if he wanted to get through it with his pride and honor intact. Now, it just happened to be that the stables were close to a river, named 'Alpheios'. It had its headwaters in the south-eastern corner of Arkadia, flowing the length of the country into Elis in the east, past Olympia to reach the Ionian sea. A God by the same name ruled over its waters, and was the son of Okeanos and Thetys. Pausanias, in his 'Description of Greece' says about him:

"The boundary between the territories of Lacedaemon and Tegea is the river Alpheius. Its water begins in Phylace, and not far from its source there flows down into it another water from springs that are not large, but many in number, whence the place has received the name Symbola (Meetings). It is known that the Alpheius differs from other rivers in exhibiting this natural peculiarity; it often disappears beneath the earth to reappear again. So flowing on from Phylace and the place called Symbola it sinks into the Tegean plain; rising at Asea, and mingling its stream with the Eurotas, it sinks again into the earth. Coming up at the place called by the Arcadians Pegae (Springs), and flowing past the land of Pisa and past Olympia, it falls into the sea above Cyllene, the port of Elis. Not even the Adriatic could check its flowing onwards, but passing through it, so large and stormy a sea, it shows in Ortygia, before Syracuse, that it is the Alpheius, and unites its water with Arethusa." [8.54.1 - 8.54.3]

Armed with the knowledge about the river, Hēraklēs sets to work. From Apollodorus:

"Hercules made a breach in the foundations of the cattle-yard, and then, diverting the courses of the Alpheus and Peneus, which flowed near each other, he turned them into the yard, having first made an outlet for the water through another opening." [2.5.5]

Alpheius took the dung away in one go, and I presume Hēraklēs then diverted the stream back to its origional course. By accomplishing such a great feat, Hēraklēs had completed the taks, and had not suffered on bit of dishonor. Happy with his accomplishments, he returned to the king to ask for his reward, but Augeias would not give it. Apollodorus again:

"When Augeas learned that this had been accomplished at the command of Eurystheus, he would not pay the reward; nay more, he denied that he had promised to pay it, and on that point he professed himself ready to submit to arbitration. The arbitrators having taken their seats, Phyleus was called by Hercules and bore witness against his father, affirming that he had agreed to give him a reward. In a rage Augeas, before the voting took place, ordered both Phyleus and Hercules to pack out of Elis. So Phyleus went to Dulichium and dwelt there, and Hercules repaired to Dexamenus at Olenus. He found Dexamenus on the point of betrothing perforce his daughter Mnesimache to the centaur Eurytion, and being called upon by him for help, he slew Eurytion when that centaur came to fetch his bride. But Eurystheus would not admit this labour either among the ten, alleging that it had been performed for hire." [2.5.5]

So it was that Hēraklēs had performed such a great feat of strength and smarts, without any reward: not only had he not gotten what the king had promised him, but because he had made such a contract, Eurystheus refused to pay him as well. As such, it came to be that in order to fulfill his ten labours, Hēraklēs would have to perform twelve of them, as both this one, nor the one in which he slayed the Hydra, counted towards his total.

As for Augeias; Hēraklēs would get his revenge on him after the labours were over, but for now, Hēraklēs let him be. There were many more tasks ahead of him, after all.