Augeas

Augeas was a demigod in Greek mythology. He was a demigod son of Helios and sometimes said to be one of the Argonauts.

Augeas owned the greatest number of cattle in Greece (over a thousand), but had been too greedy to pay anyone to clean the stables for about 30 years. It was one of Heracles' labors to clean the stables. He did this by rerouting two rivers so that they would rush through the stables and clean everything effortlessly.

In the Percy Jackson series, the stables of Augeas are mixed up with the flesh-eating mares of Diomedes, which Hercules also had to fetch as one of his labors.

The Battle of the Labyrinth
In The Battle of the Labyrinth, Geryon mentions Augeas. He says Augeas owns the Flesh-Eating Horse's Stables, but Triple G Ranch watches over them for a "small monthly fee".