The construction worker was building a dam in a forest in the mountain range near Fuchsia City. He was getting frustrated with a group of Diglett that were wrecking the road to the construction site, making it impossible for the supplies to build the dam to get there.
The construction worker decided that he should call for any able Pokémon trainer who is traveling through the area to help him get rid of the Diglett. He offered a reward of a 6-night, 7-day stay at the famous Giva Hot Springs Resort for the trainer that dealt with the Diglett situation.
After realizing that the Diglett were just protecting their home, he decided to call off the dam construction project so that it wouldn't flood the Diglett and Dugtrio's home.