William Faulkner uses the same setting in Light in August that he does in many of his other novels (including Absalom! Absalom!, Satoris, and The Sound and the Fury). The setting is fictional and "owned" by William Faulkner.
Bucolic refers to the pleasant nature of the countryside. Given the two main settings of the novel are in private homes, the movement of the text automatically separates itself from an encompassing setting. In fact, by using the homes as a setting, the removal from the urban environment is even more substantial. Since the homes are in the country, by placing the main action of the novel in the homes themselves, the life of the city seems to be twice removed. This "twice-removal" speaks to direct opposition of urban life.