A site plan shows how a project will sit on its land: buildings, parking, access, grading, stormwater, utilities, landscaping and trees. Before a building permit, the local government reviews it against the zoning and development codes, usually through several departments at once, such as planning, engineering, fire, transportation and stormwater.
The review is rarely one pass. Reviewers send comments, the design team revises and resubmits, and the plan goes around again until every department signs off. The number of rounds is often what decides the timeline, and it depends heavily on how complete and code-compliant the first submittal is.
Some site plans are approved by staff; others go to a technical review committee, a design review board or the planning commission, which adds a meeting calendar and public notice. Approvals from outside agencies, such as a state highway department for a driveway or an environmental agency for stormwater or wetlands, can run alongside or after the local review.
The best guide to how long a plan will take is how long similar plans took in the same place, and which comments they drew, so the answers are in the first submittal. In Charleston, South Carolina, for example, site plans pass through a technical review committee before approval.