Statistics released Friday show 3,214 cars passed through the checkpoint, with officers screening about 500 of them and arresting two on suspicion of driving drunk. Police also cited 17 people and impounded 12 vehicles.
City Manager Allan Roeder explained that planning commissioners report to the City Council and do not have authority over police.
Roeder did not elaborate on the nature of the city attorney's investigation, though he did confirm one is taking palce.
He said he was aware of the incident and the city is gathering all documents, field observations, including audio recordings and any other related information to hand over to the city attorney's office.
The checkpoint was funded by the California Office of Traffic Safety. Officials with OTS said checkpoints are meant as reminders to the public about police presence and the dangers of drinking and driving. Saturation patrols, where more officers are on the streets looking for impaired drivers, are typically used for increased enforcement.