A major, months-long audit of the city’s utilities department, sparked by a public outcry over high water bills, concluded that 2,750 water bills sent to San Diego residents last year were incorrect and had to be readjusted while discovering that 10 meter readers accounted for 71 percent of the errors. The city audit released Thursday also found that meter readers figured out how to bypass an accuracy check required when meters are read and the city’s Public Utilities Department doesn’t measure the performance of its 36 meter readers.