The operating ratio methodology assists the small water and wastewater utilities in staff assisted rate cases by substituting operation and maintenance expenses for rate base in calculating the amount of return component of revenue requirement. The operating ratio methodology will only be used for those utilities whose rate base is no greater that 125 percent of operation and maintenance expenses and will only be used for utilities that continue to qualify for a staff assisted rate case. The operating ratio methodology allows eligible utilities to receive margin of 12 percent of the utility’s operation and maintenance expenses. Eligible utilities will not receive more than a $15,000 margin.