Marana Water News: Sewer billing 101 - WQA and more

Currently, Marana Water has 6,747 water accounts, and of these, 5,692 are sewer customers. The water and sewer charges are listed on one statement for customer convenience. While water consumption charges are relatively easy to calculate, the sewer billing is a little more intricate. Since there is no meter on the outflows from homes and businesses, other means are required to determine monthly sewer charges.

In the Marana Water service area, Pima County Regional Wastewater Reclamation Department (RWRD) and Marana Water provide sewer services to these 5,600 connections. Both providers use similar methods for calculating a sewer bill, however Pima County RWRD uses different units in their calculation. Marana Water calculates the charges based on a per 1,000 gallon rate while Pima County RWRD uses hundred cubic feet (CCF), which is the equivalent of 748 gallons, when determining sewer charges.

Similar to the water side, the sewer calculations have a monthly minimum fee and a rate on the amount of consumption, or a volumetric calculation. Since sewer outflows are unmetered, an average is calculated based on the three winter months called a Winter Quarter Average (WQA). The winter months of December, January, and February are used because, in theory, these months should show typical indoor water use since irrigation systems and pools are not as heavily used. This indoor use is what Marana Water wants to capture since it is a good measure of what water has been discharged into the sewer system.

  Example of a WQA calculation

Example of a WQA calculation

  Sewer billing example

Sewer billing example

Calculated every July using the previous December, January, and February, the WQA is the maximum sewer consumption per account. Each month, a customer is billed either the WQA or their monthly consumption, whichever amount is lower. For example, a customer has a WQA of 5,000 gallons and a July water use of 7,000 gallons. The customer will be billed the 5,000 gallon amount rather than the actual water use of 7,000 gallons. Using the WQA allows for consistent sewer billing month to month, and gives the customer the ability to adjust their average by conserving water during the winter months.

As mentioned above, there are some small differences between Marana and Pima County RWRD sewer customers. The monthly minimum rates for a residential connection are the same, but Pima County RWRD has several classes of sewer customers, for example, seated restaurants, laundromats, or bakery customers. Each of these classes have different volumetric rates based on the effort to treat the discharged water. For more information on Pima County RWRD rates and sewer classifications, please click here.