Engaging the Community in Determining Water Aesthetics -The ‘Decision H2O’ Program

摘要

The pressing need for additional water supplies is driving utilities to seek alternatives to supplement or replace their historic water resources. The use of these alternative supplies can lead to changes in the aesthetic characteristics of the delivered water. Tucson Water has been increasing its use of an imported surface supply that differs significantly in TDS from the groundwater the community has traditionally relied on. The utility developed a public involvement program to engage customers in the decision of whether to accept rising TDS levels or to build a reverse osmosis facility to stabilize mineral levels. The “Decision H2O” program offers lessons to other utilities as they deal with customer responses to a changing water supply. In the search for additional water supplies, a rising number of utilities find themselves seeking alternative water supplies to supplement or replace their historic water resources. In many cases, use of these alternative supplies means that the aesthetic characteristics of the potable water delivered to customers will change over time. Tucson Water has been increasing its use of imported Colorado River water, which varies significantly in mineral content (measured as Total Dissolved Solids or TDS) from the community’s historic groundwater resources. The utility, continuing its primary focus on involving customers in water resource decisions, developed the “Decision H2O” program to engage customers in the choice of whether to accept rising TDS levels, or to build and operate an enhanced treatment facility to stabilize mineral levels. Since 2001, Tucson Water has successfully operated the Clearwater Recharge and Recovery Facility. At the Clearwater facility, Colorado River water, delivered via the Central Arizona Project, is put into constructed basins and allowed to percolate through the soils to reach the groundwater below. Specially constructed production wells recover the resulting blend of recharged river water and groundwater for delivery to customers. Because the TDS of Colorado River water is roughly twice that of the average groundwater in the Tucson area, mineral content in the blended water is rising over time as the percentage of river water increases. In the late 1990s, as the Clearwater facility was being designed, Tucson Water’s customers were asked to select an acceptable blend of recharged Colorado River water and groundwater. A majority of customers preferred a blend of 50% Colorado River and 50% groundwater, a TDS of approximately 450 mg/L. By designing the Clearwater recovery system to meet customer preferences, Tucson Water will be able to maintain the