Water Transfer Pilot Project

What Are We Evaluating with the Pilot Project

What are some of the things we're considering with surface water transfers and will be evaluating with our pilot project?

The chemical characteristics of groundwater and water from surface water sources (reservoirs and rivers) are different. Surface water supplies will tend to be softer with lower levels of naturally occurring minerals that, without treatment, will tend to be more corrosive than groundwater supplies. Surface water will also tend to have higher levels of total organic carbon than groundwater. While the levels of organic carbon in surface water sources varies considerably, disinfecting water containing organic carbon as part of the water treatment process results in the formation of disinfection byproducts such as trihalomethanes and haloacetic acids. Unless the organic carbon is removed before the disinfection step in the treatment process, disinfection byproducts can continue to form as the water travels through the distribution system.

Switching sources or blending sources can be a tricky business that requires good understanding of the potential issues, careful and informed management of system operation and good monitoring and feedback loops to adapt operations if and as needed to protect public health and to minimize any aesthetic issues resulting from changing water quality in either water system or customer property plumbing.

Recent issues with source water changes in Flint, Michigan and Fresno, California, for example, are reason to exercise prudence in planning for implementation of water transfers, and two issues have been identified as the focus of efforts to plan for and manage during the implementation of the pilot water transfer pilot project described earlier:

The potential for the City's softer surface water to cause corrosion of water system or property side plumbing in the District's system which could result in aesthetic issues such as red or discolored water, or of increased levels of corrosion byproducts such as lead and copper in first flush water; and the potential for continuing formation of disinfection byproducts once water from the City's system enters the District system, which may be exacerbated by the low turn-over of stored water related to low demand in parts of the District's distribution system.

A significant benefit of the planned pilot project is the opportunity to further understand these issues and learn about what approaches are necessary to implement a successful in lieu water transfer program.