Navajo-Gallup Water Supply Project - San Juan Lateral Source Water Blending and Corrosion Studies
The Navajo-Gallup Water Supply Project (NGWSP) is being constructed to convey potable water from the San Juan River to the eastern Navajo Nation, southwestern Jicarilla Apache Nation, and the city of Gallup, New Mexico. These areas currently rely on community water systems (CWS) sourced by depleting groundwater supplies of poor quality which are inadequate to meet current and future demands. Ground water levels for the city of Gallup have dropped ~200 feet over the past 10 years and over 40 percent of Navajo Nation households haul water to meet daily needs. This project focuses on quantifying and characterizing CWS water distribution materials to determine the possibility of and plan mitigation measures for material corrosion and scale release (iron, manganese, arsenic, lead, etc.) from changing water sources to the NGWSP.
A change in source water for an established CWS requires in-depth analysis to ensure that chemistry changes will not negatively impact infrastructure and the quality of water at point of use locations (residential, commercial, etc.). In 1992, the City of Tucson introduced treated Colorado River Water via the Central Arizona Project at a cost of $5 billion, changing sources to the groundwater served CWS. The changes in water quality increased the rate of corrosion which led to pinhole leaks in distribution system mains and the release of significant quantities of iron and manganese to point of use sources - registering 14,000 complaints and $2 million in settlement damages to end users - ultimately resulting in the source water being changed back to groundwater. Another case where impacts of changing water sources were not studied beforehand, and operators failed to formulate and enact stabilization and corrosion prevention plans is the 2014 Flint Water Crisis. The city of Flint, Michigan switched to a seemingly similar quality source water which ended up being significantly more corrosive. The new source finished water corroded established scal
Need and Benefit
This project will inform the proper startup and operational procedures to be utilized when NGWSP finished water is introduced into CWS. It is necessary to understand what exists in the current distribution system, the impact of changing water quality and how to mitigate corrosive release of toxic and / or constituents that are perceived to be toxic. Public trust and project success are dependent on the delivery of high-quality potable water to end users and demonstrate Reclamations' commitment to manage, develop, and protect water and related resources in the interest of the Native American and American public.
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