Kathryn (Katie) Ust is an associate attorney at Salmon, Lewis & Weldon, PLC, where her practice focuses primarily on water law, energy law, and environmental law.  Prior to joining Salmon, Lewis & Weldon, Katie worked as a Staff Attorney for the Arizona Corporation Commission (ACC), where she handled rate cases, power plant and transmission line siting cases, and appeals of ACC decisions in Maricopa County Superior Court and the Arizona Court of Appeals.  At Salmon, Lewis & Weldon, Katie uses her ACC experience to advise clients on a variety of ACC proceedings, including rate cases, policy-making dockets, and special contract proceedings.

As part of her water law practice, Katie assists clients with securing water rights in compliance with Arizona’s Groundwater Management Act.  She also represents a major water provider client in the Arizona General Stream Adjudications for the Gila and Little Colorado River Systems and Sources.

Katie represents clients in a range of environmental compliance and litigation matters, including compliance with the National Environmental Policy Act (NEPA); Endangered Species Act (ESA); Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); and Underground Storage Tank (UST) laws and regulations.

Representative Professional Experience

• As a Staff Attorney for the ACC, successfully defended three ACC decisions on appeal (two before the Maricopa County Superior Court and one before the Arizona Court of Appeals).
• Represents data centers in negotiating and securing approval of contracts for electrical infrastructure construction and electric service.
• Advises clients on ACC proceedings, litigation, and policy.
• Represented major water supplier in trial related to the subflow zone delineation for the Verde River Watershed.
• Represents major water supplier in various proceedings in the General Stream Adjudications for the Gila River and Little Colorado River Systems and Sources.
• Assists clients with obtaining water service and water rights in compliance with the Groundwater Management Act.
• Advises clients on Arizona groundwater law governing groundwater use inside and outside Active Management Areas.
• Advises clients on evolving groundwater legislation and policy.
• Advises clients on NEPA, ESA, and CERCLA compliance and litigation.
• Represents clients in environmental enforcement proceedings.

Honors and Awards

• Sandra Day O’Connor College of Law, Mentorship Initiative for Sustainability Law, 2025 – 2026 Mentor of the Year

Professional & Civic Activites

• State Bar of Arizona, Environmental and Natural Resources Law Section Executive Council (2023-Present)
• Sandra Day O’Connor College of Law, Mentorship Initiative for Sustainability Law, Attorney Mentor (2022-Present)

Memberships & Affiliations

• American Bar Association, Section on Environmental, Energy, and Resources Law
• State Bar of Arizona, Environmental and Natural Resources Law Section
• Maricopa County Bar Association, Environmental and Natural Resources Law Section