Attachment 1: Statement of Work

Paradox Valley Unit Injection Well Failure Mode Evaluation Statement of Work

1. Introduction & Background

1.1. The U.S. Bureau of Reclamation’s (Reclamation) Paradox Valley Unit (PVU) is a component of the Colorado River Basin Salinity Control Program, a multi-project effort to control the salinity of water delivered to users in the United States and Mexico. The PVU is located in western Colorado, approximately 60 miles southwest of Grand Junction.
1.2. The PVU uses a field of shallow brine extraction wells to divert highly saline groundwater that would otherwise flow into the Dolores River, a tributary of the Colorado River. The extracted brine is transported via pipeline and injected into the Paradox Salinity Control Well No. 1 (Injection Well), a 16,000-foot-deep Class V disposal well located at the edge of Paradox Valley. The well was completed in 1988, and long-term injection operations began in 1996. This process has resulted in the disposal of an average of 100,000 tons of salt annually from 1996 through 2018, and recently approximately 65,000 tons per year.
1.3. The disposal well is permitted to operate at surface pressures up to 5,350 pounds per square inch (psi), corresponding to downhole pressures of approximately 12,000 psi, which exceeds the fracture closure pressure of the injection formation. The well was originally designed and permitted with a maximum allowable surface injection pressure (MASIP) of 5,000 psi; however, this limit was later increased to 5,350 psi in response to rising operating pressures. In addition, injection rates have been progressively reduced, and various injection strategies have been implemented to manage pressures and minimize risk from induced seismicity. 1.4. In March 2019, a magnitude (Mw) 4.5 earthquake occurred approximately 1.6 km southwest of the injection well, prompting a shutdown in accordance with Reclamation protocol. The injection well remained largely shut in from March 2019 to June 2022 to allow for detailed analysis of the event, aftershocks, and future seismic risk.
1.5. Injection resumed in June 2022 for a six-month test at a reduced rate to evaluate well performance and seismic response following the prolonged shutdown. Based on the results Reclamation elected to continue injection at the reduced rate for additional testing. Injection will continue until seismic risk mitigation strategies are developed and a determination is made regarding future well operations, or unfavorable conditions are observed.