The Phoenix Lake Preservation and Restoration Project

Project Summary

Phoenix Lake is an 88-acre water storage reservoir owned and operated by the Tuolumne Utilities District (TUD). It serves as the primary drinking water source for the communities of Sonora, Jamestown, Scenic View, and Mono Village. Additionally, it supports CAL FIRE helicopter operations, aquatic habitats, and public recreation. Over time, sedimentation significantly reduced the lake’s storage capacity. In 2010, TUD received a grant from the Sierra Nevada Conservancy to prepare the Phoenix Lake Preservation and Restoration Plan (PLPRP) to increase lake capacity, reduce watershed sedimentation, improve water quality, and expand wetland habitats.

Our Role

Montrose (Formerly Horizon Water and Environment) played a crucial role in developing the PLPRP by:

• Conducting technical studies and evaluating lake stressors.
• Identifying key strategies to restore and preserve the lake’s functions and values.
• Using gathered data to determine the rate of lake sedimentation and developing a plan to restore lake capacity, enhance wetland habitats, and improve water quality.

When TUD obtained a second grant to implement portions of the PLPRP, we:

• Prepared documents and plans to support the removal of approximately 400,000 cubic yards of sediment.
• Evaluated the suitability of materials for placement around the lake, reuse in the lake, and for commercial uses.
• Conducted reconnaissance-level wildlife surveys focusing on potentially suitable habitats for special-status amphibians.
• Performed topographic and bathymetric surveys to support the design and permitting of the project.
• Prepared an Initial Study/Mitigated Negative Declaration (IS/MND) for the project, which was adopted in fall 2017.
• Successfully obtained all regulatory permits for the project by early 2020.

Challenges

We worked closely with TUD to navigate the complex regulatory landscape and ensure environmental compliance. This involved:

• Developing strategies for working with regulatory agencies.
• Ensuring all environmental constraints were considered during project planning.
• Addressing various environmental considerations and compliance requirements.

Outcome

Implementation of the PLPRP began in July 2020. We provided biological monitoring and regulatory agency coordination during the construction process, working closely with TUD, and construction manager Anchor QEA, and contractor Steve Manning Construction, Inc. Over 160,000 cubic yards of sediment were removed to restore lake capacity, improve water quality, and protect wetland resources. Sediment removal in the main body of the reservoir was completed in September 2020. We continue to provide biological and regulatory compliance support services for the PLPRP.