Phase 1: 125MW / 500MWh energy storage
Phase 2: 500MWh energy storage expansion
Completion date: 2026
EPC
Mortenson was selected as the engineering, procurement, and construction (EPC) contractor for the Tumbleweed BESS project, a cutting-edge 125MW / 500MWh energy storage facility located in Rosamond, California. Utilizing BYD’s CubePro technology, this project supports California’s clean energy goals by providing grid stability and renewable energy integration.
Environmental Support: Mortenson played a critical role in helping the customer navigate complex front-end environmental challenges, ensuring the project could move forward smoothly.
VDC & Prefabrication: Tumbleweed utilized large-scale prefabrication of underground conduit, improving installation speed and quality.
Cable Tray Innovation: This project was among the first in California to fully implement cable tray systems for DC cabling, enhancing safety and maintainability.
Substation Support: Although the substation was not part of Mortenson’s scope, the team stepped in to assist the customer in mitigating issues, demonstrating Mortenson’s commitment to partnership and project success.
Engineering Excellence: Mortenson Engineering Services (MES) served as the Engineer of Record (EOR) for electrical design.
Mortenson was also selected as the EPC partner for Phase 2 of this project, which doubled the site’s energy storage duration from 4 to 8 hours—without increasing MW capacity. This unique expansion to 125MW / 1,000MWh presented new engineering and execution challenges, making it a first-of-its-kind effort for Mortenson.
The Tumbleweed Expansion project built upon the VDC foundation utilized for the original Tumbleweed project. This VDC coordination effort greatly enhanced the pre-fabrication process and streamlined the underground installation coordination with piles and the existing site tie-ins.
In preparation for the commissioning phase of the project, the team focused on intense coordination around the commissioning scope of the project with the customer months in advance. As the system is a first-of-its-kind expansion to an existing BESS site for Mortenson, it serves as a testament to Energy Storage team’s industry-leading commissioning team.
