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How Due Diligence Can Make or Break Your Utility-Scale Solar Project


In the development of utility-scale solar projects, the importance of a well-conducted design and engineering due diligence process cannot be overstated. This phase is critical to ensuring a project’s success, as it ensures utmost efficiency by having all stakeholders pre-approve key design decisions in advance of the project being awarded. By addressing both the major electrical and civil/structural aspects of the project beforehand, project risks are drastically mitigated and regulatory compliance is assured. 


Key Categories of Due Diligence


  1. Civil/Structural Due Diligence: One of the complexities in solar project development arises from local jurisdictional requirements, which vary significantly even within the same state. Civil due diligence, which includes assessing water management, stormwater pollution prevention plans (SWPPP), and landscaping, becomes a meticulous task as regulations differ between counties, municipalities, and state departments. These distinctions affect access roads, grading plans, and lines of demarcation on-site, all of which must align with local transportation, environmental, and aesthetic guidelines. For example, the way a project screens its design with plants or buffers may vary according to both local preferences and seasonal changes. Addressing these variables early ensures smoother project approvals and avoids delays.


  1. Electrical Due Diligence: While civil regulations differ across small jurisdictions, electrical standards tend to be more consistent within the same utility provider’s service area. However, electrical due diligence involves gathering vital information for substantiation reports and ensuring compliance with utility-specific requirements. Delays in communication with utility providers can significantly hinder a project, making it essential to start identifying potential gaps in utility requirements early in the design process. Managing these dependencies upfront ensures that once the design is finalized, all necessary information is on hand, avoiding hold-ups during the permitting and construction phases.


Engaging Stakeholders: EPCs and Developers


A successful due diligence process involves more than technical assessments—it requires strong relationships with all stakeholders, particularly the owners and EPCs. Fostering early communication between EPCs and owners ensures that both sides share a clear vision for the project. A key insight gained through Castillo Engineering’s nearly three decades of experience is the benefit of engaging owners early on to understand their specific priorities and expectations for the project. This not only aligns design efforts with owner goals but also facilitates faster decision-making during the design phase, since owners can provide quicker approvals based on pre-established relationships.


Additionally, some projects involve a financial institution’s reviewer, often referred to as the "independent engineer," who has final approval on substantiation reports. Understanding their expectations early can prevent costly rework. By addressing any unique requests upfront, Castillo has been able to streamline the review process and significantly reduce approval times.


Best Practices for Efficient Due Diligence


These are the best practices for conducting efficient due diligence, especially when working with EPCs before contracts are awarded:

  • Comprehensive Early Reviews: Before design begins, Castillo conducts a thorough review of all project parameters and requirements, ensuring nothing is overlooked. This early-stage clarity identifies gaps that could delay progress later and helps manage client expectations.

  • Pre-Approved Standardized Designs: For repeat owners and EPCs, having a standardized design process where key elements are approved months in advance significantly speeds up the design process when a project is awarded. Pre-approvals allow all stakeholders to hit the ground running, leading to more efficient project execution.

  • Proactive Communication: Regular, proactive communication with utilities, developers, and financial reviewers ensures that potential issues are addressed early. With utilities often being slower to respond, initiating conversations well in advance of submission deadlines avoids bottlenecks later in the process.


Lessons Learned 


Castillo’s due diligence process has been refined through trial and error, allowing the company to foresee potential issues and incorporate lessons learned from past projects. By implementing and enforcing strict due diligence protocols, Castillo ensures that its designs not only meet regulatory requirements but also reduce risk for all stakeholders involved.

In addition, Castillo’s hands-on approach to risk management through early identification of design criteria and dependencies reduces the likelihood of project delays. This has proven to be a key factor in retaining clients, as Castillo’s ability to provide timely solutions and avoid costly setbacks builds long-term trust.


Proactive due diligence in utility-scale solar projects is paramount. It serves as the foundation for risk mitigation, regulatory compliance, and successful project delivery. Castillo’s comprehensive due diligence process, which includes both civil and electrical assessments, fosters smoother transitions from design to construction and helps EPCs navigate the complexities of working across various jurisdictions. By focusing on early engagement with owners, standardized designs, and proactive communication with utilities, Castillo ensures that solar projects are completed efficiently and effectively, paving the way for long-term success in the industry. If you’re looking for advanced design and engineering support with your utility-scale solar project, get in touch with a technical expert at Castillo. 

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