By AGILE Consulting Engineers, Solar PV and Battery Energy Storage Systems (BESS) specialists.
Construction is where a solar photovoltaic (PV) or battery energy storage system (BESS) project’s paper design meets soil, weather, subcontractor turnover and schedule pressure, usually all at once. An Owner’s Engineer (OE) on site during this phase is not there to manage the build, that is the Engineering, Procurement and Construction (EPC) contractor’s job. They are there to independently confirm that what is actually being built matches what was designed, specified and contracted for, and to raise the alarm early when it does not.
Table of Contents
- How the Role Shifts Once Construction Starts
- Monitoring Against Design and Contract
- Quality Assurance Oversight
- Tracking Program and Payment Milestones
- Flagging Deviations Early
- Reporting to the Owner
- Leading Into Commissioning
- What to Do Next
- FAQ
How the Role Shifts Once Construction Starts
During design and procurement, an OE’s work is largely desk based, reviewing drawings, specifications and contract schedules. Once construction mobilises, that work becomes physical and continuous. Site visits, inspections, witnessing of tests, and review of daily and weekly progress reporting replace, or sit alongside, document review as the core activity. The frequency of site presence generally scales with project complexity and risk, from periodic visits at defined hold points on a straightforward project through to a more continuous presence for larger or more complex BESS installations where the consequences of a missed defect are higher.
What does not change is the underlying purpose. The OE is still working for the owner, still independent of the EPC contractor, and still measuring what they observe against the approved design and contract, not against the contractor’s own account of progress.
Monitoring Against Design and Contract
The most basic construction-phase activity is confirming that installed work matches the issued-for-construction drawings and specifications. For a solar array this covers items such as pile embedment depths, torque values on structural connections, cable routing and containment, and earthing continuity. For a BESS it extends to enclosure placement and clearances, fire detection and suppression system installation, thermal management system commissioning readiness, and the physical arrangement of switchgear and protection equipment relative to the approved layout.
This is deliberately unglamorous, detailed work. The value is cumulative rather than dramatic: a plant where every stage of construction has been checked against design tends to perform closer to its design intent and present fewer surprises during commissioning than one where compliance was assumed rather than verified.
Quality Assurance Oversight
Most EPC contractors run their own quality assurance and quality control (QA/QC) processes, including inspection and test plans, hold points, and internal sign-off procedures. An OE’s role is not to duplicate that process but to provide independent oversight of it, reviewing QA/QC documentation for completeness and consistency, attending or witnessing selected hold point inspections, and spot checking that the contractor’s internal sign-offs actually reflect what is on the ground.
This oversight function matters because a contractor under schedule pressure has an incentive to move fast, and internal QA processes can occasionally be treated as a formality rather than a genuine control. An OE applying consistent scepticism to that documentation, and being willing to independently verify rather than simply accept a sign-off, is one of the more direct ways construction-phase oversight earns its keep.
Tracking Program and Payment Milestones
Construction contracts are typically structured around a sequence of milestones tied to both schedule and payment, such as mobilisation, civil works completion, mechanical completion, and readiness for energisation. An OE’s role includes independently verifying that claimed milestones have genuinely been achieved before recommending payment certification, rather than that work has simply been reported as complete by the contractor.
This is a point of genuine tension on some projects, since the contractor has a direct commercial interest in milestones being certified as early as possible, while the owner’s interest is in payment being tied to verified, not claimed, progress. An OE’s independent verification is what allows the payment mechanism in the contract to function as intended rather than becoming a point of dispute.
Flagging Deviations Early
Deviations from design or specification are a normal part of construction on any project of this scale, arising from site conditions, supply chain substitutions, or practical constructability issues discovered once work is underway. What matters is how quickly a deviation is identified, assessed and resolved. An OE’s construction monitoring is structured around catching deviations close to when they occur, documenting them through a formal non-conformance process, and assessing their technical significance before recommending how the owner should respond, whether that is accepting a variation, requiring rework, or escalating a more serious contractual issue.
The cost of a deviation generally increases sharply the later it is caught. A cable routing error identified before backfill is a straightforward correction. The same error identified during commissioning, or worse, after energisation, can mean significant rework, schedule delay and cost that a timelier catch would have avoided.
Reporting to the Owner
Regular, structured reporting is a core part of the construction-phase OE role, translating site observations, QA findings and milestone verification into a form the owner’s project team, and often their financiers, can actually use for decision making. This typically includes periodic progress reports covering schedule status against the contract program, outstanding non-conformances and their resolution status, and any emerging risks to cost, schedule or quality. Where a project is also subject to lender monitoring requirements, this reporting discipline tends to align closely with, though it does not replace, whatever independent reporting a Lender’s Technical Advisor (LTA) requires under the financing agreement.
Leading Into Commissioning
Construction-phase monitoring feeds directly into commissioning readiness. An OE tracking punch list items, non-conformance closure and mechanical completion status through construction is building the record that determines whether a plant is genuinely ready for Factory Acceptance Testing (FAT) of major equipment and Site Acceptance Testing (SAT) of the integrated plant, or whether commissioning is likely to surface issues that should have been resolved earlier. A construction phase run with discipline tends to produce a smoother, faster commissioning process, because the plant arrives at that stage without a backlog of unresolved construction issues competing for attention with genuine commissioning activity.
What to Do Next
If a project is approaching mobilisation without an independent construction monitoring arrangement in place, this is the point where establishing that oversight can meaningfully change how smoothly the build and commissioning phases run. We’ve helped project teams set up construction-phase monitoring and reporting structures before contractors mobilise on site, and it is a far more useful conversation to have before ground is broken than after the first non-conformance has already gone unnoticed.
FAQ
Does an Owner’s Engineer manage the construction contractor?
No, contract and construction management remains the EPC contractor’s responsibility, the OE independently monitors and verifies that work against the approved design, specification and contract.
How often is an Owner’s Engineer on site during construction?
It varies with project scale and risk, ranging from periodic visits at defined hold points to a more continuous presence, and is typically agreed as part of the OE’s scope before construction mobilises.
What happens when an Owner’s Engineer identifies a non-conformance?
It is documented through a formal non-conformance process, assessed for technical significance, and tracked through to verified resolution before being considered closed.
Why does milestone verification matter if the contractor already reports progress?
Contractors have a commercial interest in milestones being certified early, so independent verification ensures payment is tied to genuinely completed and verified work rather than self-reported progress.
Does construction-phase monitoring replace a Lender’s Technical Advisor’s site reporting?
No, the two typically run in parallel and often align closely in content, but an OE’s monitoring is for the owner while an LTA’s monitoring serves the lender’s own due diligence and drawdown requirements.
How does construction monitoring affect commissioning?
A construction phase with disciplined non-conformance tracking and punch list management tends to produce fewer unresolved issues heading into FAT and SAT, which generally makes commissioning faster and less disruptive.
