IS TECHNICAL DUE DILIGENCE IN DRAINAGE ACTUALLY INFORMING DECISION MAKING
Traditionally, the role of a drainage survey in TDD ahead of an acquisition, disposal or Vendor’s Pack was highlighting the defects found in the system, and supplementing them with images and the location within the site.
However, this doesn’t actually inform any decision, it fails to address the questions that actually impact investment:
- What are the immediate and long term risks associated?
- What is the best solution?
- What is the cost?
We found, particularly with the industry standard Wincan report, that only the visible defects were being highlighted, and nothing more.
This isn’t informative, it is only descriptive.
As below ground specialists, we understand the potential risks that exist beneath the surface. Because these issues are not visible above ground, it is critical that every hidden element is thoroughly assessed, as serious problems can easily go unnoticed and the consequences can be significant.
Risk Doesn’t just Lie Within Defects
Liabilities can come from numerous different aspects within the drainage system.
From mis-connections to poor maintenance, there is significant risk of failure, costly repairs or legal non-compliance hidden in other areas of the system, not just cracks or displaced joints.
Have you considered the implications for drainage risk if the site is within a Groundwater Source Protection Zone (GWSPZ)? This is unlikely to be covered adequately by a Phase 1 Environmental and would not be considered a defect, therefore would go unnoticed. The consequences of pollution occurring within a GWSPZ are severe and it is a liability that would otherwise go unnoticed.
On average, we find that approximately 30% of defects in the system relate to environmental risk, and in 2024, the remedial costs of these were valued at over £8m in total; an enormous value of risk to ignore by inadequate TDD.
Understand The Current & Future Risks
Not all defects identified within a drainage system will deteriorate to the point of compromising a site. Some issues may remain dormant long-term, while others can escalate rapidly and require immediate intervention. For this reason, a report that merely lists defects, without assessing their likely risk and the cost of solution offers limited value when informing investment decisions.
Our experienced consultancy team has extensive knowledge across all aspects of drainage and groundworks. This allows us to provide informed insight into specific defects, assess their potential impact, and recommend appropriate solutions to assist clients mitigate risk before issues escalate into costly consequences.
That said, implementing annual maintenance remains best practice. Regular inspections ensure systems continue to operate efficiently and that emerging issues are identified and addressed at the earliest possible stage.
What To Consider When Instructing a Drainage Survey for TDD
It is vital that when considering TDD for drainage systems, the following is included in the report;
- All associated risks are assessed and justified, not just structural defects
- The operational performance of the system is evaluated, including general assessments of capacity and suitability
- The site is assessed for legal compliance
- Environmental risk via the drainage systems
- Long-term costs and maintenance requirements are listed
- Clear, prioritised recommendations are provided, aligned with risk, compliance and asset lifespan
This will ensure all risks are appropriately addressed, actually informing strategic decision making.
Our Approach
At WJ Shirley, we have been Transactional specialists since 1960 so we understand the importance of a survey that is actually going to support decision making.
So, our drainage survey reports are bespoke and cover every associated risk, bridging the gap between a Phase 1 Environmental and a building survey.
We also appreciate the value of a break down in costs per year for 5 years to support forecasts, along with the type of spend and the reason.
Providing this along with a description, image and location of the risk means the liability can be completely understood when it comes to commercial property and accurately inform decision making.
The value of commercial property is high and a vast amount of risk is always going to be involved. However, by instructing reliable, strategic and informative TDD for the drainage system is critical, and the value of instructing a drainage specialist focused around the commercial property is critical.