By Dan Robbins – Senior Project Manager
Structures exposed to harsh marine environments battle the elements every day – even before they are fully constructed. For this reason, waterfront facility inspections are essential to: assess a structure’s condition, maintain the structure, budget for repairs or upgrades, and meet public safety requirements. We can conduct many types of waterfront facility inspections. In this blog, we’ll explore underwater inspections, their different types, and which one might be right for your marine structure. We’ll also look at how to choose the right kind of diver for your inspection.
Pier, wharf, bulkhead, and float structures foundations typically extend below the waterline, out of sight. So, it’s critical to look both above and below the water to conduct an effective inspection.
Waterfront facility inspections could occur for many reasons.
- Baseline Inspections: To gain baseline information on a structure’s condition which will be the basis for all future inspections going forward.
- Routine Inspections: Conducted on a periodic interval to review a structure’s condition. The American Society of Civil Engineers (ASCE) recommends that the maximum intervals for routine inspections occur between ½ years and 6 years. The duration varies based on the structure’s age, condition, and environment.
- Design Level Inspections: Focused on specific repair items and collecting enough information to develop design documents.
- QA/QC inspections: Often occurring throughout construction to ensure repairs are completed in accordance with the design intent.
- Post Event Inspections: Conducted to assess a structure for damage, operations, and safety following an isolated event such as a significant storm or vessel impact.
- Due-Diligence Inspections: To provide information on a structure’s current condition, often during a transaction.
In 2015, the ASCE published a manual of practice on Waterfront Facility Inspection (MOP 130). This manual provides greater description on the different types of inspections and divides investigations into three levels:
- Level 1
- Level 2
- Level 3
Level 1 Inspections
Also known as swim-by inspections, a diver conducts a Level 1 inspection visually, or, if visibility is low, the diver uses his or her hands to conduct a tactile inspection. The goal is to inspect 100% on the elements below water to identify gross outwardly apparent defects.
Level 2 Inspections
For a Level 2 inspection, divers go beyond a visual inspection to remove marine growth from a structure. This enables the diver to conduct a more in-depth investigation at isolated locations, typically mudline, mid-water, and directly below low water within areas which often exhibit greater levels of deterioration. The diver will typically complete this type of inspection on 10% of the elements. Depending on the level of marine growth, this can be a significant effort and take substantial time at each inspection location. Time is critical when working underwater, so it’s important to select the right tools to remove marine growth, such as algae, barnacles, mussels, and oysters. Divers frequently use bricklayer hammers, crow bars, or even axes or air hammers for this work.
Level 3 Inspections
Level 3 inspections involve nondestructive testing, or minimally invasive testing, to further evaluate areas of potential distress. For this level of inspection, your diver will often use steel ultrasonic thickness measurement devices and timber coring to assess the element. Your diver will typically complete this type of inspection on approximately 5% of the elements, again, at the same levels as defined in Level 2. These limited, but more in-depth, inspections provide a statistical view of the structure for general assessments but may not collect every defect. So, which underwater inspection is right for your marine project? Consult with your engineer to determine which is necessary to meet your specific needs.
Now, how do you pick the right diver for the job? First, while submersible Remotely Operated Vehicles (ROV) technology has developed in recent years, these un-manned vehicles are no replacement for the ability of a diver to complete physical documentation up close.
Some clients ask us about using commercial divers for underwater inspections. But we always recommend using engineer-divers for your marine inspection projects. Engineer-divers are the right people to make this venture into the depths. We bring a unique understanding of a structures load paths as well as the ability to dive, many times in challenging conditions with low visibility, high currents, limited access, or other challenges. It’s true that any diver can place eyes or hands on the structures, but a commercial diver then needs to provide their data to an engineer for review. Your engineer may find that the diver missed important information or failed to collect all the pertinent data. But engineer-divers provide an inherent benefit when assessing structures: we understand the load paths of a structure and can focus on the critical areas. Frequently, the engineer-diver is also involved with the assessment report and/or the design of repairs. This brings another layer of efficiency to the report as well as efficient designs associated with your project.
Here’s a real-world example of when our engineer-divers helped a client move fast on urgent repairs. Recently, our engineer-divers were inspecting a pier structure as part of a routine waterfront facility inspection. With their level of expertise, they noted that the pier had significant deterioration. They moved quickly. The inspection team notified the owner and quickly completed additional inspections. For public safety, it was necessary to restrict the use of the pier until repairs were completed. Without engineer-divers, there could have been significant delays before an engineer could review the data gathered by a commercial diver and realize there was a safety concern.
As an engineer-diver myself, I recall more than one time when a quick, cursory look at a structure, by boat, of the above-water elements of a pier below the deck did not show signs of significant deterioration. But once our underwater inspection began, things changed quickly. We observed piles with significant section loss – some were even fully severed. These conditions were not outwardly visible from above water, but they posed significant safety risks. These experiences, along with recent waterfront structure failures throughout the country, help drive home that underwater inspections are a critical link in a waterfront facility inspection – and having a qualified engineer-diver helps ensure public safety.
To learn how my team and I can help on your next underwater inspection, contact me.
Fun Facts About Dan
I was trained as a commercial diver in Minnesota.
I’ve inspected and performed underwater inspections on well over 1,000 structures in 35 states and territories as well as 6 countries
Most memorable dives
While diving in the middle of the Pacific – on one of the most remote islands in the world – I was inspecting an offshore mooring system. The seafloor was 150 feet deep, and you could see the bottom from the boat before you even got in the water. We were working on the edge of a land shelf which extended more than 3,000 feet straight down. You could not see the bottom then. Massive rays would swim by. It was incredible.
While inspecting a facility in Oklahoma on the Arkansas River, the water was so murky that we needed to do tactile inspection (feeling) for defects. It turns out the fish couldn’t see either and – bump! – a seemingly large fish swam right into me. My topside support team observed a three-foot alligator Gar jump out of the water at the same time. Turns out, we were both spooked!