C+S September 2021 Vol. 7 Issue 9 (web)

The Threat from Below By Matthew Fitzgerald

Every owner, designer, and construction professional has been there at some point in their career - subsurface utility unknowns causing in - juries, schedule delays, budget concerns, design updates, and unhappy customers. Plagued by inaccurate and unreliable utility records and as- builts, the design and construction industry continue to see the negative impacts of underground unknowns. Imagine hitting a gas main next to a school or cutting off the oxygen to a hospital’s intensive care unit. What if a hidden set of trolley tracks suddenly derails your building schedule? Or you dig up a decades-old fuel tank that was long forgotten — until you were unfortunate enough to find it, right in the middle of your jobsite? It happens. In fact, it’s common. Using McCarthy’ Subsurface Utility Mapping (SUM), we find issues every single time we create a map of what’s underground at a construction site. And yet, in our experience, about 90 percent of all construction projects don’t include comprehen - sive subsurface mapping before excavation. In failing to accurately locate subsurface utilities, owners, contrac - tors, and facility operations at risk. The financial impact alone can be substantial as underground unknowns typically lead to an 18 percent change order rate on complex civil site project contracts. Hidden utilities and other threats from below are ticking time bombs waiting to cost time and money as sites are being prepared for building. By using complete, accurate, color-coded and extremely detailed maps and models, subsurface mapping creates a full picture of what may be lurking underground. Where is the Value? According to the Purdue University Department of Building Construc - tion Management – for every $1 spent on mapping at this level of detail, owners can save an average of $4.62 in cost avoidance for their project. Beyond the potential cost savings of finding an issue after a project has begun, having the knowledge of what lies beneath pays in dividends. 1. Safety – Recognize greater safety measures as project teams imple- ment and communicate the investigation results to those directly involved in the construction 2. Budget – Provide cost-certainty earlier during design and preconstruction phases, as mapping results give clearer vision for civil operations 3. Design – Provide greater confidence in civil design aspects such as pro- posed utility routing and profiles, site grading, existing utility shut-offs, utility tie-ins, foundation locations, and building layouts 4. Schedule – Give greater clarity on real durations for civil construction operations due to increased accuracy of overall civil design, allowing owner to plan and communicate more effectively with campus members 5. Operations – Protect the customer experience for a passenger, student, patient, or tenant based on greater confidence and planning of surrounding construction operations

Photo: McCarthy

SUM is most valuable when considering a new project with these attributes: 1. An operating campus 2. An aging campus with decades of compounded infrastructure 3. Dense urban areas with complicated site work 4. When building adjacent to high-risk utilities such as oxygen or gas However, it is being made clear that any project can utilize a SUM customized approach that properly addresses the underground risk present. One project may need detailed sewer reports, while the next needs surface features only. One project may need detailed conduit information and butterfly diagrams, while the next is only concerned with horizontal alignments. One project wants to coordinate their site logistics in three-dimensions, while the next prefers two-dimensional. The question is not whether a project needs SUM, but rather the ap - proach that best meets the needs for the construction team, the client, and the budget.



september 2021

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