Navigating the Underground: How Subsurface Utility Engineering Quality Levels Guide Smart Decision-Making
Bottom Line Up Front: Selecting the right subsurface utility engineering (SUE) quality level can save your project significant time, money, and risk. Studies consistently show returns of $4.62 to $22.21 for every dollar invested in SUE services, making it a project manager’s most cost-effective risk management tool.
When breaking ground on any construction project, there’s an invisible network beneath your feet that could make or break your timeline, budget, and safety record. If underground utility maps exist, they are often inaccurate. A vast majority of utility records are derived from construction plans, which are often changed but not accurately documented. Sometimes lines are moved during repairs, but maps aren’t updated. Old maps get lost or damaged and are rarely georeferenced. The high cost of project delays caused by encountering unexpected utilities has led to the development of subsurface utility engineering (SUE) – a systematic approach to managing utility-related risks through standardized quality levels.
At RETTEW, we’ve seen firsthand how proper SUE implementation transforms projects from potential disasters into well-orchestrated successes. But the key lies in understanding which quality level is right for your specific project needs.
Understanding the Four Quality Levels: A Risk Management Framework
The American Society of Civil Engineers Standard Guideline for Investigating and Documenting Existing Utilities, ASCE 38-22, defines four distinct quality levels for subsurface utility data, each representing different degrees of risk and information reliability. Think of these levels as a diagnostic process, with each step providing more accurate information but also requiring additional investment.
Quality Level D: Records Research – The Foundation
Quality Level D represents the most basic level of utility data, derived entirely from existing records or verbal recollections – both typically unreliable sources. This level involves gathering historical records, architectural drawings, as-built plans, and utility company records.
Best for: Early project planning, route selection, and preliminary feasibility studies where you need a general understanding of utility congestion.
Limitations: Records may be incomplete, outdated, or inaccurate. Memory fades, and changes often go undocumented.
Project example: Carlisle Pike SUE Investigation
Quality Level C: Surface Feature Correlation – Adding Context
Quality Level C involves surveying visible above-ground utility features, such as manholes, valve boxes, and hydrants, and then correlating this information with Quality Level D data using professional judgment. This level provides a more complete picture by connecting surface features to underground infrastructure.
Best for: Projects with high accuracy records and lots of visible ground features.
Quality Level B: Geophysical Designation – The Workhorse
Quality Level B involves applying appropriate surface geophysical methods to determine the existence and horizontal position of subsurface utilities within a project’s limits. This is the most widely used quality level for subsurface utility engineering.
Best for: Most design and construction projects, especially in urban areas where utility conflicts are likely. This level provides the sweet spot between cost and accuracy for most applications.
Project example: Central Allentown Substation Expansion
Methods: Electromagnetic locating devices, ground penetrating radar (GPR), and other non-destructive surface methods are commonly used. Utilities are designated using pink paint to avoid conflicts with utility owner paint markings. SUE data is then surveyed to project control.
Quality Level A: Precise Location – The Gold Standard
Quality Level A provides the highest level of accuracy by non-destructively exposing underground utilities, revealing the type, size, condition, material, and other characteristics.
Best for: Congested urban areas, critical utility crossings, precise depth requirements, and situations where inches matter for project success.
Project example: Uniontown Gas Line Investigation
Methods: Typically achieved through vacuum excavation (hydro-excavation) or pneumatic excavation, providing precise horizontal and vertical location data.
The Business Case: Proven Return on Investment
The financial benefits of SUE are backed by decades of research. The landmark 1999 Purdue University study, commissioned by the Federal Highway Administration, found SUE provided $4.62 in savings for every $1 invested. Subsequent studies have shown even higher returns:
- University of Toronto/Ontario Sewer and Watermain Contractors Association (2005): $3.41 average return for every $1 invested
- Pennsylvania State University (2007): $22.21 saved for every $1 spent on SUE
- Pennsylvania Department of Transportation (2012): $11.39 return for every $1 invested
- Louisiana Department of Transportation and Development (2021): $2.73 saved for every $1 spent on SUE
These savings come from multiple sources:
- Reduced utility relocation costs by providing accurate information early in design
- Reduced construction and design costs through efficient planning
- Elimination of construction delays and redesign costs
- Reduced contractor claims and safety incidents.
Beyond Cost Savings: The Broader Benefits
While the financial case is compelling, SUE provides additional benefits that are harder to quantify but equally important:
Enhanced Safety: When excavation work can be shifted away from existing utilities, there’s less possibility of damage that might result in personal injury, property damage, and environmental releases.
Improved Project Delivery: Delays caused by redesign when construction cannot follow the original design due to utility conflicts are reduced.
Better Stakeholder Relationships: Accurate utility information builds trust with utility owners, contractors, and the public by demonstrating professional due diligence.
How RETTEW Guides Quality Level Selection
At RETTEW, we understand choosing the right SUE quality level isn’t a one-size-fits-all decision. Our experienced team evaluates multiple factors to select the best approach for each project.
Project Characteristics: We carefully assess the type and scale of construction, expected utility complexity, available rights-of-way, and project timeline and budget constraints. These fundamental project elements help establish the baseline requirements for the depth and accuracy of the utility investigation.
Risk Assessment: Our team thoroughly evaluates the consequences of potential utility conflicts, safety implications, environmental considerations, and regulatory requirements. Understanding these risk factors allows us to recommend quality levels that appropriately address the potential impacts of utility encounters during construction.
Technical Considerations: We analyze soil conditions and their impact on utility detectability, examine utility materials and construction methods that may influence investigation approaches, review the reliability of existing records, and assess site accessibility challenges. These technical factors directly influence which SUE methods will be most effective and reliable for your project’s specific conditions.
Our approach begins with a thorough analysis of your project’s unique requirements, then develops a tailored SUE scope that balances risk mitigation with budget realities. Our comprehensive approach ensures we’re not just finding utilities – we’re providing the quality level of information that matches your project’s specific needs and risk tolerance.
Making the Right Choice for Your Project
The question isn’t whether to use SUE services – studies have consistently shown that SUE provides cost savings across diverse project types. The question is which quality level will provide the optimal balance of risk mitigation and investment for your specific situation?
Partner with the Experts
RETTEW’s utility mapping experience ranges from corner gas stations to industrial plants, military installations, university campuses, and entire towns, involving every type and construction of pipe and cable. Our team doesn’t just provide data – we offer the expertise to guide you toward the right quality level for your project’s success.
Before your next project breaks ground, consider what’s underground.
Ready to discuss your project’s SUE needs? Contact our utility engineering experts to develop a customized approach that matches your project’s risk profile and budget requirements. Let us help you navigate the underground with confidence.
RETTEW provides comprehensive subsurface utility engineering services following ASCE 38-22 standards. Our experienced team combines cutting-edge technology with proven methodologies to deliver reliable utility data at the appropriate quality level for your project’s success.
David Mostoller, PG
David Mostoller is a Geophysics/Subsurface Utility Engineering Team Lead at RETTEW with close to 30 years of experience in multiple facets of environmental consulting. He serves as a senior project manager and client manager for SUE and geophysics projects for utilities, municipalities, natural gas exploration and midstream pipeline operations, and engineering companies. David manages all aspects of SUE Quality Level D through A investigations, private utility locates, boring clearance, and closed-circuit television inspections.
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