How can engineers and contractors ensure safe, reliable access to underground infrastructure?
PUYALLUP, WA, UNITED STATES, January 5, 2026 /EINPresswire.com/ — How can engineers and contractors ensure safe, reliable access to underground infrastructure? In an article featured in HelloNation, David Tejel of Shope Concrete in Puyallup, Washington, explains why selecting the correct manhole size and type is critical for sanitary sewer and drainage systems. His guidance emphasizes the importance of safety, compliance, and durability when planning underground infrastructure access.
The first factor in choosing a manhole is diameter. Common sizes include 48, 54, and 60 inches, with larger diameters often needed for municipal or industrial systems. A smaller manhole may fit residential needs but can limit access for crews and equipment in larger projects, while a larger one ensures safer and more efficient inspection and repair work.
Type selection is just as important as size. Many agencies, including the Washington State Department of Transportation (WSDOT), classify manholes as Type 1, Type 2, or Type 3, each suited for specific conditions. Type 1 may be used for lighter loads, while Type 3 is designed for heavy traffic or deep installations requiring greater reinforcement. Adhering to these specifications reduces the risk of rejection during inspection and ensures compliance.
National standards further strengthen quality and consistency in manhole design. ASTM guidelines outline criteria for durability, watertight performance, and structural integrity. Many projects also require NPCA (National Precast Concrete Association) certification, which ensures manufacturers follow strict quality-control processes. These certifications provide municipalities and engineers with confidence that manholes will meet or exceed long-term performance expectations.
Soil and load conditions must also be considered. In areas with sandy or unstable soils, thicker walls or additional reinforcement may be needed to prevent movement. Where heavy vehicle traffic occurs above, the manhole must be engineered to handle distributed loads safely. Engineers also account for groundwater pressure, as infiltration can increase wastewater treatment costs while exfiltration risks contaminating surrounding soil and groundwater.
Watertight performance remains a top priority in modern manhole construction. Properly designed seals, including grade rings, gaskets, and joints, prevent leaks and extend the life of the system. In high groundwater regions, watertight construction is especially critical, as constant pressure can expose any weakness in the structure. A secure seal helps protect both the manhole and the surrounding environment.
Material selection adds another layer of assurance. Precast concrete manholes are the industry standard due to their strength, durability, and ability to comply with both agency and national standards. Manufactured in controlled conditions, they provide uniform wall thickness and consistent reinforcement placement. Precast sections also fit together predictably, reducing field installation errors and ensuring reliable performance.
Maintenance considerations also depend on proper selection. A manhole that is too small or poorly aligned with pipes makes inspection and repair more difficult. Choosing the right size and type from the start supports worker safety and efficiency, reducing the time and cost associated with long-term maintenance.
Durability is another advantage of choosing carefully. Reinforced precast concrete manholes built to ASTM and NPCA standards can last for decades under heavy loads and challenging soil conditions. Though larger or more heavily reinforced structures may require higher initial investment, they often save costs over the system’s lifespan by reducing repairs and replacements.
Project planning benefits when standardized designs and certifications are followed. Contractors can source materials with confidence, knowing they will pass inspection and integrate seamlessly into existing systems. This predictability minimizes delays and supports on-schedule project completion.
As Tejel explains, selecting the right manhole size and type is more than a design decision. It impacts safety, compliance, cost, and long-term reliability. By factoring in diameter, type, soil conditions, load requirements, and adherence to ASTM and NPCA standards, engineers can ensure safe, durable access to sanitary sewer and drainage systems for decades.
These considerations are outlined in the article Choosing the Right Manhole Size & Type. This is according to Precast Concrete Expert David Tejel of Puyallup, Washington, who explains how manhole design decisions affect the strength and sustainability of underground infrastructure for HelloNation.
Pat McCabe
HelloNation
+1 (585) 427-0020
email us here
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