Field practice in sewer construction and access structures: identify the correct statements about boning rods, manhole cover shape, and depth-based manhole classification.

Introduction / Context:
Sewer construction relies on simple tools and standardized appurtenances to ensure alignment, levels, and safe access. Understanding boning rods, manhole cover shapes, and depth-based classifications is foundational for site engineers and inspectors.

Given Data / Assumptions:

• Statements concern typical municipal practice.
• Depth thresholds are approximate and widely used for classification.
• Focus is on practicality and safety in operations.

Concept / Approach:

Boning rods sight invert lines during trench excavation. Circular manhole covers cannot fall through their own opening and are easier to roll and handle. Depth classification (shallow, normal, deep) helps decide laddering, ventilation, and construction details. Commonly, depth < 0.9 m is shallow; > 1.5 m is deep.

Step-by-Step Solution:

Verification / Alternative check:

These practices are cited in standard public works manuals and frequently tested in diploma/degree examinations in civil engineering.

Why Other Options Are Wrong:

Each individual statement is correct, so “All the above” is the only comprehensive choice.

Common Pitfalls:

Memorizing exact depths without noting they are guidelines; overlooking the safety rationale for circular covers.

Final Answer:

All the above.