When establishing sewer alignments for a new drainage district, the recommended setting-out procedure generally starts from which location and proceeds upstream?

Introduction / Context:Accurate layout of sewer lines requires hydraulic continuity and feasible gradients. A practical field procedure is to start where the system must ultimately discharge and then work progressively upstream.

Given Data / Assumptions:

• Gravity sewer system with a defined outfall to a treatment plant or water body.
• Gradients and cover must be maintained while avoiding deep excavations.

Concept / Approach:Starting from the outfall ensures that downstream constraints (invert elevations, receiving works) are honored first. Designers can then establish feasible slopes and depths for upstream reaches, minimizing costly re-grading and conflict with utilities.

Step-by-Step Solution:Fix the outfall invert and grade based on receiving structure requirements.Set upstream invert levels to maintain self-cleansing velocities and cover.Iterate through branches to maintain hydraulic continuity and avoid excessive depths.

Verification / Alternative check:Field practice and surveying workflows commonly begin from benchmarks at the outfall, ensuring cumulative fall is adequate and conflicts at the discharge are avoided.

Why Other Options Are Wrong:

• Starting at the city center or tail ends risks mis-matching levels at the outfall.
• “Any convenient point” ignores critical boundary conditions.
• Highest ground is not necessarily hydraulically controlling.

Common Pitfalls:Neglecting downstream constraints first; this can force expensive redesigns or deep excavation later.

Final Answer:From the outfall (discharge point) upstream toward the tail ends.