IntermediateBEHAVIORAL
Walk me through a project where you were responsible for ensuring the quality and accuracy of water/wastewater modeling or design deliverables (reports, plans, or calculations). What specific QC steps did you follow, and how did you handle discrepancies you found?
Water/Wastewater analyst
General

Sample Answer

On a recent wastewater collection system rehab project for a city of about 85,000 people, I was the analyst responsible for QC on the modeling results and the basis-of-design report. We were sizing rehab and upsizing for roughly 40 miles of gravity sewer and 6 pump stations. My first step was a structured checklist: model build review, data sources, calibration benchmarks, and design criteria (peaking factors, I/I assumptions, freeboard). I spot-checked about 15% of pipes and all critical junctions by hand using Excel and Manning’s equation. During review, I noticed one sub-basin’s modeled peak flow was about 30% higher than historical SCADA and flow meter data. Instead of adjusting the model to fit, I traced the data back and found a GIS connectivity error and a double-counted pump station. After fixing it and re-running scenarios, projected surcharge locations dropped by about 20%. I documented all assumptions, checks, and corrections in a QC log that became part of the final report.

Keywords

Mentions scale of system and clear responsibility for QCUses a structured checklist for model and report verificationDescribes specific manual checks and comparison to SCADA/flow dataExplains how a discrepancy was found, corrected, and documented with measurable impact