Preventive maintenance planning, asset priority, work orders, and documentation
Key Takeaways
- A preventive maintenance program schedules high-risk sewer segments before failures, using blockage history, FOG sources, roots, flat grades, surcharge complaints, and critical customers to set frequency.
- Work orders should capture location, asset ID, crew, equipment, cleaning method, debris removed, defects observed, photos or CCTV links, and the follow-up decision.
- CMOM means Capacity, Management, Operation, and Maintenance; exam scenarios usually test whether the utility is preventing SSOs instead of reacting after backups.
- A line that repeatedly needs emergency cleaning should be moved into a higher-frequency route, inspected by CCTV, and evaluated for source control or rehabilitation.
- There is no single universal national wastewater collection license; many jurisdictions use WPI-style standardized exams, but certification and reporting rules are set by the certifying authority.
Preventive maintenance as an SSO prevention system
A wastewater collection system maintenance program should be built around risk, not habit. WPI's current collection outline includes high pressure cleaning, inspection, emergency bypass operations, asset management updates, system failure response, data collection, GIS updates, and work activity planning. EPA's CMOM framework points in the same direction: a utility should know its system, maintain it, document it, and use the records to prevent sanitary sewer overflows (SSOs).
Preventive maintenance (PM) means scheduled work done before a failure. In a collection system, PM often includes cleaning known trouble spots, inspecting manholes, checking air release valves, verifying access, trimming vegetation, confirming easements, calibrating meters, and updating maps. It is not the same as emergency response after a basement backup.
How to prioritize assets
The best exam answer usually links probability of failure with consequence of failure.
| Priority factor | What it suggests | Typical action |
|---|---|---|
| Repeated stoppages | Root intrusion, FOG, sag, offset joint, debris source, or poor grade | Increase cleaning frequency and schedule CCTV |
| Wet-weather SSOs | Inflow and infiltration or inadequate capacity | Flow monitoring, smoke testing, dye testing, CCTV, hydraulic review |
| Critical location | Hospital, school, highway, waterway, or dense downtown | Higher inspection priority and stronger emergency plan |
| Poor access | Buried manhole, easement conflict, traffic hazard | Correct access before an emergency occurs |
| Age/material risk | Vitrified clay joints, brick manholes, corroded concrete, failing force main | Condition assessment and capital planning |
| Pump station dependence | No gravity alternate route or single force main | Generator, bypass connection, spare pump, valve exercise |
Work orders that actually help operators
A useful work order does more than prove a crew was busy. It creates the next decision. Record the upstream and downstream manhole IDs, pipe size and material, cleaning direction, nozzle or tool used, water pressure/flow if relevant, volume and type of debris removed, unusual odors, surcharge evidence, customer contact, traffic control, confined-space notes, photos, and whether CCTV or repair is needed.
Good records change routes. If a 12-month cleaning interval still produces grease plugs, move the segment to 3 or 6 months while source control is pursued. If three cleanings remove little debris and CCTV shows a sound pipe, the interval may be safely extended. If the same line is cleaned every month because of roots, the long-term answer is root control, joint repair, lining, or replacement.
Exam traps
Do not choose answers that say to clean only after complaints, ignore wet-weather patterns, or keep cleaning the same line forever without finding the cause. Also avoid answers that imply WPI creates one national license. WPI standardized exams support many programs, but the operator's legal certification, reporting duties, and class level come from the applicable state, province, or certifying authority.
A gravity main near several restaurants has caused two dry-weather backups in six months. Crews jetted the line both times and removed heavy grease. What is the best preventive maintenance response?
Which items belong in a useful sewer cleaning work order? Select all that apply.
Select all that apply
Which statement best matches the CMOM mindset for collection system maintenance?