9.3 Sewer Cleaning, CCTV Inspection & SSO Response
Key Takeaways
High-velocity jetting is normally set up at the downstream manhole with the nozzle working upstream, so loosened debris is pulled back to the downstream manhole and removed by vacuum.
Bucket machines drag a bucket between two manholes to remove heavy debris such as sand, gravel and rocks, while power rodders with root saws cut roots.
ADEM requires a report within 24 hours of becoming aware of an unpermitted discharge such as an SSO, followed by a written report within five days, submitted electronically.
A notifiable SSO is one that reaches surface water or may imminently and substantially endanger human health, and it must be reported as soon as possible to ADEM, the public, the county health department and affected public water systems.
SSO volume is commonly estimated as the observed overflow rate multiplied by the overflow duration.
9.3 Sewer Cleaning, CCTV Inspection & SSO Response
The WPI Wastewater Collection Class I outline (used for the Alabama Wastewater 1C exam) devotes 27 questions to equipment operation, evaluation and maintenance and 27 to collection system operation, maintenance and restoration. Its task lists include hydraulic cleaning (balling, flushing, poly pigs), jet rodding, blockage removal, rodding, CCTV inspection, dye and smoke testing, and identifying and responding to sanitary sewer overflows (SSOs), collapsed pipes and pump failures.
Preventive Maintenance Programs
A good program cleans every sewer on a planned cycle and cleans hot spots (grease, roots, flat grades, sags) far more often. Records of every cleaning, the debris found and the time spent show where problems recur and justify rehabilitation. Programs often follow the CMOM approach (capacity, management, operation and maintenance) that EPA promotes for reducing SSOs.
Hydraulic Cleaning
High-velocity jetting uses a high-pressure pump to drive a hose and nozzle through the sewer.
- Nozzles: penetrating nozzles with forward jets open blockages; cleaning nozzles with rear jets angled back (commonly about 15 to 45 degrees) propel the hose and scour the pipe; rotating nozzles scrub grease; water-driven root cutters cut roots.
- Standard setup: park at the downstream manhole, feed the nozzle upstream against the flow, then retrieve the hose slowly while the rear jets pull debris back to the downstream manhole, where a vacuum (combination) truck removes it. Debris must not be pushed downstream into lift stations or the treatment plant.
- Use a hose guide or roller at the manhole to protect the hose and the manhole.
- Near service laterals, jet with care; pressure and air pushed into laterals can blow out toilet water inside homes. Reduce pressure near laterals and coordinate with customers in problem areas.
- Track the jetter's water supply: a 1,000-gallon tank feeding a nozzle at 80 gpm lasts about minutes of jetting.
Balling uses an inflated rubber ball sized slightly smaller than the pipe; water backs up behind the ball and the high velocity around it scours the pipe. Kites, bags and poly pigs work the same way. Flushing releases a large volume of water to move light deposits.
Mechanical Cleaning
- Power rodders push continuous or sectional rods with tools such as augers, corkscrews and root saws for roots and hard blockages.
- Bucket machines use two winches at two manholes to drag a bucket back and forth, filling it with heavy debris such as sand, gravel and rocks that jetting cannot lift.
- Hand rods handle small lines and short blockages.
Roots and Grease
- Roots enter through joints and cracks. Cut them mechanically, then consider chemical root control (foaming herbicide products applied under the label and state pesticide rules) to slow regrowth. Long-term control means sealing or lining the pipe.
- Fats, oils and grease (FOG) cause many SSOs. A FOG control program inspects grease interceptors and traps at restaurants, enforces the sewer use ordinance and educates residents not to pour grease down drains.
Inspection
- CCTV: a crawler camera records the pipe after cleaning; defects are coded with the NASSCO PACP system (Section 9.2). Manhole inspections commonly use the companion MACP system.
- Smoke testing and dye testing find inflow sources and cross-connections (Section 9.2).
- Flow monitoring finds capacity limits and infiltration.
- Safety: cleaning and inspection crews work from the surface; any manhole entry is a permit-required confined space with atmospheric testing (Section 12.2), and street work requires traffic control (Section 12.3).
Responding to a Sanitary Sewer Overflow
1. Stop and contain. Clear the blockage, start bypass pumping or restore the failed pump. Block storm inlets and berm the flow to keep sewage out of streams and ditches.
2. Protect the public. Post warning signs and barricades, keep people and pets away, and notify property owners affected by basement backups.
3. Clean up. Remove solids and debris, pump back what can be recovered to the sewer, wash down surfaces toward the sewer (not storm drains) and apply disinfection or lime where appropriate. Photograph the site.
4. Report under ADEM's NPDES rule (ADEM Admin. Code r. 335-6-6-.12).
| Requirement | What ADEM requires |
|---|---|
| 24-hour report | Report to ADEM within 24 hours of becoming aware of noncompliance that may endanger health or the environment, including any unpermitted discharge to a water of the state |
| 5-day report | Written report no later than 5 days after becoming aware, submitted electronically for SSOs, CSOs and bypasses |
| Report contents | Description and cause, exact dates and times, steps taken to stop and prevent recurrence, type of event, type of overflow structure (for example, a manhole), volume discharged untreated, human health and environmental impacts, and whether the event was related to wet weather |
| Notifiable SSO | An overflow that reaches a surface water of the state or may imminently and substantially endanger human health (for example, near water supply wells or where people may contact it). The permittee must notify ADEM, the public, the county health department and other affected entities such as public water systems as soon as possible. |
| Anticipated bypass at a plant | Prior notice to ADEM, if possible at least 10 days before |
5. Estimate the volume. The most common field method is:
An overflow estimated at 30 gpm that ran for 3.5 hours (210 minutes) discharged about gallons. Record how the rate was estimated (measured with a bucket and stopwatch, read from upstream flow meter data, or judged from reference photos) and how the start time was determined.
6. Prevent recurrence. Add the location to the hot-spot cleaning list, televise the line, enforce FOG rules or schedule rehabilitation.
When cleaning a sewer with a high-velocity jetter, where is the jetting truck normally set up?
At the downstream manhole, feeding the nozzle upstream so debris is pulled back to the downstream manhole for removal
At the upstream manhole, pushing debris downstream to the lift station
At any service cleanout, jetting toward the main
At the lift station wet well, jetting upstream from the pumps
A sewer segment is partially filled with sand, gravel and rocks that the jetter cannot lift. Which equipment is designed for this?
An inflatable test plug
A bucket machine dragging a bucket between two manholes
A smoke blower
A chemical root foaming unit
An SSO from a manhole flows into a creek. Under ADEM Admin. Code r. 335-6-6-.12, which notification is required as soon as possible because the overflow reached a surface water?
Only a line entry on the next monthly DMR
Notice to EPA headquarters within one week
Notice to the county commission within 30 days
Notice to ADEM, the public, the county health department and other affected entities such as public water systems
An operator estimates that a blocked sewer overflowed at about 45 gpm from 6:10 a.m. until 8:40 a.m. About how many gallons were discharged?
9,000 gallons
2,700 gallons
6,750 gallons
4,500 gallons
Sections you finish are checked off in the contents.