Grease Blockage and SSO Reporting
You are the lead operator on call for a mid-sized collection system. At 06:30 on a Saturday, you receive a call from a resident reporting sewage bubbling out of a manhole in a residential cul-de-sac. Upon arrival, you find a manhole overflowing at an estimated rate of 15 gallons per minute. The overflow is flowing into a storm drain that discharges to a small creek about 200 feet away. The manhole is in a line that serves several restaurants. You have a vacuum truck and a crew of two. The weather is dry. The spill has been ongoing for at least 30 minutes before your arrival. Your jurisdiction has a mandatory reporting requirement for any discharge that reaches surface waters.
1. What are your immediate priorities and actions upon arrival?
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- Safety first: Set up traffic control and barricades; ensure crew wears PPE. Test for hazardous gases if entering the manhole (though not needed for surface containment). 2. Stop the flow: Use the vacuum truck to contain and recover as much spill as possible; deploy booms or dams to prevent further spread to the storm drain. If possible, block the storm drain inlet with a temporary barrier (e.g., sandbags, inflatable plug) to contain the spill. 3. Notify: Immediately notify the regulatory agency (e.g., state environmental agency) as required by permit, and notify downstream water users if applicable. Also notify the public via signage if there is a risk. 4. Document: Record the time, estimated volume, and actions taken. Take photos. 5. Clean up and disinfect: After containment, clean the area and apply disinfectant. 6. Investigate cause: Once contained, CCTV or jet the line to confirm grease blockage and schedule cleaning. 7. Follow-up reporting: Complete required reports within the specified timeframe.
2. How would you estimate the volume of the spill, and what factors affect the accuracy?
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Volume can be estimated by: (a) measuring the flow rate (e.g., using a bucket and stopwatch, or estimating from the manhole depth and pipe size) and multiplying by duration; (b) using the vacuum truck's tank level change if all flow was captured; (c) estimating the area covered and depth. Factors affecting accuracy: unknown start time, variability in flow rate, infiltration/inflow, and whether the spill was contained. For reporting, use a conservative estimate and note the method. The estimated volume here: 15 gpm × 30 min = 450 gallons minimum, but likely more if it started earlier. Document assumptions.