Wednesday, 1 August 2012

All Plugged Up and Nowhere to Go

This shot was taken on July 10th at the huge storm sewer outfall along the Red Hill expressway near Barton St. In addition to the fowl odor and murky waters which surrounded the area, the obvious build up within the grate showed a cause for concern!

Why are blocked outfall pipes a concern you ask? Let's consider Hamilton's sewer system - which consists of two types of outfalls. 

Combined Sewer Outfalls

Currently, the older portions of the city's sewer system collects both domestic sewage (from sink drains and toilets) and storm water runoff in a single pipe called a combined sewer.  This mixture, called combined sewage, is then sent to the Woodward Avenue Wastewater Treatment Plant (WWTP) for treatment. During dry weather or small rainstorms, all combined sewage receives full treatment before it is discharged to Hamilton Harbour. 

During heavy rainstorms however, the excess water can cause excess combined sewage that the sewer system can’t handle. To address this problem, the city has 6 Combined Sewer Overflow Tanks. These tanks store the excess combined sewage during rainstorms. The tanks are filled by gravity, and when flows subside after a rainstorm, their liquid contents are drained or pumped back into the combined sewer system and conveyed to the Woodward Avenue WWTP where they are treated.

In some cases, the rainfall will be so heavy that the system and the tanks become overloaded as well. When this happens, the excess wastewater will be discharged directly into Hamilton’s natural waterways (at either Hamilton Harbour, Cootes Paradise, Chedoke Creek, or the Red Hill Creek). These discharge points are called Combined Sewer Overflows (CSO).

Storm Sewer Outfalls 

The storm sewers located on our roadways and in front of our properties are meant for storm water runoff only — as the materials that go down these drains filter directly into our natural waterways. These discharge points are referred to as storm outfalls. 

Given their nature, these two types of discharge points should only be flowing if there is excess combined sewage or excess road water. If these outfalls become plugged or backed up (like the grate on this outfall), the water and combined sewage within the overloaded system will need to find another release point. Say, residential basements? 

To address this outfall a picture was sent to Ward Councillors Merulla and Collins. They sent it on to the City Manager and Public Works staff who cleaned out the grate by the next morning. The city said it was unsure as to why their protocol to visit 'priority outfalls' pre- and post- storm events was not followed. 

Unfortunately, upon more recent visits, it appears that the debris on the grate is already beginning to accumulate again. So let's keep an eye out on this one!  

*Information from this post was taken from the City of Hamilton's website. 

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