"A view inside one of the tanks does not say good things about their capacity"
I’ve had a fascination obsession with Cathedral Park since we first started poking around in the storm drains of Hamilton. In 2004, Kowalski climbed the Wall of Anguish and took the photo at right, captioned: “A view inside one of the tanks does not say good things about their capacity.” When I visited the same area in the autumn of 2007, I peeked over the sill (visible at upper right/left) and caught a brief glimpse of the real tanks below. Ever since, I’ve been determined to get back.
Our original plans involved tying a rope to one of the struts in the overflow chamber, and rappelling down into the tank. I’m glad we never tried this— I’m pretty sure the tank under the overflow pipe is pretty reliably half-full of shit, year round.
In November of 2009, Dave (and his merry band of Fellowes) finally found a way into the tanks, and lived to tell about it. Determined to check it out for myself, Sarah and I attempted our own incursion a month later.
History
The Cathedral Park (Main/King) CSO, constructed in 1995, was designed to reduce the pollution from three former uncontrolled CSO outfalls, and provide a catchment facility for the Woodward Avenue waste water treatment plant.
The operation of this tank is really quite simple. Three automatic gates within the sewer system control the flow of combined sewage to the WWTP and into the tank. These gates are typically set to permit up to three times the average dry weather sewage flow to continue to be sent to the Woodward Avenue WWTP.
Flows enter the pump house wet well located beneath the control building. During dry weather and small storm events (e.g. less than 2 to 3 times dry weather flow), the pumping station acts as a normal sewage pumping station. During larger storm events, two large motorized sluice gates are opened to permit flow to enter the storage tank. The tank is separated into two individual storage cells, which are separated by a central dividing wall. The first cell provides approximately 25,000 cubic metres of CSO storage. Most storms will not fill this cell. If the first cell is filled, excess CSOs overflow from Cell 1 to Cell 2 through openings in the top of the dividing wall. Cell 2 provides another 50,000 cubic metres of storage. The storage cells are approximately 8 m deep.
[pullquote]Cathedral Park, after Christ the King Cathedral, would be more fittingly named not for the church across from the park, but for the real cathedral— beneath it.[/pullquote]
Combined sewage retained in the tank is subsequently pumped back into the 78″ sewer for transport to the Woodward Avenue WWTP for treatment during dry weather when the plant can deal with the excess flow. Secondary treatment is provided to the CSOs caught by the tank and the City’s four other CSO storage tanks.
Depending upon the size of the storm, the combined sewage may be retained in the tank for up to 36 hours. During this period, solids in the sewage settle to the bottom of the tank. After the liquid contents of the tank are emptied by the one or two of the submersible pumps (a third pump is provided for backup), the settled solids remain on the floor of the tank. The solids must be removed in an efficient and timely manner to avoid potential odour problems. The floor of the Main/King CSO Tank is cleaned by a series of 30 sediment-flushing tanks (SFTs). These are large stainless steel buckets, which are suspended above and along the back walls of the tank, about 8 m above the floor. The tanks are filled with potable water and when full, they tip and empty their contents down the back walls of the tank. The flush water continues down the sloped floor of the tank at a high velocity and washes the solids into a central trough in the middle of the tank. The flushed material is then pumped into the 78″ sewer and sent to the Woodward Avenue WWTP for treatment.
The Main/King CSO Storage Tank is designed to reduce the frequency of CSOs at three former outfalls from 20 to 30 / year to 2 to 3 / year. CSO volumes are typically reduced by approximately 90% by the tank, and approximately 95% of the wet weather flow entering the combined sewer system is controlled, easily exceeding the requirements of the Ontario Ministry of the Environment’s Procedure F-5-5 for CSO Control (i.e. 90% control to the level of primary treatment).
Infiltration
We entered via the usual route, up and over the Wall of Anguish (a difficult climb this time, as the surfaces were slippery and wet), eventually coming into the control room above the tanks. While the lights weren’t on this time as they had been for Dave, I had an easy enough time finding the switch— and when no alarms went off we proceeded to explore the place.
A brief look down the nearest staircase revealed a twenty-foot-deep pool of toxic sludge, in the primary tank. I was a bit disappointed, thinking that we wouldn’t be able to actually get down into the tanks that night, but after walking around the perimeter of the facility, we found the secondary tank to be nearly empty, aside from some sludge on the floor and the catchment basin in the center.
[pullquote-right]The Main/King CSO capacity is roughly that of 30 Olympic-sized swimming pools[/pullquote-right]
It’s hard to describe the scale of these tanks, with so few points of reference within them. In the first photo below, the staircase ascending from the floor of the secondary tank gives a hint at their size. The total combined storage capacity of these two tanks is listed as 75,000 m3. An Olympic swimming pool holds 660430.1339 U.S gallons— 2,500 m3. Imagine thirty Olympic pools, then, and you begin to get a sense of the size of this space.
After examining the sediment-flushing-tanks thoroughly, and exploring the many walkways and utility corridors crisscrossing the complex, we politely shut off the lights and left via the (as before) unlocked front door.