Late on a dark night, with blurry eyes and sleepy minds we arrived at the dark corner of an intersection on a quiet street. At a familiar spot ahead was the manhole that would serve as our entrance into a mysterious section of Vancouver's sewer network. Dubbed the "Terminal Drain", this was to be my third foray into its underground depths.
My first visit (read:"a misadventure"), somewhat unprepared and overanxious, I was nearly trapped inside the pipe when I dropped off the last ladder rung- which was then out of easy reach. I barely managed to escape that day, but vowed to return and see the rest of the drain. A recent return trip with some necessary gear to enable easier egress did in fact go very well, but was cut short due to the high tide filling the drain with water that exceeded my waders' capacity. The rising water seemed foreboding so we made a quick exit; but again I swore I'd return to explore more of this drain.
Third time's the charm, and we came prepared with the right equipment and tide predictions. A combination of waiting for low tide and low bystander presence meant that we had to arrive at the drain only a few hours before dawn. Suiting up quickly with waders, gloves and headlamps, I deployed the necessary entry gear and soon set foot into the soft mud at the base of the manhole.
The atmosphere below was moist and warm, but surprisingly seemed less smelly than it had been during our last visit. The clean air lasted only a few moments, however, until the water at my feet took on grey sediment and the smell of a sanitary sewer connection drifted to my nose.
This drain begins in a small CSO overflow chamber that connects to a much larger, older combined sewer (that is just out of reach). The pipe, arched concrete ceiling over a brick floor, is perfect walking height and only mildly slicked with the flow from small sidepipes. The bricks themselves are an off-gray colour, larger than normal, and are possibly made of vitrified clay. This pipe is not very long, and quickly splits into a pair of large, 2.4m square ducts laid side-by-side. These ducts, filled twice daily with tidal waters, were the aim of tonight's exploration. With Nancy Drew at my side I set off down the large duct, the blue beams from our headlamps lighting the way. On the other side of the wall to our left was another duct identical to the one we walked through.
The pipe had very little water in it compared to our previous visit, and the walls on either side shared a near-horizontal line of wet mud that was the high-tide mark. As we walked, the high water mark slowly rose until it was quickly above the level of our waders. The bottom of the pipe was covered by sand and gravel, with pools and channels of water carving through the muck. A slight fishy odour was in the air.
The mud piled higher and higher along the walls just before we reached a junction, where the duct we were in joined its neighbouring twin and both pipes were constricted into an 1800 RCP. After the roomy 2.4m duct pipe, it seemed a chore to walk with head bowed through the RCP, with its slippery floor and deeper water. Luckily, we soon entered an interesting 10m length where the RCP opened into a slightly larger hallway-type section; a square pipe with beveled edges. Back into the RCP after this, we passed meters of featureless pipe and a few manhole shafts. By now, the brown mud of the tide mark on the walls was neck-high; and we knew that it wouldn't get any shallower downstream.
The RCP twisted and jogged, then suddenly expanded into a huge square duct, which I carefully stepped into. Water, mere inches deep, reflected the beam of my headlamp across the wide floor, and the ceiling was about 9ft high. The walls were coated with brown mud, and the tide mark was above my head. Several meters to my front a small pipe crossed through the duct, its surface caked with inches of globby mud. We advanced into the large, dark hallway, mindful of new smells in the air. There was the constant background of wet mud and dirty water, mixed with an infrequent whiff of something less pleasant. As we walked on, and on, our feet stirred sediment which released foul gases. The air constantly reeked of one unpleasant odour or another, swamp gas or rotten eggs and somehow even cigarette smoke.
The pipe seemed nearly featureless; the brown walls marked only by the odd small sidepipe or catchbasin lead. We walked for ten minutes, and the high tide mark rose to the ceiling. The pipe was a straight line that terminated in distant darkness that our lights couldn't reach. Determined, we strode onward; monotonous walking, watching my footsteps, trying to avoid the piles of sediment on the watery floor, and being subjected to an assortement of stench. I thought our effort would soon be rewarded when I detected an odour of salty fish, and assumed we were closing in on the outfall. Small white barnacles began to dot the walls, and I could hear water flowing ahead.
Shortly, the duct terminated at a pair of large, sunken RCPs. I'm glad I took a good look instead of blindly stepping inside these; at least 1.8m in diameter, they were both half full of water. The water was easily waist-deep, and there was no way to continue without using a raft and a carefully consulted tide-chart. Looking down the pipes, they continued into blackness. I was disappointed that we'd come so far and would not be able to see the end, and I knew I would probably never make any further attempts to see the outfall itself (which I presume is usually submerged anyway). Although we were both sweaty and wishing for fresh air, neither Nancy Drew nor myself were eager to retrace our steps up the long, smelly duct; so we lingered at this point that would mark the end of our journey. Upon close examination, we discovered that the muddy walls were home to dozens of small dark-shelled molluscs, and among these were some other tiny, squirming white creatures.
Eventually, we retreated back up the pipe. Passing everything in reverse, we took more time to peer inside the small, mud-clogged sidepipes, but declined to actually enter any of them. My tired eyes watched my footsteps, and I felt very sweaty and warm.
Happy to reach the manhole exit, we wasted no time making our escape. As dawn filled the sky with pale light, we pulled off our waders, packed up our gear, and headed home for a nap.
Follow-up research indicates that the original drain in this area was "in poor repair (with) limited capacity. As a result, the (flats area) is subject to flooding during periods of heavy rainfall coinciding with high tide." Thus, the drain was expanded in 1972 with the addition of 406ft of 9'x11' box conduit, giving the sewer extra capacity.