Not clear from the article but the ‘drain’ is in fact very large concrete structure - upwards of 10 ft high and just as wide - not pipes. Almost like a pedestrian underpass. In fact the entire inside is filled with grafetti. Easily accessible and large.
Quite possible they took shelter from the rain not expecting the water to rise upwards of 8ft between the two ponds trapping them. This report Better shows what’s involved.
https://globalnews.ca/news/7251575/man-miss...mond-hill-pond/It’s surprising the quantity of water that eventually engulfed it.
Disco - kudos on your second post.