Cork, Ireland is a trench drain paradise.
Cork is settled at a low point just inland of the southern coast of Ireland where the River Lee flows into the Celtic Sea. At 187 feet above sea level, the city center is an island created by a split in the river. You’ll run across trench drain everywhere you go in Cork whether you’re strolling through the downtown shopping district or crossing one of the city’s 29 bridges. The variety is refreshing.
I spotted the trench drain above about 50 feet from my hotel at the top of a steep and winding hill. Houses are stacked up the hillside, almost every one having its own trench drain system installed in the driveway – usually a plastic system. This driveway drain system is definitely not plastic, though. Take a look at the close up photo, shown left.
This is an ACO trench drain system with galvanized slotted grates in one of Europe’s most popular sizes: 118 millimeters, or roughly 4.7 inches. One of the most obvious things about this drain – aside from the fact that it’s clogged – is that the light duty galvanized grate features a lip that covers the channel’s edge. The trench body is a 1 meter, neutral-sloped polymer concrete channel that is supposed to drain up to 190 square meters with some reliability. With all those pine needles, I’m not sure it lives up to its reputation.
There are several similar products that compete with ACO in America. ABT offers a polymer concrete drain with overhanging galvanized steel grates, which is close to Polycast’s 400 Series. All three of these drains are about 4” wide, offer galvanized grating and are not recommended for heavy traffic applications. The ACO drain near my hotel was protected from being driven over by some lovely potted plants; otherwise vehicle traffic would have bowed the grates.
Bridge Trench Drains
I ran into the next trench drain while walking along a paved river trail near downtown Cork. The trail doesn’t see much vehicle traffic, but a fair amount of pedestrian and bicyclists cross it daily.
I’m most excited about this drain because I’ve never seen Stora-Drain, a Belgian drain manufacturer, before. This particular channel drain is a lightweight polymer concrete system designed for pedestrian, bicycle and small vehicle traffic. The channel is again neutral-sloped, relying on the natural tendency of water to find its level. Also again, the drain is clogged and sediment is already turning into tufts of grass at the drain’s lowest point.
The stainless steel perforated grating gives it away as a Class A system. You can see by the shape of the grate that it sits inside the concrete channel on a lip rather than protecting its edge. It looks as if the channel has a rail protector to give the whole drainage system a more polished appearance.
Because downtown Cork is located in a valley, almost every sidewalk and road is lined with stretching runs of trench drains. Almost all of it is MEA Drain, too.
The trench drains are all fairly wide, about 8” wide by American standards. The width alone is a big change from the earlier drains, which were residential or small commercial sizes. These larger MEA drains are geared to handle some serious traffic.
Check out the photo below. The ductile iron grate is bolted into its channel. Bolting down grates stops grates from shifting as traffic goes over them, preventing them from eventually rattling loose and breaking. This is a common enough feature for airports and highways but is not seen so much on cobblestone streets.
The 800 Year Flood
In 2009 a flood swept through Cork causing the worst damage in 800 years. A local cabbie I spoke with attributed the damage to a combination of heavy rains and high tide – a similar weather pattern to what Americans saw during Superstorm Sandy in 2012 – as well as the untimely opening of an upstream dam. Officials opened the dam to prevent further flooding, but the water entered an already swollen river and left downtown beneath 1 meter of water.
I suspect the flood may be partially responsible for the extreme regional sediment build-up within the drains. Another likely culprit is the drains themselves. Most of the trench drain systems I saw had neutral slopes, meaning they were left at grade with the ground. Although the ACO drain, the Stora-Drain and the MEA drain had radius bottoms that are supposed to prevent sediment build-up, heavy rains like the 2009 floods wash away massive amounts of topsoil and leaf litter. Without a sloped channel, water lost velocity too quickly to carry the sediment out of the drain.
At least, that’s my theory.
Have a theory of your own on sediment buildup and clogged trench drains? Let me know by leaving a comment below!
If you have a question about lockdown grates or the difference between galvanized and stainless steel, email us at [email protected] or call one of our drain specialists at 610-638-1221 to discuss your application. For, information on the MEA, ABT and ACO trench drain systems mentioned above, visit our website.