# What is this road construction thing? **URL:** \ **Category:** Factual Questions\ **Created:** [March 12, 2012, 8:20pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584 "2012-03-12T20:20:12Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Dingbang](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Dingbang](https://boards.straightdope.com/u/Dingbang)\ **Post date:** [March 12, 2012, 8:20pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/1 "2012-03-12T20:20:12Z")
Sorry I don’t have a picture, but there’s been a lot of construction on a road nearby and I can’t figure out what I’m looking at. It’s not road construction per se. Rather, they’ve torn up both sides of the road, installed some new drainage pipes, and later they will add a bike/pedestrian pathway on one side. The thing in question looks like an inverted drain, about three feet in diameter, 18 inches tall, looking like a dome above ground. It’s slotted like a drain of some sort, but the dome part rises above ground, not down. Plus, it is covered with a neon high-viz green covering that may or may not be temporary. These have been installed in surprising numbers alongside the roadway, but with no set pattern or spacing. There will be one by itself, then three clustered close together. This location is a high elevation, relative to the surrounding area, almost on ridge. If it’s a drain, why is it above ground like that? And is the high-viz green just a temporary covering or is it going to be god-awful ugly like that? ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [March 12, 2012, 8:24pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/2 "2012-03-12T20:24:31Z")
Can you tell what it’s made of? ---
**Author:** ![Dingbang](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Dingbang](https://boards.straightdope.com/u/Dingbang)\ **Post date:** [March 12, 2012, 8:26pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/3 "2012-03-12T20:26:17Z")
I can’t really tell what it’s made of because I haven’t stopped to take a close look and poke at it. I’m assuming it’s metal, but maybe not. Could be rubber/plastic. I theorized that it’s a flexible drain that is installed like that, then pushed down to below ground level, but that’s just a guess. ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [March 12, 2012, 8:29pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/4 "2012-03-12T20:29:23Z")
Is it something like [this](http://www.conteches.com/Products/Stormwater-Management/Detention-and-Infiltration/ChamberMaxx.aspx)? Those are generally installed on an excavated surface and then backfilled, but they sound at least a little like what you’re describing. ---
**Author:** ![Dingbang](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Dingbang](https://boards.straightdope.com/u/Dingbang)\ **Post date:** [March 12, 2012, 8:34pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/5 "2012-03-12T20:34:47Z")
> [@Enginerd](#): > > Is it something like [this](http://www.conteches.com/Products/Stormwater-Management/Detention-and-Infiltration/ChamberMaxx.aspx)? Those are generally installed on an excavated surface and then backfilled, but they sound at least a little like what you’re describing. Thanks, but nope. These are singular round items. Imagine a bowl turned upside down, with slots cut into it, then covered with the high-viz fabric. (The bowl has more of a flat top, not round.) I gotta get a pic. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 12, 2012, 8:40pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/6 "2012-03-12T20:40:14Z")
in construction sites they want to keep debris and dirt out of drainage systems; they have to close these systems from being drained into ( at least unfiltered). they might be providing necessary venting into the drainage system (which drains would later provide) without allowing drainage for now. ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [March 12, 2012, 8:41pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/7 "2012-03-12T20:41:01Z")
I’m betting it’s [this](http://www.siltsaver.com/products.php?productid=1&PHPSESSID=50va5bih2riq94m8lpbbdgtkj4), then. That’s an inlet filter. As long as the site is active, the filter allows water to pass through it while preventing eroded sediments from leaving the site. Basically, it prevents the storm drain from filing with sediment while the rest of the work is completed. It’ll be removed once the site is finished and vegetation established. ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [March 12, 2012, 8:47pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/8 "2012-03-12T20:47:30Z")
could it be a “Beehive grate covering” like [this one](http://www.nfco.com/municipal/products/drainage-grates/beehive/)? (scroll down to bottom of the page, and click on model R4353) It’s a cover for the inlet to a drainage pipe. The convex beehive shape is to prevent leaves or mud from accumulating and clogging up the cover. (edit: oops—I’m 6 minutes too late!) ---
**Author:** ![Dingbang](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Dingbang](https://boards.straightdope.com/u/Dingbang)\ **Post date:** [March 12, 2012, 9:22pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/9 "2012-03-12T21:22:10Z")
> [@Enginerd](#): > > I’m betting it’s [this](http://www.siltsaver.com/products.php?productid=1&PHPSESSID=50va5bih2riq94m8lpbbdgtkj4), then. > > That’s an inlet filter. As long as the site is active, the filter allows water to pass through it while preventing eroded sediments from leaving the site. Basically, it prevents the storm drain from filing with sediment while the rest of the work is completed. It’ll be removed once the site is finished and vegetation established. That’s it! Thanks for the explanation. That makes sense in terms of what’s going on with the site and the stage of the construction. ---
**Author:** ![Al\_Bundy](https://avatars.discourse-cdn.com/v4/letter/a/e79b87/32.png) [@Al\_Bundy](https://boards.straightdope.com/u/Al_Bundy)\ **Post date:** [March 12, 2012, 9:45pm UTC](https://boards.straightdope.com/t/what-is-this-road-construction-thing/615584/10 "2012-03-12T21:45:24Z")
Sure sounds like those are air vents to allow the drains to work properly. Just like the vent on you roof allows the toilets to flush, these need to be on high ground.