Draining Water in Sidewalk

[knae0015]

I am working on a residential development project on a flat site. One portion of the project has a sidewalk running through the backyards of single family homes. Does anybody know any reason why I cannot drain the backyards towards the sidewalk and then have the sidewalk drain towards a proposed infiltration basin? The owner wants this area to remain relatively flat without the need for a bunch of low points and inlet structures.

Thanks.

 

[dicksewerrat]

As long as your insurance is paid up for the slip and falls. I always want the sidewalk to be above the flow lines. What about a drain under the sidewalk? some type of French drain till you get close to the pond area. You should talk to the inspecting authority about how they want the water to be handled.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[oldestguy]

I'd use a trench drain with grate along side the sidewalk. They come in a variety of widths.

 

[bridgebuster]

How about using pervious concrete for the sidewalk?

 

[civilman72]

I would think your cheapest option would be curb and gutter with attached sidewalk.

 

[cvg]

using the sidewalk as a drainage channel is not a good idea. If your site is relatively flat as you indicate, it still will not drain properly. the long term maintenance and liability of a wet sidewalk that will accumulate sediment, ice and likely settle and crack due to the constant inundation with water will be higher than just doing a proper job of grading to drain.

 

[Ron]

Not a good idea! Your job as a civil engineer is to make a bad site drain well. Don't drain to sidewalk. Oldestguy's suggestion of a trench drain is good. Expensive, but good! Remember...when you design something, think about your liability for more than just the design! This is one of those.

 

[gbam]

As Oldestguy points out, a trench drain alogn the upstream side of the sidewalk could capture your sheetflow from the backyard. There are number of manufacturers that allow the drain to be sloped seperate from the finished grade. This option is not cheap, however. A swale along the upstream soide of the SW could do the same as the trench drain but it would take up more space.

 

[brandonbw]

Is the sidewalk in the public right of way? Infiltrate and overflow through the curb face. No inlet structures means sheet flowing and lifting the site to drain to that one point.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

 

[Twinkie]

porous concrete

 

[oldestguy]

For a trench drain,perhaps a local pre-cast outfit has the channels pre-made or could make it cheaper than on-site forming.

 

[civilman72]

Curb and gutter can be installed almost flat (0.3%-0.5%) and is significantly less expensive than a trench drain.

What am I missing?

 

[oldestguy]

civil man. As I read this it is a near flat area, no place for (road for) the gutter at some "lower" elevation than the curb. If there were, he could maybe call for a swale in the lawns off to the side of the walk. Or were you thinking the curb (projecting up above the surrounding flat area) would be a form of diversion to keep water from the sidewalk? In that case you need no gutter.

For the trench drain design, I suppose intermittent inlets to a storm sewer might work, again assuming some place off site is lower for that storm sewer discharge.

 

[civilman72]

OG - Thanks for the reply.

"then have the sidewalk drain towards a proposed infiltration basin"

This statement makes me think the profile of the sidewalk would have no low points, but maybe a "flat" grade (i.e. 0.3%-0.5%). In this scenario, curb and gutter attached to he sidewalk would protect the sidewalk from the surface runoff and still move the water towards the infiltration basin. It may be even simpler to use a detached concrete pan (obviously lower than the sidewalk).

I'm also assuming that a grass swale is not an option due the need for a steeper profile grade (in my parts 2% is the minimum preferred grade).

 

[oldestguy]

Civil man:

Interesting situation. Reminds me of my step daughter's place. A condo where they jammed the buildings close together, maybe 30 feet between front entry walls and with a sidewalk down the middle. All grades go to that walk and it forms the drainage way. Total length of the walkway about 60 yards. Enough room for a fire truck, but no turning around. I'd guess no more than 1% lengthwise and maybe 2% to the walk from building.