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February 2, 2014 / Brandon

Santa Clarita Grading Plan Concept Almost Like Precise Engineering – B+W Engineering and Design Blog

Santa Clarita Grading Plan Concept Almost Like Precise Engineering #CivilEngineer

So after a few meetings with the architect, Kazanchyan Designs, going over some different designs that we came up with, we decided to go a certain direction with the grading plans in Santa Clarita.

Nothing too special going on with this Civil Engineering project. The major constraints are that the low point in the street is smack dab in the middle of the property line. Normally we get a little more slope to work with as the street has a highpoint going to a lowpoint fronting the property. Okay so we came up with a few designs to see just how far we could save money. Infiltration, infiltration, and more infiltration. That’s what all the cities are going for on the Civil Engineer side of things. And we seem to be running into more lots that require stormwater pumps. Both, infiltration and pumps, are expensive and have more maintenance involved. So could we get the site to work with something else?

And after a few rough tries we were able to get a vegetated swale, or bio-swale, to work. This is good. We can sheetflow almost the entire site into a vegetated swale and overflow into a catch basin out through the curbface. That also means no pumps. We meet the stringent SUSMP requirements and get away from something mechanical to drain the project site. So what are we going to encounter doing this? Ah-ha, some more constraints to make this a little more fun. So now we are also trying to stay under disturbing 1+ acres of land to get out of doing a SWPPP. We can’t grade out a complete slope to the undeveloped land because that would make us hit the magic 1+ acres as the site is about 42,000 sqft. We can wrap the property line with a retaining wall. Now we also want to keep this retaining wall to a max of 6′ for cost purposes. So the new constraint is getting enough slope to sheet flow the whole property to the front. While building up the lot just high enough to stay under the 6′ max. All the while we add another constraint.

This one we already knew about but I wanted to just have the extra constraint in mind while designing the grading plans. A future street may or may run against the back property line. Not only are we tying into an under construction grading plan using their driveway to match into. But we also need to make sure our side works with a future street. The tricky part to this is making sure we can get a little portion of the backlot to slope back down to match into what is being constructed. If we were designing both sites as one this would be much easier to control. But we aren’t. The idea now is to raise the site up as little as possible yet just enough to sheet flow. We should have known when a site looks hard to design without going into detail, the site will become a monster to work out as we get more into the grading concept.

Eventually I was able to work out what should be the most minimum grading possible while still keeping everything flowing to the vegetated swale. There is also a future widening on the frontage of the property which is why we are placing the swale so deep into the property. Not the best place to put the vegetated swale, but the location still works. And the best part is that if the site floods, everything is directed to the front of the property and will spill over onto the street. The current concept doesn’t have this designed out yet, but the idea is even if the site floods and a catch basin plugs up, another catch basin should handle the water. A little overkill, but this idea is about the same cost as just letting the site overflow.

With the current design we were able to minimize disturbed grading areas (no SWPPP!), not use a mechanical pump, and not use underground infiltration boxes. This also should allow the buildings to use gravity flow for the sewer lines, so no sewage pump. The tradeoff is that we have to fill the site with more dirt than I would normally want to. And we will have to use some retaining walls. With a rough estimate the costs are much less than the alternatives. And there is nothing to fail which is always a plus from the Civil Engineering perspective. Next post I will show the model I built, since planning needs a working engineering design to approve before we can get into final engineering. And I love showing proposed contours based on a TIN I build.

The post Santa Clarita Grading Plan Concept Almost Like Precise Engineering appeared first on B+W Engineering and Design Blog.
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