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Grading help.

Grading help.

Grading help.

I'm an EIT and so far the most confusing part of the job is the site grading. When I see my boss do the grading, it appears to be the easiest thing in the world but when I'm looking at it, I just can't see it.

Are there any quick references I use for Max/Min slops, preferred, ect when it comes to grading?

Also, once you set your building, do you usually leave a fairly flat area outside of it for a certain distance? If so, how much? I'm new to this forum and will contribute when I can. Thanks for the help!

RE: Grading help.

I think grading a site is based more on experience than anything. A good guide would be to use your local municipality guidelines. Hillside grading becomes a whole other animal. I can grade pretty fast on the fly on paper or straight into the computer. But that took years of me working under someone who was nice and answered all my questions constantly for months/years.

You could generalize and say you try to get a 2% min slope away from the building onto the street. Any stormwater going into an area drain should have a 1% min slope for the pipe system. The pipe and drain size depend on the Q going into the pipe network. A parking spot should have a max 5% slope. Grade slopes on a driveway entrance depend on the city codes. 2% max in all directions on an ADA area. Even if this is all written somewhere a plan checker may say no and make you redesign or you have to prove to them why it can work.

Anyone I try to teach grading to, I will try to make them understand how everything on a site must daylight into something. Whether its a retaining wall, existing ground or something existing. That is the basic idea how to connect the land together.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer
http://bwengr.com | http://bwstructuralengineer.com | http://bwcivilengineer.com

RE: Grading help.

If your boss does this with such ease, it should tell you that he will be your best source of information. He's your mentor. Don't be afraid to use him as such. I'm sure he fully understands that you would not be expected to perform at his level...but he can certainly help you to get there.

RE: Grading help.

Site grading reminds me of undergrad statics - trying to find the "sweet spot" to sum moments about. Suddenly the light bulb just pops on. I always try and first pass everything using nominal elevations and grades rounded to 0.25 or 0.1. I still like using hard elevations on inlets and breakpoints in increments of 0.25, 0.1, 0.05 and letting the slopes give to what they are 1.36%, ... (provided they meet code). The contractor will construct it around the break points, so there is little likelihood that they'll be able to run a nice even slope across the parking lot with the paver anyway.

Pick out all of your limiting constraints, i.e. property line elevations, finish floor, public streets, .. and have at it. Some other constraints will creep in as you are working, i.e. 2% ADA spots nearest the building ... No points off for working this by hand on a 1:20 or 1:10 scaled print and then going to town in 3D modeling or whatever you are using.

Once the site grading is pretty well established, spend time on storm water runoff. Does code require a Q(10), Q(2) & Q(25) or even a higher event? You may need to drop in additional area drains to insure you are capturing the required event. Also review inlet capacity based on a nominal head (or actual as design finalizes) against grades. The last thing you want is your 2cfs inlet only functioning as such with 1' of head which back water up into the building, or into another inlet's subbasin, or onto the neighbor's property, ... From here you'll get into the storm sewer design, detention requirements and so on.

I think you'll find that once the rough grades are established, there are many opportunities for fine tuning. This is where I'd start getting a detailed computer model going, but I'm not up the latest CAD"D" offerings. I doubt they have a magic button (beyond the raise/lower slab) just yet.

RE: Grading help.

That's a really good description of how to work out a site.

We just designed a commercial site that is splitting out a car lot into its own commercial lot with an existing building that will have some additions. Not only that but they will also be adding another driveway to the high side of the lot. The existing drainage pattern changes because of this. Not sure about other states, but here in Los Angeles you are supposed to keep the the same drainage pattern and Q's off site. To handle the additional water coming off the project that wasn't there before, the cities want to infiltrate the ground with a set number to handle the difference. I bring this up because to build our original design it was a little higher in cost. I kept telling the developer that if we change the drainage pattern too much something much more expensive will kick in.

When eea says to spend time on storm water runoff he/she isn't kidding. Its really important to have a good understand of the code in the city you are working in and if you don't know ask. The plan checker may give you an idea of how to get around something expensive. We did this on another job with the way we used infiltration to get around another stormwater requirement, and the developer was really happy that we saved them over $100k in building costs. That one just took some simple math in front of the plan checker to prove what we were doing.

Once you get how the stormwater works in relation to tying the lot together, that light bulb will start going off much faster and you will feel more confident when someone asks you why you graded the lot a certain way.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer
http://bwengr.com | http://bwstructuralengineer.com | http://bwcivilengineer.com

RE: Grading help.

With regard to stormwater, be prepared to re-learn what to do with your stormwater in every state you work in. It's vastly different, state to state, and in some states it's vastly different from one municipality to another. The stormwater regulations in any given state are a confluence of many factors, including:

  • Topography
  • Climate
  • Soils
  • Groundwater
  • Vegetation
  • Politics
  • What universities are nearby
  • History of the people in charge and what has worked for them in the past (both state env protection staff and the state PE board)
  • How their nonpoint permits look with the EPA
etc etc. All those spill into stormwater regs, and come out differently everywhere you go.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Grading help.

I've given seminars about grading and have taught grading to a lot of new engineers at my company, and to draftsmen, too. Not everybody gets it at first, and some may never really get it at all, because grading is as much an art as a science, but the good news is that it gets easier with practice. My usual approach to one-on-one teaching is to have the trainee look over my shoulder while I do a grading plan, and show them my process. When the next project comes in, I have the trainee do the plan while I look over their shoulder. On the next one, I have the trainee do the plan on their own, and check in occasionally as they work.

Grading is a process. You often have to try an approach to see if it will work, and abandon it or revise it until you find a solution. When you start a new site you can expect to go around in circles a little bit until you find a solution that works. The amount of time you spend doing this should decrease as you gain experience, but it never really goes away completely. You'll still have to experiment a bit on every site. The key is to work very rough at first, until you are sure you are on the right track, then refine things after. That way you won't waste a lot of time fine-tuning a small area only to find out later that it can't connect with the rest of the site.

There is also a certain amount of visualization involved. At some point, if you keep at it, your brain may make a shift from working the numbers to understanding the shape of the surface you are designing. At that point, the process becomes much easier.

When I was preparing my first grading seminar, I found the attached article by an engineer by the name of Bruce Crawford (sorry, I don't remember where I got it. It was a long time ago). It has a lot of good information and is well worth reading, even if you are experienced in preparing grading plans.

I have also attached my "Grading Cheat Sheet" which contains helpful information. I give this to the people I am training, to hang on their wall as a reference while they work.

Hope this helps.

RE: Grading help.

For site grading, sit down and thoroughly study your existing topo. Sit on your hands.

Absolutely do not make a move until you have a firm understanding what the exisitng topo is speaking and imparting to you. See where things are draining off and what is coming on to your site. Note the existing slopes, etc.

Before you begin grading tell yourself you are going to try absolutely as much as possible to work with what the existing topography is giving.

Strive to mot make significant elevation changes to the existing topography. Only deviate from the trends of the existing topography as needed per code requirements and sound engineering design requirements and principles.

Strive to avoid implementing retaining walls and storm sewer. Wait until you absolutely have to, until you get stuck essentially with no other solution, or perhaps there is some unusual cost benefit to doing so, but usually it's the other way around. These things are expensive and create liability.

Do not concentrate runoff into conveyances until you absolutely have to. Strive to implement sheet flow regimes as much as possible. They are safer and create less liability issues. Always direct drainage away from foundations in all directions at slopes no less than code requirements.

Your clients will love you if your thoughtful designs minimize the use of walls, storm sewer and earthwork.

RE: Grading help.

I went to this book often for starting points when i had questions at a Civil Site firm a few years ago. my civil site firm was small and what i learned was that there were many preferences and styles to the work that really only learn by having your work reviewed by the principles and working with them.

A Successful Civil Site Designer is 1/3 Engineer, 1/3 Lawyer, and 1/3 Politician.


here is the table of contents.

Ch. 1 Overview of the Land Development Process
II Feasibility and Site Analysis
Ch. 2 Comprehensive Planning and Zoning
Ch. 3 Site Plan Ordinances, Subdivision Regulations, and Building Codes
Ch. 4 Exactions, Infrastructure Enhancements, and Fees
Ch. 5 Real Property Law
Ch. 6 Engineering Feasibility
Ch. 7 Environmental Regulations
Ch. 8 Environmental Site Assessments
Ch. 9 Historic and Archaeologic Assessment
Ch. 10 Market Analysis and Economic Feasibility
Ch. 11 The Rezoning Process
III Conceptual Design
Ch. 12 Development Patterns and Principles
IV Schematic Design
Ch. 13 Boundary Surveys for Land Development
Ch. 14 Control Surveys
Ch. 15 Topographic Surveys
Ch. 16 Preliminary Engineering
Ch. 17 Environmental and Natural Resources
Ch. 18 Historic Preservation and Archaeology
Ch. 19 Environmental Considerations
V Final Design
Ch. 20 Suburban Street Design
Ch. 21 Storm Drain Design
Ch. 22 Design of Stormwater Management Facilities
Ch. 23 Floodplain Studies
Ch. 24 Grading and Earthwork
Ch. 25 Wastewater Collection
Ch. 26 Water Distribution
Ch. 27 Wastewater Treatment
Ch. 28 Water Supply and Treatment
Ch. 29 Erosion and Sediment Control
Ch. 30 Contract Documents and Specifications
Ch. 31 Construction cost Estimating
VI Plan Submission and Permitting
Ch. 32 Subdivision Submittals
Ch. 33 Plan Submittal, Review, and Approval Process
Ch. 34 Environmental Permits
VII Construction
Ch. 35 Construction Stakeout Surveys
Ch. 36 Building Permits and Certificates of Occupancy
VIII Technical Appendices
Ch. 37 Geospatial Data
Ch. 38 Types of Drawings Used in Land Development
Ch. 39 Soils
Ch. 40 Case Study: Union Mills
Ch. 41 Technical Appendix

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