Grading Plans in Texas

[gjeppesen]

Hi All,

I'm a SW Florida-trained engineer doing my first job in Texas, which is a small bank site. Where I work in Florida, it is so flat that we never use contour grading, just spot elevations. I need your expertise on babying me through the proper way to produce a grading plan using contours. How does one going about starting, setting building floor elevation, rules of thumb, etc? Rock factor?

In FL, storm event stages govern floor elevations, etc. and that isn't the case most other places.

Thanks for your help.

 

[msquared48]

I start at the outfall and back up everything from there to set the floor elevation. In flat terrain, the level of the outfall controls everything.

Mike McCann
MMC Engineering

 

[MiketheEngineer]

Hire a local engineer to help you out??

 

[civilman72]

Starting at the outfall is a good idea, but may not be the ultimate control. Very often the controlling factor of the building elevation will be ADA access from existing sidewalks/roads. If you think this may be the controlling factor, start with defining your ADA access, using maximum allowable ADA grades from existing walks to you proposed building. Once you've set your building elevation, you can then make sure things will drain, maintain acceptable parking lot grades, and that you can daylight your cut/fill slopes within your property.

In doing all of this you will be creating spot elevations along the way. Once you've got the spot elevations, you then can create the contours.

 

[BAWANY]

Start from the driveways with minimum and maximum slopes. 24' Firelanes will surround the building. There should be two Drives. The firelane slope should be away from the building. The building sidewalk will not exeed 2% x-slopes. The Architect should provide the layout with parkings. The ADA parking shall not exceed 2%. The drainage area map before and after shall be the same with no increase in run off if detention is not taken care of, depends on the city. If this is not enough provide more information

 

[BAWANY]

Based on existing grades, the proposed grades will follow the existing grade. The first step is to create the spot elevations. When all spot elevations work well either using land development or manually interpolate for even spots. Join all even spots will create contours

 

[gjeppesen]

OK. What about if through all of this, I determine that I need a retaining wall. Is it best to locate it on the higher ground or low ground.

 

[bank]

A lot depends on where you are in Texas. Houston also is extremely flat. The first constraints in determining the finished floor elevation are the nearest sanitary sewer rim elevation, the highest crown elevation on the adjacent streets, and the Base Flood Elevation if your site is in the 100-year flood plain. Your FF must be at least a foot above all three. After that you can consider ADA access, i.e., maximum 5% slope in the direction of travel along sidewalks unless there is a ramp, and 2% max in handicap parking areas.

 

[msquared48]

I thought that the building departments in Texas just checked the plans. I didn't know that they graded them too!

Mike McCann
MMC Engineering

 

[bank]

The City or local agency will always check to make sure the finished floor elevation meets the stated requirements. Grading the site is up to the design engineer, except that in many jurisdictions, including Houston, you won't get a Certificate of Occupancy until Texas Department of Licensing and Regulation (TDLR) inspects the site for ADA compliance.

 

[chicopee]

gjeppesen, didn't you have a surveying course in college?

 

[gjeppesen]

chicopee,

Of course I did. My question is related to plan production, and the path of least resistance in producing a contour grading plan.

bank,

Where is it written that FF needs to be 1 foot above the things you mention?

 

[GoldDredger]

I wish I had a nice little bank job to work on now.

I think the main point is start from your drainage outfall and work up to your finished floor, alot of times on an infill type project, the outfall will be the acess drive.

In Dallas your finished floor has to be 1' above the rim of the downstream sanitary manhole from your connect (in case it gets blocked up) I don't know of other juristictions that require that.

If part of the building footprint happened to be located in a 100 year floodplain, you would have to set your finished floor above that, minimum 1' but 18" I think is more common.

Then beware of the ADA issues, called 'TAS' in Texas. (Texas Accessibilty Standards). Buildings have to go through TDLR review by a TAS specialist..confusing I know.

Anyway that will govern your slopes for HC parking and route to/from building and to/from public sidewalk.

GL

 

[bank]

gjeppesen,

The flood plain requirements are laid out in the City of Houston Code of Ordinances. The other two items (crown of street and sanitary sewer manhole rim elevations) are probably building code requirements, but I couldn't tell you where to find them. Looks like they've got some of the same requirements in Dallas.