Te Soil type characteristics

[DPAJR]

Hi,

I am working on a drainage project which has a large ravine running down the middle. The NRCS soil map classifies it as Te Terrace Escarpments. Every reference to Te I have found on the internet leaves all the characteristics such as available water capacity, depth to restrictive layer etc totally blank. It is surrounded on the upper end by soils with high runoff potential and on the lower end by soils with very low runoff potentials.

Should I just assume it has a high CN like 85 or even more or does anyone know of a reference that spells it out a little better. It is located near Lake Chelan, WA.

Thanks

 

[froude]

If you know the hydrologic soil group (A,B,C,D) for that particular soil, you can use TR-55 (Urban Hydrology for Small Watersheds; NRCS) to determine either a base CN or a composite CN.

If you have GIS, you can probably download the soil survey as a shapefile. A lot of times, the soils will be attributed with the Hydrologic Soil Group. If it isn't, you can browse through the associated text files and find the HSG for any given MUKEY or MYSYM.

Hope this helps!

 

[voodoo032]

You should be able to get soils information using this process:

1. go to

http://soildatamart.nrcs.usda.gov/

and select your state (WA)
2. select the county where the soil is located
3. click Select Survey Area
4. click on "Generate Reports"
5. select the soil mapping unit you want info or "Select All"
6. go to the report pulldown menu and select RUSLE2 Related Attributes
7. click on "Generate Report", the window that opens up should have the soil group data in it.

This is the process I use when I need soil group info for stormwater reports.

See the attached PDF. Note that you can get other/more info depending on your report selection.

Jon

 

[beej67]

Froude and Voodoo, I think he's saying he already has a NRCS soils map, possibly from the web, and his soil type (Te) doesn't have a standard TR55 listing for A, B, C, or D with it.

I personally have no experience with a Te soil type, but it sounds quite a bit like the Urban classification in urbanized watersheds. The NRCS generally won't tell you what the physical characteristics are for soil strata that have been disturbed by development, because those characteristics could vary widely with the type of disturbance, compaction, where the fill dirt came from, etc.

Assuming this is what Te means (I'm still not sure) then your best bet is probably to make a conservative assumption and use the soil classification nearest the Te soils that would give you the highest CN.



Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[DPAJR]

Hi beej67,

You are right. That is exactly what I have. NRCS listed the Te soil but it only gave about half the information it gives for other soil types like CIB, CkE, MgD, EnF etc. Those list storage capacity, infiltration rates etc. Te only lists elevation, frost free period, and a typical profile

0-6 inches loamy sand
6 to 60 inches extremely gravelly sand

Thanks voodoo032,

That was a very good suggestion but I had already been there. Even so I appreciate the trouble you went to especially to trouble to note each and every step along the way. I'm sure there will be others who view this thread who gain from that.

Thanks again
dpa

 

[beej67]

Well if it gives you a typical profile, then you could fish through soils in your area to find a similar profile and then use its properties. That might be a reasonable assumption. Make sure you document your assumptions though, and if you're presenting it to a regulatory agency, get their buy in before you go too far with your engineering.



Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[amb2002]

I did a quick search on the Web Soil Survey (found here:

http://websoilsurvey.nrcs.usda.gov/app/

). The Te soil type is identified as being a HSG A soil. See the attachment for additional information.

I did not print them, but that website has the values for the available water capacity, depth to restrictive layer, etc. for the Te soils.

Hope that is helpful.