1

Section: Plant & Soil Science

Unit: Soil Management

Lesson Title: Homesite evaluations

2

SURFACE TEXTURE

• A certain feel based on their make-up sand, silt, and clay,

• Classified as fine, medium, and coarse.

TEXTURE CLASSES

FINE clay (C), sandy clay (SC), clay loam (CL), silty clay (SiC), silty clay loam (SiCL)

MEDIUM sandy clay loam (SCL), loam (L), silt loam (SiL), silt (Si)

COARSE sand (S), loamy sand (LS), sandy loam (SL)

3

PERMEABILITY

PERMEABILITY CLASSES

VERY SLOW Sandy clay, silty clay, and clay subsoils are plastic and sticky when wet and very hard when

dry

SLOW Clay loam, sandy clay loam and silty clay loam subsoils, often with subangular blocky or massive structure

MODERATE Sandy loam, loam, silt loam and silt subsoils with weak prismatic to blocky structure

RAPID Sand and loamy sand subsoils

•The speed of internal soil drainage. What areas do you think internal drainage affects?

4

SOIL DEPTH

• The vertical depth of surface soil plus subsoil plus any material to a level that would restrict root penetration or inhibit excavation.

• A factor for basements and determining the style of the house.

• Soil depth can be very shallow, shallow, moderately deep, deep, or very deep.

5

SLOPE

• Refers to the inclination of the soil surface, and has a direct influence on site drainage.

• Slopes are broken down into;

Gentle, moderate, Strong, Steep, and

Very Steep.

6

EROSION

•Loss of topsoil, airborne soil particles

•Soil piling up in areas not wanted, and severe rills and gullies create problems for septic systems, landscaping and other uses.

•Must be given a soil erosion rating of; slight, moderate, severe, very severe.

7

Soil Erosion con’tSOIL EROSION CLASSES

NONE-SLIGHT There is little or no evidence of soil movement. Plants and rocks show little to no evidence of pedestalling. Gullies are absent.

MODERATE Litter is deposited against rocks and plant crowns. Small rock and plant pedestals are present. Rills ½ to 6 inches deep are present at > 10 foot intervals. Gullies are present and eroding along < 10% of their length.

SEVERE Soil is deposited against rocks and plant crowns. Most rocks and plants are pedestalled and plant roots may be exposed. Rills 3 to 6 inches deep may be present at <5 foot intervals. Gullies are numerous, well-developed eroding along > 50 % of their length, and are > 100 feet apart.

VERY SEVERE Frequent, uncrossable gullies are present. Blow-outs may be numerous and deep. Wind deposits may be present.

8

Surface runoff

SURFACE RUNOFF CLASSESSLOW Occurs on 0-3% slopes and coarse textured

soils.

MODERATE May occur on 3-5% slopes where soils are not coarse textured.

RAPID Usually occurs on >5% slopes where soils are not coarse textured.

•Surface run-off is a problem when water runs off of the surface before it goes into the soil.

•Most worried about water running off from above and into our home.

9

Shrink-swell

SHRINK-SWELL CLASSES AND LIMITATIONSNone-slight sand, loamy sand and sandy loam soils

Moderate loam, silt loam, silt, clay loam, sandy clay loam and silty clay loam soils

Severe sandy clay, silty clay and clay soils

•Clay percentage determines amount of shrink and swell

•Smectite clay will trap water molecules causing them to swell to many times their original size, shrinking back to their original size when the water is removed.

•The horizon having the most clay should be considered when determining shrink-swell limitations.

10

Water Table

• Refers to how far it is to available water.

• A shallow water table will cause many problems for a home site.

• Look at the time of the year when the water table is the closest to the surface.

• Water table depth can be broken into the following areas: slight, moderate, and severe.

11

Flooding

• As home areas become urbanized and the area becomes “sealed” with asphalt or concrete, surface runoff increases dramatically.

• If the site is close to a floodplain, the flood hazard may also increase.

• Landscape position and proximity to streams are flood hazard indicators.

• Our ratings are; None, Rare, and Frequent.

12

Surface Texture

Building Foundations

LandscapingSeptic

SystemsSewage Lagoons

Fine Severe Severe

Medium None-Slight None-Slight

Coarse Moderate Moderate

13

Permeability

Building Foundations

LandscapingSeptic

SystemsSewage Lagoons

Very Slow Severe Very SevereNone to Slight

Slow Moderate SevereNone to Slight

ModerateNone to Slight

Moderate Moderate

Rapid Moderate Very Severe Severe

14

Soil DepthDepth

(inches)Building

Foundation LandscapingSeptic

SystemsSewage Lagoons

Very Shallow

<10Very

SevereVery Severe

Very Severe

Very Severe

Shallow 10-20 Severe SevereVery

SevereVery

Severe

Moderately Deep

20-40 Moderate Moderate Severe Severe

Deep 40-72 None-Slight None-Slight Moderate Moderate

Very Deep >72 None-Slight None-SlightNone-Slight

None-Slight

15

Slope

Slope (%) Building Foundation Landscaping

Septic Systems

Sewage Lagoons

Nearly Level

0-3 None-Slight None-SlightNone-Slight

None-Slight

Moderate 3-5 None-Slight None-SlightNone-Slight

Moderate

Strong 5-8 None-Slight None-SlightNone-Slight

Moderate

Steep 8-15 Moderate Moderate Moderate Severe

Very Steep

>15 Severe Severe Severe Severe

16

Erosion

Building Foundations

LandscapingSeptic

SystemsSewage Lagoons

None-Slight None-Slight None-Slight None-Slight None-Slight

Moderate None-Slight None-Slight None-Slight None-Slight

Severe Moderate Moderate Moderate Moderate

Very Severe Severe Severe Severe Severe

17

Surface Run-off

Building Foundations

LandscapingSeptic

SystemsSewage Lagoons

Slow Severe None-Slight Severe

Moderate None-Slight None-Slight None-Slight

Rapid None-Slight Severe None-Slight

18

Shrink-swell

Building Foundations

LandscapingSeptic

SystemsSewage Lagoons

Low None-Slight None-Slight None-Slight

Moderate Moderate Moderate Moderate

High Severe Severe Severe

19

Water Table

Building Foundations

LandscapingSeptic

SystemsSewage Lagoons

Slight >30” >24” >72” >60”

Moderate 18-30” 12-24” 48-72” 40-60”

Severe <18” <12” <48” <40”

20

Flooding

Building Foundations

LandscapingSeptic

SystemsSewage Lagoons

None None-Slight None-Slight None-Slight None-Slight

Occasional Severe None-Slight Moderate None-Slight

Frequent Severe Severe Severe Severe