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Value

Assigned Points

<700

10

700 to 1,000

8

1,000 to 1,200

5

1,200 to 1,500

2

1,500 to 2,000

1

>2,000

0

0 to 2

5

2 to 4

3

4 to 6.5

0

6.5 to 7.5

0

7.5 to 8.5

0

>8.5

3

>100

0

50 to 100

3.5

0 to 50

4

<0

5

Positive

3.5

Trace

2

Negative

0

Poor drainage, continuously wet

2

Fair drainage, generally moist

1

Good drainage, generally dry

0

Table 16. Numerical Corrosivity Scale (ANSI, 1999)

Soil Parameter

Resistivity, Ohm·cm

pH

Reduction/oxidation potential, mV

Sulfides

Moisture

Soil Conductivity

The conductivity of the water/soil mixture will be directly related to the concentration of dissolved ionic species such as salts and minerals. This variable will be controlled by the nature of the specific soil surrounding the appurtenance. The availability of water will also be a property of the soil as well as the particular environment, which includes the amount of rainfall and depth of the water table and the burial depth of the appurtenance.

Temperature Considerations

Soil temperature variations at the surface are not likely to have a significant role in affecting appurtenance corrosion rates except when they control the amount of moisture entering the soil, or in the extreme case of completely drying out the soil. Temperature variation of the

Alternative Underground Propane Tank Materials, Phase II—Final Report

26

September 2009 Battelle and Lincoln Composites

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