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Vadose Zone Penetration

Environmental Engineering · FE Reference Handbook section

Environmental Engineering
5 formulas
10 exam-style examples
~55 min
All Environmental Engineering lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • Soil Gasoline Kerosene Light Fuel Oil
  • A constant value representing capacity of soil and viscosity of product
  • Data from Shepherd, W. D. No date. Practical Geohydrological Aspects of Groundwater Contamination.
  • Dept. of Environmental Affairs, Houston: Shell Oil, as published in Underground Storage Tank

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Vadose Zone Penetration — solve for time to reach water table — Vadose Zone Penetration

vadose zone penetration time for a spill migrating to groundwater Given depth to water table (d) = 26.5000 m; field capacity (FC) = 0.3900; infiltration rate (I) = 0.0250 m/day, determine the time to reach water table (t) in day.

Given

  • depthtowatertable(d)=26.5000mdepth to water table (d) = 26.5000 m
  • fieldcapacity(FC)=0.3900field capacity (FC) = 0.3900
  • infiltrationrate(I)=0.0250m/dayinfiltration rate (I) = 0.0250 m/day

Find

time to reach water table (t), in day

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except t is given, so isolate t symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for t:

    t=d FCIt = \dfrac{d\,FC}{I}
  3. Step 3 — List the givens: depth to water table (d) = 26.5000 m, field capacity (FC) = 0.3900, infiltration rate (I) = 0.0250 m/day.

  4. Step 4 — Substitute the given values:

    t=26.5000 0.39000.0250t = \dfrac{26.5000\,0.3900}{0.0250}
  5. Step 5 — Evaluate:

    t=413.4 dayt = 413.4\ \text{day}
  6. Step 6 — Check: returning t = 413.4 day to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
t=413.4 dayt = 413.4\ \text{day}

Why the other options are there

  • 826.8 — kept a factor of two that cancels in the correct rearrangement.
  • 206.7 — dropped that same factor in the other direction.
  • 454.7 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 2
Vadose Zone Penetration — solve for depth to water table — Vadose Zone Penetration (2)

vadose zone penetration estimate given field capacity and infiltration rate Given field capacity (FC) = 0.1600; infiltration rate (I) = 0.0300 m/day; time to reach water table (t) = 4,455 day, determine the depth to water table (d) in m.

Given

  • fieldcapacity(FC)=0.1600field capacity (FC) = 0.1600
  • infiltrationrate(I)=0.0300m/dayinfiltration rate (I) = 0.0300 m/day
  • timetoreachwatertable(t)=4,455daytime to reach water table (t) = 4,455 day

Find

depth to water table (d), in m

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except d is given, so isolate d symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for d:

    d=tIFCd = \dfrac{tI}{FC}
  3. Step 3 — List the givens: field capacity (FC) = 0.1600, infiltration rate (I) = 0.0300 m/day, time to reach water table (t) = 4,455 day.

  4. Step 4 — Substitute the given values:

    d=44550.03000.1600d = \dfrac{44550.0300}{0.1600}
  5. Step 5 — Evaluate:

    d=835.3 md = 835.3\ \text{m}
  6. Step 6 — Check: returning d = 835.3 m to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
d=835.3 md = 835.3\ \text{m}

Why the other options are there

  • 1,671 — kept a factor of two that cancels in the correct rearrangement.
  • 417.7 — dropped that same factor in the other direction.
  • 918.8 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 3
Vadose Zone Penetration — solve for infiltration rate — Vadose Zone Penetration (3)

vadose zone penetration analysis above the water table Given depth to water table (d) = 18.5000 m; field capacity (FC) = 0.1800; time to reach water table (t) = 4,275 day, determine the infiltration rate (I) in m/day.

Given

  • depthtowatertable(d)=18.5000mdepth to water table (d) = 18.5000 m
  • fieldcapacity(FC)=0.1800field capacity (FC) = 0.1800
  • timetoreachwatertable(t)=4,275daytime to reach water table (t) = 4,275 day

Find

infiltration rate (I), in m/day

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except I is given, so isolate I symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for I:

    I=d FCtI = \dfrac{d\,FC}{t}
  3. Step 3 — List the givens: depth to water table (d) = 18.5000 m, field capacity (FC) = 0.1800, time to reach water table (t) = 4,275 day.

  4. Step 4 — Substitute the given values:

    I=18.5000 0.18004275I = \dfrac{18.5000\,0.1800}{4275}
  5. Step 5 — Evaluate:

    I=0.0008 m/dayI = 0.0008\ \text{m/day}
  6. Step 6 — Check: returning I = 0.0008 m/day to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
I=0.0008 m/dayI = 0.0008\ \text{m/day}

Why the other options are there

  • 0.0016 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0004 — dropped that same factor in the other direction.
  • 0.0009 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 4
Vadose Zone Penetration — solve for time to reach water table (case 2) — Vadose Zone Penetration (4)

vadose zone penetration time for a spill migrating to groundwater Given depth to water table (d) = 24.5000 m; field capacity (FC) = 0.1500; infiltration rate (I) = 0.0030 m/day, determine the time to reach water table (t) in day.

Given

  • depthtowatertable(d)=24.5000mdepth to water table (d) = 24.5000 m
  • fieldcapacity(FC)=0.1500field capacity (FC) = 0.1500
  • infiltrationrate(I)=0.0030m/dayinfiltration rate (I) = 0.0030 m/day

Find

time to reach water table (t), in day

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except t is given, so isolate t symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for t:

    t=d FCIt = \dfrac{d\,FC}{I}
  3. Step 3 — List the givens: depth to water table (d) = 24.5000 m, field capacity (FC) = 0.1500, infiltration rate (I) = 0.0030 m/day.

  4. Step 4 — Substitute the given values:

    t=24.5000 0.15000.0030t = \dfrac{24.5000\,0.1500}{0.0030}
  5. Step 5 — Evaluate:

    t=1225 dayt = 1225\ \text{day}
  6. Step 6 — Check: returning t = 1,225 day to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
t=1225 dayt = 1225\ \text{day}

Why the other options are there

  • 2,450 — kept a factor of two that cancels in the correct rearrangement.
  • 612.5 — dropped that same factor in the other direction.
  • 1,348 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 5
Vadose Zone Penetration — solve for depth to water table (case 2) — Vadose Zone Penetration (5)

vadose zone penetration estimate given field capacity and infiltration rate Given field capacity (FC) = 0.3600; infiltration rate (I) = 0.0540 m/day; time to reach water table (t) = 225.0 day, determine the depth to water table (d) in m.

Given

  • fieldcapacity(FC)=0.3600field capacity (FC) = 0.3600
  • infiltrationrate(I)=0.0540m/dayinfiltration rate (I) = 0.0540 m/day
  • timetoreachwatertable(t)=225.0daytime to reach water table (t) = 225.0 day

Find

depth to water table (d), in m

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except d is given, so isolate d symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for d:

    d=tIFCd = \dfrac{tI}{FC}
  3. Step 3 — List the givens: field capacity (FC) = 0.3600, infiltration rate (I) = 0.0540 m/day, time to reach water table (t) = 225.0 day.

  4. Step 4 — Substitute the given values:

    d=225.00.05400.3600d = \dfrac{225.00.0540}{0.3600}
  5. Step 5 — Evaluate:

    d=33.7500 md = 33.7500\ \text{m}
  6. Step 6 — Check: returning d = 33.7500 m to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
d=33.7500 md = 33.7500\ \text{m}

Why the other options are there

  • 67.5000 — kept a factor of two that cancels in the correct rearrangement.
  • 16.8750 — dropped that same factor in the other direction.
  • 37.1250 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 6
Vadose Zone Penetration — solve for infiltration rate (case 2) — Vadose Zone Penetration (6)

vadose zone penetration analysis above the water table Given depth to water table (d) = 9.5000 m; field capacity (FC) = 0.4000; time to reach water table (t) = 1,971 day, determine the infiltration rate (I) in m/day.

Given

  • depthtowatertable(d)=9.5000mdepth to water table (d) = 9.5000 m
  • fieldcapacity(FC)=0.4000field capacity (FC) = 0.4000
  • timetoreachwatertable(t)=1,971daytime to reach water table (t) = 1,971 day

Find

infiltration rate (I), in m/day

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except I is given, so isolate I symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for I:

    I=d FCtI = \dfrac{d\,FC}{t}
  3. Step 3 — List the givens: depth to water table (d) = 9.5000 m, field capacity (FC) = 0.4000, time to reach water table (t) = 1,971 day.

  4. Step 4 — Substitute the given values:

    I=9.5000 0.40001971I = \dfrac{9.5000\,0.4000}{1971}
  5. Step 5 — Evaluate:

    I=0.0019 m/dayI = 0.0019\ \text{m/day}
  6. Step 6 — Check: returning I = 0.0019 m/day to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
I=0.0019 m/dayI = 0.0019\ \text{m/day}

Why the other options are there

  • 0.0039 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0010 — dropped that same factor in the other direction.
  • 0.0021 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 7
Vadose Zone Penetration — solve for time to reach water table (case 3) — Vadose Zone Penetration (7)

vadose zone penetration time for a spill migrating to groundwater Given depth to water table (d) = 24.5000 m; field capacity (FC) = 0.1700; infiltration rate (I) = 0.0050 m/day, determine the time to reach water table (t) in day.

Given

  • depthtowatertable(d)=24.5000mdepth to water table (d) = 24.5000 m
  • fieldcapacity(FC)=0.1700field capacity (FC) = 0.1700
  • infiltrationrate(I)=0.0050m/dayinfiltration rate (I) = 0.0050 m/day

Find

time to reach water table (t), in day

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except t is given, so isolate t symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for t:

    t=d FCIt = \dfrac{d\,FC}{I}
  3. Step 3 — List the givens: depth to water table (d) = 24.5000 m, field capacity (FC) = 0.1700, infiltration rate (I) = 0.0050 m/day.

  4. Step 4 — Substitute the given values:

    t=24.5000 0.17000.0050t = \dfrac{24.5000\,0.1700}{0.0050}
  5. Step 5 — Evaluate:

    t=833.0 dayt = 833.0\ \text{day}
  6. Step 6 — Check: returning t = 833.0 day to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
t=833.0 dayt = 833.0\ \text{day}

Why the other options are there

  • 1,666 — kept a factor of two that cancels in the correct rearrangement.
  • 416.5 — dropped that same factor in the other direction.
  • 916.3 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 8
Vadose Zone Penetration — solve for depth to water table (case 3) — Vadose Zone Penetration (8)

vadose zone penetration estimate given field capacity and infiltration rate Given field capacity (FC) = 0.2200; infiltration rate (I) = 0.0700 m/day; time to reach water table (t) = 4,253 day, determine the depth to water table (d) in m.

Given

  • fieldcapacity(FC)=0.2200field capacity (FC) = 0.2200
  • infiltrationrate(I)=0.0700m/dayinfiltration rate (I) = 0.0700 m/day
  • timetoreachwatertable(t)=4,253daytime to reach water table (t) = 4,253 day

Find

depth to water table (d), in m

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except d is given, so isolate d symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for d:

    d=tIFCd = \dfrac{tI}{FC}
  3. Step 3 — List the givens: field capacity (FC) = 0.2200, infiltration rate (I) = 0.0700 m/day, time to reach water table (t) = 4,253 day.

  4. Step 4 — Substitute the given values:

    d=42530.07000.2200d = \dfrac{42530.0700}{0.2200}
  5. Step 5 — Evaluate:

    d=1353 md = 1353\ \text{m}
  6. Step 6 — Check: returning d = 1,353 m to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
d=1353 md = 1353\ \text{m}

Why the other options are there

  • 2,706 — kept a factor of two that cancels in the correct rearrangement.
  • 676.6 — dropped that same factor in the other direction.
  • 1,489 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 9
Vadose Zone Penetration — solve for infiltration rate (case 3) — Vadose Zone Penetration (9)

vadose zone penetration analysis above the water table Given depth to water table (d) = 13.5000 m; field capacity (FC) = 0.2000; time to reach water table (t) = 63.0000 day, determine the infiltration rate (I) in m/day.

Given

  • depthtowatertable(d)=13.5000mdepth to water table (d) = 13.5000 m
  • fieldcapacity(FC)=0.2000field capacity (FC) = 0.2000
  • timetoreachwatertable(t)=63.0000daytime to reach water table (t) = 63.0000 day

Find

infiltration rate (I), in m/day

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except I is given, so isolate I symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for I:

    I=d FCtI = \dfrac{d\,FC}{t}
  3. Step 3 — List the givens: depth to water table (d) = 13.5000 m, field capacity (FC) = 0.2000, time to reach water table (t) = 63.0000 day.

  4. Step 4 — Substitute the given values:

    I=13.5000 0.200063.0000I = \dfrac{13.5000\,0.2000}{63.0000}
  5. Step 5 — Evaluate:

    I=0.0429 m/dayI = 0.0429\ \text{m/day}
  6. Step 6 — Check: returning I = 0.0429 m/day to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
I=0.0429 m/dayI = 0.0429\ \text{m/day}

Why the other options are there

  • 0.0857 — kept a factor of two that cancels in the correct rearrangement.
  • 0.0214 — dropped that same factor in the other direction.
  • 0.0471 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

Example 10
Vadose Zone Penetration — solve for time to reach water table (case 4) — Vadose Zone Penetration (10)

vadose zone penetration time for a spill migrating to groundwater Given depth to water table (d) = 4.0000 m; field capacity (FC) = 0.3700; infiltration rate (I) = 0.0840 m/day, determine the time to reach water table (t) in day.

Given

  • depthtowatertable(d)=4.0000mdepth to water table (d) = 4.0000 m
  • fieldcapacity(FC)=0.3700field capacity (FC) = 0.3700
  • infiltrationrate(I)=0.0840m/dayinfiltration rate (I) = 0.0840 m/day

Find

time to reach water table (t), in day

Start with the thinking

  • The governing relation printed in this handbook section is Vadose Zone Penetration.
  • Everything except t is given, so isolate t symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Vadose zone penetration estimates travel time for an infiltrating contaminant to move through the unsaturated zone to the water table.

Step-by-step solution

  1. Step 1 — State the governing relation:

    t=d×FCIt = \dfrac{d \times FC}{I}
  2. Step 2 — Rearrange symbolically for t:

    t=d FCIt = \dfrac{d\,FC}{I}
  3. Step 3 — List the givens: depth to water table (d) = 4.0000 m, field capacity (FC) = 0.3700, infiltration rate (I) = 0.0840 m/day.

  4. Step 4 — Substitute the given values:

    t=4.0000 0.37000.0840t = \dfrac{4.0000\,0.3700}{0.0840}
  5. Step 5 — Evaluate:

    t=17.6190 dayt = 17.6190\ \text{day}
  6. Step 6 — Check: returning t = 17.6190 day to

    t=d×FCIt = \dfrac{d \times FC}{I}

    reproduces the given quantities, and both sides carry the same units.

Answer:
t=17.6190 dayt = 17.6190\ \text{day}

Why the other options are there

  • 35.2381 — kept a factor of two that cancels in the correct rearrangement.
  • 8.8095 — dropped that same factor in the other direction.
  • 19.3810 — rounded an intermediate value before the final step.

Reference: FE Handbook — Vadose Zone Penetration

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