1. EM Wave Theory Simplifications: Conductors: s>>we Dielectrics:

2. Conductors and Dielectrics
Skin depth
= SQRT (2/wms)
Wave speed
= SQRT (2w/ms)
Wavelength
= 2p SQRT (2/wms)
Note - ms are together
Skin depth
= 2 SQRT (e/m) / s
Wave speed
= 1 / SQRT (me)
Wavelength
= 2p / w SQRT (me)
Note - e appears here

3. EM Spectrum GPR frequencies Lowest ~80 MHz Highest ~1200 MHz
sees deepest— ~30m
but poor rez.
Highest ~1200 MHz
Shallow— ~10 cm
High rez

4. Monitoring Remediation: GPR

5. GPR Antennas 100 Mhz 200MHz 500 Mhz 900 Mhz (lair= 300 cm) ( 150 cm)

6. Dielectric constant, K
permittivity e = K eo where eo = 1/36p x sec/ohm-m
K = 1 air V = 30 cm/ns
= gasoline = 15
= dry sand = 12.25
= wet sand = 6.7
= water = 3.33

8. Gasoline Spill at OGI

9. Things to notice
Gasoline spreads in fingers, maybe reflecting microtextures in the sand.
The fingers wax (and wane?) as heads build up at the source. They pulse outward.
(Not shown) A repeat survey done the following spring showed bright spots (gas pockets) scattered at different depths.

12. GPR Characteristics 80-1200 MHz Uses true EM reflections
Textures, petro-chemicals, UXO...
High rez (~10 cm)
Fast ( km/hr)
Can work near cultural noise
Maximum depth penetration <~30m
Can’t penetrate conductive ground (>~30 mS/m)
clays
brackish porewaters
Realistic sections