Dielectric constant, K • permittivity e = K eo where • K=1 • =4 • =6 • = 20 • = 81 eo = 1/36 p x 10 -9 sec/ohm-m air gasoline dry sand wet sand water V = 30 cm/ns = 15 = 12. 25 = 6. 7 = 3. 33
Gasoline Spill at OGI
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.
GPR Characteristics • 80 -1200 MHz • Uses true EM reflections • Textures, petrochemicals, UXO. . . • High rez (~10 cm) • Fast ( km/hr) • Can work near cultural noise • Maximum depth penetration <~30 m • Can’t penetrate conductive ground (>~30 m. S/m) – clays – brackish porewaters • Realistic sections