Laserfiche WebLink
• In summary, the low groundwater recharge rates at the Trapper "line indicate that <br />transport (if any) of contaminants from the waste to the water table will be <br />extremely slow. <br />10 <br />Moreover, infiltrating water which may reach the surface of the disposal waste <br />will tend to move laterally through the spoils, rather than through the waste, if <br />spoil permeabilities are signficantly higher than waste permeabilities. Availa- <br />ble data show that this in fact will be the case and after mining, permeabilities <br />for the spoil will be higher than undisturbed overburden permeablities. Several <br />sources of information exist concerning spoil permeabilities: <br />Stearns -Roger laboratory hydraulic conductivity measurements on <br />artificially weathered borehole core samples of the Trapper overburden <br />(Stearns -Roger, 1974), <br />Radian infiltrometer studies (part of the groundwater recharge studies), <br />and <br />Literature references on studies of spoil permeabilities of various U.S. <br />surface mines (Wilson and Hamilton, 1978)(Holland, 1979). <br />The Stearns -Roger permeabilities for two core samples range from about .001 to <br />.88 gpd/ft2 (2.8 x 10-7 to 4,1 x 10-5 cm/sec). These are for weathered <br />samples and are probably much lower than the actual average spoil permeability, <br />because weathering would occur only very near the spoil surface. <br />Radian infiltrometer data ranged from 6.48 gpd/ft2 to 115.4 gpd/ft2 (3 x <br />10-4 to 5 x 10-3 em/sec). <br />Literature sources indicate that spoil permeabilities may be 6-10 times greater <br />than permeabilities for undisturbed consolidated overburden. Assuming a 1 gpd/ft <br />average permeability for the Upper Williams Fork, average spoil permeabilities <br />would range from 6-10 gpd/ft2 (3 x 10-4 to 5 x 10-4 cm/sec). <br />4-51 <br />