Browsing by Subject "fault"

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    Dye Tracing Sewage Lagoon Discharge in a Sandstone Karst, Askov, Minnesota
    (Proceedings of the 10th Multidisciplinary Conference on Sinkholes and the Engineering and Environmental Impacts of Karst. © 2005 American Society of Civil Engineers. Published online: April 26, 2012, 2005-09-28) Alexander Jr., E. Calvin; Alexander, Scott C; Piegat, James J; Barr, Kelton D; Nordberg, Brad
    An investigation of the sandstone karst at Askov, Pine County, Minnesota was conducted utilizing fluorescent dye tracing techniques. Connections were documented between the effluent from WWTF lagoons discharged into a sinking stream and local residential water supply wells southwest of the stream sink, over kilometer-scale distances. The apparent velocity of dye from the steam sink to the residential well was 57 m/day, much faster than would be expected for porous-media flow in a sandstone but slower than expected for well-developed conduit karst in carbonate rock. The traces also document stage-dependent, divergent flow to the northeast and west from recharge to a sinkhole adjacent to the lagoons. A well-developed conduit system extends a few hundred meters under the northern portion of the lagoons with flow velocities greater than 128 m/day to the northeast. A slower flow system extends for at least a kilometer to the west and northwest with a range of apparent flow velocities that average about 9 m/day. The slower flow system reached a broad “fan” of residential wells to the west but was not detected in other wells in the same direction.