produced by the drilling industry. it looks like a long net. it's a filter. they call it a filter sock, it's used to filter the wastewater from the tracking sites to capture the solids from the fracking. it includes salts, compounds and radioactive materials like radium. and because the filters catch all that solid stuff, the filters themselves end up being radioactive. because these things are radioactive, you need to take some care in throwing them away. no landfill in north dakota is supposed to take a piece of waste that clocks in over 5 picocurries. shale reporter said last summer, one of them came in at 374 picocurries.