^Nielsen, David, ed. (1991). Practical handbook of ground-water [sic] monitoring. CRC Press LLC. p. 321. ISBN0-87371-124-6. "In wells more than about 50 feet deep, granular bentonite may be mixed with water and conveyed through a tremie pipe from the surface directly to its intended depth in the annulus; pelletized bentonite is not effectively installed through tremie pipes."