One of the most vocal concerns regarding the development of large intensive hog operations is the possbility of ground water contamination from the earthen manure storage (EMS) facility. Regulations regarding the construction of an EMS is to maintain a minimum seepage rate through the earthen material. Current regulations suggest a clay content of 15% and a plasticity index of 10% should be achieved in order to properly construct a EMS. Researchers at the University of Saskatchewan studied the impact of ponded hog manure on flow rate, attempting to answer the following specific questions: (1) How much is flow reduced? (2) Does texture have an effect upon flow reduction? (3) Does length of time of manure ponding have an effect on flow reduction? (4) Is the flow reduction due toa seal and/or clogging within the soil? (5) What is the durability of the seal or clogging? (6) What is the effect of flow rates upon seal removal?

Seven different soils ranging in caly content from 9-33% were studied using 20cm soils column tests in a low-temperature (5-6 degress Celcius) environment. The average hydraulic conductivity values measured with water ranged from 2.63 x 10 exp -8 m/s to 131.8 x 10 exp -8 m/s. The hydrualic conducivity rapidly decreased within the first hour with a very thin black layer resting on the soil surface. Hydrualic conductivity values for all soil types (regardless of natural conductivity of the soil) dropped to about 0.1 x 10 exp -8 m/s within 3-6 weeks of ponding manure. The seal increased downward at a rate of 0.3 mm/month. The formation of the manaure seal is the primary factor for the reduction of hydrualic conductivity of all soils types tested. The text as well as the amount of time of manure ponding seems to have little effect upon flow reduction. However the seal seems to be temperature sensitive; unplanned heating events during the course of the experiment resulting in increased flow rates, average hydrualic conducivity rose from 0.10 x 10 exp -8 m/s to 0.36 x 10 exp -8 m/s when temperatures rose for the period of one day. Seal removal followed by ponding with a chemical solution resulted in the hydrualic conducivity returning back to original values measured with water.