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• Section 785.19 (c) Continued. SDB=IRRIGATION Sub-irrigation is the process of supplying water to the root zone from below through saturated permeable soils, or capillary action in tight soils. The relative positions of the water table, capil- lary fringe and root zone through time as well as soil moisture and vegetation type indicates the presence or absence of sub-irrigation at a specific location. Correlation of alluvial ground water conditions in one location with other areas in similar stream valleys can be made by comparing lithology, soils, vegetation and any outside influences such as impoundments or diversions between areas. The quality of alluvial ground water is also central to its suitability for sub-irrigation. • Stiea~u Channel Gidund Watei Hydrolbgy The area surrounding the Kerr Tipple Area is a marsh in which the water table is above ground for nine months out of the year. The source of this water is recharge to the alluvial aquifer from the perennial Illinois River. The alluvium is sufficiently permeable to sustain sub-irrigation year-round. In order to evaluate the possibility of sub-irrigation from ground water in the mine plan area, a system of 20 shallow alluvial wells was installed in the intermittent drainages of Sudduth, Williams and Bush Draws to form transacts and longitudinal sections crossing the valleys, shown on Map 15, Kerr Mine Area Ground Water Hydrology. The wells were installed in backhoe pits to facilitate soil sam- pling and detailed logging of unconsolidated materials, and were constructed with perforated PVC casing to enable water monitoring and sampling. The lithologic logs of the backhoe pits are pre- sented in Exhibit 22, Drill Hole Logs. Data on lithology, top- soils, root zones and water monitoring from these logs were used in constructing Map 40, Kerr Mine Area Stream Channel Cross Sections. 785-18