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Section 785.19 (d) Continued. r1 U Coal that they used lands in the areas as pastureland and irrigated hay meadows which were reported to produce one ton of hay per acre, but none of the owners knew how many tons of hay or animal unit months of grazing were derived from that portion of their ranch lying within the alluvial valley floor. In summary, insufficient data was available to document the quanti- ty of agriculture activities associated with the acknowledged alluvial valley floors in the mine plan, adjacent and tipple areas. However, the type of agricultural activities in the above areas is documented in Map 27, North Park Land Use. Potential Mateiial Damage. The determination of the risk of causing material damage to an alluvial valley floor is dependent on four criteria listed in 30 CFR 785.19(e). These criteria are: 1) potential increases in the • concentration of total dissolved solids (TDS) of waters supplied to an alluvial valley floor to levels above the threshold value at which crop yields decrease; 2) potential increases in the average depth to water that would reduce the amount of sub-irrigated land; 3) potential decrease in surface flows that would reduce the amount of flood irrigated land and 4) potential changes in the surface or ground water systems that reduce the area available to agriculture as a result of flooding or increased saturation of the root zone. The first subject area, the Illinois River floodplain, 1s sub- irrigated. There will be no mining and therefore no physical disturbance to the alluvial aquifer in the Illinois River flood- plain resulting from operations at the Kerr Tipple. The applicable criteria for determining material damage are potential TDS concen- tration as compared with crop salt tolerance and potential depth to water as compared with depth of the root zone. The average and maximum values of TDS listed in Table 10, Kerr Tipple Area Water 785-38