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Those areas where control activities were more extensive are shown on Exhibit 91.4 as areas • shaded with small dots. Canada thistle (Cirs ium arvense) uas [he primary target species in all control areas, with lesser activity directed towards areas of whitetop (Cardari drabs). Monitoring was conducted in 1991 to determine the need or level of retreatment necessary for areas sprayed in 1990. The applied herbicide consisted of a tank mix of 2.5 gallons of 22k Tordon and 2.5 gallons of 2, 4-D amine with 250 gallons of water. A spot spray gun was used to concentrate control activities on target areas, reducing potential impacts to ., adjacent desirable vegetation. The herbicide mix, based on recommendations from the Colorado State Extension Service, was mixed and applied under the supervision of a certified applicator. The weed control areas will be monitored in 1992 for effectiveness and potential retreatment. Revegetation monitoring was conducted by ESCO Associates, Inc. on permanently revegetated areas during the summer of 1991. Monitoring areas included two, four, and seven year old reclamation, the grazed Wadge Pasture area, and native reference areas. The 1991 annual Revegetation monitoring report is included wi [h this submittal as a separate document (ESCO, 1992). Grazing. Livestock were grazed from August 3 through September 21, 1991 in the cadge Pasture area of Seneca 11 Mine (Permit C•BO-005, Appendix 13-4, Map 1). A total of 275 long yearlings were grazed during [he 50 day period. Assuming each long yearling requires 648 pounds of forage per month, a total of 297,594 pounds of forage were consumed (648 pounds of forage x 1.67 months x 275 yearlings). The 1991 forage production in [he Yadge Pasture as determined from 1991 revegetation monitoring, totaled 902,436 pounds (314 acres x 2874 pounds per acre). The 1991 estimated forage utilization by livestock in the (ladge pasture was 33 percent (297,594 pounds of forage consumed/902,436 pounds of available forage). The configuration of the wadge Pasture was changed in 1991 due to the advance of the lower Wolf Creek Pit and other operational considerations. The new pasture configuration increased the acreage from 302 acres to 314 acres. The change in fence lines is illustrated on Exhibit 91.4. Chronological Historv of Revegetation. All areas revegetated prior [0 1991 at the Seneca II Mine are listed by field number in Table b and shown on Exhibit 90.3, Chronological History of Revege[ati on Activities of the 1990 Annual Reclamation Report (PCC, 1991). Exhibit 91.4 of this report should be compared with Exhibit 90.3 to show the current areal • extent of all permanently revegetated lands. 13