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Precipitation Data Precipitation data for the environs of the Nucla Mine and proposed Nucla East mining area from January 1980 through September 1987 are presented in Table 1. Average annual precipitation is approximately 14 inches. Except for 1980, precipitation for the period-of -record has been above normal, especially during 1983, 1984, 1985, and 1986 when average annual precipitation was exceeded by at least four inches. However, because these data are collected at stations more than 10 miles away (Norwood and Uravan) from the Nucla and Nucla East mining areas and are thus not site-specif ic, it is important that these data should only be used to assess regional precipitation trends. Surface Water Operational Monitoring Program - Nucla Mine. Monitoring activities conducted at the Nucla Mine during 1987 were consistent with the operational monitoring program outlined in the revised Nucla Permit Application Package and the 1986 Annual Hydrologic Report for Nucla. The basic program is outlined in Appendix A, (Attachment A) Reduction of Monitoring for the Nucla Strip, and is further detailed in Table 2. Monitoring site locations are presented on Exhibit 1. Several minor modifications of monitoring points at NPDES monitoring sites were made during the 1987 water year, and the following discussion provides explanations of these modifications. As a result of construction activities (approved by CMLRD) at several of the existing sedimentation ponds (001, 002, 004, 005, and 006) during 1987, discharge monitoring for compliance with the Nucla NPDES permit (CO-0000213) has keen altered for each site with regard to the monitoring point below each pond. The resultant change in monitoring points at Ponds 002, 004, 005 and 006 simply involves present and future monitoring for flow and quality at the spillway outlet (drop inlet pipe) constructed at each pond. Horvever, because of requirements by CMLRD for continuous monitoring of flow at the 001 pond (NPDES 001), Peabody reestablished the 001 monitoring point just below the newly constructed spillway outlet shortly after construction activities were completed. The reestablished point for the NPDES 001 monitoring site consists of a sharp-crested 90° v-notch weir continuously measured by a Steven's Type-F water level recorder. No changes were made in the frequency and parameters monitored during the 1987 water year at each of these modified monitoring points (NPDES 001, 002, 004, 005, and 006), and future monitoring will be consistent with the existing NPDES permit monitoring requirements. 2