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• The monuments currently in place for subsidence monitoring are 7/8-inch rebar driven approximately 18 inches or to refusal into the ground. These monuments have provided data of sufficient accuracy to determine the critical subsidence parameters for the room-and-pillar panels at the Roadside South Mine. Abel (1982, p. 6) states that, "Thin sandy soils, i.e. soils which have high permeabilities, which rapidly drain away rainwater or snow melt and are not frost susceptible can probably be successfully instrumented with steel bar monuments driven directly into the ground, to refusal." Since the sandy soils of the relatively thick colluvium overlying the strata above the mine meet this condition, the existing monuments should be adequate for continued subsidence monitoring. The Palisade pipelines will be monitored on a regular basis during mining below the areas defined previously to insure that subsidence effects, which could be potentially damaging to the pipelines, are detected early enough to prevent such damage. • Subsidence monitoring over the Roadside North and South Mines will primarily consist of a visual surface inspection in the spring and fall. The inspection will include areas over the next years' mining projections and over the past two years of actual mining. The inspection will include surface structures or features to be undermined and evidence of subsidence. The features will be documented and photographed. Subsidence evidence will be measured, recorded, mapped, and photographed. The results of these semi-annual inspections will be submitted to the Division in an annual subsidence report by December 31 of each year. For mining under Coal Creek and Jerry Creek, two monuments will be installed adjacent to Coal Creek and three monuments will be installed along Jerry Creek. These monuments will be surveyed immediately prior to undermining and twice a year for two years subsequent to undermining. The location of these monuments is shown on the Hydrologic monitoring map, Exhibit 56, Tab Section 18. • 20-9 (Rev. 01!01)