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SOUTHWEST MINING DISTRICT <br />TCC did not establish further subsidence monuments, except as described below. The ongoing subsidence <br />monitoring work has demonstrated that TCC's subsidence predictions are conservative and provided an acceptable <br />description of expected subsidence. Any further subsidence monitoring work would just be further verification of <br />these predictions and is not warranted. <br />In reference to Routt County Road 27, TCC installed subsidence monuments along the road at the gate roads and <br />center of the panels. These monuments were 6" to 12" spikes driven in the ground in the shoulder of the road. The <br />monuments were monitored on a quarterly frequency while active mining occurred. The panel has been mined out <br />and two monitoring sessions showed no further movement, however, monitoring was discontinued and the <br />monuments were removed. <br />When the road was undermined signs were placed 1500 feet before entry into the section of road that was subsided. <br />The signs were large billboard type signs, approximately 4' x 8', and lettered with "Begin Subsidence Zone and <br />heaving Subsidence Zone". These signs were placed so they are visible for each travel direction. In addition to the <br />entrence signs, warning signs were placed through the subsided area and read "Rough Road, Drive With Care". <br />Subsidence has ended and final repair completed, therefore the signs were removed from the site. <br />Additionally, during active mining the road was inspected daily for evidence of surface cracking. The cracks were <br />repaired if the cracks extend into the road base. Potholes or other larger features were repa'ved with a suitable patch. <br />The drainage ditches along the side of road were checked and no repairs were necessary to maintain road drainage. <br />A mitigation plan using a combination of ditches, berms, and permanent relocation of a portion of Routt County <br />Road # 27 was developed based on the CRSP model analysis carried out by SubTerra to contain any rocks that may <br />sluff off of the sandstone cliff and impact on the road or other man-made structures. <br />In developing the mitigation plan, the entire sandstone cliff that overlays the longwall mining area was mapped and <br />divided into fourteen (14) zones of similar morphological conditions. CRSP models were developed based on <br />selected sections of each zone. The CRSP model results were used to develop the hazard contours shown on <br />drawing 2 Exhibit 7F. A plan was then developed utilizing ditches, berms, and permanent road relocation for those <br />areas where the road or man-made structures were within the 0% hazard contour that would prevent the passage of <br />any blocks that may fall from the cliff in a worst case situation. This plan is described in detail in Exhibit 7F. A 10 <br />foot deep, v-bottomed trench and a 10 foot high constructed berm located adjacent to the road was utilized in zones <br />1 and 3. A 20 foot high berm constructed on the existing alignment of County Road 27 was utilized in zone 2. A <br />10 foot deep "v" trench and 10 foot high berm located with the lower toe of the berm approximately 30 feet north <br />of the road was used in zones 4 and 5. No mitigation was required in zones 6 through 9 to protect the road, <br />however a 10 foot deep "v" trench and a 10 foot high berm was used to protect the water tanks located on the slope. <br />A ]0 foot deep "v" trench and 10 foot high berm was used in zones 10 and 11. No mitigation measures were <br />required in zones 12 through 14. <br />A portion of Routt County Road # 27 is located in zones 1 through 3 was permanently relocated. The relocation of <br />the road was discussed with the Routt County Road Departrnent, and was conswcted according to county <br />specifications. <br />Prior to construction of the trenches and berms, topsoil was stockpiled adjacent to the construction zones within the <br />area designated for disturbance on Exhibit 7F, Sheet 2. After construction was completed, topsoil was redistributed <br />over the disturbed areas and the areas was reseeded with the rangeland see mix. Trenches were graded to provide <br />positive drainage. Erosion control measures included the installation of rock filters at the <br />~ t 2 4 ~~~~~ <br />;~~ <br />,. <br />Permit Renewal No. 3 2.05-187 12/l0/98 <br />