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The four major sediment ponds, to be constructed during this permit term have been designed to conform to the Colorado Permanent Regulatory Program. Information on the operation and design of the small sediment ponds along the coal transport and storage system was not included in the permit application. Although this information is unnecessary for the small sumps along the corneyor maintenance road and clean coal storage area, the contributing area to ponds in the railroad loop is significant enough to warrant proper sizing, construction, and operation. A check of the largest pond, sedimentation pond #4, shows an available storage area of .92 acre feet. The contributing drainage area is ap- proximately thirty-six acres. Using the standard sediment contribution of 0.1 acre foot for each disturbed acre, the pond is undersized for the 3.6 acre feet of storage required. This also appears to be true for the other three ponds in the loop. Furthermore, the theoretical detention time mentioned on page IY-31 of the permit application seems to have no basis in fact since the only de- watering device provided is a v-shaped overflow notch. The apolicant needs to submit desi n ans o7rds in~tkat--an- can be made of their aPfar+iveness _-LSee "Stipulations" in this section of the TEA). The remainder of this discussion will address the four sediment ponds to be constructed at the D-Portal and Refuse Disposal areas. These are shown on Maps 34 78!79, and 80~ Sediment Storage Volume Sediment contribution was calculated by using the Universal Soil Loss Equation to derive a 3 year sediment yield. All four sedimentation ponds were designed to provide the required storage volume as shown in Illustrations 4 through 7 of the permit application. An error was uncovered, however, in storage calcula- tions for the Refuse Disposal Subarea 1 Pond. Storage curves on Map 78 and in Illustration 4 do not agree, resulting in a required volume of 3.12 acre feet but an available volume of only 2.9 acre feet. This discrepancy of 0.22 acre feet may result in outflow during a 10 year-24 hour event without proper deten- tion time, although this would happen only when the entire available sediment storage volume had been filled. If the applicant cleans the pond when it has reached 60 percent of the design volume, as proposed, there will be no outflow during the design storm. 19