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3. The design of the spillway depicts a riprap thickness of 5 feet on both sides of the crest and the remainder (90 feet) <br />vegetated. The diagram in the Guidelines specifies a riprap thickness of 15 feet along both sides of the crest. <br />Please clarify the width of the riprap to be placed on both sides of the spillway crest to be in conformance with the <br />Guidelines. <br />4. Please state when the stabilization measures will be installed in relation to the sequence of mining and reclamation. <br />5. In the Permit Amendment Application approved by the Division on November 16, 2000, Aggregate Industries <br />states that [he operator will avoid disturbing potential Ute ladies-tresses orchid habitat and mining within 300 feet <br />of the potential Preble's Meadow Jumping Mouse habitat, until [he referenced disqualification's and/or trapping <br />studies are performed. Please inform the Division as [o the status of this study and how mining within 100 feet or <br />200 feet of the South Platte River will impact the Preble's Meadow Jumping Mouse habit and the 300-foot mining <br />offset distance. <br />6. Aggregate Industries states that an area will remain undisturbed and only vegetated if mining is 200 feet from the <br />South Platte River. The specifications noted in the Guidelines states a mining off se[ distance of 400 feet if no <br />river bank protection is proposed. A mining off set distance of 200 fee[ is allowed if the riverbanks are stabilized <br />in accordance with the Master Plan. Please inform the Division how mining within 200 feet of the South Platte <br />River with no river bank protection conforms to the technical guidelines. <br />7. In the February 8, 2002 letter to the Division, the operator requests the spillways for [he ponds be withdrawn from <br />this revision request and possibly be submitted as a future technical revision, The operator contends that <br />construction of the spillways is not a significant revision to the reclamation plan, and may change at the request of <br />Adams County Floodplain Administrator and Urban Drainage. The spillways are a necessary and significant <br />change to the reclamation plan if the operator proposes to mine within 100 feet of the South Platte River as <br />proposed in this revision. This is to ensure that pit slopes adjacent to the South Platte will be stable and non- <br />erosive in the event of a flood. If the spillways are to be withdrawn from the revision, then mining must be no <br />closer than 200 feet [o the South Platte River (where riverbank protection exists or is proposed) or 400 feet (if no <br />riverbank protection is proposed). <br />Please respond to these items prior [o February 22, 2002. If you have any questions, please do not hesitate to call me at <br />303-866943. <br />Sin r ly, <br />Enca Cros y <br />Environmental Protection~i~ ist <br />ce: Carl Mount; DMG (via electronic mail) <br />