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~ iii iiiiiiiiuiii iit ~ <br />DATE: January 30, 1998 <br />TO: File No. M-74-O15 <br />FROM: Allen Sorenson `"~ I <br />RE: Preapplication Meeting for a Large Pit Expansion <br />Attendees: Mike Hart -consultant to Western Mobile <br />Carl Mount, Gregg Squire, Allen Sorenson - DMG <br />Mr. Hart distributed an Executive Summary describing Western Mobiles proposal to expand gravel <br />mining operations along the St. Vrain Creek east of Lyons in Boulder County. <br />The following issues were discussed as being critical to the Division's review of the permit or <br />amendment application to be submitted. <br />Spiranthes Diluvialis and Preble's Mouse surveys - Mr. Hart stated that these surveys would be <br />conducted sequentially in advance of mining. <br />Grade control structures to prevent re-routing of St. Vrain Creek during a flood. <br />To be installed at flood flow inlet and outlet points of the mined areas. <br />Probably take the form of buried rock walls or similar. <br />Prevent capture of the stream during one percent annual probability flood. <br />Orient topsoil and overburden piles with the direction of flood flows. Locate s'.ockpiles in low <br />energy flood areas, Revegetate any topsoil piles that will remain for more than one growing <br />season. <br />Irrigate any cottonwoods that may experience loss of subirrigation due to pit df:watering. <br />Bonding for slurry wall installation and pit lining. <br />If slurry wall is to be installed after mining, a bond must be in place to cover the cost of <br />the slurry wall installation. Costs are about $4.00 to $8.00 per sq. ft. <br />If slurry wall is to be installed prior to mining, the operator may either post bond to <br />cover the full cost of installation, to be released once it can be demonstrated that the <br />installation adequately prevents seepage, or, the operator may provide ~ detailed slurry <br />wall installation and construction quality assurance plan, to be approved and enforced <br />by the Division, then the bond to be posted would be some percentage (25%) of the <br />total slurry wall installation cos[. <br />Demonstration of compliance with gravel pit well permit, substitute supply pl:m, and/or plan <br />for augmentation. <br />