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aTETRATECH <br />April 27, 2012 <br />Mr. Mike Refer <br />Aggregate Industries <br />1701 Cole Blvd., Suite 100 <br />Golden, CO 80401 <br />Re: Technical Revision Request for Hazeltine Mine, Mine # M-2004-031, Adams <br />County, Colorado; Tetra Tech Job No. 133-23514-12003 <br />Aggregate Industries - WCR Inc. is in receipt of Mineral Program Inspection Report, dated <br />November 4, 2011 for the Hazeltine Mine located in Adams County, Colorado. The mine permit <br />number is M-2004-031. The inspection report includes an order for corrective action to relieve a <br />water mounding situation impacting an adjacent landowner ("Subject Property"). <br />Tetra Tech was engaged by Aggregate Industries to evaluate alternatives to relieve the water <br />mounding. A review of the site conditions indicated that the ponded water is likely due to the <br />combination mounded groundwater on the upgradient side of the slurry wall and discharges into <br />the Bull Seep from the Fulton Ditch. The solution includes a pump station, and adjusting water <br />management practices at the Fulton Ditch turnout to the Bull Seep to lower the surface water <br />level. <br />Aggregate Industries reconfigured the Bull Seep under an existing US Army Corps of Engineers <br />section 404 permit. One requirement of this permit was the creation of approximately 6 acres of <br />wetlands along the Bull Seep alignment just north of the subject property. Previously, the Bull <br />Seep was rerouted north of the site on land now owned and operated by the Denver Water Board <br />(DWB). <br />Topography of the project area was obtained by Aggregate Industries in January 2012. Review <br />of the topographic data shows that the minimum elevation on the subject property is at <br />approximately elevation 5037 to 5038. <br />The alternative for lowering the water surface on the subject property is a pump station with a <br />force main discharging north of the site into First Creek. The alignment of the force main and <br />electric service would be across DWB property. Two meetings have been conducted with <br />Messrs Greg Gulley and John Bambci of DWB. DWB has verbally agreed to the alignment and <br />configuration that is presented on the attached drawings. Formal approval will require the <br />granting of revocable utility easements with Denver Water for the force main and electric <br />service. <br />The pump station will include an Agridrain level control device on the upstream end to control <br />the surface water elevation. The Agridrain is planned to control water surface elevation between <br />1900 S. Sunset street, Suite 1 F Wngmont; CO 80501 <br />T-1 303 772 SM t k 303.7727039 <br />www.tatratech.com <br />