Laserfiche WebLink
I� <br />March 31, 2015 amec <br />foster <br />wheeler <br />Mr. Chris Hanks <br />Chief Environmental Coordinator <br />Cripple Creek & Victor Gold Mining Company <br />100 North 3'd Street <br />Post Office Box 191 <br />Victor, Colorado 80860 <br />Re: Cripple Creek & Victor Mining, Co. Cresson Project M-1980-244; Follow-up Review <br />Comments for Quality Assurance Monitoring & Test Results Final Report for Squaw <br />Gulch VLF Pregnant Solution Storage Area Underdrain Ponds <br />Dear: Mr. Hanks, <br />Amec Foster Wheeler Environment & Infrastructure, Inc.(Amec Foster Wheeler) has prepared <br />this letter to address the properties of the proposed liner to be placed over the concrete in the <br />underdrain ponds. This provides additional response to a comment from the Colorado Division of <br />Reclamation Mining and Safety (DRMS) in their letter dated February 3, 2015. <br />Background: <br />Concrete testing was performed during the placement of the concrete for underdrain ponds. <br />Three tests failed the air entrainment requirements and two failed the minimum slump <br />requirements (Project Technical Specifications Section 03300.0 Cast -in -Place Concrete). Air <br />Entrainment and Slump Testing are not necessarily indicative of bad concrete; air is added to <br />concrete to increase durability during freezing and thawing conditions and slump indicated the <br />water cement ratio. All concrete testing performed at the underdrain ponds met or exceeded the <br />required minimum strength. Cripple Creek & Victor has proposed to install a liner system to <br />satisfy any concerns DRMS may have regarding the failed concrete tests. The liner system will <br />consist of 80 -mil double -sided Microspike® LLDPE geomembrane manufactured by Agru <br />America, Inc. overlying geosynthetic clay liner (GCL). <br />Underdrain Pond Liner System LLDPE Properties <br />LLDPE geomembrane was selected for the liner system due to its flexibility and excellent tensile <br />elongation properties. As indicated on the attached product data sheet, 80 -mil LLDPE <br />Microspike geomembrane has a minimum average roll value (MARV) of 400 percent elongation <br />at break using a gage length of 2.0 inches. Due to its elongation properties, LLDPE <br />geomembrane is often selected for landfill cover systems or sites with soft foundations where <br />significant settlement is anticipated. <br />Amec Foster Wheeler <br />Environment & Infrastructure, Inc. <br />2000 South Colorado Blvd., Suite 2-1000 <br />Denver, CO 80222 <br />Tel: (303) 935-6505 <br />Fax: (303) 935-6575 <br />amecfw.com <br />