Laserfiche WebLink
T E T RA T E C H 1900 S.Sunset Street,Suite I-E Longmont,CO 80501 <br /> Tel:303.772.5282 Fax:303.772-7039 <br /> MEMORANDUM <br /> TO: Martin Marietta Materials <br /> From: Gary Linden,R.G. <br /> Subject: Design Memorandum,Duckworth Mine, Weld County,Colorado; Project No. 133- <br /> 24097-14003 <br /> Date: February 27, 2014 <br /> This memorandum has been prepared to summarize investigations,analyses,and design for the <br /> Duckworth Mine Slope Liner. The mine is located on the north side of Weld County Road(WCR)20.5 <br /> approximately 'A mile west of the intersection of WCR 20.5 and WCR 7. The site is more particularly <br /> described as located in part of the northeast quarter of Section 16,Township 2 North,Range 68 West of <br /> the 6t'Principal Meridian. <br /> Site Description and Background <br /> Martin Marietta Materials,Inc. (MMM)currently is mining sand and gravel at the Duckworth Mine. <br /> Depending on the amount of suitable material,MMM plans to reclaim all or part of the Duckworth Mine <br /> as a below grade lined reservoir meeting seepage requirements of the State Engineer of Colorado. <br /> MMM contracted with Tetra Tech to design a below grade reservoir slope liner per the scope of work <br /> outlined in our proposal of July 19,2013. MMM provided Tetra Tech the site mine and reclamation <br /> plans. In addition,MMM provided exploratory boring and test pit data collected during due diligence <br /> investigations. Tetra Tech has produced reservoir slope liner plans and specifications for the project. The <br /> purpose of this memorandum is to summarize our investigations and analyses used in the design of the <br /> project. <br /> Regional geologic mapping(Colton, 1978)indicates the surficial deposits at the site are the Piney Creek <br /> and Post Piney Creek Alluvium. The regional mapping indicates outcrops of the Upper Transition <br /> Member of the Pierre Shale and the Fox Hills Sandstone are mapped in the area indicating that one or <br /> both types of bedrock may underlie the alluvium. <br /> Idaho Creek flows through the approximate center of the site dividing the site into two mine cells: Phase I <br /> on the east and Phase 11 on the west. Phase I of the mining is complete. Phase 11 mining has commenced <br /> on the north part of the cell. A gas well is located north of the Phase I cell. A yet to be constructed gas <br /> line will traverse the north side of the Phase II cell. The Smith and Emmons Ditch lies immediately west <br /> of Phase II. <br /> Two types of overburden have been broadly identified at the site. The first overburden type is a more <br /> plastic,clayey material that tends to range from brown to black. The second overburden type tends to be <br /> less plastic and generally appears to have fewer fine grained materials passing the number 200 sieve(silt <br /> and clay). This second type tends to be more orange in appearance. When stripping the overburden, <br /> Page 1 of 5 <br />