|
CIVIL RES'DURCES,LLC
<br /> ENGINEERS S, PLANNERS
<br /> January 5,2006
<br /> Mr.Jeff Gregg,Resources Manager
<br /> Hall-Irwin Corporation
<br /> 301 Centennial Drive
<br /> Milliken,Colorado 80543
<br /> Re: Stability Analysis for Parker/Dersham Sand and Gravel Resource
<br /> Dear Mr.Gregg:
<br /> This letter has been prepared to address the Mine Land Reclamation Board(MLRB)Construction Materials Rule 6,
<br /> Section 4,Subsection 19, Exhibit S-Permanent Man-Made Structures(6.4.19,Exhibit S)for the proposed
<br /> Parker/Dersham aggregate mine Olett is—cr€bes the project and slope stability calculations carried out to evaluate
<br /> the minimum distance betwetpliredge of mining and adjacent structures to avoid damage to the structure.
<br /> "; c- 4.:
<br /> The site is locate •A'okimat do=half
<br /> � � �.�:. �, jle�#ro th8�tlh t�atte`Iver, �1�� �a, ilii j. +arts of east one-half of
<br /> Section 36,To ,i*;i No °an o7 est=d e 6t i�`J' ntk ;<� t,: t : #�•�ter.,,
<br /> ,,,- �? � g°. �' ,tP ,, . � 7h bounded on the
<br /> west by Weld u e' Road,,A:,R) 415,the north 4Y'�1CR 4;!I! . - s.'i laX01 se t:il fi�` i.41681h Ave)and
<br /> on the east b t ting'-:I Inc ' source aggregate ne ones .'v'n' I ;` Ia: pr• =it ,,ercated in Weld
<br /> County,Coloratlg;ap$,owrf`,o--1 *)Ire 1 "` �= €
<br /> Approximately three'tos r� f overb r8en�fs' a'n by afte dee all 4-i';}-•rega,�"I t,The aggregate
<br /> will likely be transported"iia c �a : ' . 6 + � �,,r
<br /> Rut,: ?, :it lanant located _� rth on A,r( Ing Hall-Irwin site.
<br /> Hall-Irwin plans to dewater and dry-mine Phase 1 and 2 at a 0.5:1 (horizontal to ,,,,.!,-. ',.i.pie. Phase 3 will be mined
<br /> after constructing a perimeter soil-bentonite slurry wall that will tie into-the :'4,1''i' urry wall. Phase 3 will mine the
<br /> highwall to a slope no steeper than 3:1 (horizontal to vertical)final grade,as indicated in the DMG permit application.
<br /> This report lists minimum safe setbacks for mining from structures within 200 feet of the permitted mining boundary
<br /> based on stability calculations. Actual setbacks may be greater due to permit limitations,zoning requirements,
<br /> construction issues,agreements with owners,extent of economically mineable aggregate,or other issues.
<br /> GEOLOGY
<br /> The site is located approximately 30 miles east of the foothills of the Colorado Front Range on the western flank of the
<br /> Denver Structural Basin. The basin is a downwarp of sedimentary strata that trends north-northwest,parallel to the
<br /> mountain front. In the project area,the sedimentary beds dip gently eastward toward the axis of the basin east of the
<br /> site. Based on regional geologic mapping(Colton, 1978),the near surface bedrock in the project area is the Paleocene
<br /> and Upper Cretaceous Denver and Arapahoe Formations. The bedrock is overlain by upper Pleistocene and Holocene
<br /> (Quatemary age)gravel deposits and eolian(wind blown)overburden soils. The gravel deposits exist primarily within the
<br /> Broadway Alluvium deposit. The bedrock unit consists mainly of claystone and may contain lenses of siltstone and
<br /> sandstone.
<br /> 451 OAK STREET, SUITE 209 • P.Q. BOX 690 i FREDERICK, CO 80530 • (303) 833-1416 • 1303) 833-2950 - FAX
<br />
|