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2006-04-03_REVISION - M1977526
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2006-04-03_REVISION - M1977526
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Last modified
6/15/2021 5:35:53 PM
Creation date
11/21/2007 3:52:34 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1977526
IBM Index Class Name
Revision
Doc Date
4/3/2006
Doc Name
Submittal of Amendment
From
Environment Inc
To
DMG
Type & Sequence
AM2
Media Type
D
Archive
No
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4 <br />Mr. Ken Lambrecht <br />January 17, 2006 <br />Page 2 <br />Our analysis involved varying the offset distance from the highwall to the slurry wall and <br />evaluating the factor of safety and failure surface orientation at each offset distance. Shallow <br />surfaces (infinite slope or "raveling failures") were excluded from the analysis, as they should <br />not impact the slurry wall. <br />We evaluated two types of reclaimed slopes. The first type consists of mining up to a 3:1 <br />(horizontal to vertical) slope and leaving the native soils in-place as the final reclamation slope. <br />The second type of slope evaluated consists of mining a steep highwall (0.5:1) and placing <br />overburden soils compacted to 95 percent of the maximum dry density per ASTM D-698. This <br />compacted slope was evaluated with a 3:1 slope. <br />Four different cross-sections were modeled as bedrock depth vanes across the site. Bedrock <br />depths were based upon borings drilled during August of 2005. Cross-sections were analyzed <br />with bedrock depths of 13.5, 40, and 62 feet. <br />A fourth cross-section was modeled with the deep bedrock stratigraphy. This fourth section was <br />modeled using a weathered_bedrock layer immediately underlying the sand and gravel layer. <br />The highwall in each of these cross-sections was modeled with a slope of 0.5:1 (horizontal to <br />vertical) typical for gravel mines in this area. The soil profile analyzed consisted of 0.5 feet to <br />4.5 feet of overburden clays overlying approximately 15 to 60 feet of sand and gravel on top of <br />claystone bedrock. . <br />A long-term stability analysis was conducted modeling the final reclaimed slope which will <br />include a 3:1 (horizontal to vertical) compacted clay reservoir liner constructed interior to the <br />mine highwall. Both a compacted clay liner and a mined slope of 3:1 were analyzed. <br />Additionally, for the purposes of determining appropriate setback distance from the existing <br />structures (utilities and right-of--way), an analysis was performed using the Division of Minerals <br />and Geology (DMG) parameters for sites where laboratory testing is absent. These pazameters <br />are given below on Table 2: <br />Table 2: DMG Model Parameters <br />Soil type ~' (degrees) c' (psn y (pct <br />Overburden 28 50 114 <br />Gravel 35 0 130 <br />Weathered Bedrock 14 0 124 <br />Bedrock 28 100 124 I <br />Co acted Cla Liner 24 100 119 <br />
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