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REP41984
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REP41984
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Entry Properties
Last modified
8/25/2016 12:43:48 AM
Creation date
11/27/2007 9:10:24 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1977342
IBM Index Class Name
Report
Doc Date
12/5/1995
Doc Name
TRANSMITTAL AS BUILT DRAWING & DOCUMENTATION HENDERSON MINE SEDIMENTATION POND 1.2
From
TITAN ENVIRONMENTAL
To
HENDERSON MINE
Media Type
D
Archive
No
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<br />TEC conducted periodic inspections of the excavation activities, pond berm construction, <br />cushion sand placement, inlet/outlet construction and pond liner installation. <br />During the pond excavation the following subsurface materials were encountered: <br />• Surface to 5 feet: Dry backfill materials consisting of gravels, sands, large rocks and <br />timber; <br />• 5 to IS feet: Wet to moist organic, clayey, gravelly soils. <br />Soils collected from the 5 to IS foot interval were tested for maximum density using the <br />Standard Proctor Test, and for shear strength using Consolidate-Undrained triaxial compression <br />tests. These test results are attached. The attached slope stability calculations show that the pond <br />slopes of 1.5:1 are stable for the soils encountered at the site. <br />Ground water was encountered during pond excavation in two primary zones. A perched zone <br />was encountered at the backfill/clay soil interface. Ground water seeps associated with the <br />perched zone were of limited volume and short-duration. Ground water was also ero:ountered at <br />the bottom of the pond excavation as minor seeps. The ground water in the excavation was <br />collected and removed using construction sumps (trenches). Once the ground water was <br />removed, the sub-base materials were firm and provided an adequate foundation for cushion sand <br />placement. <br />A 6-inch minimum cushion sand was placed on the bottom and sides of the pond. 7"he purpose <br />of the sand was to provide a firm sub-base for the HDPE pond liner. The sand was placed using <br />an excavator and was compacted using a heavy steel roller. The resulting sand base was firm and <br />unyielding and was deemed acceptable by the liner installation company (Colorado Lining). The <br />east side of the pond bottom showed some signs of softness; however, the bottom became firm <br />with additional sand. <br />Pond berms were constructed by compacting (to a minimum 95% Proctor compaction) native <br />soils in 12 to 18-inch lifts. The berms were compacted using construction equipment followed <br />by a heavy steel roller. Compaction of the berm soils was verified by in-situ density field tests. <br />The attached documentation includes the field results. As shown, the field tests show that all of <br />the soil densities exceeded 95% of the Proctor maximum density. In some cases, the densities <br />exceeded 100% of the Proctor compaction. Densities exceeding 100% were likely due to the <br />presence of rocks within the berm soils. As constructed, the pond berms are sound and will <br />provide a film structure for the pond liner anchor. <br />The 40-mil HDPE pond liner was installec~.,by Colorado Lining Company wish periodic <br />inspections by TEC personnel. TEC also provided a final visual inspection of the pond liner on <br />November 30, 1995. The pond litter was installed using industry standard procedures. All welds <br />were air tested. The QA/QC sheets provided by Colorado Lining are included in the attached <br />documentation. In addition to air tests, welds and seams were "rip" tested by the 4ining <br />=F~° ° Environmental <br />
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