PERMFILE111467 - Laserfiche WebLink

Home Browse Search

0 • consistent with the results of this site specific investigation. The site conditions found are considered generally favorable for construction of the proposed sedimentation pond embankments. At most embankment locations, clayey sand or clay soils are available to construct the embankment. The pond embankment heights are up 10 feet. We performed stability analysis for several conditions on a representative model of a 10- foot high embankment. Factors of safety in excess of 1.3 were found for the conditions modeled. The lowest calculated value was 1.7. Due to the relatively low height of permanent water storage, seepage and piping below the embankment are not considered to be significant concerns. Construction recommendations including suitable and unsuitable materials types, key-way size, and placement and compaction recommendations are presented on Fig. 7. Monitoring and inspection should be performed by qualified individuals as required by State regulations. DESIGN AND CONSTRUCTION RECOMMENDATIONS Following are initial recommendations for geotechnical related design and • construction aspects of the spoil fills. Excess Spoil Fill Configuration The proposed slope configuration For "major" Fills (No. 4 through 9) is 2.5:1 (H:V) slope with 20-foot wide benches at approximate 40-foot vertical spacing. This results in an average overall slope on the order of 3:1 (H:V). Our analysis indicates the configuration produces a fill with satisfactory stability. Variations in the face configuration (if desired) should be possible. We do not recommend steepening of the face. However, if construction results in one or more intervals with slopes slightly exceeding 2.5:1, we do not believe stability will be significantly reduced. Our experience indicates interbench slopes as steep at 2.2:1 can provide stable fills. • LORENCITO COAL COMPANY, LLC LORENCITO SURFACE MINE - PHA6E I CTLR 32, 617 12