PERMFILE53729 - Laserfiche WebLink

Home Browse Search

ENGINEERING $OLUTIONS FROM THE GROUND DOWN MEMORANDUM 10 May 2004 File No. 103070-000 TO: JCB Engineering, LLC Attention: John Vazquez C: Banks & Gesso ~~~~ Maureen Jacoby 1Il/// FROM: Lyman Henn Inc. Jay Davenport SUBJECT: Addendum to Slope Stability Analysis for Town of Windsor Water Pipeline dated 26 March 2004 Raindance Sand and Gravel Mine Windsor, Colorado Lyman Henn was requested to evaluate the slope stability for three additional structures that are within 200 feet of the proposed mining limits of the subject gravel pit. These structures are the Poudre Trail (south and west of mining areas), the Eaton Ditch (west of mining), and the Everitt Barn (just north of the "west mine" area). Since the general slope configurations during and after reclamation of the of the mined pit area aze similar to the configuration used in evaluating the slope stability for the Windsor Water Pipeline (Lyman Henn report dated 26 March 2004), [he model used and the results of that evaluation are used as the basis for the evaluation of these three additional structures. Based on the DMG Exhibit C-3 and our understanding that reclamation slopes will be constructed at no steeper than 3:1 (horizontal:vertical), Lyman Henn prepazed slope profiles of the reclaimed slopes for each structure as shown in Figure 1. The Poudre River Trail represents the worst case scenario of the three additional structures, with a 20-ft offset from crest of the grading excavation and 72 ft offset from the reclaimed mining slope. Therefore a slope stability analysis of the slope for a potential failure at the uppermost slope crest was used to evaluate the stability of the slope for the three structures. An analysis for the worst case condition was performed, which is the active mining slope as described in the original Lyman Henn report dated 26 March 2004. The result of this analysis suggests that approximately a factor of safety of approximately 1.9 can be expected for the stability of the slope at the point located at the uppermost crest of the slope (see attached model output). Since the three structures are actually located further back from the uppermost crest as analyzed, it can be expected the factor of safety of the slope will be greater at the closest part of the structures than from the critical case used for the analysis. Applying the results of this analysis, the proposed excavation slope and reservoir slope configurations appear to be stable in terms of protecting the Everitt Bam, the Eaton Ditch, and the Poudre Trail. G'.NROJECTS\103070 Whiting EarznUt. Records aad CotttspotWetue\R.1 t Repotts\Addendum to Report doc i I Q 16th 5u-eec, Suite 94G - Demec ~O 802Q2-S"LO"t -lei; 3Q3.534, i Q^ -~ c~;:: 30:;. X34, i'?7 -- v:w~n•.! vnlanHena.ccm Geotechnical,7unre6rtg oaa`Cuictrucr;on _er-vn:?s