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HomeMy WebLinkAboutSlope Study - 2005c&Ftecrt HEPWORTH . PAWLAK GEOTECHNICAL i.i,-,., enrire:. t 6" 2oo5 ,:leei' Custorn Remodeling. I-l.C r\tn: 3oh Zeeh P.Cl. Box 1997 Avon. Colorado 81620 Subie:t. .lob Flo. 404 358 Review of Boulder Slope Stability. -1828 Bridge Road. Lot 10. Bighom Subdivision Second Addition. Vail- Colotado De.,l.ivil. Zc-e b: As requested, a representative of Hepworth-Pau'lak Geotechnical. inc. met *,tth you at the subject site on November 4. 2005 to observe the boulder slope behind the residerce ibr stabiliti' considerations. The findings of our obsen aliorrs are presented in this reirort. S.'e previously observed the building excavation for fbunclation bearing conditioris and presented our findings in a report dated October 21. 2004, JoF,No. 401 3-SE. f i;e c.rrc:nt ;"er isr'" was performed as a supplement to our agreerrrent ibr proibssional ser"'iieg rlith 1'ou daied October I l. 2004. Eristing Conditions: We understand that the f'own of !'ajl i., r:questing a r"-'''ie '.i of the boulCer slope as a condition of the Certificate of C)ccuptmcr.. l-he upirill slope is essentially the same as that observed in October 2004 except that stackeci boulder rvalls have been built to retain the uphill part ofthe cut slope. The large boulder about 20 feet in size that is located about 3 feet off of the south building wall is incorporated into the stacked boulder walls. We understand that the large boulder was too massive to be moved and the building footprint had to be moved 2 feet north to avoid the bouider. The boulder walls are constructed in two tiers,, roughly each 5 to 6 f'eet high and stepped L'''ack at about an effective slope of I to l. The boulders are angular shaped and rve understand ihat they- .,,,eie piaccd on the i-iatural ground. A shallc-"v s';;.iic is cut iiito thc hill:idc abcul iC f:ct behind the top of the boulder wall that drains to the east and west around the resrdence. Design Conditions: The site plan for the residence by Steven James Riden dated March 7. 2005 shovvs stacked boulder walls stepped up the hillside behind the residence. similar to the constructed walls. The existing large rock is also shou'n on the plan. The uphill foundation wall is about l8 feet deep at the backside. The original cu1 depth reported by us was about 20 feet so most ofthe uphill excavation has been backfilled and is supported by the building foundation. We understand that the backfili consists maini;" of drain gravel that was placed last winter and that there has heen no indicettion o1'fourdation wall movement The excavation was dry at the time of our o'bservation in Octobe:'?0()4 and we are not aware of seepage in the uphill cut or in the hilisicle abrrve ihe residenc.:. Conclusions and Recommendations: The stacked boulder walls and large boulder appear adequate to support the uphill cut slope irt the current dry condition. In our Glenwcrrrcl Springs 970-945-7988 o Parker l0l-841-7119. Ct,loradoSprings 719-633-5567 llepr,"'r'rth'['au'1ak CcL,tcchnical, lnc. P (). [)rrrtcr lil87 Silvcrrh,rrnc, (irlLrrl.l,r 80498 Ph,nc: 97Ll-468- I989 Frrxr 970-4(rh-5691 cmrtil: hfr:c,r4(Dhp!s()tech.c(]rr (-.. (' .-r tt\_ r,.,,2 fy rrl Y-i Zeeb Custom Remodelins. LLC November 16.2005 Page2 opinion. it appears unlikely that groundwater conditions sufficient to destabilize the boulder wall slope wiil der,elop considering the obsen'ed dr,v excavation slopes and hillside. The gravel foundation wall backfill that connects to the foundation drain should be adequate to collect seasonal perched water or subsurface seepage from spring runoff. If seepage was to develop and there was boulder undermining, the potential for the boulder to impact the residence, in our opinion. is low'and the undermining could be repaired such as w-ith grouting. The slope stability condition should be monitored on a regular basis and at least during spring thaw'when seepage is most likel,v to develop. If there is any indication of slope movement. it should be brought to the attention of a professional. The conclusions and recommendations submitted in this letter are based on our obsen'ation of the soils exposed within the lbundation excavation and the current constructed boulder walls. Variations in the subsurface conditions below the hillside could increase the risk of movement. We should be advised of any differences in the site and subsurface conditions to those presented in this report for possible changes to our conclusions and recommendations. If you have any questions or need further assistance, please call our office. Sincerely, HEPWORTH - PAWLAK GEOTECHNICAL. INC. Steven L. Pawlak, P Rev. by: RJU SLPtksw nk |jt"d oi ."$:.:s L,'. sj F} Job No. 404 358 c&ttecrr