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Home My WebLink About116175A (05-31-16) GeoHazReview signed.pdf H-Ptivorth•Pawl ik Georeclinical,Irk GeSeti-4 020 County RRoad154 ech x50nSprings,Colorado 81601 Phone:e:97 970-945 7988 HEPWORTH-PAWLAK GEOTECHNICAL Fax 970-945-8454 email.hrgeo@Ohpgeotcch.com May 31, 2016 Kissane Construction LLC Attn: Jeff Kissane P. O. Box 1752 Gypsum, Colorado 81637 jeffkissane@gmail.com Job No. 116 I75A Subject: Review of Potential Geologic Hazards, Crow Residence, Lot 4, Vail Village Seventh Filing, 1250 Ptarmigan Road, Vail, Colorado Dear Jeff: As requested, Hepworth-Pawlak Geotechnical has reviewed the potential geologic hazards that could impact the site. Our findings are presented in this report. The services were performed in general accordance with our agreement for professional engineering services to Kissane Construction, LLC dated May 16, 2016. Background Information: The residence is planned to be remodeled. As part of the remodeling, existing timber site retaining walls will be replaced. We understand the new retaining walls are not planned to change the existing site grading. The geologic hazards review of the site is needed for the submittal to the Town of Vail. Site Conditions: The residence is a three story structure reportedly constructed in about 1979. The residence was constructed on relatively flat graded terrain near the base of mountainside terrain near the intersection of Ptarmigan Road and Vail Valley Drive. The mountainside terrain to the south of the residence is steep to very steep and forms the south valley side of Gore Creek. The grading for the site development included several low retaining walls on upslope sides of the residence and the driveway as grade change in to the previously moderately steep terrain. There are small to medium sized aspen and scattered evergreen trees on the slope behind the residence. Bedrock of the Mintum Formation outcrops on the very steep mountainside slope areas above the residence. Geologic Hazards Review: Potential major geologic hazards that could impact the site consist of rockfall, debris avalanche and snow avalanche influence zone according to the Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468-1989 Kissane Construction LLC May 31, 2016 Page 2 Town of Vail mapping (Town of Vail, 2000a, 2000b, and 2000c). The hazards are noted as high for the debris avalanche potential for most of the lot excluding the extreme northern and northeastern portions, medium severity for rockfall potential, and possible avalanche influence zone. We generally agree with the mapping hazards for the lot. Debris avalanches typically occur due to saturated surface soils from rapid snowmelt sometimes associated with heavy rainfall, and are not common in the Vail area but do occur. The rockfall risk is due to the bedrock outcrops above the site and are typically not frequent but can damage homes and property when larger rocks fall. The snow avalanche risk is viewed as low. The hazards appear to be an active geologic process at the subject site and in the nearby areas, and should be expected in the future. However, without long term observations, it is not possible to develop a statistical recurrence probability of hazards. We are not aware of recent debris avalanche or rockfall at the site. Although the probability a debris avalanche or rockfall will hit the residence during a reasonable exposure time for the building is likely low, a debris avalanche or rockfall has the potential to cause major damage to the building with a risk of harm to the building occupants. If this risk is not acceptable to the owner, then the feasibility of risk mitigation should be evaluated. Rockfall in the area has been mitigated with rockfall catching barriers and debris avalanche by soil berms which may or may not be feasible at the subject site due to the topography and limited area on the lot behind the residence. The mitigation would Iikely need to extend beyond the property limits and encompass several adjacent lots which are also subject to similar potential geologic hazards. If the owner does not plan to mitigate the potential geologic hazards and accepts the risk they may pose on the residence, this should be feasible based on Town of Vail code provided the grading plan of proposed improvements does not increase the existing rockfall, debris avalanche or avalanche hazards to adjacent properties including public streets, right-of-ways and easement. Limitations: This review was conducted according to generally accepted geotechnical engineering principles and practices in this area, at this time. We make no warranty either express or implied. The information presented in this report is based on the geologic hazards mapping by others,our field observations, and our experience in the area. We are not responsible for technical interpretation of our findings by others. Job No. 116 175A Gecgtech Kissane Construction LLC May 31, 2016 Page 3 If you have any questions or need further assistance, please call our office. Sincerely, HEPWORTH—PAWLAK GEOTECHNICAL, INC. . ., .. 4 1. At 4,s / T David A. Young, P.m ", 32.. • l '' Rev by: SLP �, °,1., .' �% �*`•, DAY/ksw REFERENCES Town of Vail, 2000a. Official Rocs(fall Hazard Map, Town of Vail. Prepared by the Town of Vail, Vail, Colorado (Adopted by the Town Council on October 17, 2000). Town of Vail, 2000b. Official Debris Flow Hazard Map, Town of Vail. Prepared by the Town of Vail, Vail, Colorado (Adopted by the Town Council on October 17, 2000). Town of Vail, 2000c. Official Avalanche Hazard Map, Town of Vail. Prepared by the Town of Vail, Vail, Colorado (Adopted by the Town Council on October 17, 2000). Job Na 116 I75A �Hp Ge tech