HomeMy WebLinkAboutDRB17-0083_GeoHazard report_1492122420.pdf H i_p L F\,1iR 5020 County Road 154
Glenwood Springs, CO 81601
Geotechnical Engineering E Engineering Geology Phone: (970)945-7988
Materials Testing I Environmental Fax: (970)945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Parker,Glenwood Springs,and Silverthome, Colorado
November 30, 2016
Revised April 10, 2017
Kevin Douglas
5075 Ute Lane
Vail, Colorado 81657
kevlarski@hotmail.com
Project No. 16-7-574
Subject: Review of Potential Geologic Hazards, Proposed Addition to Residence, Lot 29,
Vail Meadows Filing No. 1, 5075 Ute Lane, Vail, Colorado
Dear Mr. Douglas:
As requested, the undersigned representative of HP/Kumar observed the project area on
November 19, 20I6 and reviewed the potential geologic hazards that could impact the project
site. Our findings are presented in this report. The services were performed in accordance with
our proposal for professional engineering services to you, dated November 4, 2016.
Background Information: An addition is proposed to be attached to the downhill, northeast
side of the residence. We understand existing grading on the south, north and west sides of the
residence will essentially not be changed as part of the addition. The geologic hazards review is
needed for the submittal to the Town of Vail.
Site Conditions: The existing residence is a one and two story wood frame structure partially
retaining hillside cut on the uphill, west side. The terrain is strongly sloping down to the
northeast toward the Lane and Main Gore Drive. The lot has undergone some grading for the
existing development with possible shallow fill in the downhill part. No active creeks were
observed that flow through the project site or adjacent lots. Vegetation consists of grass with
scattered to moderately thick aspen and evergreen trees. The natural hillside located a few
hundred feet to the west of the residence becomes steep to very steep and is vegetated with thick
aspen and evergreen trees. The lots surrounding the property are all developed with similar
single family residences.
Geologic Hazards Review: Potential major geologic hazards that could impact the project site
consist of debris flow (and snow avalanche limit just above the lot) according to the Town of
Vail mapping (Town of Vail, 2000a, 2000b and 2000c). The hazards are noted as moderate for
the debris flow potential. We generally agree with the mapping hazards for the lot.
Debris flows occur from hillside and mountainside drainages due to heavy rainfall sometimes
associated with snowmelt. Debris flows are not common in the Vail area but do occur. The
Kevin Douglas
November 30, 2016
Revised April 10, 2017
Page 2
debris flow hazard at the subject site is due to the hillside drainage which outlets several hundred
feet southwest of the site into controlled drainages through the neighborhood. The subject site is
located near the northeastern limit of the potential debris fan flow from the drainage and below
several developed lots.
Avalanches occur from snow pack on steep slopes when weak layers of snow pack develop
and/or additional heavy snow or precipitation add to the snow pack. Based on the thick trees and
existing residences above the project site, there has apparently not been a recent avalanche in this
area and the risk (just uphill of the subject lot) is a potential impact area rather than an area of
historic impact.
The potential hazards appear to be an active geologic process at the subject site and in 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 the hazards. We are not aware of
reported debris flows or snow avalanche in the area. Although the probability of a debris flow
impacting the project site is unknown, a debris flow has the potential to cause property damage
and the need for cleanup. If this risk is not acceptable to the owner, then the feasibility of
mitigation should be considered.
We understand that there have not been historic debris flow impacts to the property area and the
owner accepts the risk that potential geologic hazards may pose to the residence. Based on our
review of the proposed grading plan for the addition which allows for surface drainage along the
south side of the property, in our opinion, "the site is in a geologically sensitive area but the
proposed development will not increase the hazard to other property or structures, or to public
buildings, right of ways, roads, streets, easements, utilities or facilities or other properties of any
kind." (ref. Town of Vail Code, section 12-21-13. B.2).
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 conclusions and recommendations submitted in this report are based
upon the geologic hazard mapping by others, our field observations and experience in the area.
We are not responsible for technical interpretation of our findings by others.
If you have any questions or need further assistance, please call our office.
Sincerely, • -.
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Project Na. 16-7-574
Kevin Douglas
November 30, 2016
Revised April 10, 2017
Page 3
REFERENCES
Town of Vail, 2000a. Official Roclfall 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).
H-P KUMAR Project No. 16-7-574