HomeMy WebLinkAboutAppendix C. Exhibit 14 Slope Stability Memol(+A Kumar & Associates, Inc.•Geolechnical and Materials Engineers and Environmental Scientists
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An Employee Owned Company
5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado March 2, 2020
Norway Island, LLC
Attn: Jean Coulter
P.O. Box 12393
Aspen, Colorado 81612
jeanncoulter@gmail.com
Subject:
Project No. 19-7-615
Geotechnical Review Comments of Grading Plan, Proposed Gorsuch Haus, South
Aspen Street, Aspen, Colorado
Dear Ms. Coulter:
As requested by Tim Carpenter, we are providing review comments for the grading plan
prepared by Sopris Engineering concerning slope stability. We previously conducted a subsoil
study for development of the project at the subject site and presented our findings in a report
dated December 5, 2019, Project No. 19-7-615.
The grading plans for the project considered in our review consist of sheets C.2.00 through
C.2.06 dated January 15, 2020. In general, the development plan and building location is
consistent with that described in our previous report. Of note is that sheet C.2.03, the perimeter
grading plan is identified as conceptual. In the west perimeter area, the building footprint
encroaches the west slope causing oversteepening of the hillside cut slopes. Cut depths for the
drainage swale on that side are up to 10 to 12 feet causing this issue. Typically, the
oversteepening can be handled by structural walls of either the building or the hillside. We
understand that site plan modifications will be made in this area from what is shown by the
current grading.
The slope grading design can generally use the following criteria:
1)Natural dry slope (deep groundwater level, no seepage) parallel cut to slope grade,
2H:1V.
2)Natural wet slope area (perched seasonal shallow water seepage) parallel cut to
slope grade 2½H:1V.
3)Natural wet slope area mitigated by subsurface drainage (such as trench drain),
l¾H:lV.
4)Natural slope area with possible seepage (such as Mtn Road) cut made across
slope grade, 2H: 1 V.
It appears the west side slope stability condition can be mitigated with soils nail walls possibly
stepped in tiers at an effective lH: 1 V with 2½H: 1 V minor cut above that if needed. This
condition occurs for about 150 feet beginning at the southwest building comer
Appendix C. Exhibit 14
Norway Island, LLC
March 2, 2020
Page 2
northwestward. The west side northernmost 2H:1V cut adjacent Shadow Mountain is probably
in a natural dry slope area being lower down on the hillside and the 2H:1 V cut there should be
acceptable. Likewise, the double cut, Mtn Road sta 5+50 at 2H:1 V is across the contours and
appears acceptable.
If you have any questions or need further assistance, please call our office.
Sincerely,
Kumar & Associates,
Steven L. Pawlalld P
SLP/kac4 ���
cc: RA Nelson —Ia
Sopris Engineerin — sse Swann ('s� wann(iDsopriseng corn)
Kumar & Associates, Inc. 0 Project No. 19-7-615