HomeMy WebLinkAboutEngineer's Letter - Review of Rockfall Condition 06.29.2017H -PKU MAR
Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
June 29, 2017
Trevor Ruonavaara
160 Spring Ridge Drive
Glenwood Springs, Colorado 81601
trfinishes @gmai ].corn
Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado
JUN 3 0 2017
:'.
Project No. 17-7-235.01
Subject: Review of Rockfall Condition, Lot 76, Spring Ridge Reserve PUD, Phase 4, 76
Hidden Valley Drive, Garfield County, Colorado
Dear Trevor:
As requested, the undersigned representative of H-P/Kumar observed the hillside above the
proposed residence at the subject site on June 29, 2017 for potential rockfall impacts to the
proposed construction. We previously conducted a subsoil study for design of foundations at the
site and presented our findings in a report dated April 4, 2016, Project No. 16-7-235.
The residence will be located in the lower part of the building envelope, roughly between the
exploratory boring locations shown on Figure 1 of our previous report. The foundation
excavation for the structure was substantially complete at the time of our site visit. Based on the
foundation excavation, it appears that the uphill side of the residence will extend to within about
20 to 30 feet of the existing, abandoned irrigation ditch located uphill and to the northeast.
The hillside above the proposed residence consists of relatively shallow colluvium, comprised of
silty, clayey sand with gravel and cobbles, overlying sandstone bedrock of the Maroon
Formation. The ground surface slopes at about 40 to 45% (22° to 24°) up to the northeast, which
roughly coincides with the bedding dip of the formation rock. Scattered, mostly flat (tabular)
shaped rock fragments, typically up to about 1 foot in size, are exposed on the hillside to the top
of ridge about 270 feet above the building area. Drainage on the slope above the proposed
residence appears to be by sheet flow.
Trevor Ruonavaara
June 29, 2017
Page 2
Based on the material observed on the slope and the lack of evidence of rockfall into the building
area, mitigation of rockfall potential for the proposed construction, in our opinion, is not
warranted. If alterations to the slope above the residence are planned in the future, we should be
consulted to review the planned alterations for potential rockfall hazard.
If you have any questions or need further assistance, please call our office.
Sincerely,
H -P; KUMAR
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James A. Parker, P.E., /4" 2a1
Rev. by: SLP ,' (f .741 ti / •',50717
JAP/kac
cc: Garfield County Community Development — Dave Argo(dargo@gariield-county.com)
Terry Heidi Ruonavaara (thruonavaara@msn.com)
H-PkKUMAR
Project No. 17-7-235.01