HomeMy WebLinkAboutEngineer's Letter - Review of Rockfall Condition 05.10.2017H-P�KUMAR
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
May 10, 2017
Craig Whitlock
P.O. Box 1757
Glenwood Springs, Colorado 81602
sitewest@msn.com
Office Locations: Parker, Glenwood Springs, and Silverthorne, Colorado
Project No. 16-7-121
Subject: Review of Rockfall Condition, Lot 72, Spring Ridge Reserve PUD, Phase 4, TBD
Hidden Valley Drive, Garfield County, Colorado
Gentlemen:
As requested, the undersigned representative of H-P/Kumar observed the hillside at the subject
site on May 10, 2017 for potential rockfall impacts to the site. We previously conducted a
subsoil study for design of foundations at the site and presented our findings in a report dated
July 13, 2016, Project No. 16-7-121.
The residence will be located in the middle part of the building envelope roughly between the
exploratory boring locations shown on Figure 1 of our previous report. The uphill side of the
residence will be about 30 feet below the existing abandoned irrigation ditch.
The hillside above the irrigation ditch consists of shallow, rocky colluvium above sandstone
bedrock of the Maroon Formation. The ground surface slopes at about 40 to 45% (22° to 24°)
which roughly coincides with the bedding dip of the formation rock. The colluvium, thickens at
the base of the hillside where the ditch is located and scattered rock from the irrigation ditch
construction are exposed immediately below the ditch. Scattered, mostly flat shaped rock
fragments typically up to 1 to 2 feet in size are exposed on the hillside to the top of ridge about
140 feet above the building area.
No evidence of rockfall into the building area was observed and mitigation of rockfall potential
in the proposed building area, in our opinion, is not warranted. The existing abandoned
Craig Whitlock
May 10, 2017
Page 2
irrigation ditch provides a catchment area for small rock fragments that may slide down the
hillside by erosion and should be kept above the residence for a width of at least 10 feet.
If you have any questions or need further assistance, please call our office.
Sincerely,
H -P= KU MAR
Steven L. Pawlak, P.E.
Rev. by: DEH
SLP/kac
cc: Chase Whitlock (chase@ site-west.com)
H -P KUMAR
Project No. 16-7-121