HomeMy WebLinkAboutSolar Vail Rockfall report Arthur L Mears, P.E., Inc.
Natural Hazards Consultants
555 County Road 16
Gunnison, CO 81230
Tel/Fax: (970)641-3236
May 31, 2008
Mr. Henry Platt
GPSL Architects, P.C.
1000 South Frontage Road West, Suite102
Vail, CO 81657
RE: Solar Vail rockfall study
Dear Mr. Platt:
At your request, I visited the site of the proposed Solar Vail building construction
in Vail last Thursday, May 29. The purpose of my site inspection was to evaluate
the rockfall potential at the existing and new building site and recommend
mitigation if needed.
Town of Vail Rockfall Map
The entire Solar Vail property and current building are located in a "moderate-
severity" rockfall hazard area on the Town maps. The lower boundary of the
hazard area extends through the existing building and downslope to the south
side of the North Frontage Road. Because the site is within a designated rockfall
hazard area the owner and architect
are concerned that the new building
Photo 1. View from south is properly protected from rockfall, if
this is necessary.
Site Location and rockfall hazard
�,�,,��,, , •� .� The existing building (which will be
�`,����.,�' ,� _ry -- _ removed) is immediatel y north of the
''�`�` � - _. � north Fronta e Road a roximatel
- ,;,., ._��.� J pp Y
'�� �,'� ' _ - - -- � -° 1,000 feet east of the pedestrian
. .'���..�" - overpass that spans I-70. Photos 1
,�� s ` � `'�`� �,�Ff; �;� and 2 provide overviews of the
w � ' ` �- �-�� existin buildin from the south and
� ��,.��� 9 9
��_�,�„ ,,,, F„�, ,,. � ,�...:_ � . east directions, respectively. The
_ existing multiplex building is located
� �� `'°' �- - y��'' �� --• at approximately 8,200 feet elevation
below a moderately steep slope that
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is 8,550 feet elevation at the top, about 350 feet above the building. Residential
buildings of the "Potato Patch Re-Subdivision" are located on the top of the slope
above the existing building (Photo 1). The north Frontage Road and I-70 are
located below and to the south of the multplex. Photo 2 is a side perspective
view of the existing building and the slope above it. The slope is inclined at
vertical angles of 20° to 35° and is crossed midway by a stand of aspen trees that
are growing in the moderately thick soil that exists on the sloping bench midway
on the slope. Rocks and boulders are embedded in the soil on the slope,
however no cliff bands that could serve as rockfall source areas crop out
anywhere on the slope above the building. This slope does not have a history of
producing rockfall.
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Photo 2. View from southeast
Development plans
Development plans are to remove the existing building and replace it with a more
modern one at the same location. The property is only about one acre in area
and the building site is currently near the base (south end) of the property where
terrain is not steep. No other reasonable options exist for the new building
location.
Conclusions
These conclusions are based on my site inspection earlier this week, study of
aerial images and knowledge of rockfall in the Vail area and at other sites in
western North America. My conclusions are as follows:
1. The existing and proposed building site (same location as current
building) are not exposed to any rockfall hazard from current conditions
observed on May 29, 2008;
2. Because rockfall hazard does not exist, mitigation will not be needed.
Minor rockfall hazard could develop if (a) excavation into the slope directly
behind takes place during or after new building construction and this exposes or
dislodges rocks and/or (b) if the slope above the Solar Vail site (within the Potato
Patch near the top of the ridge) were disturbed and large rocks were dislodged
onto the slope. If conditions "(a)" or "(b)' were to take place, appropriate rockfall
mitigation procedures would then be needed. If the slope conditions do not
change, conclusions "1" and "2" are valid.
You as my client should know that while our company can and does attempt to
uphold high professional standards, the state of scientific and engineering
knowledge is incomplete, and does not always permit certainty. The complex
phenomena involved in rockfall cannot be perFectly evaluated and predicted, and
methods used to predict rockfall behavior change as new research becomes
available. While we can and will offer our best professional judgment, we cannot
and do not offer any warranty or guarantee of results.
Sincerely,
Arthur I. Mears, P.E.