HomeMy WebLinkAboutEngineering letter_3.pdf H... ti Ku mAR5020 County Road 154
Glenwood Springs,CO 81601
Geotechnical Engineering I Engineering Geology Phone:(970)945.7988
Materials Testing I Environmental
Fax (970)945-8454
Email. hpkglenwood(Qkumarusa.com
Office Locations: Parker,Glenwood Springs,and Silverthome,Colorado
January 16, 2017
Sundial HOA
Attn: James Crane
cranej@wustl.edu Project No. 16-7-590
Subject: Pavement Section Thickness Recommendations, Proposed Access Drives for
Garage Replacements, Sundial Townhomes, 5040 Main Gore Place, Vail,
Colorado
Dear Mr. Crane:
As requested, H-P/Kumar is providing pavement section thickness recommendations for the
proposed access drives at the subject site. This report summarizes our assumptions and
recommendations. The services were performed in accordance with our proposal for
professional services to Sundial HOA c/o Pierce Architects dated December 14, 2016.
Hepworth-Pawlak Geotechnical (now H-P/Kumar)previously performed a subsoil study for the
proposed garages and submitted the findings in a report dated October 31, 2014.Job No. 114
418A.
Proposed Construction: The access drives for the garages will be re-built concurrent with the
new garages. The portion of the access drives along the southwest side of the southern two
garages will consist of the main development access traffic and include trash, concrete, and
possible other trucks as well as passenger vehicles. Based on our experience, we estimate an 18
kip equivalent load application (EDLA) of about 15 for this condition including a small amount
of construction traffic. We assume final grades for the road/access drives will remain essentially
the same.
Recommendations: The subgrade soils encountered at the site were non-plastic, slightly silty
sand,gravel and cobbles. The soils likely have AASHTO A-1-a classification which are
considered relatively good support for pavement sections; however there could be different fill
soils in areas. Also, groundwater level is shallow at the site which would act to increase the soil
susceptibility to frost heave. We estimate an Hveem stabilometer"R"value of about 20 for the
subgrade soils.
Using CDOT design procedures with an"R" value of 20, 18 kip EDLA of 15, a Regional Factor
of 3.0 and a serviceability index of 2.0, we recommend the minimum pavement section thickness
consist of 4 inches of asphalt on 8 inches of base course or 5 inches of asphalt on 4 inches of
base course. Concrete sections should consist of a minimum 6Y2 inches of concrete on 4 inches
of base course.
- 2 -
The base course should meet CDOT Class 6 specifications. All base course and required
subgrade fill should be compacted to at least 95%of the maximum standard Proctor density at a
moisture content within about 2%of optimum. Concrete should have a minimum 28 day
compressive strength of 4,500 psi and be air entrained.
Required fill to establish design subgrade level can consist of the on-site granular soils or
suitable imported granular soils approved by the geotechnical engineer. Prior to fill placement,
any topsoil or fine grained soils should be removed, the subgrade scarified to a depth of 8 inches,
adjusted to near optimum moisture and compacted. In soft or wet areas,the subgrade may
require drying or stabilization prior to fill placement. A geogrid and/or subexcavation and
replacement with aggregate base soils may be needed for the stabilization. The subgrade should
be proofrolled. Areas that deflect excessively should be corrected before placing pavement
materials. The subgrade improvements and placement and compaction of base materials should
be monitored on a regular basis by a representative of the geotechnical engineer. Once traffic
loadings are better known,we can review our pavement section recommendations when
requested.
Drainage: The collection and diversion of surface drainage away from paved areas is extremely
important to the satisfactory performance of the pavement. Drainage design should provide for
the removal of water from paved areas and prevent excessive wetting of the subgrade soils.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
express or implied. The conclusions submitted in this report are based upon the data obtained
from the previous exploratory borings drilled at the site for building foundation design,
information provided to us regarding the traffic loading, and our experience in the area.
If you have any questions or if we may be of further assistance, please let us know.
Respectfully Submitted,
H-P:4err`;4" aQ It*
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David A. Young, P.E # ,. 1.17-17 `'i '
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Rev. by: SLP `-
cc: Pierce Architects—Bill Pierce(bill gvailarchitects_com)
Pierce Architects—Will Lones (wlones@vailarchitects.com)
Martin/Martin—Mark Luna(mluna .martinmartin-mtn.com)
Jack Hunn(jackf'hunnconsultinggroup,corn)
Roger Eastman (rogereastmanmac.com)
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H-P KIIMAR
Project No. 16-7-590