PA9901-CS130417FUGRO CONSULTANTS, INC.
April 17, 2013
Project No. 4013 -2020
Friends of Coppell Nature Park
P.O. Box 1363
Coppell, Texas 75019
Attention: Mr. Lou Duggan
Pad Preparation Recommendations
Biodiversity Education Center
Coppell, Texas
Dear Mr. Duggan:
ORD
2880 Virgo Lane
Dallas, Texas 75229
Tel: 972 - 484 -8301
Fax: 972 -620 -7328
As requested, Fugro Consultants met Northstar Construction personnel at the site on April 17, 2013
to evaluate the building pad for the education center. The earthwork contractor was also onsite
and had started grubbing the site. A total of two test pits were excavated within the building pad
down to approximately 3 -ft depth. Test Pit 1 was located in the southwest corner of the pad while
Test Pit 2 was located in the southeast corner of the pad.
The soil conditions in the two test pits were very similar, consisting of a dark brown sandy clay to
clayey sand to 1 to 1.5 -ft depth, which was underlain by a light brown clayey sand to the total depth
of the pits at 3 -ft. The base of both excavations was sandy and fairly dense. Large roots and other
organics were observed to be in the top 6 -in of the exposed soil in both pits. Test Pit 2 contained
some construction debris consisting of brick and concrete indicating there had been a structure at
this location at one time. Samples of both the predominant soil samples were obtained for Proctor
testing at the laboratory.
Methods of pad preparation were discussed. The original geotechnical report (Fugro Report
04.4012.1022) indicated excavating down to 5 -ft depth then using the excavated soils to backfill the
pad back to original grade. The overexcavation was pfanned to provide a more consistent and
stronger subgrade for the building slab. Based on the results of the test pit observations, we
believe the pad preparation can be modified to between 2 and 2.5 -ft depth. The pad preparation
should consist of the following:
A member of the Fugro group of companies with offices throughout the world..
Coppell Biodiversity Education Center (4013 -2020)
April 17, 2013
• Strip the building pad site down an additional 6 -in or until the larger roots (over 0.5 -in
diameter) are removed. These more organic soils should be stockpiled separately from the
remainder of the excavated soils that will be used to backfill the pad.
• Continue excavating the pad down, between 2 and 2.5 -ft depth until the base of the
excavation consists of the light brown clayey sand. Use a vibratory steel wheel or padfoot
roller to thoroughly compact the exposed and underlying soils.
• Use the excavated pad soils to backfill the building area using maximum 8 -in lifts and
compacting to 95 percent or more of the materials maximum dry density (Standard Proctor)
at a moisture content between 0 and +5 percentage points above optimum.
• The remainder of the recommendations in the original report should be followed for design
and construction considerations.
Fugro Consultants Inc. appreciates the opportunity to be of service to the Friends of Coppell Nature
Park and SHW on this project. We trust the information provided herein is sufficient for your use.
Please contact us if we may be of further service.
Sincerely,
FUGRO CONSULTANTS INC.
TBPE Firm Registration No. F -299
--
David A. Belcher, F
Senior Project Man
Attachments: Site Photographs
DAB/lb
Copies Submitted: 1 — email Amy King /SHW ( akingshwgroup.com }
1 — email Ben Reiners /Northstar ( breiners(a-),nstarbuilders.com }
GRO'