Park West CC(13)-CS 910510MASON
JOHNSTON
& ASSOCIATES,
geotechn~al ~nsultan~
May 1991
City of Coppell
Engineering Department
Coppell City Hall
255 Parkway Blvd. /~
Coppell, Texas 75019
Attention: Ms. Shoh~e/-~ane~hmand, P.E.
Acti~l'~y Engineer
Re: Soil Treatment for Pavement
Toyo Tires Site
Park West Commerce Center
Coppell, Texas
Raymond C. Mason, RE.
Chairman of the Board
Aubrey D. Henley, R.G., C.E.G.
President
John W. Johnston, P.E.
Executive Vice-President
W~lliam D. Flanigan, R.G.
Vice President
W..lay Cromeans
Vice President
Richard C. Mason
Controller
Dear Ms. Daneshmand:
On 2 May 1991, I discussed with Mr. Larry Davis of the City of
Coppell the subject of treatment of subgrade soils under
pavement. This letter is intended to clarify the proposed
treatment of soils under pavement at the Toyo Tires Site.
We believe that the proposed soil treatment method described in
the attached specification section "0220~ - EARTHWORK" and our
geotechnical report, No. MJ5771, also attached, provides a
reasonable approach to soil treatment under pavement.
Basically, in our investigation of the site, we found that the
moisture contents of the near-surface soils were at a level
close to the wet moisture content as determined by Method
TEX-124-E of the Texas State Department of Highways and Public
Transportation. In addition, two swell tests performed on
near-surface soils from the site indicate that these soils, in
the moisture state present at the time of our investigation,
have low swell potential. Based on these data, and our
experience with similar treatment of the soils at the Tract 1
site at Park West Commerce Center, we believe that the concept
of maintaining the existing moisture condition in the
near-surface soils and placing fill soil at moisture contents
at or above the optimum moisture content determined by a
Standard Proctor Compaction Test, ASTM D 698, provides a viable
subgrade treatment which will be compatible with the pavement
section designed for this project.
235 Morgan Ave., Dallas, Texas 75203-1088 (214) 941-3808
10 May 1991
City of Coppell
page two
In approach areas, we understand that the City of Coppell will
require further treatment of the subgrade. We propose to
overexcavate the approaches by six (6) inches and place a
6-inch thick commercially-available crushed stone or sand
Cement Treated Base (CTB) below the pavement section. The
moisture condition of the subgrade below the cement treated
base would be controlled as required for the pavement above.
We trust this adequately describes the subgrade treatment which
we plan to undertake for the Toyo Tires project. Please call
if you have any questions.
Very truly yours,
John W. Johnston, P.E.
Executive Vice President
Mason-Johnston & Associates, Inc.
JWJ:lf
Encl
cc: w/o encl Mr. Don Mills, Prentiss Properties Limited, Inc.
Mr. Gary Rademacher, Pross Design Group
MASON
JOHNSTON
&ASSOCIATES, INC.