Chicken Express-CS080226 (2)
~~~~A~Y
I PRINCIPAL
MARC O. BENTLEY, P.E.
February 26, 2008
Mr. Kenneth M. Griffin, P.E.
Director of Engineering & Public Works
City of Coppell
255 Parkway
Coppell, Texas 75019
Re: Chicken Express
BEl No. 27149
Dear Mr. Griffin:
We are requesting that the on-site pavement be 8 inch thick for firelanes and 6 inch thick for all
other areas as shown on Paving Plan Sheet C1. We also propose the concrete be 4000 PSI
with #3 rebar on 18 inch centers in both directions on 6 inch compacted subgrade. This request
is being made in lieu of lime stabilizing the subgrade.
We would appreciate your consideration of our alternate paving section. If you should have any
questions or concerns, please do not hesitate to call.
Sincerely,
BENTLEY ENGINEERING, INC.
77J,O~
Marc O. Bentley, P.E.
CIVIL ENGINEERING
4125 BROADWAY BLVD. 972-240-4821 [TEL]
SUITE A250 972-240-0922 [FAX]
GARLAND, TEXAS 75043
WWW.BENTLEYENGINEERING.COM
ASSOC'ATES INC.
REPORT
OF
GEOTECHNICAL EXPLORATION
CmCKEN EXPRESS
EAST BELTLINE AND DENTON TAP ROAD
COPPELL, TEXAS
ATC PROJECf NO. 74.20467.0008
Prepared for:
Franz-Jeanes-Lazo-Cora & Associates, Inc.
4055In~tionalPlaza,Sllire510
Fort worth, Texas 76109
Prepared by:
ATC Associates IDe.
1555 Valwood Parkway, Suite 160
CarrolltoD, Texas 75006
Phone: (972) 919-3300
Fax: (972) 919-3395
September 25, 2007
Report of Geotechnical Exploration
Chicken Express
East Beltline Road and Denton Tap Road
Coppell, Texas
4.0 PAVEMENT RECOMMENDATIONS
4.1 DESIGN CONSIDERATIONS
Traffic loading information for the proposed parking lot pavement was not available at the time of this report
submittal. It was therefore assumed that the parking areas will be subject to automobile traffic only (light duty
pavement section) and that the drives will be subject to both automobile and occasional medium to heavy truck
traffic (medium duty pavement section). If the assumed traffic loading conditions are different than indicated
herein we should be contacted since it could impact the reconnnendations presented in the following sections.
4.2 PAVEMENT SECTIONS
Recommended pavement sections for rigid pavement for the parking lots and drive thru are presented in the
following Table 1.
TABLE 1 - RIGID PAVEMENT SECTIONS
Portland Cement Concrete
5 inches
6 inches
Lime-Stabilized Subgrade
6 inches
6 inches
Total Pavement Section
11 inches
12 inches
A minimum 7-inch thick concrete pavement is recommended for the dumpster pad and the area in front of the
dumpster and for all fire lanes.
4.3 CONCREl'E PAVEMENT MATERIALS
The concrete should have a minimum compressive strength of3,ooO psi at 28 days for the light duty traffic and of
4,000 psi at 28 days for the medium duty traffic. Concrete quality will be important in order to produce the
desired flexural strength and long-term durability. Assuming a nominal maximum aggregate size of 1 inch, the
concrete is reconnnended to have entrained air of 5 percent (:I:: 1 percent) and a maximum water cement ratio of
0.50.
Proper joint placement and design is critical to pavement performance. Contraction joints should typically be
placed at 15 feet on-center. The contraction joints should be saw cut as soon as possible after placement of
concrete but before shrinkage cracks occur. The concrete saw cut should be at least 3/8-inch wide and 2 inches
deep. Control joints should be sawed within 5 to 12 hours after placing concrete.
FLJC & Associates, Inc.
Fort Worth, Texas
-11-
<YATC
Report of Geoteclmical Exploration
Chicken Express
East BeJtline Road and Denton Tap Road
Coppell, Texas
Isolation joints should be placed where the pavement will abut the building, drainage in-lets, manholes, T- and
unsymmetrical intersections, and anywhere differential movement between the pavement and a structure may take
place. The isolation joints should 0.5 inch wide.
All joints including sawed joints should be properly cleaned and sealed as soon as posSlble to avoid infiltration of
water, small gravel, etc. Either cold-poured or hot-poured sealing material may be used. Backing should be
provided to hold the isolation joint sealant in place. Manufacturers' instructions for mixing and installing the joint
materials should be followed.
It is recommended that the concrete pavement be reinforced with No. 3 bars placed on chairs on approximately
24-inch centers in each direction. The perimeter of the pavements should have a stiffening curb section to reduce
the potential for distress due to heavy wheel loads near the edge of the pavements and to provide channelized
drainage.
4.4 LIME-STABILIZED SUBGRADE
The clay soils at this site are highly active and have a significant shrink/swell potential. These clays react with
hydrated lime, which serves to improve their support value and provide a firm, uniform subgrade beneath the
paving. A stabilized subgrade would improve pavement performance and reduce future maintenance
requirements.
The lime should be thoroughly mixed and blended with the top 6 inches of the subgrade (TxDOT Item 260) and
the mixture compacted to a minimum of 95 percent of maximum dry density as determined by ASTM D 698,
within 2 percent of the soil's optimum moisture content. The lime stabilized subgrade should extend at least one
foot beyond exposed pavement edges, if possible, in order to reduce the effects of shrinkage during extended dry
periods.
Project specifications should allow a curing period between initial and final mixing of the 1ime/soil mixture. After
initial mixing, the lime treated subgrade should be lightly rolled and maintained at or to 5 percent above the soil's
optimum moisture content until final mixing and compaction. A 2-day curing period is recommended for these
soils. The following gradation requirements are reconnnended for the stabilized mataials before final
compaction:
Sieve Size Percent Passing
1 3/4" .. ......... .... ....... ......... ........... ........ ......... ........ .........MiniInum 100
No.4 ...............................................................................MiniInum 60
All non-slaking aggregates retained on the No.4 sieve should be removed before testing.
The site should be graded to prevent ponding and infiltration of excessive moisture on or adjacent to the pavement
areas.
A minimum of six percent hydrated lime, by dry weight, should be used for lime treatment of the pavement
subgrade soils. The application rate oflime for a depth of 6 inches is 27 pounds per square yard
FLJC & Associates, Inc.
Fort Worth, Texas
-12-
(YATC
Report of Geotechnical Exploration
Chicken Express
East Heltline Road and Denton Tap Road
Coppell, Texas
Lime-stabilized soil should be compacted to a mininmm of 95 percent of the maximmn dry density defined by the
ASlM D 698. Lime-stabilized subgrade should be compacted at moisttrre content between -2 to +2 percentage
points of the optimum moisture content.
Sand should be specifically prolnbited beneath pavement areas, since these more porous soils can allow water
inflow, resulting in heave and strength loss of subgrade soils. It should be specified that only lime stabilized soil
will be allowed for fine grading. After fine grading each area in preparation for paving, the subgrade surface
should be lightly moistened, as needed, and recompacted to obtain a tight non-yielding subgrade.
4.5 PAVEMENT CONSIDERATIONS
Soils at the site are highly active and differential heave area should be anticipated. The pavement service life may
be reduced due to water infiltration into subgrade soils through heave induced cracks in the pavement section.
lbis will result in softening and loss of strength of the subgrade soils. A regular maintenance program to seal
pavement cracks will help prolong the service life of concrete pavement.
The life of the pavement can be increased with proper drainage. The site should be graded to prevent ponding
adjacent to curbs and pavement edges. Backfill materials capable of holding water behind the curb should not be
permitted. Flat pavement grades should be avoided. All joints and pavements should be inspected at regular
intervals to ensure proper performance and to prevent crack propagation.
Trees near proposed pavement areas should be removed if practical, due to their contnbution to loss of subgrade
support during dry periods of the year. Where trees will remain near the pavement, consideration should be given
to the use of thicker pavement sections and/or additional reinforcing steel to resist the loss of subgrade support or
movement of the pavement due to tree root.
FLJC & Associates, Inc.
Fort Worth, Texas
-13-
<YATc