SC-Coppell HS-AG 880426SUBMISSION DEADLINE: 5:00 --~n~. Monday - 8 Days Preceding C'~'~ Council Meeting
~Rav.:, Effective 1/20/88
AGENDA REQUEST FORM,
FOR CITY COUNCIL MEETING: April 26, 1988
REF/FILE NUMBER
II.
: Coppell High School
ITEM CAPTION : Discussion and consideration of variance from Standards of
Snecificati~ns req.iring liming of High School Darking lot located at 185 W.
Parkway Rn.lmvmrd
III. ACTION RECOMMENDED
IV. REP. IN ATTENDANCE
A: STAFF - Steve Gnram- Director of Public Works
Steve Morton, Chief Development Inspector
B: O~IER -Mike Elmore~ S H W C. Inc.
vi.
NOTIFICATION TO
: Dr. Stanfield
METHOD OF CONTACT :
DATE :
FINANCIAL REVIEW : 1. BUDGETED ITEM
2. BUDGET AMOUNT
q,m~rinfmndent: CT~
r~ TX 75019
telephone
4-21-88
3. ESTIMATED AMOUNT FOR THIS ITEM
4. AMOUNT OVER OR UNDER BUDGET
5. LOW BIDDER RECOMMENDED
SOURCE OF FUNDING
CO'S OR BONDS FUNDS
(Series or year authorized)
OPERATING BUDGET (Account Number)
OTHER
APPROVED BY CITY MANAGER :
ITEM NUMBER I ~
YES NO
: YES NO
AGENDA REQUEST FORM
DMEMOI
DEPUTY CITY MANAGER'S COMMENTS/RECOMMENDATION FOR AGENDA ITEM
ITEM #16 CITY COUNCIL AGENDA DATED: April 26, 1988
II. COMMENTS/RECOMMENDATION
Information included in your packet for this particular item are:
1. Formal request and supporting documents furnished by Dr.
Stanfield ;
2. Copy of City Council minutes dated September 8, 1987, Item #16
where Council approved the final plat and variances for the high
school; and
3. Staff's recommendation and supporting documents.
COPPELL INDEPENDENT SCHOOL DISTRICT
°'~~~c David P. Stanfield
'*U'" Superi~
April 19, 1988
Mr. Alan Ratliff
City Manager
City of Coppell
P. O. Box 478
Coppell, Texas 75019
Dear Mr. Ratiiff:
Coppell Independent School District would like to request a
variance of the select fill ordinance related to the sub
grade for paving of streets and parking at the new Coppell
High School at the April 26, 1988, City Council meeting.
Our engineers have indicated in the attached letter that
we have excellent soil to serve as select fill for our
paving requirements. Approval of this request would save
the school district an estimated $140,000.
Thank you for your consideration of this request.
Sincerely,
Dr. David Stanfield,
Superintendent
Enclosure
DS:bv
CC:
Mike Elmore, S H W C, Inc.
File
1~01 Wrangler Drive Coppell, Te~s 75019 (£1,$) ,$71-Illl
817 336-5773
T[ AGUE NALL AND PERKINS
C 0 ~,\' $ U L T I bl G E N G I N E E R
March 29, 1988
Mr. Gary Keep, AIA
SHWC, Inc.
P.O. Bcx 619087
Dallas, Texas 75261
Re:
APR i' 8
SHWc, INC.
Architects, Engineers, Pl~ :..~ s
DALLAS, TEXAS
Coppell High School;
Cement Treat. of Paving Subgrade,
NCTCOG Std. Specs. for Same
Dear Gary:
This afternoon Mike Elmore (SHWC) and I discussed TNP's
evaluations regarding the method of cement treating the
pavement subgrade at the project. Subgrade t~eatment is a
City requirement at this site. Although there will be
strengthening of the pavement section with the subgrade
treatment, it is our opinion (given the good quality of the
native sandy material) that the cost/benefit comparison does
not justify the subject treatment at this site.
We have had success over the last 15 years in designing
reinforced concrete pavement for municipal street and road
projects directly on compacted raw (i.e. natural, existing)
subgrades. In many cases, especially when a clay subgrade was
J~nvolved, a 2-inch sand cushion was placed on the compacted
subgrade prior to placement of the reinforced concrete
pavement. This was a typical pavement section for residential
streets (and still is for many cities) for many years.
Typically, when the street is to be subjected to a higher
traffic volume (e.g. collector or major thoroughfare use),
then a higher strength pavement section is commonly required.
%he extra strength is often provided by constructing a base
course fmr the concrete pavement. This "base course" can take
the form of imported aggregate material and/or chemical
improvement (via additives like lime and cement) of the raw
subgrade.
It is our opinion that the relatively low P.I. (plasticity
index) and sandy subgrade material (or clayey sand) found at
the Coppell High School site is an excellent pavement subgrade
material. When properly compacted (with no lime or cement
additives) we feel that this natural material will provide
adequate support for a reinforced concrete pavement as
proposed for the above project.
915 Florence Street Fort Worth, Texas 76102
Mr. Gary Keep, AIA
March 29, 1988
Page Two
Having related all of the above, we recognize that the City of
Coppell requires that pavement subgrades for private
construction be treated with lime or cement, as appropriate.
Therefore, based upon the City requirement and Maxim
Engineers' March 15, 1988, report of tests of various subgrade
samples at the site, it is our recommendation that cement
stabilization be used on the project with cement being added
at the rate of 3.5% cement b~ dr~ weight of soil (16 lbs. of
cement £~_~l~e__yard).
The method of cement treatment of the subgrade soil shall be
in accordance with either of two specification items in the
North Central Texas Council of Government (NCT~OG) Standard
Specifications. The Contractor should be allowed to use
either Item 4.7 ("Portland Cement Treatment") or new Item 4.9
("Portland Cement Modi~ica_____t~o___n of Sub~rade Soils"). We have
attached copies of both the existing Spec% Item 4.7 and the
new Spec. Item 4.9 (which has recently been authored by
NCTCOG). We feel comfortable in recommending either one of
these pr~>cedures (i.e. either Item 4.7 or Item 4.9). We feel
like the Contractor should decide which Item can be
constructed most economically and provide a price to the Owner
for utilization of his chosen method. Also, he should
communicate in writin~ which Item (i.e. 4.7 or 4.9) that he
will be incorRoratin~ into the construction; the chosen Item
will then ~~_~_~k~rade construction.
The limits of the cement treatment/modification of the
pavement subgrade shall be under all proposed concrete
pavement at the site and extend to a point 1 foot behind the
back of curb (or edge of pavement, as applicable). The
treated/modified thickness of subgrade material shall be
6 inches.
There is one other item that needs to be emphasized. Cement
treatment/modification of the pavement subgrade along the
north line should not be pursued in those areas where the
northern edge of proposed pavement would be constructed at or
near the top-of-bank of recently filled embankment sections.
In these top-of-bank areas there is inadequate lateral support
to allow compaction necessary to provide the subgrade strength
required to support the overlying pavement section. Until the
lower areas to the'north (immediately adjacent to these filled
embankment sections) can themselves be filled and compacted,
there should be a postponement of concrete pavement and
subgrade preparation in these particular areas. There is the
Mr. Gary Keep, AIA
March 29, 1988
Page Three
possibility that if the postponement causes a work delay to
the Contractor, there will need to be some sort of wall or
slope stabilization construction pursued in order to provide
the lateral support necessary to adequately compact the
subRrade under the proposed concrete pavement.
If you have any questions regarding any of the above or the
attached material, please advise.
Sincerely,
TEAGUE NALL AND PERKINS, INC.
John It. Nall,.Jr., P.E.
JHN/11
Attachments
cc:
Coppell I.S.D (Dr. Stanfield)
Maxim Engineers (S. Haneidi)
City of Coppell (Steve Morton)
ITEM 4.1.7.
contract in
satisfactory to the owsEa as to grade, crown and
TRACTOR
durability
4.6.7.
measured for
the plans for the
measurement for lime
Lime treatment shall be paid
yard (M2), as provided in the
price shall be the total
loosening, pulveri~i.'n.g,
mixture and the
finishing, curing and
labor, equipment,
work, all in
measured
as the surface course is constructed. All
that may occur shall be immediately repaired by
Repairs are to be made as
to insure restoration of a
AND PAYMENT:
of
and
mixing,
tools and incid
the
this item shall be paid for
price shall
shall be
(Me) thickness shown on
accepted work. The
) dry weight.
unit price per square
and contract. The contract unit
preparing the roadbed; for
water content in the slurry
sprinkling, compacting
and for all
to complete the
Lime material
~ unit price bid
for all freight involved; for all unloading,
, for all labor, ~quipment, fuels, tools and incidentals
complete the work.
ITEM 4.7. PORTLAND CEMENT TREATMENT
4.7.1. DESCRIPTION: This item shall consist of the treatment of the
base, subbase, or subgrade course which is to be composed of a compact-
ed mixture of soil, portland cement and water; and shall be constructed
as herein specified and in conformity to the cross sections, lines and
grades as established by the owsva. In the event new materials are
placed, rather than using existing base or subbase, the base or subbase
shall be constructed as herein specified and in conformity with the
items governing the base or subbase courses.
4.7.2. MATERIALS:
(a) Portland Cement. Cement shall conform to the requirements of
Item 2.2.1., "Cement."
Co) Water. Water shall conform to the requirements of Item 2.2.4.,
"Water."
(c) Soil. The soil shall consist of approved soil, free from vegetation or
other objectionable matter. It may be either the material encountered
in the existing section, material secured from approved sources shown
on the plans or as designated by the OWNER, or a combination of existing
and additional soil from approved som'ces, as shown on the plans, or as
directed by the
4.7.3. EQUIPMENT: All equipment necessary to properly prosecute,
ITEM 4.'/.4.
perform and complete the work within the contract time, shall be on the
project and shall be approved by the OWN~a as to type and condition
before the CONT~ACroa shall be permitted to begin construction oper-
ations on which the equipment is to be used.
, Soil-cement may be constructed with any machine or combination of
machines and auxiliary equipment that shall produce the results meet-
ing the requirements for soil pulverization, cement application, mixing,
water application, incorporation of materials, compaction, finishing and
curing as specified herein. The CONTRACTOR shall at all times provide
sufficient equipment to enable continuous performance of the work and
its completion in the required number of working days.
4.7.4. CONSTRUCTION METHODS:
(a) General. The primary requirement of this specification is to secure
a complete course of treated material containing a 'uniform portland
cement mixture, f~ee from loose or segregated areas, of uniform densi-
ty and moisture content, well bound and compacted for its full depth
with a smooth surface suitable for placing additional subbase, base or
surface courses. It shall be the responsibility of the CONTRACro~ to regu-
late the sequence of his work to process a sufficient quantity of material
so as to provide full depth as shown on plans, to use the proper amount
of portland cement, maintain the work and to rework the courses as
necessary to meet the foregoing requirements.
~.Cement stabili~ hase ~ not:b~, mixed pr. placed~when the air
~temperat ._uEe_~ iS_.b~l~ o~, 40 d~i Fahrd'n~. eit (.5°C,)' an~f~al~'ng,'esbU~am~rY'
~b~'mixed ~ placed when the*air cempera~ure~s aooye ~o aegrees z -
~'et~beit-(2°C).andrising, the temperature being taken in the shade and
away from artificial heat; and with the further provisions that cement
stabilized base shail be mixed or placed only when weather conditions,
in the opinion of the ownER, are suitable.
0) Treatment for Materiah in Place. BefOre other construction op-
to construct the portland cement treatment lor macenm m pmce m con-
formance with the lines, grades, thickness and typical cross sections
shown on the plans. Unsuitable soil or material shall be removed and
replaced with acceptable soil. The subgrade shall be firm and able to
support without displacement the construction equipment and the com-
paction hereinafter specified. So/t or fielding subgrade shall be cor-~
rected and made stable before construction proceeds.~The soil shall be
~-so pulverized that,,*at the completion of moist-mixing 100 percent by
.~: dry weight it passes a one-inch (25mm) sieve; and a minimum of 80
,.~;.,percent passes a No. 4 sieve; exclusive of gravel or stone retained on
· these sieves. Old bituminous wearing surface shall be pulverized so that
100 percent shall pass a two-inch (50mm) sieve.
(b) Application of Cement. Portland cement shall be spread uniformly
on the soil at the rate specified on the plans or as determined by
preliminary laboratory tests. If a bulk cement spreader is used, it shall
be positioned by string Unes or other approved method during spread-
ing to insure a uniform distribution of cement. Cement shaU be appll..e~..
ITEM 4.7.4.
~0fdy to"such.an ~ that ~ the ~perati.on~.._c~....b~. continuous and
~pleted in 'daylight ~ithhi~'h~ ~of s~ch ~pplication.~,'
The percentage of moisture in the base at the time of cement appli-
cation shall not exceed the quantity that shall permit uniform and inti-
mate mixture of soil and cement during dry-mixing operations; and it
shall not exceed the specified optimum moisture content for the soil-
cement mixture.
No equipment, except that used in the spreading and mixing, shall
be allowed to pass over the freshly spread cement until it is mixed with
the soil.
(c) Mixing and Processing. The following method of mixing and proc-
easing may be used at the option of the COSVaACVOa.
(1) Multiple Pass Traveling Mixer. After the cement has been ap
~:plied, it shall be dr,j~h~xed with the soil. Mixing shall continue until the
ce~nent has been sufficiently blended with the soil to prevent the forrna-
tion of cement balls when water is applied. Any mixture of soil and
cement that has not been compacted and finished shall not remain un-
disturbed for more than 30 minutes.
Immediately after.the'dry-mixing of soil and cement is complete,
· ~water as necessary shall be uniformly applied and incorporated into the
mixture. The pressurized equipment and the supply provided shall be
adequate to insure continuous application of the required amount of
water to sections being processed withifi~"h6~'~ bf the'applicatien~",,-
- ~,of the cement. Proper care shall be exercised to insure proper moisture
distribution- at all times. After the last inc~ement of water has been
added, mixing shall continue until a thorough and nniform mix has been
obtained. .
. (2) Single-Pass Traveling Mixing'Plant. A/ret the cement has been
applied, it shall be sufficiently dry-mixed with the soil to prevent the
formation of cement balls when water is applied. Unpulverized soil
lumps in the soil cement mixture immediately behind the mixture that
are dry shall not be allowed. Should this condition prevail, the comm~c-
voa shall 'prewet" the raw soil as n _ecesss~__~y to correct this condition.
The mixer shall be provided with means for visibly and' accurately
gauging the water application. The water shall be applied uniformly
through a pressure spray bar. .
After cement is spread, mixing operations shall proceed as fol-
lows:
The mixer shall, in one continuous operation, mix the air-dry soil
and cement full depth; add the required moisture uniformly; thoroughly
moist-mix the soil, cement and water; spread the completed soil cement
mixture evenly over the machine-pressed width of the subgrade; ~nd
leave it in a loose condition ready for inunediate compaction. The soil
and cement mixture shah not remain undisturbed after mixing and be-
fore compacting for more than 30 minutes.
(3) Central Mixing Plant. The soil, cement and water shall be dry-
mixed in a pugmill either of the hatch or continuous-flow type. The
plant shall be equipped with feeding and metering devices which shall
ITEM 4.7.4. 257
add the soil, cement and water into the mixer in the specified quanti-
ties. Soil and cement shall be mixed sufficiently to prevent cement ball.~
fi.om forming when water is added. Mixing shall continue until a uni-
form and intimate mixture of soil, cement and water is obtained. The
mixture shall be hauled to the construction site in suitable vehicles
equipped with protective covers. The mixture shall be placed on the
moistened subgrade in a uniform layer by an approved spreader or
spreaders. Not more than 30 minutes shall elapse between the place-
ment of soil-cement in adjacent lanes at any location except at longitudi-
nal construction joints. Not more than 30 minutes shall elapse between
the start of spreading the soil and cement mixture and start of compac-
tion. Not more than 60 minutes shall elapse between the start of moist-
mixing and the start of compaction of the soil-coment. The layer of
soil-cement shall be uniform in thickness and surface contour; and in
such quantity that the completed base shall conform to the required
grade and cross section. Dumping of the mixture in piles or windrows
upon the subgrade shall not be permitted.
(d) Compaction _and Finis.hi'pg. ,The material shall be compacted to 95
percent of the maximum density as established in accordance with Tex-
as SDHPT Test Method Tex-113-E. At the start of compaction, the
percentage of moisture in the mixture and in unpulverized soil lumps,
based on oven-dry weights, shall not be below or more than two per-
centage points above the specified optimum moisture content; and shall
be less than that quantity which shall cause the soil-cement mixture to
become unstable during compaction and finishing. When the uncom-
patted soil-cement mixture is wetted by rain so that the average mois-
ture content exceeds the tolerance given at the time of final compac-
tion, the entire section shall be reconstructed in accordance with this
specification at the sole expense of the co~?~AcroR. The specified op-
timum moisture content and density shall be determined in the field on
representative samples of soil-cement mixture obtained fi.om the area
being processed.
Prior to the beginning of compaction, the mixture shall be in a loose
condition for its full depth. The_loose. mLx,.,tur.e shall~then be uniformly
%.'.:.co.mpacted to the-speCified density within tw° hours. After the S~il'~d
cement mixture, except the.top mulch, is compacted, water shall be
uniformly applied as needed and thoroughly mixed in with a spike tooth
harrow or equal. The' surface shall then be 'reshape~l to the required
lines, grades and cross section and then lightly scarified to loosen any
imprint left by the compacting or shaping equipment.
The resulting surface shall be thoroughly rolled with a pneumatic
tire roller and "clipped," "skinned," and "tight-bladed" by-a power
~?grade~: to'a depth ~if apP~.i~{~ly 1/4inch~(6mm), moving all loosened
soil and cement fi.om the section. The surface shall then be thoroughly
compacted with the pneumatic roller, adding small increments of mois-
ture as needed during roiling. When directed by the OV~Ea, surface
finishing methods may be varied fi.om this procedure, provided a dense,
uniform surface, flee of surface material, is maintained at its specified
optimum during all finishing operations. Surface compaction and finish-
ITEM 4.7.~.
ing shall proceed in such a manner as to produce, in not more than two
hours, a smooth, closely knit surface; free of cracks, ridges or loose
material; conforming to the drawn grade and line shown on the plans.
4.7.5. PROTECTION AND COVER: A/'cer the roadway has been fin-
ished as specified herein, it shall be immediately protA~zte~l ~i6s~
~drying by applying two-tenths (0.2) gallon per.,yard~(1L per Mz) RG-2
~..~cut-hack 'asphalt.~ Immediately prior to application of RC-2, the section
shall be wetted by the use of pressure water distributors so that all voids
in the soil-cement surface are filled with water, but without free water
standing on the surface. The RC-2 cure shall be applied while this mois-
ture condition exists so that undue asphalt penetration of the soil-cement
surface shall be prevented; and at the same time aided in complete
coverage by the RC-2. Should it be necessary for construction equipment
or other traffic vehicles to pass over the section before the RG-2 has dried
sufficiently to prevent pickup, it shall be the responsibility of the cos-
~^croR to dust or sand the surface before such use. ThE
~shall also maintain this curing cover during the seven-day protection so
~ that all bf th~'S~il-~-~in/~/~t b~se 'c0urs~ shall be covered effectively with
RC-2 during this period. The RC-2 curing coat shall remain in place for
the additional asphalt-wearing surface.
4.7.6. OPENING TO TRAFFIC: The co~rr~croa shall not be permit-
ted to drive heavy equipment over completed portions. Pneumatic-tired
equipment required for hauling cement and water may be permitted to
drive over after the surface has hardened sufficiently to prevent the
equipment from marring the surface, provided that protection and
cover are not impaired. ,The-soil-~ement~cOurse may~be'opened to 10cai
~tr~ffic .as: soon as the. RC_~2~ has been .applied 'and'dusted'b~'~ride~d
necessary~to~prevent it,from 'being picked up by traffic. ,.C..0mpleted
portions may be opened to' all traffic after seven days. **
4.7.7. MNffI'EN~NCE: The co~r~croa shall be required, within the
lindts of his contract, to maintain the soil-cement treatment in good
condition from the time he first starts work until all work shall have
been completed. Maintenance shall include immediate repairs of any
defect that may occur after the cement is applied. Such maintenance
work shall be done by the co~rrRscroa at his own expense and repeated
as often as necessary to keep the area continuously intact. Repairs are
to be made in such a manner as to insure restoration of a uniform sm--
face for the full depth of treatment. Any low area shall be remedied by
replacing the material for the full depth of treatment rather than add-
ing a thin layer of stabilized material to the completed work.
~ 4.?.8. MF.~$URI:MI:NT~ND P&YML~IT: This work shall be measured
by the square yard (M2) of eompl~d and accepted cement stabilized
base course. Measurement for c~jtient shall be by the ton, 2,000 pounds
allowance shall be made for~y materials used or work done outside
(900 kg) of dry weight, as de~rmined by certified weight tickets. No
the_ "mits,established ~ the ow~a. The work performed and mate-
rial furnishedas presc~i~ed by this item and measured as provided in
ITEM 4.8.3, / 2SS
/
this item shall be paid for at the unit price bid fog'so_il-cement treated
base, subbase, or subgrade course, which price ~all be full compensa-
tion for pulverizing the soil material; for hand!~tig; hauling and spread-
ing cement; for mixing the cement with the ~lverized soil; furnishing,
hauling and mixing water with the soil-cer~dnt nu'xture; spreading and
shaping the mixture; compacting the miy~t~tre, including all rolling re-
quired for this compaction; surface finis~ng; curing; and for all manipu-
lation, labor, equipment, appliances, ~'ols and incidentals necessary to
complete the work and carry out ~q'e maintenance provisions in this
specification. Cement material measured as provided in this item shall
be paid for at the unit price bid/for cement mate_~ _al, _which price shall
be compensation for furnishin~he material; for_all freight involved, for
ail unloading and storing; a~ for ail labor_, eq.u.i.pment, fuels, tools and
incidentals necessary to ~plete the work, all in accordance with the
plans and these specifi~'tions.
DESCRIPTION: This item shall consist of a treated
combination of soil and liquid asphaltic material
mixed, and finished in accordance with these s
lines, grades, thickness and typical cross
on the plans, directed by the
4.8.2.
(a) Asphaltic The asphaltic material of the type
grade shown on the and shall conform uirements for
grade specified, as in Item 2.4., Materials."
(b) Water. Water shall to the nirements of Item 2.2.4.
,q~rater.,,
(c) Soil. Soil shall consist of soil, free from ye
other objectionable matter; and may either the material
in the existing roadbed;
plans or approved by the OWNER; ~ of existir
and additional soil from appro sources, ms shown on the plans.
4.8.3. EQUIPMENT:
(a) General. E(
work shall be on the
be approved by the
beginning
provide
work and its
the opinion
for the
ture or to
the work
necessary for the construction
in first-class and
both as to type and prior to
operations. The CONTRA~ro~ at all
to insure continuous
in the required number of worki~
0WN~R, additional pieces of equipment are
aerating, compacting and finishing
a rate of progress which shall insure corn
required number of working days,
request of the OWNER, immediately secure and place
the required equipment. Any machine, combination of ma-
or equipment which shall pulverize the soil, apply the asphalt,
ATTACHMENT 3.
Amendments and. Revisions to Part III, Construction Method
of the Standard Specifications*
Al. Table of
Part II., Division 4.,
and Base Courses"
Item 4.7. Portland )atment
Item 4.8. Asphalt Tr
Item 4.9. Portlan~ement o.~ of Sub~rade Soils
' Cnt~~dific ' ~~
A2 Portland atiOn of Subgrade Soils. 'It ~m~)~., "Cement
' - - - ' ,, 'NEW ~,,
Modific~on~ of Subgrade Soils (page 263). L ] ,
labor, equipment, fuels, tools and incidentals necessary
[THE FOLLOWING TEXT IS NEW MATERIAL TO BE ADDED
- _ TO THE STANna~ SP£CIF:CAT:C[:£. CnN~TDE~ IT UNDERLINFn]
ete
~'on of Sub rade Soils
4.9.1. Description: This item shall consist of the treating the subgrade
soils by pulverizing, addition of portland cement and water, mixing, and
compacting the mixture to the required density. This item applies to natural
ground or embankment encountered in the construction. The cement-modified soil
layer shall be constructed as specified herein and in conformity with the
typical sections, lines and grades as shown on the plans or as established by
the OWNER.
4.9.2. Materials:
(a) Portland Cement. Cement shall conform to the requirements of Item
2.2.1., "Cement."
(b) Water. Water shall conform to the requirements of Item 2.2.4.,
"Water."
(c) Soil. The soil shall consist of approved soil, free from vegetation
or other objectionable matter. It may be either the material encountered in
the existing section, material secured from approved sources shown on the plans
or as designated by the OWNER, or a combination of existing and additional soil
from approved sources, as shown on the plans, or as directed by the OWNER.
NUIE:
Underlining indicates new words to be added to the Standard Specifica-
tions. Strike-outs indicate existing words and phrases to be deleted.
3.1
4.9.3. Equipment: All equipment necessary to properly prosecute, perform
and complete the work within the contract time, shall be on the project and
shall be approved by the OWNER as to type and condition before the CONTRACTOR
shall be permitted to begin construction operations on which the equipment is
to be used.
The cement-modified soil layer may be constructed wit~ any machine or
combination of machines and auxiliary equipment that shall produce the results
meeting the requirements for soil pulverization, cement application, water
application, mixing, incorporation of materials, compaction, and finishin9 as
specified herein. The CONTRACTUR shall at all times provide sufficient
equipment to enable continuous performance of the work and its completion in
the required number of working days.
4.9.4 Construction Methods:
(al General~ The primary requirement of this specification is to secure
a complete course of treated subgrade material containing a uniform portland
cement mixture, free from loose or segregated areas, of uniform density and
moisture content, well bound and compacted for its full depth with a smooth
surface suitable for placing additional subbase, base or surface courses. It
shall be the responsibility of the CONTRACTOR to regulate the sequence of his
work to process a sufficient quantity of material so as to provide full depth
as shown on plans, to use the proper amount of portland cement, maintain the
work and to rework the courses as necessary to meet the foregoing requirements.
Before other construction operations are begun, the roadbed shall be
graded and shaped as required to construct the portland cement modified
subgrade layer in conformance with the lines, grades, thickness and typical
cross sections shown on the plans. Unsuitable soil or material shall be
removed and replaced with acceptable soil. The subgrade shall be firm and able
to support without displacement the construction equipment and the compaction
hereinafter specified. Soft or yielding sub§rade shall be corrected and made
stable before construction proceeds.
(b) Application of Cement. Portland cement shall be spread uniformly by
an approved dry or slurry method on the soil at the rate specified on the plans
or as determined by preliminary laboratory tests. If a bulk cement spreader is
used, it shall be positioned by string lines or other approved method during
spreading to insure a uniform distribution of cement. Cement shall be applied
only to such an area that all the operations can be continuous and completed in
one operation.
The percentage of moisture in the sub§rade soil at the time of cement
application shall not exceed the quantity that shall permit uniform and
intimate mixture of soil and cement during dry-mixing operations; and it shall
not exceed the specified optimum moisture content f~r the soil and cement
mixture.
No equipment, except that used in the spreading, and mixing, shall be
allowed to pass over the freshly spread cement until it is mixed with the soil.
(c) Mixing and Processing. The mixing procedure shall be the same for
"Dry Placing" or "Slurry Placing" as described herein. The material and cement
shall be thoroughly mixed by approved road mixers or other approved equipment,
3.2
and the mixing shall continue until, in the opinion of the Engineer, a
homogeneous, friable mixture of material and cement is obtained, free from all
clods or lumps. Materials containing plastic clays or other material which
will not readily mix with cement shall be mixed as thoroughly as possible at
the time of the cement application and brought to the proper moisture content.
The material shall be kept moist as directed by the Engineer.
The cement-soil mixture shall meet the following gradation requirements
when tested dry by laboratory sieves:
MinimUm Passing 1" Sieve ................ 100%
Minimum Passing 1/2" Sieve .............. 70%
Minimum Passing No. 4 Sieve .............. 45%
(d) Compaction. Compaction shall begin immediately after final mixing.
The material shall be compacted to 95% of the maximum density, as established,
and in accordance with Test Method Tex 113-E. It shall be aerated or wetted as
necessary to provide optimum moisture. Moisture tolerances shall be as
described below.'
Prior to the beginning of compaction, the mixture shall be in a loose
condition for its full depth. Compaction shall begin at the bottom and shall
continue until the entire depth of the mixture is uniformly compacted.
Description
Density, Percent
Moisture, Percent
For cement treated
subgrade that will
receive subsequent
courses.
Not less than 95,
except when shown
otherwise on the
plans.
Within 2.5 of
optimum unless
otherwise shown
on the plans.
In place density tests shall be as outlined in Test Method Tex 114-E or
Test Method Tex 115-E. In-Place Density tests shall be performed at the rate
of one per 300 linear feet of paving for two (2) lanes. The suitability of the
stabilization shall be confirmed by Atterberg Limit testing at the rate of one
test per 2,500 cubic yards of processed material.
In addition to the requirements specified for density, the full depth of
the material shown on the plans shall be compacted to the extent necessary to
remain firm and stable under construction equipment. After each section is
completed, tests as necessary will be made by the Engineer. If the material
fails to meet the density requirements, it shall be reworked as necessary to
meet these requirements. Throughout this entire operation the shape of the
course shall be maintained by blading, and the surface upon completion shall be
smooth and in conformity with the typical section shown on the plans and to the
established lines and grades. Should the material due to any reason or cause,
loose the stability, density and finish before the next course is placed or the
work is accepted, it shall be ~ecompacted and refinished at the sole expense of
the CONTRACTOR.
(e) Finishing and Preparation for Surfacing. After the final layer or
course of the cement-modified subgrade has been compacted, it shall be brought
to the required lines and grades in accordance with the typical sections. The
3.3
completed section shall then be finished by rolling as directed with a
pneumatic tire or other suitable roller sufficiently light to prevent hair
cracking. Preparation for final surfacing may begin immediately.
4.9.5. Maintenance: The CONTRACTOR shall be required, within the limits
of his Contract, to maintain the cement-modified soil in good condition from
the time he first starts work until all work shal! have been cc:~pleted.
Maintenance shall include immediate repairs of any ~efect that ~y occur after
the cement is applied. Such maintenance work shall be done by ~e CONTRACTOR
at his own expense and repeated as often as necessary to keep the area
continuously intact. Repairs are to be made in such a manner as to insure
restoration of a uniform surface for the full depth of treatment. Any low area
shall be remedied by replacing the material for the full depth of treatment
rather than adding a thin layer of stabilized material to the completed work.
4.9x6. Mea~rement and Payment: This work shall be measured by the square
yard (ML) of complhe, ted and accepted cement-modified soil. Measurement for .
cement shall be by )b~Le ton, 2,000 pounds .(900 kg) of dry weight, as determined
by certified weight t~'~.kets. No allowance shall be made for any materials used
or work done out~ide the~imits as established by the OWNER. The work
,.performed and material fur~shed as prescribed by this item and measured as
provided in this item shall l>q. paid for at the unit price bid for
cement-modified soil, which pr~ shall be full compensation for pulverizing
the soil material; for handling;'lt~uling and spreading the dry or slurry cement
mixture; for mixing the cement with~t~he pulverized soil; furnishing, hauling
and mixing water wi ht the cement-soil'~k~xture; spreading and shaping the
mixture; compacting the mixture, includ~ all rolling required for this
compaction; su~l~hing; and for all'~t~Lanipulation, labor, equipment,
appliances, to~'dentals necessary t~s~complete the work and carry out
the maintenanc~is specificatio'~ Cement material measured as
provided in th~ be paid for at the unf't,.price bid for cement
material, which '~sation for furn~ing the material; for
all freight in~'n and storing; an~for all labor,
equipment, fue~~es~.ary to comp'h~e the work, all in
accordance with the plans and these specifications.
[THE PRECEDING MATERIAL IS NEW AND SHALL BE ADDED TO THE
STANDAJ~D SPECIFICATIONS. CONSIDER IT UNDERLINED.]
Hot-mix Asphaltic Concrete Pavement. Item 5.7.5., "Measur~~
H~~e measured by the ton complete
~~, comput~d.at~,_~_ ~/S.Y. per inch or by the
~(M~) °f the type °r types ii~i in the c°mp~
3.4
~inutes
September 8, 1987
Page 8
Item 16: Consider approval of a final plat and variances for Coppell
High School, at the request of Coppell I.S.D., on property
located approximately 1000 feet west of Denton Tap Road, and
approximately 1300 feet north of Sandy Lake Road.
Date of Planning and Zoning meeting - August 20, 1987
Decision of Planning and Zoning Commission - Approved (6-0)
Planning and Zoning Coordinator Taryon Bowman made the presentation to
the Council. She stated that this is a request of a final plat for
Coppell High School on 49.9 acres of land. Several variances have been
requested such as building height, lighting, parking, parking surface,
and screening wall. The school district has also requested a waiver for
the payment of water and sewer availability fees, sewer contract fees,
water tap fees and construction permit fees. Ail DRC comments have been
addressed, therefore, staff has no objections. Mr. Jim Boughton of
SHWC Architects made the presentation to the Council on behalf of the
applicant. Due to a conflicting function this same night, there was no
one from the Coppell I.S.D. or School Board present. Following
discussion, Councilman Smothermon moved that Council approve the final
plat of Coppell I.S.D. for the Coppell High School and that this
approval be subject to the conditions set forth in the preliminary plat
as reiterated below:
t. That the building height be granted a variance to allow for a
proposed height of the structure to fifty-two feet (52').
2. That the variance on the lighting be approved with the use of a
blinder to cut the sideways spillage of the light onto adjoining
property owners.
That the variance from the required two thousand (2,000) parking
spaces be decreased to one thousand two hundred fifty (1,250).
That five inches (5") of concrete on a prepared subgrade be allowed
for the entire parking area with no gravel parking areas.
at as man trees as_P_p_ssi_bl~eMil--1 b_be left on the
5. ~h ~~fC-~ ein~ constructed on the out~d~ of---
th?___trees al~pg the west property line. Dr. Melvin Gross, who was
in the-fla~ence the night the pre]i~inary plat was approved by
Council, stated that he would be willing to donate any property to
the school that would be required to put this fence on the outside
area of the trees and this fence would also be constructed along
, rn property line up to Oak Trail. The gate to this
the southe .... ~= o=te to this
ould be for emergency use oniy .....
property w ..... J ~ ...... rtv would be considered to
property on the south sl~e.o~ ~?=-[~if~hasts on shrubbery would
be for emergency traffiCu~%ZYr%n%r%~U%~n% ~rom the chain lin~ fence
be followed along the so P P
east to the school's eastern most property line.
~ha the fees be waived as requested and the City Manager enter into
~ t
negotiations with the Coppell I.S.D. for some "in-kind" training of City
employees. M~vor Pro Tem Stanton seconded; motion carried unanimously
with ~avor Pro Tem Stanton, Councilmen Wilkerson, Pettijohn, Morton,
~. motion.
~O±~
Smothermon, Co~z~an and ~' ~= voting in favor of the
COPPELL PUBLIC WORKS
April 19, 1988
TO:
Via:
FROM:
RE:
Alan Ratliff, City Manager
Steve Goram, Director of Public Works
Steve Morton, Public Works Inspector
High School Parking Lot Subgrade
In accordance with the Subdivision Ordinance, Appendix A, page
15, paragraph D.l.a., and page 21, paragraph J., I have required
that the school parking lot and drives be lime stabilized or cement
stabilized. This requirement was specified as far back as the
preliminary review of their construction plan.
On March 9, 1988, Maxim Engineering took samples of pavement subgrade
material. The report dated March 15, 1988 shows soil ranging from
0 - 16 p.i.. (P.I. stands for plastisity index. It is used to
determine soil movement. Soil of p.i. 6 - 12 by our ordinance
is acceptable).
The passing soils are not in the same areas, but randomly scattered.
For example: In each parking lot the soil ranges from 0-8, 1 -
9, 0 - 6 and 90% of all drives failed.
In talking with Maxim, we discussed that the wide range of soils
were due to the massive amount of fill on site which has made the
soil so diverse that they could not guarantee that if another sample
was taken 5 feet away from the ones taken March 9, the sample that
passed would probably fail.
I also asked if from the tests they have compiled could they tell
me where the good soil starts and the bad soil ends. They were
unable to determine as the soils are so random that even a more
extensive sampling of soils would not yeild the line between
acceptable and non-acceptable soils.
The use of cushion sand under paving surfaces is not allowed because:
1. the sand will allow water to be trapped between subgrade and
pavement; 2. the sand migrates leaving air voids; 3. the sand,
when water is trapped in it, pumps out of shrinking cracks; 4.
if the concrete fails (pot holes), sand migrates to the pot hole
leaving air voids under pavement; 5. the majority of cities have
deleted the use of cushion sand under paving surfaces due to the
extensive failures and continual costs and hazards of failing parking
lots due to sand migrating and water trapped under pavement.
I am attaching a copy of Maxim's report and letter from Teague
Nail and Perkins.
This requirement is no suprise to Coppell ISD. This item is shown
on their approved construction plan and appear on the CISD contract
documents, page 003003, and plat approval stipulates minimum of
5" concrete on a prepared subbase.
We are sympathetic with the cost estimate of $140,000.00, but feel
that the tax payer will be better served in the long run by not
having to pay for concrete failure repairs which will potentially
exceed $140,000.00.
Even though the test samples show the site has a few areas with
soil in the allowable range of 6 - 12 p.i., they do not represent
the actual conditions as they exist at present.
SMM/SGG/sm
Additional Streets and Alley Reguirements.
1. Streets and alleys shall be platted and
constructed in accordance with the lhoroughfare
Plan of the Comprehensive Plan or other plans
approved by the City Council, and shall conform
to the following requirements:
a. The'.subgrade on all streets and alleys
shall be thoroughly compacted and proof-
rolled as required. Subgrade material
with a plast'[c~ty index of less than 6 or
.greater than-12 shall be stabilized with
hydrated lime, unless recommended other-
wise by a soils engineer.
Fill material when tested in accordance
with ASTN D-698/THD T-9~ shall be in lifts
compacted to 95% of theoretical density
with a moisture content within 3t of
optimum moisture.
In lieu of the above subgrade requirements
the recommendations of a soils engineering
firm familiar with local conditions may be
substituted.
Appendix A
The pro ~ata cost sha]! be approved by the
City Engineer and shal! be payable
to approval of the plans by the
Engineering Department.
Where a Type A, B, B+, C or D
thoroughfare, or a State Highway, is to be
constructed, the Developer sba1] construct
pav~ng a minimum width of 25 feet, if
deemed necessary by the City Engineer. The
City will reimburse the cost of the excess
width to the Developer who installed the
paving, at the Developer's contract
when City funds become available.
When paving thickness ~n excess of e~ght
(Bi inches is ~equired, the City will
reimburse the Developer for the additional
thickness when funds are
lechn]ca] Specifications. l'he specifica-
tions for materials and workmanship shall
conform to "Standard Specifications for
Public Works Construction," published by
North Central Texas Council of
Governments.
Po~ing Lot~. Parking ]ors for public use
shall be constructed of 6" concrete on o
prepared {lime stobilizedl svbg~ode with
adequate surface drainage. Asphalt
See Sheet ~5, paragraph
not be permitted.
D.l.o.
Append~ x A
21
Maxim Engineers, Inc.
March 15, 1988
C~ppell I.S.D.
c/o ~ Ard~tects
P.O. Box 612087
Dallas, Texas 75261
Paving at Coppell
High School
A representative of Maxim Engineers, Inc. %fas present on March 9, 1988, at
the above referenced project. Samples of the pavement subgrade material
were obtained at eleven locations and brought to our laboratory. Atterberg
T.{~lits a~d Peroent Passing No. 200 Sieve Tests were performed on all the
samples. ~ne results are as follows:
Sample #:
Sample Location:
Sample Description:
Liquid T,~mit:
Plastic Limit:
Plasticity Index:
Percent PassingNo. 200 Sieve
1
See attached plan
Light brown silty sand
Non-plastic
20
Sample #:
Sample Location:
Sample Description:
Liquid T.i mit:
Plastic Limit:
Plasticity Index:
Percent Passing No.200 Sieve
2
See attached plan
D~rk gr~y silty sandy clay
33
17
16
64
23~:2 ~-aoens
Box 59902
?.'? as Te x a,.-}
, &
~ I.S.D.
15, L988
Pa~2
Sample #:
Sample Location:
Sample Description:
Liquid Limit:
Plastic Limit:
Plasticity Index:
Percent Passing No.200 Sieve
3
See attached plan
Olive brown silty clayey sand
30
Sample #:
Sample Location:
Sample Description:
Liquid Limit:
Plastic Limit:
Plasticity Index:
Percent Passing No.200 Sieve
4
See attached plan
Yellc~ish brc~n silty
clay balls
13
12
16
sand with few
Sample #:
Sample Location:
Sample Description:
Liquid Limit:
Plastic T.~mit:
Plasticity Index:
Peroent Passing No.200 Sieve
5
See attached plan
Olive brown silty clayey sand
23
14
r.~
Sample #:
Sample Location:
Sample Description:
Liquid T,~ mit:
Plastic T,4 mit:
Plasticity Index:
Percent Passing No.200 Sieve
6
See attached plan
Reddish brown and
sand
26
~5
light brown clayey
Sample #:
SamPle LOCation:
Sample Description:
Liquid T,imit:
Plastic ?.~mit:
Plasticity Index:
Percent Passing No.200 Sieve
7
See attached plan
Light brown sand with few clay balls
18
22
Maxim Engineers, Inc.
Sample #:
Sample Location:
Sample Description:
Liquid T.~mit:
Plastic Limit:
Plasticity Index:
Percent Passir~ No.200 Sieve
8
See attac~ed plan
Light brown silty sand
Sample #:
Sample Location:
Sample Description:
Liquid Limit:
Plastic Limit:
Plasticity Index:
Percent Passing No.200 Sieve
9
See attached plan
D~rk brown clayey sand
25
34
Sample #:
Sample Location:
Sample Description:
Liquid v,~it:
Plastic Limit:
Plasticity Index:
Percent Passing No.200 Sieve
10
See attached plan
Light brown silty clayey sand
21
13
8
35
Sample #:
Sample Location:
Sample Description:
Liquid Limit:
Plastic Limit:
Plasticity Index:
Percent Passing No.200 Sieve
11
See attached plan
Light brown sand
N~plastic
15
Based on these results, we recx.amt,end, that the subgrade, in areas where non-
plastic or material with less than 20 percent passing a No. 200 sieve are
present, be s~ahilized with the addition of 3 to 4 percent cement by dry
weight of soil (14 to 18 pounds per square yard). ~ne subgrade in the
r~ain~ area should be scarified and compa~ to a m/nimum density of 95
percent at a moisture content within three (3) percent of the optimum
moisture content as determined by the Standard Proctor Test (AS~4 E~698).
The cement st~_bilization should be performed in accordance with the
applicable Tewa~ State Department of Highways and Public Transportation
specifications.
Maxim Engineers, Inc.
~ I.S.D.
~rch 15, 1988
We trust the information provided is sufficient for your use. Please
contact us if you need any additional information or if we may be of further
service.
Very Truly Yours,
Saad M. Hineidi, P.E.
Executive Vice President
Enclosures
SHWC, Inc. - Michael Elmore
Coppell I.S.D. - Mickey Harper
Teague, Nall& Perkins, Inc. - Tom Rutledge
City of Coppell - Steve Morton
Maxim Engineers, Inc.
COPPELL HIGH SCHOOL.
COPfl~.L L~,.D. ,'