geotechnical and pavement sections brighton school ... improvements thornton, colorado final...

Geotechnical and Pavement Sections Brighton School District 27J High School #3

Off-site Improvements Thornton, Colorado

Final Submittal Revised

Prepared for:

Brighton School District 27J 630 S. 8th Avenue

Brighton, Colorado 80601

Attention: Ms. Ranette Carlson

Job Number: 16-3500 March 28, 2016

TABLE OF CONTENTS

Page

Purpose and Scope of Study ........................................................................................ 1

Proposed Construction .................................................................................................. 1

Alignment Conditions .................................................................................................... 2

Subsurface Exploration .................................................................................................. 2

Laboratory Testing ......................................................................................................... 3

Subsurface Conditions ................................................................................................... 4

Culvert Foundation System ............................................................................................... 4

Lateral Earth Pressures .................................................................................................... 7

Water Soluble Sulfates ...................................................................................................... 8

Soil Corrosivity ................................................................................................................ 10

Project Earthwork ............................................................................................................ 13

Excavation Considerations .............................................................................................. 17

Utility Pipe Installation and Backfilling ............................................................................. 18

Frost Heave ..................................................................................................................... 21

Pavement Sections ...................................................................................................... 21

Closure .......................................................................................................................... 27

Site Vicinity Map ...................................................................................................Figure 1A

Typical Site Soils ..................................................................................................Figure 1B

Typical Site Pavement ........................................................................................ Figure 1C

Logs of Test Holes .......................................................................................... Figures 2-7

Legend and Notes ................................................................................................ Figure 8

Swell-Consolidation Testing ............................................................................ Figures 9-20

Resilient Modulus Test Results ..................................................................... Figures 21-23

Hydrometer Test Results .............................................................................. Figures 24-30

Compaction Test Results .............................................................................. Figures 31-33

Summary of Laboratory Test Results .................................................................... Table 1

Summary of Soil Corrosion Results ........................................................................ Table 2

Pavement Section Calculations .................................................................... Appendix A

High School #3 Off-site Improvements Brighton School District 27J

Thornton, Colorado Final Submittal

Revised

Job No. 16-3500 GROUND Engineering Consultants, Inc. Page 1

PURPOSE AND SCOPE OF STUDY

This report presents the results of a subsurface exploration program performed by

Ground Engineering Consultants, Inc. (GROUND), for the construction of the proposed

off-site improvements associated with the future construction of High School #3 in

Thornton, Colorado. Our study was conducted in general accordance with GROUND’s

proposal number 1512-2348 Revised, dated December 29, 2015.

A field exploration program was conducted to obtain information on subsurface

conditions. Material samples obtained during the subsurface exploration were tested in

the laboratory to provide data on the classification and engineering characteristics of the

on-site soils. The results of the field and laboratory studies are presented herein.

This report has been prepared to summarize the data obtained and to present our

conclusions and parameters based on the proposed construction and the subsurface

conditions encountered. Design parameters and a discussion of geotechnical

engineering considerations related to the proposed improvements are included.

PROPOSED CONSTRUCTION

Based on the information provided, we understand that the proposed development will

consist of roadway widening and reconstruction within 136th Avenue, Yosemite Street,

and the Yosemite Street/Riverdale Road intersection. The proposed roadways will

range from approximately 24 feet to 45 feet in width with 3-foot wide shoulders. Total

roadway reconstruction length appears to the approximately 7,500 linear feet. Concrete

sidewalks will also be constructed on both sides of the project roadways. Localized mill

and overlay is being considered for roadway tie-ins. Additionally, the installation of

underground utilities, a culvert system within Yosemite Street, and a potential cast-in-

place structure associated with a pressure reducing valve/facility (PRV) are also planned

for construction. Utility depths are anticipated to be approximately 10 to 15 feet below

the final roadway surface with a few locations toward the south end of Yosemite Street

being approximately 20 feet in depth. If the proposed construction differs significantly

from that described above, GROUND should be notified to re-evaluate the parameters

contained herein.



Revised


ALIGNMENT CONDITIONS

At the time of our exploration, the

proposed roadway alignments

appeared to be near rough final

grades. Underground utilities

including gas and sewer lines as well

as overhead power were associated

with the project site. Asphalt

pavement was associated with 136th

Avenue east of Yosemite Street and

Riverdale Road, south of Yosemite

Street. Based on our exploration,

asphalt thicknesses ranging from

approximately 3 to 6 inches were

observed on 136th Avenue and an

asphalt thickness of approximately 7

inches was observed near the

intersection of Yosemite Street and

Riverdale Road. The general project

area currently accommodates a few

residential properties. The general

topography across the site ranged from 2 to 8 percent generally descending toward the

south (Yosemite) and to the east (136th Avenue).

Man-made fill was encountered in some of the test holes at the time of drilling. The

exact extents, limits, and composition of any man-made fill were not determined as part

of the scope of work addressed by this study, and should be expected to potentially exist

at varying depths and locations across the site.



Revised


SUBSURFACE EXPLORATION

The subsurface exploration for the project was conducted on January 15 and 21, 2016.

Twenty-seven (27) test holes were drilled within the proposed alignments at approximate

250-foot linear spacing (per the City of Thornton specifications). The test holes

extended to depths of approximately 10 to 20 feet below existing grades. The test holes

were drilled with a truck-mounted, continuous flight power auger rig to evaluate the

subsurface conditions as well as to retrieve soil and bedrock samples for laboratory

testing and analysis. A representative of GROUND directed the subsurface exploration,

logged the test holes in the field, and prepared the soil and bedrock samples for

transport to our laboratory.

Samples of the subsurface materials were taken with 2-inch I.D. California-type liner

sampler. The sampler was driven into the substrata with blows from a 140-pound

hammer falling 30 inches. This procedure is similar to the Standard Penetration Test

described by ASTM Method D1586. Penetration resistance values (blows per distance

driven, typically 12 inches), when properly evaluated, indicate the relative density or

consistency of soils. Composite disturbed (bulk) samples of the shallow soils were

collected from the pavement test hole auger returns. Depths at which the samples were

taken, and associated penetration resistance values are shown on the test hole logs.

The approximate locations of the test holes are shown in Figure 1. Logs of the

exploratory test holes are presented in Figures 2 through 7. Explanatory notes and a

legend are provided in Figure 8. The test holes locations were determined by the Client

on a provided site plan.

LABORATORY TESTING

Samples retrieved from our test holes were examined and visually classified in the

laboratory by the project engineer. Laboratory testing of soil and bedrock samples

obtained from the subject site included standard property tests, such as natural moisture

contents, dry unit weights, grain size analyses, liquid and plastic limits, swell-

consolidation testing, water-soluble sulfate contents, and soil corrosivity testing.

Resilient modulus testing was also performed on the composite bulk samples obtained

from the auger cuttings. Laboratory tests were performed in general accordance with



Revised


applicable ASTM protocols. Results from the laboratory-testing program are

summarized on Table 1. Swell-consolidation test results are presented in Figures 9

through 20 and hydrometer test results are presented in Figures 24 through 30.

Resilient modulus test results are presented in Figures 21 through 23 and compaction

test results are presented in Figures 31 through 33.

SUBSURFACE CONDITIONS

The subsurface conditions encountered generally consisted of sand and clay. These

materials were underlain by claystone bedrock encountered at depths ranging from

approximately 4 to 12 feet below existing grades. The test holes extended to depths

ranging from approximately 10 to 20 feet below existing grade. A thin veneer of asphalt

was associated with a few of the test holes, ranging in thickness from approximately 3 to

7 inches.

Man-Made Fill was generally comprised of sandy clay, was medium plastic, fine to

coarse grained, slightly moist to moist, and brown in color.

Sand and Clay were interbedded, low to highly plastic, fine to coarse grained with

gravels, stiff/medium dense to hard/very dense, dry to moist, occasionally calcareous,

somewhat iron stained and brown/tan to gray in color.

Claystone Bedrock was sandy, medium to highly plastic, fine to medium grained, hard

to very hard and relatively resistant, slightly moist to moist, occasionally iron stained, and

olive to brown in color.

Swell-Consolidation Testing indicated a potential for heave and consolidation in the

tested on-site materials tested. Swells of approximately 0.1 to 4.7 percent and

consolidations of approximately 0.1 to 0.5 percent were measured upon wetting against

a surcharge load of 150 psf (City of Thornton – Standards and Specifications, 503.7A.j).

Swell-consolidation test results are provided in Table 1 and Figures 9 through 20.

Groundwater was encountered in Test Holes 1 and 22 at the time of drilling at depths of

approximately 14½ and 18 feet below existing grade, respectively. The test holes were

backfilled immediately following drilling operations for safety. Groundwater levels should



Revised


be anticipated to fluctuate, however, in response to annual and longer-term cycles of

precipitation, applied irrigation, and surface drainage.

CULVERT FOUNDATION SYSTEM

According to representatives of the project team, a culvert system may be installed

within Yosemite Street. Additionally, a cast-in-place concrete structure that will

accommodate a PRV for the proposed waterline will also be installed. Final

depths/elevations of the proposed culvert/concrete system or actual construction type

were unknown at the time of this report preparation. This information should be provided

to GROUND for review in order to evaluate the parameters provided herein.

Based on the results of our field and laboratory testing program, a potential for heave is

present in the site earth materials. Even so, our experience suggests that these

structures often have a greater tolerance for movement and when movement does

occur, the movement often tends to not appear as severe as that observed in other

types of structures, i.e., a building. Additionally, up to approximately 6 feet of existing fill

material was observed within the test holes, likely associated with the existing utility

trenches. Deeper depths of man-made fill may exist on-site. It is unknown if these fill

soils were documented during placement (compaction testing). Ideally, undocumented

fill material should be removed and replaced as properly compacted fill. However, as

indicated above, we understand that these types of structures are often more tolerant to

movement and the removal and replacement of observed fill soils are often deemed

impractical or uneconomical. Therefore, the proposed culvert/concrete structures may

be constructed using a shallow foundation system bearing on the fill soils or native earth

materials provided that at least 12 inches of subgrade beneath the proposed structures

are scarified and re-compacted as outlined in the Project Earthwork section of this

report. The City of Thornton should be consulted as to whether they possess istorical

data regarding these fill soils.


approximately 14½ and 18 feet below existing grade, respectively. Even so,

groundwater levels may fluctuate with the season. Therefore, depending on final

grades, groundwater may be encountered in deep excavations. The contractor should

be prepared to dewater the excavation during construction.



Revised


The geotechnical parameters indicated below may be used for design of shallow

foundations for the proposed culvert/concrete structure.

Geotechnical Parameters for Shallow Foundation Design

(1) Footings/foundations bearing on at least 12 inches of properly moisture-density

treated materials may be designed for an allowable soil bearing pressure of 2,000

psf. Based on this allowable bearing pressure, we anticipate post-construction

settlements to be on the order of 1 inch.

Compression of the bearing soils for the provided allowable bearing pressure is

estimated to be 1 inch, based on an assumption of drained foundation conditions.

If foundation soils are subjected to an increase/fluctuation in moisture content, the

effective bearing capacity will be reduced and greater post-construction

movements than those estimated above may result.

This estimate of foundation movement from direct compression of the foundation

soils is in addition to movements from expansive soils heave and/or collapse of

hydro-compressive soils.

To reduce differential settlements between foundation elements, footing loads

should be as uniform as possible. Differentially loaded footings will settle

differentially.

(2) Footings/foundations should have a minimum dimension of 14 or more inches.

Actual dimensions, however, should be determined by the Structural Engineer,

based on the design loads.

(3) Footings/foundations should bear at an elevation 3 or more feet below the lowest

adjacent exterior finish grades to have adequate soil cover for frost protection

(4) The lateral resistance of footings/foundations will be developed as sliding

resistance of the footing bottoms on the foundation materials and by passive soil

pressure against the sides of the footings/foundations. Sliding friction at the

bottom of footings/foundations may be taken as 0.27 times the vertical dead load.



Revised


(5) Connections of all types must be flexible and/or adjustable to accommodate the

anticipated, post-construction movements.

Shallow Foundation Construction

(6) The contractor should take adequate care when making excavations not to

compromise the bearing or lateral support for nearby improvements.

(7) Care should be taken when excavating the foundations to avoid disturbing the

supporting materials particularly in excavating the last few inches.

(8) All unsuitable including but not limited to saturated, near-saturated, muck-like or

yielding bearing materials exposed at the bottom of the excavation should be

excavated and replaced with properly moisture conditioned and compacted fill in

accordance with the Project Earthwork section of this report, or the excavation

deepened to adequate earth materials. Use of controlled low strength material

(CLSM), i.e., a lean sand-cement slurry, flowable fill, or a similar material in lieu of

compacted soil backfill in these locations may be beneficial where access is

restricted or when it can be placed more rapidly than properly compacted soil fill.

As stated, placement of a layer of crushed rock at the bottom of the excavation to

achieve and maintain a stable working platform should be considered. A layer of

geotextile between the crushed rock and on-site soils should also be considered.

(9) Foundation-supporting soils may be disturbed or deform excessively under the

wheel loads of heavy construction vehicles as the excavations approach footing

bearing levels. Construction equipment should be as light as possible to limit

development of this condition. The movement of vehicles over proposed

foundation areas should be restricted.

(10) All foundation subgrade should be properly cleaned/compacted so no loose soils

remain, prior to placement of concrete.

(11) As necessary, fill placed against the sides of the footings/foundations should be

properly compacted in accordance with the Project Earthwork section of this report.



Revised


LATERAL EARTH PRESSURES

The at-rest, active, and passive earth pressures in terms of equivalent fluid unit weight

for the on-site backfill are summarized on the table below. The use of passive pressure

under a saturated condition is not recommended. The values or the on-site sand

material and clay/silt were approximated utilizing a unit weight of 124 pcf and a phi angle

of 22 degrees. The values below are unfactored. Appropriate factors of safety should

be included in the design.

Lateral Earth Pressures (Equivalent Fluid Unit Weights)

Material Type Water

Condition

At-Rest

(pcf)

Active

(pcf)

Passive

(pcf)

Friction

Coefficient

On-Site Sand and Clay Backfill

Drained 77 56 270 0.27

Submerged 100 90 - 0.27

Structure Backfill

Drained 55 35 400 0.45

Submerged 90 80 -- 0.45

WATER-SOLUBLE SULFATES

The concentrations of water-soluble sulfates measured in selected samples obtained

from the test holes were approximately 0.01 to 0.34 percent. Such concentrations of

water-soluble sulfates represent a negligible to severe environment for sulfate attack on

concrete exposed to these materials. Degrees of attack are based on the scale of

‘negligible,’ ‘moderate,’ ‘severe’ and ‘very severe’ as described in the “Design and

Control of Concrete Mixtures,” published by the Portland Cement Association (PCA).

The Colorado Department of Transportation (CDOT) utilizes a corresponding scale with

4 classes of severity of sulfate exposure (Class 0 to Class 3) as described in the

published table below.



Revised


REQUIREMENTS TO PROTECT AGAINST DAMAGE TO

CONCRETE BY SULFATE ATTACK FROM EXTERNAL SOURCES OF SULFATE

Severity of Sulfate

Exposure

Water-Soluble Sulfate (SO4)

In Dry Soil (%)

Sulfate (SO4) In Water

(ppm)

Water Cementitious

Ratio (maximum)

Cementitious Material

Requirements

Class 0 0.00 to 0.10 0 to 150 0.45 Class 0

Class 1 0.11 to 0.20 151 to 1500 0.45 Class 1

Class 2 0.21 to 2.00 1501 to 10,000 0.45 Class 2

Class 3 2.01 or greater 10,001 or greater 0.40 Class 3

Based on our test results and PCA and CDOT guidelines, GROUND recommends use of

sulfate-resistant cement in all concrete exposed to site soil and bedrock, conforming to

one of the following Class 2 requirements:

(1) ASTM C 150 Type V with a minimum of a 20 percent substitution of Class F fly

ash by weight

(2) ASTM C 150 Type II or III with a minimum of a 20 percent substitution of Class F

fly ash by weight. The Type II or III cement shall have no more than 0.040

percent expansion at 14 days when tested according ASTM C 452

(3) ASTM C 1157 Type HS; Class C fly ash shall not be substituted for cement.

(4) ASTM C 1157 Type MS plus Class F fly ash where the blend has less than 0.05

percent expansion at 6 months or 0.10 percent expansion at 12 months when

tested according to ASTM C 1012.

(5) A blend of Portland cement meeting ASTM C 150 Type II or III with a minimum of

20 percent Class F fly ash by weight, where the blend has less than 0.05 percent

expansion at 6 months or 0.10 percent expansion at 12 months when tested

according to ASTM C 1012.

(6) ASTM C 595 Type IP(HS); Class C fly ash shall not be substituted for cement.



Revised


When fly ash is used to enhance sulfate resistance, it shall be used in a proportion

greater than or equal to the proportion tested in accordance to ASTM C 1012, shall be

the same source, and it shall have a calcium oxide content no more than 2.0 percent

greater than the fly ash tested according to ASTM C 1012.

All concrete exposed to site soil and bedrock should have a minimum compressive

strength of 4,500 psi.

The contractor should be aware that certain concrete mix components affecting sulfate

resistance including, but not limited to, the cement, entrained air, and fly ash, can affect

workability, set time, and other characteristics during placement, finishing and curing.

The contractor should develop mix(es) for use in project concrete which are suitable with

regard to these construction factors, as well as sulfate resistance. A reduced, but still

significant, sulfate resistance may be acceptable to the owner, in exchange for desired

construction characteristics.

SOIL CORROSIVITY

The degree of risk for corrosion of metals in soils commonly is considered to be in two

categories: corrosion in undisturbed soils and corrosion in disturbed soils. The potential

for corrosion in undisturbed soil is generally low, regardless of soil types and conditions,

because it is limited by the amount of oxygen that is available to create an electrolytic

cell. In disturbed soils, the potential for corrosion typically is higher, but is strongly

affected by soil chemistry and other factors.

A preliminary corrosivity analysis was performed to provide a general assessment of the

potential for corrosion of ferrous metals installed in contact with earth materials at the

site, based on the conditions existing at the time of GROUND’s evaluation. Soil

chemistry and physical property data including pH, reduction-oxidation (redox) potential,

and sulfides content were obtained. Test results are summarized on Table 2.

pH Where pH is less than 4.0, soil serves as an electrolyte; the pH range of about 6.5 to

7.5 indicates soil conditions that are optimum for sulfate reduction. In the pH range

above 8.5, soils are generally high in dissolved salts, yielding a low soil resistivity

(AWWA, 2010). Testing indicated pH values of approximately 8.7 to 9.0.



Revised


Reduction-Oxidation testing indicated negative potentials: -102 to -118 millivolts. Such

low potentials typically create a more corrosive environment.

Sulfide Reactivity testing for the presence of sulfides indicated ‘trace’, ‘negative’ and

‘positive’ results. The presence of sulfides in the site soils also suggests a more

corrosive environment.

Soil Resistivity In order to assess the “worst case” for mitigation planning, samples of

materials retrieved from the test holes were tested for resistivity in the in the laboratory,

after being saturated with water, rather than in the field. Resistivity also varies inversely

with temperature. Therefore, the laboratory measurements were made at a controlled

temperature.

Measurements of electrical resistivity indicated values of approximately 778 to 4,693

ohm-centimeters in samples of the site earth materials. The following table presents the

relationship between soil resistivity and a qualitative corrosivity rating (ASM, 2003)1.

Corrosivity Ratings Based on Soil Resistivity

Soil Resistivity (ohm-cm)

Corrosivity Rating

>20,000 Essentially non-corrosive

10,000 – 20,000 Mildly corrosive

5,000 – 10,000 Moderately corrosive

3,000 – 5,000 Corrosive

1,000 – 3,000 Highly corrosive

<1,000 Extremely corrosive

Corrosivity Assessment The American Water Works Association (AWWA, 20102) has

developed a point system scale used to predict corrosivity. The scale is intended for

protection of ductile iron pipe but is valuable for project steel selection. When the scale

equals 10 points or higher, protective measures for ductile iron pipe are suggested. The

1 ASM International, 2003, Corrosion: Fundamentals, Testing and Protection, ASM Handbook, Volume 13A. 2 American Water Works Association ANSI/AWWA C105/A21.5-05 Standard.



Revised


AWWA scale (Table A.1 Soil-test Evaluation) is presented below. The soil characteristics

refer to the conditions at and above pipe installation depth.

Table A.1 Soil-test Evaluation

Soil Characteristic / Value Points

Resistivity <1,500 ohm-cm ..........................................................................................… 10 1,500 to 1,800 ohm-cm ................................................................……......…. 8 1,800 to 2,100 ohm-cm .............................................................................…. 5 2,100 to 2,500 ohm-cm ...............................................................................… 2 2,500 to 3,000 ohm-cm .................................................................................. 1 >3,000 ohm-cm ................................................................................… 0 pH 0 to 2.0 ............................................................................................................ 5 2.0 to 4.0 ......................................................................................................... 3 4.0 to 6.5 ......................................................................................................... 0 6.5 to 7.5 ......................................................................................................... 0 * 7.5 to 8.5 ......................................................................................................... 0 >8.5 .......................................................................................................... 3

Redox Potential < 0 (negative values) ....................................................................................... 5 0 to +50 mV ................................................................................................…. 4 +50 to +100 mV ............................................................................................… 3½ > +100 mV ............................................................................................... 0

Sulfide Content Positive ........................................................................................................…. 3½ Trace .............................................................................................................… 2 Negative .......................................................................................................…. 0

Moisture Poor drainage, continuously wet ..................................................................…. 2 Fair drainage, generally moist ....................................................................… 1 Good drainage, generally dry ........................................................................ 0

* If sulfides are present and low or negative redox-potential results (< 50 mV) are

obtained, add three points for this range.

The redox potential of a soil is significant, because the most common sulfate-reducing

bacteria can only live in anaerobic conditions. A negative redox potential indicates

anaerobic conditions in which sulfate reducers thrive. A positive sulfide reaction reveals

a potential problem caused by sulfate-reducing bacteria. Anaerobic conditions are

regarded as potentially corrosive.



Revised


Based on a maximum possible score of 25.5 using the AWWA method, the value of 10

for the use of corrosion protection, and scores of approximately 11.5 to 21.5 in the on-

site soil, the soil appears to comprise a moderate to highly corrosive environment for

buried metals.

If additional information is needed regarding soil corrosivity, the American Water Works

Association or a Corrosion Engineer should be contacted. It should be noted, however,

that changes to the site conditions during construction, such as the import of other soils,

or the intended or unintended introduction of off-site water, may significantly alter

corrosion potential.

PROJECT EARTHWORK

The following information is for private improvements; public roadways or utilities

should be constructed in accordance with City of Thornton standards.

Prior to earthwork construction, existing vegetation, topsoil, asphalt, concrete, and other

deleterious materials should be removed and disposed of off-site. Relic underground

utilities, if encountered, should be abandoned in accordance with applicable regulations,

removed as necessary, and capped at the margins of the property. The Geotechnical

Engineer should be contracted to test the excavation backfill during placement.

Topsoil should not be incorporated into fill placed on the site. Instead, topsoil should be

stockpiled during initial grading operations for placement in areas to be landscaped or

for other approved uses.

Existing Fill Soils: Man-made fill was encountered in some of the test holes at the time

of drilling. Actual contents and composition of all aspects of the man-made fill materials

are not known; therefore, some of the excavated man-made fill materials may not be

suitable for replacement as backfill. The Geotechnical Engineer should be retained

during site excavations to observe the excavated fill materials and provide guidance for

its suitability for reuse.

Imported Fill Materials: If it is necessary to import material to the site, the imported

soils should be free of organic material, and other deleterious materials. Imported

material should consist of relatively impervious soils that have less than 60



Revised


percent passing the No. 200 Sieve and should have a plasticity index less than 20.

Representative samples of the materials proposed for import should be tested and

approved prior to transport to the site.

Use of Existing Native Soils: Overburden soils that are free of trash, organic material,

construction debris, and other deleterious materials are suitable, in general, for

placement as compacted fill. Organic materials should not be incorporated into project

fills.

Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt)

larger than 3 inches in maximum dimension will require special handling and/or

placement to be incorporated into project fills. In general, such materials should be

placed as deeply as possible in the project fills. A Geotechnical Engineer should be

consulted regarding appropriate information for usage of such materials on a case-by-

case basis when such materials have been identified during earthwork. Standard

parameters that likely will be generally applicable can be found in Section 203 of the

current CDOT Standard Specifications for Road and Bridge Construction.

Reconditioning Expansive Earth Materials: Expansive materials were observed in the

test holes and include swell potentials up to 4.7 percent, measured against a 150 psf

surcharge pressure. Higher swell potentials could exist on-site. In the Denver Metro

area, these materials have been excavated and replaced with variable success due to

the natural properties of highly expansive materials as well as poorly controlled materials

processing and varying placement techniques. The Client, Owner, and Contractor must

understand that expansive bedrock will require additional processing including but not

limited to stockpile moisture conditioning and multiple sub-excavations including partial

to complete removal of previously moisture conditioned and compacted fill materials.

The following parameters will not eliminate post-construction movement associated with

structures/utility trenches/improvements constructed on expansive soils and bedrock, but

may tend to make movements more uniform.

Excavated materials will require a well-coordinated effort to moisture treat, process,

place, and compact properly. In-place bedrock deposits were hard to relatively resistant

and relatively dry, and require a significant volume of water to be mixed into the

excavated material to bring them to a uniform moisture content from optimum to 3



Revised


percent above the optimum prior to compaction. The daily moisture content in the tested

fill should be between 2 and 3 percent above the optimum as an additional requirement.

Bedrock fragments should be reduced so as to achieve a soil-like mass. Adequate

watering, and compaction equipment that aids in breaking down the material (e.g., a

Caterpillar 825 compactor-roller), likely will be needed. Excavated bedrock will require

additional moisture conditioning and processing in an open area outside of utility

trenches prior to placement as backfill.

Fill Platform Preparation: Prior to filling, the top 8 to 12 inches of in-place materials on

which fill soils will be placed should be scarified, moisture conditioned and properly

compacted in accordance with the parameters below to provide a uniform base for fill

placement.

If surfaces to receive fill expose loose, wet, soft or otherwise deleterious material,

additional material should be excavated, or other measures taken to establish a firm

platform for filling. The surfaces to receive fill must be effectively stable prior to

placement of fill.

Wet, Soft or Unstable Subgrades Where wet, soft or unstable subgrades are

encountered, the contractor should establish a firm, stable platform for fill placement and

compaction. Excavation of the unstable soils and replacing them with coarse granular

material or relatively dry soil, possibly together with the use of stabilization geo-textile or

geo-grid, may be necessary to achieve stability. Whereas the stabilization approach

should be determined by the contractor, GROUND offers the alternatives below for

consideration. Proof-rolling can be beneficial for identifying unstable areas.

Replacement of the existing subgrade soils with clean, coarse, aggregate (e.g.,

crushed rock or “pit run” materials) or with road base. Excavation and replacement

to a depth of 1 to 2 feet commonly is sufficient, but greater depths may be necessary

to establish a stable surface.

On very weak subgrades, an 18- to 24-inch “pioneer” lift that is not well compacted

may be beneficial to stabilize the subgrade. Where this approach is employed,

however, additional settlements of ½ inch may result.



Revised


Where coarse, aggregate alone does not appear sufficient to provide stable

conditions, it can be beneficial to place a layer of stabilization geo-textile or geo-grid

(e.g., Tencate Mirafi® HP370 or RS 380i, or Tensar® BX 1100) at the base of the

aggregate section.

The stabilization geo-textile / geo-grid should be selected based on the aggregate

proposed for use. It should be placed and lapped in accordance with the

manufacturer’s recommendations.

Geo-textile or geo-grid products can be disturbed by the wheels or tracks of

construction vehicles. We suggest that appropriate care be taken to maintain the

effectiveness of the system. Placement of a layer of aggregate over the geo-textile /

geo-grid prior to allowing vehicle traffic over it can be beneficial in this regard.

When a given remedial approach has been selected, GROUND recommends

constructing a test section to evaluate the effectiveness of the approach prior to use over

a larger area.

Fill Placement: Fill materials should be thoroughly mixed to achieve a uniform moisture

content, placed in uniform lifts not exceeding 8 inches in loose thickness, and properly

compacted.

Soils that classify as A-1 through A-3 should be compacted to 95 percent of the

maximum modified Proctor dry density at moisture contents within 2 percent of optimum

moisture content as determined by AASHTO T-180.

Soils that classify as A-4 through A-7 should be compacted to 95 percent of the

maximum standard Proctor density at moisture contents from 1 percent below to 3

percent above the optimum as determined by AASHTO T-99.

No fill materials should be placed, worked, rolled while they are frozen, thawing, or

during poor/inclement weather conditions.

Care should be taken with regard to achieving and maintaining proper moisture contents

during placement and compaction. Materials that are not properly moisture conditioned

may exhibit significant pumping, rutting, and deflection at moisture contents near



Revised


optimum and above. The contractor should be prepared to handle soils of this type,

including the use of chemical stabilization, if necessary.

Compaction areas should be kept separate, and no lift should be covered by another

until relative compaction and moisture content within the suggested ranges are obtained.

EXCAVATION CONSIDERATIONS

The test holes for the subsurface exploration were excavated to the depths indicated by

means of truck-mounted, flight auger drilling equipment. Practical drill rig refusal was not

encountered at the time of subsurface exploration, however, very hard and resistant

bedrock was encountered. We anticipate that excavation into the bedrock will be slow

even with conventional, heavy duty, excavating equipment, and will entail greater than

typical wear on the equipment used.

Some excavation difficulties are anticipated, however. These may include the following:

The presence of claystone formational bedrock. Significant processing and

moisture conditioning of claystone formational bedrock may be needed prior to

incorporation in project fills (see Project Earthwork section). It is possible that

sandstone bedrock possessing varying degrees of cementation may also be

encountered.

Temporary, un-shored excavation slopes up to 10 feet in height be cut no steeper than

1½:1 (horizontal : vertical) in the site soils in the absence of seepage. Sloughing on the

slope faces should be anticipated at this angle. Local conditions encountered during

construction, such as groundwater seepage and loose sand, will require flatter slopes.

Stockpiling of materials should not be permitted closer to the tops of temporary slopes

than 5 feet or a distance equal to the depth of the excavation, whichever is greater.

Should site constraints prohibit the use of the slope angles, temporary shoring should be

used. The shoring should be designed to resist the lateral earth pressure exerted by

building, traffic, equipment, and stockpiles.


approximately 14½ and 18 feet below existing grade, respectively. Therefore,



Revised


groundwater may be encountered during utility excavations and should be anticipated by

the contractor. A properly designed and installed de-watering system may be required

during the construction. The risk of slope instability will be significantly increased in

areas of seepage along the excavation slopes. If seepage or groundwater is

encountered during excavation, the Geotechnical Engineer should evaluate the

conditions and provide additional parameters as appropriate.

Good surface drainage should be provided around temporary excavation slopes to direct

surface runoff away from the slope faces. A properly designed drainage swale should

be provided at the top of the excavations. In no case should water be allowed to pond at

the site. Slopes should also be protected against erosion. Erosion along the slopes will

result in sloughing and could lead to a slope failure.

Excavations in which personnel will be working must comply with all OSHA Standards

and Regulations. The Contractor’s “responsible person” should evaluate the soil

exposed in the excavations as part of the Contractor’s safety procedures. GROUND has

provided the information above solely as a service to the Client, and is not assuming

responsibility for construction site safety or the Contractor’s activities.

UTILITY PIPE INSTALLATION AND BACKFILLING

As stated, groundwater was encountered in Test Holes 1 and 22 at the time of drilling at

depths of approximately 14½ and 18 feet below existing grade, respectively. Therefore,

groundwater could potentially be a significant factor in utility excavations in some areas,

and should be anticipated by the contractor. The contractor should be prepared to

dewater the excavation to provide a stable platform prior to the installation of the pipe

and bedding materials.

Pipe Support: The bearing capacity of the site soils appeared adequate, in general, for

support of anticipated water lines. The pipe + water are less dense than the soils which

will be displaced for installation. Therefore, GROUND anticipates no significant pipe

settlements in these materials where properly bedded.

Excavation bottoms may expose soft, loose or otherwise deleterious materials, including

debris. Firm materials may be disturbed by the excavation process. All such unsuitable

materials should be excavated and replaced with properly compacted fill. Areas allowed



Revised


to pond water will require excavation and replacement with properly compacted fill. The

contractor should take particular care to ensure adequate support near pipe joints which

are less tolerant of extensional strains.

Where thrust blocks are needed, they may be designed for an allowable passive soil

pressure of 270 psf per foot of embedment, to a maximum of 2,700 psf. Sliding friction

at the bottom of thrust blocks may be taken as 0.27 times the vertical dead load.

Trench Backfilling: Some settlement of compacted soil trench backfill materials should

be anticipated, even where all the backfill is placed and compacted correctly. Typical

settlements are on the order of 1 to 2 percent of fill thickness. However, the need to

compact to the lowest portion of the backfill must be balanced against the need to

protect the pipe from damage from the compaction process. Some thickness of backfill

may need to be placed at compaction levels lower than specified (or smaller compaction

equipment used together with thinner lifts) to avoid damaging the pipe. Protecting the

pipe in this manner can result in somewhat greater surface settlements. Therefore,

although other alternatives may be available, the following options are presented for

consideration:

Controlled Low Strength Material: Because of these limitations, we suggest backfilling

the entire depth of the trench (both bedding and common backfill zones) with “controlled

low strength material” (CLSM), i.e., a lean, sand-cement slurry, “flowable fill,” or similar

material along all trench alignment reaches with low tolerances for surface settlements.

We suggest that CLSM used as pipe bedding and trench backfill exhibit a 28-day

unconfined compressive strength between 50 to 200 psi so that re-excavation is not

unusually difficult.

Placement of the CLSM in several lifts or other measures likely will be necessary to

avoid ‘floating’ the pipe. Measures also should be taken to maintain pipe alignment

during CLSM placement.

Compacted Soil Backfilling: Where compacted soil backfilling is employed, using the

site soils or similar materials as backfill, the risk of backfill settlements entailed in the

selection of this higher risk alternative must be anticipated and accepted by the

Client/Owner.



Revised


We anticipate that the on-site soils excavated from trenches will be suitable, in general,

for use as common trench backfill within the above-described limitations. Backfill soils

should be free of vegetation, organic debris and other deleterious materials. Fragments

of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) coarser than 3

inches in maximum dimension should not be incorporated into trench backfills.

If it is necessary to import material for use as backfill, the imported soils should be free

of vegetation, organic debris, and other deleterious materials. Imported material should

consist of relatively impervious soils that have less than 60 percent passing the No. 200

Sieve and should have a plasticity index of less than 20. Representative samples of the

materials proposed for import should be tested and approved prior to transport to the

site.

Soils placed for compaction as trench backfill should be conditioned to a relatively

uniform moisture content, placed and compacted in accordance with the Project

Earthwork section of this report.

Pipe Bedding: Pipe bedding materials, placement and compaction should meet the

specifications of the pipe manufacturer and applicable municipal standards. Bedding

should be brought up uniformly on both sides of the pipe to reduce differential loadings.

As discussed above, we suggest the use of CLSM or similar material in lieu of granular

bedding and compacted soil backfill where the tolerance for surface settlement is low.

(Placement of CLSM as bedding to at least 12 inches above the pipe can protect the

pipe and assist construction of a well-compacted conventional backfill although possibly

at an increased cost relative to the use of conventional bedding.)

If a granular bedding material is specified, it is our opinion that with regard to potential

migration of fines into the pipe bedding, design and installation follow ASTM D2321. If

the granular bedding does not meet filter criteria for the enclosing soils, then non-woven

filter fabric (e.g., Mirafi® 140N, or the equivalent) should be placed around the bedding to

reduce migration of fines into the bedding which can result in severe, local surface

settlements. Where this protection is not provided, settlements can develop/continue

several months or years after completion of the project. In addition, clay or concrete cut-

off walls should be installed to interrupt the granular bedding section to reduce the rates



Revised


and volumes of water transmitted along the sewer alignment which can contribute to

migration of fines.

If granular bedding is specified, the contractor should not anticipate that significant

volumes of on-site soils will be suitable for that use. Materials proposed for use as pipe

bedding should be tested by a geotechnical engineer for suitability prior to use.

Imported materials should be tested and approved by a geotechnical engineer prior to

transport to the site.

FROST HEAVE

Based on the results of the field exploration as well as the laboratory testing, it appears

that silty soils requiring special design considerations for the purpose of addressing frost

heave are present at the project. According to the US Army Corps of Engineers, the

soils on-site classify as F3 materials. Therefore, even if surface drainage is effective,

the likelihood of movement of pavements, flatwork and other hardscaping as a result of

frost heave, is relatively moderate to high.

PAVEMENT SECTIONS

A pavement section is a layered system designed to distribute concentrated traffic loads

to the subgrade. Performance of the pavement structure is directly related to the

physical properties of the subgrade soils and traffic loadings.

Standard practice in pavement design describes a typical flexible pavement section as a

“20-year” design pavement. However, most pavements will not remain in satisfactory

condition without routine maintenance and rehabilitation procedures performed

throughout the life of the pavement.

Pavement sections for the internal roadways were developed in general accordance with

the design guidelines and procedures of the American Association of State Highway and

Transportation Officials (AASHTO), the Colorado Department of Transportation (CDOT),

City of Thornton pavement construction practice. We understand that the proposed

roadways will be designated as Collector (Minor) roadways.



Revised


Subgrade Materials

Based on the results of our field and laboratory studies, subgrade materials encountered

in our test holes consisted predominantly of fill material that was comprised of sand and

clay/silt. These materials were classified typically as A-6 to A-7-6 soils in accordance

with the AASHTO classification system, with Group Index values from 2 to 25 in the

upper 4 feet.

GROUND collected composite bulk samples from the test holes. Based on the results of

the Proctor testing, GROUND utilized the “worst case” for use in the design of the

pavement. Resilient Modulus (MR) testing (AASHTO T-307) was performed on the

composite samples of the subgrade materials encountered along the alignments.

Typically, the R-value, unconfined compressive strength, California Bearing Ratio (CBR),

or other index properties of subgrade materials have been obtained and the resilient

modulus obtained only by correlation. However, due to the variability in the correlations,

subjecting representative samples of the subgrade to the actual resilient modulus test is

the most accurate way to determine soil support characteristics for use in pavement

design.

A dynamic load test, the resilient modulus measures the elastic rebound stiffness of

flexible pavement materials, base courses and subgrades under repeated loading. The

loading cycles were applied under various confining and deviatoric stresses as specified

in AASTHO T-294. The material was compacted to approximately 95 percent of

maximum dry density at approximately optimum moisture content, and at 2 percent and

4 percent above the optimum, based on AASHTO T-99 (the “standard Proctor”) for

cohesive soils.

The resilient modulus of a material at 2 percent above optimum moisture content

typically is used for the pavement design for fine-grained soils that classify as A-4, A-6,

or A-7. According to our testing results, resilient modulus values ranging from

approximately 5,178 to 5,817 psi were determined for the on-site materials. For the

purpose of this study, a resilient modulus value of 5,178 psi was utilized.

It is important to note that significant decreases in soil support as quantified by the

resilient modulus have been observed as the moisture content increases above the

optimum. Therefore, pavements that are not properly drained may experience a loss of

the soil support and subsequent reduction in pavement life.



Revised


Design Traffic

GROUND was provided existing and projected traffic information developed by Stolfus &

Associates, Inc., for Yosemite Street between 136th Avenue and Riverdale Road for the

“SD 27J High School #3” project, in a revised study dated March 18, 2016. We

understand that the proposed improvements will be constructed in 2017 (build year).

Based on this information, vehicle traffic values are indicated in the table below for

Yosemite Street, 136th Avenue, and Riverdale Road (south and east of Yosemite Street).

Additionally, as provided in the traffic study, a total of 2 to 4 percent trucks with a 60 / 40

percent split between single unit trucks and combination trucks was assumed based on

CDOT data for SH-22A. Using this information, the corresponding lane configuration

value of 0.60 for roadways consisting of 2 lanes (136th Avenue and Riverdale Road) and

3 lanes (Yosemite Street) and applicable design procedures, resulted in equivalent 18-

kip single axle loading (ESAL) value as provided in the table below.

Roadway Section ADT (Vehicles per

Day)

Truck Percentage

(%)

ESAL (20-year)

Yosemite Street 5,700 6 510,205

136th Avenue 8,800 4 1,011,703

Riverdale Road south of Yosemite

9,100 2 582,883

Riverdale Road east of Yosemite

5,300 2 339,482

If design traffic loadings differ significantly from these values, the pavement sections

provided below should be re-evaluated. The City of Thornton should be provided with

this report in order to review the above traffic values.

Pavement Design

The soil resilient modulus and the indicated ESAL value were used to determine the

required design structural number for the project pavements. The required structural

number was then used to develop pavement sections. Pavement designs for flexible



Revised


pavements were based on the DARWin™ computer program that solves the 1993

AASHTO pavement design equations. The resilient modulus and the design ESAL

values, as indicated above, along with a Reliability Level of 85 percent and a

serviceability index of 2.0 (City of Thornton – Standards and Specifications, Table 500-5)

were used in the pavement section designs for the proposed construction. The required

structural number was then used to develop pavement sections. Structural coefficients

of 0.44 and 0.14 were used for new hot bituminous asphalt (HBA) and aggregate base

course, respectively (City of Thornton, Table 500-6). The pavement design calculations

are presented in Appendix A.

Minimum Pavement Sections

Roadway

Minimum Full Depth Asphalt Section (inches Asphalt)

Minimum Composite

Section (inches Asphalt over

Aggregate Base Course)

Yosemite Street 7½ 5 / 8

136th Avenue 8½ 6 / 8

Riverdale Road south of Yosemite 7½ 5 / 8

Riverdale Road east of Yosemite 7 5 / 6

Pavement Properties

Hot Bituminous Asphalt (HBA): The asphalt pavement shall consist of a bituminous plant

mix composed of a mixture of high quality aggregate and bituminous material, which

meets the requirements of a job-mix formula established by a qualified engineer. The

asphalt materials used should be based on a SuperPave Gyratory Design Revolution

(NDES) of 75, for both the lower lift(s) and surface layer, per City of Thornton (Table 500-

10). Grading SG or S is acceptable for the lower lift(s) using PG 64-22 asphalt cement

binder and grading SX is acceptable for the surface layer using PG 64-28 asphalt

cement binder. Please note that the pavement binders could be adjusted depending on

the market condition at the time of construction. Alternate binding types should be

submitted to the City of Thornton for review and approval prior to construction.



Revised


Pavement lift thicknesses should be between 3 to 4 inches (SG) and 2¼ to 3½ inches

(S) for the lower lift(s), depending on the material type selected, and 2 to 3 inches for the

top lift (SX). Ultimately, NDES and asphalt cement binder requirements are those of City

of Thornton and may differ from those presented herein.

Aggregate Base Course (ABC): The aggregate base material should meet the criteria of

CDOT Class 6 aggregate base course. Base course should be placed in uniform lifts

not exceeding 8 inches in loose thickness and compacted to at least 95 percent of the

maximum dry density a uniform moisture contents within 3 percent of the optimum as

determined by ASTM D1557 / AASHTO T-180, the “modified Proctor.”

Pavement Subgrade Preparation

According to City of Thornton specifications, swelling (expansive) soils greater than 2

percent under a 150 psf surcharge (flexible pavements) shall not be permitted (for use)

without subgrade treatment. Based on our test results, a swell potential of 4.7 percent

was obtained from our testing within the proposed alignment of 136th Avenue (Test Hole

3 at a depth of approximately 4 feet). Therefore, subgrade treatment to mitigate the

swell potential in this area will be necessary based on the City of Thornton

specifications. A specific overexcavation/moisture-density treatment depth is not

specified by the City of Thornton. It is GROUND’s opinion that the roadway alignment

from approximately 200 feet in each direction from Test Hole 3 should be removed to a

depth of approximately 5 feet and replaced in a moisture-density treated manner.

Greater extents may be necessary based on the actual subsurface conditions

encountered/observed during construction. Based on our test results, swell potentials

less than 2 percent were obtained from our testing of samples obtained from the

remainder of 136th Avenue, Yosemite Street, and Riverdale Road. Therefore, mitigation

to address expansion potentials in all other areas does not appear to be necessary.

Even so, the upper 12 inches should be scarified and recompacted in accordance with

the Project Earthwork section of this report. The City of Thornton should be consulted

regarding the desired subgrade preparation measures.

Immediately prior to paving, the subgrade should be proof rolled with a heavily loaded,

pneumatic tired vehicle. Areas that show excessive deflection during proof rolling should

be excavated and replaced and/or stabilized. Areas allowed to pond prior to paving will



Revised


require significant re-working prior to proof-rolling. All subgrade preparation must

ultimately comply with roadway inspection, testing, and construction procedures outlined

by the governing municipality.

The proposed alignment(s) contains existing shallow-buried utilities. The contractor

should be aware that additional care should be taken when working in these areas. In

the event the subgrade materials are significantly disturbed or require moisture-density

treatment, recompaction over/adjacent to these utilities may be very difficult, possibly

resulting in the utilization of concrete or flow fill in order to properly prepare the subgrade

area for paving.

Pavement subgrade materials should be compacted in accordance with the Project

Earthwork section of this report. Subgrade preparation should extend the full width of

the pavement from back-of-curb to back-of-curb and also extend under the adjacent

sidewalks, exterior flatwork, etc.

Additional Observations

The collection and diversion of surface drainage away from paved areas is extremely

important to satisfactory performance of the pavements. The subsurface and surface

drainage systems should be carefully designed to ensure removal of the water from

paved areas and subgrade soils. Allowing surface waters to pond on pavements will

cause premature pavement deterioration. Where topography, site constraints or other

factors limit or preclude adequate surface drainage, pavements should be provided with

edge drains to reduce loss of subgrade support.

GROUND’s experience indicates that longitudinal cracking is common in asphalt-

pavements generally parallel to the interface between the asphalt and concrete

structures such as curbs, gutters or drain pans. Distress of this type is likely to occur

even where the subgrade has been prepared properly and the asphalt has been

compacted properly.

The standard care of practice in pavement design describes the flexible pavement

section as a “20-year” design pavement; however, most pavements will not remain in

satisfactory condition without routine, preventive maintenance and rehabilitation

procedures performed throughout the life of the pavement. Preventive pavement



Revised


treatments are surface rehabilitation and operations applied to improve or extend the

functional life of a pavement. These treatments preserve, rather than improve, the

structural capacity of the pavement structure. In the event the existing pavement is not

structurally sound, the preventive maintenance will have no long-lasting effect.

Therefore, a routine maintenance program to seal cracks, repair distressed areas, and

perform thin overlays throughout the life of the pavement is suggested.

A crack sealing and fog seal / chip seal program should be performed on flexible

pavements on a regular basis. After approximately 8 to 10 years, patching, additional

crack sealing, and asphalt overlay may be required. Prior to future overlays, it is

important that all transverse and longitudinal cracks be sealed with a flexible, rubberized

crack sealant in order to reduce the potential for propagation of the crack through the

overlay. Concrete pavements will likely require grinding and localized panel

replacement. Traffic volumes that exceed the values utilized by this report will likely

necessitate the need of pavement maintenance practices on a schedule of shorter

timeframe than that stated above. The greatest benefit of preventive maintenance is

achieved by placing the treatments on sound pavements that have little or no distress.

CLOSURE

Geotechnical Review: The author of this report should be retained to review project

plans and specifications to evaluate whether they comply with the intent of the

parameters in this report. The review should be requested in writing.

The geotechnical opinions presented in this report are contingent upon observation and

testing of project earthworks by representatives of GROUND. If another geotechnical

consultant is selected to provide materials testing, then that consultant must assume all

responsibility for the geotechnical aspects of the project by concurring in writing with the

conclusions in this report, or by providing alternative parameters.

Materials Testing: The Client should consider retaining a Geotechnical Engineer to

perform materials testing during construction. The performance of such testing or lack

thereof, in no way alleviates the burden of the contractor or subcontractor from

constructing in a manner that conforms to applicable project documents and industry

standards. The contractor or pertinent subcontractor is ultimately responsible for



Revised


managing the quality of their work; furthermore, testing by the geotechnical engineer

does not preclude the contractor from obtaining or providing whatever services they

deem necessary to complete the project in accordance with applicable documents.

Limitations: This report has been prepared for Brighton School District 27J as it

pertains to the construction of proposed roadways and improvements as described

herein. It may not contain sufficient information for other parties or other purposes. The

owner or any prospective buyer relying upon this report must be made aware of and

must agree to the terms, conditions, and liability limitations outlined in the proposal.

In addition, GROUND has assumed that project construction will commence by

Fall/Winter 2016. Any changes in project plans or schedule should be brought to the

attention of the Geotechnical Engineer, in order that the geotechnical parameters may

be re-evaluated and, as necessary, modified.

The geotechnical conclusions in this report relied upon subsurface exploration at a

limited number of exploration points, as shown in Figure 1, as well as the means and

methods described herein. Subsurface conditions were interpolated between and

extrapolated beyond these locations. It is not possible to guarantee the subsurface

conditions are as indicated in this report. Actual conditions exposed during construction

may differ from those encountered during site exploration.

If during construction, surface, soil, bedrock, or groundwater conditions appear to be at

variance with those described herein, the Geotechnical Engineer should be advised at

once, so that re-evaluation of the parameters may be made in a timely manner. In

addition, a contractor who relies upon this report for development of his scope of work or

cost estimates may find the geotechnical information in this report to be inadequate for

his purposes or find the geotechnical conditions described herein to be at variance with

his experience in the greater project area. The contractor is responsible for obtaining

the additional geotechnical information that is necessary to develop his workscope and

cost estimates with sufficient precision. This includes current depths to groundwater,

etc.

The materials present on-site are stable at their natural moisture content, but may

change volume or lose bearing capacity or stability with changes in moisture content.



Revised


Performance of the proposed pavement and improvements will depend on

implementation of the conclusions in this report and on proper maintenance after

construction is completed. Because water is a significant cause of volume change in

soils and rock, allowing moisture infiltration may result in movements, some of which will

exceed estimates provided herein and should therefore be expected by the owner.

The materials present on-site are stable at their natural moisture content, but may

change volume or lose bearing capacity or stability with changes in moisture content.

ALL DEVELOPMENT CONTAINS INHERENT RISKS. It is important that ALL aspects

of this report, as well as the estimated performance (and limitations with any such

estimations) of proposed project improvements are understood by the Client, Project

Owner (if different), or properly conveyed to any future owner(s). Utilizing these

parameters for planning, design, and/or construction constitutes understanding and

acceptance of conclusions or information provided herein, potential risks, associated

improvement performance, as well as the limitations inherent within such estimations. If

any information referred to herein is not well understood, it is imperative for the Client,

Owner (if different), or anyone using this report to contact the author or a company

principal immediately.

This report was prepared in accordance with generally accepted soil and foundation

engineering practice in the project area at the date of preparation. GROUND makes no

warranties, either expressed or implied, as to the professional data, opinions or

conclusions contained herein. Because of numerous considerations that are beyond

GROUND’s control, the economic or technical performance of the project cannot be

guaranteed in any respect.



Revised


GROUND appreciates the opportunity to complete this portion of the project and

welcomes the opportunity to provide the Owner with a cost proposal for construction

observation and materials testing prior to construction commencement.

Sincerely, GROUND Engineering Consultants, Inc.

Amy Crandall, P.E. Reviewed by Jason A. Smith, REM, P.E.

Sample of: Fill: Sandy CLAY

GRADATION TEST RESULTSJOB NO.: 16-3500

FIGURE: 24

58%

From: TH-2 at 3 feet Liquid Limit 42 Plasticity Index 24

Gravel 1% Sand 41% Silt and Clay

3" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #16 #40 #50 #100 #200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G

DIAMETER OF PARTICLE IN MILLIMETERS

SIEVE ANALYSIS: ASTM C 136 with C 117 or D 1140

Sieve Openings: U.S Standard Sieves

HYDROMETER ANALYSIS: ASTM D 422

Timed ReadingsCO

BBLE

GRAVELCoarse Fine

SANDCoarse Medium

SILT

CLAYFine

Sample of:


FIGURE: 25

67%



3" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #16 #40 #50 #100 #200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G





Timed ReadingsCO

BBLE

GRAVELCoarse Fine

SANDCoarse Medium

SILT

CLAYFine

Sample of: Sandy CLAY


FIGURE: 26

67%



3" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #16 #40 #50 #100 #200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G





Timed ReadingsCO

BBLE

GRAVELCoarse Fine

SANDCoarse Medium

SILT

CLAYFine

Sample of: Fill: Sandy CLAY


FIGURE: 27

58%



3" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #16 #40 #50 #100 #200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G





Timed ReadingsCO

BBLE

GRAVELCoarse Fine

SANDCoarse Medium

SILT

CLAYFine



FIGURE: 28

64%



3" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #16 #40 #50 #100 #200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G





Timed ReadingsCO

BBLE

GRAVELCoarse Fine

SANDCoarse Medium

SILT

CLAYFine

Sample of: CLAY with Sand


FIGURE: 29

76%



3" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #16 #40 #50 #100 #200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G





Timed ReadingsCO

BBLE

GRAVELCoarse Fine

SANDCoarse Medium

SILT

CLAYFine



FIGURE: 30

63%



3" 2" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #16 #40 #50 #100 #200

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.1110100

PE

RC

EN

T P

AS

SIN

G





Timed ReadingsCO

BBLE

GRAVELCoarse Fine

SANDCoarse Medium

SILT

CLAYFine

COMPACTION TEST REPORTCurve No.: 3063

Project No.: Date:

Project:Client:Location: 136th Ave, TH 1-13, 0-5'

Sample Number: 3063

Remarks:

MATERIAL DESCRIPTION

Description:

Classifications - USCS: AASHTO:

Nat. Moist. = Sp.G. =

Liquid Limit = Plasticity Index =

% < No.200 =

ROCK CORRECTED TEST RESULTS

FigureGround Engineering Consultants, Inc.

16-3500 1/15/16

Brighton School #275

Sand and Clay and Silt and Gravel

(SC)g A-4(0)

26 10

36.7 %

Maximum dry density = 120 pcf

Optimum moisture = 12 %

31

Dry

den

sity

, pcf

70

80

90

100

110

120

130

140

Water content, %

0 5 10 15 20 25 30 35 40

100% SATURATION CURVESFOR SPEC. GRAV. EQUAL TO:

2.82.72.6

Test specification: AASHTO T 99-01 Method A Standard AASHTO T 224-01 Oversize Correction Applied to Final Results


Project No.: Date:

Project:Client:Location: TH-14-23, Yosemite St

Sample Number: 3064

Remarks:


Description:




% < No.200 =



16-3500 1/15/16


Sand, Silt, Clay and Gravel

s(CL)g A-6(4)

41 21

60.3 %



32

Dry

den

sity

, pcf

70

80

90

100

110

120

130

140

Water content, %

0 5 10 15 20 25 30 35 40


2.82.72.6



Project No.: Date:

Project:Client:Location: TH-24-27

Sample Number: 3088

Remarks:


Description:




% < No.200 =



16-3500 1/21/16


Clays, Sand and Silt

s(CL) A-6(4)

32 13

51.3 %



33

Dry

den

sity

, pcf

70

80

90

100

110

120

130

140

Water content, %

0 5 10 15 20 25 30 35 40


2.82.72.6


TABLE 1SUMMARY OF LABORATORY TEST RESULTS

Sample Location Natural Natural Percent Atterberg Limits Percent USCS AASHTOTest Moisture Dry Passing Liquid Plasticity Swell Classifi- Classifi- Soil orHole Depth Content Density Gravel Sand Silt Clay No. 200 Limit Index (150 psf Surcharge cation cation Bedrock TypeNo. (feet) (%) (pcf) (%) (%) (%) (%) Sieve Pressure) (GI)

1 4 21.2 99.6 - - - - 76 35 15 0.1% CL A-6(10) CLAY with Sand

2 3 15.0 112.5 1 41 31 27 58 42 24 - CL A-7-6(11) Fill: Sandy CLAY

3 4 24.6 99.6 - - - - 85 51 24 4.7% CH A-7-6(23) CLAY with Sand

3 9 17.4 111.7 - - - - 89 49 25 - CL A-7-6(24) CLAYSTONE

4 3 19.5 107.7 - - - - 74 38 17 - CL A-6(12) CLAY with Sand

4 13 17.6 109.1 - - - - 92 47 20 - CL A-7-6(21) CLAYSTONE

5 3 23.7 96.4 2 31 22 45 67 55 25 1.7% MH A-7-5(17) Sandy SILT

6 4 17.9 92.5 - - - - 64 39 16 - CL A-6(9) Sandy CLAY

6 9 18.5 110.4 - - - - 91 36 17 0.8% CL A-6(15) CLAYSTONE

7 2 18.5 105.4 - - - - 71 43 20 0.5% CL A-7-6(13) CLAY with Sand

8 3 18.1 103.5 0 33 29 38 67 41 16 - CL A-7-6(10) Sandy CLAY

9 4 21.3 103.8 - - - - 81 43 19 - CL A-7-6(16) CLAY with Sand

9 9 11.0 121.6 - - - - 44 33 15 - SC A-6(3) Clayey SAND

10 4 16.3 107.5 - - - - 61 34 14 - CL A-6(6) Sandy CLAY

11 3 13.6 111.8 1 41 33 25 58 31 13 - CL A-6(5) Fill: Sandy CLAY

12 4 17.5 108.1 - - - - 65 38 19 - CL A-6(10) Fill: Sandy CLAY

12 9 16.6 113.0 - - - - 86 47 25 4.5% CL A-7-6(23) CLAYSTONE

13 4 20.8 103.1 - - - - 74 39 17 0.7% CL A-6(12) CLAY with Sand

14 3 15.6 110.9 1 35 34 30 64 39 18 - CL A-6(10) Sandy CLAY

15 4 17.2 107.3 - - - - 69 37 16 - CL A-6(10) Sandy CLAY

15 9 16.7 106.7 - - - - 67 35 15 - CL A-6(8) Sandy CLAY

16 3 17.1 109.4 - - - - 70 40 17 - CL A-6(11) Sandy CLAY

16 18 21.5 89.5 - - - - 74 53 29 - CH A-7-6(22) CLAYSTONE with Sand

Hydrometer Testing

TABLE 1SUMMARY OF LABORATORY TEST RESULTS

Sample Location Natural Natural Percent Atterberg Limits Percent USCS AASHTOTest Moisture Dry Passing Liquid Plasticity Swell Classifi- Classifi- Soil orHole Depth Content Density Gravel Sand Silt Clay No. 200 Limit Index (150 psf Surcharge cation cation Bedrock TypeNo. (feet) (%) (pcf) (%) (%) (%) (%) Sieve Pressure) (GI)

Hydrometer Testing

17 2 15.7 111.1 1 23 37 39 76 42 20 -0.5% CL A-7-6(15) CLAY with Sand


18 9 20.0 105.0 - - - - 76 46 23 - CL A-7-6(17) CLAY with Sand


20 3 17.0 103.3 - - - - 85 38 17 -0.1% CL A-6(14) CLAY with Sand


21 9 18.2 108.4 - - - - 84 47 25 -0.1% CL A-7-6(22) CLAYSTONE with Sand

22 3 23.3 89.7 - - - - 77 58 31 - CH A-7-6(25) CLAY with Sand

23 2 19.5 106.5 - - - - 84 43 21 0.5% CL A-7-6(18) CLAY with Sand

24 4 13.7 107.6 - - - - 55 33 15 - CL A-6(5) Sandy CLAY

24 9 20.6 100.6 1 35 39 24 63 30 13 - CL A-6(6) Sandy CLAY

25 3 18.2 102.5 - - - - 70 38 16 0.5% CL A-6(10) Sandy CLAY

26 2 12.1 112.8 - - - - 40 33 15 - SC A-6(2) Fill: Clayey SAND

26 7 22.2 101.7 - - - - 87 57 29 - CH A-7-6(29) CLAYSTONE


Resilient Modulus (psi)

1-13 1-5 12.2* 120.1* - - - - 37 26 10 5,817 SC A-4(0) Clayey SAND

14-23 1-5 9.3* 127.1* - - - - 60 41 21 5,178 CL A-7-6(10) SAND and CLAY

24-27 1-5 13.4* 116.8* - - - - 51 32 13 5,423 CL A-6(4) SAND and CLAY

* Indicates optimum moisture content and maximum standard Proctor density (ASTM D-698) Job No. 16-3500

TABLE 2SUMMARY OF SOIL CORROSION TEST RESULTS

Sample Location Water Redox Sulfides USCSTest Soluble pH Potential Content Resistivity Classifi- Soil orHole Depth Sulfates cation Bedrock TypeNo. (feet) (%) (mV) (ohm-cm)

2 3 <0.01 8.8 -105 Positive 4,693 CL Sandy CLAY

4 13 0.11 9.0 -111 Negative 1,211 CL CLAY

6 4 0.11 8.9 -106 Positive 778 CL Sandy CLAY

7 2 0.11 8.7 -102 Trace 1,341 CL CLAY with Sand

12 4 0.34 8.9 -108 Trace 1,132 CL Sandy CLAY



27 2 0.04 9.0 -112 Positive 1,906 CL Sandy CLAY

Job No. 16-3500

1993 AASHTO Pavement Design

DARWin Pavement Design and Analysis System

A Proprietary AASHTOWareComputer Software Product

Network Administrator

Flexible Structural Design Module

Brighton School District 27J - High School #3Yosemite Street

Flexible Structural Design

18-kip ESALs Over Initial Performance Period 510,205 Initial Serviceability 4.5 Terminal Serviceability 2 Reliability Level 85 %Overall Standard Deviation 0.44 Roadbed Soil Resilient Modulus 5,178 psiStage Construction 1

Calculated Design Structural Number 3.22 in

Specified Layer Design

Layer

Material Description

StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated

SN (in)1 Full Depth Asphalt 0.44 1 7.5 - 3.30

Total - - - 7.50 - 3.30






Brighton School District 27J - High School #3Yosemite Street

Composite Section





Layer


StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated

SN (in)1 Asphalt 0.44 1 5 - 2.202 Aggregate Base Course 0.14 1 8 - 1.12

Total - - - 13.00 - 3.32






Brighton School District 27J - High School #3136th Avenue


18-kip ESALs Over Initial Performance Period 1,011,703 Initial Serviceability 4.5 Terminal Serviceability 2 Reliability Level 85 %Overall Standard Deviation 0.44 Roadbed Soil Resilient Modulus 5,178 psiStage Construction 1



Layer


StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated


Total - - - 8.50 - 3.74






Brighton School District 27J - High School #3136th Avenue

Composite Section


18-kip ESALs Over Initial Performance Period 1,011,703 Initial Serviceability 4.5 Terminal Serviceability 2 Reliability Level 85 %Overall Standard Deviation 0.44 Roadbed Soil Resilient Modulus 5,178 psiStage Construction 1



Layer


StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated


Total - - - 14.00 - 3.76






Brighton School District 27J - High School #3Riverdale Road South of Yosemite





Layer


StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated


Total - - - 7.50 - 3.30






Brighton School District 27J - High School #3Riverdale Road South of Yosemite

Composite Section





Layer


StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated


Total - - - 13.00 - 3.32






Brighton School District 27J - High School #3Riverdale Road East of Yosemite Street





Layer


StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated

SN (in)1 Full Depth Asphalt 0.44 1 7 - 3.08

Total - - - 7.00 - 3.08






Brighton School District 27J - High School #3Riverdale Road East of Yosemite

Composite Section





Layer


StructCoef.(Ai)

DrainCoef.(Mi)

Thickness(Di)(in)

Width

(ft)

Calculated


Total - - - 11.00 - 3.04

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