Geotechnical_Report.pdf

Report Cover Page

Koeblen Road Expansion and Bridge Geotechnical Engineering Report

Rosenberg, Texas

September 8, 2026 | Terracon Project No. 92245249

Prepared for:

CivilCorp, LLC

29255 FM 1093 Road, Suite 7A

Fulshear, Texas 77441

11555 Clay Road, Suite 100

Houston, Texas 77043

P (713) 690-8989

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

September 8, 2026

CivilCorp, LLC

29255 FM 1093 Road, Suite 7A

Fulshear, Texas 77441

Attn: Mr. Jason Kaspar, P.E. – Transportation Division Manager

P: (979) 777-6169

E: jkaspar@civilcorp.us

Re: Geotechnical Engineering Report

Koeblen Road Expansion and Bridge

Koeblen Road and State Highway 36

Rosenberg, Texas

Terracon Project No. 92245249

Dear Mr. Kaspar:

We have completed the scope of geotechnical engineering services for the above referenced project in general accordance with Terracon Document No. 92235334.

Revision2, dated December 28, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning the design and construction of pavement and foundations for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon Consultants, Inc.

(Texas Firm Registration No.: F-3272)

Ammar Ali, Ph.D. Karla I. Stringer, P.E.

Senior Staff Engineer Group Manager

Geotechnical Engineering Report

Koeblen Road Expansion and Bridge | Rosenberg, Texas

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Introduction Project Description Site Conditions Geotechnical Characterization

Geology Subsurface Profile Groundwater Conditions Particle Size Analysis

Geotechnical Overview Bridge Foundations

Design Recommendations – Drilled Straight Shaft Foundations Construction Considerations – Drilled Shaft Foundations Design Recommendations – Driven Piles Construction Considerations – Driven Piles Foundation Construction Monitoring LPILE Parameters

Pavements Subgrade Preparation Wet Weather/Soft Subgrade Considerations Pavement Section Material Requirements Maintenance Considerations

Storm Sewer Uplift Pressures Lateral Earth Pressures Excavation Considerations Temporary Groundwater Control Utility Bedding Utility Backfill

General Comments

Figures GeoModel

Facilities | Environmental | Geotechnical | Materials ii

Attachments

Exploration and Testing Procedures Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Note: This report was originally delivered in a web-based format. Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/ http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed roadway extension and bridge to be located in Rosenberg, Texas. Our work was authorized by Mr. Thomas C. Kuykendall, Jr., Vice President with CivilCorp, LLC (CivilCorp) through signature of the Subconsultant

Agreement for Professional Services between CivilCorp and Terracon Consultants, Inc.

(Terracon) on June 13, 2025.

The purpose of our services was to provide information and geotechnical engineering recommendations relative to:

■ Foundation design parameters and construction

■ Lateral design (LPILE) parameters

■ D50 and D95 values to support scour analysis (to be performed by others)

■ Earthwork including site and subgrade preparation

■ Design guidelines for rigid pavements

■ Utility construction considerations including excavation and temporary groundwater control

The geotechnical engineering Scope of Services for this project included the advancement of 11 test borings (B-1 through B-11) to depths ranging from approximately 15 to 90 feet below existing grade, laboratory testing, engineering analysis, and preparation of this report.

At the time of this report, seven borings (B-1 through B-4 and B-7 through B-9) have been completed, two borings (B-5 and B-6) have not been performed due to restricted site access, and the remaining two borings (B-10 and B-11) have been removed from our scope of work by the client.

Maps showing the site and boring locations are shown on the Site Location and

Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs and as separate graphs in the Exploration and Laboratory Results section.

Project Description

Our initial understanding of the project was provided in our cost estimate document and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Proposed

Improvements 1

Koeblen Road

■ New four-lane boulevard with an approximate length of 2,500 feet. The pavement section is planned to consist of 7 inches of reinforced concrete over 8 inches of chemically treated subgrade according to

City of Rosenberg standards.

Bridge Structure

■ A 500-foot-long bridge across Seabourne Creek. The bridge is anticipated to be supported on a foundation system consisting of drilled straight shafts, with driven piles considered as an additional alternative.

Storm Sewer

■ An approximately 2,200-foot-long storm sewer line consisting of 48-inch-diameter reinforced concrete pipe (RCP) is planned to be installed along the new roadway at a maximum embedment depth of approximately 10 feet below existing grades using open-cut construction methods.

Finished Grade

Elevation Within approximately one to 5½ feet above existing grades

Maximum Loads

Anticipated structural loads were provided by CivilCorp on

July 30, 2026.

■ Westbound (WB) Abutment – 76 tons per shaft

■ WB Interior Bent – 102 tons per shaft

■ Eastbound (EB) Abutment – 66 tons per shaft

■ EB Interior Bent – 86 tons per shaft

Anticipated Traffic Major thoroughfare roadway

1. Based on information provided by CivilCorp on July 30, 2026, the originally proposed detention pond has been removed from the project’s scope of work.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration.

Facilities | Environmental | Geotechnical | Materials 3

Item Description

Project Location

The proposed Koeblen Road extension will run east–west, connecting State Highway (SH) 36 to the proposed new bridge across Seabourne Creek.

See Site Location

Existing

Improvements

The site was undeveloped, with a transmission line easement crossing the proposed roadway alignment in a northwest–southeast direction. Residential and commercial developments along with detention ponds were located adjacent to the roadway alignment. Seabourne Creek runs northwest southeast along the eastern boundary of the proposed roadway.

Current Ground Cover

Grass, weeds, and scattered trees. The site was heavily vegetated on the west end of the proposed roadway alignment, near SH 36.

Existing Topography

Relatively level. Seabourne Creek at the bridge crossing has sideslope declinations of about 3½ horizontal to 1 vertical (3½H:1V) and maximum depth of about 9 feet.

Geotechnical Characterization

Geology

Based on the geologic maps published by the Bureau of Economic Geology, the site for the proposed construction is located on the Beaumont Formation, a deltaic nonmarine

Pleistocene deposit. The Beaumont Formation is heterogeneous containing thick interbedded layers of clay, fine sand, and silt.

The clay fraction is primarily composed of montmorillonite, illite, kaolinite, and finely ground quartz. The clay present in the formation has been preconsolidated by a process of desiccation. Numerous wetting and drying cycles have produced a network of small randomly oriented, closely-spaced joints within some depth zones. These small joints frequently have a shiny appearance and the clays are called slickensided in these cases.

The joint pattern may have an influence on the construction and engineering behavior of the soil.

The coastal plain in this region has a complex tectonic geology, several major features of which are: Gulf Coastal geosyncline, salt domes, and major sea level fluctuations during the glacial stages, subsidence and geologic faulting activities. Most of these geologic faulting activities have ceased for millions of years, but some are still active. A detailed

Facilities | Environmental | Geotechnical | Materials 4 geologic fault investigation and study of the site geology are beyond the scope of this report.

Subsurface Profile

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting, and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration and Laboratory Results and the GeoModel can be found in the

Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model

Layer Layer Name General Description

1 Fill: Sandy Lean Clay gray

Lean Clay and Sandy

Lean Clay gray and reddish brown, medium stiff to very stiff, with calcareous nodules

3 Fat Clay light gray and reddish brown, medium stiff to hard, with calcareous nodules and sand seams

Silty Sand, Sandy Silt, and Sand tan, light gray, and reddish brown, loose to very dense, with clay pockets and seams, and scattered gravel

Groundwater Conditions

Borings B-1 through B-4 were advanced using dry drilling techniques to depths that ranged from approximately 18 to 30 feet in an effort to evaluate groundwater conditions at the time of our field program. Wet rotary techniques were used thereafter to the termination depth of the borings (about 90 feet). Borings B-7 through B-9 were advanced using dry drilling techniques to their termination depths (about 15 feet) in an effort to evaluate groundwater conditions at the time of our field program. Upon reaching groundwater, drilling was suspended for a period of about 15 minutes to allow the groundwater to rise and the groundwater levels to be recorded. Groundwater levels were also observed after about one day at borings B-1 through

B-4. The water levels observed in the boreholes can be found on the boring logs in

Exploration and Laboratory Results, and are summarized below.

Facilities | Environmental | Geotechnical | Materials 5

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project and should be evaluated prior to construction.

Particle Size Analysis

Particle size analyses were performed in accordance with ASTM D6913 on select soil samples from our borings. Gradation curves with D95 and D50 values are presented in

Exploration Results and are summarized in the following table.

Summary of Groundwater Level Observations 1

Boring

No.

Boring

Elevation 2

(feet)

Approximate

Boring

Depth 3

(feet)

Approximate

Depth of Dry

Drilling 3

(feet)

Approximate Depth of Groundwater 3 /

Elevation (feet)

Initial/During

Dry Drilling

After 5

Minutes

After 15

Minutes

After One

Day

B-1 89.74 90 18 164 / 74.74 ---5 ---5 20 / 69.74

B-2 84.29 90 20 144 / 70.29 ---5 ---5 21 / 63.29

B-3 86.21 90 18 154 / 71.21 ---5 ---5 21 / 65.21

B-4 93.83 90 30 224 / 71.83 ---5 ---5 19 / 74.83

B-7 92.44 15 15 ---6 ---6 ---6 ---5

B-8 92.63 15 15 ---6 ---6 ---6 ---5

B-9 91.05 15 15 ---6 ---6 ---6 ---5

1. Groundwater readings were obtained on October 27 through 31, 2025.

2. Boring elevation provided by CivilCorp.

3. Below existing grade at the time of our field program.

4. Cave-in.

5. Groundwater levels were not measured.

6. No free water observed.

Summary of Particle Size Analysis Results

Sample

ID

Sample

Elevation

(feet)

Soil Description D95

(mm)

D50

(mm)

Percent

Sand (%)

Percent

Fines (%)

B-1 77.24 – 75.74 Silty Sand (SM) 0.242 0.168 85.6 14.4

B-2 80.29 – 78.79 Silty Sand (SM) 0.238 0.142 75.7 24.3

B-3 80.21 – 78.71 Silty Sand (SM) 0.240 0.163 80.9 19.1

Facilities | Environmental | Geotechnical | Materials 6

Geotechnical Overview

The site appears suitable for the proposed construction based upon geotechnical conditions encountered in the test borings, provided that the recommendations in this report are implemented in the design and construction phases of this project. A summary of our findings and recommendations is provided below.

■ Fill soils were observed at the ground surface at borings B-4 and extended to a depth of approximately 4 feet below existing grade. Fill soils may be observed at varying depths at other locations within the site not explored during our field program.

■ Native subsurface soils generally consisted of medium stiff to hard lean clay and fat clay soils overlaying loose to very dense sands.

■ Groundwater levels were observed at borings B-1 through B-4 at depths of approximately 19 to 21 feet below existing grades (Elevation (El.) +74.83 to

+63.29 feet) one day after completion of drilling. Groundwater was not observed at borings B-7 through B-9 during or upon completion of drilling.

■ We understand the proposed bridge at this site is planned to be supported on a foundation system consisting of drilled straight shafts or, potentially, driven piles.

These types of foundation systems may be utilized to support the proposed bridge planned at this site provided the recommendations in this report are followed.

■ Deep foundations consisting of 24-inch diameter drilled straight shafts may be utilized to support the proposed bridge abutments at this site. As requested, allowable axial pile capacity curves for this pile size are included in Supporting

Information.

■ We understand the pavement structure will consist of 7 inches of concrete overlaying 8 inches of chemically treated subgrade in accordance with the City of

Rosenberg and Fort Bend County minimum requirements for permanent concrete roadways. This pavement section is expected to support up to approximately

450,000 Equivalent 18-kip Single Axle Loads (ESALs) over a 20-year design life of the pavement.

■ Based on the subsurface conditions observed at the site, we anticipate that the pavement subgrade will generally consist of medium to high plasticity clay soils.

The top 8 inches of the finished subgrade soils should be chemically treated with lime.

■ Excavations that extend into the clay soils may be performed in the dry without advance dewatering. Seepage that may occur in these clay soils is expected to be

Facilities | Environmental | Geotechnical | Materials 7 minor and likely can be handled utilizing a system of sumps and pumps at the bottom of the excavations. Excavations that extend through or into zones of silty/sand soils will likely require some form of advanced dewatering.

Groundwater levels will fluctuate with seasonal and climatic changes and should be evaluated just prior to construction. The contractor should determine effective methods of groundwater management prior to starting excavation operations.

■ Bedding and backfill for the storm sewer line should be in accordance with City of

Rosenberg or other appropriate standards.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration and Laboratory Results), engineering analyses, and our current understanding of the proposed project. This summary should be used in conjunction with the entire report for design purposes.

Details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The General

Comments section provides an understanding of the report limitations.

Bridge Foundations

The deep foundation systems should be designed to resist both horizontal and vertical forces.

Horizontal forces can be resisted by the passive pressure of soil acting on the vertical face of the foundation. Vertical downward forces can be resisted by the allowable end bearing pressure of the soils at the bottom of the foundation. Vertical uplift forces can be resisted by the dead weight of the foundation. Deep foundations will also provide resistance to vertical forces through the mobilization of the skin friction acting at the interface of the pile sidewall and the adjacent soils.

Design Recommendations – Drilled Straight Shaft Foundations

Based on the information provided by CivilCorp on July 30, 2026, 24-inch diameter drilled shafts are planned to support the proposed bridge abutments for this project. Allowable axial capacity curves for 24-inch diameter drilled straight shafts were developed following the

Allowable Stress Design (ASD) methodology and are presented in Supporting

Information. These capacity analyses were performed utilizing the commercial software program, SHAFT v2023. The FHWA method was used to compute the allowable axial load capacity of the shafts. The allowable capacity curves include a factor of safety of 2 for skin friction and a factor of safety of 3 for end bearing. These capacity curves were computed based on the soil profile and engineering properties of the subsurface soils observed within each boring at this site.

Facilities | Environmental | Geotechnical | Materials 8

The following table presents the recommendations for the drilled shaft foundation of the proposed bridge. As requested, a minimum recommended embedment shaft length is included based on the highest structural load provided by CivilCorp on July 30, 2026.

Drilled Shaft Design Summary

Reference

Boring

Shaft

Diameter

(in)

Load

Per

Shaft

(tons)

Boring

Elevation

(ft)1,2,3

Disregard

Elevation

(ft)2,4

Minimum

Tip

Elevation

(ft)2,5

Shaft

Length

(ft)2,5

B-1 24 102 90 80 45 45

B-2 24 102 84 74 42 42

B-3 24 102 86 76 46 40

B-4 24 102 94 84 54 40

1. Based on survey information provided by CivilCorp.

2. Values were rounded to the nearest half of a foot.

3. We assumed the approximately top of shaft elevation same as the top of the boring elevation.

4. A disregard depth is recommended from the top of the shaft to account for surface effects, the presence of fill and expansive soils, and anticipated disturbance during foundation installation. If the design scour depth is greater, the larger depth should be used as the disregard depth.

5. We recommend the drilled shafts at both abutments be constructed to the same tip elevation.

If proposed drilled shaft loads differ from those provided in this report, please provide those to us so that we may review and revise our analyses. Design drilled shaft penetration should be determined based on the final drilled shaft diameters, design foundation loads, and any lateral load resistance requirements.

Drilled straight shaft foundations should extend at least two feet or one-half the shaft diameter, whichever is greater, into the desired bearing strata in order to use the recommended allowable end bearing pressures. A minimum of four feet of the selected bearing stratum should also be beneath the foundation tip.

Long-term settlement of the drilled straight shaft foundation, designed and constructed in accordance with the recommendations presented in this report, should be about one inch or less.

Design of shafts should also include an evaluation of the structural capacity of the foundation element which may limit the allowable capacity.

Facilities | Environmental | Geotechnical | Materials 9

Construction Considerations – Drilled Shaft Foundations

The drilling contractor should be experienced in the subsurface conditions observed at the site, and the excavations should be performed with equipment capable of providing a relatively clean bearing area. The drilled straight shaft foundations should be installed in general accordance with the procedures presented in " Drilled Shafts: Construction

Procedures and LRFD Design Methods," by Brown, D.A., Turner, J.P., and Castelli, R.J., FHA Publication No. FHWA-NHI-10-016, 2010 and "Standard Specification for the

Construction of Drilled Piers", ACI Publication No. 336.1-01, 2001.

The successful completion of the drilled shafts will depend to a large extent on the suitability of the equipment and the operator’s skills. The operation sequence should be scheduled so that the shaft excavations can be completed, reinforcing steel placed, and the concrete poured in a continuous, rapid, and orderly manner to minimize the time the excavations are open. Concrete should be placed as soon as practical and in all instances should be placed within the same day.

Based on the subsurface conditions observed, the installation of drilled straight shafts will likely require the use of the Slurry Displacement Method and/or temporary steel casing due to the presence of sand soils. If drilled shaft installation is attempted without utilizing Slurry Displacement Method or temporary casing, zones of sloughing soils and/or groundwater inflow will likely occur during construction, particularly in the more sandy zones within the subgrade. Therefore, we recommend that provisions be incorporated into the plans and specifications to utilize slurry or casing to control sloughing and/or groundwater seepage during shaft construction.

The need for casing or slurry will depend on the depth of the drilled shaft and the groundwater conditions at the time of construction. If casing is used and seepage persists, the water accumulating in the foundation excavation should be pumped out.

The condition of the bearing surface should be evaluated immediately prior to placing concrete, if casing is used in lieu of slurry. If groundwater inflow is too severe to be controlled by the use of casing and pumping or significant sloughing of the sidewalls occurs, the slurry method of construction should be utilized to complete the foundation installation.

Where casing is used, removal of the casing should be performed with extreme care and under proper supervision to minimize mixing of the surrounding soil and water with the fresh concrete. Rapid withdrawal of the casing may develop a suction that could cause the soil and water to flow into the excavation. An insufficient head of concrete in the casing during withdrawal could also allow the water to intrude into the wet concrete.

Under no circumstances should loose soil be placed in the annulus between the casing and the drilled shaft sidewalls. The casing must be removed in order to utilize the skin friction values previously provided.

Facilities | Environmental | Geotechnical | Materials 10

During slurry displacement, the foundation excavation is filled with a slurry mixture. The level of slurry should be maintained above the groundwater level to maintain a positive head in the foundation excavation. Therefore, the slurry tends to seep out of the excavation, rather than the groundwater seeping into the open excavation. The slurry must be maintained in the foundation excavation until design termination depth is achieved and should be removed only as concreting proceeds. The properties of the slurry including the density, viscosity, and pH must be carefully controlled and should be in accordance with Item 416 of Texas Department of Transportation (TXDOT) Standard

Specifications for Construction of Highways, Streets, and Bridges.

Slurry left in place for long periods of time will build up on the sides of the shaft causing a reduction in skin friction.

The following procedures and equipment are recommended for installation of the drilled shafts by the Slurry Displacement Method:

■ The bottom of the shaft should be cleaned as well as practical just prior to concreting to remove cuttings.

■ The concrete should be placed by means of a tremie with a one-way valve to prevent slurry from entering the pipe. The tremie should extend to the bottom of the shaft to allow displacement of the slurry.

■ The end of the tremie should remain several feet within the concrete mass to reduce the entrapment of slurry.

■ The concrete should be relatively fluid to reduce the entrapment of slurry. We recommend that concrete with a slump of 6 to 8 inches be used.

■ The upper few feet of concrete should be expunged from the shaft excavation if found to be contaminated with slurry or soil.

A surface casing may be required in addition to the slurry for shaft installation at this site if sloughing of the surficial soils occurs. Where casing is used, removal of the casing should be performed with extreme care as previously discussed in this section.

Production shaft installation should be observed by a qualified technician experienced in drilled shaft installation techniques. At a minimum, the technician should observe shaft excavation, note any unusual installation occurrences, observe slurry propert ies and/or casing installation and removal, observe concrete placement and generally evaluate if shaft installation is being performed in accordance with the project specifications.

Design Recommendations – Driven Piles

Alternatively, deep foundation systems consisting of driven steel pipe piles may be utilized to support the proposed bridge planned at this site.

Facilities | Environmental | Geotechnical | Materials 11

Allowable skin friction and end bearing values for steel pipe piles are presented in the following tables. These design parameters were estimated based on the soil profile and engineering properties of the subsurface soils observed within each boring at this site. The end bearing and skin friction values within the upper 10 feet of the on-site soils were neglected to account for surface effects, the presence of fill and expansive soils, and anticipated disturbance during foundation installation. The following allowable capacities include a factor of safety of 2 for skin friction and a factor of safety of 3 for end bearing. The allowable skin friction values provided in the following tables may be used to calculate the uplift resistance for the pile.

Design Parameters for Driven Piles B-1

Depth1

(feet)

Elevation2

(feet) Soil Description

Allowable Side

Friction3 (psf)

Net Allowable

End Bearing

Pressure4 (psf)

0 to 10 +89.7 to +79.7 Lean Clay Disregard

10 to 12 +79.7 to +77.7 Lean Clay 250

Disregard 12 to 15 +77.7 to +74.7 Silty Sand 250

15 to 23 +74.7 to +66.7 Silty Sand 350

23 to 38 +66.7 to +51.7 Silty Sand 550 11,000

38 to 43 +51.7 to +46.7 Fat Clay 250 1,500

43 to 50 +46.7 to +39.7 Sand with Silt 750 11,000

50 to 65 +39.7 to +24.7 Sand with Silt 650 12,000

65 to 78 +24.7 to +11.7 Sand with Silt 600 10,000

78 to 90 +11.7 to -0.3 Fat Clay 650 7,800

1. Grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. The allowable side friction is based on a rectangular pressure distribution.

4. The net allowable end bearing pressure refers to the pressure at the foundation bearing level in excess of the surrounding overburden pressure. A minimum penetration of 2 feet or one-half a shaft diameter, whichever is greater, into the desired bearing strata should be achieved with a minimum of

4 feet of the selected bearing stratum beneath the shaft tip to use the recommended allowable end bearing pressure.

Facilities | Environmental | Geotechnical | Materials 12

Design Parameters for Driven Piles B-2

Depth1

(feet)

Elevation2

(feet) Soil Description

Allowable Side

Friction3 (psf)

Net Allowable

End Bearing

Pressure4 (psf)

0 to 4 +84.3 to +80.3 Lean Clay Disregard

4 to 10 +80.3 to +74.3 Silty Sand Disregard

10 to 14 +74.3 to +70.3 Silty Sand 200 Disregard

14 to 23 +70.3 to +61.3 Silty Sand 300

23 to 33 +61.3 to +51.3 Silty Sand 450 10,000

33 to 53 +51.3 to +31.3 Sand with Silt 600 10,000

53 to 70 +31.3 to +14.3 Sand with Silt 900 10,000

70 to 78 +14.3 to +6.3 Sand with Silt 900 13,000

78 to 90 +6.3 to -5.7 Lean Clay 350 4,500

1. Grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. The allowable side friction is based on a rectangular pressure distribution.

4. The net allowable end bearing pressure refers to the pressure at the foundation bearing level in excess of the surrounding overburden pressure. A minimum penetration of 2 feet or one-half a shaft diameter, whichever is greater, into the desired bearing strata should be achieved with a minimum of 4 feet of the selected bearing stratum beneath the shaft tip to use the recommended allowable end bearing pressure.

Facilities | Environmental | Geotechnical | Materials 13

Design Parameters for Driven Piles B-3

Depth1

(feet)

Elevation2

(feet) Soil Description

Allowable Side

Friction3 (psf)

Net Allowable

End Bearing

Pressure4 (psf)

0 to 6 +86.2 to +80.2 Sandy Lean Clay Disregard

6 to 10 +80.2 to +76.2 Silty Sand

10 to 15 +76.2 to +71.2 Silty Sand 200 Disregard

15 to 23 +71.2 to +63.2 Silty Sand 350

23 to 28 +63.2 to +58.2 Silty Sand 400 11,000

28 to 40 +58.2 to +46.2 Silty Sand 550 13,000

40 to 53 +46.2 to +33.2 Silty Sand 1,000 10,000

53 to 68 +33.2 to +18.2 Sand with Silt 850 12,000

68 to 78 +18.2 to +8.2 Sand with Silt 1,100 13,000

78 to 90 +8.2 to -3.8 Lean Clay 650 8,000

1. Grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. The allowable side friction is based on a rectangular pressure distribution.

4. The net allowable end bearing pressure refers to the pressure at the foundation bearing level in excess of the surrounding overburden pressure. A minimum penetration of 2 feet or one-half a shaft diameter, whichever is greater, into the desired bearing strata should be achieved with a minimum of

4 feet of the selected bearing stratum beneath the shaft tip to use the recommended allowable end bearing pressure.

Facilities | Environmental | Geotechnical | Materials 14

Design Parameters for Driven Piles B-4

Depth1

(feet)

Elevation2

(feet) Soil Description

Allowable Side

Friction3 (psf)

Net Allowable

End Bearing

Pressure4 (psf)

0 to 4 +93.8 to +89.8 Sandy Lean Clay Disregard

4 to 10 +89.8 to +83.8 Fat Clay

10 to 14 +83.8 to +79.8 Fat Clay 400 Disregard

14 to 23 +79.8 to +70.8 Fat Clay 450

23 to 38 +70.8 to +55.8 Silty Sand 500 10,000

38 to 53 +55.8 to +40.8 Silty Sand 1,400 12,000

53 to 75 +40.8 to +18.8 Silty Sand 1,400 15,000

75 to 83 +18.8 to +10.8 Silty Sand 1,300 13,000

83 to 90 +10.8 to +3.8 Fat Clay 600 7,500

1. Grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. The allowable side friction is based on a rectangular pressure distribution.

4. The net allowable end bearing pressure refers to the pressure at the foundation bearing level in excess of the surrounding overburden pressure. A minimum penetration of 2 feet or one-half a shaft diameter, whichever is greater, into the desired bearing strata should be achieved with a minimum of

4 feet of the selected bearing stratum beneath the shaft tip to use the recommended allowable end bearing pressure.

Design of piles should also include an evaluation of the structural capacity of the foundation element which may limit the allowable capacity. Any pile splices must provide positive load transfer both in compression and tension since driving displacement piles within clay could result in heave. As the pile is driven, it displaces soil upward toward the surface. This upward soil movement can "drag" the adjacent piles up and lift them off of their bearing layer causing tension along the piles.

Pile groups subjected to axial loads can be affected by numerous factors which may include foundation type, size and length, spacing, overall group size, loading conditions, installation procedures and soil type and strength. With a center-to-center spacing of at least three widths or diameters, the group effect will be insignificant on the capacity of the piles. Therefore, the group capacity for axial load may be taken as the sum of the individual pile capacities in the group.

Settlement of a single, isolated pile will depend on the elastic properties of the foundation, the applied load, and the interaction of the soil and foundation. Settlement

Facilities | Environmental | Geotechnical | Materials 15 of a single, isolated pile is anticipated to be primarily elastic and will occur relatively soon as load is applied. Significant consolidation settlement of a single, isolated pile due to applied load is not anticipated for the allowable capacities. Our experience indicates that a single, isolated foundation loaded to about one-half of its ultimate capacity will result in settlements of about 1/2 inch or less. Groups generally undergo more settlement than single, isolated foundation elements for the same applied load.

Consolidation settlement due to the applied load will depend on the pile cap size and number of piles beneath the cap. To evaluate the settlement response of the pile groups, we recommend that details of the planned pile groups (such as length, size, and arrangement) be provided to us. Once we receive the pile group details, we can perform a detailed settlement analysis and provide our comments in a supplemental letter report.

Construction Considerations – Driven Piles

The installation of driven piles at this site should preferably be accomplished by driving alone. However, predrilling or controlled jetting may be required to achieve the design penetrations if excessive resistance to penetration occurs during driving. The effects and methods of pile installation should be given proper consideration when choosing and designing pile foundation systems. In most situations, the greatest stress a pile will experience is during installation. Pile and soil properties, embedment length requirements and driving equipment are only a few of the many variables to consider in determining the most efficient method of pile installation.

Driving piles to design embedment depths may be facilitated by predrilling to a depth somewhat less than the anticipated final embedment depth. Under no circumstances should predrilling extend deeper than 5 feet above the final pile embedment depth unless refusal occurs. The predrilled excavation should be about 4 inches less in width than the pile size to promote the development of skin friction resistance. Care should be exercised during predrilling since it can affect the lateral and axial capacities of the pile.

Production piles should be driven to a predetermined depth with blow count as a secondary consideration. Because set-up during interruptions can produce increased resistance to driving, a pile should be driven to its design depth without any delays, if possible.

Also, if a pile exhibits a resistance lower than the terminal resistance values given by driving formulas at an appreciable depth below the predetermined depth, the pile may be re-tapped after a suitable elapsed time and after the installation of other nearby piles. The re-tap should be performed at the contractor’s discretion to prove the acceptability of the pile. Should, in the Geotechnical Engineer’s judgment, the re-tap not indicate adequate capacity, a new pile should be installed to provide sufficient capacity.

In addition, we recommend the use of a “Pile Driving Analyzer” (PDA) during pile installation. The PDA can monitor driving stresses and hammer energy during pile

Facilities | Environmental | Geotechnical | Materials 16 installation, and also provides a continuous record of the pile installation. Such information can be beneficial in evaluation of the acceptability of a driven pile. Varying installation methods and soil conditions can have an effect on the soil-pile interaction and capacity.

We recommend that full scale pile load tests be performed to evaluate the actual pile capacities at this specific site. We recommend performing at least two load tests per pile size/type. Terracon should be involved in evaluating and selecting the appropriate depths for the test piles. The test piles should be tested to failure as defined by pile load test procedures. To help accommodate testing the pile to failure, the loading apparatus should be designed to reach a load of at least three times the estimated design load.

Installation of test piles should be identical to planned production installation procedures.

The performance of the piles will be highly dependent upon the quality of construction.

Thus, we recommend that pile installation be closely observed by a qualified inspector experienced in pile installation techniques. At a minimum, the inspector should record blows, note any unusual installation occurrences, observe the hammer operation and generally evaluate if pile installation is being performed in accordance with the specifications.

Foundation Construction Monitoring

As previously mentioned, regardless of the deep foundation system selected, the performance of the foundation systems for the proposed bridge will be highly dependent upon the quality of construction. Thus, we recommend that foundation installation be observed full time by an experienced Terracon soil technician under the direction of our

Geotechnical Engineer. We would be pleased to develop a plan for foundation installation observation to be incorporated in the overall quality control program.

LPILE Parameters

As requested, LPILE design parameters are presented in the following tables. These design parameters were computed based on soil profiles and engineering properties of the subsurface soils observed within each boring at this site.

For abutment drilled shafts, the resistance should be disregarded through embankment fills, to a depth of 10 feet from the top of the shaft, or to the design scour depth, whichever is greater.

These parameters are based on an evaluation of a single pile. Appropriate reduction factors should be used when performing a lateral load analysis of piles in a group. These reduction factors are based on the direction of the applied lateral load as it relates to the pile group, Facilities | Environmental | Geotechnical | Materials 17 spacing of the piles, and configuration of the piles within the group. If desired, Terracon can review a proposed foundation layout and assist with providing group reduction factors.

LPILE Design Parameters B-1

Depth1

(feet)

Elevation2

(feet) Soil Type

Effective

Unit

Weight3

(pcf)

Lateral

Subgrade

Modulus

(pci)

Ultimate

Soil

Strain 50

(in/in)

Undrained

Shear

Strength

(psf)

Angle of

Internal

Friction

(degree)

0 to 4 +89.7 to

+85.7 Soft Clay 125 --- 0.020 500 ---

4 to 10 +85.7 to

+79.7

Stiff Clay w/o Free

Water

125 --- 0.005 3,000 ---

10 to 12 +79.7 to

+77.7 Soft Clay 125 --- 0.020 500 ---

12 to 15 +77.7 to

+74.7

Sand

(Reese) 120 90 --- --- 31

15 to 23 +74.7 to

+66.7

Sand

(Reese) 58 60 --- --- 31

23 to 38 +66.7 to

+51.7

Sand

(Reese) 58 125 --- --- 36

38 to 43 +51.7 to

+46.7 Soft Clay 58 --- 0.020 500 ---

43 to 50 +46.7 to

+39.7

Sand

(Reese) 58 125 --- --- 33

50 to 65 +39.7 to

+24.7

Sand

(Reese) 58 60 --- --- 31

65 to 78 +24.7 to

+11.7

Sand

(Reese) 58 60 --- --- 30

78 to 90 +11.7 to

-0.3

Stiff Clay w/o Free

Water

58 --- 0.005 2,600 ---

1. Approximate depth below existing grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. Groundwater was assumed at an approximate elevation of 74.7 feet (15 feet below ground surface (bgs)) for use in calculating effective unit weight.

Facilities | Environmental | Geotechnical | Materials 18

LPILE Design Parameters B-2

Depth1

(feet)

Elevation2

Weight3

(pcf)

Lateral

Subgrade

Modulus

(pci)

Ultimate

Soil

Strain 50

(in/in)

Undrained

Shear

Strength

(psf)

Angle of

Internal

Friction

(degree)

0 to 4 +84.3 to

+80.3 Soft Clay 125 --- 0.020 500 ---

4 to 14 +80.3 to

+70.3

Sand

(Reese) 120 90 --- --- 29

14 to 23 +70.3 to

+61.3

Sand

(Reese) 120 60 --- --- 29

23 to 33 +61.3 to

+51.3

Sand

(Reese) 58 60 --- --- 33

33 to 53 +51.3 to

+31.3

Sand

(Reese) 58 125 --- --- 34

53 to 70 +31.3 to

+14.3

Sand

(Reese) 58 125 --- --- 35

70 to 78 +14.3 to

+6.3

Sand

(Reese) 58 60 --- --- 34

78 to 90 +6.3 to

-5.7

Stiff Clay w/o Free

Water

63 --- 0.007 1,500 ---

1. Approximate depth below existing grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. Groundwater was assumed at an approximate elevation of 70.3 feet (14 feet bgs) for use in calculating effective unit weight.

Facilities | Environmental | Geotechnical | Materials 19

LPILE Design Parameters B-3

Depth

(feet)

Elevation1

Weight2

(pcf)

Lateral

Subgrade

Modulus

(pci)

Ultimate

Soil

Strain 50

(in/in)

Undrained

Shear

Strength

(psf)

Angle of

Internal

Friction

(degree)

0 to 6 +86.2 to

+80.2 Soft Clay 125 --- 0.020 500 ---

6 to 15 +80.2 to

+71.2

Sand

(Reese) 120 90 --- --- 29

15 to 28 +71.2 to

+58.2

Sand

(Reese) 58 60 --- --- 31

28 to 40 +58.2 to

+46.2

Sand

(Reese) 58 125 --- --- 34

40 to 53 +46.2 to

+33.2

Sand

(Reese) 58 60 --- --- 33

53 to 68 +33.2 to

+18.2

Sand

(Reese) 58 125 --- --- 35

68 to 78 +18.2 to

+8.2

Sand

(Reese) 58 125 --- --- 37

78 to 90 +8.2 to

-3.8

Stiff Clay w/o Free

Water

63 --- 0.005 2,700 ---

1. Approximate depth below existing grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. Groundwater was assumed at an approximate elevation of 71.2 feet (15 feet bgs) for use in

Facilities | Environmental | Geotechnical | Materials 20

LPILE Design Parameters B-4

Depth1

(feet)

Elevation2

Weight3

(pcf)

Lateral

Subgrade

Modulus

(pci)

Ultimate

Soil

Strain 50

(in/in)

Undrained

Shear

Strength

(psf)

Angle of

Internal

Friction

(degree)

0 to 4 +93.8 to

+89.8 Soft Clay 125 --- 0.020 500 ---

4 to 14 +89.8 to

+79.8

Stiff Clay w/o Free

Water

120 --- 0.007 1,600 ---

14 to 19 +79.8 to

+74.8

Stiff Clay w/o Free

Water

120 --- 0.007 1,800 ---

19 to 23 +74.8 to

+70.8

Stiff Clay w/o Free

Water

58 --- 0.007 1,800 ---

23 to 38 +70.8 to

+55.8

Sand

(Reese) 58 60 --- --- 33

38 to 53 +55.8 to

+40.8

Sand

(Reese) 58 125 --- --- 36

53 to 75 +40.8 to

+18.8

Sand

(Reese) 58 125 --- --- 34

75 to 83 +18.8 to

+10.8

Sand

(Reese) 58 60 --- --- 33

83 to 90 +10.8 to

-3.8

Stiff Clay w/o Free

Water

58 --- 0.007 2,500 ---

1. Approximate depth below existing grade at the time of our field program.

2. Based on survey data provided by CivilCorp.

3. Groundwater was assumed at an approximate elevation of 74.8 feet (19 feet bgs) for use in

Facilities | Environmental | Geotechnical | Materials 21

Pavements

Subgrade Preparation

Pavement construction areas should be stripped of all vegetation, topsoil, trees, and other debris/unsuitable surface materials. Roots of trees to be removed within the construction areas should be grubbed to full depths. Care should be taken to replace or recompact all soil removed or loosened by the removal of tree roots and stumps as recommended in subsequent paragraphs. Any open excavations remaining after site stripping should be backfilled with on-site clay soils. The on-site clay soils used to backfill the excavations should be compacted to a minimum of 95 percent of the maximum dry density as determined by the Standard Effort (ASTM D 698) in lifts not exceeding 8 inches loose measure.

Once final subgrade elevations have been achieved, the exposed soil subgrade area should be proofrolled with a 20-ton pneumatic roller or equivalent equipment, such as a fully loaded dump truck, to detect weak zones in the subgrade. Weak areas detected during proofrolling, as well as zones containing organic matter and/or debris, should be removed to expose firm subgrade and replaced with soils exhibiting similar classification, moisture content, and density as the adjacent in-situ soils. Proper site drainage should be maintained during construction so that ponding of surface runoff does not occur and cause construction delays and/or inhibit site access.

Subsequent to proofrolling, and just prior to placement of fill, the exposed subgrade within the construction areas should be evaluated for moisture and density. The subgrade should be moisture conditioned between optimum moisture content and 4 percent wet of optimum moisture content and have an in-place dry density of at least 95 percent of the Standard Effort (ASTM D 698) maximum dry density. If the moisture or density does not meet the above criteria, the subgrade should be scarified to a minimum depth of 6 inches, moisture conditioned to between optimum and 4 percent wet of optimum moisture content and compacted to at least 95 percent of the Standard Effort

(ASTM D 698) maximum dry density.

Any fill soils used for grade adjustments in the proposed pavement areas should consist of clean on-site soils that are free of organics/debris or imported soils with similar characteristics as the on-site soils and should be compacted to a minimum of 95 percent of the maximum dry density as determined by the Standard Effort (ASTM D 698) at a moisture content within 4 percent wet of the optimum moisture content in lifts not exceeding 8 inches loose measure.

Prior to any filling operations, samples of the proposed borrow materials should be obtained for laboratory moisture-density testing. The tests will provide a basis for evaluation of fill compaction by in-place density testing. A qualified soil technician should

Facilities | Environmental | Geotechnical | Materials 22 perform sufficient in-place density tests during the filling operations to evaluate that proper levels of compaction are being attained.

Wet Weather/Soft Subgrade Considerations

Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by methods of subgrade improvement.

Methods of subgrade improvement, as described below, could include scarification, moisture conditioning and recompaction, removal of unstable materials and replacement with select fill, and chemical treatment. The appropriate method of improvement, if required, would be dependent on factors such as schedule, weather, the size of area to be stabilized, and the nature of the instability. More detailed recommendations can be provided during construction as the need for subgrade stabilization occurs. Performing site grading operations during warm seasons and dry periods would help reduce the amount of subgrade stabilization required.

If the exposed subgrade is unstable during proofrolling operations, it could be stabilized using one of the methods outlined below.

■ Scarification and Recompaction - It may be feasible to scarify, dry, and recompact the exposed soils. The success of this procedure would depend primarily upon favorable weather and sufficient time to dry the soils. Stable subgrades likely would not be achievable if the thickness of the unstable soil is greater than about 1 foot, if the unstable soil is at or near groundwater levels, or if construction is performed during a period of wet or cool weather when drying is difficult.

■ Select fill - Removal and replacement with select fill is a common procedure to improve subgrade stability. The undercut depth below finished subgrade elevation will depend on the site conditions at the time of construction. The select fill soils should consist of lean clay (CL), sandy lean clay (CL), and/or clayey sand (SC) soils with plasticity index between 10 and 20. The select fill soils should be moisture conditioned to within 2 percent of the optimum moisture content and have an in-place dry density of at least 95 percent of the Standard Effort (ASTM D

698) maximum dry density.

■ Chemical Treatment - Improvement of subgrades with lime could be considered for improving unstable soils. Chemical treatment should be performed by a pre-qualified contractor having experience with successfully stabilizing subgrades in the project area on similar sized projects with similar soil conditions. Terracon

Facilities | Environmental | Geotechnical | Materials 23 should be contacted for additional recommendations if chemical treatment is needed due to soft and wet subgrade.

The subgrade should be conditioned by one of these means such that it can be proofrolled without undue deflection or rutting. Further evaluation of the need and recommendations for subgrade stabilization can be provided during construction as the geotechnical conditions are exposed.

Pavement Section

Once the subgrade is properly prepared, a rigid pavement system may be considered for this project. Detailed traffic loads and frequencies were not available at the time of this report. However, we understand the roadway will be classified as a Major Thoroughfare.

We understand the proposed roadway will consist of 7 inches of concrete overlaying 8 inches of chemically stabilized subgrade in accordance with City of Rosenberg and/or

Fort Bend County design standards.

Based on the subsurface conditions observed at this site, we anticipate that the pavement subgrade will generally consist of medium to high plasticity clay soils.

Therefore, the top 8 inches of the finished subgrade soils directly beneath the pavements should be chemically treated with lime. Chemical treatment will increase the supporting value of the subgrade and decrease the effect of moisture on subgrade soils.

These 8 inches of treatment is a required part of the pavement design and is not a part of site and subgrade preparation for wet/soft subgrade conditions. Chemical treatment should occur after all utility trenches have been excavated and backfilled.

Using the 1993 AASHTO Guide for Design of Pavement Structures, we estimated the equivalent 18-kip ESALs that the anticipated pavement sections can support.