Water Line Rehabilitation - Deussen Park Harris County Precinct 1

UPIN 25101MF3PZ01

Report File

1. Geotechnical Reports

i. Connectivity Project - Deussen - Eisenhower (UPIN 22101MF2F801), by HVJ Associates, Inc., June 3, 2022; Report No. HG2110554

ii. Metal Pavilions Alexander Deussen Park, by HBC/Terracon, Inc., December 2004;

Report No. 92045-421

iii. Sonnier Road Extension Alexander Deussen Park, by Geotech Engineering and Testing Services, Inc., March 2000; Report No. 00-075E

GEOTECHNICAL REPORT

DUESSEN PARK IMPROVEMENTS

Harris County, Texas

SUBMITTED TO

Cobb, Fendley & Associates, Inc. (CobbFendley)

22316 Grand Corner Drive, Suite 100

Houston, TX 77042

BY

HVJ ASSOCIATES, INC.

HOUSTON, TEXAS

June 03, 2022

REPORT NO. HG2110554

i

June 03, 2022

Mr. Daniel Scott Project Manager | Principal Cobb, Fendley & Associates, Inc. (CobbFendley) 22316 Grand Corner Drive, Suite 100 Houston, TX 77042

Re: Geotechnical Investigation Deussen Park Improvements Harris County, Texas Owner: Harris County Precinct 1 HVJ Report No.: HG2110554

Dear Mr. Scott:

Submitted herein is the draft report of our geotechnical investigation for the above referenced project. The study was conducted in general accordance with our proposal number HG2110554 dated December 9, 2021 and is subject to the limitations presented in this report.

We appreciate the opportunity of working with you on this project. Please read the entire report and notify us if there are questions concerning this report or if we may be of further assistance.

Sincerely, HVJ ASSOCIATES, INC.

Texas Firm Registration No. F-00064

DRAFT DRAFT

Sharmi Vedantam, P.E. Prakash Dahal, EIT Houston Branch Manager Staff Engineer

MH/SV/PD

Copies submitted: 1 (electronic)

This document was released for the purpose of interim review under the authority of Sharmi P. Vedantam, PE 100218 on June 03, 2022. It is not to be used for construction, bidding or permit purposes.

TABLE OF CONTENTS

Page

1 EXECUTIVE SUMMARY ....................................................................................................................... i

2 INTRODUCTION

2.1 Project Description

2.2 Purpose and Scope of Work

3 FIELD EXPLORATION

3.1 Geotechnical Borings

3.2 Survey Data

3.3 Sampling Methods

3.4 Water Level Measurements

4 LABORATORY TESTING

4.1 Dispersive Tests for Cohesive Soils

4.2 Sieve and Hydrometer Test Results

4.3 Consolidated Undrained Triaxial Tests

5 SITE CHARACTERIZATION

5.1 General Geology

5.2 Geologic Faulting

5.3 Soil Stratigraphy

5.4 Groundwater Conditions

6 BULKHEAD DESIGN AND CONSTRUCTION RECOMMENDATIONS

6.1 General

6.2 Lateral Earth Pressures

6.3 Soil Parameters for Lateral Load Analysis

6.4 Global Stability Analysis

6.5 Dispersive Soils

6.6 Recommendations for Fill

7 FOUNDATION RECOMMENDATIONS FOR PEDESTRIAN BRIDGE, ELEVATED

BOARDWALK AND L-SHAPED PIER

7.1 General

7.2 Foundation Selection

7.3 Analyses Criteria

7.4 Safety Factor

7.5 Timber Pile Construction Recommendations

8 TRAIL, PARKING LOT AND ACCESS ROAD PAVEMENT RECOMMENDATIONS

8.1 General

8.2 Pavement Sections

8.3 Preparation of Subgrade

9 LIMITATIONS

APPENDICES

SITE VICINITY MAP .................................................................................................................................... A

PLAN OF BORINGS ..................................................................................................................................... B

GEOLOGY MAP ............................................................................................................................................ C

FAULT MAP .................................................................................................................................................... D

BORING LOGS AND KEY TO TERMS & SYMBOLS ........................................................................ E

SUMMARY OF LABORATORY TEST RESULTS ..................................................................................F

PIEZOMETER INSTALLATION RECORDS ........................................................................................ G

CRUMB TEST RESULTS .............................................................................................................................. H

DOUBLE HYDROMETER TEST RESULTS ........................................................................................... I

SIEVE ANALYSIS WITH HYDROMETER .............................................................................................. J

CONSOLIDATED UNDRAINED TRIAXIAL TEST RESULTS ....................................................... K

TIMBER PILE ULTIMATE CAPACITY CURVES ................................................................................ L

L-PILE PARAMETERS ................................................................................................................................ M

PROPOSED BULKHEAD SECTION ....................................................................................................... N

GLOBAL STABILITY OUTPUT RESULTS ............................................................................................O

1 EXECUTIVE SUMMARY

HVJ Associates, Inc. was retained by CobbFendley to provide geotechnical services for Deussen Park Improvements project in Harris County Precinct 1, Texas (Key Map No. 417D, 418A & 418E).

The proposed improvements include reconstruction of the existing bulkhead, parking lot and pedestrian bridge, and construction of new L-Shaped pier, boardwalk and trails. The project scope also includes providing erosion protection measures for shoreline erosion. The project site is shown in the Site Vicinity Map, Appendix A.

The purpose of this study is to perform a geotechnical investigation and provide recommendations for the above structures. The drawings and the related information for shoreline erosion were not available at the time of writing this draft report, hence the recommendation for the shoreline erosion protection measures will be provided in the revised report at a later date. Subsurface conditions at the site were investigated by drilling and sampling one (1) boring to a depth of 100 feet, one (1) boring to a depth of 80 feet, five (5) borings to a depth of 70 feet, two (2) borings to a depth of 50 feet, two (2) borings to a depth of 40 feet, three (3) borings to a depth of 15 feet, and fourteen (14) borings to a depth of 10 feet below the existing grade. Based on the subsurface conditions revealed by the soil borings, the findings and recommendations of this report are summarized below:

1. Firm to hard cohesive soils (CH, CL & CL-ML) were generally observed from the ground surface to the termination depths of the borings. Cohesionless soils (SM, SC, ML, SC-SM & SP- SM)) too were encountered in majority of the borings at varying depths. Please note that cohesionless soils were not encountered in borings BW-1, DP-4, DP-5, DP-7, HP-3, HP-4, HP- 5, SB-1, SH-2 and SH-4.

Details of the subsurface stratigraphy encountered in the borings are shown on the boring logs presented in Appendix E.

2. A literature review of surface faults near the project area was conducted based on the Scientific

Investigations Map 2874, Principal Faults in the Houston, Texas metropolitan area by Shah, S.D., and Lanning-Rush, J, 2005. The primary objective of this review was to evaluate available information from published and open file reports. Based on our review, the project site is situated at about 9 miles northeast of Lee fault. A fault map is presented on Appendix D of this report. Faulting is not anticipated to impact the project site; however, it should be noted that unmapped faults that could impact the project may exist within the project area. A detailed fault study is not within the scope of this study.

3. Groundwater was encountered at depths varying between 0.5 and 10.8 feet below the existing grade during drilling operations. Based on the water level observed in the piezometers, groundwater was observed at depths varying between 2.3 and 4.3 feet (El. 42.71 to El. 41.46) below the existing grade. Please note that borings LP-2, SB-1, SH-3 and SH-4 were drilled in water. It should be noted that groundwater levels determined during drilling may not accurately reflect the true groundwater conditions, and therefore should only be considered as approximate. Groundwater levels measured in open standpipe piezometer are more accurate;

however, these readings will fluctuate seasonally and in response to rainfall.

4. Lateral earth pressure coefficients for the bulkhead wall design are provided in Section 6.2 of the report.

i

5. LPILE parameters for lateral load analysis are based on a general subsurface soil and are presented in Appendix M.

6. Global stability analysis was performed for the proposed design configuration of the bulkhead wall based on the typical section provided by CobbFendley. The stability analysis was performed considering end of construction (short-term), long term and rapid drawdown loading conditions.

The sheet pile wall embedded 16 feet deep, with the design configuration presented on bulkhead section in Appendix N meets the required safety factors for slope stability analysis. The global stability analysis results are summarized in the table below and can be found in the outputs presented in Appendix O.

Table 1-1 – Global Stability Analysis Results

Location Proposed Sheet Pile

Length

Factor of Safety

End of Constructi on (Required

FOS = 1.3)

Long Term

(Required

FOS = 1.5)

Rapid Drawdown (Required

FOS = 1.1 to 1.3)

BH-3 (PZ-1)

(Based on borings BH-1 &

BH-3 (PZ-1))

16 feet 4.1 2.2 1.8

BH-5 (Based on borings BH-2, BH-4 & BH-5)

16 feet 2.0 2.1 1.5

7. We understand that driven timber piles will be used as a foundation system to support the pedestrian bridge, elevated boardwalk and L-shaped piers. The foundation recommendations for the above structures are presented in Section 7.

8. Pavement recommendations for the construction of concrete trail, access roads and parking lots are presented in Section 8 of the report. The recommendations on subgrade for sailboat launch ramp are also presented in Section 8.

Please note that this executive summary does not fully relate our findings and opinions. Those findings and opinions are only presented through our full report.

ii

2 INTRODUCTION

2.1 Project Description

HVJ Associates, Inc. was retained by CobbFendley to provide geotechnical services for Deussen Park Improvements project in Harris County Precinct 1, Texas (Key Map No. 417D, 418A & 418E).

The proposed improvements include reconstruction of the existing bulkhead, parking lot and pedestrian bridge, and construction of new L-Shaped pier, boardwalk and trails. The project scope also includes providing erosion protection measures for shoreline erosion. The project site is shown in the Site Vicinity Map, Appendix A.

The purpose of this study is to perform a geotechnical investigation and provide recommendations for the above structures. The drawings and the related information for shoreline erosion were not available at the time of writing this draft report, hence the recommendation for the shoreline erosion protection measures will be provided in the revised report at a later date.

2.2 Purpose and Scope of Work

The purpose of this study is to provide design recommendations for the proposed structures. The study was performed in accordance with the Harris County Engineering Department (HCED) Guidelines for Consultants performing Geotechnical investigations dated January 01, 2011 and HCED Regulations for the Approval and Acceptance of Infrastructure dated September 29, 2020.

The objectives were accomplished by:

• Drilling 28 soil borings to depths varying between 10 and 100 feet below the existing grade to determine soil stratigraphy and to obtain samples for laboratory testing;

• Installing two piezometers to gain an understanding of the groundwater conditions at the project site;

• Performing laboratory tests to determine physical and engineering characteristics of the soils; and,

• Performing engineering analyses to develop design recommendations for the proposed structures.

Subsequent sections of this report contain descriptions of the field exploration, laboratory testing program, general subsurface conditions and design and construction recommendations for the proposed structures.

3 FIELD EXPLORATION

3.1 Geotechnical Borings

The field exploration program undertaken at the project site was performed between March 7th and 29th, 2022. The subsurface conditions were investigated by drilling 28 soil borings to depths varying between 10 and 100 feet. Four borings SB-1, LP-2, SH-3 and SH-4 were drilled in water. The boring details are provided in Table 3-1. No odor was observed or detected during our investigation to suggest any environmental concerns. Two borings were converted into piezometers to obtain long term water level readings. The borings were drilled using truck and buggy mounted drilling equipments using wet and dry augering techniques. All the borings with exception to the borings converted into piezometers were backfilled with non-shrink grout using tremie method after obtaining the 24-hour water level readings. Approximate boring and piezometer locations are presented in Appendix B.

3.2 Survey Data

The survey data of borings provided by CobbFendley is summarized in the table below.

Table 3-1 – Boring Details

Location Structure Boring No.

Depth, Feet Northing Easting

Elevation (feet)

Deussen Park

Bulkhead

BH-1 70 13900975.55 3188975.05 45.18

BH-2 70 13901173.87 3188865.61 44.44

BH-3(PZ-1) 70 13901366.76 3188661.69 45.71

BH-4 70 13901530.58 3188447.07 44.91

BH-5 70 13901625.91 3188293.75 46.58

Sail Boat Ramp

Launch

SB-1* 15 13902871.96 3188432.62

40.09

L- Shaped Pier

LP-1 100 13901685.75 3188104.48 45.53

LP-2* 80 13902929.85 3188379.64 40.29

Shoreline Erosion

Protection

SH-1(PZ-2) 40 13901662.16 3187503.02 45.01

SH-2 40 13901958.89 3187559.44 45.41

SH-3* 15 13902834.09 3187896.75 40.99

SH-4* 15 13903137.29 3187895.58 40.09

Pedestrian Bridge at Tributary

BR-1 50 13901241.54 3187861.77

43.41

Parking Lot, Access Roads and

Trails

DP-1 10 13900587.36 3188805.19 51.79

DP-2 10 13900832.42 3188745.7 48.08

DP-3 10 13901168.26 3188576.21 46.41

DP-4 10 13900824.21 3188453.51 48.32

DP-5 10 13900856.48 3188097.77 47.72

DP-6 10 13901059.15 3188359.12 45.33

DP-7 10 13901211.03 3188250.08 52.19

DP-8 10 13901415.11 3188258.31 54.06

DP-9 10 13901468.18 3187607.98 45.06

Eisenhower Park

Trails

HP-1 10 13899157.96 3189985.87 45.18

HP-2 10 13898962.41 3189554.47 44.44

HP-3 10 13899031.93 3189084.39 45.71

HP-4 10 13898784.52 3188678.1 44.91

HP-5 10 13899336.98 3188858.39 46.58

Location Structure Boring No.

Depth, Feet Northing Easting

Elevation (feet)

Elevated Boardwalk

BW-1 50 13898474.82 3188498.27

46.91

Note: *- These borings were drilled in water.

Coordinates shown are in U.S. Feet and are referenced to U.S. State Plane Texas South Central Zone, North American Datum 83. Elevations are referenced to North American Vertical Datum

(NAVD) 88.

3.3 Sampling Methods

Soil samples were obtained continuously to a depth of 20 feet and then at 5-foot intervals thereafter to the termination depth of the borings. The samples were obtained continuously to the termination depths for the borings less than 20 feet deep. Cohesive soil samples were generally obtained with a three-inch thin-walled (Shelby) tube sampler in general accordance with ASTM D-1587 standard.

Cohesionless soils were generally sampled with the split spoon sampler in accordance with ASTM D-1586 standard. Each sample was removed from the sampler in the field, carefully examined, and then classified. Suitable portions of each sample were sealed and packaged for transportation to our laboratory. Detailed descriptions of the soils encountered in the borings are given on the boring logs presented in Appendix E. A key to the soils classification and symbols used in the boring logs is also presented in Appendix E.

3.4 Water Level Measurements

The groundwater level in the borings were measured during drilling operations and 24 hours after drilling. Borings BH-3 (PZ-1) and SH-1 (PZ-2) were converted into piezometers to obtain the 24-hour, and 30-day water level readings. Groundwater measurements are presented in Section 5.4.

Piezometer installation records are provided in Appendix G.

4 LABORATORY TESTING

Selected soil samples were tested in the laboratory to determine applicable physical and engineering properties. All tests were performed according to the relevant ASTM Standards. These tests consisted of moisture content measurement, percent passing No. 200 sieve, Atterberg limits and unconfined compression (UC), unconsolidated undrained (UU), crumb, double hydrometer, sieve analysis with hydrometer, and consolidated undrained (CU) triaxial compression tests.

The Atterberg Limits and percent passing number 200 sieve tests were utilized to verify field classification by the Unified Soils Classification System crumb and double hydrometer tests were conducted to identify the presence of dispersive soils and the compression tests were performed to obtain the undrained and drained shear strength parameters of the soil. Sieve analysis was performed to obtain gradation of the soil. The type and number of tests performed for this investigation are summarized below:

Table 4-1 – Type and Number of Laboratory Tests

Type of Test Number of Tests

Moisture Content (ASTM D2216) 213

Atterberg Limits (ASTM D4318) 119

Type of Test Number of Tests

Percent Passing No. 200 Sieve (ASTM D1140) 138

Unconfined Compression (ASTM D2166) 15

Unconsolidated Undrained (ASTM D2850) 38

Sieve Analysis with Hydrometer (ASTM D422) 2

Crumb Test (ASTM D6572) 4

Double Hydrometer Test (ASTM D4221) 1

Consolidated Undrained Triaxial (ASTM D4767) 4*

Note: *- Please see the note under Table 4-4.

The laboratory test results are presented on the boring logs in Appendix E. The conversion between pocket penetrometer readings obtained in the field to the shear strength parameters presented in the borings logs were obtained using a conversion factor of 1/2. A summary of laboratory test results is provided in Appendix F.

4.1 Dispersive Tests for Cohesive Soils

Crumb and double hydrometer tests were conducted to identify the presence of dispersive soils at the project location. Crumb tests were assigned on selected soil samples. The results of crumb tests indicate that the cohesive soils observed in the borings are non-dispersive to intermediate . The double hydrometer test was assigned to the intermediate soil, thereafter. The test results are summarized in Table 4-2 below. Results of crumb and double hydrometer tests are presented in Appendix H and Appendix I, respectively.

Table 4-2 – Crumb & Double Hydrometer Test Results

Boring Depth, Feet Sample Description Crumb Test

Double Hydrometer Test

SH-1 (PZ-2) 2-4 Silty Clayey Sand (SC-SM) Non-Dispersive Not Performed

SH-1 (PZ-2) 6-8 Fat Clay (CH) Non-Dispersive Not Performed

SH-2 0-2 Fat Clay w/ Sand (CH) Intermediate Non-Dispersive

SH-2 8-10 Sandy Lean Clay (CL) Non-Dispersive Not Performed

4.2 Sieve and Hydrometer Test Results

Pedestrian bridge foundations over waterways generally require scour analysis. We performed sieve analysis and hydrometer tests on the sample obtained at about bedding depth zone to obtain soil parameters (D50 and D95) that may be required for scour analysis. The D50 value is the diameter of the soil particle for which 50% of the material is coarser and 50% of the material is finer and D95 value is the diameter of the soil particle for which 95% of the material is coarser and 5% of the material is finer. The test results are presented in Appendix J and summarized in Table 4-3.

Table 4-3 – Sieve Analysis and Hydrometer Test Results

Boring Depth, Feet Soil Description D50, mm D95, mm

BR-1 6-8 Clayey Sand (SC) 0.08 0.16

BR-1 10-12 Clayey Sand (SC) 0.10 0.20

4.3 Consolidated Undrained Triaxial Tests

We performed four consolidated undrained (CU) triaxial compression tests to estimate the drained shear strength of the soil. The results of the CU tests are provided in Table 4-4 and the laboratory data is presented in Appendix K.

Table 4-4 – Consolidated Undrained Triaxial Test Results

Boring Depth, Feet Soil Description

Liquid Limit

Plasticity Index c’, psf ø’, degrees

BH-1 12-14 Lean Clay (CL) 37 20 152 26.3°

BH-3 (PZ-1) 8-10 Fat Clay (CH) 80 57 260 19.8°

Note: - We performed 2 more CU tests in borings SH-1 (PZ-2) and SH-2 but the tests were interrupted due to power failure and the test results turned out to be incorrect. Therefore, the results are not presented in this report.

Where:

c’: Consolidated Drained Cohesion ø’: Consolidated Drained Friction Angle

5 SITE CHARACTERIZATION

5.1 General Geology

There are two major surface geological formations that exist in the Gulf area: the Beaumont formation and the Lissie formation. The Beaumont formation is a relatively younger formation generally found to the southeast of the Lissie formation. The Beaumont formation dips southeastward and extends beneath beach sand and waters of the Gulf of Mexico as far as the continental shelf. The project site is located in an area where the Beaumont formation is typically encountered in the vicinity of Alluvium formation. A geology map is presented in Appendix C.

The Beaumont formation was deposited on land near sea level in flat river deltas and in inter-delta regions. Soil deposition occurred in fresh water streams and in flood plains (as backwater marsh and natural levees). The courses of major streams and deltaic tributaries changed frequently during the period of deposition, generating within the Beaumont clay a complex stratification of sand, silt and clay deposits. Frequently, stream courses were diverted significant distances from a given point in a backwater marsh, and the water overlying the soil would evaporate since it was cut off from a drainage path. Such water, which would be highly alkaline, would precipitate large nodules of calcium carbonate (calcareous nodules) throughout the surface of evaporation. With the coming of the Second Wisconsin Ice Age, the nearby sea withdrew, leaving the formation several hundred feet above sea level and permitting the soil to desiccate. The process of desiccation compressed the clays in the formation such that they became significantly overconsolidated to a large depth. In addition to preconsolidating the soil, the process of desiccation, together with the later rewetting, produced a network of fissures and slickensides that are now closed but which represent potential planes of weakness in the soil.

Alluvium consists of clay, silt, and sand organic matter, abundant locally and includes point-bar, natural levee, stream channel, backswamp, coastal marsh, mud flat, and narrow beach deposits that are shown by line symbol.

5.2 Geologic Faulting

The tectonic history of the Texas Gulf Coast includes a relatively stable depositional cycle since the Cretaceous Period (about 65 million years). During this period the area was subjected to deposition of clays, silts, and sands resulting in over 30 thousand feet of sedimentary rocks. Underlying this clastic sequence are salt formations, which have migrated upwards to produce the typical salt dome features associated with the Texas Gulf Coast. In conjunction with salt movement, dewatering and compaction of some of the deeper sediments in the basin have resulted in the development of growth faults.

A literature review of surface faults near the project area was conducted based on the Scientific Investigations Map 2874, Principal Faults in the Houston, Texas metropolitan area by Shah, S.D., and Lanning-Rush, J, 2005. The primary objective of this review was to evaluate available information from published and open file reports. Based on our review, the project site is situated at about 9 miles northeast of Lee fault. A fault map is presented on Appendix D of this report.

Faulting is not anticipated to impact the project site; however, it should be noted that unmapped faults that could impact the project may exist within the project area. A detailed fault study is not within the scope of this study.

5.3 Soil Stratigraphy

Our interpretation of soil and groundwater conditions at the project site is based on information obtained at the boring locations only. This information has been used as the basis for our conclusions and recommendations. Significant variations maybe encountered at areas not explored by the project borings. If such variations are observed, reevaluation of our findings and conclusions will be required. Firm to hard cohesive soils (CH, CL & CL-ML) were generally observed from the ground surface to the termination depths of the borings. Cohesionless soils (SM, SC, ML, SC-SM & SP-SM)) too were encountered in majority of the borings at varying depths. Please note that cohesionless soils were not encountered in borings BW-1, DP-4, DP-5, DP-7, HP-3, HP-4, HP-5, SB-1, SH-2 and SH-4.

Details of the subsurface stratigraphy encountered in the borings are shown on the boring logs presented in Appendix E.

5.4 Groundwater Conditions

The groundwater level in the borings were measured during drilling operations, 24 hours and 30 days after drilling. Borings B-8 (PZ-1) and B-12 (PZ-2) were converted into piezometers to obtain the 24-hour and 30-day water level readings. The groundwater observations are presented in Table 5-2.

Table 5-2 – Groundwater Observations

Location Structure Borings

Groundwater Depth Below Existing Grade (Feet)

During Drilling

24 Hours After Drilling/Piezometer

Installation

30 Days After Piezometer Installation

Deussen Park

Bulkhead

BH-1 5.5 2.1 --

BH-2 3.2 2.0 --

BH-3(PZ-1) 8.3 4.3 3.5

BH-4 5.5 3.2 --

BH-5 6.6 6.5 --

Location Structure Borings

Groundwater Depth Below Existing Grade (Feet)

During Drilling

24 Hours After Drilling/Piezometer

30 Days After Piezometer

Sail Boat Ramp

Launch

SB-1* At Surface -- --

L- Shaped Pier

LP-1 10.7 3.2 --

LP-2* At Surface -- --

Shoreline Erosion

Protection

SH-1(PZ-2) 2.2 3.2 2.3

SH-2 10.8 3.2 --

SH-3* At Surface -- --

SH-4* At Surface -- --

Pedestrian Bridge at Tributary

BR-1 3.3 0.5 --

Parking Lot, Access Roads and

Trails

DP-1 Dry 7.4 --

DP-2 5.6 Caved-in at 4.8 --

DP-3 6.3 3.0 --

DP-4 Dry 5.3 --

DP-5 Dry 4.7 --

DP-6 6.3 1.7 --

DP-7 Dry Caved-in at 7.8 --

DP-8 Dry Caved-in at 8.4 --

DP-9 Dry 1.2 --

Eisenhower Park

Trails

HP-1 7.0 6.3 --

HP-2 6.5 1.3 --

HP-3 Dry 3.3 --

HP-4 Dry 3.5 --

HP-5 Dry 1.8 --

Elevated Boardwalk

BW-1 6.7 0.5 --

Note: * - The borings were drilled in water.

Groundwater was encountered at depths varying between 0.5 and 10.8 feet below the existing grade during drilling operations. Based on the water level observed in the piezometers, groundwater was observed at depths varying between 2.3 and 4.3 feet (El. 42.71 to El. 41.46) below the existing grade.

Please note that borings LP-2, SB-1, SH-3 and SH-4 were drilled in water. It should be noted that groundwater levels determined during drilling may not accurately reflect the true groundwater conditions, and therefore should only be considered as approximate. Groundwater levels measured in open standpipe piezometers are, on the other hand are more accurate; however, these readings will fluctuate seasonally and in response to rainfall.

6 BULKHEAD DESIGN AND CONSTRUCTION RECOMMENDATIONS

6.1 General

The project involves the design and construction of a new bulkhead wall for the repair of erosion damage along lake shore periphery. Based on the cross section provided to us, we understand that the proposed bulkhead wall is planned to have an approximate height of 6 to 8 feet from surface to mudline and will extend for about 1300 feet along the lake shore periphery.

Based on the bulkhead typical section provided by CobbFendley and presented in Appendix N, we have performed global stability analyses considering the general subsurface conditions encountered at the site. The following sections provide recommendations for the design and construction of the proposed bulkhead wall.

6.2 Lateral Earth Pressures

The lateral earth pressures exerted on a bulkhead wall are mainly a function of the subgrade soils.

The at-rest, active and passive earth pressure coefficients for full soil profile are summarized below.

Table 6-1 – Lateral Earth Pressure Parameters

Depth Below

Grade at Top of

Bank, Feet

Soil Description

Total Unit weight (pcf)

Lateral Earth Pressure Coefficients

At- Rest Ko

Active Ka

Passive Kp

BH-3 (PZ-1)

(Based on borings BH-1 &

BH-3 (PZ-1))

Surface - 8.0 Sand (Backfill) 120 0.53 0.36 2.77

8.0 - 15.0 Clay 129 1.06 0.53 1.89

20.0 – 30.0 Clay 130 1.06 0.49 2.04

BH-5 (Based on borings BH-2, BH-4 & BH-5)

Surface - 8.0 Sand (Backfill) 120 0.53 0.36 2.77

8.0 - 20.0 Sand 120 0.50 0.33 3.00

20.0 - 30.0 Clay 130 1.06 0.51 1.97

Note: Based on our previous experience, we assume that it is unlikely that the soils below 30 feet will affect the bulkhead analysis.

The lateral earth pressure coefficients provided on the table above were determined based on a horizontal surface at the top of the bulkhead wall.

6.3 Soil Parameters for Lateral Load Analysis

LPILE parameters for lateral load analysis are presented in Appendix M.

6.4 Global Stability Analysis

Global stability analyses were conducted using SLOPE/W, a slope stability program that calculates the factor of safety against slope failure using a two-dimensional limiting equilibrium method. The

Morgenstern-Price method was employed to evaluate the factor of safety for the bulkhead wall design configuration.

The factor of safety represents the calculated resisting forces and moments divided by the calculated driving forces and moments of the various potential failure surfaces analyzed. These forces and moments are based on the estimated unit weights and shear strengths of the various soils in the profile. Accordingly, a factor of safety of 1.0 indicates impending failure. The larger the factor of safety is above 1.0, the lower the risk is that the slope will fail. As a practical matter, and in consideration of the variables and unknowns involved, the risk cannot be reduced to zero. The goal is to reduce the risk of failure to a reasonable and acceptable level, with consideration of the consequences of failure. For these, US Army Corps of Engineers EM 1110-2-1902 Slope Stability provides Minimum Required Factors of Safety: New Earth and Rock-Fill Dams (Chapter 3, Table 3- 1). The slope should have safety factors of 1.3, 1.5 and 1.1 to 1.3 for short term, rapid drawdown and long-term loading conditions, respectively.

6.4.1 Soil Parameters and Water Level

The soil parameters used in each case were estimated based on the field and laboratory data developed for this study and are presented in Table 6-2. Unconfined Compression (UC) and Unconsolidated Undrained (UU) tests along with Pocket Penetrometer values were utilized to obtain end of construction shear strength parameters. Consolidated Undrained (CU) triaxial tests were conducted to estimate the drained shear strength parameters of cohesive soils. For cohesionless soils, the parameters were determined based on SPT results (Ref., NAVFAC 7.1-149, Figure 7).

Short Term: The short term case is representative of the ‘end of construction’ state, where the soil is loaded quickly relative to the pore water pressure dissipation in cohesive soils. For this analysis, Unconfined Compression and Unconsolidated Undrained test results were used to estimate the undrained shear strength of cohesive soils. A surcharge of 1,000 psf was assumed to consider equipment traffic along the top of the bank during construction. The water level was considered at ordinary high water mark of El 43.0 feet.

Long Term: The long term design case represents steady state piezometric and stress conditions.

When the slope is constructed, altered stress conditions create pore pressure changes within the slope and the undrained strength of the bank soils is mobilized. With time, the soil pore pressures adjust to the imposed stress and piezometric conditions, and the bank soils rely on their available strength for long term stability. A surcharge of 350 psf was assumed to account for maintenance equipment traffic along the top of the bank. The water level was considered at ordinary high water mark of El 43.0 feet.

Rapid Drawdown: The rapid drawdown design case represents the rapid lowering of water level and associated stress conditions. When the water level is lowered in a short duration of time, it destabilizes the slope due to the development of excess pore pressures in the embankment consisting of low permeability materials (e.g. clay) and removal of stabilizing force on the upstream face of the slope due to water. The program SLOPE/W utilizes the Duncan et al.’s (1992) staged rapid drawdown method to evaluate slope stability after rapid drawdown. This is a 3-stage process:

The first stage involves the stability analysis before drawdown when the water level is high and the pore water pressure in the soils is at steady state condition. Both the effective normal stress and the shear stress along the slip surface are used to determine the undrained shear strength of the soils that do not drain freely.

The second stage involves the stability analysis after drawdown when the water level is low and the pore water pressure in the soils is in steady state condition. The effective normal stress obtained from stage two, together with the effective strength parameters are used to compute the drained strength along the slip surface. Both the drained and undrained strength at the slice base along the slip surface are compared and the smaller strength is chosen as the computed shear strength to be used.

The third stage involves stability analysis using the computed shear strength and final drawdown water level. The computed factor of safety from the first and second stages are ignored, and only the factor of safety computed from the third stage analysis is used to represent the stability after rapid drawdown. The water level was drawn down from the top of the bank to approximately bottom of the mudline at an elevation of about El. 38.0 feet for this loading condition.

Shear Strength Reduction (Weathered Soil Parameters): Overconsolidated high plasticity clays that are exposed at the surface, swell when exposed to water and shrink when dried. Alternate cycles of this process cause the strength of these clays to reduce over time after initial construction. The strength normally measured in the laboratory is referred to as the peak strength. Research has shown that the strength of high plasticity clay soils subject to prolonged shrink/swell cycles is the “fully softened” (mobilized) strength – which is lower than the peak strength. For the clay layers, the friction angle was obtained from empirical correlation between the plasticity index and the effective angle of internal friction for soft to stiff cohesive soils (Mesri and Ghaffar, 1993). The consolidated undrained test results were used to model the clay layer behind the fully softened (mobilized) zone.

Shear strength parameters of these soils have been reduced accordingly for the long term and rapid drawdown loading cases.

Table 6-2 presents the soil parameters used for global stability analyses.

Table 6-2 – Soil Parameters for Global Stability Analyses

(Borings)

Elevation, Feet

Soil Description γt, pcf

EOC

(Undrained

Shear Strength) Cu, psf/ Friction Angle

(Degree)

Plasticity Index (PI)

RDD/LT (Drained Shear Strength) c’peak, psf φ'peak, deg c’ fully softened, psf φ' fully softened, deg

BH-3 (PZ-1)

(Based on borings BH-

1 & BH-3

(PZ-1))

El. 45 - El. 39 Lean Clay

Layer I 125 820/0 17 150 26 -- --

El. 39 – El. 30 Fat Clay

Layer 125 850/0 57 200 18 50 18

El. 30 – El. 25 Lean Clay Layer II

125 2,500/0 24 150 26 -- --

BH-5 (Based on borings

BH-2, BH-4

& BH-5)

El. 45 - El. 41 Clay Layer 125 1,500/0 29 150 26 50 26

El. 41 – El. 37 Sand Layer I 120 0/28 NP 0 28 -- --

El. 37 – El. 25 Sand Layer II 120 0/30 NP 0 30 -- --

Where:

γt: Moist Unit Weight of Soil EOC: End of Construction cu: Unconsolidated Undrained Cohesion RDD: Rapid Drawdown c’peak: Peak Consolidated Drained Cohesion LT: Long Term φ’peak: Peak Consolidated Drained Friction Angle c’weathered: Consolidated Drained Cohesion Reduced for Weathering in the top 8 feet φ’weathered: Consolidated Drained Friction Angle Reduced for Weathering in the top 8 feet

6.4.2 Results of Global Stability Analyses

Global stability analysis was performed for the proposed design configuration of the bulkhead wall based on the typical section provided by CobbFendley. The stability analysis was performed considering end of construction (short-term), long term and rapid drawdown loading conditions.

The sheet pile wall embedded 16 feet deep with the design configuration presented on bulkhead section in Appendix N meets the required safety factors for slope stability analysis. The global stability analysis results are summarized in the table below and can be found in the outputs presented in Appendix O.

Table 6-3 – Global Stability Analysis Results

Proposed Sheet Pile

Length

Factor of Safety

End of Constructi on (Required

FOS = 1.3)

Long Term

(Required

FOS = 1.5)

Rapid Drawdown (Required

FOS = 1.1 to 1.3)

BH-3 (PZ-1)

(Based on borings BH-1 &

BH-3 (PZ-1))

16 feet 4.1 2.2 1.8

BH-5 (Based on borings BH-2, BH-4 & BH-5)

16 feet 2.0 2.1 1.5

6.5 Dispersive Soils

Dispersive soils, sands and silts are highly susceptible to erosion and piping are a major cause of slope distress in the Houston area. Dispersive soils are clays that disintegrate in the presence of relatively pure water as a result of their chemical composition. The results of crumb tests revealed the presence of non-dispersive to intermediate cohesive soils at the boring locations.

Rainfall and runoff on exposed slopes containing potential dispersive clays, sands and silts may result in surficial erosion which often results in rilling and gullying on the slopes. In other cases, standing water at top of the slopes may result in a distinctive erosion pattern referred to as “tunnel and jug hole”. The typical slope failure due to dispersive soils is depicted in Figure 6-1.

Figure 6-1 Typical Slope Failures due to Dispersive Soils (Ref., Soil Mechanics Note No. 13, USDA, 1991)

We recommend that water should not be allowed to accumulate behind the top of the wall. The finish grading adjacent to the shore should be sloped away not less than one vertical in twelve horizontal (1V:12H) for a horizontal distance of at least 10 feet. The surrounding site-finish grading should be established so that surface water runoff may be collected at areas of the site where it may be captured into a drainage structure. We recommend installing backslope interceptors/swale system installed at close intervals to quickly dissipate water from the ground surface.

6.6 Recommendations for Fill

We anticipate that adjustments to existing grade are planned to be made behind the new bulkhead wall. We recommend that onsite soils within the eroded zone be over-excavated and removed. The excavation should extend vertically and horizontally (into the slope) beyond the observed failure surface to expose undisturbed soils. We also anticipate that the slope is planned to be backfilled and regraded with sand material.

The sand material to be utilized as backfill should meet the following criteria:

Free of debris and organics.

Non-plastic.

Must have a maximum of 10 percent fines passing the No. 200 sieve.

Half of coarse fraction must pass the No. 4 sieve.

The sand backfill should be placed in lifts (maximum compacted thickness of 6 inches) and compacted to 95 percent of the standard Proctor maximum dry unit weight in accordance with

ASTM D698.

7 FOUNDATION RECOMMENDATIONS FOR PEDESTRIAN BRIDGE,

ELEVATED BOARDWALK AND L-SHAPED PIER

7.1 General

The project involves construction of pedestrian bridge and L-Shaped Pier in Deussen Park and elevated boardwalk near Eisenhower Trails. We understand that driven timber piles will be used as a foundation system to support the proposed structures. Details from the foundation recommendations for above mentioned structures are provided in the subsequent sections of this report.

7.2 Foundation Selection

Foundations for the structure must satisfy two basic design criteria. First, bearing pressure transmitted to the foundation soils should not exceed the allowable bearing capacity of the soils. Second, foundation movement due to soil volume change must be within desirable limits.

HVJ understands that driven circular timber piles would be used to construct the foundation for the proposed structures.

7.3 Analyses Criteria

The ultimate compressive capacity, Qult, for a given embedded length is taken as the skin friction along the pile/pier wall, Qs, and the end bearing at the tip, Qp. Skin friction in top 5 feet from point of installation has been ignored to account for construction disturbances and erosion, if any. Please note that for L-Shaped Pier, at boring location LP-2, skin friction in top 5 feet below the mudline has been ignored.

Q Q Q fA qAult s p sa E= + = +

Where: Asa = Embedded surface area f = Unit skin friction q = Unit end bearing AE = Cross-sectional end area

Ultimate compressive capacity curves that include skin friction and tip resistance for driven piles were developed based on several methods with the use of APILE Plus (by Ensoft Inc.), was utilized to model circular timber piles after consultation with Cobbfendley. The timber piles were considered to have butt diameters of 10-, and 12-inches.

Foundations may encounter lateral loading due to wind force. Lateral loads on a driven pile would be countered by the mobilization of resistance in the surrounding soils as the pile deflects. The lateral load capacity of the pile, therefore, will depend on its relative stiffness, and the strength of the surrounding soils. We recommend performing more detailed study to estimate lateral load capacity.

Lateral load analysis was beyond the scope of this study and should be performed using computer programs such as LPILE, etc. The input parameters for lateral load analysis are presented in Appendix M.

Ultimate capacity curves for 10-, and 12-inch diameter tapered timber piles are presented in Appendix L Tapered angle of 0.27 degrees is used. These curves were generated based on the boring BR-1 for pedestrian bridge, borings LP-1 and LP-2 for L-Shaped Piers, and boring BW-1 for elevated boardwalk. We recommend using capacity curves generated from Federal Highway Administration (FHWA) method. The design soil properties used to develop capacity curves are presented in Table 7-1.

Table 7-1 – Design Soil Properties

Location Boring

Ground -water Depth, Feet

Depth, Feet

Soil Description

Total Unit

Weight (pcf)

Undrained Cohesion, Su (psf)

Fric.

Angle, φ (deg)

Pedestrian Bridge

BR-1 3.3

0-14 Sand 120 - 30

14-25 Lean Clay 130 2,700 -

Location Boring

Ground -water Depth, Feet

Depth, Feet

Soil Description

Total Unit

Weight (pcf)

Undrained Cohesion, Su (psf)

Fric.

Angle, φ (deg)

25-30 Sandy Silty Clay 127 1,800 -

30-35 Sand 120 - 34

35-45 Lean/ Silty Clay 125 2,500 -

45-50 Silty Clay 125 3,800 -

Elevated Boardwalk

BW-1 6.7

0-18 Lean/Fat Clay 129 1,900

18-50 Lean/Fat Clay 128 3,200 -

L-Shaped Pier

LP-1 10.7

0-14 Lean Clay 125 1,300 -

14-16 Sand 120 0 28

16-35 Lean Clay 130 2,700 -

35-40 Lean Clay 125 1,100 -

40-80 Lean/Fat Clay 130 3,900 -

80-100 Lean/Fat Clay 124 3,000 -

LP-2*

At Surface (drilled on water)

0-12 Lean Clay 130 2,800 -

12-25 Lean Clay 130 3,300 -

25-30 Sand 120 0 30

30-40 Fat Clay 126 3,800 -

40-55 Sandy Silty/ Fat Clay 120 1,600 -

55-80 Lean/Fat Clay 130 3,000 - Note: *- Boring LP-2 was drilled in water. The surface elevation of boring LP-2 corresponds to the mudline.

7.4 Safety Factor

In order to determine the design allowable capacity, a factor of safety must be applied to the ultimate capacity presented. We recommend a factor of safety of at least three to be used to calculate allowable axial load.

7.5 Timber Pile Construction Recommendations

The performance of a timber pile foundation system is not only a function of the design of the foundation but also its construction. If either is deficient, the performance of the foundation may not be as desired. Construction control of timber piles is much more difficult than for shallow foundations where the footing excavation and footing construction can be visually observed to assure quality. Since piles cannot be seen after their installation, direct quality control of the finished product is impossible. Construction monitoring should be exercised in three areas; pile materials, installation equipment, and the estimation of static load capacity. The following guidelines according to “Timber Pile Design and Construction Manual, Timber Piling Council, American Wood Preserves Institute” should be followed when installing timber piles.

1. Timber piles should be monitored at the project site to assure that they meet project specifications with respect to length, size (butt and toe diameter), sapwood, straightness, twist of grain, knots, and pressure treatment. ASTM D 25-99 Standard Specification for

Round Timber Piles should be used for establishing the acceptance requirements for timber piles delivered to the project site.

2. The straightness of the piles shall also be checked. A straight line from the center of the butt to the center of the tip shall lie entirely within the body of the pile. Piles shall also be free from short crooks that deviate by more than 2.5 inches from straightness in any 5 feet length. Sound knots shall be no larger than one sixth the circumference of the pile located where the knot occurs.

3. The pile driving equipment, crane, leads, hammer, hammer cushion, and helmet are all important in the proper installation of a pile foundation. The inspector should check that the contractor’s driving equipment is in accordance with the project plans and specifications. The inspector should perform the following tasks prior to pile driving:

• Verify that the pile driving hammer meets the specifications for type and size.

• Hammer cushion (if used) meets the specifications for type, size, and thickness Helmet (drive cap) fits the pile.

• The lead system conforms to the project specifications.

4. The equipment necessary to install timber piles includes a crane that is capable of handling the loads from the pile driving equipment with sufficient capacity so that the reach of the crane does not limit the productivity of the installation process. The boom on the crane must be long enough to allow the maximum length pile to be installed without severely limiting the reach of the crane. The crane may be either a truck mounted or a crawler mounted rig. The selection of truck versus crawler will depend of the site conditions, maximum loads anticipated, and availability. The selection of the most economical crane for a project is typically left to the contractor.

5. There are two types of leads used for the installation of timber piles: swinging leads and fixed leads. The function of the leads is to maintain alignment of the hammer-pile system so that a concentric blow is delivered to the pile from the hammer for each impact. Regardless of the type of lead chosen for a project, the leads should keep the pile in good alignment with the hammer so that eccentric impacts which may cause local stress concentrations and pile damage are minimized.

6. There are two general categories of pile hammers; vibratory and impact hammers.

Vibratory hammers are typically not used to install timber piles.

7. The helmet is a heavy steel block between the hammer and the pile. The helmet should provide a smooth surface for contact between the hammer and the pile. The helmet should fit snugly over the pile (less than 2 inches of lateral movement). The top of the helmet is typically recessed for a hammer cushion. The hammer cushion is used to relieve the impact shock between the ram and the pile. Cushion materials eventually become compressed, lose their effectiveness, and must be replaced. Hammer cushion materials are usually proprietary man-made materials. Pile cushions, cushions between the pile butt and helmet are typically not required for timber piles, but are typically used for steel and concrete piles.

8. The selection of the hammer size for a project is an important consideration that will affect not only the performance of the pile but the efficiency with which the piles are installed. A hammer that is too small may not be able to install the pile to the required depth, capacity, or may require an excessive number of blow counts. A hammer that is too large may damage the pile. A wave equation analysis which considers the hammer cushion pile soil system may be used to determine the optimal hammer size.

9. An Inspector must be present during pile driving. Inspection of the pile driving equipment during driving is important to assure that the piles are installed so that they meet the driving criteria and that the pile remains undamaged. The driving criteria is often defined as a minimum driving resistance as measured by the blow count in blows per foot or fraction thereof, and is to assure that the piles have a desired capacity. The driving resistance is also a function of the performance of the pile driving hammer. A hammer operating at lower energy levels than specified will result in pile blow counts that are higher than for the same pile, with the same capacity, with the same hammer operating at a high energy level. In order for the inspector to assure that the minimum driving criteria has been met, and therefore that the capacity is adequate, she/he must evaluate if the hammer is performing properly. Each hammer has its own operating characteristics.

10. Pile driving records must be maintained for all installed piles. Pile driving records are an important part of the quality assurance program. The records provide information which greatly assists the design engineer in assessing the adequacy of the installed foundation system to support the design loads. Timber pile installation should not be complete without pile driving records.

8 TRAIL, PARKING LOT AND ACCESS ROAD PAVEMENT

RECOMMENDATIONS

8.1 General

We understand that the project includes construction of concrete trail, access roads and parking lots at the site.