Geotech_Report_1.pdf

FINAL REPORT FOR

THE PHASE I

. GEOTECHNICAL

INVESTIGATION

FOR THE

LAKE MICHIGAN I

CHICAGO RIVER

LEAKAGE CONTROL

INVESTIGATION

PREPARED FOR THE

ILLl.NOIS

DEPARTMENT OF

WATER RESOURCES

IDNR-OWR PROJECT .

#FR-401.

PATRICK

ENGINEERING INC.

PROJECT

NO. L6091.AO

DECEMBER 1997

l;;t.;jjr/133

ENGINEER.ING INC.

Transportation Infrastructure

. Environmental · Planning Architecture D.esign/Build

. Surveying

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TABLE OF CONTENTS

INTRODUCTION

Description of the Project

EXECUTIVE SUMMARY

EXPLORATION AND TESTING

Exploration Program Drilling and Logging Procedures Soil Sampling Procedures (ATV and Truck Rigs) Concrete Coring and Soil Sampling Procedures (Hand Auger and Tripod Rig) Water Level Measurements Decontamination Procedures Borehole Backfilling Procedures Laboratory Testing Program

PIEZOMETERAND WELL INSTALLATION METHOD

Piezometer and Pumping Well Installation Piezometer and Pumping Well Development Well Point Installation

SURVEYING

FIELD PERMEABILITY TESTING PROCEDURES

Slug Test Procedures Pump Test Procedures

FLOW MEASUREMENTS

RESULTS OF INVESTIGATION

General Diving Survey Dye Testing Soil Profile - Headlands ............................................................................ :

Soil Profile - North Pier Extension Groundwater Levels - Lake Michigan and Chicago River Elevations Slug Test Results Equilibrium Pump Test Results Hydraulic Conductivity from Pump Test Data Seepage Quantity - South Crib Seepage Quantity- North Pier

GROUNDWATER MODELING

SEEPAGE CONTROL OPTIONS

TABLES

Table 1 - Summary of Groundwater Elevations Table 2 - Summary of Slug Test Results Table 3A - Summary of April 17, 18, and 22, 1997 Equilibrium Pump Test Results Table 3B - Summary of April 24, 1997 Equilibrium Pump Test Results

EXHIBITS

Exhibit 1 - Boring Location Plan Exhibit 2 - Soil Profiles Exhibit 3 - Diving Inspection Plan (Provided in Appendix H) Exhibit 4 - Soil Description Terminology

APPENDICES

Appendix A- PEI Boring Logs (1997, 1996 and 1986) Appendix B - U.S. Corps ofEngineers Boring Logs (1963) Appendix C - Piezometer and Well As-Builts Appendix D - Laboratory Data Appendix E - Slug Test Results Appendix F - Equilibrium Pump Test Data Plots Appendix Fl - Equilibrium Pump Tests Data Plots for April 17, 18, and 22, 1997 Tests Appendix F2 - Equilibrium Pump Test Data Plots for April 24, 1997 Test Appendix G - MODFLQWTM Results Appendix H - Diving Survey Report Appendix I - Photographs Appendix J - Seepage Calculations h:\geo\6091 \aO\toc.doc

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INTRODUCTION

Description of the Project. At the request of the Illinois Department of Natural Resources

- Office of Water Resources (IDNR-OWR), Patrick Engineering Inc. (PEI) has performed a geotechnical investigation and groundwater study for the Lake Michigan/Chicago River

Headlands Area Leakage Control Project. The purposes of the study were to 1) determine the rate ofleakage that is occurring through the headlands, 2) determine the location where leakage is occurring, and 3) provide conceptual alternatives and cost estimates to reduce the leakage rate.

The project site is located in the area between Navy Pier and the Chicago River Lock in the City of Chicago, Illinois (see Exhibit 1). The study site includes the headlands bounded by the bulkheads on the east (Lake Michigan) and west (Ogden slip) and by the North Pier on the south side. The original shoreline (in the year 1820±) was located between 300 and 500 feet east of

Michigan Avenue or approximately 3,000 feet west of the site. The headlands area therefore consists entirely of reclaimed land, formed between the years 1820± and 1900±, partly by accretion and partly by filling. In the 1870s± the crib structure forming the southern end of the study area was constructed.

Presently, water from Lake Michigan is entering the Chicago River/Ogden Slip by leakage through the headlands area, including the North Pier located east of the headlands. This leakage is in defiance of the 1968 United States Supreme Court consent decree requiring the State of

Illinois to regulate the amount of water diverted from Lake Michigan and limiting the volume of water so diverted. Patrick Engineering was retained by the IDNR-OWR to perform a geotechnical investigation of the headlands area to determine the cause( s) of the leakage and to estimate the leakage rate from each source.

Patrick Engineering's Scope of Work is divided into two phases:

Phase I. Phase I consisted of investigating where and how the leakage was occurring, quantifying the amount of leakage, and identifying alternatives with preliminary projected costs for reducing the leakage to prevent further legal proceedings against the State of

Illinois.

Phase II. Phase II of the study will consist of the preparation of contract plans, specifications, and cost estimates for the construction of one of the selected remedial alternatives, if deemed to be economically feasible by the IDNR-OWR.

This report presents the results of the Phase I study.

EXECUTIVE SUMMARY

In February 1997 PEI completed its initial subsurface geotechnical investigation at the Site and prepared a progress report. The purpose of the Phase I progress report was to:

work:

1. Present the results of the initial subsurface geotechnical investigation and diving survey.

2. Recommend where additional borings/piezometers and a pumpmg well were needed to quantify the amount ofleakage occurring through the headlands.

As a result of the initial investigation, PEI recommended and performed the following

1. Constructed piezometers on GSA and MPEA property. All the borings/piezometers installed for the initial investigation were located on Corps of

Engineers' property. After securing right-of-entries from the General Services

Administration (GSA) and the Metropolitan Pier and Exposition Authority

(MPEA), PEI installed a total of three (3) borings/piezometers on these properties

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(P-1-97, P-2-97, and P-6-97, see Exhibit 1). The purpose of these borings was to . l

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Corps's property was present beneath the GSA and MPEA property.

2. Constructed additional piezometers within the rubble-filled south crib. As discussed in the progress report, the initial investigation included only one piezometer (P-2-96) located beneath the utility tunnel and screened within the rubble-filled crib. However, the measured hydraulic conductivity of this piezometer was three (3) to four (4) orders of magnitude greater than for those piezometers (nine total) located outside the crib and within the headland. In order to determine if this one slug test result was representative of the conditions within the crib, PEI installed three (3) additional piezometers within the crib and performed slug tests in the piezometers (P-3-97, P-4-97, and P-5-97, see Exhibit

1).

3. Constructed well points along North Pier. To determine the water levels (and whether any significant seepage is occurring) within the sheet pile cofferdam on the north side of North Pier and below the lower concrete-paved area on the south side ofNorth Pier, a total of three (3) well points were installed. Two of the well points (P-7-97 and P-10-97) were located on the north side of the pier while the third well point (P-12-97) was installed on the lower concrete-paved area on the south side of the pier. Several boring attempts (B-8-97, B-9-97, B-11-97, B-llA-97, B-13-97, B-14-97) were made in an attempt to install a second well point below the paved area. However, it was not possible to advance the hole through the large stone and cobbles beneath the concrete slab. Several voids were encountered below the slab on the south side of the pier (see boring logs B-9-97, B-9A-97, B-12-97, B-13-97, and B-14-97) and the diving survey detected flow in the northeast corner of the North Pier.

4. Conducted pump tests. A pumping well (PW-1-97) was installed within the south crib and several equilibrium pump tests were performed to determine the transmissivity of the crib fill and to estimate the seepage rate through the south crib. (The south crib is hereinafter defined as the area on the south side of the headlands. The North Pier is defined as the structure located east of the east crib, and is located entirely in Lake Michigan.)

5. Groundwater Modeling. A groundwater flow model of the headlands, specifically for the area in and around the rock-filled south crib, was developed using the

U.S.G.S. computer program MODFLOW. The purpose of the groundwater model was to simulate the area hydrology for use in predicting the groundwater flow rate through the headlands. The model was calibrated using static water level data collected in the piezometers. The seepage rate predicted by the model was consistent with the rate as calculated using physical data collected at the site.

6. Conduct Unde1Water Flow Velocity Measurements. Areas identified as potential major contributors to seepage through the cribs and North Pier were further investigated using a Global™ Flow Meter. The meter was used to measure the velocity of water exiting the North Pier and the west end of the south crib. Data collected was used to estimate the leakage rates from these areas.

The results of the Phase I study indicate there are two main areas where seepage enters the Chicago River. The area of highest leakage is at the comer where the North Pier turns south.

There is a large hole in the concrete block wall and large voids are apparent in the underwater video. (Photographs of this area are provided in Appendix I.) Leakage is also occurring through horizontal joints in the concrete block wall and numerous apparent lift holes in the concrete block.

Based on the flow measurements and estimated areas of the holes/joints, it is estimated that leakage through this area ranges between 25 cfs to 3 5 cfs, depending on Lake Michigan and

Chicago River water levels.

The second area where leakage is occurring is through a gap between the existing steel sheet pile and Wakefield wall located at the west end of the south crib. The source of this

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I l seepage is principally from the deteriorated sheet pile wall located on the east side of the headlands, just north of North Pier. Water from Lake Michigan enters the south crib via large gaps in the east crib wall. This water travels through the south crib, exiting at the southwest comer of the headlands. It is estimated that this leakage is on the order of 1 to 5 cfs.

Based on this investigation, there is minimal seepage occurring through the headlands itself. The soils within the headlands generally consist of layered clays and silty sands. The groundwater model predicts that the seepage rate through the headlands (excluding the south crib and North Pier) is less than 0.05 cfs.

Options to control seepage through the south crib concentrate on the sealing of the sheet pile wall along the east side of the headlands or controlling seepage so that the net inflow to the

Chicago River is minimized. Options evaluated include sheet pile wall replacement, grouting the stone-filled crib behind the wall, constructing a fill section within Lake Michigan to seal off the wall, and installing a pump station to extract water at a rate equal to or greater than the seepage rate. Feasibility level construction cost estimates for these options range from $25,000 to

$325,000.

Options to control the leakage rate through the North Pier concentrated on remediation of the concrete block timber crib wall located in the northeast comer of the Chicago River entrance channel. Options include complete removal/replacement of the concrete wall, grouting the voids within the crib, and constructing a new wall riverside of the existing wall and backfilling with concrete. Feasibility level cost estimates for these options range from $75,000 to _$250,000.

EXPLORATION AND TESTING

The investigation of site conditions included both a diving survey to determine the condition of the perimeter sheet pile walls and concrete walls surrounding the headlands and

North Pier and a comprehensive subsurface investigation. This section presents the methodology used to collect the subsurface information. The results of the diving survey are provided in

Appendix H. The results of the subsurface investigation are provided in a subsequent section of this report.

Exploration Program. The exploration program, developed by the IDNR-OWR and PEI, consisted of the following:

• Five (5) soil borings within the headlands property owned by the U.S. Army Corps of Engineers (Corps). All five borings were converted into either single or nested

(i.e., one shallow and one deep) piezometers. (Based on a previous subsurface investigation performed by Patrick Engineering for the Corps of Engineers [PEI

Report No. 247, May 1986], it was anticipated that two distinct pervious sand layers would be encountered within the fill. At four of the headland boring locations, two layers were indeed encountered and at those locations two piezometers were constructed [one piezometer in the shallow pervious sand layer and the second piezometer in the deeper pervious sand layer].) The piezometers are designated as P-lS-96, P-lD-96, P-3-96, P-4S-96, P-4D-96, P-SS-96, P-SD-96, P-6S-96, and P-6D-96. The purpose of these borings was to determine the general soil stratigraphy within the headlands. The piezometers were also used to obtain water level measurements to determine the groundwater flow direction, and to perform slug tests to estimate the transmissivity of the layered soil system.

• Three (3) soil borings on GSA and MPEA property. All three borings were converted into single piezometers, designated P-1-97, P-2-97, and P-6-97. These three piezometers were abandoned following completion of the pump tests. These borings and piezometers were used to confirm the data obtained from the borings made on Corps property.

• Four (4) soil borings and a pumping well (PW-1-97) within the rock-filled crib on the south side of the headlands property. All four borings were converted into \

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I I single piezometers (P-2-96, P-3-97, P-4-97, and P-5-97). These borings and well were used to estimate the transmissivity of the rubble-filled south crib.

• Well points were installed along North Pier. A total of six (6) well points were planned; however, only three (3) could be installed due to difficult drilling and the presence of boulders/cobbles within the pier. Two (2) well points were installed on the north side of North Pier. The purposes of these well points was to

1) determine if the clay fill as indicated on Corps of Engineers design plans was indeed present, and 2) to determine if the clay fill is effective in minimizing seepage through the north side of North Pier. The one well point constructed on the south side (within the crib) was used to determine the water level in the crib, specifically if it was higher than the water level in the Chicago River entrance channel.

All boring/piezometer/well point locations are shown on the Boring Location Plan, Exhibit 1.

Drilling and Logging Procedures. Prior to drilling, a field meeting to locate utilities was held with representatives from the Corps, the utility owners, Illinois Constructors (Corps contractor using the headlands area as a staging area for rehabilitation of the Chicago Lock sluice gates), and Patrick Engineering in attendance. Boreholes were offset to avoid utilities such as water, power, telephone, etc. and to minimize interference with Illinois Constructors' operations.

The subsurface exploration procedures were m accordance with standard Corps procedures and ASTM standards as indicated below:

1. EM 1110-1-1804, "Geotechnical Investigations"

2. EM 1110-2-1907, "Soil Sampling"

3. ASTM D 1586, "Penetration Test and Split-Barrel Sampling of Soils"

Borings in the headland area were made with either a truck-mounted rotary drill rig, Model No. 55, an ATV-mounted rotary drill rig, Model No. 75, or an ATV-mounted rotary drill rig, Model No. 45, all manufactured by the Central Mine Equipment Company (CME), St. Louis, Missouri. Boreholes were stabilized using 7%-inch O.D. by 4Y.-inch I.D. hollow-flight augers.

The well point borings were drilled using a tripod-mounted drill rig and concrete coring machine because of access and weight restrictions on the utility tunnel.

Eight borings (B-1-96, B-3-96 through B-6-96, B-1-97, B-2-97 and B-6-97) were drilled in the headlands area immediately north of the south crib. The subsurface conditions encountered in the borings are discussed in a subsequent section of this report. In order to investigate the conditions directly beneath the utility tunnel, and within its rock-filled timber crib (see cross section D-D', Exhibit 2), borings B-2-96, B-3-97, B-4-97 and B-5-97 and pumping well PW-1-97 were located immediately adjacent to the north side of the utility tunnel. Based on the results of this investigation, it is believed that the rock-filled timber crib is a primary "conduit" for leakage and, as such, the conditions encountered in these four ( 4) "crib" borings will be discussed in detail here.

The four ( 4) crib borings encountered approximately 6 to 7 feet of surficial silty clay fill before encountering the concrete footing for the utility tunnel. The borings were then advanced through the approximate 3- to 4-foot-thick tunnel footing/concrete crib cap which was encountered at a depth of approximately 6 to 7 feet below the ground surface. From a depth of

10 feet to approximately 30 feet, coarse gravel, sand, and cobbles were encountered. In boring

B-2-96, at a depth of approximately 21 feet, the hollow-flight augers encountered increased resistance and began to grind as they apparently encountered rubble fill placed as a mat foundation for the cribs. At a depth of approximately 27 to 29 feet, the augers started to wander and bind as they apparently encountered the timber sides of the crib. At a depth of approximately

29 feet, soft gray silty clay was encountered. The other borings encountered soft gray silty clay at depths ranging from 29 to 33 feet. The borings were terminated in this natural clay deposit at depths of approximately 33 to 36 feet. Two-inch-diameter piezometers were installed in all four

( 4) borings while a 6-inch-diameter PVC pumping well was installed in PW-1-97.

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All exploration was performed under the direction of an experienced geotechnical engineer or engineering technician. The technician maintained the daily drilling records, logged the soils, and selected representative samples for laboratory testing. The field logs, together with the laboratory tests, were used to develop the boring logs presented in Appendix A. The borings were logged according to the Soil Description Terminology and the locally adopted version of the

Unified Soil Classification System, ASTM D 2487-92, as presented in Exhibit 4.

Soil Sampling Procedures (ATV and Truck Rigs). The sampling procedures were dependent on the material encountered. Typically, 2-inch outside diameter split-spoon samples were obtained using the standard penetration test, ASTM D 1586. Occasionally, 3-inch-diameter j split-spoon samples were obtained when it was not possible to obtain representative samples of the larger gravel-sized fill materials using the 2-inch-diameter spoon. With the exception of

I B-1-96, which was not sampled, all borings were sampled continuously. (A previous investigation for a proposed maintenance facility at the Site (Patrick Engineering-1986) had

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/I several borings in the vicinity of the proposed location of B-1-96 and as such boring B-1-96 was drilled blind to allow the installation of a deep (P- lD-96) piezometer.) Although B-1-96 was not sampled, the grinding of the augers on apparent concrete from a depth of approximately 7.5 to

10.5 feet indicates that it was apparently drilled adjacent to the north face of the tunnel· footing/concrete crib cap. A shallow piezometer (P-1 S-96) was installed in an offset hole. For borings B-2-96 through B-6-96 and B-1-97 through B-6-97, the type of sample obtained and interval sampled, and the recovery/run are noted on the boring logs, Appendix A.

Representative samples obtained by the standard penetration (split-spoon) method were placed in 8-ounce glass jars, with additional jars used, as required, for material changes within the split-spoon sampler. Jar samples were sealed first by wrapping a 4-inch square sheet of aluminum foil over the mouth of the jar, then using twist-on lids. All jar samples were subjected to a head space scan using a photoionization detector (PID). The PID is a non-specific, trace gas detector of volatile organic compounds (VOCs ), including petroleum hydrocarbons such as benzene, toluene, etc. A Photovac MicroTlP™ with a lamp energy of 10.6 electron volts (EV) was used to screen the soil within the sealed sample jars for the presence of VOCs. The PID was calibrated in the field to detect the gaseous phase voes with a sensitivity of 0.1 parts per million (ppm).

The results of the PID scans are noted on the boring logs. It is noted that the PID detected very low levels (less than 10 ppm) of volatile organic compounds in the fill soils. Although analytical testing would be needed to determine the actual concentrations of VOCs in the samples, if any, the PID results indicate that it is unlikely any special handling or disposal procedures would be required if the site soils were to be excavated for the selected remedial option.

Concrete Coring and Soil Sampling Procedures (Hand Auger and Tripod Rig). The borings along the north side of North Pier (B-7-97 and B-10-97) were sampled using a 2-inch

O.D. hand auger to auger refusal in the coarse gravel and cobble layer. A tripod rig and 35-pound hammer were then used to attempt to drive a 2-inch O.D. split-spoon sampler into the coarse gravel layer, however, the layer could not be penetrated due to the large diameter of the fill material (typically greater than 2 inches).

The borings (B-8-97, B-9-97, B-9A-97, B-11-97, B-llA-97, B-12-97, B-13-97 and

B-14-97) through the lower concrete walk along the south side of the pier were made by coring through the concrete slab and removing the underlying materials by hand. It is noted that space limitations made it impossible to sample the coreholes using the tripod rig and a split-spoon. The concrete walkway was cored using a Dymorig No. 20 coring machine manufactured by

Milwaukee Electric Tool Company. A 4-inch-diameter diamond-impregnated core barrel was used to obtain the core.

Water Level Measurements. A water level measurement was made in each boring at the time water was first observed in the recovered samples or on the drill string. Water level measurements were obtained using an electronic water level indicator graduated to 0.01 foot.

Delayed water level measurements were made in all piezometers which were installed and are provided in Table 1.

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Decontamination Procedures. All drilling equipment was steam cleaned pnor to mobilization to the Site. The augers, drill rods and drill rig tooling were decontaminated after completion of each boring/piezometer made in the headlands using a steam generating pressure washer. Because of the potential for contamination to exist within the headland area and to prevent cross-contamination between boreholes, the split-spoon sampler and the engineer's logging tools were washed in a solution of Alconox and potable water, and rinsed with potable water prior to obtaining each sample. All washwater generated from the decontamination procedures was discarded near each boring as it was completed.

Borehole Backfilling Procedures. All boreholes which were not converted to piezometers

(i.e., those that were started but were abandoned due to obstructions encountered) were

. ~ abandoned by backfilling the borehole with bentonite chips. Details of the abandoned boreholes are provided on the boring logs. As discussed earlier, the piezometers on the GSA and MPEA

\ properties (P-1-97, P-2-97 and P-6-97) were removed and the boreholes grouted shut immediately following the conclusion of the equilibrium pump test. Coreholes made in the North f Pier were either grouted shut or the core was replaced in the hole and grouted.

Laboratorv Testing Program. Laboratory testing of select soil samples was performed at the PEI soils laboratory in accordance with ASTM procedures. The purpose of the laboratory testing program was to classify and determine engineering properties of the soils encountered.

The laboratory testing program included the following tests:

(1) Particle Size Distribution: particle size distribution (washed sieve) was determined in accordance with ASTM D 422.

(2) Moisture Content: moisture contents were detennined m accordance with

ASTMD 2216.

Laboratory tests were performed on samples selected by PEI. Results of the laboratory testing are included on the boring logs (Appendix A) and are presented in Appendix D. The test results were used to refine and revise (as necessary) the field classifications of the soils encountered.

PIEZOMETER AND WELL INSTALLATION METHOD

Piezometer and Pumping Well Installation. A total of sixteen ( 16) 2-inch-diameter PVC

(Schedule 40) piezometers were installed at the 12 boring locations. The installations were performed in accordance with ASTM D 5092, "Design and Installation of Groundwater

Monitoring Wells in Aquifers." In general, the following procedures were used to install each of the piezometers:

• Clean packaged # 10/20 silica sand filter pack was placed at the bottom of the hole

(6 inches minimum) to provide a base on which to set the piezometer screen.

• A 2-inch-diameter, 5-foot-long to 20-foot-long (#10 slot) PVC screen was then carefully lowered to the desired elevation. PVC riser pipe (2-inch diameter) was added above the screen as necessary to extend the piezometer to approximately 6 inches below the ground surface. Sand was placed around the screen to approximately 2 feet above the top of the well screen.

• A minimum 2-foot-thick bentonite chip seal was placed above the sand pack and allowed to hydrate for one hour.

• The remaining annulus was then filled with soil cuttings. A flush-mount steel well protector was installed over the piezometer riser at the surface. Piezometer installation reports are included in Appendix C.

A pumping well was constructed in boring PW-1-97. The well was constructed with 6-inch-diameter flush joint Schedule 80 PVC screen and riser. The screen was 20 feet in length with

0.010-inch machine made slots. An end plug was placed at the bottom of the screen and a vented

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I l cap was placed at the top. Filter pack installation, grouting, and surface completion were similar to the piezometers. An as-built diagram for the pumping well is included in Appendix C.

Piezometer and Pumping Well Development. Piezometer and pumping well development consisted of using a rig-mounted Moyno™ pump and purging and surging equipment. A

Teflon™ surge block was used to enhance the surging action of the pump. Development proceeded until the pumped water was clear to the unaided eye and a minimum of five times the piezometer casing volume or well casing volume was removed.

Well Point Installation. A total of three (3) 1 V.-inch-diameter low carbon steel (Schedule

40) well points were installed at boring locations B-7-97, B-10-97, and B-12-97. The well points were driven to approximately 1 inch below the ground surface using an approximately 35-pound weight falling 18 inches. An approximately 1-foot-thick bentonite chip seal was placed at the surface. A steel well protector was installed over the steel riser at the surface. Well point installation reports are included in Appendix C.

SURVEYING

The elevations of the piezometers, pumping well and boreholes were surveyed relative to the site benchmark system. The vertical control used, supplied by the U.S. Army Corps of

Engineers, were two Corps of Engineers brass disks with elevations referenced to Low Water

Datum (LWD) for Lake Michigan. For reference, 0.0 LWD = 578.10 USGS = -1.38 CCD (CCD

=Chicago City Datum). Elevations of the borings are inclu.ded on the boring logs (Appendix A) and the piezometer/well installation reports (Appendix C).

FIELD PERMEABILITY TESTING PROCEDURES

Slug Test Procedures. With the exception of piezometer P-4S-96, single well aquifer tests

(slug tests) were performed in each of the piezometers installed during this project. (Piezometer

P-4S-96 was screened in the silty clay surficial fill from a depth of 6 to 11 feet and was used to determine the presence, if any, of perched water at the Site.) Slug tests were performed in accordance with ASTM D 4044-91 "Field Procedure for Instantaneous Change in Head (slug tests) for Determining Hydraulic Properties of Aquifers."

The slug tests were conducted using a slug made of 1.3-inch diameter, 5-foot-long PVC pipe filled with sand and plugged at both ends. The volume of the slug was equal to the volume ofa 2-foot column of water in a 2-inch I.D. casing. For example, submersing the slug completely into the 2-inch I.D. piezometer resulted in a water level rise of 2 feet within the well. Likewise, removing the slug resulted in a water level drop of 2 feet. A Hermit 2000 Environmental Data

Logger, Model SE2000, Manufactured by In-Situ Inc., Laramie, Wyoming, and one pressure transducer was used to record the water level variation with time during the slug tests.

To conduct a slug test, the pressure transducer was first suspended in the piezometer at a depth of approximately 1 foot above the bottom of the piezometer and the connector cable was strapped securely to the casing. After allowing sufficient time for the water level in the piezometer to stabilize after the disturbance caused by inserting the transducer, the static water level was measured from the top of the casing using an electronic water level indicator in accordance with ASTM D 4750. The transducer was then connected to the Data Logger and the static water level was entered into the Data Logger recording system.

To start the test, the Data Logger was started and then, as quickly as possible, the slug was submerged below the static water level. This action resulted in a rise in water level in the piezometer which immediately began falling. The change in water level (head) with time was recorded by the data logger. When the water level in the piezometer returned to approximately the static water level, this step of the test was considered complete. The next test step was conducted by reinitializing the data logger and as quickly as possible removing the slug from the piezometer. This action resulted in a drop in water level in the piezometer which immediately began rising. The Data Logger recorded the water level rise until the water level returned to approximately the static water level.

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Each step in the slug test was repeated twice for each of the piezometers tested. The data from the Data Logger was viewed in the field and if inconsistencies were noted in the data, the test was performed again. (Tests which had inconsistent data were not counted in the number of tests run at each piezometer location.)

At the end of the day, the data was downloaded into a computer. The slug test data was subsequently reduced and analyzed. The results of slug test analyses are given later in this report and the plots are provided in Appendix E.

Pump Test Procedures: Several equilibrium pumping tests were conducted by pumping water from the pumping well (PW-1-97) at a known and constant rate and measuring the drawdown in select piezometers. The water levels were measured and recorded with In Situ

Troll™ pressure transducers for all the piezometers located in the crib plus piezometers P-lD-96, P-1 S-96, P-3-96, and P-6D-96. Transducers were used in these piezometers as they were the closest to the pumping well and would be the most affected (if at all by the pumping). The transducers were set below the anticipated drawdown in the piezometers to ensure that the transducers would remain submerged during the test. The water level measured by the transducers was automatically read and stored in the transducers. Each transducer was programmed to collect water level data at frequent time intervals in the initial stages of the drawdown and recovery tests when the water levels were changing quickly.

The water levels in the remaining piezometers P-4D-96, P-48-96, P-5D-96, P-58-96, P-68-96, P-1-97, P-2-97, and P-6-97) and all the well points were measured manually with an electronic water level indicator. (It is noted that manual measurements were also obtained in all the piezometers where a transducer was used. These water levels were used to check the accuracy of the data collected by the transducers. Comparisons of the pressure transducer and manual measurements showed that the transducers were functioning within their stated precision of0.015 ft.)

A 4-inch-diameter contractor's pump was used to pump water from the pumping well.

The flow rate was regulated by a gate valve connected to the discharge piping. The piping extended approximately 50 feet west from the well and discharged into the Chicago River. The flow rate was measured manually by measuring the time required to fill a 450-gallon plastic water tank and converting to gallons per minute.

The barometric pressure was noted periodically throughout each test so that corrections could be made (if necessary) for barometric-pressure-induced water level changes that might have occurred during the test. The barometric pressure did not change significantly (less than 3 mbar) during any of the tests and the calibration piezometers did not change. (Piezometers P-1-97, P-2-97, and P-6-97 were outside the radius of influence and were not affected by the slight

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FLOW MEASUREMENTS

The results of the diving survey (see Appendix H) indicated that there were two main areas where leakage was occurring into the Chicago River: 1) at the southwest corner of the headlands, near the west end of the south crib, and 2) at the northeast corner of the Chicago River entrance channel. Photographs of these areas are provided in Appendix I.

In order to better estimate the leakage rates from these areas, a Global™ flow meter was used to measure the flow velocity at numerous locations at the west end of the south crib and along the concrete block wall where the North Pier turns south (the northeast corner of the

Chicago River entrance channel). The flow was measured using the following procedure.

1. The flow meter was placed at the water surface and a measurement was obtained.

The meter was then lowered in 0.5-foot increments to a depth of approximately

6.5 feet. The meter was used at several locations along the pier/crib in an attempt

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to locate areas of high flow. Specific areas where flow measurements were obtained included the holes and gaps in the sheet pile and concrete block walls.

At each depth the flow was typically measured with the meter placed in three separate directions. For example, where the North Pier turns south, flow measurements were made with the flow meter aligned in the following directions:

A. North-South; B. Northwest-Southeast; and C. Northeast-Southwest. The purpose of performing these tests was to determine if flow was originating from a certain direction, which could be used to identify the source of the leakage.

RESULTS OF INVESTIGATION

General. During PEI's 1986 investigation for the Corps of Engineers, a small structure was present at the southwest corner of the headlands, approximately 15 feet north of the utility tunnel. This structure was razed sometime after 1986, however, its concrete floor slab and wall footing remain. At the time of this investigation the Site was vacant. The existing ground surface at the Site is relatively level with a very gentle slope to the east. The maximum relief between the borings is approximately 1 foot.

Diving Survey. An underwater inspection of the sea walls between Navy Pier and the

Chicago Lock was performed by Pro-Dive, Inc. under contract to Patrick Engineering. The main objective of the inspection was to locate any area where obvious seepage was occurring through the wall and to document the general condition of the sea wall surrounding the headlands. A complete copy of the inspection report is provided in Appendix H. A summary of the pertinent findings are summarized below. Photographs of the major flow areas are provided in Appendix I.

1. Flow into the headlands was detected below the concrete cap for the wood sea wall located on the east side of the headlands and north of North Pier. The area

(approximately 100 feet long) showed signs of suction (plastic bags stuck to the wall).

The wall was in poor to very poor condition, timber components were rotted, and the concrete cap was deteriorated.

2. No flow (or signs of flow) was observed into the north wall of the North Pier. The wall was generally intact and in good condition. (It is noted that due to the high lake levels, the sheetpile wall was overtopped by waves. Overtopping water could be infiltrating into the crib and causing leakage.)

3. Flow was detected near the northeast comer (Lake Michigan side) of the North Pier

(where the North Pier turns south). Flow was detected at the steel piling/concrete block intersection and through five 1. 5 inch diameter holes. Much of this area has toe stone, so the survey was limited in this area. Leakage may be occurring at depth.

4. Flow (estimated to be 5 to 10 gpm by the diver) detected on the west side of the south leg of the North Pier (into the Chicago River). Flow through crack of 1± inch wide.

Total flow area of 6 to 8 square inches.

5. Major flow detected through a 14-inch by 66-inch gap at the point where North Pier turns south. The flow appears to come from the west (through the stone-filled crib below the utility tunnel). Flow is also occurring through horizontal joints in the concrete block wall and through several lift holes.

6. Minor small leaks were observed in the sheet pile in the south crib at the east crib extended.

7. Flow was observed at the southwest comer of the headlands, at the northwest side of the south crib wall. Flow was observed coming from a hole in the timber crib, approximately 1 foot square in size. The flow was not strong enough to push the diver away.

8. The west crib wall was generally in poor condition. The wall is a timber Wakefield with occasional broken timbers.

Based on the diving survey, water is mainly entering the headlands and the North Pier both through the deteriorated east wall of the headlands and through the northeast comer of the North

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Pier. Flow is entering the Chicago River mainly at the northeast corner of North Pier and at the southwest corner of the headlands.

Dye Testing. Dye testing was performed in ten piezometers (P-lD-96, P-1 S-96, P-2-96, P-3-96, P-4D-96, P-4S-96, P-SD-96, P-SS-96, P-6D-96, and P-6S-96). The dye testing was performed by pumping between 200 and 400 gallons of green or red dye into the piezometer and recording the time it takes for the dye to emerge into the Chicago River entrance channel. If dye was not observed after approximately one to two hours, the next downstream piezometer was tested.

The only piezometer from which the dye emerged in the Chicago River entrance channel was P-lD-96. The dye emerged from the large opening just east of the timber dolphin within approximately 10 minutes. Assuming the dye flowed in a straight line through the crib, the average velocity of the flow would be on the order of 0.2 ft/sec. This velocity is consistent with the flow measurement of 0. 5 ft/sec made with the Global™ flow meter in the vicinity of the dolphin.

Soil Profile - Headlands. The soil conditions encountered at each boring location are described on the boring logs in Appendix A. An overview of the soil conditions encountered is provided in this section. The logs of the twelve (12) borings made during this investigation in conjunction with three (3) boring logs (CBB-1-86 through CBB-3-86) from the 1986 PEI investigation and by previous investigators (Corps 196J) were used to delineate soil strata at the

Site, see Exhibit 2. With the exception of the soil conditions encountered within the crib (which was discussed earlier), the fill within the headlands area was divided into six (6) layers, identified here as A through F. (It is noted that all six [ 6] layers were not encountered in every boring.)

The upper fill zone, Layer A, consists of dark brown to black silty clay fill having variable amounts of sand, gravel, cinders and brick fragments. This zone is approximately 5 feet thick and extends down to Elevation 5 L WD. Layer B consists of dark gray silty clay fill having a trace of sand and gravel, including shale pieces. Soil properties, determined during this and the 1986 investigation, including moisture content, Atterberg limits, particle size distribution, and shear strength, correlate well with those of the soft lake clay, Layer G, indicating this fill was probably dredged from the Chicago Harbor. This layer extends from a depth of approximately 5 to 13 feet

(El. 5 LWD to El. -3 LWD). As discussed earlier, piezometerP-4S-96 was screened inlayerB.

Layer C is a grayish-brown, clean, fine sand fill in a very loose to medium dense state.

Measured "N" values range from one (1) to twelve (12). This "shallow" layer extends to a depth of 20 feet (EI. -10 LWD). Piezometers P-lS-96, P-5S-96, and P-6S-96 were screened in this

"shallow" sand layer.

Layer D is a dark grayish-brown silty clay fill having medium stiff to stiff consistency and medium plasticity. Water contents and Atterberg limits from the 1986 investigation indicate this soil is similar to Layer B. Layer D extends to a depth of24 feet (El. -14 LWD).

Layer E is a grayish-brown fine sand fill in a loose to medium dense condition. Layer E is approximately 3 feet thick. This soil is similar to Layer C. Piezometer P-4D-96 was screened in

Layer E. Layer F, rubble fill, was encountered from a depth of approximately 27 feet to 30 feet.

This fill consisted of boulders, cobbles, timbers, etc. Larger materials were located near and in the timber cribs (see B-2-96) indicating this zone served as a mat foundation upon which the cribs were constructed. This layer may exhibit local variations in thickness and may be much greater than 3 feet in thickness. Piezometers P-lD-96 and P-3-96 were screened across Layers E and F.

Piezometers P-2-96, P-3-97, P-4-97 and P-5-97 were screened in the rubble fill within the timber crib beneath the utility tunnel.

All borings drilled for this investigation were terminated a few feet into the natural silty clay (Layer G) deposit at the Site. The following information on Layers G and H was obtained from the 1986 borings. Layer G extended from a depth of 30 feet to 60 feet (EI. -20 to El. -50

L WD) and consisted of soft clays of the Lake Border Morainic System. Layer H, located below the soft clay of Layer G, was very stiff to hard glacial till of the Park Ridge drift. The unconfined compressive strength of this soil is at least 3. 0 tsf i

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Soil Profile - North Pier Extension. Borings in the North Pier were made with either a tripod-mounted rig or a concrete coring machine. Borings B-7-97 and B-10-97 were made on the grass slope on the north side of the pier. At the surface both borings encountered approximately

2.5 feet of sand and clay fill. From a depth of approximately 2.5 feet to 3.0 feet both borings encountered coarse gravel and cobble fill. Below a depth of 3 feet it was impossible to drive the split-spoon sampler using the tripod rig, suggesting that the material below 3 feet was granular material having a large diameter. A total of three (3) additional boring attempts were made near boring locations B-7-97 and B-10-97, however, it was not possible to advance through the coarse gravel and apparent cobble fill. (The presence of granular material was not expected. Corps of

Engineers design drawings indicated that a 10-foot-wide clay seal was to have been constructed between the sheet pile wall and the crib. It remains unknown ifthe clay seal is present.)

Borings B-8-97, B-9-97, B-9A-97, B-11-97, B-llA-97, B-12-97, B-13-97 and B-14-97 were made through the lower concrete walkway on the south side of North Pier. (It is noted that only three borings were planned but a total of eight were drilled in order to estimate the limits of the void encountered beneath the concrete.) The concrete thickness ranged between 0.9 and 1.4 feet thick and was typically underlain by an apparent 1/8-inch-thick layer of tar paper. Four of the locations cored encountered either one or two layers of #6 reinforcing bars. Below the concrete, boring locations B-8-97, B-11-97, and B-llA-97 encountered coarse gravel and cobble-size limestone. The gravel and cobbles could not be sampled using a hand auger and instead had to be removed from the corehole by hand. As such, it was only possible to "sample" these three (3) borings to a depth of approximately 2 feet.

Voids were encountered beneath the concrete at borings B-9-97, B-9A-97, B-12-97, B-

13-97, and B-14-97. At B-14-97 the void was 0.2 feet, but at the other locations the void was approximately I foot. At all the locations the void extended laterally at least several feet in all directions. Below the void, coarse gravel and cobbles were present. Once again, it was impossible to "sample" more than a few inches of the gravel. The borings were terminated in the gravel layer.

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Groundwater Levels - Lake Michigan and Chicago River Elevations. Static groundwater elevations were measured on numerous occasions in each of the piezometers and well points installed during this project. An electronic water level indicator was used to measure the water level inside the piezometer or well casing. All measurements were recorded to the nearest 0.01 foot referenced to the top of the piezometer casing. Static groundwater levels are summarized in

Table 1. On those days when water level measurements were made in the piezometers, the elevation of Lake Michigan and the Chicago River were measured as well. Those measurements were also made to the nearest 0.01 foot using a 6-foot engineer's rule referenced to temporary benchmarks established by PEL Lake Michigan and Chicago River elevations are summarized in

Table I as well.

As expected, the piezometers indicate that the general flow of groundwater within the upper and lower sand layers at the Site is from east to west across the headlands. The water levels within the sand and clay fill (outside the cribs) was consistently higher than the water level in the south crib. This indicates that the south crib is a sink, collecting flow from the north. The data also indicates that the south crib is a conduit for the flow of water.

The water levels for the two well points constructed on the east side of North Pier (near the major leakage area) are near the river level. This suggests that there is not a gradient across the pier cross-section, indicating that either the clay fill is present on the north side of North Pier

(prohibiting flow into the pier) and/or the seepage rate into the North Pier is small compared to the discharge rate. The water level in P-7-97 (located on the west side of North Pier) was approximately 0.2 feet higher (based on numerous measurements made during the pump test) than the water level in the two well points located to the east. This suggests that there is a small flow gradient from west to east which is consistent with the fact that water is entering the south crib from the open section in the east crib. Water likely is entering the North Pier from the west and traveling along the pier, exiting at the weak area located at the northeast corner of the Chicago

River entrance channel.

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Slug Test Results. With the exception of the rubble-filled crib piezometers, slug test data for the piezometers was analyzed using the computer software AQTESOLV™ version 2.0, developed by Geraghty & Miller, Inc., Reston, Virginia. The Bouwer-Rice Solution for confined aquifer conditions available within AQTESOL yrM was used to estimate the hydraulic conductivity of the respective fill layers where the tests were performed. (Confined conditions were assumed for the sandy soil because they were generally overlain by fine grained soils and the piezometric surface was above the deposit being tested.) The crib piezometers (P-2-96, P-3-97, P-4-97, and P-5-97) typically recovered in a few seconds and an approximate hydraulic conductivity was estimated using the Springer-MIT method.

Table 2 summarizes the hydraulic conductivity of the different fill layers as determined from the slug tests performed in the piezometers. Where more than one test was performed for the same condition, the test which provided the more consistent data (better straight line fit) was selected to estimate the hydraulic conductivity of the formation. The output plots for each of the slug tests, as obtained from AQTESOL V™, as well as the Springer-MIT calculations are included in Appendix E.

In general, the slug test results indicate that the hydraulic conductivity values obtained by the "Slug Withdrawn" step are higher (i.e., faster) than the values obtained by the "Slug Inserted" step. A possible reason for this difference is that if a slug is inserted into the well, water can flow only through the annular space between the slug and the casing, i.e., the available cross-sectional area for flow is reduced. For highly permeable formations the flow through that annular space may not be sufficient, resulting in a flow rate which is lower (i.e., slower) than actually possible, which will result in a lower estimated hydraulic conductivity.