august 5, 2008 ls3p charleston, south carolina, 29401 wpc...

August 5, 2008 Mr. Richard Gowe LS3P 205½ King Street Charleston, South Carolina, 29401

Proposal for Existing Calhoun Street Drainage Tunnel Monitoring Concord Park Development Charleston, SC WPC Proposal CHS-472-2007 R1

Dear Mr. Gowe: As you are aware, there are concerns about damage to the existing City of Charleston Calhoun Street storm water drainage tunnel under the proposed development at Concord Park. As requested, WPC has examined the possible affects of driven pile foundations for the project on this tunnel. Using the results our examination and their own engineering analysis, Davis & Floyd concluded the proposed piling foundation will not endanger the structural integrity and long-term performance of the tunnel. In Davis & Floyd’s Recommendation for Deep Tunnel Easement Encroachment Effects of Concord Park Driven Pile Foundation on Existing Drainage Tunnel letter dated July 25, 2008, authorization of the proposed easement encroachment was recommended with the following conditions remaining in force:

1. Perform a pre-project inspection of the tunnel lining 2. Perform a comprehensive tunnel monitoring program starting with the test pile program

(with test piling being located within the easement) and continuing throughout the duration of piling installation within the drainage easement. A qualified geotechnical firm shall be responsible for monitoring loads and work shall stop in any event where loads used to qualify the subject conclusions are exceeded. Remedial measures and/or additional professional qualifications of such conditions being acceptable will be subject to approval of the City before work can be restarted.

3. Perform a post-project inspection of the tunnel lining.

Concord Park WPC Proposal CHS-472-2007 R1 Existing Calhoun St. Drainage Tunnel Monitoring and Test Pile Program August 5, 2008

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4. Maintain provisions for repair or replacement of the tunnel section should damage result as a consequence of structural encroachment within the tunnel easement.

In addition to the above Davis & Floyd conditions, we recommend a pre-condition survey of the surrounding buildings to protect the owner from allegations and lawsuits claiming damage from construction. Pre-condition surveys are routinely performed in the downtown area for driven pile projects. WPC recently performed an above ground pre-condition survey for the Anson House development and because of our documentation, a claim of over $100,000 was dismissed prior to involvement with attorneys. The estimated cost to conduct the monitoring requested by Davis & Floyd, the recommended pre-condition survey of the above ground neighboring structures, and the test pile program ranges between $171,000 to $201,000. The range in cost is due to uncertainties in the monitoring plan (e.g. number of gages required, number of mobile monitoring days required) and estimated costs in the post-condition tunnel inspection beyond WPC’s control. It is possible that the tunnel monitoring results from the test pile program can reduce the scope of the tunnel monitoring. A detailed estimated cost breakdown is provided in Table 1. Miscellaneous meeting time with the design team and City of Charleston officials will be invoiced based on our hourly rates (Principal @ $160.00 per hour, Senior Engineer @ $120.00 per hour, and Geotechnical Engineer @ $100.00 per hour). Our estimated costs include WPC’s portion (i.e. testing measurements, analysis, and recommendations) for the test pile program. The test pile program can refine pile design, potentially saving on pile lengths and/or number of piles required, which in turn can reduce project costs. Past WPC test pile programs in the area have resulted in savings of over $100,000 (e.g. 100 Calhoun Street building) from the final pile foundation costs. Subsequent sections of this proposal provide brief descriptions of our tasks associated with each of Davis & Floyd’s authorization conditions. A summary schedule showing estimated time for each WPC task is also provided, as is a brief description of our capabilities.


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Table 1. Estimated Tunnel Monitoring Cost Summary.

Davis & Floyd Condition No.

Associated WPC Task Descriptions

Cost Total Cost

1. Perform Pre-Project Inspection of Tunnel Lining

A. Pre-Condition Survey of Tunnel w/Report

$5,000

$13,0001 B. Pre-Condition Survey of Above Ground Neighboring Buildings

w/Report $8,0001

2. Perform Comprehensive Monitoring during Pile

Installation

A. Development and Submittal of Tunnel Monitoring Plan

$8,000

$123,000 to

$153,0003

B. Installation of Soil and Tunnel Instrumentation.

$84,0002

C. Test Pile Program Testing & Report $12,000

D. Mobile Soil Instrumentation Installed via In-situ Testing Rig

$30,0003

E. Instrumentation Monitoring during Pile Installation (12 wks @ $1,000/wk)

$12,000

F. Summary Instrumentation Monitoring Report

$8,000

3. Perform Post Project Inspection of Tunnel Lining

A. Post-Condition Survey of Tunnel $3,000 +

(Cost +10%) $15,0004

4. Maintain Provisions for Existing Tunnel Repair or

Replacement

A. Development and Submittal of Tunnel Repair/Replacement Plan

$20,000 $20,0005

NOTES: 1. Includes installation of ten (10) Crack Monitoring Devices (CMD’s) @ $50/each. 2. Includes two (2) instrumentation clusters within easement. Instrumentation clusters consist of one (1)

strain gauge and one (1) crack displacement monitor in tunnel; one (1) pieozmeter, one (1) triaxial geophone, and one (1) settlement gage in soil; and one (1) data acquisition system. Cost per cluster = $42,000. Also assumes access to the tunnel will be available at no cost to WPC.

3. Based on ten days of mobile monitoring @ $3,000 per day. Mobile monitoring may not be required depending on results of test pile program and/or instrumentation clusters in easement.

4. Cost + 10% resulting an anticipated cost of $11,000 to $12,000 for the crane, manbasket and the four accompanying personnel to conduct the survey. The cost for WPC’s portion will be a lump sum of $3,000.00.

5. For development of preliminary provisions. A proposal for detailed tunnel repairs will be submitted based on actual damage observed.


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SCOPE OF WORK Perform Pre-Project Inspection of Tunnel Lining A. Pre-Condition Survey of Tunnel

WPC proposes to visually examine and document the storm water tunnel owned and operated by the City of Charleston. Based on our meeting with the City of Charleston, the tunnel is due for a routine inspection and the City is willing to allow us to accompany their personnel. As such, the cost for this work will be only for our time and efforts. WPC will devote our time to examining only the segment of the tunnel that underlies the proposed development. Within this section, we will document the condition of the tunnel using a video camera as well as high resolution digital photographs. We will note and document any area that appears to be cracked or damaged. Our examination of the concrete tunnel lining will be conducted in accordance with American Concrete Institute (ACI) 201.1R-08 Guide for Conducting a Visual Inspection of Concrete in Service. From this work, WPC will issue a pre condition document that will identify any areas of pre-existing damage. The tunnel pre-condition survey will be used in the development of the tunnel monitoring plan. WPC proposes to perform the inspection of the tunnel in the following manner:

1. All OSHA confined space entry procedures will be adhered to under the supervision

of persons trained in confined space entry including gas monitoring, the use of a fresh air source and alternate breathing apparatus. We will use health & safety meters (PID, O2 and LEL) before personnel and lowered into the tunnel to check for toxic gasses. While in the tunnel our personnel will carry safety meters while they work.

2. The inspection team will consist of at least 5 persons to be used in the following manner: 1 person stationed topside at the entry to the drop shaft, 2 people stationed at the bottom of the drop shaft, and one person to accompany our WPC inspector in the tunnel.

3. The topside person will be responsible for coordination with City representatives and contact with emergency personnel if needed. Radio communication will be maintained with the stand-by staff at the bottom of the drop shaft and emergency extraction equipment will be available topside.

4. The two persons at the bottom of the drop shaft will monitor the progress and maintain radio communication with the two persons penetrating linearly into the


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tunnel. They will perform and coordinate emergency evacuation procedures with topside personnel if necessary.

5. The WPC inspector and his escort will carry gas monitoring devices, be in possession of alternate breathing apparatus and maintain contact with stand-by rescue staff during the entire process.

6. All activities will be coordinated with City of Charleston staff throughout preparation for and during the inspection process.

7. WPC will plan to perform the inspection in one day and careful planning around potential rain events. The tunnel is an active system and although the water levels will be lowered, we expect some water to be present. Thus the timing of both the pre and post condition surveys will be dependant on having clear weather with minimal chance of rainfall.

B. Pre-Condition Survey of Above Ground Neighboring Buildings WPC personnel will examine and photograph the exteriors of structures near the project site prior to the start of construction. The survey will document existing conditions and any significant cracks or damage present on the exterior of the nearby structures, and if requested the interior walls of identified structures facing the project site. Based on our examination of the site, we have identified twenty (20) properties near the planned building locations be examined during the pre-condition survey. Figure 1 shows the estimated extent of the above ground pre condition survey limits. A pre-condition survey report containing brief descriptions of the examined structures, the exterior photographs, the interior photographs if any, and a site plan showing the photograph locations will be provided at the conclusion of our work. The pre-condition survey report will also contain recommendations regarding any locations for crack monitoring device (CMD) installation. The report will be signed by a professional engineer registered in the state of South Carolina. WPC can install CMD’s at the recommended locations upon request. These devices will allow for measurement of expansion and/or contraction of existing cracks. CMD measurements provide additional documentation for analysis of the effects of construction/demolition activities on adjacent structures. WPC will also record relevant environmental conditions (e.g. temperature and relative humidity) to account for crack movements due to these factors.


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Figure 1. Proposed Above Ground Survey Limits (Blue).

Perform Comprehensive Monitoring during Pile Installation A. Development and Submittal of Tunnel Monitoring Plan

Using the results of the pre-condition tunnel inspection, the in-situ test data from WPC’s geotechnical exploration, and the results of our examination of the affects of driven pile installations on the existing tunnel, WPC will develop an integrated tunnel monitoring plan. The tunnel monitoring plan will:

Establish a tunnel coordinate system. The establishment of a coordinate system allows for easy reference on the structure, direct comparison of measurements from various


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types of instrumentation, and provides a common means of determining structure behavior.

Select instrumentation to monitor tunnel strain, existing tunnel crack movements, soil vibrations, and excess pore pressures generated due to driven pile installation. Proper selection of instrumentation will result in an effective monitoring plan.

Provide instrumentation installation details.

Determine instrumentation monitoring frequencies during construction activities.

Determine Threshold Values and Corresponding Action Plans for each instrument. Establishment of threshold levels and corresponding action plans for the various selected instruments will allow for rapid resolution of situations where pile installation may cause tunnel damage. Recommendations for threshold levels and corresponding action plans will be inter-dependant on all the available instrumentation (i.e. once a threshold level is reached, the corresponding action plan will be dependent on the measurements from all the gauges). An example of an instrumentation threshold level and corresponding action flow chart developed by WPC for the Morris Island Lighthouse Phase I Foundation Stabilization Plan is presented in Figure 2.

Provide Test Pile Program Recommendations. WPC will provide recommendations to incorporate the test pile program with the tunnel monitoring plan.

Upon completion of our tunnel monitoring plan, WPC will provide a tunnel instrumentation plan submittal for the City of Charleston to review. The tunnel instrumentation plan submittal will be signed by a professional engineer registered in the State of South Carolina.

B. Installation of Soil and Tunnel Instrumentation. Upon approval of the tunnel monitoring plan, WPC will install the selected tunnel and soil instrumentation. Based on our conceptual instrumentation plan developed during our evaluation of driven pile affects on the exiting tunnel, we anticipate the following instrumentation to be used:


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Figure 2. Example WPC Threshold Value and Decision Flowchart (from Morris Island Lighthouse Phase I Project).

Strain Gauges: These gauges will monitor changes in strain within the tunnel lining and can be correlated to construction events via time.

Crack Monitors: These gauges will monitor movements of existing tunnel cracks and can be correlated to construction events via time.

Vibration Monitors: These gauges will monitor vibrations within the Cooper Marl formation and will be placed between the intended pile locations and the existing tunnel. Note we also anticipate monitoring of surface ground vibrations during pile installation. However, while this data will be used in any assessment of potential tunnel damage, this monitoring will be accomplished by the field technicians conducting pile installation monitoring and is therefore not part of this proposal.

Vibration Monitoring (VM)

Threshold Level A

(0.1 in/sec) reached

Monitoring

Threshold Level B

(0.12 in/sec) reached

Continue Vibration Monitoring (VM)

Increase vibration monitoring frequency to 1 reading per minute.

Compare observed vibrations with other monitoring data.

Conduct visually examination of building exterior.

Halt PZ-40 sheet pile installation and/or other construction activities.

Compare observed vibrations with other monitoring data.

Conduct visually examination of building exterior and interior.

Re-evaluate vibration criteria and/or installation

YES YES

NO NO


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Piezometers: Vibration monitors will monitor pore pressures (i.e. water pressure) within the Cooper Marl formation and will be placed between the intended pile locations and the existing tunnel.

At the time of this proposal, WPC has not been provided the number of piles which will be within the tunnel easement. We estimate that two (2) pile groups will be located within the easement. We plan on one (1) instrumentation cluster per pile group, within one (1) of each gauge to be installed per instrumentation cluster. We note that the instrumentation clusters will be monitored throughout pile installation and can be setup to provide long-term monitoring of the tunnel, should that be desired. All of the soil and tunnel gauges within the instrumentation clusters will be attached to a data acquisition system (DAS) which will be installed onsite. A solar panel will be attached to the DAS to provide power. WPC personnel will access the data within the DAS via site visits or via a modem with a mobile phone. WPC will require that a security system such as fencing be installed around the DAS to protect it from disturbance and vandalism.

C. Test Pile Program Testing & Report WPC will monitor the piles and tunnel instrumentation during installation and load testing. We anticipate that the test piles will be monitored during installation using the Pile Driving Analyzer (PDA). Due to the time dependent pile capacity gain (i.e. pile “setup” or “freeze”) characteristics of the Cooper Marl, additional load testing will be required after pile installation to determine pile capacity. This load testing should consist of both dynamic and static load testing. Static load testing of the pile will allow for an assessment of the affects of long-term pile structural loading on the tunnel while dynamic load testing will allow for an evaluation of affects of multiple driven piles on the existing tunnel. At the conclusion of the test pile program, WPC will provide a test pile summary report detailing the various test results and providing recommendations for production pile lengths and installation procedures. The test pile program report will also provide the results of the tunnel instrumentation monitoring and recommendations for tunnel monitoring during production pile installation. The Test Pile Program report will be signed by a professional engineer registered in the State of South Carolina.



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In addition to the instrumentation clusters, we anticipate that additional soil monitoring may be required if (a) more than two (2) pile groups are located within the existing tunnel easement and/or (b) tunnel, soil, or pile measurements indicate the potential for tunnel damage at locations other than the instrumentation clusters. Mobile monitoring will consist of the installation of our piezocone penetration test (CPTu) equipment equipped with tri-axial accelerometers into the Cooper Marl near the existing tunnel at locations to be determined. This equipment will allow for ground vibration and excess pore pressure measurements within the Cooper Marl. Figure 3 presents a conceptual cross-section of the mobile soil instrumentation.

Figure 3. Conceptual Mobile Soil Instrumentation

(Section View. Not To Scale). Due to the pile “setup” characteristics of the Cooper Marl, the mobile insitu soil instrumentation cannot be installed for extended periods of time, as the increase in skin friction with time could prevent withdrawal of the instrumentation. During mobile monitoring, our crews will move the in-situ testing equipment to prevent setup. These moves will be scheduled around construction activities as to not interfere with the required measurements.

14in SQ PSC Pile (Typ.)

Tri-axial Accelermoetyer

Piezometer

Mobile CPTu Test

KEY:

Existing Tunnel


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E. Instrumentation Monitoring during Pile Installation WPC will provide weekly summary reports, showing instrumentation measurements relative to established threshold values in graphical form, to LS3P. An example of a weekly graphical instrumentation summary from WPC’s Morris Island Lighthouse project is provided in Figure 4.

Figure 5. Example Weekly Graphical Measurement Summary (from WPC Morris Island Lighthouse Instrumentation Project).

We anticipate twelve (12) weeks of pile installation, for a total of twelve (12) weekly summary reports will be issued.

E. Summary Instrumentation Monitoring Report Upon completion of pile installation and construction activities, WPC will prepare a summary instrumentation report. This report, which will be signed by a professional engineer registered in the State of South Carolina, will contain the results of all instrumentation monitoring for both the test pile program and productions piles, the results of the post-condition tunnel inspection (see Section 3.A of this proposal), a summary of the pile installations, and our conclusions regarding tunnel damage derived from this data.


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Perform Post Project Inspection of Tunnel Lining A. Post-Condition Survey of Tunnel

After completion of pile driving and other construction activities, WPC will conduct a post condition survey to close out this issue with the City. WPC intends to use the same crew to return to the tunnel and visually examine the conditions. We will return to the areas (if any) that were originally noted as being damaged and examine the segment for any new signs of distress. Like the previous visit, WPC personnel will document the tunnel using a video camera and photographs in accordance with ACI 201.1R-08 Guide for Conducting a Visual Inspection of Concrete in Service. The results of the post condition survey will be incorporated in the Summary Instrumentation Monitoring Report.

For the post condition survey of the tunnel, WPC will contract with the same firm the City used during the initial visit. WPC intends to pass through our costs ($3,000) plus access costs +10%. Based on our conversation with the firm that is likely to do the work, we anticipate a cost of $11,000 to $12,000 for the crane, manbasket and the four accompanying personnel.

Maintain Provisions for Existing Tunnel Repair or Replacement A. Development and Submittal of Tunnel Repair/Replacement Plan

WPC, in conjunction with a structural engineering firm familiar with tunnel design similar to the existing tunnel, will develop preliminary provisions for repair of the existing tunnel. These provisions will provide repair scenarios for anticipated tunnel damage (e.g. concrete spalling, lining cracking). Should actual damage be confirmed, WPC can provide detailed repair provisions. Given the complexity of tunnel replacement, this option is most likely not feasible, although this option will be evaluated.

SCHEDULE The estimated timeframes for our proposed scope of work is summarized in Table 2.


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Table 2. Estimated Task Schedules.

Davis & Floyd Condition No.

Associated WPC Task Descriptions

Time to Complete1

(days)

Time to Report2 (days)

1. Perform Pre-Project Inspection of Tunnel

Lining

A. Pre-Condition Survey of Tunnel w/Report

1 4

B. Pre-Condition Survey of Above Ground Neighboring Buildings

w/Report 5 9

2. Perform Comprehensive

Monitoring during Pile Installation

A. Development and Submittal of Tunnel Monitoring Plan

NA 10

B. Installation of Soil and Tunnel Instrumentation.

15-303

C. Test Pile Program Testing & Report TBD4 5


1 NA

E. Instrumentation Monitoring during Pile Installation (12 wks @ $1,000/wk)

TBD5 Weekly

F. Summary Instrumentation Monitoring Report

NA 14

3. Perform Post Project Inspection of Tunnel

Lining

A. Post-Condition Survey of Tunnel 1 4

4. Maintain Provisions for Tunnel Repair or

Replacement

A. Development and Submittal of Tunnel Repair/Replacement Plan

NA 20

NOTES: 1. Time for to complete fieldwork. Allow two(2) days for WPC to mobilize to site. 2. Time from completion of fieldwork or authorization to proceed to submittal of report. 3. Estimated based on conceptual instrumentation. 4. Actual length of test pile program dependent on setup of static load test reaction frame and evaluation of

Cooper Marl setup characteristics. 5. Length of production pile monitoring dependent on driven pile contractor.


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QUALIFICATIONS WPC is a geotechnical, environmental, and construction materials testing firm with over 13 years experience in the South Carolina Low Country. Our engineers routinely provide pre and post condition surveys to assess the condition of structures near construction sites, present vibration recommendations that outline construction techniques and mitigation techniques to reduce the impact of vibrations within the Charleston area, and install and monitor geotechnical and structural instrumentation. In addition to our project work, WPC engineers have published several technical papers regarding geotechnical and structural instrumentation and pile driving vibrations and are actively involved in ongoing research with the Pile Driving Contractors Association (PDCA) and the Citadel regarding this topic. WPC experience with similar scope of instrumentation ranges from residential building developments to large transportation projects. WPC monitored vibrations and existing structures during the demolition of the Grace Memorial and Silas Pearman bridges in Charleston County, SC and for the Morris Island Lighthouse during the recent installation of steel sheet piling to protect this historic structure. Both projects included pre and post condition surveys and development of instrumentation plans. WPC also installed and monitored geotechnical instrumentation for the Arthur Ravenel Jr. Bridge and installed geotechnical instrumentation for Affholder Inc. during the Cooper River Tunnel phase of the CPW Sewer Tunnel Replacement Project. WPC has extensive geotechnical data for Concord Park, having performed the geotechnical investigation for the project and having prepared the Geotechnical Data Report for the Concord Street Water Tunnel.

WPC also has extensive experience with vibration and structural monitoring of historic structures in and around the Low Country. For example, WPC conducted an extensive pre-condition survey and developed a vibration and monitoring plan for the historic Hopsewee Plantation in Georgetown County, SC. Our projects in Charleston, SC have included pre-condition surveys and ground and existing structure monitoring for such historic structures as Centenary United Methodist, Trinity United Methodist, and Church of the Holy St John. Another vibration and existing structure monitoring project of note is the Old Charleston High School Project in Charleston, SC. This project involved monitoring the existing structure and ground vibrations during pile driving within the braced brick masonry facade of the old Charleston High School during its rebuilding. Figure 2 shows pile driving operations being conducted within the braced brick façade. In addition, a pre-condition survey was conducted of the neighboring hospital and residential buildings with associated structural and ground vibration monitoring. This project


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was the 2004 Project of the Year for the Pile Driving Contractors Association (PDCA) and a 2005 award winner from the American Council of Engineering Companies (ACEC).

Figure 2. Pile driving Operations during Old Charleston High School Project. Other WPC geotechnical/structural monitoring projects include the new Woodrow Wilson Bridge across the Potomac River along I-95/I-495 (i.e. the Capitol Beltway) in Maryland and Bridge 91 over the Yadkin River for the NCDOT. Our scope of work for the Woodrow Wilson Bridge replacement project included installing instrumentation on the existing bridge abutment to detect movements, rotations, and vibrations during installation of the adjacent new bridge foundations, while the Bridge 91 over the Yadkin River included monitoring existing bridge movements during underpinning operations of a failed bridge bent foundation. WPC has an “on-call” delivery contract for deep foundation testing, to include vibration monitoring, with the South Carolina Department of Transportation (SCDOT) and has performed numerous test pile programs in the Charleston, SC area. Table 2 provides a summary of relevant WPC instrumentation/pile testing projects.


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Table 2. Relevant WPC Instrumentation Projects.

Project Location WPC Involvement

Monitoring Plan

Condition Surveys

Soil Monitoring

StructureMonitoring

Morris Island Lighthouse Charleston County,

SC X X X X

Grace Memorial and Silas Pearman Bridges Demolition

Charleston County, SC

X X X X

Hopsewee Plantation Georgetown County,

SC X X X See Note 2

Charleston Stormwater Charleston County,

SC X

Old Charleston High School Project - MUSC

Charleston, SC X X X X

Woodrow Wilson Bridge (I-95/I-495)

Prince George County, MD

X X

Bridge 91 over Yadkin River Yadkin County, NC X X X X

Mixed Use Facility Project College of Charleston

Charleston. SC X X X X

King and Queen Street Parking Garage


21 George Street Condominiums


100 Calhoun Street Office Building


Addlestone Library College of Charleston


NOTES:

1. Projects involving pile testing in bold.

2. Project has not proceeded to monitoring phase.

CLOSURE Our “Agreement for Professional Services” is attached and is incorporated as a part of this proposal. Please indicate your acceptance of our proposal by signing the attached “Agreement for Professional Services” and returning the signed copy to our office. We will execute the


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“Agreement for Professional Services” and return a copy to you for your files. We will then proceed with the performance of our services. WPC appreciates this opportunity to provide environmental services to you. Please us at (843) 884-1234 with any questions regarding this proposal or if you require any additional information. Respectfully submitted,

WPC, Inc. Joshua C. Adams Edward L. Hajduk, D.Eng. PE Instrumentation Manager Senior Engineer Donovan Ledford, P.E. Matthew Silveston, P.E. Senior Engineer Senior Engineer Attachments: Agreement for Professional Services

august 5, 2008 ls3p charleston, south carolina, 29401 wpc...

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