Attachment 6 CEU Cleveland Memo 11410 Waterfront Load Limit - MSU Clev Harbor 28 Feb 2018.pdf

Commanding Officer 1240 East Ninth Street, Room 2179 U.S. Coast Guard Cleveland, OH 44199-2060 Civil Engineering Unit Cleveland Phone: 216-902-6206 Fax: 216-902-6277

11410/18-048 28 Feb 2018

MEMORANDUM

From: S. P. Hannigan, CDR Reply to Mr. Jerry Placzek CG CEU Cleveland Attn of: 216-902-6206

To: CG MSU Cleveland Harbor Thru: CG SECTOR Buffalo

Subj: WATERFRONT LOAD LIMITS –MSU CLEVELAND HARBOR

Ref: (a) Civil Engineering Manual, COMDTINST M11000.11B

(b) My memo 11410/17-399 of 29 Dec 2017

1. Per reference (a), a structural evaluation of the MSU Cleveland Harbor waterfront bulkhead was performed on 03 September 2013 and can be found in enclosure (1).

2. The structural evaluation identified significant structural deficiencies to the Steel Sheet Pile

(SSP) RPUID – 15449. Based on the structural evaluation, MSU Cleveland Harbor waterfront bulkhead has the following waterfront load limits:

a. A working load limit of 150 pounds per square foot (psf) uniformly distributed within 20 feet of the bulkhead face. This means that stockpiling, parking and material handling is restricted to loads that fall below the 150 psf threshold. See enclosure (2) for a plan view schematic showing the area of load limitation.

b. The working load limit provides for "vehicle traffic" to continue to operate within the area of load limitation and include passenger vehicles, passenger trucks, fuel trucks, and emergency vehicles such as fire trucks. Specifically restricted from the area of load limitation are cutter bubbler compressors, heavy construction equipment to include excavators, large front end loaders, dozers, scrapers and cranes, to include those with tires, tracked crawlers, and outriggers.

3. MSU Cleveland Harbor is responsible for ensuring load limit signs are posted and clearly visible. Affected areas shall be marked off to prevent personnel injury and further degradation of the structure. Please ensure unit personnel and contactors on site take necessary precautions when operating on site.

4. To address the structural deficiencies identified in the evaluation, Shore AC&I Project

Number 5092184 ($15.9M) is listed on the Shore Facility Requirement List for execution in

FY2024. The following AFC-43 projects, as identified in reference (b), are in WAPPR status for

Subj: WATERFRONT LOAD LIMITS –MSU CLEVELAND HARBOR 11410/18-048

28 Feb 2018 consideration at future District Nine AFC-43 Regional Planned Obligation Prioritization (POP)

Boards:

a. P/N 10489955, Repair Steel Sheet Pile Bulkhead at MSU Cleveland Harbor, IGE: $253K

b. P/N 10489957, Repair Sheet Pile Wave Break at MSU Cleveland Harbor, IGE: $142K

5. Please contact the CEU Cleveland Technical Director, Mr. Jerry Placzek at (216) 902-6206 if you need any additional information.

Enclosures: (1) Structural Evaluation Report dated 3 Sept 2013

(2) Plan View Schematic

Copy: CGD NINE (dm, dpw)

CG LANTAREA (LANT-37)

CGC MORRO BAY (WTGB-106)

CGC NEAH BAY (WTGB-105)

CG BASE Cleveland

CG FDCC

CG SILC (esd)

Submitted to United States Coast Guard 1240 East Ninth Street, Rm 2179 Cleveland, OH 44119

Submitted by

AECOM

303 E Wacker Dr, Ste 14 Chicago, IL 60601 September 2013

Structural Evaluation Report

Task Order HSCG83-13-J-PCR098 (13-PCR098) A/E Services for Structural Evaluation/Environmental Assessment United States Coast Guard Marine Safety Unit (MSU) Cleveland, Ohio AECOM Project No. 60289994 mailto:Teresa.F.Dailey@uscg.mil

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Table of Contents

1 Project Understanding........................................................................................................................................................ 1-1 2 Scope of Work ..................................................................................................................................................................... 2-1 3 Summary of Moffatt & Nichol Report ................................................................................................................................ 3-1 4 AECOM Analyses ................................................................................................................................................................ 4-1

4.1 Geotechnical Analysis—Wall Configuration ................................................................................................................. 4-1

4.2 Geotechnical Analysis—Embedment and Stability ....................................................................................................... 4-1

4.3 Geotechnical Analysis—Parametric Analysis ............................................................................................................... 4-2

4.4 Structural Analysis—Steel Sheet Piling ........................................................................................................................ 4-4

4.5 Structural Analysis—Steel Waler .................................................................................................................................. 4-4

4.6 Structural Analysis—Steel Tie Rod .............................................................................................................................. 4-4

4.7 Structural Analysis—Timber Batter Pile........................................................................................................................ 4-5

4.8 Corrosion and Service Life ........................................................................................................................................... 4-5

5 Recommendations .............................................................................................................................................................. 5-1

5.1 Inspection and Monitoring ............................................................................................................................................ 5-1

5.2 Options to Increase Operational Factor of Safety ......................................................................................................... 5-3

6 Summary.............................................................................................................................................................................. 6-1

List of Appendices

Appendix A. Figure 4 Typical Section Appendix B. SPW 911 Output Appendix C. Structural Calculations

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We understand the United States Coast Guard (USCG) would like to dredge adjacent to two bulkheads identified as the North and East mooring faces, at the Marine Safety Unit (MSU) facility in Cleveland, Ohio. Current plans call for the dredging to extend to a maximum depth of 18 feet below the Low Water Datum (LWD) for Lake Erie. An alternative plan limits dredging to

15 feet below LWD. The Lake Erie LWD corresponds to elevation +569.2 (IGLD85 Datum). Therefore, -18 LWD = elevation

+551.2, and -15 LWD = elevation +554.2. Sounding maps prepared in 2011 by URS Corporation indicate the top of existing sediment adjacent to these bulkheads varies from approximately elevation +552 to slightly over elevation +556.

The North and East mooring faces and two other bulkheads at the facility were previously evaluated by Moffatt & Nichol

Engineers in January, 2001. Using historic construction drawings (circa 1934), Moffatt & Nichol produced a typical structural section for the bulkhead system which is shown as Figure 4 in Appendix A. This typical section is comprised of “u-shaped” steel sheet piling (MP 116) and a composite sheet pile and timber pile deadman connected through a waler and tie-rod. The sheet piling has a concrete cap, and the interior surface of the bulkhead quay is asphalt paved. The anchorage connection is set at elevation +572, which is 6.5 feet below the top of wall at elevation +578.5. The design length of the sheet pile (top of concrete cap to design tip) was determined to be 38 feet.

1 Project Understanding

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AECOM was authorized to perform a Site Investigation and a Structural Evaluation of the North and East mooring faces for the potential dredging. The scope of the site investigation, extents, assumptions and limitations for the structural evaluation is detailed in AECOM’s proposal dated March 4, 2013.

The Site Investigation consisted of a general site observation, two soil borings, and ultra-sonic testing of the steel sheetpile bulkhead. This site observation and ultra-sonic testing was performed on April 16 and April 17, 2013 by two AECOM technicians. The soil borings were performed by a subcontractor, Ohio Testbor, and observed by the on-site AECOM technicians. Soil samples collected from the borings were returned to the AECOM laboratory in Vernon Hills, Illinois for routine testing and classification. The site observations, soil profiles, and test data were summarized in the Site Survey Report, dated

May 17, 2013. It should be noted that no investigative test pits were performed to verify either the geometry or the condition of the bulkhead structural components, other than what is specifically described in this report.

For the Structural Analysis, AECOM performed conventional retaining wall analyses using classical free-earth methods. The existing North and East mooring faces were evaluated for the current sediment depth conditions (per the 2011 URS soundings) and for the proposed dredging to -15 LWD and -18 LWD depths. These evaluations were performed in general accordance with the guidelines and requirements of:

USACE EM1110-2-2504 Design of Sheetpile Walls, UFC 4-152-01 Design: Piers and Wharves, UFC 4-159-03 Design: Moorings

In particular, the major components of these bulkhead walls were assessed to determine the following:

Sheeting Embedment – Whether the existing sheet piles have adequate length below the mud line to maintain toe stability for the current condition and the proposed dredging, within generally accepted factors of safety.

Bending Stress – Whether the existing sheet pile section modulus is sufficient for the in-service bending moment.

Anchor Capacity and Waler/Tie Rod Stress – Whether the anchorage system has adequate capacity to resist the imposed pullout load. The effectiveness of the transfer of loading from the wall to the anchor system through the waler was also evaluated.

Corrosion and Service Life – The sheet pile and anchorage components were assessed to estimate the potential remaining service life.

AECOM utilized the soil profiles and strength parameters developed during the Subsurface Investigation (soil borings and laboratory testing). Geometry and major component sizing were based on historic design drawings provided by USCG. The

2001 Moffatt & Nichol report was used to evaluate section loss and corrosion. As directed by USCG, no investigative test pits were excavated to check the condition of the walers, tie-rods, or anchorage system. AECOM assumed these elements are fully functional.

Analyses were based on a static water environment assuming the bulkheads are effectively sheltered. No hydrodynamic forces associated with wave loading or prop wash were developed or considered in the analyses. Ice loading was not part of this analysis.

2 Scope of Work

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The North and East mooring faces and two other bulkheads at the facility were evaluated by Moffatt & Nichol Engineers in

January, 2001. We understand Moffatt & Nichol did not have any soil data from borings available at the time of their analysis.

Moffatt & Nichol therefore assumed the soil profile consists of loose to medium dense fill overlying natural dense sand. (It should be noted the soil borings performed in April 2013 as part of AECOM’s site investigation encountered soil conditions different than this assumption – see section 4.2 of this report). For their structural analysis, Moffatt & Nichol assumed: the steel sheet piles are PZ22; the steel waler is (2) C 15 X 33.9 channels; the tie rods are 2 ¾” diameter, spaced 13’-4” on center;

and the tension in each tie rod is resisted by a 12” diameter timber batter pile.

Moffatt & Nichol performed geotechnical and structural analyses assuming a dredge depth of -13.7 LWD (the existing mudline at the time of their investigation), as well as a dredge depth of -16.7 LWD (the design dredge depth, based on the original drawings). They drew the following conclusions:

The embedment of the sheet piling below the dredge line was adequate for both dredge depths.

The sheet piling is overstressed in bending for both dredge depths.

The waler is adequate for both dredge depths.

The anchor rods are adequate for both dredge depths.

The North and East mooring faces and two other bulkheads at the facility were also inspected for evidence of corrosion by

Moffatt & Nichol in November, 2000. Ultrasonic testing found section loss in the steel sheet piling, just below the waterline, of between 32% and 68%. Numerous small holes were observed. They estimated the remaining service life of the bulkheads to be approximately 5 to 7 years, at that time.

3 Summary of Moffatt & Nichol Report

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4.1 Geotechnical Analysis—Wall Configuration

The USCG Marine Safety Unit bulkhead quay was reportedly constructed in 1934. The quay itself is composed of four bulkheads with a perimeter of approximately 678 feet. However, only Bulkheads 2 and 3, the East and North Mooring faces, are addressed in this scope of work.

The typical retaining wall section is comprised of steel sheet pile and a composite sheet pile and timber pile deadman connected through a waler and tie-rod. Based on historic drawings and measurements taken by Moffatt & Nichol Engineers, the sheet pile was determined to be a “U-shaped” or Larssen section conforming to an MP116 profile likely produced by US

Steel or Bethlehem. U-sections are conventionally driven in alternating pairs to produce a wall alignment with a “belly-in / belly-out” pattern that is visually similar to that produced by a standard “Z-shaped” sheet pile. The primary difference between the two systems is the location of the interlocks in the finished wall (see Figure 1, following).

a. U-Shaped or Larssen Section b. Z-Shaped Section

FIGURE 1: Typical sheet pile sections in use

The interlocks for U-shaped sections are located at the neutral axis (y-y in Figure 1a) of the completed wall. To prevent slippage in bending applications, the interlocks of U-shaped walls are conventionally welded. Conversely, for a Z-shaped section, the interlocks are located at extremes of the wall depth, this wall depth is indicated as “h” (Figure 1b).

The sheet pile at the bulkhead quay is provided with a concrete cap and the interior surface is asphalt paved. The anchorage connection is set at elevation +572 (+2.8 LWD), which is 6.5 feet below the top of wall at elevation +578.5 (+9.3 LWD). The design length of the sheet pile from top of concrete cap to design tip, was indicated to be 38 feet.

4.2 Geotechnical Analysis—Embedment and Stability

The retaining walls were analyzed for stability using classical free-earth methods. In this procedure, a static analysis is performed assuming the moment at the anchorage elevation is equal to zero. The desired factor of safety against failure is applied to the mobilized passive resistance, and the length of sheet pile penetration below the excavation, mudline, or dredge line required to balance the driving and resisting forces is determined.

The stability analyses were performed using the commercial software SPW 911 produced by Pile Buck, Inc. Separate analyses were performed for each mooring face using the soil profiles developed from the April 2013 soil borings. The soil profile within the depth of exploration consisted of approximately 20 to 25 feet of man-placed soil (fill) overlying apparent lake sand and compressible lacustrine clay (glacial drift). The tip of the assumed 38-foot long sheet pile is located in the soft clay.

For comparison, analyses were also performed using the soil profile assumed by Moffatt & Nichol consisting of loose to medium dense fill overlying natural dense sand.

4 AECOM Analyses

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A uniform surcharge of 250 psf was applied behind the retaining wall to account for variable material stockpiles, light structure loads, vehicle traffic (moving and static) that may exist along the alignments, and light support reactions as may be imposed by attached fendering systems, small mooring cleats, or lightly loaded davit cranes. The surcharge also helps to generalize the analyses and account for minor variability in the stratigraphy, the strength in the backfill materials, and small changes in top of wall elevation between the widely spaced boring locations.

The walls were analyzed using the low water datum (elevation +569.2 corresponds to +0.0 LWD) for Lake Erie. It was assumed the existing off-shore breakwater would substantially reduce wave loading associated with the lake. Consequently no hydrodynamic pressures were applied to the bulkhead walls in this analysis. However, a 2-foot differential head was applied to account for the retained water indicated by the observations made in the April 2013 soil borings, and the potential wake pressures associated with moorings.

The walls were not analyzed for mooring line pulls, ice pressure, vessel impact, seismic or any other imposed loads.

The results of the retaining wall analyses for dredging to both -15 LWD and -18 LWD are summarized in the table below. The table also includes results of analyses performed to estimate required embedment depths to obtain the generally accepted factor of safety of 1.5 for a dredge depth of -18 LWD. Copies of the SPW 911 output are included in Appendix B.

TABLE 1: Summary of Bulkhead Retaining Wall Analyses using SPW 911

Location Dredge

Elevation

Pile Tip

Elevation

Maximum

Moment

Horizontal

Anchor Load

Factor of Safety

Moffatt & Nichol

(Assumed Granular Profile)

+554.2

(-15 LWD)

+540.5

(-28.7 LWD)

50.2 kip-ft 9.23 kip FS > 1.5

+551.2

(-18 LWD)

+540.5

(-28.7 LWD)

59.7 kip-ft 9.92 kip 1.1 < FS < 1.2

North Mooring Face

(Boring B-1)

+554.2

(-15 LWD)

+540.5

(-28.7 LWD)

34.3 kip-ft 7.54 kip 1 < FS < 1.1

+551.2

(-18 LWD)

+540.5

(-28.7 LWD)

- - 1 < FS

+551.2

(-18 LWD)

+518.0

(-51.2 LWD)

96.6 kip-ft 11.78 kip FS > 1.5

East Mooring Face

(Boring B-2)

+554.2

(-15 LWD)

+540.5

(-28.7 LWD)

39.4 kip-ft 7.98 kip 1 < FS < 1.1

+551.2

(-18 LWD)

+540.5

(-28.7 LWD)

- - (0.7 Est) 1 < FS

+551.2

(-18 LWD)

+519.5

(-49.7 LWD)

71.3 kip-ft 10.0 kip FS > 1.5

Based on these analyses, it appears the walls would be marginally stable (1 < FS < 1.2) for dredging to elevation -15 LWD. If dredging is extended to -18 LWD, the walls would likely experience toe failure due to inadequate sheet pile penetration. To provide a factor of safety of 1.5 as recommended by the US Army Corps of Engineers (EM 1110-2-2504) at a dredge elevation of -18 LWD, the sheet pile would need to be approximately 20-25 feet longer.

4.3 Geotechnical Analysis—Parametric Analysis

To account for potentially non-representative sampling results, and the limited amount of subsurface data obtained from the two soil borings completed in April 2013, parametric analyses were performed to assess the sensitivity of the wall system to the strengths of the soils below the dredge line. In these analyses, the design strengths of the clay crust and the soft clay were iterated to provide a specific factor of safety for the assumed 38-foot long sheet pile. The strengths of the retained fill soils and the general profile stratigraphy were held constant in the parametric analyses.

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The results of the analyses were grouped by design dredge depth and are plotted in Figure 2 below:

FIGURE 2: Parametric analysis results for North and East Mooring Faces at design dredge depths

For dredging to -15 LWD, the toe resistance is dominated by the strength of the clay crust, and because its thickness is consistent between the design profiles, the spread in the analysis results is relatively small. However, the clay crust was encountered at a slightly higher elevation along the North Mooring Face. If dredging were extended to -18 LWD, it will reduce the available thickness of this material in the resistance profile relative to the East Mooring Face. Therefore, a larger strength increase is required for the soils on the North Mooring Face to produce the same factor of safety, which is indicated by the

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K:\PROJECTS\60289994_USCG MSU\500_Submittals\5.03 Final Structural Evaluation Report\Structural_Evaluation_Report_9-03-13.docx September 2013 greater spread in the analysis results. The linear regression lines can be assumed to represent an average condition for the two bulkheads which takes into consideration the lateral changes in the composition of the retained fill and localized variations in the transitions between soil types within the footprint of the quay structure.

As can be seen from the plots, the strengths of the lakebed clays (i.e., the clay crust and soft clay) would need to be slightly more than 50% higher than was indicated by the field and laboratory testing to achieve a factor of safety of 1.5 with a dredge depth of -15 LWD. Similarly, for a dredge to -18 LWD, the clay shear strengths would need to increase by 85% to satisfy

USACE design guidelines.

Owing to scale factors, disturbance, and changes in the stress state, the in-situ strength of a natural clay deposit will, in general, be higher than that estimated from pocket penetrometer and unconfined compressive strength tests performed on recovered samples. A variety of empirical correction factors may be applied, but in most cases the net increase in estimated strength varies from about 15 to 35% depending primarily on quality and quantity of sampling and testing. Allowing for an increase of 25% in the design strengths, it can be seen that the walls would have an operational factor of safety between 1.2 and 1.3 if the dredging is completed to -15 LWD. While well below the standard USACE guidelines for design of waterfront structures, the analysis indicates the bulkhead walls would be effectively stable at this dredge depth. If the dredge is extended to -18 LWD, the factor of safety would decrease to a value of approximately 1.1, which would be considered marginal for safe operation.

4.4 Structural Analysis—Steel Sheet Piling

The MP116 steel sheet piling was first analyzed for the induced bending moment, assuming a dredge depth of -15 LWD. This bending moment was calculated as part of the geotechnical analysis described in Section 4.2 above. Structural calculations are contained in Appendix C of this report.

The section properties of the sheet pile wall were determined assuming full composite action between the individual sheet piles (i.e., no slippage in the interlocks). Interestingly, because most of the area of the sheet piles is near the neutral axis of the composite wall, there is little difference between the section properties of the composite wall and those of the individual sheet piles.

The sheet piling was found to be 77% overstressed for a dredge depth of -15 LWD. While it is commonly accepted that the free earth method of retaining wall analysis overestimates bending moment, it is unlikely this sheet piling can be justified for a dredge depth of -18 LWD.

4.5 Structural Analysis—Steel Waler

The waler was assumed to consist of (2) C 15 X 33.9 steel channels, back to back, with a gap between the channels to accommodate the tie rods. The waler was analyzed for the induced lateral force, for a dredge depth of -15 LWD. This lateral force was calculated as part of the geotechnical analysis described in Section 4.2 above. Structural calculations are contained in Appendix C of this report.

The waler was found to be acceptable for the induced lateral force.

4.6 Structural Analysis—Steel Tie Rod

The tie rods were assumed to be 2 ¾” diameter, unthreaded steel rods, spaced 13’-4” on center. The typical tie rod was analyzed for the induced tension force, for a dredge depth of -15 LWD. This tension force was based on the waler force mentioned in Section 4.5 above. Structural calculations are contained in Appendix C of this report.

The allowable stress in tie rods is typically limited to 40% of the yield stress. This conservative assumption accounts for the fact that tie rod force is generally higher than the force calculated using the free earth method of retaining wall analysis.

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The typical tie rod was found to be 24% overstressed. While limiting allowable stress to 40% of yield stress is conservative, and may indicate the tie rods are acceptable for a dredge depth of -15 LWD, it is unlikely they can be justified for a dredge depth of -18 LWD.

4.7 Structural Analysis—Timber Batter Pile

The two species of timber generally used for the manufacture of timber piles in North America are Douglas Fir and Southern

Yellow Pine. Unlike pipe or steel section piles, timber piles have a natural taper. The tip of the pile represents the smallest circumference and the lowest strength section of a pile. To achieve a desired structural capacity, piles are typically selected based on the tip diameter. The corresponding butt dimension becomes a function of the species and the desired pile length.

For design it is common to use a critical diameter, which represents the minimum average dimension which would be expected along the length of the pile. In general, the critical diameter is assumed to be 1-2 inches larger than the tip diameter.

The historic drawings indicate the timber piles had a required minimum [butt] diameter of 12 inches and they were driven on

1H:1V batter. Given their age they would likely be rated as Class B per ASTM D 25, although the standard itself was not adopted until 1937. Tabulated piling charts for Douglas Fir and Southern Pine indicate the tip diameter for a 40 to 45-foot pile length would be approximately 7 to 9 inches. The rated capacity for these piles based on dimensions would be somewhere between 40 and 80 kips depending on the actual tip diameter they were able to source. Old-growth timber tended to have a lesser taper than the modern forest product upon which the tables are based. Using a conservative maximum compression stress of 900 to 1,000 psi for the unknown species, and assuming a similar-to-modern taper profile with an average tip of 8 inches, the design structural capacity of the timber batter piles was estimated at about 50 kips.

Historically, nearly all timber piles were installed using the Engineering News Formula, or a variant thereof. The piles were driven to a penetration resistance which is determined from an empirical function of the hammer energy and the desired capacity. For a capacity of 50 to 60 kips, we would estimate the piles were installed to a resistance of about 25 to 30 blows per foot (2 to 3 blows per inch) depending upon the actual hammer size used. For foundation piling, a driving resistance of 7 to 10 blows per inch was not uncommon, so the range of 2 to 5 blows per inch would seem to be about right for this type of application.

Assuming a dredge depth to -15 LWD, and resolving the entire horizontal reaction force into an axial compression on the batter piles, the overload is estimated to be 198%.

Research performed by the United States Federal Highway Administration (FHWA) has concluded that timber foundation piles submerged in fresh ground water will last indefinitely. Fully embedded, treated, and concrete capped foundation piles which extend partially above the groundwater will last 100 years or longer. Treated exposed piles, such as marine piles, can be expected to last about 75 years in northern areas and about 40 years in southern areas of the United States. Given the approximate timeframe of the construction, we would expect the timber piles at this site were creosoted, or otherwise treated.

Creosoting as a preservation system for timber piles dates from the late 1800’s. It was the most prevalent system until it was supplanted in the late 20th Century by Copper Chromated Arsenate (CCA) and Ammoniacal Zinc Arsenate (ACZA).

Decay and rot will be accelerated in the presence of oxygen. In most anchorage applications, the connection is located above the static groundwater level. Cyclic rises and falls in the groundwater will also tend to decrease service life of the anchorage system through failure of the tie rod to pile connection.

4.8 Corrosion and Service Life

As part of the April 2013 site investigation, AECOM performed ultrasonic testing at numerous locations on the bulkheads to determine the thickness of the steel sheet pile. AECOM accessed the face of the sheet pile using a small boat.

Measurements were restricted to locations above the waterline. No dive survey was performed as part of this scope.

Ultrasonic thickness gaging is a widely used nondestructive test technique for measuring the thickness of a material from one side. In general, ultrasonic thickness gages work by very precisely measuring how long it takes for a sound pulse generated

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K:\PROJECTS\60289994_USCG MSU\500_Submittals\5.03 Final Structural Evaluation Report\Structural_Evaluation_Report_9-03-13.docx September 2013 by a transducer to travel through the test piece. Because sound waves reflect from boundaries between dissimilar materials, this measurement is normally made from one side in a "pulse/echo" mode, where the gage measures the round trip transit time of a pulse that reflects off the far side or back wall of the test piece.

Many factors affect measurement accuracy in a given application, including proper instrument calibration, uniformity of material sound velocity, sound attenuation and scattering, surface roughness, curvature, poor sound coupling, and backwall non-parallelism. With proper calibration, measurements can usually be made to an accuracy of +/- 0.001" or 0.01 mm, and in some cases accuracy can approach 0.0001" or 0.001 mm. Accuracy in a given application can best be determined through the use of reference standards of precisely known thickness. For this application, reference measurements were made at accessible existing penetrations where the full depth of the sheet pile was exposed. Although the sheet pile at these locations was slightly distorted, it did provide a reasonable check on the measurements.

The following table summarizes the results of the tests performed in April 2013 by AECOM. All AECOM tests were performed above the water line. Generally the thickness was measured at or about 0.400 inches.

TABLE 2: Sheet Pile Thickness Measurements

East Mooring Face North Mooring Face

Test Thickness (in) Notes Test Thickness (in) Notes

1 South End 0.402 7 East End 0.370

0.398 8

0.389

3 0.409 9 0.392 Ref 0.404

4 0.425 Rough Surface 10 0.438 Rough Surface

5 0.433 Scaling, Rough 11 0.412

6 North End 0.406 Ref 0.409 12 0.403

13 West End 0.402

A new MP116 steel sheet pile had 3/8” thick webs and a 3/8” thick flange. The measurements in Table 2 indicate the loss of section due to corrosion, above the waterline, has been minimal.

However, the anticipated service life for a steel bulkhead wall is 50 years. These bulkhead walls, constructed in 1934, are almost 80 years old. We believe the bulkhead walls have outlived their useful service life.

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5.1 Inspection and Monitoring

It should be recognized the construction of this bulkhead wall predates the modern development of geotechnical engineering, and the publication and widespread dissemination of the USACE and NAVFAC design manuals and recommendations.

Consequently, it can be expected the wall system was designed using analysis methods and material strength limitations that are not consistent with current practice, and it may not be possible to satisfy modern design requirements with the existing structure. Many such older structures are currently functional and performing adequately at factors of safety similar to, or lesser than, those described above.

While it would not normally be recommended for routine design, it is our opinion the risks associated with allowing the bulkheads to remain in service at the indicated factors of safety can be reduced to a manageable level if inspection and monitoring programs are instituted as part of the maintenance and operations plan for the structure. The intensity of the monitoring program and the frequency of the inspections would need to be developed taking into consideration the factor of safety environment in which the wall system is expected to operate (i.e., the acceptable risk level), and the project specific definition of failure. Typical failure limits for quay structures may include serviceability falling below a level that permits mooring of specific vessels, a structural load rating dropping below an operational threshold, or in extreme cases failure may allow for partial collapse provided there is no discharge of retained material.

Given the age and condition of the structure, establishment of an inspection and monitoring program would be strongly recommended regardless of the dredging option chosen. The deterioration of waterfront structures is generally progressive, but is rarely linear. As a minimum the program should provide for evaluation of lateral and vertical movement of the bulkhead walls over time, and an assessment of corrosion and other readily visible signs of distress of the structural elements. The site walkover should also include a general assessment of pavements and other site features to identify areas of soil loss, excessive ground movement, and any damage to supported or adjacent structures that could be associated with the performance of the quay.

Survey points established at regular intervals along the top of the wall would be useful for determining general movements, but they cannot provide information regarding the progressive change in the wall deflection profile. Moreover, their readings are subject to environmental conditions and accuracy may not be sufficient to capture the small differential movements of the wall over time. To supplement survey points, it is recommended that inclinometers be installed behind the bulkhead walls.

Inclinometers consist of aluminum or plastic casings drilled vertically into a stable (non-moving) stratum which is located below the level of interest. The casing is provided with tracking grooves, or rails, which enable the deflection measurements to be oriented parallel to, and at right angles to, the axis of the retaining wall face. The inclinometer probe contains bi-axial servo-accelerometers which detect the change in tilt from absolute vertical as the probe is lowered and withdrawn from the casing.

Following establishment of the baseline, each set of readings thereafter provides data on how the ground (effectively the wall) is moving when the user plots the newer movement curves against the initial curves.

The following nominal scope could be used as a guideline to establish a monitoring and inspection program for the bulkhead quay structure:

5 Recommendations

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TABLE 3: Nominal Inspection and Monitoring Program

Operational Criteria

Survey Points Inclinometers Structural Inspection

Additional Considerations

FS > 1.5

Establish local benchmark and set points at 50-ft intervals along top of wall. Read on annual basis.

None Required

Perform walkover condition survey every 2 years, supplement with annual site visit

Increase frequency of readings if sudden wall movements are observed, or if corrosion or deterioration appears to be accelerating.

1.3 < FS < 1.5

As above increase frequency of readings to bi-annual

Install 2 inclinometers (one each mooring face) and read bi-annually

Perform walkover condition survey every 2 years, supplement with annual site visit

Increase frequency if sudden wall movements are observed. Verify that total movements have not exceeded tolerable thresholds.

1.15 < FS < 1.3

As above increase frequency of readings to quarterly

Install 4 inclinometers (two each mooring face) and read quarterly

Perform annual walkover condition survey. Include inspection by boat of anchorage.

Increase frequency of inclinometer readings if sustained movements are observed or if movements appear to be accelerating. Intervention procedures for corrective action should be established.

1.15 < FS

As above increase frequency of readings to every other month

Install 5 inclinometers (two each mooring face and one at corner) and read monthly

Perform walkover condition survey every 6 months.

Supplement with annual boat inspection and a dive survey every 2 years.

Monitoring should be weighted heavily toward evaluating rates of movement.

Equipment and materials required for intervention should be readily accessible or stockpiled on-site. Surcharge loading immediately behind the walls should be prohibited or closely controlled.

The details of the actual monitoring and inspection program would need to be determined in consultation with the USCG. In general, monitoring program details should include:

The type of instrumentation, Installation requirements and locations where applicable, Schedule of readings and reporting, Threshold and maximum limit criteria for vertical and horizontal movement, Contact information for the USCG and responsible engineer, Notification and construction procedures should the threshold criteria be exceeded.

The threshold values should be based on performance predictions. Obviously, modern structures can resist slightly more movements and/or higher ranges of vibrations, fragile structures considerably less. A typical program would define a maximum allowable value (generally consistent with maximum values defined by regulatory agencies), and at least two thresholds below the maximum that trigger specific actions.

For example, for a retaining wall which is movement sensitive, the maximum top deflection might be set at 1 inch total horizontal movement. Preferably the upper limit is based on performance prediction, but for simple applications it may be defined using an acceptable tolerance range for the retention system components, or the estimated tolerance of an adjacent structure. The first threshold could be 0.5 inches which would trigger increased frequency of survey or inclinometer readings.

The second threshold may then be 0.75 inches, at which time operational activities in the area are temporarily halted. The

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K:\PROJECTS\60289994_USCG MSU\500_Submittals\5.03 Final Structural Evaluation Report\Structural_Evaluation_Report_9-03-13.docx September 2013 assumptions used in the design analysis can then be re-evaluated, and the operations practices assessed to determine the fundamental cause of the un-anticipated movements. Procedure modifications could then be implemented to allow operations to continue, or additional investigation and analysis could be performed to develop repair or strengthening options. In extreme cases where progressive failure is a concern intervention by removal of surcharges and excavation of backfill could be considered to relieve loading on the walls.

5.2 Options to Increase Operational Factor of Safety

Although steel sheet piling immersed in fresh water and exposed to non-aggressive soils has been observed anecdotally in the literature to last virtually indefinitely, the typical design life span is limited in practice to a period of 50 or 75 years. Having been installed in 1934, the steel sheet piling used in the construction of the bulkhead walls would generally be considered to be beyond its practical service life. We understand, however, that at the time of the writing of this report, complete replacement and reconstruction of the bulkhead structure is not being considered.

Several options exist to potentially extend the service life of the existing structure and allow completion of the desired dredging to a variable extent depending upon the measures implemented. While it may not be economically practical to modify the walls to achieve modern design requirements, the options would help to improve the factor of safety at which the structure operates.

These options are summarized in Table 4, and further described in the paragraphs following the table. The options can be characterized as either Structure Modifications, or Operations Modifications.

TABLE 4: Strengthening and Design Options

Solution Description Advantages Limitations Cost Range

S T

R U

C T

U R

E M

O D

IF

IC

A T

IO

N

Supplemental Toe Restraint

Install soldier piles outboard of existing wall to prevent toe rotation failure.

Efficient and reliable

Relatively quick to install

Can be done from existing structure

Requires access to face of sheet pile

Potential interference with moorings

May preclude use of some fendering systems

Moderate to High

Secondary Anchorage

Install second level of anchorage below waterline (approximately 10’ below existing at -7 LWD) to reduce required embedment

Could be performed from inside the structure

Would partially relieve the load on the existing anchorage

Opportunity to strengthen existing anchorage and connections

Connection must be made below waterline

Supplemental deadman would be required

Efficiency of deadman limited by geometry

High

Backfill Replacement

Excavate interior fill within approximately 20’ of the walls to the waterline (top of tiebacks). Replace with lightweight fill, foam concrete or similar.

May increase stability by 15 to 30% depending upon design dredge

Highly cost-effective for relative increase in stability

Can be performed in stages to limit cost exposure for a

Will generate spoil which may incur disposal cost

Will require disruption of treatment area

Some systems may have limitations on surcharge loading or traffic restrictions

Moderate

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Does not require specialty contractor for majority of work

Primarily earthworks

O P

E R

A T

IO

N

S M

O D

IF

IC

A T

IO

N

Design Dredge to -15 LWD

Limit maximum dredge to no deeper than -15 LWD at the walls

No modifications to existing wall required

Operational factor of safety1.2 < FS < 1.3

Does not achieve desired maximum dredge depth

Structural wall elements may be overstressed

N/A

Smart Dredge Profile

Extend dredge to -18 LWD in navigation channel and below ship keel. Reduce dredge to -15 LWD within 15’ of wall face

Satisfies maximum design dredge intent while reducing impact on the existing structure

Profile which benefits stability may not be consistent with ship requirements

Additional mooring dolphins or lane markers may be required

Profile would need to be maintained from future dredging and erosion

Low

Impose Usage Restrictions on Deck

Restrict stockpiling, parking, material handling, etc. which results in surcharge loading within the active zone of the bulkhead walls

Could improve operational factor of safety by 10 to 15%

Would likely not be sufficient to allow dredge to -18 LWD

May interfere with practical and efficient operations for the quay

May require relocation of waterside facilities

Low

Structure Modifications

For the general case of a waterfront retaining wall subject to a toe rotation, the most common strengthening option is the installation of toe, or “pin” piles to provide supplemental lateral restraint. The piles are driven or drilled-in at regular intervals and extended into a stable stratum below the depth of the sheet pile. Depending on the application, the piles may be cut-off at some level below the waterline, or they may secured to the wall face through welded brackets. Either small diameter (8-inch or less) pipe sections, or compact wide-flange (HP 8) sections, may be used. For Z-shaped profiles it is preferable to locate the piles at belly-in locations to reduce the protrusion from the wall and to maintain the restraint within the neutral plane of the sheet pile.

At this site however, the use of toe piles is likely impractical. Access cannot be gained to the face of the wall without extensive removal of fendering and mooring systems. The concrete cap and utility hangers also create an overhang which could interfere with driving or drilling operations. The construction could be performed from a barge using a small reach-in capable micro-pile rig to mitigate some of the conflicts, however, the cost would increase substantially, and clearance of the wall face at the installation line would still be required.

The installation of a second level of anchorage such as a grouted tieback or passive soil anchor will reduce the demand for lateral resistance in the embedded portion of the wall, but it requires unrestricted access to the face of the wall for installation of walers or anchorage head assemblies. For waterfront structures, drilled-in tiebacks are conventionally utilized as replacement anchorage for failed tie rod and deadman systems, but the difficulty and cost associated with underwater

(TABLE 4 continued)

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K:\PROJECTS\60289994_USCG MSU\500_Submittals\5.03 Final Structural Evaluation Report\Structural_Evaluation_Report_9-03-13.docx September 2013 construction often precludes their use as a supplemental lower tier system. Simply replacing a single-tier anchorage with a more robust system will not reduce the required embedment.

At this site, outboard (waterside) installation is likely impractical. To be effective and reduce the unbraced length of sheeting, the second level of anchors would need to be installed below the existing tie rod system which is located within a few feet of the waterline. Although the tiebacks could be drilled from a barge, the sheet pile penetrations, waler and anchor head connections, and pre-stressing would all require the use of construction divers.

As an alternative, the secondary anchorage could be constructed using an excavation inside the quay structure. Large diameter bored piles would be installed to act as deadmen, and a new tie rod and waler system would be used to transfer loads from the sheetpile bulkhead. However, the connection to the wall would require a substantial excavation, and some pumping or dewatering would likely be required to maintain a stable working subgrade. The excavation would also need to maintain and work around the existing anchorage which would be exposed in the excavation. However, once exposed, this would present an opportunity to strengthen the existing anchorage as part of these works.

Of the Structural Modification items listed, the backfill excavation and replacement option offers perhaps the best performance benefit return to investment cost, and is the most feasible. Rather than using brute-force structural measures to increase resistance, this system reduces the driving load on the existing embedded portion of the wall. For a simple wall retaining granular fill above the water table, replacing the backfill in the active zone with a lightweight fill or foam concrete could reduce the active earth pressure by 50% to as much as 65% if it provided for the full height of the wall. The reduction in required embedment is further dependent upon geometry and the anchorage provided, but 25 to 60% could reasonably be expected.

For the bulkhead quay, the reduction in required embedment could be balanced by increasing the allowable dredge depth to maintain an acceptable operational factor of safety. However, for practical construction and cost reasons the excavation would not be expected to extend lower than the existing tie rod and deadman system. For the wall profiles used in the analyses, we would estimate that the increase in the factor of safety would be between 15 and 30% depending upon the depth of the final dredge at the wall. The excavation would need to extend approximately 20 to 30 feet behind the face of the wall, or approximately the length of a typical parking space plus a portion of the drive lane. The excavation would then extend down at

1H:1V slope to the top of the tie rods which are 6 to 7 feet below existing grade. Preferably the backfill replacement would be completed in advance of the dredging. The works could be completed in stages to allow the quay to remain active, and, if desired, the backfill replacement could be performed during successive construction seasons or fiscal sessions to limit exposure and inconvenience.

Operations Modifications

In lieu of adapting the structure to desired use, the operations can be modified to suit the existing structure. Based on our analyses, it appears that setting a default maxim dredge at -15 LWD would allow the existing structure to remain in service virtually as is. Moffatt & Nichol indicated the lakebed ranged from about -4 to -14 LWD at the bulkhead walls. The hydrographic plan prepared by URS indicates the existing lakebed is no higher than about -10 LWD, and it may be as low as -

18 LWD on the north side of the East Mooring Face. Assuming a uniform dredge to -15 LWD, the operational factor of safety in most areas would decrease slightly from the existing, but the structure…