6. PO-133 Geotechnical Report 4.11.2014.pdf

Geotechnical Engineering Services LaBranche Central Marsh Creation Project

(PO-133)

St. Charles Parish, Louisiana for US Department of Agriculture Natural Resources Conservation Service

April 11, 2014

Earth Science + Technology

Geotechnical Engineering Services

LaBranche Central Marsh Creation Project (PO-133) St. Charles Parish, Louisiana for US Department of Agriculture Natural Resources Conservation Service

April 11, 2014

11955 Lakeland Park Boulevard, Suite 100 Baton Rouge, Louisiana 70809 225.293.2460

Table of Contents

INTRODUCTION

PROJECT UNDERSTANDING

PURPOSE AND SCOPE OF SERVICES

EXISTING INFORMATION

Pipelines 2013 Survey Data LaBranche East Marsh Creation Project (PO-75)

FIELD EXPLORATION

LABORATORY TESTING

Marsh Area Lake Borrow Area

SITE CONDITIONS

Project Location Surface Conditions Subsurface Conditions

Subsurface Marsh Stratigraphy Borrow Area Stratigraphy

CONCLUSIONS AND RECOMMENDATIONS

General Pilot Test Study Marsh Creation

Settlement Hydraulic Fill Containment

Cut-to-fill Ratios

CONSTRUCTION CONSIDERATIONS

LIMITATIONS

LIST OF FIGURES

Figure 1. Vicinity Map Figure 2. Site Location Plan with Soil Borings Figures 3A through 3B. Subsurface Profile Sections Figure 4. USACE Subsurface Profile Figure 5. Assumed Containment Dike Geometry

April 11, 2014 | Page i File No. 10883-018-01

APPENDICES

Appendix A. Logs of Borings Figure A-1 - Key to Exploration Logs Figures A-2 through A-15 - Logs of Borings Appendix B. Laboratory Testing Consolidation Test Results Summary Tables of Laboratory Data Appendix C. Design Profiles Figures C-1 through C-14 - Design Soil Parameters.

Appendix D. Settlement Analyses for Marsh Fill and Foundation Soils Figures D-1 through D-14 - Marsh Fill and Foundation Soils Time Rate of Settlement Settlement Calculations for Marsh Fill and Foundation Soils Appendix E. Slope Stability and Bearing Analyses for Containment Dikes

Figures E-1 through E-14 - Earthen Containment Dike Slope Stability Evaluations Slope Stability Calculations Bearing Capacity Calculations Apprendix F. Containment Dike Settlement Figures F-1 through F-14 – Earthen Containment Dike Elevation vs. Time Containment Dike Settlement Calculations Appendix G. Report Limitations and Guidelines for Use

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LABRANCHE CENTRAL MARSH CREATION PROJECT (PO-133) St. Charles Parish, Louisiana

INTRODUCTION

This report presents the results of GeoEngineers, Inc.’s (GeoEngineers) geotechnical engineering services for the LaBranche Central Marsh Creation Project (PO-133) located in St. Charles Parish, Louisiana. Our services have been completed under the United States Department of Agriculture - Natural Resources Conservation Service (NRCS) contract AG-7217-C-10-003, task order AG-7217- D-10-0095, dated September 26, 2013. The LaBranche Central Marsh Creation Project is located in an area of open water near Lake Pontchartrain south of Interstate 10 approximately 2 miles east of where the Bonnet Carré Spillway discharges into the lake, as shown in the Vicinity Map, Figure 1.

The open marsh area will be filled with soil dredged from Lake Pontchartrain near where the spillway discharges into the lake, as also shown in Figure 1. Relevant site features are shown in Figure 2.

PROJECT UNDERSTANDING

Our understanding of the project is based on the June 4, 2013, NRCS Proposal No. 14 scope of services, subsequent communications, and a June 27, 2013 site visit with the NRCS.

We understand that this project will involve creation of approximately 764 acres of interior marsh and nourishment of approximately 140 acres of existing marsh using a hydraulic dredge to excavate bottom material from Lake Pontchartrain and pump it to the planned marsh creation area.

We understand that the target marsh elevation for this project is +1 foot (EL. +1 ft.). The target year could range between 3 and 20 years and will be decided subsequent to this study. All elevations in this report and its appendices are referenced to the North American Vertical Datum of

1988 (NAVD 88).

PURPOSE AND SCOPE OF SERVICES

The purpose of our services was to complete a geotechnical investigation and analysis to develop recommendations for design and construction of the proposed marsh creation. Our specific scope of services included the following:

1. Visited the site to observe field conditions and better understand the project conditions.

2. Contacted Louisiana “One-Call” to notify them of our intent to perform soil borings at this site and to clear the boring locations of potential underground utilities.

3. Performed a field investigation that included:

a. Fourteen (14) undisturbed soil borings; of which 13 soil borings were each 30 feet in depth, and one soil boring was 80 feet in depth with air boat-mounted drill rig, and

b. Borehole vane shear tests at 14 boring locations in the marsh.

4. Performed laboratory testing on select undisturbed specimens. Selected samples were lab classified and subjected to strength, unit weight, moisture content, Atterberg limit, sieve, hydrometer, organic content, fiber content, specific gravity and consolidation testing.

5. Evaluated subsurface data and identified appropriate design profiles representing different sections along the project alignment.

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6. Completed the following evaluations for each design profile:

a. Earthen Containment Dikes:

i. Stability analyses to determine stable dike side slopes and minimum berm width between the dike and borrow excavation

b. Marsh Creation:

i. Settlement analyses to evaluate the initial marsh elevation required to meet a target elevation of EL. +1.0 ft. between three (3) and 20 years, and

ii. Marsh settlement versus time over a 20-year period for a range of initial fill elevations from EL. +1.5 ft. to EL. +4.0 ft.

7. Provided general construction recommendations.

8. Prepared a report of findings, including recommended earthen containment dike geometry, estimated marsh settlement and fill to cut ratios.

EXISTING INFORMATION

Pipelines

Pipeline locations were provided by the NRCS. The approximate locations of known pipelines based on the information provided to GeoEngineers are shown in Figure 2.

2013 Survey Data

The NRCS contracted with T. Baker Smith, Inc. (TBS) to perform surveying for this project. TBS marked the soil boring locations and surveyed the mudline elevation at each soil boring location.

Mudline elevation is shown on the soil boring logs in Appendix A.

LaBranche East Marsh Creation Project (PO-75)

GeoEngineers completed a geotechnical investigation and design for the LaBranche East Marsh Creation Project, just north of the interstate from this project. This investigation and report was completed in 2010 under the existing contract with NRCS and was followed by a subsequent pilot study of a subsection of the overall marsh creation project to assess constructability. As directed by the NRCS, dredged fill parameters from PO-75 were used for this marsh creation report.

FIELD EXPLORATION

From November 1 through November 5, 2013, 13 soil borings (BHMC-1 through BHMC-12 and BHMC-14) were completed in the marsh creation area to a depth of 30 feet below the mudline and one (BHMC-13) to a depth of 80 feet below the mudline using an airboat-mounted drill rig. All borings were sampled continuously for the top 20 feet, then on 5-foot centers thereafter. The surveyed mudline elevation at the soil boring locations varied from -0.1 to -1.5 feet. Soil boring locations are shown in Figure 2 and detailed soil boring logs are included in Appendix A.

Borehole sampling was conducted in general accordance with applicable ASTM International (ASTM) specifications. High-quality, undisturbed, cohesive and semi-cohesive soil (clay/clayey silt) specimens suitable for laboratory strength testing were obtained using a 30-inch-long, 3-inch

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outside diameter (O.D.), thin-walled steel Shelby tube sampler. The sampler was hydraulically pushed into the ground a distance not exceeding 24 inches per specimen using an Osterberg piston sampler in the top 20 to 30 feet and by pushing with the drill rig for deeper depths.

Immediately upon recovery, each sample was classified in the field by a GeoEngineers field representative based on soil exposed on either end of the Shelby tube. Each Shelby tube was then sealed and stored/transported in a vertical position. Shelby tubes were secured bottom down during transportation to minimize sample disturbance.

Upon completion of each soil boring, the drill rig was repositioned adjacent (±2 feet) to the completed boring and a GEONOR H-10 vane borer instrument was used to perform field vane shear tests at various depths in general accordance with ASTM D 2573. The test consisted of placing a four-blade vane in the in-situ soil and rotating it from aboard the drill rig to determine the torque required to shear a cylindrical soil surface with the vane. The resulting torque was used to determine the in-situ soil undrained shear strength.

LABORATORY TESTING

Laboratory test results are presented on the boring logs and figures included in Appendix A and Appendix B, respectively.

Marsh Area

Each semi-cohesive and cohesive sample was subjected to a laboratory miniature vane (mini vane) shear test prior to extrusion. Upon extrusion, each sample was examined to confirm or modify field classifications. Representative samples were selected for laboratory testing consisting of moisture content, dry unit weight, organic content, fiber content, unconfined compression, unconsolidated undrained compression, sieve analysis, consolidation testing and Atterberg limits.

Lake Borrow Area

The Labranche Central Marsh Creation Project (PO-133) shares a common borrow area in Lake Pontchartrain with the Labranche East Marsh Creation Project (PO-75). Eight (8) soil borings were completed in Lake Pontchartrain in 2010 to study the soil properties in the proposed borrow area.

The soil boring logs and testing results can be found in GeoEngineers’ November 15, 2010 Geotechnical Engineering Services report for the PO-75 project.

SITE CONDITIONS

Project Location

The LaBranche Central Marsh Creation Project (PO-133) is located adjacent to the southwestern corner of Lake Pontchartrain in St. Charles Parish, Louisiana, immediately south of Interstate 10 and about a mile and a half east of the Bonnet Carré Spillway, as shown in Figures 1 and 2.

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Surface Conditions

The surrounding area is generally undeveloped but there are several significant features as listed below.

■ Interstate 10 and a parallel railroad exist north-northeast of the marsh creation area. The clearance beneath the interstate and the railroad wooden trestle will limit the size of equipment that can be launched from the public launches in the Bonnet Carré spillway and access the site.

■ As shown in Figure 2 there are pipelines, overhead power lines, and other features in and around the marsh creation area.

■ The marsh creation area was accessed via a canal with a flow control structure. Equipment and personnel access within the marsh creation area is limited to a few access points, one of which is a private boat launch for small vessels, and two of which are canals with obstacles (a weir and a gate).

On June 27, 2013, representatives of GeoEngineers and NRCS toured the design project area by airboat. Based on our observations and discussions with the NRCS representative during the visit and observations during subsequent work, we offer the following information regarding site conditions.

Water depths in general ranged from 0.3 to 2.8 feet at soil boring locations BHMC-1 through BHMC-14. Weather, wind, and tides can substantially affect water levels. Wind can make the open water rough and difficult to operate equipment that is sensitive to wave action. During our field exploration, BHMC-13-80 was moved to a nearby sheltered location to allow us to sample on a day that was too windy for the airboat-mounted drill to remain stationary at the staked location.

Within the marsh creation area, there were a number of duck blinds and crab traps visible throughout the open water area.

Subsurface Conditions

Subsurface Marsh Stratigraphy

Subsurface profiles based on our soil borings in the marsh creation area are shown on Figures 3A and 3B. The top 10 to 15 feet of the soil profile consisted of very soft peat and organic clay, with some isolated clay layers, particularly near the mudline. At the locations of soil borings BHMC-1, BHMC-2, and BHMC-8 the peat and organic clay extended deeper: to depths of 30 feet (bottom of boring), 28 feet, and 23 feet below the mudline, respectively. Organic clay and peat are high– moisture compressible layers.

Very soft clay was encountered beneath the peat and organic clay in all the soil borings; however, 9 of the 14 soil boring locations encountered layers of loose clayey silt, silt, and/or silty sand.

These silt/sand layers were 10 or more feet thick in several soil borings, but were not consistent in thickness or depth across the site. Soil borings BHMC-7 and BHMC-11 encountered silt/sand layers that appear to be over 10 feet thick and extend below the 30-foot investigation depth. Two other soil borings (BHMC-4 and BHMC-12) appear to have silt/sand layers between 5 and 10 feet

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thick. The other 5 soil borings with silt/sand encountered one or more layers between 1 and 5 feet in thickness, as shown on Figures 3A and 3B.

Soil boring BHMC-13 extended to 80 feet below the mudline. With the exception of the 61- to 63-foot sample, the soil samples from 37 feet to 83 feet below the mudline (EL. -35 ft. to EL. -81 ft.) consisted of very soft to soft gray clay. The 61- to 63-foot sample was loose gray silt. Based on United States Army Corps of Engineers (USACE) maps (Figure 4), it was expected that sand and stiff overconsolidated clay (i.e., Pleistocene deposits) would be encountered at approximately EL. -50 ft.; however, we did not encounter Pleistocene deposits within the exploration depth of BHMC-13.

GeoEngineers expects that Pleistocene deposits are within 100 feet of the mudline and the very soft to soft clay deposits are not much thicker than the 80-foot depth of BHMC-3. Design profiles were developed individually for each soil boring based on laboratory testing results at each soil boring location.

Figures 3A and 3B show subsurface soil profiles through the marsh creation area. Detailed soil boring logs are provided in Appendix A, and Appendix B contains laboratory data. Appendix C contains the assumed design profiles (shear strength, unit weight, and moisture content) for the 14 profiles, based on the laboratory and field testing results. As presented in these profiles, typical peat moisture content (ASTM D 2216) in the proposed marsh creation area is between 300 percent and 1,000 percent, with several tests indicating moisture contents in excess of 1,000 percent. In organic clay, moisture contents are typically between 100 percent and 400 percent. The term “moisture content” is defined in ASTM D 2216 as the ratio of water weight to dry soil solids weight in a given sample.

Borrow Area Stratigraphy

As mentioned previously, no additional soil borings were completed in the borrow area during this investigation. GeoEngineers refers readers to our November 15, 2010 PO-75 Geotechnical Engineering Service report for detailed information regarding the borrow area.

CONCLUSIONS AND RECOMMENDATIONS

General

Soil conditions for this project resemble the Labranche East Marsh Creation Project (PO-75): peat forms a significant portion of the subsurface profile across the site. As such, a portion of the discussion from our geotechnical services report for PO-75 bears repeating in this document (quotation represented by italicized text):

Based on the investigation results, the most critical design issues are the compressibility and design characteristics of the peat present in the proposed marsh creation

April 11, 2014 | Page 5 area. The peat will compress (settle) very quickly when loaded, and also dries and shrinks to a fraction of its initial volume when removed from a submerged condition. The photo given in this text shows how significant the volume change can be for an organic soil after it has been air dried.

The three samples on the left of the photo were initially the same size as the sample on the right.

An important clarification regarding this photo is that the samples shown were dried inside a building with air conditioning over a period of a month or so. In a field scenario, the sample may be able to “wick” up water from below, precipitation events may help to moisten soil, and/or sun and wind may affect the drying rate.

We expect that peat used to construct containment will shrink significantly when excavated from a submerged condition and placed on the existing marsh bank. The extent of shrinkage will depend on how well the peat retains its original moisture in the open air. The results of the PO-75 Labranche East Marsh Creation pilot test, currently under observation, will be instructive in terms of peat behavior both above and below the water surface. Containment dikes constructed from organic near-surface soils were able to contain dredged fill discharged from a 12-inch diameter pipe without disruption to the containment dike integrity.

Peat properties in relation to those of other soils also present a challenge. Again, from the PO-75 geotechnical services report:

Because peat is highly organic, silt and clay fill from the borrow area will weigh substantially more.

The unit weight of peat is slightly more than water and was estimated to be 65 to 70 pounds per cubic foot (pcf) based on testing for this project. The fill being placed was estimated to be 80 to 90 pcf initially and is expected to consolidate to a denser weight of near 100 pcf over time. The light weight and compressibility of peat causes severe settlement problems. The soils beneath peat “feel” very little stress from the peat, because of water buoyancy. When new fill is placed over the peat, not only does the fill increase the stress substantially from the current state of stress, but the peat also compresses rapidly, requiring more fill and causing additional stress. In addition to the compression in the peat, the soil layers underlying the peat experience a significant increase in stress relative to the very low stress currently applied by the submerged peat.

As a consequence of peat’s light weight and weak bonds, some peat will be displaced around the discharge point as the hydraulic fill flows from the pipe into the fill area, as was described anecdotally by NRCS after observing filling activities for the PO-75 pilot study.

Pilot Test Study

The NRCS is monitoring a pilot test project within the limits of the PO-75 marsh creation project area. The pilot test consists of three approximate 300-400 feet by 300-400 feet roughly square test plot areas within which hydraulic fill from Lake Pontchartrain was placed over highly organic compressible soil. Preliminary results from survey monitoring the fill elevation suggest that hydraulic fill settlement estimates may be different than estimated by calculations; however, there is not sufficient data at this time to fully address the discrepancy between estimated and measured settlement.

Available pilot test data suggest settlement observed at the fill surface to date is from consolidation of soil beneath the fill. The average settlement measured at the fill surface through

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February 2014 in Cell 2 was 0.62 feet versus 0.79 feet measured at the base of the fill (settlement plate). Despite being disturbed during filling, the settlement plate in Cell 1 appears to exhibit a similar post-fill settlement trend. The magnitude of the settlement measured at the base of the fill in Cell 2 is similar to GeoEngineers predicted settlement (adjusting for mudline elevation differences); however, the rate seems to be slower than GeoEngineers preliminary estimates.

GeoEngineers has modified our time rate so that subgrade soil settlement occurs over a longer period for this final report, based on the pilot test data.

Two likely explanations for little, or no, hydraulic fill consolidation since the end of fill placement are; 1) consolidation occurred rapidly during filling, or 2) the consolidation process is much slower than estimated by GeoEngineers. The observation that survey crews are walking on hydraulically filled areas to collect elevation data, and that there apparently has been little settlement within the fill, suggests that option 1 (rapid consolidation) is more likely. Consider the data and graph below from the settling column test and low-stress consolidation data presented in the PO-75 report.

VARIATION IN HYDRAULIC FILL PROPERTIES

Void Ratio Wet Density

(pcf) Water Content

Description

4.9 80.2 183 Properties at end of 15-day settling column test

3.8 84.2 142 Properties back-calculated at 0.01 psf stress from low-stress consolidation test

2.85 89.7 106 Properties of re-constituted sample from low-stress consolidation test

2.0 97.0 76 Properties at 25 psf stress from low-stress consolidation test

For this report, GeoEngineers used a 3.8 void ratio at the end of dredging for hydraulic fill settlement calculations. This is considerably less than the void ratio at the end of a 15-day settling column test (4.9) as shown on the graph to the right. A foot of submerged fill with a density of 87 pounds per cubic foot (pcf) exerts a pressure of 25 pounds per square foot (psf) on the underlying soil. As shown on the graph, the difference between a void ratio of 4.9 and a void ratio of 2.0 (void ratio at 25 psf), represents a 49 percent volume change. GeoEngineers

April 11, 2014 | Page 7 offers the following observations regarding the pilot test, settling column test and low-stress consolidation test data for this and the PO-75 project.

■ We suspect hydraulic fill may be consolidating to void ratios of 3, or less, more rapidly (i.e., during construction) than our calculations show.

■ We have no field data for the interval between settling column data (<0.01 psf) and the low stress consolidation test (25 psf). Different assumptions for void ratio during, and at the end of, filling may have significant implications for estimated settlement magnitude and time rate.

■ We recommend collecting samples of in-place pilot study fill material. Undisturbed samples from several locations and depths within Cells 1 and 2 (near center and edges, but not in deeper borrow channel fills) are preferred; however, disturbed samples can be tested for water content to estimate void ratio and density, and also tested for grain size.

■ Until there is data to make conclusions regarding how best to adjust hydraulic fill settlement estimates, GeoEngineers does not believe it is prudent to modify the fill portion of our calculations. For instance, if our fill settlement magnitude estimates are correct, but the time rate is slower than estimated, adjusting our curves assuming that consolidation happened quickly during placement will result in under-predicting the project fill volume. The current curves are likely to err towards excess fill volume, which for project budgeting should be better than under-estimating volume.

The only difference in how GeoEngineers calculated settlement for this report and the PO-75 report is that for the PO-75 report we used a lower initial void ratio: selecting 2.85 as our starting point.

This was a judgment call based on larger volumes and a longer fill time to allow more settlement during fill placement.

Marsh Creation

Settlement

The following design elevations were used to calculate settlement:

■ The existing marsh mudline elevation, as determined by survey at each soil boring location.

■ The average water level was assumed at EL. +0.5 ft., as recommended by NRCS.

■ A marsh creation target elevation of EL. +1.0 ft. at some point between three (3) and 20 years after completion of hydraulic dredge operations.

The thickness of dredged material fill in a contained area decreases due to primary consolidation, secondary compression and desiccation. The consolidation settlement and time rate of settlement analyses for the marsh creation area were performed using the Primary consolidation, Secondary compression, and Desiccation of Dredged Fill (PSDDF) program. Soil boring and laboratory data from low-pressure “self-weight” consolidation and settling column tests conducted for the PO-75 project were used to determine the input parameters for the dredged fill materials.

In addition to the dredged material, the existing soil beneath the fill areas will experience consolidation settlement from the fill overburden. The foundation soils will compress while the fill is placed and, in some areas, the fill will displace the foundation soils to some depth below the mudline, as observed in the PO-75 pilot study. This serves to increase the quantity of fill required

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to reach the design elevation. We are unable to predict the displacement of soils by the dredged fill with any certainty, so we have not included an assessment of soil displacement as part of our analysis. We have accounted for settlement during the filling period by assuming a 30-day filling time and assuming that the settlement caused by the full thickness of fill during those 30 days approximates the additional fill required to reach the design elevation.

When the fill is placed, only a portion is below the natural water table; however, as time passes and the fill densifies, more and more of the fill submerges. As the fill settles/consolidates and more of the mass becomes buoyant (submerges), the stress (weight) of the fill on the underlying soils decreases relative to the time the fill was initially placed. This is a dynamic and complicated process resulting in significant settlement in both the fill and soil underlying the fill. Figures D-1 through D-14 in Appendix D summarize the predicted settlement for initial fill elevations ranging from EL. +1.5 ft. to EL. +4 ft. over a 20-year design life.

The initial fill thickness, the estimated elevation three years after construction, and the estimated long term elevation for both initial fill elevations considered for this evaluation are summarized in the table below. As shown in the table, the EL. +4 ft. initial fill level will provide approximately an additional foot of long-term marsh platform (ranging from 0.6 to 1.0 feet) relative to estimated platform elevations for fill initially placed to EL. +1.5 ft. Observed mudline elevations are higher in the PO-133 project, which helps reduce the required fill thickness and subsequent fill load and self-weight settlement in comparison to PO-75.

MARSH FILL SETTLEMENT SUMMARY

Soil Boring

Initial Fill Elevation = 1.5 ft NAVD 88 Initial Fill Elevation = 4 ft NAVD 88

Fill thickness

(ft)

3-year elevation

(ft NAVD 88)

20-year elevation

(ft NAVD 88)

Fill thickness

(ft)

3-year elevation

(ft NAVD 88)

20-year elevation

(ft NAVD 88)

BHMC-1 2.8 +0.2 +0.1 5.5 +0.9 +0.7

BHMC-2 2.5 +0.3 +0.2 5.5 +1.0 +1.0

BHMC-3 3.0 +0.1 +0.1 5.7 +0.8 +0.8

BHMC-4 2.3 +0.5 +0.5 5.2 +1.5 +1.5

BHMC-5 2.6 +0.4 +0.3 5.3 +1.4 +1.3

BHMC-6 2.7 +0.2 +0.1 5.6 +1.1 +1.0

BHMC-7 2.6 +0.4 +0.3 5.3 +1.4 +1.3

BHMC-8 1.8 +0.6 +0.6 4.6 +1.4 +1.3

BHMC-9 1.7 +0.7 +0.6 4.3 +1.6 +1.3

BHMC-10 2.3 +0.5 +0.4 4.9 +1.4 +1.2

BHMC-11 2.8 +0.5 0.0 5.4 +1.1 +0.9

BHMC-12 2.7 +0.2 +0.1 5.5 +1.1 +1.0

BHMC-13 2.9 +0.4 +0.3 5.8 +1.2 +1.1

BHMC-14 3.1 +0.2 +0.1 5.7 +1.1 +1.0

Note:

Fill Thickness–(Initial Fill Elev.–Surveyed Mudline Elev.)=Initial Foundation Soil Settlement

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Local differences in soil compressibility and mudline elevation will cause low spots in the marsh platform. This will be especially apparent within the borrow channel footprint adjacent to the marsh fill containment dikes, where a “moat” is likely to form due to the extreme difference in mudline elevation between the dike borrow channel and the rest of the marsh creation area. One way to address this disparity in marsh platform is to start filling in the known low areas, move to the rest of the project, and then return to the low areas and refill to the design initial fill level at the end of the fill placement period.

It appears that a single lift of hydraulically dredged fill will generally be sufficient to reach the target marsh fill elevation at this site.

Hydraulic Fill Containment

Containment features for this project should perform the following functions:

■ Containment to prevent overflow of fill into existing marsh areas and into surrounding canals and other waterways; and

■ Containment to prevent flow of fill through shallow water breaches around the perimeter of the proposed marsh creation area as shown in Figure 2.

As discussed in the previous section, we expect hydraulic fill placed to EL. +4 ft. to reach the target marsh platform elevation in most of the cases we examined. In order to accommodate that level of fill, we evaluated earthen containment dikes constructed to EL. +5 ft., allowing 1 foot of freeboard above the maximum design initial fill elevation for slope stability and bearing capacity. Because the surface foundation soils are generally organic, weak, and highly compressible, we assumed that the top 1 foot of foundation soil would be displaced during the filling process. We also assumed that the materials in the top 10 feet of the foundation soil profile (generally organic clay and peat) will be used as fill for the containment dike. We assumed a unit weight of 70 pcf and a cohesion of 60 psf for the containment dike fill. We found that the side slopes were generally stable at 3 feet horizontal for every 1 foot vertical (3H:1V). The berm width used in our analysis was 30 feet from the containment dike toe to the edge of the borrow channel. This berm serves two purposes: 1) it increases the stability of the embankment and 2) it serves as a working platform for marsh buggy excavators. The containment dike geometry and soil properties are summarized in the table below and shown on Figure 5.

SUMMARY OF CONTAINMENT DIKE PROPERTIES

Design Mudline EL.

(ft) (from NRCS)

Assumed Mudline EL (ft)

Crown EL.

(ft)

Crown Width

(ft)

Side Slopes (H:V)

Berm Width (ft)

Fill Total Unit

Weight (pcf)

Fill Cohesion

(psf)

-1 -2 +5 5 3:1 30 70 60

The table below gives a summary of our slope stability and bearing capacity evaluations. Slope stability was computed with and without reinforcement. Due to low factors of safety (FOS) in some profiles, it was assumed that geotextile reinforcement would be required and FOS against global bearing failure was computed along with FOS against lateral squeeze effects (soil movement under the geotextile). Lateral squeeze is the potential of soft foundation soil to squeeze out from beneath

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the dike (i.e., mud wave). This is an evaluation that GeoEngineers has added to our stability assessment based on recent project experience. The geotextile reinforcement was assumed to be a woven fabric with a tensile strength of 400 pounds per linear inch. Two stability scenarios (titled “Condition 1” and “Condition 2”) were studied: the first (Condition 1) was potential of the constructed dike to fail into the borrow channel immediately after dike construction; the second (Condition 2) was potential for dike failure at the maximum hydraulic fill level. The results from both scenarios, both with and without geotextile, are shown below. Slope stability analysis results are also shown on figures in Appendix E.

CONTAINMENT DIKE STABILITY SUMMARY

Boring Id.

FOS without Reinforcement FOS with Reinforcement

Condition

Condition

Global Bearing

FOS

Lateral Squeeze

FOS

Condition

Condition

Global Bearing

FOS

Lateral Squeeze

FOS

BHMC-1 1.84 1.24 1.65 0.80 2.15 1.25 3.22 2.56

BHMC-2 1.90 1.24 1.89 0.88 2.17 1.25 3.68 2.81

BHMC-3 2.34 1.24 1.81 0.85 2.63 1.25 3.52 2.69

BHMC-4 2.64 1.24 1.72 0.96 3.15 1.25 3.40 3.07

BHMC-5 2.62 1.24 2.52 1.29 2.89 1.25 4.94 4.09

BHMC-6 1.82 1.24 1.56 0.80 2.23 1.25 3.07 2.54

BHMC-7 2.24 1.17 1.89 1.06 2.81 1.25 3.75 3.38

BHMC-8 2.56 1.15 2.28 0.95 2.81 1.24 4.40 3.01

BHMC-9 1.97 0.99 1.68 0.78 2.21 1.25 3.26 2.49

BHMC-10 2.66 1.15 1.89 0.81 3.00 1.25 3.65 2.59

BHMC-11 2.48 1.24 1.87 0.84 2.84 1.25 3.63 2.67

BHMC-12 1.99 1.16 1.73 0.81 2.69 1.25 3.36 2.56

BHMC-13 2.90 1.25 2.51 1.04 3.39 1.25 4.84 3.31

BHMC-14 2.54 1.25 2.39 1.22 2.84 1.24 4.69 3.88

For slope stability, a FOS of 1.2 was considered acceptable for this project. For global bearing and lateral squeeze, acceptable FOS was 1.5 and 1.3, respectively. The FOS for lateral squeeze with no reinforcement is somewhat misleading. Lateral squeeze is typically applied to geotextile reinforcement conditions only, and we used a reduced base dike width to represent lateral squeeze without the benefit of a geotextile to distribute loading over the full dike base width. What the unreinforced lateral squeeze FOS suggests is that mud waves are more likely to develop without using a geotextile.

Our slope stability evaluations include allowance for a marsh buggy on the interior (fill side) of the containment dike during dike construction. The presence of the buggy does not significantly affect the containment dike stability, but does increase potential for a failure along the borrow channel

April 11, 2014 | Page 11 cut bank. The marsh buggy excavator position may be operated closer to the containment dike on the 30-foot wide bench, if the borrow channel cut slopes have stability problems.

Foundation soil settlement under the containment dike was computed using the RocScience program Settle3D, which incorporates compressibility and drainage information as well as load dimensions to compute settlement as a function of time. Additional settlement under the containment dike in the form of instantaneous construction settlement occurs during fill placement and has been estimated as 20 percent of the long-term consolidation settlement computed for the foundation soils. Another settlement concern for containment dikes is settlement within the fill itself. For this project, we expect the organic clay and peat to shrink significantly and have estimated consolidation within the dike fill using the method discussed in the calculations approach discussion in Appendix F. Containment dike settlement estimates, including foundation settlement at 6 months, 1, 5, 10, and 20 years, settlement of the fill within itself due to moisture loss and shrinkage, and construction settlement are summarized in the table below. Figures F-1 through F-14 depict containment dike crown elevation change with time based on foundation settlement and fill shrinkage estimates.

CONTAINMENT DIKE SETTLEMENT SUMMARY

Boring Id.

Foundation Settlement (ft) Shrinkage

Settlement (ft)

Construction Settlement

(ft) 6 months 1 year 5 years 10 years 20 years

BHMC-1 1.2 1.5 2.2 2.4 2.5 0.7 0.5

BHMC-2 1.3 1.5 1.7 1.7 1.7 0.6 0.3

BHMC-3 0.9 1.0 1.3 1.3 1.3 0.7 0.3

BHMC-4 0.7 0.8 1.0 1.0 1.0 0.8 0.2

BHMC-5 0.9 0.9 1.0 1.0 1.0 0.7 0.2

BHMC-6 0.5 0.7 1.4 1.5 1.5 0.8 0.3

BHMC-7 0.2 0.4 1.4 1.8 1.9 0.9 0.4

BHMC-8 1.1 1.3 1.7 1.8 1.8 0.7 0.4

BHMC-9 0.9 1.4 1.9 2.1 2.2 0.7 0.4

BHMC-10 0.9 1.2 1.5 1.6 1.7 0.7 0.3

BHMC-11 0.4 0.5 1.0 1.1 1.2 0.8 0.2

BHMC-12 0.9 1.0 1.4 1.4 1.4 0.7 0.3

BHMC-13 1.4 1.5 1.6 1.6 1.6 0.6 0.3

BHMC-14 0.5 0.6 0.9 1.0 1.0 0.8 0.2

A discussion of alternative containment structures is contained in the PO-75 geotechnical services report.

Cut-to-fill Ratios

Based on anecdotal reports from previous coastal projects, we expect the cut-to-fill ratio for containment dike construction to be about 2. Volume change and material loss for the organic

Page 12 | April 11, 2014 | GeoEngineers, Inc.

clays and peats during excavation and placement may increase that estimate for the specific soils at this site.

As mentioned previously, information related to the borrow area, including borrow area consistency, is included in the PO-75 report. As reported for the PO-75 project, the cut-to-fill ratio, based on self-weight consolidation and settling column test results, is about 0.33 immediately after construction and 0.5 thirty days after construction (i.e., fill-to-cut ratios of 3 and 2, respectively). This calculation is for perfectly contained dredged fill. In reality, for marsh creation projects, reported hydraulic dredging cut-to-fill ratios range from about 1 to about 1.5.

CONSTRUCTION CONSIDERATIONS

Based on the site work and evaluations completed for this project, the following are offered with respect to construction.

■ Several points of access may be used to access the property; however, each of them has its own limitations. The private launch is not built for more than private, small vessel use, and damage caused by large construction equipment would most likely require compensation to the owner. Two additional access canals have obstructions to through traffic. One has a flow control structure/weir that crosses the entire canal. The other has a gate that will need to be removed to allow access.

■ A pipeline crosses the northwestern section of the marsh creation area. Care should be taken to avoid damage to the pipeline.

■ Water depth in the marsh creation area is shallow. Construction equipment will need to both be acceptable to the land owner and be able to perform the required tasks.

■ Containment dike construction should be undertaken as gently as practicable. Care should be taken to first place fill at the center of the dike footprint and then move outward to allow any mud waves or other displaced soils to exit the dike footprint. Dikes should be constructed in lifts and shaped after reaching the full specified height.

■ Peat considerations

Peat placed on the existing marsh above the static water level will likely shrink and decay significantly; dikes constructed from this material will require regular maintenance to maintain the desired elevation.

Energy diffusers or other such precautions are recommended to minimize scouring of the organic deposits during hydraulic fill placement.

Peat is a weak material and mud waves should be expected while placing fill.

■ Settlement during hydraulic fill placement will result in an initial fill thickness greater than the elevation difference between the target fill elevation and the pre-fill mudline elevation. A contingency should be built into the expected dredge volumes to avoid cost overruns.

■ Given the pilot test findings to date, the NRCS may want to consider some type of in-place hydraulic fill sampling and testing during construction to determine in-place void ratio and evaluate the potential for settlement after completion of fill activities.

April 11, 2014 | Page 13

LIMITATIONS

We have prepared this report for the exclusive use of the USDA-NRCS in support of design of the proposed LaBranche Central Marsh Creation Project (PO-133) located in St. Charles Parish, Louisiana.

Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of geotechnical engineering in this area at the time this report was prepared. No warranty or other conditions, expressed or implied, should be understood.

Please refer to Appendix G titled “Report Limitations and Guidelines for Use” for additional information pertaining to use of this report.

Page 14 | April 11, 2014 | GeoEngineers, Inc.

Type Name of Services Here Name of Project Here for Type Client Name Here

Type Date of Report Here

Feet

W E

N

PO-133 LaBranche Central Marsh Creation St Charles Parish, Louisiana

VICINITY MAP

Figure 1

Notes:

1. The locations of all features shown are approximate.

2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. can not guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

Reference: Topographic image taken from USGS, DRG-100k Template, Quad Ponchtoula & New Orleans, Dated 9/2005

P:\10\10883018\01\CAD\vicinity map.dwg\TAB:Layout1 modified on Apr 14, 2014 - 9:49am KMCVT

MARSH

CREATION

AREA

STATE OUTLINE

SITE

BORROW

AREA

BHMC-12-30

BHMC-13-80

BHMC-14-30

BHMC-06-30

BHMC-05-30

BHMC-04-30

RAILROAD

I-10

A

A'

B

B'

C

C'

BHMC-10-30WEIR

GATE

TO PRIVATE

BOAT LAUNCH

TO PUBLIC

BOAT LAUNCH

BHMC-03A-30

BHMC-02-30

BHMC-07-30

BHMC-08-30

BHMC-09-30

BHMC-11-30

BHMC-01-30

B

AYO

U

LA BR

AN

C

HE

SHELL PIPELINE

LOCATION

POWERLINE

W E

N

PO-133 LaBranche Central Marsh Creation St Charles Parish, Louisiana

BORING LOCATION PLAN

Figure 2

Legend

BHMC-01-30

Notes:

1. The locations of all features shown are approximate.

2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. can not guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

Reference: 1. Aerial image taken from Google Earth Pro, Licensed to GeoEngineers Inc., Dated 11/14/2012

P:\10\10883018\01\CAD\Boring Location Plan_1_1_8582.DWG\TAB:Layout1 modified on Jan 24, 2014 - 1:39pm KMCJMP

Boring Location

BORING DETAILS

BORING # LATITUDE

BHMC-01-30 N30° 02' 12.0"

LONGITUDE

W90° 20' 52.2"

FEET

DEPTH (FT)

30'

BHMC-02-30 N30° 01' 52.0" W90° 20' 31.7" 30'

BHMC-03-30 N30° 01' 50.25" W90° 20' 01.04" 30'

BHMC-04-30 N30° 01' 11.86" W90° 20' 05.27" 30'

BHMC-05-30 N30° 01' 12.05" W90° 20' 26.18" 30'

BHMC-06-30 N30° 01' 12.25" W90° 20' 48.03" 30'

BHMC-07-30 N30° 01' 25.68" W90° 21' 15.24" 30'

BHMC-08-30 N30° 01' 43.76" W90° 21' 38.80" 30'

BHMC-09-30 N30° 02' 05.18" W90° 21' 31.89" 30'

BHMC-10-30 N30° 02' 18.17" W90° 21' 22.67" 30'

BHMC-11-30 N30° 02' 08.48" W90° 21' 10.85" 30'

BHMC-12-30 N30° 01' 52.87" W90° 21' 16.28" 30'

BHMC-13-80 N30° 01' 41.64" W90° 20' 49.40" 80'

BHMC-14-30 N30° 01' 28.90" W90° 20' 24.37" 30'

A Cross Section

A

Proposed Marsh Creation Boundary

2. Marsh Creation Limits and pipeline location were provided by NRCS, Geotechnical Boring Locations, Sheet 3, Dated 6/3/2013

LOOSE

SILT &

SILTY

SAND

-10

-20

-30

-40

E

LE

V

AT

IO

N

(F T)

-10

-20

-30

-40 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

DISTANCE (FEET)

A A'

BHMC-01-30BHMC-10-30 BHMC-11-30 BHMC-02-30 BHMC-03-30

-10

-20

-30

-40

E

LE

V

AT

IO

N

(F T)

-10

-20

-30

-40 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

DISTANCE (FEET)

C C'

VERY SOFT PEAT & ORGANIC CLAY

WITH OCCASIONAL CLAY LAYERS

VERY SOFT PEAT & ORGANIC CLAY

WITH OCCASIONAL CLAY LAYERSVERY SOFT PEAT &

ORGANIC CLAY

WITH OCCASIONAL

CLAY LAYERS

VERY SOFT CLAY

VERY SOFT CLAY

CLAYEY

SILT

PEAT & ORGANIC CLAY WITH

OCCASIONAL CLAY LAYERS

PEAT & ORGANIC CLAY WITH

OCCASIONAL CLAY LAYERS

VERY SOFT CLAY

LOOSE SILT &

SILTY SAND

VERY SOFT CLAY

BHMC-8-30 BHMC-7-30

BHMC-6-30

BHMC-5-30

MUDLINE

MUDLINE

SUBSURFACE PROFILE A-A' & C-C'

Figure 3A

Notes:

1. The locations of all features shown are approximate.

2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. can not guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

P:

\1

0\

\0

1\ C

AD

\B or in g Lo ca tio n Pl an _1

_1 _8

2.

D W

G \T

AB

:L ay ou t2 (4

) m od ifi ed o n

Ja n

, 2

- 4 :2

4p m

KM

C

D

SE

PO-133 LaBranche Central Marsh Creation St Charles Parish, Louisiana

Reference: Mudline elevations were provided by NRCS, Geotechnical Boring Location, Sheet 3, Dated 6/3/2013.

LEGEND

SILTY CLAY CLAY SILT SILTY SAND

PEAT ORGANIC

CLAY

CLAYEY

SILT

3. All elevations are based on the 1988 North American Vertical Datum.

LOOSE SILT, CLAYEY

SILT, SAND WITH SILT &

WITH CLAY LAYERS

-10

-20

-30

-40

-50

-60

-70

-80

-90

E

LE

V

AT

IO

N

(F T)

-10

-20

-30

-40

-50

-60

-70

-80

-90 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

DISTANCE (FEET)

BHMC-9-30 BHMC-12-30

BHMC-13-80

BHMC-14-30 BHMC-4-30

B B'

VERY SOFT PEAT & ORGANIC CLAY

WITH OCCASIONAL CLAY LAYERS

VERY SOFT PEAT & ORGANIC CLAY

WITH OCCASIONAL CLAY LAYERS

VERY SOFT CLAY

VERY SOFT CLAY

VERY SOFT CLAY

MUDLINE

SILTSILT

SUBSURFACE PROFILE C-C'

Figure 3B

Notes:

1. The locations of all features shown are approximate.

2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. can not guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

P:

\1

0\

\0

1\ C

AD

\B or in g Lo ca tio n Pl an _1

_1 _8

2.

D W

G \T

AB

:L ay ou t2 (5

) m od ifi ed o n

Ja n

, 2

- 1 0:

am

KM

C

D

SE

PO-133 LaBranche Central Marsh Creation St Charles Parish, Louisiana

Reference: Mudline elevations were provided by NRCS, Geotechnical Boring Location, Sheet 3, Dated 6/3/2013.

LEGEND

3. All elevations are based on the 1988 North American Vertical Datum.

LEGEND

SILTY CLAY CLAY SILT SILTY SAND

PEAT ORGANIC

CLAY

CLAYEY

SILT

Miles W E

N

Notes:

1. The locations of all features shown are approximate.

2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. can not guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

Reference: Geology Map taken from USACE, Distribution of Deltaic and Marine Deposits, Sheets Bonnet Carre A & B, Dated 1990

P:

\1

0\

\0

1\ C

AD

\s ec tio n 3B

.d w g\

TA

B :L ay ou t1 m od ifi ed o n Ap r 1 4,

- 9

:5 1a m

KM

C D

SE

LEGEND LEGEND

Figure 4

USACE SUBSURFACE PROFILE

PO-133 LaBranche Central Marsh Creation St Charles Parish, Louisiana

SITE MAP

CROSS SECTION

B B'

MARSH

CREATION

AREA

EL. +5.0 FT.

5'

= 70 PCF

C = 60 PSFWATER @

EL. +0.5 FT.

ASSUMED BOTTOM OF

CONTAINMENT DIKE EL. -2.0 FT

30'ASSUMED

MUDLINE

EL. -1.0 FT.

-5

EXISTING ASSUMED

MUDLINE EL. = -1.0 FT

BORROW

CHANNEL

MARSH BUGGY

EXCAVATOR

HYDRAULIC FILL

ELEV. = 4.0 FT.

PO-133 LaBranche Central Marsh Creation St Charles Parish, Louisiana

ASSUMED CONTAINMENT

DIKE GEOMETRY

Figure 5

Notes:

1. The locations of all features shown are approximate.

2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. can not guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.

P:\10\10883018\01\CAD\Containment Dike Geometry.dwg\TAB:Layout1 modified on Apr 11, 2014 - 1:02pm KMCDSE

Type Name of Services Here Name of Project Here for Type Client Name Here

Type Date of Report Here

APPENDIX A

Logs of Borings

Blowcount is recorded for driven samplers as the number of blows required to advance sampler 12 inches (or distance noted). See exploration log for hammer weight and drop.

A "P" indicates sampler pushed using the weight of the drill rig.

NOTE: The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions.

Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made; they are not warranted to be representative of subsurface conditions at other locations or times.

Perched water observed at time of exploration

SYMBOLS TYPICAL

KEY TO EXPLORATION LOGS

CC

CR

Groundwater observed at time of exploration

Approximate location of soil strata change within a geologic soil unit

Laboratory / Field Tests %F

AL

CA

CP

CS

DS

HA

MC

MD

OC

PM

PP

SA

TX

UC

VS

Standard Penetration Test (SPT)

Bulk or grab

Asphalt Concrete

Measured groundwater level in exploration, well, or piezometer

DESCRIPTIONSLETTER

Distinct contact between soil strata or geologic units

Material Description Contact

Approximate location of soil strata change within a geologic soil unit

Distinct contact between soil strata or geologic units

TS

ADDITIONAL MATERIAL SYMBOLS

AC

Cement Concrete

Sampler Symbol Descriptions

GRAPH

Topsoil/ Forest Duff/Sod

Percent fines Atterberg limits Chemical analysis Laboratory compaction test Consolidation test Direct shear Hydrometer analysis Moisture content Moisture content and dry density Organic content Permeability or hydraulic conductivity Pocket penetrometer Sieve analysis Triaxial compression Unconfined compression Vane shear

Piston

Crushed Rock/ Quarry Spalls

Graphic Log Contact

GC

PT

OH

CH

MH

OL

ORGANIC CLAYS AND SILTS OF

MEDIUM TO HIGH PLASTICITY

GM

GP

GW

DESCRIPTIONS

TYPICAL

LETTERGRAPH

(APPRECIABLE AMOUNT

OF FINES)

MORE THAN 50%

RETAINED ON NO.

200 SIEVE

SYMBOLSMAJOR DIVISIONS

WELL-GRADED SANDS, GRAVELLY

SANDS

SP

PEAT, HUMUS, SWAMP SOILS WITH

HIGH ORGANIC CONTENTS

INORGANIC CLAYS OF HIGH

PLASTICITY

(LITTLE OR NO FINES)

ORGANIC SILTS AND ORGANIC

SILTY CLAYS OF LOW PLASTICITY

INORGANIC CLAYS OF LOW TO

MEDIUM PLASTICITY, GRAVELLY

CLAYS, SANDY CLAYS, SILTY CLAYS,

LEAN CLAYS

CLAYEY SANDS, SAND - CLAY

MIXTURES

SILTY SANDS, SAND - SILT

MIXTURES

CLAYEY GRAVELS, GRAVEL - SAND -

CLAY MIXTURES

POORLY-GRADED GRAVELS,

GRAVEL - SAND MIXTURES

ML

SC

SM

NOTE: Multiple symbols are used to indicate borderline or dual soil classifications

MORE THAN 50%

PASSING NO. 200

SIEVE

MORE THAN 50%

OF COARSE

FRACTION

PASSING NO. 4

SIEVE

CLEAN SANDS

GRAVELS WITH

FINES

CLEAN

GRAVELS

HIGHLY ORGANIC SOILS

SILTS

AND

CLAYS

SILTS

AND

CLAYS

SAND

AND

SANDY

SOILS

GRAVEL

AND

GRAVELLY

SOILS

(LITTLE OR NO FINES)

FINE

GRAINED

SOILS

COARSE

GRAINED

SOILS

SW

MORE THAN 50%

OF COARSE

FRACTION

RETAINED ON NO.

4 SIEVE

CL

WELL-GRADED GRAVELS, GRAVEL -

SAND MIXTURES

POORLY-GRADED SANDS,

GRAVELLY SAND

INORGANIC SILTS, ROCK FLOUR,

CLAYEY SILTS WITH SLIGHT

PLASTICITY

INORGANIC SILTS, MICACEOUS OR

DIATOMACEOUS SILTY SOILS

SILTY GRAVELS, GRAVEL - SAND -

SILT MIXTURES

(APPRECIABLE AMOUNT

OF FINES)

SOIL CLASSIFICATION CHART

LIQUID LIMIT

GREATER THAN 50

LIQUID LIMIT

LESS THAN 50

SANDS WITH

FINES

Shelby tube

Direct-Push

FIGURE A-1

PT

OH

PT

OH

PT

OH

Zero (0) at boat deck Boat deck to water surface = 1.25 feet

Water depth = 2 feet

Mudline at EL. -1.18 feet

Very soft black peat

Very soft black peat (organic content = 43%, fiber = 30%)

Very soft black peat

Very soft black peat ((Su)fvcorr = 0.07 ksf) (specific gravity = 1.6)

Very soft black peat

Very soft black peat

Very soft black peat

Very soft brown peat

Soft brown peat with clay

Very soft black and gray organic clay ((Su)fvcorr

= 0.035…