FSR 17A Soil Informaiton Report.pdf

January 21, 2010

Mark Colgan, P.E.

Vanasse Hangen Brustlin, Inc.

7056 US Route 7

North Ferrisburgh, VT 05473

RE: Letter Update to our Geotechnical Recommendations Report

USDA Forest Service

GMNF FSR 17A over Jenny Coolidge Brook, Weston, VT

Culvert Replacement

GeoDesign #837-19.5

Cc: Tristan Cooke, P.E., VHB

Aaron Guyette, P.E., VHB

Dear Mark:

GeoDesign is pleased to submit this supplemental letter on the foundation recommendations for the culvert replacement in Weston, VT for Green Mountain National Forest (GMNF). This letter updates the bearing pressures and lateral load recommendations given in our original report dated December 16, 2009 to provide LRFD factored resistances for bearing and lateral loading.

1 RECOMMENDATIONS

1.1 Bearing Pressure

The recommended bearing pressure at the proposed bottom of footing elevation (assumed to be designed at six feet below brook bottom elevation with a design width of seven feet) for the proposed open bottom culvert is presented in Table 1 assuming a full scoured out section in front of the footing (i.e., stream side). We assumed a 135 pound per cubic foot unit weight for the glacial till and the groundwater table at the ground surface at the location of the footings.

For comparison, we have provided additional bearing pressures assuming two other scoured depth conditions in front of the proposed footing. Table 2 presents the recommended bearing pressure if half of the soil in front of the footing was scoured out. Table 3 presents the recommended bearing pressure if none of the soil in front of the footing was scoured out. For all tables, the resistance factor used is 0.45 per Table 10.5.5.2.2-1 in the AASHTO LRFD Bridge

Design Specification, 4 th edition 2007 with 2009 Interim Revisions.

GMNF Jenny Coolidge Brook Culvert Replacement Evaluation and Recommendations – Letter update

GeoDesign Project Number: 837-19.5

1/21/10

Table 1 Recommended Net Nominal and Factored Bearing Resistances assuming full scour

(i.e., 6 feet to bottom of footing (BOF)).

Site Expected

Soil Type at Bearing

Elevation

Recommended

Net Nominal

Bearing

Resistance

(psf)

Recommended

Net Factored

Bearing

Resistance

(psf)

Weston

Culvert

Glacial

Till

15,700 7,100

Table 2 Net Nominal and Factored Bearing Resistances assuming half scour (i.e., 3 feet deep or 3 feet above BOF).

Site Expected

Soil Type at Bearing

Elevation

Recommended

Net Nominal

Bearing

Resistance

(psf)

Recommended

Net Factored

Bearing

Resistance

(psf)

Weston

Culvert

Glacial

Till

28,100 12,600

Table 3 Net Nominal and Factored Bearing Resistances assuming no scour.

Site Expected

Soil Type at Bearing

Elevation

Recommended

Net Nominal

Bearing

Resistance

(psf)

Recommended

Net Factored

Bearing

Resistance

(psf)

Weston

Culvert

Glacial

Till

40,500 18,200

1.2 Expected Settlement

We expect the settlement of the structures at the Weston Culvert will be on the order of a ½ to 1 inch or less provided the subgrade is kept firm upon excavation. We expect that settlements will be largely complete during construction.

1.3 Lateral Earth Pressure against backfilled walls and culverts and Sliding Resistance

Recommended earth pressure design criteria are presented below for free draining compacted

Granular Backfill (i.e., VAOT 704.08A):

GMNF Jenny Coolidge Brook Culvert Replacement Evaluation and Recommendations – Letter update

1/21/10

Horizontal Earth Pressures and Sliding Resistance

Abutments and wing walls should be designed for the lateral earth pressures outlined below.

Load factors for earth pressures shall be taken from Table 3.4.1-2 in AASHTO LRFD Bridge

Design Specifications. Resistance factors for bearing and sliding resistance shall be taken from

Table 10.5.5.2.2-1 in AASHTO LRFD Bridge Design Specifications.

Granular Backfill

! Coefficient of Active Earth Pressure, Ka = (1-sin"f)/(1+sin"f) = 0.28

! Coefficient of At-Rest Earth Pressure, Ko = (1-sin"f) = 0.44

! Coefficient of Passive Earth Pressure, Kp = tan (45+"f/2) = 3.5 (Rankine)

! Backfill Density, # = 135 pounds per cubic foot (pcf)

! Friction angle, "f = 34 degrees

Coefficient of friction, (ultimate) f, (from DM-7.2 Table 7.2-63)

! Mass footing concrete on Granular Backfill or crushed stone = 0.55

! Mass footing concrete on Natural Glacial Till Soil = 0.55

Reliance on passive pressure in front of foundation is not recommended due to scour potential.

1.4 Closure

If you have any questions regarding these updated recommendations, please call our office.

Sincerely, GeoDesign, Inc.

Shawn P Kelley, Ph.D. John E. Lens, P.E.

Associate Senior Principal

O:\Client related\CL-800 to 899\837-Vanasse Hangen Brustlin\837-19.5-Weston Culvert\Report\837-19.5 Letter update to Rpt

100121.doc

December 16, 2009

Mark Colgan, P.E.

Vanasse Hangen Brustlin, Inc.

7056 US Route 7

North Ferrisburgh, VT 05473

RE: Geotechnical Recommendations Report

USDA Forest Service

GMNF FSR 17A over Jenny Coolidge Brook, Weston, VT

Culvert Replacement

GeoDesign #837-19.5

Cc: Tristan Cooke, P.E., VHB

Aaron Guyette, P.E., VHB

Dear Mark:

GeoDesign is pleased to submit this report on the foundation recommendations for the culvert replacement in Weston, VT for Green Mountain National Forest (GMNF). This report includes the site evaluation data that we collected (i.e., test pit logs and grain size analysis), our summary of the subsurface conditions at the culvert replacement evaluated, and our recommendations for bearing pressure and subgrade preparation at each crossing for the replacement culvert.

We appreciate the opportunity to be of service to you on this project. If you have any questions, please contact me at 802-674-2033 (Ext. 209).

Sincerely, GeoDesign, Inc.

Shawn P Kelley, Ph.D. John E. Lens, P.E.

Associate Senior Principal

Enclosed: GMNF Culvert replacement evaluation report

Submitted: One electronic copy via email (mcolgan@vhb.com, tcooke@vhb.com, aguyette@vhb.com) and one hard copy mailed U.S. Post.

U n i t e d S t a t e s D e p a r t m e n t o f A g r i c u l t u r e ( U S D A )

F o r e s t S e r v i c e , E a s t e r n R e g i o n

Green Mountain National Forest (GMNF)

Culvert at Jenny Coolidge Brook Replacement

Evaluation and Recommendations

Town of Weston, Windsor County, VT

Vanasse Hangen Brustlin, Inc.

Mr. Mark Colgan, P.E.

7056 US Route 7

North Ferrisburgh, VT 05473

802-425-7788

VHB Project No. 57263.14

GeoDesign Project No. 837-19.5

December 16, 2009

54 Main Street, P.O. Box 699, Windsor, Vermont 05089

(T) 802.674.2033, (F) 802.674.5943 i

TABLE OF CONTENTS

TABLE OF CONTENTS........................................................................................................... i

1 EXECUTIVE SUMMARY

2 INTRODUCTION

2.1 Objective

2.2 Available Information

2.3 Organization of Report

3 SITE LOCATION AND SUBSURFACE DESCRIPTION

3.1 Location

3.2 Geology

3.3 Subsurface Explorations

3.4 Subsurface Description

3.4.1 Overview

3.4.2 Weston Culvert

3.4.3 Groundwater

4 RECOMMENDATIONS

4.1 Bearing Strata/Elevation

4.2 Bearing Pressure

4.3 Expected Settlement

4.4 Lateral Earth Pressure against backfilled abutments and culverts

4.5 Material and Compaction Requirements

4.5.1 Working mat

4.5.2 Soil Material

4.5.3 Compaction Requirements

5 CONSTRUCTION CONSIDERATIONS

6 CONSTRUCTION DOCUMENT REVIEW AND FIELD OBSERVATION

7 LIMITATIONS

8 APPENDICES

ii

APPENDIX 1 – SITE LOCATIONS........................................................................ A-1

APPENDIX 2 –TEST PIT LOCATIONS................................................................. A-4

APPENDIX 3 –TEST PIT PHOTOGRAPHS .......................................................... A-6

APPENDIX 4 –TEST PIT LOGS............................................................................. A-8

APPENDIX 5 – GRAIN SIZE ANALYSIS RESULTS......................................... A-11

APPENDIX 6 – LIMITATIONS............................................................................ A-13

GMNF Jenny Coolidge Brook Culvert Replacement Evaluation and Recommendations

12/16/09

1 EXECUTIVE SUMMARY

The culvert crossing was evaluated for this report (as shown on Figures 1 through 2 in Appendix

1) and firm bearing soils are at expected foundation bearing elevation, approximately six feet below stream bed elevation. The subsurface condition is conducive to shallow foundations for the proposed open bottom culvert crossing with our recommended maximum net allowable bearing pressure of 4,000 psf.

These recommendations were developed from the test pits that were excavated with a track excavator at the Weston culvert site to a depth of 6 feet below stream bed elevation (see Figure

3, Appendix 2). The allowable bearing pressures were estimated using the observed soil type from the test pits and based on corresponding presumptive allowable bearing pressures as given by the AASHTO 2LRFD Bridge Design Specifications 4 th edition 2007 with 2009 Interim

Revisions and our experience in these soil conditions.

Sieve analyses were performed on soil samples within the expected bearing soil strata for the proposed open bottom culvert to support scour analysis by VHB at each brook crossing. These data are presented in Appendix 5.

We recommend that a field engineer from our office observe the excavations for the proposed open bottom culvert. The purpose is to evaluate the in situ soil conditions for consistency between our interpretation, our recommendations and actual field conditions.

2 INTRODUCTION

This report presents our subsurface evaluation and the geotechnical engineering we performed for the brook crossing in the GMNF that are due for replacement per the June 19, 2009 GMNF

2009-2010 Roads and Facilities Maintenance Activities letter authored by Meg Mitchell, Forest

Supervisor. The culvert on FSR 17A is an Aquatic Passage Culvert Reconstruction project. The project location is presented in Figures 1 through 2. We have provided recommended bearing pressures for the one open culvert crossing replacement. Our evaluation included test pits and grain size analysis and through interpretation of this data, we are providing foundation recommendations for the brook crossing.

A copy of this referred letter by GMNF may be found here:

(http://www.fs.fed.us/r9/forests/greenmountain/htm/greenmountain/links/projects/docs/other/cale ndar_year_09/gm_roadsmaint_notice_19jun09.pdf)

12/16/09

2.1 Objective

The planned objective of this report is to provide VHB with a characterization of the subsurface conditions at the expected culvert location and provide geotechnical design criteria for the foundation design for the brook crossing.

2.2 Available Information

The specific type of planned culvert structures was not available to us while preparing this report. We assumed an open bottom pre-cast concrete or metal structure. If other systems are considered, our office should be informed so that the design/construction recommendations provided herein may be evaluated for applicability. Since the type of replacement structure for the culvert crossing is unknown, the manufacturer of the structure should be consulted for construction recommendations (i.e., compaction requirements behind the structure).

2.3 Organization of Report

This report is divided into eight chapters including an appendix chapter. Chapter 1 has an executive summary of the report, and Chapter 2 is an introductory chapter. Chapter 3 presents the site location and subsurface description for the brook crossing. Chapter 4 presents the foundation recommendations and recommended subgrade preparation. Chapter 5 presents construction considerations for the installation of the foundation elements for the proposed open bottom culvert and Chapter 6 presents the construction document review recommendations and field observation recommendations. Chapter 7 presents the report conclusions and Chapter 8 has the appendices for the report.

3 SITE LOCATION AND SUBSURFACE DESCRIPTION

The culvert location, Forest Service Road 17A over Jenny Coolidge Brook, is in the Green

Mountain National Forest, in the Town of Weston, Windsor County, VT as presented in Figure 1 in Appendix 1. For clarity, the brook crossing site will be referred to as Weston Culvert in this report.

3.1 Location

The Weston Culvert is located in Weston, VT in National Forest Land next to the Robert T

Stafford White Rocks National Recreational Area in the GMNF as presented in Figure 2 (see

Appendix 1).

12/16/09

3.2 Geology

Soils and bedrock encountered in boring logs and test pits generally match published mapping data provided on the Surficial Geologic Map of Vermont (Doll, 1970) and the Centennial

Geological Map of Vermont (Doll, 1961). The Surficial Map indicates predominantly glacial till.

Bedrock is mapped as Gneiss from the Mount Holly Complex at the Weston culvert site. Table 1 presents this information.

Table 1 Mapped Soil and Bedrock Information.

Site

Mapped

Elevation

(feet)

Mapped

Surficial(1) Mapped Bedrock(2)

Weston

Culvert ~1990 Glacial Till

MOUNT HOLLY COMPLEX – Felsic-magnetite-biotite GNEISS.

(1) Doll, C.G., Stewart, D.P., and MacClintock, P. (1970). “Surficial Geologic Map of

Vermont.” Vermont Geologic Survey, Map, scale 1:250000.

(2) Doll, C.G., Cady, W.M., Thompson Jr, J.B., and Billings, M.P. (1961). “Centennial Geologic

Map of Vermont.” Vermont Geologic Survey, Map, scale 1:250000.

3.3 Subsurface Explorations

GeoDesign subcontracted two test pits, one on either side of the brook, at the Weston culvert crossing as shown in Figure 3 in Attachment 2. Test pits were excavated by George B. Tucker

Inc. on December 4, 2009. These test pits were excavated to about 6 feet below brook elevation and the location of the test pits were governed by the steep slopes along the brook, therefore limiting our subsurface exploration plan.

GeoDesign personnel observed and logged the test pits. Photographs from each site is presented in Attachment 3. The test pit logs are provided in Attachment 4.

The locations of the test pits shown on the attached figures in Appendix 2 are approximate based on visual observations with reference to the culvert location and edge of brook made in the field by GeoDesign personnel. The test pit locations should be considered accurate only to the degree implied by the method used. The plan for the Weston culvert was received by GeoDesign on the date indicated in Table 2.

Table 2 AutoCADD drawing names and date received.

Drawing Name Site Name Date Received from VHB

57263.14ex.dwg Weston Culvert November 30, 2009

12/16/09

3.4 Subsurface Description

3.4.1 Overview

In general, all test pits terminated in firm in glacial till soil material. The following sections describe the encountered soil types. All test pit logs may be found in Appendix 4. The test pit logs provide an estimated quantity of cobbles and boulders observed in the test pits.

Sieve analyses were performed on soil samples from the anticipated strata at the proposed foundation bearing surface (i.e. strata within six feet below stream bottom) for the proposed open bottom culvert. These tests were performed on grab samples from the test pits. The grab samples did not contain particles larger than coarse gravel and therefore those size particles were excluded from the sieve analysis (i.e., cobbles and boulders were not included in the grab samples due to the size of these particles). The sieve results are presented in Appendix 5.

3.4.2 Weston Culvert

Two test pits were performed at Site 2B. TP-1 was performed on the east brook bank beginngin approximately 1 ½ feet above stream elevation. TP-2 was performed on the west brook bank also beginning approximately 1 ½ feet above stream elevation. Figures 4 and 5 present photographs of the existing culvert. The generalized subsurface profile beginning approximately 1 foot above the brook elevation at the Weston culvert is as follows:

! Silty Sand & Gravel (SSG) – A layer of silty Sand and Gravel consisting of fine to coarse

Sand and fine to coarse Gravel with 10 to 20% silt was observed to approximately 1 foot below brook elevation (approximately 3 foot thick). Frequent boulders and cobbles were present in the sidewall in this layer.

! Glacial Till – Glacial Till was observed directly below the SSG layer. This layer was difficult to excavate and approximately 5 to 10 boulders/cobbles were observed in the excavation that terminated at about 7.5 feet below grade.

The sieve analysis samples for TP-1 and TP-2 were in the glacial till layer (the bearing elevation) and these samples contained 75% and 81% silt, respectively.

3.4.3 Groundwater

Groundwater was encountered in each test pit and the groundwater elevation corresponded to the adjacent brook elevation while digging each test pit at the Weston site.

12/16/09

4 RECOMMENDATIONS

4.1 Bearing Strata/Elevation

The bearing strata will be glacial till for the culvert crossing. The glacial till stratum begins about 3 feet below the ground surface elevation at the test pit locations (which were about 1 ½ feet above the bottom of brook elevation).

4.2 Bearing Pressure

The recommended bearing pressure at the proposed bottom of footing elevation (assumed to be designed at six feet below brook bottom elevation) for the proposed open bottom culvert is presented in Table 3.

12/16/09

Table 3 Recommended Net Allowable Bearing Pressure.

Site Expected Soil

Type at Bearing

Elevation

Silt Content of soil matrix at Bearing

Elevation

Recommended

Maximum net

Allowable

Bearing

Pressure (psf)

Special Subgrade

Construction

Issues

Weston Culvert Glacial Till 40% to 50% 4,000 Softening of subgrade soils underwater – subgrades need protection

4.3 Expected Settlement

We expect the settlement of the structures at the Weston Culvert will be on the order of a ½ to 1 inch provided the subgrade is kept firm upon excavation. We expect that settlements will be largely complete during construction.

4.4 Lateral Earth Pressure against backfilled abutments and culverts

Recommended earth pressure design criteria are presented below:

Table 4 Recommended Earth Pressures.

Static Condition During Wall Construction Recommended Equivalent Fluid Weight of

Soil Backfill (pounds per cubic foot)

At-Rest Pressure Behind Rigid Foundation

Walls (Fixed at top before backfilling)

60*

Active Pressure Behind Walls Free to Rotate at

Top During Backfilling

40*

Passive Resistance in Front of Walls 0**

* These unit weights assume use of free draining compacted Granular Fill backfill against the walls, as described above. Also, where the equivalent wall pressure is less than 240 pounds per square foot (i.e., near the top of wall), use a uniform pressure of 240 pounds per square foot until wall pressure reaches this value, to account for locked in compaction stresses.

** reliance on passive pressure in front of foundation/abutments is not recommended due to scour potential.

We recommend a design friction factor of 0.6 (ultimate) at the base of the wall footings bearing on Granular Soil.

12/16/09

4.5 Material and Compaction Requirements

4.5.1 Working mat

We recommend that a 6 inch working mat consisting of ¾ inch crushed stone (VAOT material

704-02B) enveloped in non-woven geotextile fabric (VAOT material as defined in Table 720-

04A listed as 649.41) be placed beneath the proposed footing.

Fabric should be needle-punched non-woven material. Seams should be overlapped a minimum of 12 inches. During backfill placement, the drop height should not exceed 3 feet and equipment traffic should be kept off the fabric.

4.5.2 Soil Material

Granular Fill for Structures (as shown in Table 704.08A – Granular Fill for Structures, VAOT

2006 Standard Specifications for Construction) is recommended as structural backfill below culvert footings and behind culvert walls. Section 15.1.2 – Spread Footings on Soil from the

VAOT Structures Manual provides additional information.

Material beyond the structural backfill behind the culvert walls and below the roadway should meet VAOT 703.02 Earth Borrow requirements (i.e., reuse existing borrow). Material excavated from the abutment and approach roadway area may be reused as Earth Borrow provided debris and wood/organics are removed and materials can meet compaction requirements.

4.5.3 Compaction Requirements

Compaction should comply with VAOT Specifications where appropriate (i.e., VAOT 204.08).

In addition, all backfill soils beneath and within ‘zone of influence’ of footings as defined as a plane beneath the edge of the footing extending beneath the footing on a slope of 1 Horizontal to

1 Vertical should be compacted to 95% Modified Proctor as defined in ASTM 1557 (or

AASHTO T180) and within 2 percent of optimum water content.

Earth borrow should be compacted per VAOT 203.11 (d), 90% Standard Proctor as defined in

ASTM 698 (or AASHTO T99). The material within the top 24 inches of the road surface (or embankment surface), should be compacted to not less than 95% of the maximum dry density.

Field moisture content should follow the specification in VAOT 203.11 (d) as well.

Compaction requirements behind the proposed pre-cast concrete arch structure/open bottom metal culvert should follow the manufacturers’ recommendations (i.e., compaction requirements in the haunch zone areas).

Table 5 should be used as a guide for soil compaction requirements.

12/16/09

5 CONSTRUCTION CONSIDERATIONS

A key construction consideration is the potential for encountering local variations in the soils at exposed subgrade level and being able to respond promptly. Having on-site geotechnical representation will be critical for the construction of this brook crossing.

Inflow of water into the excavation during construction will most likely occur and measures to control water inflow are critical to this design. A firm and stable subgrade is critical for limiting footing settlement on soil. This requires protecting the shallow footing subgrades from becoming loosened. Having a relatively dry excavation will assist in this requirement. The expected quantity of cobbles and boulders may make installation of a sheet piling system difficult and the contractor should be made aware of such conditions. Dewatering pumps will most likely be required in these six foot excavations. A pre-planned cofferdam and dewatering design is needed for this construction.

While bedrock is unlikely, if blasting is used we recommended that the overblast rock material have large rock pieces removed from the subgrade and the remaining rock be densified with at least four passes in each of two orthogonal direction with a vibratory compactor able to apply a minimum dynamic force of 8000 pounds per foot of drum width. If appropriately sized compaction equipment can not be used, overblast material should be removed and replaced with concrete.

Any overblast rock material must be limited to 15 inches in average diameter. If larger blast-rock is observed at the subgrade elevation, that material should be removed and replaced with smaller rock fill to be able to fill the voids and be compacted. Maximum loose lift thickness is

16 inches. Granular fill may also be placed and compacted using the requirements presented in

Table 5.

In confined areas, smaller vibratory compactors may be used, provided maximum stone size matches the compaction equipment per Table 5.

12/16/09

Table 5 Recommended loose lift thickness for fill and maximum number of passes of compaction equipment.

Maximum

Loose Lift Thickness

Minimum

Number of Passes

Compaction

Method

Maximum

Stone

Size

Below

Structures and Pavement

Less

Critical

Areas

Below

Structures and

Pavement

Less

Critical

Areas

Hand-operated vibratory plate or light roller in confined areas

4” 6” 8” 6 4

Hand-operated vibratory drum rollers weighing at least 1,000#

6” 8” 10” 6 4

Light vibratory drum roller, minimum dynamic force 3,000# per ft. of drum width

6” 10” 14” 6 4

Medium vibratory drum roller, minimum dynamic force 5,000# per ft. of drum width

8” 12” 18” 6 4

Large vibratory drum roller, minimum dynamic force 8,000# per ft. of drum width

10” 16” 24” 6 4

Rock fill should be a well-graded mixture of rock with maximum size matching the compaction equipment being used (i.e., Table 5 requirements).

A 1 foot thick layer of choker material should be placed over top of the compacted overblast rock material. The chocker material should consist of a well-graded mixture of particles to fill the voids in the rock fill surface and should not contain any clayey or silty soil. We recommend a woven geotextile fabric at the surface of the choker layer (VAOT material as defined in Table

720-04A listed as 649.11 with elongation criteria at failure !50%).

6 CONSTRUCTION DOCUMENT REVIEW AND FIELD OBSERVATION

To maintain continuity between the design and construction phases, GeoDesign recommends that it be given the opportunity to review the construction documents. GeoDesign will also review geotechnical aspects of contractor/design submittals for consistency with the specifications and geotechnical design intent.

Our design recommendations are based on GeoDesign providing construction observation of subgrades before backfilling. This will provide us the opportunity to evaluate that the subgrades are as anticipated, and to recommend adjustments as warranted. As such, GeoDesign should

12/16/09 observe that the earthwork and footing bearing surface preparation are being performed per the construction documents.

7 LIMITATIONS

This report is subject to the limitations presented in Appendix 6.

12/16/09

8 APPENDICES

APPENDIX 1 – SITE LOCATIONS

FIGURE 1. Site LocationAPPENDIX 1- SITE LOCATIONS

GMNF Culvert Replacement and

Foundation Recommendations

Town of Weston, VT

GEODESIGN File # 837-19.5

Date 12/15/2009

Location of Culvert

Replacement

A P P E N D

IX

S

IT

E L O C A T

IO

N S

G M N F C u lv e rt R e p la c e m e n t a n d

F o u n d a ti o n R e c o m m e n d a ti o n s

T o w n o f W e s to n V T

G E O D E S

IG

N F ile -1 .5

D a te /1 /2

A p p ro x im a te S c a le m ile

F ig u re W e s to n C u lv e rt L o c a ti o n P la n

G M N F F S R A o v e r J e n n y

C o o lid g e B ro o k

APPENDIX 2 –TEST PIT LOCATIONS

APPENDIX 3 –TEST PIT PHOTOGRAPHS

Figure 4 Photograph of Weston Culverts

Figure 5 Photograph of Site 3B during Test Pits.

APPENDIX 4 –TEST PIT LOGS

APPENDIX 5 – GRAIN SIZE ANALYSIS RESULTS

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APPENDIX 6 – LIMITATIONS

Explorations

1. The analysis and recommendations submitted in this memorandum are based in part upon the data obtained from widely spaced subsurface explorations. The nature and extent of variations between these explorations may not become evident until construction. If variations then appear evident, it will be necessary to reevaluate the recommendations of this memorandum.

2. The generalized soil profiles described in the text are intended to convey trends in subsurface conditions. The boundaries between strata are approximate and idealized and have been developed by interpretations of widely spaced explorations and samples; actual non-engineered fill / native soil transitions are probably more erratic. For specific information, refer to the exploration logs.

3. Water level readings have been made in the exploration test pits at times and under conditions stated on the test pit logs. These data has been reviewed and interpretations made in the text of this report. However, it must be noted that fluctuations in the level of the groundwater may occur due to variations in rainfall, temperature, and other factors occurring since the time measurements were made.

Review

4. In the event that any changes in the nature, design, or location of the proposed structures are planned, the conclusions and recommendations contained in this report should not be considered valid unless the changes are reviewed and conclusions of this report modified or verified in writing by GeoDesign, Inc. It is recommended that this firm be provided the opportunity for a general review of final design and specifications in order that geotechnical engineering recommendations may be properly interpreted and implemented in the design and specifications.

Uses of Report

5. This geotechnical engineering report has been prepared for this project by GeoDesign, Inc.

This report has been prepared for the exclusive use of VHB, Inc. and their design team for specific application to the proposed Culvert Replacements for the Green Mountain National

Forest in Weston, VT in accordance with generally accepted soil and foundation engineering practices. No other warranty, express or implied, is made.

6. This geotechnical engineering report has been prepared for this project by GeoDesign, Inc.

This report is for design purposes only and is not sufficient to prepare an accurate bid.

Contractors wishing a copy of the report may secure it with the understanding that its scope is limited to design considerations only.