Geotechnical Engineering Report - Des Moines, Iowa Bids 2019/08-2018-008/Supplemental...Geotechnical engineering exploration and analysis has been completed for the evaluation of portions

REPORT COVER PAGE

Geotechnical Engineering Report__________________________________________________________________________

Yeader Creek Stabilization ImprovementsDes Moines, Iowa

December 12, 2018Terracon Project No. 08175152-01

Prepared for:HR Green, Inc.Johnston, Iowa

Prepared by:Terracon Consultants, Inc.

Des Moines, Iowa

Terracon Consul tants, Inc. 600 SW 7 t h Street, Sui te M Des Moines, Iowa 50309P (515) 244 3184 F (515) 244 5249 terracon.com

REPORT COVER LETTER TO SIGN

December 12, 2018

HR Green, Inc.5525 Merle Hay Road, Suite 200Johnston, Iowa 50131

Attn: Mr. Chad Mason, P.E.P: (636) 812-4210E: [email protected]

Re: Geotechnical Engineering ReportYeader Creek Stabilization ImprovementsDes Moines, IowaTerracon Project No. 08175152-01

Dear Mr. Mason:

We have performed geotechnical engineering services for the referenced project in generalaccordance with the Standard Agreement for Subconsultant Services, HR Green Project No.170850, dated September 14, 2018. After the initial field exploration was completed, the locationsof proposed improvements was altered, Terracon received approval for an additional threeborings via email on November 13, 2018. This report presents the findings of the subsurfaceexploration and provides geotechnical considerations and recommendations concerning theproposed channel improvements along the applicable portions of the Yeader Creek tributaries.

We appreciate the opportunity to be of service to you on this project. If you have any questionsconcerning this report, or if we may be of further service, please contact us.

Sincerely,Terracon Consultants, Inc.

Theodore D. Bechtum, P.E. Brett E. Bradfield, P.E.Project Engineer Senior Engineering Consultant

Responsive ■ Resourceful ■ Reliable

REPORT TOPICS

INTRODUCTION ............................................................................................................. 2SITE CONDITIONS ......................................................................................................... 2PROJECT DESCRIPTION .............................................................................................. 4GEOTECHNICAL CHARACTERIZATION ...................................................................... 5GRAVITY RETAINING WALLS ...................................................................................... 6STABILITY ANALYSES ................................................................................................. 8EARTHWORK............................................................................................................... 16ENVIRONMENTAL CONSIDERATIONS ...................................................................... 20GENERAL COMMENTS ............................................................................................... 20SIGNATURE PAGE ...................................................................................................... 21ATTACHMENTS ........................................................................................................... 22

Note: This report was also delivered in a web-based format. For more interactive features, please view your projectonline at client.terracon.com.

ATTACHMENTSEXPLORATION AND TESTING PROCEDURESSITE LOCATION AND EXPLORATION PLANSEXPLORATION RESULTSSUPPORTING INFORMATION

Note: Refer to each individual Attachment for a listing of contents.


INTRODUC TION

Geotechnical Engineering ReportYeader Creek Stabilization Improvements

Des Moines, IowaTerracon Project No. 08175152-01

December 12, 2018

INTRODUCTION

Geotechnical engineering exploration and analysis has been completed for the evaluation ofportions of the creek stabilization improvements proposed on the Yeader Creek tributaries in DesMoines, Iowa. The exploration consisted of 8 geotechnical borings to depths ranging fromapproximately 20 to 30 feet below existing ground surface (bgs) and 6 hand auger borings todepths ranging from approximately 5 to 13 feet bgs.

The purpose of these services is to provide information, professional opinions, and/orgeotechnical recommendations relative to:

■ Subsurface soil and rock conditions ■ Groundwater conditions■ Cursory slope stability evaluation of

planned improvements■ Earthwork and subgrade preparation■ Bearing conditions for planned

improvements

Maps showing the sites along the channel and boring locations are shown in the Site Locationand Exploration Plan section. The results of the laboratory testing performed on soil samplesobtained from the sites during the field exploration are included on the boring logs and/or asseparate graphs in Exploration Results.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with thefield exploration and our review of publicly available geologic and topographic maps.

Item Description

Location

Exploration was requested by HR Green in the following areas:See Site Location and Exploration Plan■ Area 1: North of Yeader Creek and south of 511 Titus Avenue (Vicinity

of Boring 1)■ Area 2 (Wall shown on Sheet V.01): East of Yeader Creek tributary

and west of 5310 and 5304 SE 5th Street (Vicinity of Boring 2, 3 and 4).■ Area 3 (Wall shown on Sheet V.02): South of Yeader Creek and west

of Yeader creek tributary near 5201 South Union Street (Vicinity Boring5, 6, and 12)

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Geotechnical Engineering ReportYeader Creek Stabilization Improvements ■ Des Moines, IowaDecember 12, 2018 ■ Terracon Project No. 08175152-01


Item Description■ Area 4 (Wall shown on Sheet V.03): East of Yeader Creek Tributary

and west of 100 East Kenyon Avenue (Vicnity of Boring 7 and 13)■ Area 5: Yeader Creek Tributary, east of 17 East Kenyon Avenue

(Vicinity of Boring 8)■ Area 6: West of Yeader Creek Tributary and east of 5513 South Union

Street (Vicinity of Boring 9 and 10).■ Area 7 (Wall shown on Sheet V.04): East of Yeader Creek Tributary

and west of 5512 Southeast 1st Court (Vicinity of Boring 11 and 14)

Current GroundCover

Existing conditions generally consist of eroded stream banks near theexisting creek. Vegetation consists of trees, shrubs, and grass, with reducedvegetation in areas of recent erosion.

Existing Topography

In general, the area outside the creek banks has relatively flat or rollingtopography in areas with minor erosion. Near the stream, the ground slopesrelatively steeply to the existing stream, often creating a ravine, withoccasional indications of prior bank failures. Elevations and apparent slopesinterpreted from the information provided by Nilles and HR Green areprovided below: The ground slopes vary along the waterways with areas ofnearly vertical slopes, and the following descriptions are only an approximateindication of actual conditions.

■ Area 1: Creek flow line elevation of about 53 feet (City of Des Moinesdatum). North bank has apparent 0.5:1 (horizontal : vertical) slope withelevation of about 66 feet at top of slope. South bank has apparent 1.5:1slope with elevation of about 60 feet at top of slope.

■ Area 2 (Wall shown on Sheet V.01): Creek flow line elevations of about72 to 77 feet. East and west creek banks generally have a 1.5:1 slope,with areas steeper than 1:1. The elevation is about 88 to 91 feet at topof east slope and 83 feet at top of west slope.

■ Area 3 (Wall shown on Sheet V.02): Creek flow line elevation of about69 to 72 feet. West creek bank generally has a slope of about 3:1, withareas steeper than 1:1 near the steam channel. The elevation is about86 feet at the top of the west slope.

■ Area 4 (Wall shown on Sheet V.03): Creek flow line elevation of about77 feet. East and west creek banks generally have slopes of about 1:1or 1.5:1, with areas steeper than 1:1. The elevation is about 93 feet atthe top of the east slope and about 95 feet at the top of the west slope.

■ Area 5: Creek flow line elevation of about 82 to 83 feet. West and eastbank has an apparent 1:1 slope with elevation of about 100 feet at topof west bank and 92 feet at top of east bank.

■ Area 6: Creek flow line elevation of about 86 to 90 feet. West bank hasapparent 1:1 slope or steeper with elevation of about 95 to 100 feet attop of slope.

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Item Description

Existing Topography(cont.)

■ Area 7 (Wall shown on Sheet V.04): Creek flow line elevation of about86 to 90 feet. East bank has an apparent 1.5:1 to 1:1 slope, with areassteeper than 1:1. The elevation is about 100 feet at top of east slope.

Current streambankdistress

Rip rap has been placed in occasional locations of erosion or bank collapsesor sloughing, and debris and refuse was occasionally encountered at theground surface and/or embedded in the banks. Much of the existing streambank is anticipated to be prone to potential instability with increases in porewater pressure, possibly due to rain events, and scour and erosion/removalof material at base of creek.

PROJECT DESCRIPTION

Item Description

Project Description

Based on meetings with HR Green, Terracon understands gravity walls willbe considered at Areas 2, 3, 4, and 7. Information at each of the walls wasprovided on the V Sheets provided by HR Green, dated October 18, 2018.

■ Area 2 (Wall shown on Sheet V.01): Proposed gravity wall with heightof about 7 feet or less and length of about 160 feet on the east side ofYeader Creek behind 5304 and 5310 SE 5th Street.

■ Area 3 (Wall shown on Sheet V.02): Proposed gravity wall with heightof about 7 feet or less and length of about 59 feet on the west side ofYeader Creek behind the apartments at 5201 South Union Street.

■ Area 4 (Wall shown on Sheet V.03): Proposed gravity wall with heightof about 12 feet or less and length of about 98 feet on the east side ofYeader Creek behind 100 Kenyon Avenue.

■ Area 7 (Wall shown on Sheet V.04): Proposed gravity retaining wallwith height of about 8 feet or less and length of about 186 feet on theeast side of Yeader Creek behind 5506, 5512, and 5518 SE 1st Court.

■ Terracon understands that current channel slopes adjacent to theplanned walls at Areas 2, 3, 4, and 7 will be flattened to about 3:1 fromplanned top of wall elevations to near the creek channel, with slopes ofabout 2:1 occasionally at the creek channel (total slope height less thanabout 7 to 12 feet, with about 2 to 3 feet of occasionally steepened slopenear the channel). These slopes are planned to be protected from toeand slope erosion. Terracon anticipates vegetation will be used to helpminimize the potential for surficial sloughs.

■ Earlier versions of project plans indicated retaining walls or slopeflattening at Areas 1, 5, and 6, but Terracon understands thatstabilization improvements including flattening of current back slopes orerosion protection are not currently planned in Areas 1, 5 and 6. Boringswere completed in these areas based on preliminary direction from HRGreen, and the logs are provided in Exploration Results for reference.

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Item Description

Retaining WallConstruction

■ Terracon understands the gravity retaining wall systems consisting ofpre-cast concrete blocks are planned. Drainage will be providedbehind/below the retaining walls.

■ Terracon understands retaining walls will be design-build by selectedcontractor.

GEOTECHNICAL CHARACTERIZATION

We have developed a general characterization of the subsurface soil and groundwater conditionsbased upon our review of the data, geologic setting, and our understanding of the project. Thischaracterization, termed GeoModel, forms the basis of our geotechnical recommendations.Conditions encountered at each exploration point are indicated on the individual logs. TheGeoModel and boring logs are provided in the Exploration Results section.

Stratification boundaries on the GeoModel and boring logs represent the approximate location ofchanges in soil types; in situ, the transition between materials may be gradual. As noted inGeneral Comments, the characterizations are based on widely spaced exploration points acrossthe site, and variations are likely.

NRCS SSURGO soils data indicates the explored areas adjacent to Yeader Creek arerepresented by alluvium near surface soils. Existing fill was encountered in Borings 5 and 6 (Area3) and Boring 13 (Area 4), and were underlain by the apparent alluvial soils. Zones of refuse andrubble were encountered in the existing fill at Borings 5 and 6, and a hydro-carbon odor wasobserved by the drill crew at a depth of about 12 feet in Boring 6.

In general, the borings except Borings 3 and 8 encountered cohesive overburden soils exhibitingvariable plasticity (lean clays and fat clays) and variable sand contents. Sand seams and pocketswere occasionally encountered in the alluvial soils. The alluvial soils generally exhibited mediumstiff to stiff consistency with a zone of very soft to soft soils in Boring 1, 12, and 14. Borings 1, 5to 7, 10, 11, and 12 terminated in the apparent alluvial clay or sand soils.

Shale and residual clay soils were encountered below the alluvial deposits in Borings 2, 4, 9, 13,and 14 and just below the ground surface in Borings 3 and 8. The shale often transitioned fromresidual clay to highly to moderately weathered with depth. Borings 2 to 4, 8 and 9 terminated inthe residual clay and shale.

Groundwater conditions were observed while drilling and shortly after completion of drilling at thesoil borings completed with a drill rig. The water levels observed in the boreholes can be found onthe boring logs in Exploration Results and in the table below.

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Boring NumberApproximate Depth to Groundwater (feet) 1

While Drilling After Drilling

1 16 15

2 13 14

5 13 16

6 17 16

9 12 10

12 13 15½

13 19 19½

14 14 12½

1. Below ground surface

A relatively long period may be necessary for a groundwater level to develop and stabilize in aborehole. Long term observations in piezometers or observation wells sealed from the influence ofsurface water are often required to define groundwater levels in materials of this type.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff,level of nearby waterways, and other factors not evident at the time the borings were performed.Therefore, groundwater levels during construction or at other times in the life of the structuresmay be different than the levels indicated on the boring logs. The possibility of groundwater levelfluctuations should be considered when developing the design and construction plans for theproject.

GRAVITY RETAINING WALLS

The proper design and analysis of a gravity block retaining wall system should includeconsideration of external, internal, and global stability. The external stability considers the wallmass and any supplemental reinforced backfill zone as a monolithic block, and includes sliding,overturning, and bearing capacity failure of the wall. The internal stability should consider thestrength and mechanical connections or interlocking of the selected wall system. Global stabilityconsiders the failure of the slope cross-section above and below the limits of the retaining wallcomponents. The results of these analyses are dependent upon the wall configuration, wall type,slope geometry, surcharge loading, groundwater, as well as soil characteristics (texture, density,shear strength, and moisture content).

Evaluation of the internal stability and final external stability of the wall is the responsibility of thewall designer and was not part of our scope of services and not considered in our analyses.Terracon completed a general characterization of the influence of planned improvements on

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external global stability at one location at each of the four planned wall areas. The results of theseanalyses and associated considerations/opinions are presented in Stability Analysis.

We recommend that Terracon is retained to review grading plans and the design of the retainingwall systems by the selected design-build contractor with regard to external, internal, and globalstability, if desired.

Gravity Retaining Wall Design Considerations

The walls should be designed with a leveling pad comprised of properly compacted, well-gradedcrushed stone or concrete mud mat. If lateral resistance is needed to be derived from passivesoil pressures, in addition to protection against movements due to frost action, we suggest thatthe leveling pad be designed with a minimum embedment depth of at least 42 inches, asmeasured from the base of the foundation to the lowest adjacent grade. The base of the wallshould be constructed to minimize infiltration of surface water into the leveling pad.

It should be noted that drainage of retained soil behind a retaining wall system is essential inmaintaining the integrity of the proposed wall. Saturation of the retained soil can significantlyreduce the material strength and jeopardize the stability of the wall structure. Thus, werecommend that a drainage system be constructed to reduce the potential for surface waterinfiltration or groundwater accumulation behind the retaining wall.

Terracon anticipates the walls could be designed with a maximum contact bearing pressure of upto 1,500 psf and the base of retaining walls should bear on medium stiff to stiff native clay soils,or on new fill extending to suitable native materials. The actual wall contact pressure andsurcharge loadings should be considered in the final external stability analyses. The maximumcontact bearing pressure will depend on the final wall configuration, and Terracon should beretained to review the bearing capacity of the soils supporting the wall during construction.Overexcavation will be required where relatively lower strength soils are encountered or contactpressures exceed the bearing capacity of the soil.

Retaining Wall Foundation Construction Considerations

Retaining wall foundation excavations should be observed by Terracon. If the soil conditionsencountered differ significantly from those presented in this report, supplementalrecommendations will be required. Where unsuitable bearing soils are encountered at the wallbase, the excavations should be extended deeper to suitable soils or as directed by the retainingwall designer and/or geotechnical engineer, and backfilled with properly compacted granularmaterials.

The base of the wall foundation excavation should be free of water and loose soil prior to placingthe aggregate leveling pad and wall backfill. Should the soils at bearing level become excessivelydry, disturbed or saturated, or frozen, the affected soil should be removed prior to wall construction

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STABILITY ANALYSES

Slope stability analyses for a general characterization of the influence of planned improvementswere requested at one location at each of the four planned walls. Cursory global slope stabilityanalyses were completed by Terracon at:

■ Gravity Wall at Area 2 (Plan Sheet V.01 – Approx. Station 0+40)■ Gravity Wall at Area 3 (Plan Sheet V.02 – Approx. Station 0+20)■ Gravity Wall at Area 4 (Plan Sheet V.03 – Approx. Station 0+45)■ Gravity Wall at Area 7 (Plan Sheet V.04 – Approx. Station 1+47)

As presented in Gravity Retaining Walls, the general stability analyses do not consider internalstability or final external stability of the still to be designed retaining wall, and the final externaland internal stability of the wall will need to be determined by the wall designer.

Stability Analysis Criteria

The planned configurations of the gravity walls and altered grading for the creek and tributaryslopes are provided on Sheets V.01, V.02, V.03, and V.04, prepared by HR Green, dated October18, 2018. These configurations are generally described in Project Description. Theconfigurations developed by HR Green were used in Terracon’s analyses of stability of thecompleted channel. One-cross section was considered by Terracon at each wall.

Borings performed in the general areas of the analyzed cross-section locations were used todevelop a generalized profile of subsurface conditions present in the areas. As presented onthe boring logs and in Geotechnical Characterization, the subsurface conditions appear togenerally consist of relatively low strength clay soils, possibly derived from alluvial deposits,underlain with shale bedrock. Borings completed at or near each of the 4 proposed walls wereused to develop a general characterization of stratigraphy at the analyzed cross-section.

Global slope stability analyses were completed utilizing the computer software ”SLOPE/W”, usingthe Morgenstern-Price methodology utilizing optimized circular failure mode analysis. Extensivesearches were performed that resulted in hypothetical failure surfaces with the lowest factors ofsafety against slope failure for the different conditions at each cross-section, i.e., relative amountof relief and existing slope.

As used in engineering, a Factor of Safety is considered to be the sum of resisting forces (thoseforces which resist movement or failure) divided by the sum of driving forces (those forces whichpromote movement or failure). As applied to soil slope stability analysis, factors that resistmovement are primarily the soil shear strength (friction and cohesion), mechanical or man-madedevices to reinforce the slope, and/or counterweight measures at the lower portions of the slopes.

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Factors that drive or promote slope movement are primarily upland soil mass, surcharge loadsand gravity, groundwater or pore water pressure, and seepage forces, where present.

To avoid movement or failure, the resisting forces must be greater than the driving forces andtheir ratio, or Factor of Safety, must be greater than 1. When driving forces exceed the peakresisting forces, movement occurs. Often times, the remaining strength of the failed soil mass,or soil in the zone of shear planes (referred to as residual strength) is lower than the peak strength.Increasing or improving stability of slopes involves increasing the resisting or stabilizing forces ordecreasing the driving (destabilizing) forces.

Slopes that appear stable may have a factor of safety only slightly above 1. Sometimes onlyminor changes to slope geometry, erosion at the toe of slopes or creek banks, surface water flow,or changes in groundwater levels can affect stability of slopes. Movements related to instabilitycan occur rapidly or slowly.

Soil slopes that have noticeably failed provide useful information regarding the conditions of theslope and soil strength characteristics at the time of failure. The factor of safety at the distressedslopes can be considered to be 1.0 and a slope model can be developed. The slope modelrequires information about the slope geometry, assumed shape of failure surface, stratigraphy,shear strength and unit weight of the materials, pore water pressures, and presence of otherimposed loadings. Much of this information is collected during field exploration at the site, andthen is used to constitute the back-analysis model. Back-analysis is the iterative process ofdeveloping a suitable slope model from the assumed near-failure condition. This model is helpfulto better understand the condition of the existing slope, and aids in the evaluation of changes inoverall stability by the planned grading changes, and for the development of measures that shouldbe considered to improve or maintain the overall factor of safety of the slope.

We used back-analysis methods to correlate shear strength parameters for the slope stabilitymodels. Current conditions of slopes were modeled to have factors of safety near 1.0 to developthese parameters; however, actual factor of safety of current slopes are likely somewhat highersince the slopes are intact. When new slope configurations are modeled with these pre-determined shear strength values, the new analysis would indicate either a relative improvementof slope stability, or a decrease which would indicate changes in design should be considered tomaintain stability equal to or above current conditions.

Slope Geometry and Soil Strength Parameters

The effective stress shear strength parameters for each soil stratum were estimated frompublished correlations between Atterberg limits and clay content determined from tests performedon representative samples. Shale parameters were estimated from field results, laboratorytesting, and publications. A back-analysis calculation was also used to adjust some of the shearstrength parameters.

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When used, soil total stress shear strength parameters were generally evaluated from standardpenetration test N-values and/or unconfined compressive strength tests from each soil stratum.

The estimated shear strength parameters for each stratum, as obtained from the field results,laboratory testing, and back-calculation analyses, are shown in the following table. Computeroutputs showing the section, estimated subsurface profile, strength parameters, groundwaterconditions and the cross section of the hypothetical failure surfaces with the computed relativelowest factor of safety on the current slope topography are provided in Supporting Information.

Subsurface Material Shear Strength Parameters

MaterialTotal Stress Parameters Effective Stress Strength Parameters

Friction Angle(Φ’)

Cohesion (c’)psf

Friction Angle(Φ’)

Cohesion (c’)psf

Fat Clay 0 1,200 23 50

Lean Clay 1

(occasionally variablesand content)

0 300 to 800 26 to 27 0 to 50

Residual Shale 0 600 12 100

Shale 0 2,000 15 200

Existing Fill 2 0 750 23 50

1. Some variation in parameters used depending on zone / depth in soil profile. Zone of higherstrength sandy lean clay encountered at wall V.01 modeled with total stress cohesion of 1,500psf.

2. Used to model existing fill encountered in Boring B-13 only.

Stability Analysis Results

As previously mentioned, global slope stability analyses were completed utilizing the computersoftware ”SLOPE/W”, using the Morgenstern-Price methodology utilizing optimized circular failuremode analysis. For the sections analyzed, extensive searches were performed that resulted inhypothetical failure surfaces representing the lowest relative factors of safety with respect to slopefailure for the waterway slopes and adjusted channel geometry.

The profiles of the natural ground surfaces and alternations at the analyzed cross sections wereestimated from the project E and V Sheets provided to Terracon. The soil layer profiles for ouranalysis sections were interpolated or estimated from borings performed in the vicinity of theanalyzed cross sections.

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The following locations were evaluated:

n Gravity Wall at Area 2 – (Plan Sheet V.01 Approx. Station 0+40 +/-)n Gravity Wall at Area 3 – (Plan Sheet V.02 Approx. Station 0+20 +/-)n Gravity Wall at Area 4 – (Plan Sheet V.03 Approx. Station 0+45 +/-)n Gravity Wall at Area 7 – (Plan Sheet V.04 Approx. Station 1+47 +/-)

The results of the analyses for these cross-section conditions are presented in the following table.Computer outputs showing the stability section, strength parameters, groundwater conditions andthe cross section of the hypothetical failure surface with the computed relative lowest factor ofsafety are provided on in Supporting Information. The factors of safety listed for each existingand altered channel cross-section are relative to one another, and it would be preferred to expressthe results as “new channel modification results in a relative change in stability at this location”.

Sheet B.03, dated October 16, 2018 provided by HR Green indicates the gravity wall blocks willhave a width of about 4 feet. The V and E sheets provided by HR Green show a wall width ofabout 1 foot. In the slope stability analyses, as summarized below, the wall was modeled with agravity block width of about 4 feet and unit weight of 140 pcf. The downslope location of the wallshown on the V and E sheets was approximately maintained, with the wall widths extendedupslope beyond the limits shown on the V and E sheets.

Summary of Slope Stability Analyses Results

Analysis Location 1 and ConditionSupportingInformation

Page #

ComputedMinimumFactor of

Safety

Comments

Area 2 GravityWallSheet V.01Station 0+40 +/-

Existing Slope 1 1.07Hypothetical failuresurface extends intoshale bedrock

Proposed Wall 2 2 1.09Hypothetical failuresurface extends intoshale bedrock

Summary: ■ New wall of planned height and grading maintains similar global stability factorof safety as current condition.


Existing Slope 3 0.99 --

Proposed Wall 2 4 0.74 Reduction from currentcondition

Proposed Wallwith Remediation 5 1.06

Conceptual remediationfor shear keyconstructed under wall

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Summary of Slope Stability Analyses Results

Analysis Location 1 and ConditionSupportingInformation

Page #

ComputedMinimumFactor of

Safety

Comments

Summary:

■ New wall of planned height and grading reduces factor of safety by about 25%■ Slope stability remediation (such as shear key) needed to maintain similar

global stability factor as current condition. See Remedial StabilityMeasures. Shear key remediation was considered and depicted in globalstability analysis provided on Supporting Information Page #5.



Proposed Wall 2 7 0.98 Reduction from currentcondition

Summary:

■ New wall of planned height and grading reduces factor of safety by about 7%.■ Slope stability remediation is needed to maintain or increase the global

stability factor of safety relative to current condition. See Remedial StabilityMeasures. A shear key constructed under the wall (as conceptuallyconsidered for the wall shown on Sheet V.03 at Area 4) could be consideredas a potential remediation option.



Proposed Wall 2 9 0.81Reduction from currentcondition

Summary:

■ New wall of planned height and grading reduces factor of safety by about 23%■ Slope stability remediation is needed to maintain or increase the global

stability factor of safety relative to current condition. See Remedial StabilityMeasures. A shear key constructed under the wall (as conceptuallyconsidered for the wall shown on Sheet V.03 at Area 4) could be consideredas a potential remediation option.

Notes Applicable to Each Table1. Refers to section location and station.2. Factor of safety provided is for long term soil shear strength condition.

As indicated in the above table, the planned channel grading improvements with the gravity wallsystem show reductions in overall computed degree of safety of the slopes for walls shown onsheets V.02, V.03 and V.04. Conceptual improvements were considered for the wall systemplanned at Area 4 and shown on Sheet V.03 (most significant reduction in relative stability factorof safety), and similar improvements would likely be applicable for the other locations inconjunction with the planned gravity walls.

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Conditions associated with rises in groundwater levels (e.g. rainfall and/or flooding), rapiddrawdown conditions after channel flooding, and erosion of toe material will all increase the riskof slope instability. These mechanisms are anticipated to be responsible for previous slopeinstabilities. Based on the analyses completed by Terracon, all proposed creek channelimprovements would be subject to similar or greater risk of instability due to these factors.Furthermore, many of the creek channel improvements indicate a reduction in relative factor ofsafety as compared to current conditions, which indicates potential slope instability afterequalization of normal pore water pressure conditions.

The proposed creek channel improvements appear to move the hypothetical slope failure surfaceupslope and engage more material mass. As a result, the consequences of slope failure afterchannel improvements could be more significant.

Structures are currently located near the top of the creek channel slopes in some areas.Surcharge loadings were not considered in our analyses, and it should be understood that existingstructures located in vicinity of the channel and wall improvements could result in surcharge loadsand effect overall stability of slopes. Consideration should be given to underpinning vitalstructures to help reduce the risk of future movement.

It is important to understand that the analyses completed by Terracon were at locations whereslope failures were not readily apparent. Previous areas of slope instability appear to haveoccurred at locations in the areas of the proposed walls shown on Sheet V.01 (Area 2) and SheetV.04 (Area 7), and appear to be characterized by a scarp and reduced or distorted elevationrelative to nearby locations. The factor of safety for slopes associated with previous failuresurfaces will be approximately 1.0. As such, any increase in driving forces without acorresponding increase in resisting forces will lead to further slope movement. It is anticipatedthat fill placement (such as at the “backfill to match grade” locations shown on the Vsheets) in areas of previous slope instability will lead to further movement along theexisting failure surfaces. Remediation or placement of material at the toe of the slope will beneeded to reduce the potential for future movement.

The proposed retaining wall shown on Sheet V.03 (Area 4) appears to tie into an existing retainingwall at station 0+98. The existing wall appears to show signs of distress and movement. If theexisting wall is not stabilized, the proposed wall design must consider the potential for furthermovement and possible failure of the existing wall.

Remedial Stability Measures

Every slope will have a finite failure probability associated with its particular geometry. Theappropriate factor of safety for a slope should reflect the degree of confidence the engineer hasin the selection of soil and groundwater conditions, as well as consequence of failure. For slopeconditions that are in stages of noticeable failure, it is customary in geotechnical engineering to

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seek a relative improvement in factor of safety against slope failure (using site specific soilparameters) of at least 30 percent, and perhaps as high as 50 percent for permanent slopesadjacent to critical structures.

Based on observations during our site visits, it appears that slope failures had occurred inrelatively isolated locations, with shallow, surficial failures near the stream along much of thecorridor. In our opinion, as the waterway erodes these materials, the overall stability of the currentslopes will reach a critical state, resulting in additional slope instability. Additional slope failuresfurther encroach on or extend into private property beyond the waterway easement.Improvements for lining the channel to reduce erosion will reduce the likelihood of theseprogressive movements

Subsurface drainage measures could be considered in upslope locations to control the level ofgroundwater and improve stability. Subsurface drainage improvements are often effective inimproving stability of slopes; however, limitations would include the depths and elevations thatdrains can be installed while maintaining positive gravity flow discharge to the creek level. Trenchdrains with a suitable drain pipe and granular backfill would likely be needed in a series of skewedorientations to the creek channel rather than parallel orientations. Terracon can assist in selectinglocations, spacing and depths for trench drains.

As discussed in Stability Analysis Results, the proposed changes in channel slopes andadditions of retaining walls in the evaluated areas are anticipated to develop a reduced factor ofsafety or negligible changes to the factor of safety of the channel slope. Remedial improvementmeasures could be considered, such as:

■ development of reinforced backfill zones further laterally behind the back of gravity blockwalls,

■ key trenches backfilled with high shear strength materials below the wall, or■ soil nailing.

Geotechnical reinforcement could be placed in backfill zones behind the retaining walls to improvethe stability of the completed wall system. Select granular materials are used for the reinforcedfill, and this would involve exporting and importing materials. The reinforced backfill zones mightneed to extend more than conventionally used lengths of about 70% of the wall height to createa stability improvement relative to existing conditions. Relatively broader cuts to constructadditional length of reinforcement, or reinforcement in conjunction with an additional remediationmethod is anticipated to gain an appreciable effect on existing slope stability. Trees, vegetation,and possibly nearby structures would also be lost during excavations for the reinforced soil areas.

A key trench at the base of the proposed walls or near base of channel could be reviewed as apossible remedial slope stability improvement measure. Proper depth of embedment of the keytrench will need to be considered in the design and construction in order to extend adequate depth

14



below historic or hypothetic failure surfaces. A key trench was conceptually reviewed at the wallshown on Sheet V.03 for Area 4. The conceptual review included a key trench depth of about 10feet below the base of the wall and bottom width of about 5 feet. Low strength cohesive soils areanticipated to extend more than 10 feet below the base of the wall based on borings performedin this area, and shale bedrock with relatively low shear strength was encountered, which limitsthe increase in factor of safety associated with a key trench in this location. The applicability ofthe key trenches will depend on the desired factor of safety increase relative to existing conditionsand constructability of the system. Given the anticipated depth of excavations for the key trenchrequired to increase the factor of safety for the wall and slope configuration shown on Sheet V.03,it will be important to implement construction measures to prevent slope movements duringconstruction, and to control groundwater. Excavation and construction of the key trenches insuccessive relatively short segments should be considered. The key trenches would be backfilledwith high shear strength materials such as interlocking coarse grained granular materials or leanconcrete. Protection against scour extending into these materials would be required at the toe ofthe slope. Similar construction, dewatering, and protection considerations would be applicable toother walls where key trenches are used as remediation. Terracon can complete additional reviewand analysis of these slope improvement measures on request.

Additional remedial measures to improve slope stability could be considered, but were notconceptually reviewed as part of this report, and potential limitations and complexities for thedesign and construction of these improvements are presented below. These measures are notpresented in any particular order of ease or cost of construction, and the suitability or effectivenesswould likely be dependent on the overall extent of the instability or improvement needed.

n Soil nail slope reinforcemento Soil nail systems are installed by either drilling and grouting methods, or air cannon

methods.o Nails would need to extend significant lateral distances to extend beyond hypothetical

failure surfaces.

n Installation of “stub” concrete drilled shafts or aggregate piers at locations at the base of thewallo Drilled elements that are backfilled with select granular material or concrete could be used

to develop increased shear resistance.o Proper depth of embedment and spacing of the drilled elements will need to be considered

in the design and construction in order to extend adequate depth below historic orhypothetical failure surface zones.

Additional analysis of any of these methods, along with additional subsurface exploration wouldbe needed. Formal recommendations for these methods can be developed upon request

15



Slope Instrumentation

Instrumentation, such as survey monuments that would not be disturbed by the earthworkconstruction, should be established at the toe of slopes, top of slopes, and on wall facing inregularly spaced intervals and situations specific to critical structures or greater heights toevaluate if lateral/vertical movement of the improvements are occurring.

The monuments could be surveyed on a regular basis and the surveying of lateral/verticalpositions should be accurate to at least ¼ inch. Inclinometers could also be installed to serve thispurpose, but would be better suited for walls and slopes of significant height. Instrumentation bestsuited for the project and locations can be provided when the project plans for the improvementsare finalized, contractors selected, and methods are discussed. We recommend that thegeotechnical instrumentation be installed and monitored right after the construction phase, withsome limited instrumentation possibly being installed near the toe of the slope prior toconstruction.

EARTHWORK

Site Preparation

Site preparation for the construction of the new walls should commence with stripping ofvegetation, organic soils, and any soft, frozen or otherwise unsuitable materials from the sitesurface. Root systems of trees and brush should be grubbed. Re-use of stripped soil materialscontaining organic matter should be limited to landscaped areas or areas not requiring structuralfill.

During the site preparation for areas where new fills are placed on existing slopes, care shouldbe taken to ensure good bond between the new fill and existing soils. Existing slopes should bebenched to provide horizontal surfaces for placement and compaction of new structural fill. Thebenching and removal of weak near surface soils, where encountered, would help to reduce thepotential for creating a plane of weakness at the interface of the existing slope and new fill. Thewidths of cut to establish benches should be limited to less than 5 feet in consideration of reducingremoval of material at the toes of slopes which could affect the global stability during construction.

Prior to placement of fill, the exposed subgrades should be scarified to a depth of 9 inches,moisture conditioned, and recompacted to the density and moisture content rangesrecommended in section Compaction Requirements. The surficial compaction should aid inproviding a firm base for compaction of new fill and help delineate soft or disturbed areas thatmay exist at or near the exposed subgrade level. Unstable areas should be undercut to stablematerials and the zone replaced with new structural fill.

16



The initially prepared subgrades and subgrade stability in structural fill areas should be observedand tested by Terracon. Terracon personnel should also observe and test fill placement andcompaction.

Site Preparation Drainage and Dewatering

Groundwater is anticipated to be encountered in cut and excavations areas along the slopes. Werecommend that the contractor verify the groundwater conditions/depth immediately prior toconstruction. If signs of groundwater within cut or excavation depths are encountered, anydewatering and diverting of collected seepage necessary should commence prior to or during earlyphases of earthwork. Water and any softened soils should be removed from all fill placement andcompaction surfaces. Diversion ditches and trench drains should be considered along the perimeterof cut areas.

Existing drain tiles should be located, mapped and removed or rerouted/restored to a suitableoutlet. The potential impact on adjacent properties drained by these tiles should be evaluated,and rerouting to a suitable outlet could be necessary in order to maintain drainage, and potentiallyto maintain stability of the slopes.

Some of the temporary construction drainage facilities might eventually be removed, filled orgraded during latter phases of the project; however, some construction drainage measures couldassist in permanent drainage aspects of the project and should be reviewed during construction.

Site grades should be maintained so surface water will flow away from construction areas. Lowelevation areas that collect surface water should be improved during early phases of the gradingso that water does not continue to accumulate in these areas. During earthwork operations, allexposed subgrades should be properly sloped to provide rapid drainage so that water does notaccumulate on surfaces and soften the subgrades. Standing water should be removed as soonas possible to reduce wetting or disturbance of the subgrade soils).

Excavation Considerations

Temporary excavations will be required during grading operations, and construction of newstructures. The stability of these excavations are critical to the integrity of the existing facilities.As a minimum, all temporary excavations should be sloped or braced as required by OccupationalSafety and Health Administration (OSHA) regulations to provide stability and safe workingconditions. Contractors, by their contract, are usually responsible for designing and constructingstable, temporary excavations and should shore, slope or bench the sides of the excavations asrequired, to maintain stability of both the excavation sides and bottom. All excavations shouldcomply with applicable local, state and federal safety regulations, including the current OSHAExcavation and Trench Safety Standards.

17



Planned excavations or cuts could impact the stability of the slopes. Excavations may need to beperformed in short segments and the segments completed prior to progressing to the nextsegment.

Operation of heavy construction equipment on the top or on the slopes of the waterway valleyshould be avoided. Routes for construction equipment traffic should be planned in non-sensitiverelatively flat areas to reduce any potential impact on the stability.

Structural Fill Material Types

Other than aggregate for reinforced backfill, drainage purposes, pipe bedding, or specifiedgranular backfill, we anticipate that a mix of on-site soils removed from excavations and gradingcould be used as fill for shaping of new grades. Structural fill should meet the following materialproperty requirements:

Fill Source 1 Soil Type(USCS Classification)

Acceptable Location for Placement

On-Site Soils Lean clay and sandy lean clay (CL)n Shaping and grading of slopesn Unreinforced wall backfill zonen Air drying should be anticipated

Imported GranularSoils

Granular(GW, GP, GM, GC, SW, SP)

n Backfill below wall systemoverexcavations

n Reinforced backfill zone 2

n Specific gradations required fordrainage course materials

Unsuitable Materials Organic clays (OL, OH)n Not recommended in structural fill

areas

1. Controlled, compacted fill should consist of approved materials that are free of organic matter anddebris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. Asample of each material type should be submitted to the geotechnical engineer for evaluation.

2. Wall designer must specify gradation requirements for soils to be placed in reinforced soil zone.

Compaction Requirements

Item 1 Description

Fill lift thickness

n 9 inches or less in loose thickness when heavy,self-propelled compaction equipment is used.

n 4 inches in loose thickness when hand equipment(e.g., jumping jack, vibratory plate compactor, etc.)is used.

Compaction of cohesive soil 2n At least 95%

18



Item 1 Description

Compaction of granular material 2, 3n Below structures: at least 98%n Adjacent to structures: at least 95% or as

determined by the wall designer

Moisture content of cohesive soil 4 n Within the range of 0% to +4% of optimum moisturecontent

Moisture content of granular material 4, 5 n Workable moisture levels.

1. Compaction and moisture content levels referenced to ASTM D698 standard Proctor maximum drydensity and optimum moisture content, respectively.

2. We recommend structural fill be tested for moisture content and compaction during placement.Should the results of the in-place density tests indicate the specified moisture or compaction limitshave not been met, the area represented by the test should be reworked and retested as requireduntil the specified moisture and compaction requirements are achieved.

3. If the granular material is a coarse sand or gravel, is of a uniform size, or has a low fines content,compaction comparison to relative density may be more appropriate. In this case, granular materialsshould be compacted to at least 70% relative density (ASTM D 4253 and D 4254).

4. Moisture content values as determined at the time of placement and compaction.5. Specifically, moisture levels should be maintained at levels satisfactory for compaction to be

achieved without the granular fill material bulking during placement or pumping when proofrolled.

Grading and Drainage and Landscaping

The site soils and new subgrades prepared with them are considered susceptible to erosion.Exposed slopes should be protected from erosion. Erosion protection, such as vegetation or rip-rap materials, of sloped and grade surfaces should be established as soon as possible.

Sloped areas that are distressed from erosion and development of rills or scour should bepromptly repaired. Repairs may require removal of soils in a relatively wide and benchedconfiguration to allow for proper bonding of new fill.

Grades during and following construction should slope to prevent ponding of water.

Earthwork Construction Considerations

Unstable subgrade conditions could develop during general construction operations, particularly ifthe soils are wetted and/or subjected to repetitive construction traffic. The use of light constructionequipment would aid in reducing disturbance. The use of remotely operated equipment, such as abackhoe, and other light track-mounted equipment would be beneficial to perform cuts and reducesubgrade disturbance. Should unstable subgrade conditions develop, stabilization measuresinvolving excavation and replacement with new structural fill will need to be employed.

19



The geotechnical engineer should be retained during the construction phase of the project toobserve earthwork and to perform necessary tests and observations during subgrade preparation;placement and compaction of structural fill; and backfilling of excavations.

ENVIRONMENTAL CONSIDERATIONS

An apparent hydrocarbon odor was noted by the driller in the soils encountered at a depth ofabout 12 feet bgs in Boring 6. The source of the odor is not known. Geotechnical design andconstruction recommendations included in this report do not address the potential effects ofcontamination on the proposed project. If the detection of an unidentified odor is a concern,additional studies should be conducted to identify the odor, its source and its concentration anddetermine its impact on the project.

GENERAL COMMENTS

Our analysis and opinions are based on our understanding of the project, the geotechnicalconditions in the area, and the data obtained from our site exploration. Natural variations will occurbetween exploration point locations or due to the modifying effects of construction or weather.The nature and extent of such variations may not become evident until during or after construction.Terracon should be retained to review the final design plans and specifications so comments canbe made regarding interpretation and implementation of our geotechnical recommendations inthe design and specifications. Terracon should be retained to provide observation and testingservices during grading, excavation, foundation construction, and other earth-related constructionphases of the project. If variations appear, we can provide further evaluation and supplementalrecommendations. If variations are noted in the absence of our observation and testing serviceson-site, we should be immediately notified so that we can provide evaluation and supplementalrecommendations.

Our Scope of Services does not include either specifically or by implication any environmental orbiological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention ofpollutants, hazardous materials or conditions. If the owner is concerned about the potential forsuch contamination or pollution, other studies should be undertaken.

Our services and any correspondence or collaboration through this system are intended for thesole benefit and exclusive use of our client for specific application to the project discussed andare accomplished in accordance with generally accepted geotechnical engineering practices withno third party beneficiaries intended. Any third party access to services or correspondence issolely for information purposes to support the services provided by Terracon to our client.Reliance on the services and any work product is limited to our client, and is not intended for third

20



parties. Any use or reliance of the provided information by third parties is done solely at their ownrisk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Anyuse of our report in that regard is done at the sole risk of the excavating cost estimator as theremay be variations on the site that are not apparent in the data that could significantly impactexcavation cost. Any parties charged with estimating excavation costs should seek their own sitecharacterization for specific purposes to obtain the specific level of detail necessary for costing.Site safety, and cost estimating including, excavation support, and dewateringrequirements/design are the responsibility of others. If changes in the nature, design, or locationof the project are planned, our conclusions and recommendations shall not be considered validunless we review the changes and either verify or modify our conclusions in writing.

SIGNATURE PAGE

I hereby certify that this engineering document was prepared by me orunder my direct personal supervision and that I am a duly licensedProfessional Engineer under the laws of the State of Iowa.

______________________________________December 12, 2018__Theodore D. Bechtum, P.E. Date

My license renewal date is December 31, 2020.

21

ATTACHMENTS

22


Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 1 of 2

EXPLORATION AND TESTING PROCEDURES

Boring Layout and Elevations: The field exploration consisted of eight geotechnical borings todepths ranging from approximately 20 to 30 feet below existing ground surface (bgs) and six handauger borings to depths ranging from approximately 5 to 13 feet bgs designated. Terraconpersonnel provided the boring layout based on direction from HR Green and the Yeader CreekSteam Stabilization – Phase 2 Preliminary Drawings, dated July 27, 2018. Supplemental boringlayout (borings designated 12 to 14) was based on V sheets dated October 18, 2018 provided byHR Green. Coordinates at the borings locations were generally obtained with a handheld GPSunit (estimated horizontal accuracy of about ±10 feet) and approximate elevations were generallyobtained by interpolation from the survey information provided by Nilles, dated September 13,2018, or from the V sheets prepared by HR Green. The survey data appeared incomplete in thevicinity of Borings 5 and 6, and Terracon personnel approximated the elevations at Borings 5 and6 using a surveyor’s level and rod referencing the manhole rim (elevation 79.81 feet) northeastof the intersection of Yeader Creek and South Union Street. The relative elevations of Borings 2,3, and 4 were approximated by using a survey level and rod. Elevations provided on the logs arerounded to the nearest foot. The locations and elevations of the borings are considered accurateonly to the degree implied by the means and methods used to define them. If more preciselocations and elevations are desired, we recommend the borings be surveyed.

Subsurface Exploration Procedures: The soil borings were advanced with an ATV-mounted drillrig and GeoProbe using continuous flight solid stem augers, and soil sampling was performed usingthin-wall tube and split-barrel sampling procedures. In the thin-walled tube sampling procedure, athin-walled, seamless steel tube with a sharp cutting edge is pushed hydraulically into the soil toobtain a relatively undisturbed sample. In the split-barrel sampling procedure, a standard 2-inch outerdiameter split-barrel sampling spoon is driven into the ground by a 140-pound automatic hammerfalling a distance of 30 inches. The number of blows required to advance the sampling spoon thelast 12 inches of a normal 18-inch penetration is recorded as the Standard Penetration Test (SPT)resistance value. The SPT resistance values, also referred to as N-values, are indicated on theboring logs at the test depths. We observed and recorded groundwater levels during and afterdrilling and sampling. The other borings were advanced with a hand auger and samples fromauger cuttings were obtained for each soil/rock layer interpreted by the drill crew and occasionalthin-wall tube samples were obtained. Borings were backfilled with auger cuttings and bentonitechips after completion.

Our exploration team prepared field boring logs as part of the drilling operations, which includesampling depths, penetration distances, and other sampling information. These field logs includevisual classifications of the materials encountered during drilling and our interpretation of thesubsurface conditions between samples. Final boring logs, prepared from the field logs, represent


Responsive ■ Resourceful ■ Reliable EXPLORATION AND TESTING PROCEDURES 2 of 2

the geotechnical engineer's interpretation of the field logs and include modifications based onobservations and tests of the samples in our laboratory.

Laboratory Testing

In the laboratory, water content tests were performed on portions of the recovered samples. Thedry unit weight of intact, thin-walled tube samples was determined. Unconfined compressivestrength and hand penetrometer tests were performed to estimate the consistency of selectsamples of fine-grained soils. Atterberg limits tests and grain size distribution testing wereperformed on select soil samples. The results of the laboratory tests are shown on the boring logsin Exploration Results at their corresponding sample depths.

The samples were described in the laboratory based on visual observation, texture and plasticity,and the laboratory testing described above. The descriptions of the soils indicated on the boringlogs are in general accordance with the General Notes and the Unified Soil Classification System(USCS), both summarized and included in Supporting Information

SITE LOCATION AND EXPLORATION PLANS

Contents:Site Location PlanExploration Plan (6 pages)

Note: All attachments are one page unless noted above.

SITE LOCATIONYeader Creek Stabilization Improvements ■ Des Moines, IowaDecember 12, 2018 ■ Terracon Project No. 08175152

TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEYQUADRANGLES INCLUDE: DES MOINES SW, IA (1/1/1976) and DES MOINES SE, IA

(1/1/1976).

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND ISNOT INTENDED FOR CONSTRUCTION PURPOSES

GENERAL SITEVICINITY

EXPLORATION PLAN – AREA 1Yeader Creek Stabilization Improvements ■ Des Moines, IADecember 12, 2018 ■ Terracon Project No. 08175152


AERIAL PHOTOGRAPHY PROVIDEDBY MICROSOFT BING MAPS













EXPLORATION PLAN – AREA 6 and 7Yeader Creek Stabilization Improvements ■ Des Moines, IADecember 12, 2018 ■ Terracon Project No. 08175152



EXPLORATION RESULTS

Contents:GeoModels (Areas 1 to 7)Boring Logs (B-1 through B-14)Grain Size Distribution (2 pages)


38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

EL

EV

AT

ION

(M

SL

) (f

eet)

10/11/2018 Terracon Project No. 08175152Yeader Creek Stabilization Improvements Des Moines, Iowa

First Water Observation

Second Water Observation

Final Water Observation

Sandy lean clay with occasional sand seams, refuse, andrubble.

Variable plasticity cohesive soils. Medium stiff to stiff withzones of very soft to soft. Occasoinal sand layers

Possible residual shale

Highly to moderately weathered. Variable colorationand bedding structure.

LEGEND

Lean Clay/Fat Clay

Lean Clay

Silty Sand

Sandy Lean Clay

Layering shown on this figure has been developed by the geotechnicalengineer for purposes of modeling the subsurface conditions asrequired for the subsequent geotechnical engineering for this project.Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

GEOMODEL - AREA 1

Groundwater levels are temporal. The levels shown are representative of the dateand time of our exploration. Significant changes are possible over time.Water levels shown are as measured during and/or after drilling. In some cases,boring advancement methods mask the presence/absence of groundwater. Seeindividual logs for details.

Model Layer General DescriptionLayer Name

1

2

3

4

Existing Fill

Alluvium

Fat clay

Shale

15

16

25.5

2

1

64

66

68

70

72

74

76

78

80

82

84

86

88

90

92


EL

EV

AT

ION

(M

SL

) (f

eet)









LEGEND

Sandy Lean Clay

Fat Clay

Highly Weathered Shale

Shale

Lean Clay

Fat Clay with Sand


NOTES:

GEOMODEL - AREA 2



1

2

3

4

Existing Fill

Alluvium

Fat clay

Shale

14

13

9

13

25.5

2

3

4

2

4

5

3

4

3

6

7.5

2

3

4

50

55

60

65

70

75

80

85

90


EL

EV

AT

ION

(M

SL

) (f

eet)








Highly to moderately weathered. Variable coloration andbedding structure.

LEGEND

Fill

Lean Clay

Sandy Lean Clay

Silty Sand

Clayey Gravel

Fat Clay

Lean Clay with Sand


NOTES:

GEOMODEL - AREA 3


1


2

3

4

Existing Fill

Alluvium

Fat clay

Shale

1

2

16

1312

30.5

5

1

2

1617

12

30.5

6

2

15.5

13

20.5

12

64

66

68

70

72

74

76

78

80

82

84

86

88

90

92


EL

EV

AT

ION

(M

SL

) (f

eet)









LEGEND

Poorly-graded Sand

Fat Clay

Fill

Lean Clay

Fat Clay with Sand

Lean Clay with Sand



NOTES:

GEOMODEL - AREA 4


1


2

3

4

Existing Fill

Alluvium

Fat clay

Shale

2

5

7

1

2

3

19.519

6

24

25.5

13

58

60

62

64

66

68

70

72

74

76

78

80

82

84

86


EL

EV

AT

ION

(M

SL

) (f

eet)









LEGEND

Poorly-graded Sand



NOTES:

GEOMODEL - AREA 5



1

2

3

4

Existing Fill

Alluvium

Fat clay

Shale

4.5

3

8

74

76

78

80

82

84

86

88

90

92

94

96

98

100

102


EL

EV

AT

ION

(M

SL

) (f

eet)









LEGEND

Fat Clay

Shale

Lean Clay with Sand

Lean Clay/Fat Clay

Fat Clay with Sand

Lean Clay


NOTES:

GEOMODEL - AREAS 6 and 7


1


2

3

4

Existing Fill

Alluvium

Fat clay

Shale

2

4

10

12

18

24.8

9

2

9.5

10

2

13

11

2

4

12.5

14

19.5

25.4

14

3540

2750

1500

92

93

66

27

27

29

33

27

25

27

38

96

92

95

48-21-27

36-19-17

33-20-13

52+/-

48+/-

45.5+/-

39.5+/-

1-2-2N=4

1500 (HP)

2000 (HP)

2-2-2N=4

1000 (HP)

0-0-0N=0

500 (HP)

0-0-2N=2

500 (HP)

11

13

13

18

17

16

15

1

2

3

4

5

6

7

Approx. 2 inch root zoneLEAN TO FAT CLAY (CL/CH), trace sand,dark gray brown, medium stiff to stiff

LEAN CLAY (CL), trace sand, brown withgray, medium stiff

SILTY SAND (SM), fine to mediumgrained, brown, very loose

SANDY LEAN CLAY (SC), dark graybrown, very soft to soft

wood fragments (possible tree root)observed in Sample 7Boring Terminated at 25.5 Feet

13.0

17.0

19.5

25.5

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

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ATTERBERGLIMITS

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ELEVATION (Ft.)

Approximate Surface Elev: 65 (Ft.) +/-

WA

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S

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5

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LOCATION

Latitude: 41.5392° Longitude: -93.6057°

See Exploration Plan

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DEPTH

Page 1 of 1

Advancement Method:Power Auger

Abandonment Method:Boring backfilled with Auger Cuttings and Bentonite Chips

600 SW 7th St, Ste MDes Moines, IA

Notes:

Project No.: 08175152

Drill Rig: 844

BORING LOG NO. 1HR Green, Inc.CLIENT:

Driller: MD

Boring Completed: 09-17-2018

PROJECT: Yeader Creek Stabilization Improvements

See Exploration and Testing Procedures for adescription of field and laboratory proceduresused and additional data (If any).

See Supporting Information for explanation ofsymbols and abbreviations.

Des Moines, IowaSITE:

Boring Started: 09-17-2018

15' After Boring

18' After Boring

16' While Sampling

15' After Boring

18' After Boring

WATER LEVEL OBSERVATIONS16' While Sampling

2

3740

2830

1430

94

93

91

20

30

27

24

26

18

16

105

93

96

63-25-38

56-23-33

42-23-19

86+/-

82+/-

78+/-

74+/-

69+/-

65.5+/-

2-3-4N=7

3500 (HP)

3000 (HP)

2-3-5N=8

3500 (HP)

10-22-17N=39

18-23-40N=63

11

16

10

18

15

17

16

1

2

3

4

5

6

7

Approx. 2 inch root zoneSANDY LEAN CLAY (CL), brown and gray,stiff

FAT CLAY (CH), trace sand, dark graybrown, stiff

FAT CLAY (CH), trace sand, gray andbrown with maroon, stiff, possible residualclay

SHALE*, brown with gray, highlyweathered

SHALE*, olive gray with brown, highlyweathered, laminated

SHALE*, olive gray with maroon, highly tomoderately weathered, laminated

Boring Terminated at 25.5 Feet

5.0

9.0

13.0

17.0

22.0

25.5

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.*Classification of rock materials has been estimated based on observation of disturbedsamples. Core samples and/or petrographic analysis may reveal other rock types.

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ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

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5

10

15

20

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TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1


Abandonment Method:Boring backfilled with Bentonite Chips


Notes:


Drill Rig: 844


Driller: MD







14' After Boring

20' After Boring

13' While Drilling

14' After Boring

20' After Boring

WATER LEVEL OBSERVATIONS13' While Drilling

2

3

4

2120

29

34

29

9075+/-

74+/-

10

1

2

Approx. 2 inch root zoneSHALE*, brown, residual clay to highlyweathered shale

SHALE*, olive gray, highly weahtered

Boring Terminated at 5 Feet

4.0

5.0


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1

Advancement Method:Hand Auger



Notes:


Drill Rig: Hand Auger


Driller: MD






Boring Started: 09-17-2018WATER LEVEL OBSERVATIONS

3

4

23

25

18

16

77.5+/-

75+/-

73.5+/-

1

2

3

4

LEAN CLAY (CL), trace sand, dark brown

FAT CLAY (CH), with sand, trace gravel,dark gray brown

FAT CLAY (CH), brown with olive gray,possible residual clay


3.5

6.0

7.5


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:




Driller: MD







2

3

83

20

17

16

17

25

32

27

16

104

102

110

48-22-26

80

76

72

60

56

53.5

5-7-8N=15

2-3-3N=6

3000 (HP)

1-2-3N=5

1000 (HP)

1-2-3N=5

1000 (HP)

5-6-8N=14

12

10

18

12

1

2

3

4

5

6

7

8

Approx. 2 inch root zoneFILL - SANDY LEAN CLAY , brown

FILL - LEAN CLAY , with refuse, with sand,trace gravel, dark brown and brown

FILL - SANDY LEAN CLAY , brown andgray

LEAN CLAY (CL), trace sand, dark brown,medium stiff

SANDY LEAN CLAY (CL), brown and gray,medium stiff

SILTY SAND (SM), trace gravel, brown,medium dense


4.0

8.0

12.0

24.0

28.0

30.5


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)

Surface Elev.: 84 (Ft.)

WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

10

15

20

25

30

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:


Drill Rig: 897


Driller: JG







16' After Boring

20' on 09/20/2019

13' While Drilling

16' After Boring

20' on 09/20/2019


1

2

56

24

17

16

21

29

37

27

1914

98

109

101

81

76

73

61

58

55.5

54.5

2-2-3N=5

2-3-4N=7

2000 (HP)

2-3-3N=6

500 (HP)

1-2-3N=5

10-6-4N=10

8

12

12

12

12

1

2

3

4

5

6

7

8

Approx. 2 inch root zoneFILL - LEAN CLAY , with sand, tracerubble, brown and dark brown

SANDY LEAN CLAY, trace rubble, brownand dark brown

FILL - SANDY LEAN CLAY , with sandseams, brown and dark brown

Driller's Note: Hydro-carbon odorobserved at about 12 feetLEAN CLAY (CL), trace sand, dark brown,medium stiff

SANDY LEAN CLAY (CL), brown and gray,medium stiff

SILTY SAND (SM), trace gravel, brown,medium dense

CLAYEY GRAVEL (GC), with sand, brown,medium denseBoring Terminated at 30.5 Feet

4.0

9.0

12.0

24.0

27.0

29.5

30.5

AS1 = 0 - 12'AS2 = 12-27'


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)

Surface Elev.: 85 (Ft.)

WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

10

15

20

25

30

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:


Drill Rig: 897


Driller: JG







16' After Boring

20' on 09/20/2019

17' While Drilling

16' After Boring

20' on 09/20/2019


1

2

1390

27

26

32

96

77.5+/-

73+/-

1

2

3

SAND (SP), trace gravel, medium tocoarse grained, brownFAT CLAY (CH), with sand seams, darkgray brown, medium stiff


0.5

5.0


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:




Driller: MD







2

4130

22

19 107

82.5+/-

78.5+/-12

1

2

SAND (SP), with gravel, fine to mediumgrained, brownFAT CLAY (CH), gray, very stiff, possibleresidual clay


0.3

4.5


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:




Driller: MD







3

4400

2980

2180

96

32

26

25

26

24

18

16

88

98

98

50-19-31

91+/-

82+/-

78+/-

75+/-

2-2-3N=5

2-2-3N=5

19-47-50/4"

35-50/4"

8

17

10

18

23

16

8

1

2

3

4

5

6

7

Approx. 2 inch root zoneFAT CLAY (CH), trace sand, dark graybrown, stiff to medium stiff

FAT CLAY (CH), trace sand, gray withbrown, medium stiff to stiff

becoming gray

SANDY SHALE*, olive gray with brown,highly weathered

SHALE*, gray, highly weathered, laminated


9.0

18.0

22.0

24.8


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

10

15

20

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:


Drill Rig: 844


Driller: MD






Boring Started: 09-17-201812' While Drilling

10' After Boring

WATER LEVEL OBSERVATIONS

2

4

4310

13

18

16

8

8995+/-

93+/-

90.5+/-

10

1

2

3

4

Approx. 2 inch root zoneFAT CLAY (CH), trace sand, dark graybrown, stiff to very stiff

LEAN CLAY (CL), with sand, gray

LEAN TO FAT CLAY (CL/CH), trace sand,gray


5.0

7.0

9.5


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:




Driller: MD







2

2280

27

27

25

24

32

29

92

98+/-

95+/-

90+/-

87+/-

24

1

2

3

4

5

6

FAT CLAY (CH), with sand, trace gravel,dark brown

LEAN CLAY (CL), trace sand, dark brown

FAT CLAY (CH), trace sand, dark graybrown, stiff

FAT CLAY (CH), trace sand, gray withbrown


2.0

5.0

10.0

13.0


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

10

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:




Driller: MD







2

4660

2990

760

27

25

26

29

36

28

91

95

83

78.5+/-

76+/-

67+/-

63+/-

59.5+/-

4000 (HP)

2-3-3N=6

2500 (HP)

2000 (HP)

0-2-2N=4

1000 (HP)

500 (HP)

0-0-2N=2

500 (HP)

9

14

9

9

17

16

1

2

3

4

5

6

Approx. 2 inch root zoneLEAN CLAY (CL), trace sand and gravel,brownFAT CLAY (CH), trace sand, dark gray,stiff to very stiff

LEAN CLAY (CL), trace sand, gray, stiff tomedium stiff

LEAN CLAY (CL), trace sand, gray, soft

LEAN CLAY (CL), with sand seams, gray,soft


1.5

4.0

13.0

17.0

20.5


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

10

15

20

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:


Drill Rig: Power Auger


Driller: MD







15.5' After Boring

18.5' After Boring

13' While Drilling

15.5' After Boring

18.5' After Boring


2

2310

4580

3590

26

20

28

27

24

27

26

100

91

100

89+/-

87+/-

85+/-

82+/-

77+/-

72+/-

67+/-

65.5+/-

3000 (HP)

3-4-6N=10

6000 (HP)

4500 (HP)

2-3-4N=7

3000 (HP)

2000 (HP)

0-2-3N=5

1000 (HP)

6-10-12N=22

9

18

8

18

12

18

18

1

2

3

4

5

6

7

Approx. 2 inch root zoneFILL - LEAN CLAY , trace sand, darkbrownFILL - SANDY LEAN CLAY , trace gravel,brown with dark brown

FILL - SANDY FAT CLAY , trace gravel,brown

FAT CLAY (CH), trace sand, dark brown,very stiff

LEAN CLAY (CL), trace sand, dark gray,medium stiff to stiff

FAT CLAY (CH), with sand, trace gravel,gray, stiff

LEAN CLAY (CL), with sand, trace gravel,gray, medium stiff

FAT CLAY (CH), with sand, gray brown,very stiff, possible residual clay


2.0

4.0

6.0

9.0

14.0

19.0

24.0

25.5


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

10

15

20

25

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:




Driller: MD






Boring Started: 11-26-201819' While Sampling

19.5' After Boring

WATER LEVEL OBSERVATIONS

1

2

3

2560

3480

880

29

26

25

24

32

20

16

90

97

86

91+/-

87+/-

80.5+/-

78+/-

74.5+/-

4000 (HP)

2-3-4N=7

2500 (HP)

3000 (HP)

2-2-3N=5

2000 (HP)

1000 (HP)

10-22-32N=54

24-40-50/5"

9

14

10

15

17

14

13

1

2

3

4

5

6

7

Approx. 2 inch root zoneFAT CLAY (CH), trace sand, dark brown,stiff

FAT CLAY (CH), trace sand, gray, mediumstiff

LEAN CLAY (CL), with sand, brown,medium stiff to soft

SILTY SHALE*, brown, highly weathered

SHALE*, gray, highly weathered


9.0

13.0

19.5

22.0

25.4


TH

IS B

OR

ING

LO

G IS

NO

T V

ALI

D IF

SE

PA

RA

TE

D F

RO

M O

RIG

INA

L R

EP

OR

T.

GE

O S

MA

RT

LO

G-N

O W

ELL

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

2/4/

18

UN

CO

NF

INE

DC

OM

PR

ES

SIV

ES

TR

EN

GT

H (

psf)

PE

RC

EN

T F

INE

S

WA

TE

RC

ON

TE

NT

(%

)

DR

Y U

NIT

WE

IGH

T (

pcf)

ATTERBERGLIMITS

LL-PL-PI

ELEVATION (Ft.)


WA

TE

R L

EV

EL

OB

SE

RV

AT

ION

S

DE

PT

H (

Ft.)

5

10

15

20

25

SA

MP

LE T

YP

E

FIE

LD T

ES

TR

ES

ULT

S

RE

CO

VE

RY

(In

.)

Sam

ple

ID

LOCATION



GR

AP

HIC

LO

G

MO

DE

L LA

YE

R

DEPTH

Page 1 of 1




Notes:




Driller: MD







12.5' After Boring

18' After Boring

14' While Sampling

12.5' After Boring

18' After Boring

WATER LEVEL OBSERVATIONS14' While Sampling

2

4

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

0.0010.010.1110100

30 40 501.5 2006 810 1441 3/4 1/2 60

GRAIN SIZE IN MILLIMETERS

PE

RC

EN

T F

INE

R B

Y W

EIG

HT

HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS

4 3/8 3 100 1403 2

GRAIN SIZE DISTRIBUTIONASTM D422 / ASTM C136

6 16 20

PROJECT NUMBER: 08175152

SITE: Des Moines, Iowa

PROJECT: Yeader Creek StabilizationImprovements

CLIENT: HR Green, Inc.600 SW 7th St, Ste M

Des Moines, IA

LAB

OR

AT

OR

Y T

ES

TS

AR

E N

OT

VA

LID

IF S

EP

AR

AT

ED

FR

OM

OR

IGIN

AL

RE

PO

RT

.

GR

AIN

SIZ

E: U

SC

S-2

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

0/10

/18

1

1

1

2

3

coarse coarsefine fineCOBBLES

GRAVEL SANDSILT OR CLAY

LEAN CLAY (CL)

LEAN CLAY (CL)

SANDY LEAN CLAY (CL)

LEAN CLAY with SAND (CL)

SANDY LEAN CLAY (CL)

0.013

0.024

0.056

0.022

0.177

4.75

2

9.5

12.5

12.5

48

36

33

0.0

0.0

0.2

1.9

4.5

0.001

0.006

0.014

0.002

0.012

27

38

17

17

WC (%) LL

D30 D10 %Gravel %Fines %Clay

1

1

1

2

3

27

17

13

21

19

20

Boring ID Depth USCS Classification PL PI Cc Cu

D100 D60

4.5 - 6

14 - 16

24 - 25.5

4 - 6

4 - 6

Boring ID Depth %Sand %Silt

medium

92.0

93.1

66.0

83.3

55.9

4.5 - 6

14 - 16

24 - 25.5

4 - 6

4 - 6

8.0

6.9

33.8

14.8

39.6

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

0.0010.010.1110100

30 40 501.5 2006 810 1441 3/4 1/2 60

GRAIN SIZE IN MILLIMETERS

PE

RC

EN

T F

INE

R B

Y W

EIG

HT

HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS

4 3/8 3 100 1403 2

GRAIN SIZE DISTRIBUTIONASTM D422 / ASTM C136

6 16 20

PROJECT NUMBER: 08175152

SITE: Des Moines, Iowa

PROJECT: Yeader Creek StabilizationImprovements

CLIENT: HR Green, Inc.600 SW 7th St, Ste M

Des Moines, IA

LAB

OR

AT

OR

Y T

ES

TS

AR

E N

OT

VA

LID

IF S

EP

AR

AT

ED

FR

OM

OR

IGIN

AL

RE

PO

RT

.

GR

AIN

SIZ

E: U

SC

S-2

081

751

52 Y

EA

DE

R C

RE

EK

ST

AB

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T 1

0/10

/18

4

4

4

5

coarse coarsefine fineCOBBLES

GRAVEL SANDSILT OR CLAY

FAT CLAY (CH)

FAT CLAY (CH)

SHALE (see log)

FAT CLAY (CH)

0.005

0.003

0.013

0.014

9.5

2

4.75

4.75

63

56

42

50

0.2

0.0

0.0

0.0

0.003

30

24

WC (%) LL

D30 D10 %Gravel %Fines %Clay

4

4

4

5

38

33

19

31

25

23

23

19

Boring ID Depth USCS Classification PL PI Cc Cu

D100 D60

4.5 - 6

9 - 10.5

14 - 16

6 - 8

Boring ID Depth %Sand %Silt

medium

94.1

92.8

90.6

96.1

4.5 - 6

9 - 10.5

14 - 16

6 - 8

5.7

7.1

9.4

3.8

SUPPORTING INFORMATION

Contents:Slope Stability Analysis Cross Sections (Pages 1 to 9)General NotesUnified Soil Classification SystemDescription of Rock Properties


1.07

Distance (ft)0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

60

70

80

90

100

110

1200 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Elev

atio

n(ft

)

60

70

80

90

100

110

120

B-4

B-2

B-3

YC 11B Gravity Wall - Sheet V.01Approx. Station 0+40Existing ConditionsTerracon Project No. 08175152

Color Name Model UnitWeight(pcf)

Cohesion'(psf)

Phi'(°)

Fat Clay Mohr-Coulomb 120 50 23

ResidualShale

Mohr-Coulomb 120 100 12

Sandy LeanClay


Shale Mohr-Coulomb 130 200 15

Yeader Creek Stabilization ImprovementsDecember 12, 2018 - Terracon Project No. 08175152 Supporting Information

Page 1 of 9

1.09

Distance (ft)0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

60

70

80

90

100

110

1200 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Elev

atio

n(ft

)

60

70

80

90

100

110

120

B-4

B-2

B-3

YC 11B Gravity Wall - Sheet V.01Approx. Station 0+40Gravity Wall - Long Term ConditionsTerracon Project No. 08175152


Cohesion'(psf)

Phi'(°)


ResidualShale


SandyLean Clay



Wall High Strength 140


Page 2 of 9

0.99

Distance (ft)-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45

60

70

80

90

100

110-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45

Elev

atio

n(ft

)

60

70

80

90

100

110

YC 12 Gravity Wall - Sheet V.03Approx. Station 0+45Existing ConditionsTerracon Project No. 08175152


Cohesion'(psf)

Phi'(°)

Existing Fill Mohr-Coulomb 120 50 23


Lean Clay Mohr-Coulomb 115 50 27

Residual Shale Mohr-Coulomb 120 100 12

B-13


Page 3 of 9

0.74

Distance (ft)-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45

60

70

80

90

100

110-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45

Elev

atio

n(ft

)

60

70

80

90

100

110

YC 12 Gravity Wall - Sheet V.03Approx. Station 0+45Long Term ConditionsTerracon Project No. 08175152


Cohesion'(psf)

Phi'(°)

ExistingFill




ResidualShale



B-13


Page 4 of 9

1.06

Distance (ft)-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45

60

70

80

90

100

110-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45

Elev

atio

n(ft

)

60

70

80

90

100

110



Cohesion'(psf)

Phi'(°)

ExistingFill



Key High Strength 140


ResidualShale



B-13


Page 5 of 9

1.05

Distance (ft)0 10 20 30 40 50 60

60

70

80

90

1000 10 20 30 40 50 60

Elev

atio

n(ft

)

60

70

80

90

100

YC 12 Gravity Wall - Sheet V.02Approx. Station 0+20Existing ConditionsTerracon Project No. 08175152


Cohesion'(psf)

Phi'(°)


Lower Lean Clay Mohr-Coulomb 105 0 26

Upper Lean Clay Mohr-Coulomb 120 50 27

B-12


Page 6 of 9

0.98

Distance (ft)0 10 20 30 40 50 60

60

70

80

90

1000 10 20 30 40 50 60

Elev

atio

n(ft

)

60

70

80

90

100



Cohesion'(psf)

Phi'(°)


Lower LeanClay


Upper LeanClay



B-12


Page 7 of 9

1.05

Distance (ft)0 5 10 15 20 25 30 35 40 45 50 55

75

80

85

90

95

100

105

1100 5 10 15 20 25 30 35 40 45 50 55

Elev

atio

n(ft

)

75

80

85

90

95

100

105

110Section A Gravity Wall - Sheet V.04Approx. Station 1+47Existing ConditionsTerracon Project No. 08175152


Cohesion'(psf)

Phi'(°)




B-14


Page 8 of 9

0.81

Distance (ft)0 5 10 15 20 25 30 35 40 45 50 55

75

80

85

90

95

100

105

1100 5 10 15 20 25 30 35 40 45 50 55

Elev

atio

n(ft

)

75

80

85

90

95

100

105

110Section A Gravity Wall - Sheet V.04Approx. Station 1+47Long TermTerracon Project No. 08175152


Cohesion'(psf)

Phi'(°)





B-14


Page 9 of 9

Yeader Creek Stabilization Improvements Des Moines, IowaOctober 10, 2018 Terracon Project No. 08175152

500 to 1,000

> 8,000

4,000 to 8,000

2,000 to 4,000

1,000 to 2,000

less than 500

Unconfined Compressive StrengthQu, (psf)

AugerCuttings

ShelbyTube

StandardPenetrationTest

Trace

PLASTICITY DESCRIPTION

Water levels indicated on the soil boring logs arethe levels measured in the borehole at the timesindicated. Groundwater level variations will occurover time. In low permeability soils, accuratedetermination of groundwater levels is notpossible with short term water levelobservations.

DESCRIPTION OF SYMBOLS AND ABBREVIATIONSGENERAL NOTES

> 30

11 - 30

1 - 10Low

Non-plastic

Plasticity Index

#4 to #200 sieve (4.75mm to 0.075mm

Boulders

12 in. to 3 in. (300mm to 75mm)Cobbles

3 in. to #4 sieve (75mm to 4.75 mm)Gravel

Sand

Passing #200 sieve (0.075mm)Silt or Clay

Particle Size

Water Level Aftera Specified Period of Time

Water Level After aSpecified Period of Time

Water InitiallyEncountered

Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of theirdry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soilshave less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic,and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituentsmay be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils aredefined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.

GRAIN SIZE TERMINOLOGY

RELATIVE PROPORTIONS OF FINESRELATIVE PROPORTIONS OF SAND AND GRAVEL

DESCRIPTIVE SOIL CLASSIFICATION

LOCATION AND ELEVATION NOTES

SAMPLING WATER LEVEL FIELD TESTSN

(HP)

(T)

(DCP)

UC

(PID)

(OVA)

Standard Penetration TestResistance (Blows/Ft.)

Hand Penetrometer

Torvane

Dynamic Cone Penetrometer

Unconfined CompressiveStrength

Photo-Ionization Detector

Organic Vapor Analyzer

Medium

0Over 12 in. (300 mm)

>12

5-12

<5

Percent ofDry Weight

TermMajor Component of Sample

Modifier

With

Trace

Descriptive Term(s) ofother constituents

>30Modifier

<15

Percent ofDry Weight

Descriptive Term(s) ofother constituents

With 15-29

High

Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. Theaccuracy of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographicalsurvey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined fromtopographic maps of the area.

Standard Penetration orN-Value

Blows/Ft.

Descriptive Term(Density)

CONSISTENCY OF FINE-GRAINED SOILS

Hard

15 - 30Very Stiff> 50Very Dense

8 - 15Stiff30 - 50Dense

4 - 8Medium Stiff10 - 29Medium Dense

2 - 4Soft4 - 9Loose

0 - 1Very Soft0 - 3Very Loose

(50% or more passing the No. 200 sieve.)Consistency determined by laboratory shear strength testing, field visual-manual

procedures or standard penetration resistance

STRENGTH TERMS

> 30

Descriptive Term(Consistency)

Standard Penetration orN-Value

Blows/Ft.

RELATIVE DENSITY OF COARSE-GRAINED SOILS

(More than 50% retained on No. 200 sieve.)Density determined by Standard Penetration Resistance

Geotechnical Engineering Report

Yeader Creek Stabilization Improvements ■ Des Moines, Iowa

October 10, 2018 ■ Terracon Project No. 08175152-01

Responsive ■ Resourceful ■ Reliable UNIFIED SOIL CLASSIFICATION SYSTEM 1 of 1

UNIFIED SOIL C LASSIFIC ATION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Soil Classification

Group

Symbol Group Name B

Coarse-Grained Soils:

More than 50% retained

on No. 200 sieve

Gravels:

More than 50% of

coarse fraction

retained on No. 4 sieve

Clean Gravels:

Less than 5% fines C

Cu 4 and 1 Cc 3 E GW Well-graded gravel F

Cu 4 and/or [Cc<1 or Cc>3.0] E GP Poorly graded gravel F

Gravels with Fines:

More than 12% fines C

Fines classify as ML or MH GM Silty gravel F, G, H

Fines classify as CL or CH GC Clayey gravel F, G, H

Sands:

50% or more of coarse

fraction passes No. 4

sieve

Clean Sands:

Less than 5% fines D

Cu 6 and 1 Cc 3 E SW Well-graded sand I

Cu 6 and/or [Cc<1 or Cc>3.0] E SP Poorly graded sand I

Sands with Fines:

More than 12% fines D

Fines classify as ML or MH SM Silty sand G, H, I

Fines classify as CL or CH SC Clayey sand G, H, I

Fine-Grained Soils:

50% or more passes the

No. 200 sieve

Silts and Clays:

Liquid limit less than 50

Inorganic: PI 7 and plots on or above “A”

line J

CL Lean clay K, L, M

PI 4 or plots below “A” line J ML Silt K, L, M

Organic: Liquid limit - oven dried 0.75 OL Organic clay K, L, M, N

Liquid limit - not dried Organic silt K, L, M, O

Silts and Clays:

Liquid limit 50 or more

Inorganic: PI plots on or above “A” line CH Fat clay K, L, M

PI plots below “A” line MH Elastic Silt K, L, M

Organic: Liquid limit - oven dried 0.75 OH Organic clay K, L, M, P

Liquid limit - not dried Organic silt K, L, M, Q

Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat

A Based on the material passing the 3-inch (75-mm) sieve

B If field sample contained cobbles or boulders, or both, add “with cobbles

or boulders, or both” to group name.

C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded

gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay.

D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded

sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay

E Cu = D60/D10 Cc =

6010

2

30

DxD

)(D

F If soil contains 15% sand, add “with sand” to group name.

G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

H If fines are organic, add “with organic fines” to group name.

I If soil contains 15% gravel, add “with gravel” to group name.

J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.

K If soil contains 15 to 29% plus No. 200, add “with sand” or “with

gravel,” whichever is predominant.

L If soil contains 30% plus No. 200 predominantly sand, add

“sandy” to group name.

M If soil contains 30% plus No. 200, predominantly gravel, add

“gravelly” to group name.

N PI 4 and plots on or above “A” line.

O PI 4 or plots below “A” line.

P PI plots on or above “A” line.

Q PI plots below “A” line.

Geotechnical Engineering Report

Yeader Creek Stabilization Improvements ■ Des Moines, Iowa

October 10, 2018 ■ Terracon Project No. 08175152-01

Responsive ■ Resourceful ■ Reliable ROCK VERSION 1 1 of 2

ROCK VER SION 1

WEATHERING

Term Description

Unweathered No visible sign of rock material weathering, perhaps slight discoloration on major discontinuity surfaces.

Slightly weathered

Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be discolored by weathering and may be somewhat weaker externally than in its fresh condition.

Moderately weathered

Less than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework or as corestones.

Highly weathered

More than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a discontinuous framework or as corestones.

Completely weathered

All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact.

Residual soil All rock material is converted to soil. The mass structure and material fabric are destroyed. There is a large change in volume, but the soil has not been significantly transported.

STRENGTH OR HARDNESS

Description Field Identification Uniaxial Compressive Strength, psi (MPa)

Extremely weak Indented by thumbnail 40-150 (0.3-1)

Very weak Crumbles under firm blows with point of geological hammer, can be peeled by a pocket knife

150-700 (1-5)

Weak rock Can be peeled by a pocket knife with difficulty, shallow indentations made by firm blow with point of geological hammer

700-4,000 (5-30)

Medium strong Cannot be scraped or peeled with a pocket knife, specimen can be fractured with single firm blow of geological hammer

4,000-7,000 (30-50)

Strong rock Specimen requires more than one blow of geological hammer to fracture it

7,000-15,000 (50-100)

Very strong Specimen requires many blows of geological hammer to fracture it 15,000-36,000 (100-250)

Extremely strong Specimen can only be chipped with geological hammer >36,000 (>250)

DISCONTINUITY DESCRIPTION

Fracture Spacing (Joints, Faults, Other Fractures) Bedding Spacing (May Include Foliation or Banding)

Description Spacing Description Spacing

Extremely close < ¾ in (<19 mm) Laminated < ½ in (<12 mm)

Very close ¾ in – 2-1/2 in (19 - 60 mm) Very thin ½ in – 2 in (12 – 50 mm)

Close 2-1/2 in – 8 in (60 – 200 mm) Thin 2 in – 1 ft. (50 – 300 mm)

Moderate 8 in – 2 ft. (200 – 600 mm) Medium 1 ft. – 3 ft. (300 – 900 mm)

Wide 2 ft. – 6 ft. (600 mm – 2.0 m) Thick 3 ft. – 10 ft. (900 mm – 3 m)

Very Wide 6 ft. – 20 ft. (2.0 – 6 m) Massive > 10 ft. (3 m)

Discontinuity Orientation (Angle): Measure the angle of discontinuity relative to a plane perpendicular to the longitudinal axis of the core. (For most cases, the core axis is vertical; therefore, the plane perpendicular to the core axis is horizontal.) For example, a horizontal bedding plane would have a 0-degree angle.

ROCK QUALITY DESIGNATION (RQD) 1

Description RQD Value (%)

Very Poor 0 - 25

Poor 25 – 50

Fair 50 – 75

Good 75 – 90

Excellent 90 - 100

1. The combined length of all sound and intact core segments equal to or greater than 4 inches in length, expressed as a percentage of the total core run length.

Reference: U.S. Department of Transportation, Federal Highway Administration, Publication No FHWA-NHI-10-034, December 2009 Technical Manual for Design and Construction of Road Tunnels – Civil Elements

Documents

Geotechnical Engineering Report - Des Moines, Iowa Bids 2019/08-2018-008/Supplemental...Geotechnical engineering exploration and analysis has been completed for the evaluation of portions