Geotechnical Engineering Report_BCE Storage Shed.pdf

Report Cover Page

BCE Storage Jefferson

Barracks Geotechnical Engineering Report

November 1, 2023 | Terracon Project No. 15235267

Prepared for:

Professional Engineering

Consultants, P.A.

Wichita, KS 67202

11600 Lilburn Park Rd

St. Louis, MO 63146

P (314) 692 9173

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

November 1, 2023

Professional Engineering Consultants, P.A.

303 S Topeka St

Wichita, KS 67202

Attn: Mr. Clay Cline, PE

P: 316-262-2691

E: clay.cline@pec1.com

Re: Geotechnical Engineering Report

BCE Storage Jefferson Barracks

52 Kearney Street

St. Louis, Missouri

Terracon Project No. 15235267

Dear Mr. Cline:

We have completed a subsurface exploration and geotechnical engineering evaluation for the referenced project in general accordance with Terracon Proposal No. P15235267 dated September 29, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, and pavements for the project.

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

Sincerely, Terracon

Ripken B. Dodson, E.I. Kole C. Berg, P.E.

Staff Geotechnical Engineer Principal/Senior Geotechnical Consultant

BCE Storage Jefferson Barracks | St. Louis, Missouri

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Introduction

Project Description

Site Conditions

Geotechnical Characterization

Seismic Site Class

Geotechnical Overview

Earthwork

Demolition

Site Preparation

Excavation

Subgrade Stabilization

Fill Material Types

Fill Placement and Compaction Requirements

Utility Trench Backfill

Grading and Drainage

Earthwork Construction Considerations

Construction Observation and Testing

Shallow Foundations

Shallow Foundation Design Parameters

Foundation Construction Considerations

Floor Slabs

Floor Slab Design Parameters

Floor Slab Construction Considerations

Lateral Earth Pressures

Lateral Earth Pressure Design Parameters

Subsurface Drainage for Below-Grade Walls

Pavements

Pavement Subgrade Preparation

Pavement Section Thicknesses

Pavement Drainage

Pavement Maintenance

General Comments

Figures GeoModel

Attachments

Exploration and Testing Procedures

Facilities | Environmental | Geotechnical | Materials ii

Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Note: This report was originally delivered in a web-based format. Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed new BCE Storage Shed to be located at

52 Kearney Street in St. Louis, Missouri. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ IBC seismic site class

■ Site preparation and earthwork

■ Demolition considerations

■ Foundations

■ Floor slabs

■ Lateral earth pressure parameters

■ Pavements

Drawings showing the site and boring locations are shown on the attached Site

Location Plan and Exploration Plan. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs and/or as separate graphs in Exploration Results.

Project Description

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Item Description

Project Description

The project includes replacement of the existing shed on site with a new 50’x80’ single-story, steel-framed, pre-engineered metal building.

Finished Floor

Elevation

The FFE of the building was not provided. We anticipate the

FFE will match the FFE of the existing building.

Maximum Loads

The following anticipated maximum structural loads were provided by the client:

■ Columns: 50 kips

■ Walls: 3 kips per linear foot (klf)

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Grading

A site grading plan was not provided. We have considered no more than 3 feet of cut or fill will be required to develop final grades.

Below-Grade

Structures No basement level or other below-grade areas are planned.

Free-Standing

Retaining Walls

We understand a cast-in-place concrete retaining wall with a maximum height of 5 feet will be constructed to the east of the building.

Pavements

No information regarding anticipated vehicle types, axle loads, or traffic volumes was provided. We anticipate the pavements will be utilized primarily by passenger vehicles

(cars, pickup trucks, SUV’s) with occasional 2-axle delivery trucks and 3-axle trash collection trucks.

Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading limits, as modifications to our recommendations may be necessary.

Site Conditions

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

Item Description

Parcel

Information

The project is located at 52 Kearney Street in St. Louis, Missouri.

Approximate Latitude/Longitude: 38.5021, -90.2775

See Site Location

Existing

Improvements

Existing building with partially enclosed, fenced lot and asphalt pavement

Current Ground

Cover Asphalt parking lot

Existing

Topography Based on Google Earth, the building site is relatively flat.

Facilities | Environmental | Geotechnical | Materials 3

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based on the subsurface exploration, laboratory data, geologic setting, and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical evaluation. Conditions observed at each boring location are indicated on the individual logs. The individual logs are in the Exploration Results and the GeoModel is in the

Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model

Layer Layer Name General Description

1 Fill-Lean Clay Brown lean clay fill material

2 Lean Clay Brown sandy lean clay

The borings were observed during drilling and shortly after completion of drilling for the presence and level of water. Groundwater was not encountered in the other borings at these times. A longer period of time may be required for groundwater to develop and stabilize in a borehole. Longer term observations in piezometers or observation wells, sealed from the influence of surface water, are often required to define groundwater levels.

Groundwater levels may fluctuate due to seasonal variations in the amount of rainfall, runoff, and other factors not evident at the time the borings were performed. “Perched” water could occur above lower permeability soil layers and/or near the soil/bedrock interface, and “trapped” water could be present within existing fill materials. Therefore , groundwater conditions at other times may be different than the conditions encountered in our exploratory borings. The potential for water level fluctuations and perched water should be considered when developing design and construction plans and specifications for the project.

Seismic Site Class

The seismic design requirements for buildings and other structures are based on Seismic

Design Category. The Site Class is required to determine the Seismic Design Category for a structure. The Site Class is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC). Based on the soil encountered in our subsurface exploration, Seismic Site Class D can be considered for design of the project. The

Facilities | Environmental | Geotechnical | Materials 4 subsurface exploration at this site extended to a maximum depth of 20 feet. The site properties below the maximum boring depth were estimated based on our experience and knowledge of geologic conditions of the general area. Upon request, we could perform deeper borings or geophysical testing to confirm the conditions below the current maximum boring depth.

Geotechnical Overview

Based on conditions encountered at the boring locations, it appears feasible to support the new building on shallow spread footings bearing on medium stiff to sti ff native clay or engineered fill materials.

Existing foundations, walls, slabs, pavements, and associated utilities of existing structures should be removed prior to the construction of the new building and pavements. Care should be taken to thoroughly remove all existing improvements that would interfere with the proposed new construction. Excavations created by demolition/removal of existing features should be backfilled with engineered fill that is placed and compacted as recommended in this report. The demolition contractor should be aware of project requirements for complete removal of existing features, observation/testing of the base of demolition excavations prior to backfilling, use of appropriate backfill materials, and proper placement/compaction/testing of backfill materials so that removal of the demolition contractor’s backfill materials and replacement under controlled conditions is not necessary when building construction commences.

Underground utility lines may be present within the proposed construction area. If these utilities are to remain in place, we recommend that the backfill be tested by a representative of Terracon at the time of construction. If these utilities are to be relocated, the resulting trenches should be overexcavated, backfilled, and tested in accordance with the recommendations in the Earthwork section of this report.

Existing fill materials composed of lean clay with gravel were encountered to a depth of approximately 3 feet at Boring B-1. Fill could be encountered and extend to greater depths in other areas of the site where no borings were performed. Based on field and laboratory test data, it appears that some compactive effort was applied to the fill encountered at Boring B-1. However, no documentation regarding placement and compaction of the fill was provided for our review. New foundations and floor slabs should not be supported on or above existing fill. Existing fill present within the building footprint should be overexcavated during site grading and be replaced with engineered fill that has been placed and compacted as recommended in this report. Existing fill may be left in place below pavements provided it is observed, tested, and approved by

Terracon during construction.

Facilities | Environmental | Geotechnical | Materials 5

Based on the results of our sampling and testing, samples of the on-site clay soils recovered from our borings (both the existing fill soils and the underlying native soils) classified as “lean clay” (Unified Soil Classification System designation: CL). However, based on the results of Atterberg limits tests on selected samples, the existing fill soils are considered to be “lean to fat clay” soils, which are transitional material between low-plasticity “lean clay” and high-plasticity “fat clay” soils. Clay soils with a liquid limit of

45 or higher and/or a plasticity index of 23 or higher have the potential to shrink and swell with seasonal fluctuations in the soil moisture content. We recommend the floor slabs be supported on at least 24 inches of low volume change (LVC) material. In areas that are currently above or less than 2 feet below the planned bottom of floor slab level, any native clay soils that do not meet the liquid limit and plasticity index criteria for LVC material should be undercut to accommodate placement of LVC material. In areas where more than 2 feet of fill will be placed below the bottom-of-floor-slab level (including where the subgrade must be undercut to remove the existing fill soils), at least the upper 24 inches of new engineered fill should consist of LVC material. Placement of a layer of LVC material below floor slabs, as recommended in this report, will not eliminate all future subgrade volume change and resultant floor slab movements. However, use of an LVC zone should reduce the potential for subgrade volume change. Details regarding the LVC zone are provided in Earthwork.

This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and at least minor cracking in the structure could still occur. The severity of cracking and other cosmetic damage caused by movement of the floor slabs will probably increase if any modification of the site results in excessive wetting or drying of the expansive soils.

Eliminating the risk of movement and cosmetic distress may not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction. We would be pleased to discuss other construction alternatives with you upon request.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration Results), engineering analyses, and our current understanding of the proposed project. The General Comments section provides an understanding of the report limitations.

Earthwork

Site preparation, excavation, subgrade preparation, and placement of engineered fill should follow the recommendations presented in this section. The recommendations presented for design and construction of earth-supported elements including foundations, slabs, and pavements are contingent upon the recommendations outlined in this section being followed. We recommend earthwork on this project be observed and evaluated by Terracon. The evaluation of earthwork should include observation and

Facilities | Environmental | Geotechnical | Materials 6 testing of subgrade preparation, engineered fill, foundation bearing soils, and other geotechnical conditions exposed during the construction of the project.

Demolition

The proposed building will be constructed within the footprint of the existing shed which will need to be demolished, as well as exterior sidewalks, pavements, and utilities. We recommend existing foundations, slabs, and utilities be removed from within the proposed building footprint and at least 5 feet beyond the outer edge of foundations.

For areas outside the proposed building footprints and foundation bearing zones, existing foundations, floor slabs, and utilities should be removed where they conflict with proposed utilities, retaining walls, and pavements. In such cases, existing foundations, floor slabs, and utilities should be removed to a depth of at least 2 feet below the affected utility or design pavement subgrade elevation.

Site Preparation

Vegetation, topsoil, and any loose, soft, or otherwise unsuitable soils present within the proposed construction areas should be stripped. The required removal depth will likely vary, and should be evaluated by a representative of the Geotechnical Engineer during site preparation. Organic soils removed during site preparation should not be used as fill beneath the proposed new building and pavement areas.

The soils within the planned building area should be further undercut as necessary to completely remove existing undocumented fill from the building footprint and to accommodate placement of the recommended 24-inch thick LVC layer below floor slabs.

The undercut areas should extend a minimum of 5 feet laterally outside the building wall lines. Undercutting to facilitate placement of the LVC layer would not be necessary in areas where more than 2 feet of fill will be placed to develop the floor slab subgrade level.

Following initial stripping and any necessary undercutting, the exposed soils should be proofrolled. A Terracon representative should observe the proofrolling. Proofrolling can be accomplished using a loaded tandem-axle dump truck with a gross weight of at least

20 tons, or similarly loaded equipment. Areas that display excessive deflection

(pumping) or rutting during proofroll operations should be improved by scarification/compaction or by removal and replacement with engineered fill.

Excavation

We anticipate that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. The bottom of excavations should be thoroughly

Facilities | Environmental | Geotechnical | Materials 7 cleaned of loose soils and disturbed materials prior to backfill placement and/or construction.

Subgrade Stabilization

Due to the presence of soils with relatively high moisture content, some means of subgrade stabilization may be required to facilitate construction, especially if wet soils are encountered during site preparation or if the subgrade becomes saturated by precipitation during site preparation/earthwork operations.

In general (weather permitting), scarifying, drying, and compacting the exposed subgrades is expected to be the most economical means of improving these soils prior to placing new fill. However, this option is typically less effective where soft/wet soils are more than about one foot thick. Alternatives for subgrade stabilization could include undercutting unsuitable (wet, low strength, and/or disturbed) soils followed by the addition of crushed stone aggregate (typically on the order of 12 to 18 inches thick) to improve subgrade stability. The need for stabilization, and the most appropriate type of stabilization, will be dependent upon soil, groundwater, and weather conditions at the time of construction. The proposed grading plan, the construction schedule, and construction methods will also affect the selection of stabilization method. Terracon should be retained during construction to help provide recommendations as needed.

Fill Material Types

Fill required to achieve design grade should be classified as structural fill and general fill.

Structural fill (also referred to as engineered fill) is material used below, or within 10 feet of structures, pavements, or constructed slopes. General fill is material used to achieve grade outside of these areas.

Reuse of On-Site Soil: Excavated on-site soil may be selectively reused as fill provided the material meets the requirements outlined below and is properly compacted per the requirements in this report.

Material property requirements for on-site soil for use as general fill and engineered fill are noted in the table below:

Facilities | Environmental | Geotechnical | Materials 8

Fill Type

USCS

Classification Acceptable Location for Placement

Existing Fill

CL

(LL of 45 or greater or PI of

23 or greater)

Pavement areas and at depths greater than

24 inches below building finished grade

Existing fill should be observed, tested, and approved by Terracon.

Organics, rock/rubble fragments larger than 3 inches, debris, or other unsuitable materials should be removed prior to re-use of the existing fill in engineered fill sections.

Native Lean Clays

(LL<45 and PI<23)

CL

All locations and elevations, except where free-draining material is required

Imported Fill Materials: Imported fill materials should meet the following material property requirements. Regardless of its source, compacted fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

Fill Type

USCS

Classification Acceptable Location for Placement

Low Volume Change

(LVC) material

GM

or

CL (LL<45 and

PI<23)

All locations and elevations, except where free-draining material is required

Free Draining Granular

GW, GP,

SW, SP

Less than 5% passing No. 200 sieve

1. Engineered fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

2. MoDOT Type 5 or an approved alternate gradation of crushed limestone aggregate

3. Granular materials with less than 5 percent fines (material passing the #200 sieve), such as ASTM C33 Size No. 57 aggregate or an approved alternate gradation.

Fill Placement and Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Facilities | Environmental | Geotechnical | Materials 9

Item Structural Fill General Fill

Maximum Lift

Thickness

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

4 to 6 inches in loose thickness when hand-guided equipment (i.e., a jumping jack or plate compactor) is used

Same as structural fill

Minimum

Compaction

Requirements 1,2,3

95% of max. below and above foundations, below floor slabs, and below pavements 92% of max.

Water Content

Range

Low plasticity cohesive: -2% to +3% of optimum

High plasticity cohesive: 0 to +4% of optimum

Granular: -3% to +3% of optimum

As required to achieve min.

compaction requirements

1. Maximum density and optimum water content as determined by the standard

Proctor test (ASTM D 698).

2. High plasticity cohesive fill should not be compacted to more than 100% of standard Proctor maximum dry density.

3. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least

70% relative density (ASTM D 4253 and D 4254). Materials not amenable to density testing should be placed and compacted to a stable condition observed by the Geotechnical Engineer or representative.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench excavation should not be conducted below a downward 1:1 projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

On-site materials are considered suitable for backfill of utility and pipe trenches from 1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances.

Facilities | Environmental | Geotechnical | Materials 10

Trench backfills should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

Utility trenches are a common source of water infiltration and migration. Utili ty trenches that penetrate beneath the building should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the building. Each trench should be provided with an effective trench plug that extends at least 5 feet from the face of the building exterior. The plug material should consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If clay is used to construct the trench plug, the clay should be placed and compacted in accordance with the water content and compaction recommendations for structural fill provided in this report.

Grading and Drainage

The site should be graded to provide effective drainage away from the building during and after construction, and these conditions should be maintained throughout the life of the structure. Accumulation of water adjacent to the structure could contribute to significant moisture increases in the subgrade soils and subsequent softening/settlement or expansion/heave, which could result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks.

After building construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Terracon should be retained during the construction phase of the project to observe earthwork and to perform necessary tests and observations during subgrade preparation, proofrolling, placement and compaction of engineered fill, backfilling of excavations into completed subgrades, and just prior to construction of foundations, slabs, and pavements.

Care should be taken to avoid disturbance of prepared subgrades. Unstable subgrade conditions can develop during general construction operations, particularly if the soils

Facilities | Environmental | Geotechnical | Materials 11 are wetted and/or subjected to repetitive construction traffic. If unstable subgrade conditions develop, stabilization measures will need to be employed. Construction traffic over the completed subgrade should be avoided to the extent practical. If the subgrade becomes frozen, desiccated, saturated, or disturbed, the affected materials should be removed or these materials should be scarified, moisture conditioned, and compacted prior to floor slab construction.

Based on conditions encountered in the borings, significant seepage is generally not expected in excavations for this project (e.g., for footing construction and utility installation). If seepage is encountered in excavations during construction, the contractor is responsible for designing, implementing, and maintaining appropriate dewatering methods to control seepage and facilitate construction. In our experience, dewatering of excavations in clay soils can typically be accomplished using sump pits and pumps.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part

1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local, state, and federal safety regulations. The contractor should be aware that slope height, slope inclination, and excavation depth should in no instance exceed those specified by these safety regulations. Flatter slopes than those dictated by these regulations may be required depending upon the soil conditions encountered and other external factors. These regulations are strictly enforced and if they are not followed, the owner, contractor, and/or earthwork and utility subcontractor could be liable and subject to substantial penalties. Under no circumstances should the information provided in this report be interpreted to mean that Terracon is responsible for construction site safety or the contractor’s activities. Construction site safety is the sole responsibility of the contractor who shall also be solely responsible for the means, methods, and sequencing of the construction operations.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content.

In areas of foundation excavations, the bearing subgrade should be evaluated by the

Geotechnical Engineer. If unanticipated conditions are observed, the Geotechnical

Engineer should prescribe mitigation options.

Facilities | Environmental | Geotechnical | Materials 12

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

Shallow Foundations

Based on the conditions encountered at the borings, and provided our recommendation for removal/replacement of the existing fill materials are followed, the building can be supported on shallow footing foundations that bear on medium stiff to stiff, native clay soils and/or engineered fill.

Shallow Foundation Design Parameters

Item Description

Maximum Net Allowable Bearing

Pressure 1, 2, 3

2,000 psf

Minimum Foundation Dimensions Per IBC 1809.7

Minimum Embedment below

Finished Grade

30 inches

Estimated Total Settlement from

Structural Loads

On the order of 1 inch

Estimated Differential Settlement 2, 5

About 1/2 to 2/3 of total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation.

2. Values provided are for maximum loads noted in Project Description. Additional geotechnical consultation will be necessary if higher loads are anticipated.

3. Unsuitable or soft soils should be overexcavated and replaced per the recommendations presented in Earthwork.

4. Embedment necessary to minimize the effects of frost and/or seasonal water content variations

5. Differential settlements are noted for equivalent-loaded foundations and bearing elevation as measured over a span of 50 feet.

Foundation Construction Considerations

The base of all foundation excavations should be free of water and loose soil prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. If the soils at the bearing level become excessively dry, disturbed, Facilities | Environmental | Geotechnical | Materials 13 saturated, or frozen, the affected soil should be removed prior to placing concrete. If the excavations must remain open overnight or for an extended period of time, placement of a lean concrete mud-mat over the bearing soils should be considered.

The bearing materials at the base of each footing excavation should be evaluated by a representative of the Geotechnical Engineer. If unsuitable bearing materials are observed, the excavation should be extended deeper to suitable soils. The footings could bear directly on suitable soils at the lower level or on lean concrete backfill as shown on the following figure.

The footings could also bear on properly compacted structural fill extending down to suitable soils as shown in the following figure. Overexcavation for compacted structural fill placement below footings should extend laterally beyond all edges of the footings at least 8 inches per foot of overexcavation depth below footing elevation. The overexcavation should then be backfilled up to the footing base elevation with well graded granular material (e.g., MoDOT Type 5 aggregate or an approved alternate gradation) placed and compacted as recommended in the Earthwork section.

Facilities | Environmental | Geotechnical | Materials 14

Floor Slabs

Design parameters for floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to positive drainage away from the structure and positive drainage of the aggregate base beneath the floor slab.

Floor Slab Design Parameters

Item Description

Floor Slab

Support1 At least 24 inches of low volume change (LVC) material

Granular Leveling

Course Layer

Thickness 2

4 inches (minimum)

Estimated Modulus of Subgrade

Reaction 3

100 pounds per square inch per inch (psi/in) for point loads

1. Floor slabs should be structurally independent of building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation.

2. Well graded crushed sone (e.g., MoDOT Type 5) or open-graded crushed stone

(e.g., ASTM C33, Size No. 57 aggregate) can be used as the leveling course.

3. These granular materials can be considered part of the LVC zone.

4. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in Earthwork, and the floor slab support as noted in this table. It is provided for point loads. For large area loads the modulus of subgrade reaction would be lower.

The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, when the project includes humidity-controlled areas, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

Joints should be placed in slabs at regular intervals as recommended by ACI to help control the locations of cracks. Joints or any cracks that develop in the floor slab should be sealed with a waterproof, non-extruding compressible compound.

If floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates differential movement between the

Facilities | Environmental | Geotechnical | Materials 15 walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks beyond the length of the structural dowels. The Structural Engineer should account for potential differential settlement through use of sufficient control joints, appropriate reinforcing or other means.

Floor Slab Construction Considerations

The subgrade should be maintained within the moisture content range recommended for engineered fill until the floor slab is constructed. If the subgrade becomes desiccated prior to construction of the floor slab, the affected material should be removed or the materials should be scarified, moistened, and compacted. Upon completion of grading operations in the building area, care should be taken to maintain the subgrade within the moisture content and density ranges recommended for engineered fill prior to construction of the building floor slab.

On most project sites, the site grading is generally accomplished early in the construction phase. However, as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, rainfall etc. As a result, the floor slab subgrade soils may not be suitable for placement of the granular course and/or concrete at the time of building construction, and corrective action may be required.

The Geotechnical Engineer should observe the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

Lateral Earth Pressures

Lateral Earth Pressure Design Parameters

Structures with unbalanced backfill levels on opposite sides (such as the planned retaining wall) should be designed for earth pressures at least equal to values indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction, methods and degree of compaction, and the strength of the materials being restrained. Two wall restraint conditions are shown in the diagram below. Active earth pressure is commonly used for design of free-standing cantilever retaining walls where wall movement is acceptable.

The “at-rest” condition assumes no wall movement and is commonly used for design of basement walls, loading dock walls, or other walls restrained at the top. The recommended design lateral earth pressures do not include a factor of safety. The drained parameters do not provide for possible hydrostatic pressure on the walls.

Facilities | Environmental | Geotechnical | Materials 16

Lateral Earth Pressure Design Parameters

Earth

Pressure

Condition 1

Coefficient for

Backfill Type 2,3

Surcharge

Pressure 4 p1 (psf)

Equivalent Fluid Unit Weight

(pcf) 2,5

Drained 5 Undrained 5

Active (Ka) Granular - 0.3

Clay - 0.42

(0.31)S

(0.42)S

At-Rest (Ko) Granular - 0.47

Fine Grained - 0.58

(0.47)S

(0.58)S

Passive (Kp) Granular - 3.3

Clay - 2.4

1. For active earth pressure, wall must rotate about base, with top lateral movements 0.002 H to 0.004 H, where H is wall height. For passive earth pressure, wall must move horizontally to mobilize resistance.

2. Uniform, horizontal backfill, with a maximum unit weight of 120 pcf for clay soils and 130 pcf for granular soils.

3. Granular material backfill phi = 32 degrees (minimum); Clay soil phi = 24 degrees (minimum)

4. Uniform surcharge, where S is surcharge pressure.

5. Loading from heavy compaction equipment is not included.

6. To achieve “Drained” conditions, follow guidelines in Subsurface Drainage for

Below-Grade Walls below. “Undrained” conditions are recommended when drainage behind walls is not incorporated into the design.

Backfill placed against structures should consist of granular soils or low plasticity cohesive soils. For the granular values to be valid, the granular backfill must extend out and up from the base of the wall at an angle of at least 45 degrees from vertical for the active and at-rest

Facilities | Environmental | Geotechnical | Materials 17 cases, and at an angle of 60 degrees from vertical for the passive case. To calculate the resistance to sliding, a value of 0.3 should be used as the ultimate coefficient of friction where the footing bears on native clay soils or engineered fill.

Footings, floor slabs, or other loads bearing on backfill behind walls may have a significant influence on the lateral earth pressure. Placing footings within wall backfill and in the zone of active soil influence on the wall should be avoided unless structural analyses indicate the wall can safely withstand the increased pressure.

The lateral earth pressure recommendations given in this section are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever or gravity type concrete walls. These recommendations are not applicable to the design of modular block - geogrid reinforced backfill walls (also termed MSE walls). Recommendations covering these types of wall systems are beyond the scope of services for this assignment. However, we would be pleased to develop a proposal for evaluation and design of such wall systems upon request.

Subsurface Drainage for Below-Grade Walls

A perforated rigid plastic drain line installed behind the base of walls that extend below adjacent grade is recommended to prevent hydrostatic loading on the walls. The invert of a drain line around a below-grade building area or exterior retaining wall should be placed near foundation bearing level. The drain line should be sloped to provide positive gravity drainage to daylight or to a sump pit and pump. The drain line should be surrounded by clean, free-draining granular material having less than 5% passing the

No. 200 sieve, such as No. 57 aggregate. The free-draining aggregate should be encapsulated in a filter fabric. The granular fill should extend to within 2 feet of final grade, where it should be capped with compacted cohesive fill to reduce infiltration of surface water into the drain system.

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As an alternative to free-draining granular fill, a prefabricated drainage structure may be used. A prefabricated drainage structure is a plastic drainage core or mesh which is covered with filter fabric to prevent soil intrusion and is fastened to the wall prior to placing backfill.

Pavements

Pavement Subgrade Preparation

Pavement subgrades are expected to consist of on-site native clay soils, newly placed engineered fill, and/or tested/approved existing fill. The pavement subgrades should be proofrolled as recommended in Earthwork. If soft or otherwise unsuitable areas are observed, additional over-excavation and replacement will be needed.

Grading and paving are commonly performed by separate contractors and there is often a time lapse between the end of grading operations and the commencement of paving.

Subgrades prepared early in the construction process may become disturbed by construction traffic. Non-uniform subgrades often result in poor pavement performance and local failures relatively soon after pavements are constructed. Depending on the paving equipment used by the contractor, measures may be required to improve subgrade strength to greater depths for support of heavily loaded concrete/asphalt trucks.

We recommend the moisture content and density of the subgrade be evaluated and the pavement subgrades be proofrolled (using a loaded tandem-axle dump truck with a minimum gross weight of 20 tons or similarly loaded rubber-tire equipment) within two days prior to commencement of actual paving operations. Areas not in compliance with the required ranges of moisture or density should be scarified, moisture conditioned, and compacted. Particular attention should be paid to high traffic areas that were rutted and disturbed earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions are located should be repaired by removing and replacing the materials with properly compacted fills. The subgrade should be in its finished form at the time of the final review.

Pavement Section Thicknesses

Pavement thickness depends upon many factors including but not limited to:

■ applied wheel/axle loads and number of repetitions

■ subgrade and pavement material characteristics

■ climate conditions

■ site and pavement drainage

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Specific information regarding anticipated vehicle types, axle loads, and traffic volumes was not provided at the time of this report. The “Parking Lots” pavement section considers 4-tire, 2-axle personal vehicle traffic only (cars, vans, pickups, and SUVs).

The “Drives” pavement section considers personal vehicle traffic and a maximum of ten delivery trucks/trash collection trucks per week. Our recommendations for full depth asphaltic cement concrete (ACC) pavement, ACC pavement over aggregate base, and portland cement concrete (PCC) pavement sections are outlined in the following table.

Opinions of Minimum Pavement Thickness

Pavement Type Parking Lots Drives

Full Depth ACC 2 inches ACC surface

4 inches ACC base

2 inches ACC surface

6 inches ACC base

Aggregate Base

2 inches ACC surface

2 inches ACC base

6 inches aggregate base

(MoDOT Type 5 or similar)

2 inches ACC surface

4 inches ACC base

6 inches aggregate base

(MoDOT Type 5 or similar)

PCC

5 inches PCC

4 inches open graded rock

(ASTM C33 Size No. 57 aggregate or similar)

6 inches PCC

4 inches open graded rock

(ASTM C33 Size No. 57 aggregate or similar)

1. For trash container pads, we recommend a PCC pavement section be used consisting of 7 inches (minimum) of PCC over 4 inches (minimum) of open graded rock (ASTM C33 Size No. 57 aggregate or similar) on a compacted soil subgrade. The trash container pad should be large enough to support the container and the tipping axle of the collection truck.

PCC pavements will perform better than ACC in areas where short radius turning and braking are expected (i.e., entrance/exit aprons) due to better resistance to rutting and shoving. In addition, PCC pavement will perform better in areas subject to heavy static loads.

Construction traffic on the pavements was not considered in developing our opinions of minimum pavement thickness. If the pavements will be subject to construction equipment/vehicles, the pavement sections should be revised to consider the additional loading.

Pavements and subgrades will be subject to freeze-thaw cycles and seasonal fluctuations in moisture content. Pavement thickness design methods are intended to provide adequate thickness of structural materials over a particular subgrade such that wheel loads are reduced to a level that the subgrade can support. The subgrade support

Facilities | Environmental | Geotechnical | Materials 20 parameters for pavement thickness design do not account for shrink/swell movements of a subgrade constructed of expansive clay soils. Therefore, the pavement may be adequate from a structural standpoint, yet still experience cracking and deformation due to shrink/swell related movement of the subgrade.

The pavement sections provided above consider that the subgrade soils will not experience significant increases in moisture content. Paved areas should be sloped to provide rapid drainage of surface water and to drain water away from the pavement edges. Pavements should be designed so water does not accumulate on or adjacent to the pavement, since this could saturate and soften the subgrade soils and subsequently accelerate pavement deterioration.

Periodic maintenance of the pavements will be required. Cracks should be sealed, and areas exhibiting distress should be repaired promptly to help prevent further deterioration. Even with periodic maintenance, some movement and related cracking may still occur, and repairs may be required.

Pavement Drainage

Pavements should be sloped to provide rapid drainage of surface water. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. In addition, the pavement subgrade should be graded to provide positive drainage within the granular base section. Appropriate sub-drainage or connection to a suitable daylight outlet should be provided to remove water from the granular subbase.

Pavement Maintenance

The pavement sections represent minimum recommended thicknesses, and periodic maintenance and repairs should be anticipated. Preventive maintenance should be planned and provided for through an on-going pavement management program.

Maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment. Pavement care consists of both localized (e.g., crack sealing, joint sealing, and patching) and global maintenance (e.g., surface sealing).

Additional engineering consultation is recommended to determine the type and extent of a cost-effective program. Even with periodic maintenance, some movements and related cracking may still occur, and repairs may be required.

Pavement performance is affected by the pavement’s surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements:

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■ Final grade adjacent to paved areas should slope down from the edges at a minimum 2%.

■ Subgrade and pavement surfaces should have a minimum 2% slope to promote proper surface drainage.

■ Install pavement drainage systems surrounding areas anticipated for frequent wetting.

■ Install joint sealant and seal cracks immediately.

■ Seal all landscaped areas in or adjacent to pavements to reduce moisture migration to subgrade soils.

■ Place compacted, low permeability backfill against the exterior side of curb and gutter.

■ Place curb, gutter and/or sidewalk directly on clay subgrade soils rather than on unbound granular base course materials.

General Comments

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration.

Variations will occur between boring 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 as the

Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Support of pavements above existing fill is discussed in this report. Even with the construction observation/testing recommended in this report, the owner must accept the risk that unsuitable materials within or buried by the fill will not be discovered. This may result in larger than normal settlement and damage to pavements supported above existing fill, requiring additional maintenance. This risk cannot be eliminated without removing the existing fill from below the pavement areas, but it can be reduced by thorough observation and testing as discussed herein.

Our…