Amd0001_Attch4_Terracon Soils Report Requirement of Ove....pdf

RFI. NO:

Project #0422015

Tel: 719-651-8228 email: rernest@gchconstruction.com

Submitted By:

Rocky Ernest

Discipline

Structural

Answer:

Date:Submitted To: Spec Section

Mike Bell

Terracon Soils Report Requirement of Over Excavation and Structural Fill

Terracon Soils Report No. 24145008 & S0.00, S1.00, S2.00

None

Yes

Yes

GCH RFI 003 Attachment A

CVAMC

03/31/16

0003Request For Information

MRI Site Prep

Answered By: Date:

Schedule Impact?Answer Company:

Subject:

Referenced Drawing # and/or Details

There are multiple details in the drawings that state to "Prepare Footing Subgrade According to the Geotechnical Report".

During the Question and Answer session of the Bidding Process Question #16 in Amendment 5 requested the soils report. The response stated

"Geotechnical report was provided to the A/E for design purposes. The report will be provided to the successful offeror, if needed."

Upon receipt and review of Terracon Soils Report Dated on April 17th 2014 provided after award it was found; That spread footing and spot footings can bear on native silty to well graded sands or structural fill extending to suitable native soils. This soils reports states this material is located at approx. 7' the surface grade. On Sheet S0.00 Notes 1-3 under Soil Conditions references the Terracon report for requirements related to the construction of the slab & footings on granular engineered fill material.

Without the soils report there is no way to determine if over excavation was required or requirement of import of Engineered Fill. Attachment A shows the footings that are affected.

Please advise if over excavation and structural fill is required or if the design allows for footings to be installed on native soils.

Date Required:

Attachments?

04/07/16

Question:

Proposed Solution:

Cost Impact

Albertson Engineering Inc. (AEI) Response: The structural design was based upon the geotechnical recommendations given in the geotechnical report prepared by Terracon. Terracon is the entity who needs to respond to any questions regarding geotechnical issues. The recommendations given in their report contain specific recommendations regarding the need for Terracon to observe the excavations in order to determine if native soils are suitable, or if engineered fill is required, as well as many other parameters related to excavation and subgrade preparation requirements. See attached section 4.0 from Terracon's report for specific details on subgrade preparation and requirements (this is only an excerpt and entire document needs to be followed). For the recommendations to be valid, all of the recommendations in terms of subgrade excavation, observation, testing, and subgrade preparation given in the geotechnical report need to be followed without exception.

Michael Albertson, PE (AEI) 4-29-16

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Kyle Text Box Engineer Fill Required below spot footings

Kyle Text Box Engineer Fill Required below continuous footings

Kyle Text Box Limits of Sloping of excavation

Rocky Typewritten Text GCH RFI 003 Attachment A

Geotechnical Engineering Report Proposed VA MRI Addition Cheyenne, Wyoming April 17, 2014 Terracon Project No. 24145008

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4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

4.1 Geotechnical Considerations

Terracon recommends removing all topsoil, vegetation, root zones, debris or fill within the building addition and parking area prior to construction. This excavation should be observed by Terracon’s geotechnical engineer. In our opinion, shallow spread footings and continuous wall footings can be used to support the proposed structure. Suitable bearing soils should consist of native silty sand to well-graded sand, or imported Structural Fill extending to suitable native sand soils. The building foundations should not be supported on the clayey sand or lean clay soils in the upper approximate 3.5 to 4.5 feet.

Terracon based our bearing capacity and settlement analysis on a lightly-loaded, single story structure with slab-on-grade flooring. The analysis has been conducted assuming continuous strip foundations founded on native silty to well-graded sand at frost-depth elevation for the building perimeters. Interior support would be provided by isolated column footings similarly bearing on silty sand to well-graded sand or Structural Fill extending to native sands. For analysis purposes, an SPT N-value of 20 blows per foot has been assigned to the silty sand and well-graded sand and a maximum column loading of 50,000 pounds provided by the Structural Engineer was used. Based on these conditions and using an allowable bearing pressure of 3,000 psf, the design column footing size will be on the order of 4.5 feet.

For the foundation walls, 2,500 pounds per lineal foot was provided to us for design purposes by the Structural Engineer. A minimum 1.5 foot wide continuous footing designed for a 2,000 psf allowable bearing capacity is expected to experience total settlement of less than 1 inch.

Differential settlements should be on the order of one half the total settlements for both wall and column footings.

The native clayey sand and lean clay soils may be used to support the pavements for the new parking area, provided the exposed subgrade is prepared in accordance with the recommendations presented herein.

The excavation/sub-excavation base on the native sands should be prepared to minimize disturbance to the native materials. The use of a smooth bucket without teeth is recommended.

Compaction of the excavated base in accordance with Section 4.2.2 is recommended prior to any formwork or placement of Structural Fill or sub-excavated native sands.

4.2 Earthwork

4.2.1 Site Preparation

Site preparation should commence with stripping of vegetation, organic soils, root systems and any unsuitable materials (e.g., debris, desiccated soil, frozen soil, etc.) from the site surface

Responsive Resourceful Reliable 5 within planned new construction areas. Terracon personnel should evaluate the depth of removal of unsuitable materials during construction.

Structural Fill for foundation area soil replacement or site grade raising should be developed from reliable sources approved by our geotechnical engineer and should meet the gradation and composition requirements included in the following table:

Controlled Fill Type USCS Classification Acceptable Location for Placement

Structural Fill

GW, SW, SM

GW-GM, SW-SM

GP, SP

GP-GM, SP-SM

Screen or Sieve Size Percent Passing by Weight

3 inch 100

No. 4 30-80

No. 40 10-30

No. 200 15 maximum

On-Site Soils

SC, SM, SW-SM

On-site clayey, silty and well-graded sand soils are suitable for general foundation backfill above footing elevation, trench backfill above bedding and select zones, and for general site fill outside the footing influence zone provided that specific criteria herein are met.

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

2. The sand, gravel, and cobble-size particles comprising the Structural Fill must be hard, durable rock materials that will not degrade by moistening or under mechanical action of the compacting equipment; i.e. not shale or other clayey rock types.

3. Particle sizes larger than 3-inches are removed from trench and foundation backfill zones.

Soils exposed after stripping should be proof rolled. Proof rolling of exposed soils should be performed using a loaded tandem axle dump truck with a gross weight of at least 25 tons.

Subgrades identified to be yielding or unstable should be removed if they cannot be satisfactorily compacted in place. Following proof rolling and correction of identified deficiencies, the subgrade should be scarified to a depth of 8 inches, moisture conditioned, and compacted to the moisture content and density ranges recommended in this report.

Although the exposed subgrades may be relatively stable upon initial exposure, unstable subgrade conditions could develop during general construction operations, particularly if the soils are wetted and/or subjected to repetitive construction traffic. The exposed soil layers could be sensitive to construction disturbances. The use of remotely operated equipment, such as a tracked excavator, would be beneficial to perform cuts and reduce subgrade disturbance.

Should unstable subgrade conditions develop, stabilization measures will need to be employed.

Terracon should be contacted to discuss alternative stabilization measures.

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Disturbed and unstable subgrades should be improved before the aggregate base and floor slabs and pavements are placed. Improvement methods are influenced by schedule, weather, the size of disturbed area, and the nature of the disturbance. Improvement methods include, but are not limited to:

Scarification and Compaction – Soils can be scarified, moisture conditioned (i.e., dried or moistened), and compacted. The success of this procedure depends primarily upon favorable weather and sufficient time to manipulate the soils. Even with adequate time and favorable weather, stable subgrades may not be achieved if the thickness of the unstable material is greater than about 1 to 1½ feet.

Removal and Replacement with Granular Fill/Aggregate – Unstable subgrade soils can be removed and replaced with crushed stone, pit run gravel or crushed concrete. If the depth of instability extends more than 2 feet below grade, placement of geogrid reinforcement should be considered. Geogrid should ideally be installed after underground work, such as utility construction, is completed. Equipment should not be operated above the geogrid until one full lift of granular fill is placed above it. The maximum particle size of granular material placed over geogrid generally should not exceed 1½ inches. Gradation requirements for granular material provided by the geosynthetic product manufacturer should be verified prior to material purchase and delivery to the site.

Terracon should observe subgrade preparation and can provide further recommendations based on conditions encountered during construction.

4.2.2 Compaction Requirements

ITEM DESCRIPTION

Fill 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. jumping jack or plate compactor) is used

Compaction Requirements 1

Native Sand/Structural Fill for the Building Area 95% of the maximum Standard Proctor dry density (ASTM D 698) Site Fill/Backfill 95% of the maximum Standard Proctor dry density (ASTM D 698)

Pavement Subgrade 95% of the maximum Standard Proctor dry density

(ASTM D 698)

Moisture Content

Within the range of 3% below the optimum moisture content to 2% above optimum moisture content value as determined by the Standard Proctor test at the time of placement and compaction

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1. We recommend that all controlled 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 limits have not been met, the area represented by the test should be reworked and retested as required until the specified moisture and compaction requirements are achieved.

2. Specifically, moisture levels should be maintained low enough to allow for satisfactory compaction to be achieved without the material pumping under construction equipment traffic.

3. Compaction within 4 feet of foundation structures should be accomplished using hand-operated tamping equipment.

4.2.3 Grading, Drainage, and Landscaping

The site should be graded so surface water will drain away from prepared subgrades and excavations. Accumulations of water should be promptly removed to reduce the potential softening of prepared subgrades and bearing surfaces. During earthwork operations, exposed subgrades should be properly sloped to provide rapid drainage so that risks of saturation of the subgrades can be reduced. The soil types observed in the borings are easily eroded by surface water, so appropriate erosion control measures should be provided.

Removal of water that accumulates in relatively shallow excavations can typically be accomplished using sump pits and pumps. The contractor is responsible for employing appropriate dewatering methods to control seepage and facilitate construction.

Final grades should slope down and away from all sides of the completed structure to prevent ponding of water next to foundations. Gutters and downspouts that drain water a minimum of 10 feet beyond the footprint of the building are recommended. This can be accomplished through the use of downspout extensions or flexible pipes that are designed to attach to the end of the downspout. Flexible pipe should only be used if it is day-lighted in such a manner that it drains collected water.

4.2.4 Earthwork Construction Considerations

Temporary excavations will probably be required during grading operations and installation of utilities. Contractors, by their contract, are usually responsible for designing and constructing stable, temporary excavations and should shore, slope or bench the sides of the excavations as required, to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, state and federal safety regulations, including the current Occupational Safety and Health Administration (OSHA) Excavation and Trench Safety Standards.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of the grade-supported slabs and pavements. Construction traffic over the completed subgrade should be avoided to the extent practical.

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If the subgrade should become frozen, desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to grade-supported slab and pavement construction.

By conducting this exploration and site characterization, Terracon is in an advantageous and beneficial position to observe and evaluate conditions exposed during construction, compare these to the findings of the exploration and assist in providing remedial recommendations if variations are present. 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 controlled compacted fills; backfilling of excavations into the completed subgrade, and just prior to construction of building foundation, floor slab and pavement.

4.3 Conventional Shallow Foundations

Based on the materials encountered in the borings and our analyses, it is our opinion that the proposed building addition can be supported on continuous and spread footings bearing on either suitable native silty sand, well-graded sand or imported Structural Fill extending to these suitable soils.

The soils encountered in foundation excavations should be observed and tested by Terracon personnel. Design recommendations for spread footing foundations prepared in accordance with the recommendations in this report are presented in the following sections.

4.3.1 Conventional Shallow Foundation Design Recommendations

Description Value

Suitable bearing materials Spread and Continuous Footings

Medium dense, native, silty sand to well-graded sand or Structural Fill, Structural fill placed during mass grading

Net allowable bearing pressure 1 3,000 psf- Spread Footings 2,000 psf – Continuous Footings

Minimum dimensions Continuous footings: 18 inches Isolated column footings: 36 inches

Minimum embedment below finished grade for frost protection 2 36 inches

Estimated total settlement 3 1 inch or less

Estimated differential settlement 4 ¾ inches or less between columns ¾ inches or less over 40 feet along walls

Ultimate coefficient of sliding friction Native soils or compacted granular fill: 0.4

1. The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. Assumes any unsuitable materials, Responsive Resourceful Reliable 9 existing fill, where encountered, will be undercut and replaced with structural fill, and any loose sands will be recompacted in accordance with Section 4.2.2 .

2. For perimeter footings and footings beneath unheated areas

3. The foundation settlement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth of the footings, the thickness of Structural Fill, and the quality of the earthwork operations.

4. Frequent control joints in the structures and sufficiently flexible connections are recommended help to accommodate differential settlement.

4.3.2 Foundation Construction Considerations

Overexcavation for Structural Fill placement or native sand replacement below footings should extend laterally beyond all edges of the footings at least 8 inches per foot of overexcavation depth below footing base elevation. The overexcavation should then be backfilled to the footing base elevation with Structural Fill or native sand placed and compacted as recommended in Section 4.2.2 of this report. The overexcavation and backfill procedures are illustrated in the following figure.

The base of all foundation excavations should be free of water and loose soil prior to placing Structural Fill. Fill material should be placed soon after excavating to reduce bearing soil disturbance. Should the materials at bearing level become excessively dry, disturbed, or saturated, or frozen, the affected material should be removed prior to placing any additional material.

4.4 Seismic Considerations

Parameter Value Site Class - 2012 International Building Code 1 D 2

1. In accordance with the 2012 International Building Code, Section 1613.3.2 - Site Class Definitions.

Design Footing Level

Structural Fill or Native Sand

Note: Excavation in sketch is shown vertical for convenience.

Excavations should be sloped as necessary for safety.

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Parameter Value

2. The 2012 International Building Code (IBC) uses a site soil profile determination extending to a depth of 100 feet. The current scope requested does not include the 100 foot soil profile determination. The deepest boring extended to a maximum depth of approximately 15½ feet and this seismic site class definition considers that dense sand deposits continue below the maximum depth of the subsurface exploration.

4.5 Floor Slabs

4.5.1 Interior Floor Slab Design Recommendations

Item Description

Floor slab support 1, 2 Minimum of 24 inches of recompacted on-site soils or Structural Fail prepared according to section 4.2 Earthwork.

Aggregate base course 3 4 inches of free draining granular material.

Modulus of subgrade reaction (for point load conditions)

150 pounds per square inch per inch (psi/in) where 4 inches of granular materials are present below the floor slab.

1. Floor slabs and foundations support substantially different loads so foundations and floors often settle differently. The design should consider the potential for differential settlement of walls and floors.

2. We recommend subgrades comprised of cohesionless (sand) soils be maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become desiccated prior to construction of floor slabs the affected material should be removed or the materials scarified, moisture conditioned, and recompacted. Upon completion of grading operations in the building areas, care should be taken to maintain the recommended subgrade moisture content and density prior to construction of the building floor slabs.

3. Clean, well-graded to poorly-graded aggregate or sand containing less than 15% passing the U.S.

No. 200 sieve.

Where appropriate, saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual.

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

4.5.2 Exterior Slabs

The clayey sand, lean clay and silty sand soils on this site are considered frost susceptible, and small amounts of trapped water below exterior slabs exposed to freezing temperatures can be detrimental to the performance of the slabs. Exterior slabs should be expected to heave during the winter and early spring seasons. The amount of heave may be reduced by providing

Responsive Resourceful Reliable 11 surface drainage away from the building and slabs and toward the site storm drainage system.

Even with appropriate surface and subsurface drainage, some frost heave may still occur.

To minimize the effects of seasonal heave, entrances can be supported on stoops (structural concrete slabs supported on frost walls bearing on spread footings that extend to the frost depth) so that frost heave does not impact the functioning of doors. We recommend that the interior of the stoops be filled with compacted structural fill that is extended to approximately design slab subgrade. The backfill of the stoops that supports slabs should consist of low-frost susceptible fill that is hydraulically connected to a drain line that provides positive gravity drainage to a reliable outlet. Low-frost susceptible fill materials are typically free-draining crushed aggregate containing less than 10% passing the No. 200 sieve.

4.5.3 Floor Slab and Exterior Slab Construction Considerations On most project sites, grading for slab subgrade is accomplished relatively early in the construction phase, so the subgrade, which may be constructed weeks or months later, should be evaluated as the time for slab construction approaches. Particular attention should be given to high traffic areas that become rutted and disturbed, and to areas where backfilled trenches are located.

A Terracon representative should observe the floor slab subgrade prior to placement of the aggregate base and concrete. Where unstable or disturbed soils are identified, those areas should be undercut to expose stable material and backfilled with structural fill. All slab subgrade areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to placement of the aggregate base course and concrete.

Care will be necessary to avoid contaminating the granular (aggregate base course) layer located directly below the floor slab with soil prior to floor slab placement. We recommend the granular layer be placed only immediately prior to slab concrete placement.

4.6 Foundation Backfill/Lateral Earth Pressures

Reinforced concrete walls, such as will be constructed for the MRI pit with unbalanced backfill levels on opposite sides should be designed/checked using earth pressures at least equal to those indicated in the following table. Foundation backfill drainage should also be provided to reduce the potential for hydrostatic pressure against the building and pit walls.

Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained.

Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls

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EARTH PRESSURE COEFFICIENTS

Earth Pressure

Condition Coefficient For Backfill Type

Equivalent Fluid Density (pcf)

Surcharge Pressure, p1 (psf)

Earth Pressure, p2 (psf)

Active (Ka) Structural Fill - 0.26 Native Sand – 0.33

Lean Clay - 0.49

(0.26)S (0.33)S (0.49)S

(35)H (40)H (60)H

At-Rest (Ko) Structural Fill - 0.41 Native Sand – 0.50

Lean Clay - 0.66

(0.41)S (0.50)S (0.66)S

(55)H (60)H (80)H

Passive (Kp) Structural Fill – 3.85 Native Sand – 3.00 Lean Clay – 2.00

Applicable conditions to the above include:

For active earth pressure, wall must rotate about base, with top lateral movements of about 0.002 H to 0.004 H, where H is wall height

For passive earth pressure to develop, wall must move horizontally to mobilize resistance.

Uniform surcharge, where S is surcharge pressure Backfill weight a maximum of 135 pcf for Structural Fill and 120 pcf for onsite sand and lean clay soils

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Ultimate coefficients of friction for the lean clay = 0.40, sand =0.58 and for the Structural Fill = 0.70

Horizontal backfill, compacted per Section 4.2. Compaction within 4 feet of wall to be conducted using hand operated tamping equipment only

Loading from heavy compaction equipment not included No hydrostatic pressures acting on wall; underdrainage provided as recommended Parameters given are ultimate values without safety factors included Ignore passive pressure in frost zone Seismic thrust is additive per IBC recommendations

For the Structural Fill values in the foregoing table to be valid, the Structural Fill must extend out from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively. If onsite soils are to be used as perimeter foundation backfill, then the backfill zone will be of mixed materials/texture and should be considered as “Lean Clay” in the table above for purpose of earth pressure calculation. A qualified geotechnical engineer should approve the use of all onsite soils for backfill purposes.

4.7 Pavements

4.7.1 Flexible Pavement Design Parameters

The anticipated traffic loading used in our analysis was 22,000 18-kip equivalent single axle loads (ESALs). This loading was obtained from the original geotechnical engineering report completed for the adjacent clinic building, dated June 3, 2009. A design life of 20 years has been requested. Should there be any changes in the assumed traffic loading which includes 2% delivery trucks, our office should be notified to review the design and make supplementary recommendations. The design also assumes that proper subgrade drainage is provided.

Based on our past CBR testing experience and engineering text references for soils similar to those encountered in the upper two feet of this site, we used the following input parameters for the design of the pavement. The controlling, lowest shear strength subgrade soil is the sandy lean clay encountered in Boring 3 at the ground surface.

Input Parameter Asphalt Pavement

CBR (flexible pavement design) 2 The Resilient Modulus – Mr (flexible pavement design) 3,000 psi

Reliability 95%

Initial Serviceability 4.2

Terminal Serviceability 2.0

Standard Deviation 0.35

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Input Parameter Asphalt Pavement

Drainage coefficients m2 = 1.3, m3 = 1.2

Structural Coefficients a1 = 0.41, a2 = 0.14

4.7.2 Flexible Pavement Recommendations

The following resource was utilized to develop recommendations for flexible asphaltic concrete pavement sections for the proposed building: The 1993 AASHTO “Guide for Design of Pavement Structures”.

Pavement thickness recommendations are based on the subsurface conditions encountered at the borings, general characterization of the subgrade, and our experience on similar projects, and consider that all materials are placed on a subgrade prepared and evaluated as recommended in this report. Periodic maintenance will extend the service life of the pavements and should include patching and repair of deteriorated areas, crack sealing, and surface sealing. If higher truck traffic volumes and/or heavier trucks are expected, thicker pavement sections may be required.

Presented below is our recommended minimum thickness of asphaltic concrete pavement for the traffic loading anticipated on the site.

Pavement Section Components

Crushed Aggregate Base Course Thickness (inches)

Asphalt Surfacing Thickness (inches)

6 3

This section is based on the design traffic operating on the entire section of gravel and asphalt surface. Construction use of the section or partial components thereof for support of excessive or channelized wheel loads may lead to rutting or premature pavement failure. Properly compacted materials, and prudent selection of compaction, hauling, and construction equipment will be necessary to preserve the integrity of the subgrade and gravel base course components during construction.

In areas of anticipated concentrated loads (e.g.,dumpster pads) we recommend constructing reinforced portland cement concrete (PCC) pavements with a minimum thickness of 6 inches over 4 inches of base course.

All of the paving materials and pavement construction should meet the requirements of the City of Cheyenne Construction Standards and Specifications. In addition, mix designs should be submitted prior to construction to verify their adequacy. The aggregate base course should consist of a blend of sand and gravel which meets the specifications for Grading W. The aggregate base course should be compacted to a minimum of 95% of ASTM D698.

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Asphalt concrete should be composed of a mixture of aggregate, filler and additives, if required, and approved bituminous material. The asphalt concrete should conform to approved mix designs stating the Marshall properties, optimum asphalt content, job mix formula and recommended mixing and placing temperatures. Aggregate used in plant-mixed asphalt concrete should meet particular gradations. Material meeting City of Cheyenne ¾” or ½” nominal maximum size specifications is recommended for asphalt concrete. The asphalt should be supplemented with 1½% hydrated lime if the aggregate is known to have stripping issues. Mix designs should be submitted prior to construction to verify their adequacy. Asphalt material should be compacted to a minimum of 92% Maximum Theoretical Specific Gravity.

4.7.3 Pavement Drainage

Pavements should be sloped to provide rapid drainage of surface water. Water should not be allowed to pond on or adjacent to the pavements, since this could saturate the subgrade and contribute to premature pavement deterioration. Periodic maintenance of the pavements will be required. All cracks should be sealed, and areas exhibiting distress should be repaired promptly to help prevent further deterioration. Even with periodic maintenance, some movements and related cracking may still occur and repairs will be required.

4.7.4 Pavement Construction Considerations

Lean clay and clayey sand soils generally provide poor to fair pavement support and are susceptible to rutting and pumping under repeated heavy vehicle traffic (both during construction and under inadequate pavement sections). A Terracon representative should observe proof rolling of the pavement subgrade, as described in section 4.2.1 Site Preparation, prior to paving operations to help delineate soft or disturbed areas, and the pavement subgrade should be prepared in accordance with the recommendations presented in section 4.2 Earthwork.

Construction scheduling often involves grading and paving by separate contractors and can involve a time lapse between the end of grading operations and the commencement of paving.

Disturbance, desiccation, or wetting of the subgrade soils between grading and paving can result in deterioration of the previously completed subgrade. A non-uniform subgrade can result in poor pavement performance and local failures relatively soon after pavements are constructed.

If a significant precipitation event occurs after the evaluation or if the surface becomes disturbed, the subgrade should be reviewed by a Terracon representative immediately prior to paving. The subgrade should be in its finished form at the time of the final review.

5.0 GENERAL COMMENTS

Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations

Responsive Resourceful Reliable 16 in the design and specifications. Terracon also should be retained to provide observation and testing services during grading, excavation, foundation construction, subgrade preparation, and other earth-related construction phases of the project.

The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, 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. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided.

The scope of services for this project does not include either specifically or by implication any environmental or biological assessment of the site or identification or prevention of pollutants, hazardous materials or conditions beyond the limited field screening performed. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing.