Bid Docs - Reports - Phase 1 Expansion Geotechnical Report.pdf

REPORT C OVER PAGE

Geotechnical Engineering Report

Ft. Logan National Cemetery - Phase 1 Expansion

4400 West Kenyon Avenue

Denver, Colorado

December 24, 2020

Terracon Project No. 25205232

Prepared for:

Calibre Engineering, Inc.

Littleton, Colorado

Prepared by:

Terracon Consultants, Inc.

Wheat Ridge, Colorado

Terracon Consultants, Inc. 10625 W. I -70 Frontage Rd N, Ste 3 Wheat Ridge, Colorado 80033

P (303)423-3300 F (303) 423-3353 terracon.com

REPORT C OVER LETTER TO SIGN

Calibre Engineering, Inc.

8201 Southpark Lane, Suite 200

Littleton, Colorado 80210

Attn: Mr. John Strandberg

P: 303.339.5409

E: jstrandberg@calibre-engineering.com

Re: Geotechnical Engineering Report

Ft. Logan National Cemetery - Phase 1 Expansion

4400 West Kenyon Avenue

Denver, Colorado

Terracon Project No. 25205232

Mr. Strandberg:

We have completed the Geotechnical Engineering services for the above referenced project. This study was performed in general accordance with Exhibit A – Scope of Services and Fee in the

Service Authorization, dated August 11, 2020. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations and pavements for the proposed 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 Consultants, Inc.

Preston S. Rich, E.I. Scott B. Myers, P.E.

Geotechnical Staff Engineer Regional Senior Consultant

Ft. Logan National Cemetery - Phase 1 Expansion ■ Denver, Colorado

December 24, 2020 ■ Terracon Project No. 25205232

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REPORT TOPICS

REPORT SUMMARY --------------------------------------------------------------------------------------- I INTRODUCTION -------------------------------------------------------------------------------------------- 1

SITE CONDITIONS ----------------------------------------------------------------------------------------- 1 PROJECT DESCRIPTION ------------------------------------------------------------------------------- 3 GEOTECHNICAL CHARACTERIZATION ----------------------------------------------------------- 4

Groundwater Conditions ---------------------------------------------------------------------------------------------- 5

GEOTECHNICAL OVERVIEW -------------------------------------------------------------------------- 7

Existing Fill Materials -------------------------------------------------------------------------------------------------- 8 Expansive Soils and Bedrock ---------------------------------------------------------------------------------------- 9 Loose and Soft Soils --------------------------------------------------------------------------------------------------- 9 Shoring -------------------------------------------------------------------------------------------------------------------- 9 Existing Structures ---------------------------------------------------------------------------------------------------- 10 Temporary Dewatering ---------------------------------------------------------------------------------------------- 10

EARTHWORK ----------------------------------------------------------------------------------------------10

Site Preparation ------------------------------------------------------------------------------------------------------- 11 Material Types --------------------------------------------------------------------------------------------------------- 11 Compaction Requirements ----------------------------------------------------------------------------------------- 13 Excavation -------------------------------------------------------------------------------------------------------------- 13 Grading and Drainage ----------------------------------------------------------------------------------------------- 14 Earthwork Construction Considerations ------------------------------------------------------------------------- 15

UTILITY RECOMMENDATIONS ----------------------------------------------------------------------15

CORROSIVITY ---------------------------------------------------------------------------------------------16 SOIL NUTRIENTS -----------------------------------------------------------------------------------------18 COLUMBARIA AND PUMP STATION --------------------------------------------------------------18

Spread Footing Foundation Recommendations --------------------------------------------------------------- 18

CULVERT DESIGN RECOMMENDATIONS -------------------------------------------------------20

PRE-PLACED CRYPTS GEOTECHNICAL CONSIDERATIONS ----------------------------21

IN GROUND CREMAINS GEOTECHNICAL CONSIDERATIONS ---------------------------22

SEISMIC CONSIDERATIONS --------------------------------------------------------------------------22

EXTERIOR FLATWORK ---------------------------------------------------------------------------------22 BELOW-GRADE STRUCTURES ----------------------------------------------------------------------23 LATERAL EARTH PRESSURES ---------------------------------------------------------------------23

PAVEMENTS -----------------------------------------------------------------------------------------------25

Design Traffic ---------------------------------------------------------------------------------------------------------- 25 Subgrade Soils -------------------------------------------------------------------------------------------------------- 25 Swell Potential and Subgrade Treatment Requirements ---------------------------------------------------- 25 Pavement Thickness Design --------------------------------------------------------------------------------------- 26 Recommended Minimum Pavement Sections and Materials ---------------------------------------------- 27 Pavement Maintenance --------------------------------------------------------------------------------------------- 27 Pavement Construction Considerations ------------------------------------------------------------------------- 28

GENERAL COMMENTS ---------------------------------------------------------------------------------28

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

FIGURES

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

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

http://client.terracon.com/

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REPORT SUMMARY

A geotechnical engineering exploration has been performed for the Ft. Logan National Cemetery

- Phase 1 Expansion to be located at 4400 West Kenyon Avenue in Denver, Colorado. Based on the information obtained from this subsurface exploration and the laboratory testing completed, the site appears suitable for the proposed construction; however, the following geotechnical conditions will need to be considered:

■ Up to about 8 feet of fill materials were encountered in portions of the site. In the columbaria area up to 7 feet of fill was encountered, in the pump station area up no fill was encountered, in the culvert area up to 8 feet of fill material was encountered, in the crypt and cremains areas up to 7 feet of fill was encountered and in the roadway alignment up to 8 feet of fill material was encountered. It should be noted that fill depths presented in the boring logs are approximate and the depth, lateral extents, and composition of fill should be expected to vary. We do not possess any information regarding whether the fill was placed under the observation of a geotechnical engineer.

Based upon the results of our field exploration and laboratory testing, it is our opinion the existing fill should not be used to support foundations for the columbaria, pump station, or the culvert without complete removal and modification. It is our opinion that existing fill can be used to support crypts, exterior slabs-on-grade, and pavement construction without complete removal and modification.

■ Laboratory testing indicates the clay and sand fill materials and native clay soils have nil to very high swell potential. The native sand soils and sandstone bedrock are considered to have nil to low expansive potential. Based on our experience, the claystone in the area has low to moderate expansive potential.

■ Test boring data indicate that loose and soft soils may be locally present. Loose and soft soils were encountered in Boring Nos. 4, 5, 17, and 19 in the culvert, roadway alignment, and cremains areas. Consequently, loose and soft soils could be encountered below foundations or other improvements and these conditions will likely require some corrective work. Corrective work could involve removal and re-compaction or replacement, in-place soil densification, or deepening excavations to suitable bearing materials.

■ Based on the geotechnical engineering analyses, the proposed columbaria and pump station may be constructed on spread footing foundation systems bottomed on new engineered fill, provided the owner is willing to accept the associated risk of movement.

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■ Based upon the results of the field exploration and laboratory testing program for this exploration, the proposed culvert may be constructed on native soils or new engineered fill, provided the owner is willing to accept the risk of movement.

■ Based on the 2018 International Building Code (IBC) Section 1613.3.2, the City of Denver amendments to the IBC, and the subsurface conditions encountered in the borings, the seismic site classification for the columbaria, pump station, and crypt areas is C while the seismic site classification for the culvert, cremains, and roadway alignment is D .

■ Existing fill and expansive soils may be encountered at exterior flatwork and pavement construction elevation. Construction of exterior flatwork and pavements on a zone of new engineered fill is recommended to improve performance.

■ The amount of movement associated with foundations, slabs-on-grade, etc. will be related to the wetting of the underlying soils and bedrock. Therefore, it is imperative the recommendations outlined in the Grading and Drainage subsection of Earthwork be followed to reduce potential movement. Moisture conditioning and/or replacement of the on-site fill materials and/or native soils and bedrock should follow the recommendations outlined in Earthwork.

This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled General Comments should be read for an understanding of the report limitations.

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INTRODUCTION

Geotechnical Engineering Report

Ft. Logan National Cemetery - Phase 1 Expansion

4400 West Kenyon Avenue

Denver, Colorado Terracon Project No. 25205232

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the Ft. Logan National Cemetery - Phase 1 Expansion to be located at

4400 West Kenyon Avenue in Denver, Colorado.

As part of our subsurface exploration, twenty borings (designated as Boring Nos. 1 to 20) were drilled at the site to depths of about 10 to 30 feet below existing site grade. Maps showing the site and boring locations are shown in the Site Location and Exploration Plan sections, respectively. The results of the laboratory testing performed on soil and bedrock samples obtained from the site during the field exploration are included on the boring logs in the Exploration

Results section of this report.

The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

◼ Subsurface soil and bedrock conditions

◼ Groundwater levels

◼ Earthwork

◼ Drainage

◼ Lateral earth pressures

◼ Seismic site classification

◼ Foundation design and construction

◼ Pavement design and construction

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.

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Item Description

Location

The project is to be located at 4400 West Kenyon Avenue in Denver, Colorado.

The general location of the proposed project is 39.6430° N, 105.0446° W and is presented below.

See Site Location

Existing

Improvements

Columbaria Areas – This area consists of grass and barren land and has been previously graded.

Pump Station Area – This area consists of grass and has been previously graded.

Culvert Area – This area consists of grass, an asphalt roadway, and pipe culverts and has been previously graded.

Crypt Areas – This area consists of grass, vegetation, concrete pavements, aggregate roadways, an abandoned single-story building, and existing foundations. The foundation systems of the existing building and existing foundations are not known at this time but are assumed to be shallow spread footings.

Cremains Areas – This area consists of grass, vegetation, concrete pavements, and aggregate roadways.

Proposed Roadway – This area consists of grass, vegetation, concrete pavements, and aggregate roadways.

Current Ground

Cover

Inside the fence line the ground cover primarily consists of grass. Outside the fence line the ground cover consists of weeds, trees, and barren land.

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Geology

According to publicly available geologic maps the site typically contains quaternary gravel and alluvium deposits underlain by the Denver and

Arapahoe Formations which typically includes sandstone, mudstone, claystone, and conglomerate.

PROJECT DESCRIPTION

Our initial understanding of the project was provided in our proposal and was discussed during project planning. Our final understanding of the project conditions is as follows:

Item Description

Proposed construction

Columbaria (Boring Nos. 1, 2, and 3) – We understand that the columbaria will consist of free standing structures of 10 feet or less in height (5 entombment niches) and may be up to 500 feet in length and will be above ground. Columbaria will be constructed of precast units on a cast-in place spread footing foundation and may have a brick veneer. Approach concrete sidewalks and concrete walkways around the columbaria are anticipated.

Pump Station (Boring No. 20) – We understand that the pump station will consist of a small (less than 15 foot by 15 foot) prefabricated metal building on a cast-in-place shallow spread footing foundation with a 15 foot deep well that is independent of the structure.

Culvert (Boring No. 4) – We understand that the culvert will consist of a box culvert constructed of precast or cast-in-place concrete and will replace existing pipe culverts that are present below Denver Drive.

Crypts (Boring Nos. 12, 13, 14, and 15) – Regular and oversized pre-placed crypts will consist of precast concrete structures and will be placed in excavations up to 10 feet in depth and may contain up to two caskets per crypt.

Cremains Areas (Boring Nos. 16, 17, 18, 19) – We understand that cremains areas will consist of the burial of an urn or other vessel containing cremated remains that will be placed in an excavation of about 3 feet or less with a flat grave marker.

Roadway (Boring Nos. 5, 6, 7, 8, 9, 10, 11) – We understand the proposed roadway will consist of asphalt or concrete pavements with concrete gutters.

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Anticipated foundation systems

Above Ground Columbaria – spread footings

Pump Station – spread footings

Culvert – spread footings

Crypts – None

Cremains Structures – None

Below grade areas Pre-placed crypts – up to 10 feet in depth

Maximum Loads

(assumed)

■ Columns: 10 to 25 kips

■ Walls: 3 to 4 kips per linear foot (klf)

■ Slabs: 150 to 250 pounds per square foot (psf)

Grading Cut and fill, 6 feet (+/-) max

Excavation depth

■ Columbaria: 3 feet

■ Pump Station: 3 feet

■ Culvert area: 8 feet

■ Pre-placed crypts: 10 feet

■ In-ground cremains: less than 3 feet

Free-standing retaining walls None indicated

Infrastructure

New pavements will likely consist of flexible asphalt and rigid concrete pavement. We anticipate installation of underground utilities within about 5 to 8 feet of finished site grades.

GEOTECHNICAL CHARACTERIZATION

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting, and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of site preparation and foundation options. Conditions encountered at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results section and the GeoModel can be found in the Figures section 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

Vegetative

Layer About 6 inches

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2 Concrete About 8 inches

3 Fill Clay Fill materials consisting of lean and fat clay with varying amounts of sand and gravel; variable consistency

4 Fill Sand Fill materials consisting of sand with varying amounts of clay, silt, and gravel; variable densities

5 Native Clay Native lean and fat clay soils with varying amounts of silt, sand, gravel, and cobbles; very soft to very stiff

6 Native Sand Native sand soils with varying amounts of silt, clay, and gravel;

medium dense

7 Claystone Claystone bedrock, firm to very hard

8 Sandstone Sandstone bedrock, soft to very hard

Based on the results of the laboratory testing and our experience in the area, the clay and sand fill materials and native clay soils have nil to very high swell potential, while the native sand soils, and sandstone bedrock are considered to have nil to low expansive potential. Based on the results of our laboratory testing and our experience, the claystone in the area has low to moderate expansive potential. A summary of laboratory test results is included in the Exploration Results.

Groundwater Conditions

The borings were observed while drilling and upon completion of drilling for the presence and level of groundwater. Borings Nos. 1, 2, 3, 8, 18, and 19 were left open for a single follow up measurement and were then backfilled. Boring Nos. 12, 13, 14, 15, 17, and 20 had a temporary piezometer installed consisting of 10 feet of slotted screen PVC followed by 20 feet of solid PVC riser to the surface surround by sand and capped with a bentonite plug. The water levels observed in the boreholes can be found on the boring logs in Exploration Results and are summarized below.

Columbaria, Pump Station, and Culvert

Boring No.

Shallowest depth to groundwater encountered while or upon completion of drilling

Shallowest depth to groundwater encountered during follow up readings

1 None encountered About 15.7 feet

2 None encountered None encountered

3 None encountered None encountered

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Columbaria, Pump Station, and Culvert

Boring No.

Shallowest depth to groundwater encountered while or upon

4 None encountered None taken

20 About 26 feet About 5.6 feet

1. Due to safety concerns, Boring No. 4 was backfilled immediately after completion. Therefore, subsequent groundwater measurements were not obtained.

2. Reading obtained on 10/5/20.

3. Reading obtained on 10/7/20.

Crypts and Cremains

Boring No.

Shallowest depth to groundwater encountered while or upon

12 None encountered About 28.8 feet

13 None encountered About 24.5 feet

14 None encountered None encountered

15 None encountered None encountered

16 None encountered None taken

17 None encountered None taken

18 None encountered None encountered

19 None encountered None encountered

1. Due to safety concerns, Borings nos. 16, and 17 were backfilled immediately after completion. Therefore, subsequent groundwater measurements were not obtained.

2. Reading obtained on 12/10/20.

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Roadway

Boring No.

Shallowest depth to groundwater encountered while or upon

5 None encountered None taken

6 None encountered None taken

7 None encountered None taken

8 None encountered None encountered

9 None encountered None taken

10 None encountered None taken

11 None encountered None taken

1. Due to safety concerns, borings 5, 6, 7, 9, 10, and 11 were backfilled immediately after completion.

Therefore, subsequent groundwater measurements were not obtained.

2. Reading obtained on 10/21/20.

These observations represent groundwater conditions at the time of the field exploration and may not be indicative of other times or at other locations. Groundwater levels can be expected to fluctuate with varying seasonal and weather conditions.

Zones of perched and/or trapped groundwater may also occur at times in the subsurface soils overlying bedrock, on top of the bedrock surface or within permeable fractures in the bedrock materials. The location and amount of perched water is dependent upon several factors, including hydrologic conditions, type of site development, irrigation demands on or adjacent to the site, fluctuations in water features, seasonal and weather conditions.

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

GEOTECHNICAL OVERVIEW

Based on subsurface conditions encountered in the borings, the site appears suitable for the proposed construction from a geotechnical point of view provided certain precautions and design

Responsive ■ Resourceful ■ Reliable 8 and construction recommendations outlined in this report are followed. We have identified geotechnical conditions that could impact design and construction of the proposed structures, pavements and other site improvements.

Existing Fill Materials

Up to about 8 feet of fill materials were encountered in portions of the site. In the columbaria area up to 7 feet of fill was encountered, in the pump station area up no fill was encountered, in the culvert area up to 8 feet of fill material was encountered, in the crypt and cremains areas up to 7 feet of ill was encountered and in the roadway alignment up to 8 feet of fill material was encountered. It should be noted that fill depths presented in the boring logs are approximate and the depth, lateral extents, and composition of fill should be expected to vary. We do not possess any information regarding whether the fill was placed under the observation of a geotechnical engineer.

Based upon the results of our field exploration and laboratory testing, it is our opinion the existing fill should not be used to support foundations for the columbaria, pump station, or the culvert without complete removal and modification.

If the owner is willing to accept a higher risk of movement for pavements and exterior slabs, consideration could be given to overexcavating a portion of the existing fill materials below these elements, then processing, moisture conditioning and compacting the materials back to subgrade elevation.

It should be noted that there exists the potential for construction debris and/or domestic trash to be encountered within the fill on some portions of the site. Metal fragments were encountered within Boring No. 8. The potential for encountering construction debris is considered to be moderate to high, while the potential for encountering domestic trash is considered to be low. The fill materials should be observed for the presence of trash and debris during site grading and construction.

Terracon has been involved in additional explorations that have been conducted and are underway east of the Phase 1 Expansion to evaluate the extent of a historic landfill. Evaluation and review of report and explorations regarding the historical landfill are outside the scope of this report.

The existing fill can be reused as engineered fill below foundations, slabs-on-grade, and pavements, any deleterious materials are removed, and some movement can be tolerated. Some removal and replacement may be required if unsuitable or soft materials are exposed.

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Expansive Soils and Bedrock

Laboratory testing indicates the clay and sand fill materials and native clay soils have nil to very high swell potential. The native sand soils, and sandstone bedrock are considered to have nil to low expansive potential. Based on our experience, the claystone in the area has low to moderate expansive potential.

This report provides recommendations to help mitigate the effects of soil and bedrock shrinkage and expansion. However, even if these procedures are followed, some movement and cracking in the structures, pavements, and flatwork should be anticipated. The severity of cracking and other damage such as uneven floor slabs will probably increase if any modification of the site results in excessive wetting or drying of the expansive soils and bedrock. Eliminating the risk of movement and distress is generally not feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction. It is imperative the recommendations outlined in the Grading and Drainage subsection of Earthwork in this report be followed to reduce movement.

Loose and Soft Soils

Test boring data indicate that loose and soft soils may be locally present. Loose and soft soils were encountered in Boring Nos. 4, 5, 17, and 19 in the culvert, road, and cremains areas.

Consequently, loose and soft soils could be encountered below foundations or other improvements and these conditions will likely require some corrective work. Corrective work could involve removal and re-compaction or replacement, in-place soil densification, or deepening excavations to suitable bearing materials. In any event, Terracon should be contacted to observe foundation excavations to evaluate bearing conditions and to provide guidance concerning corrective work (if needed).

Shoring

Excavations as deep as 10 feet are anticipated for the proposed below grade crypts and up to 8 feet for the culvert. If excavation slopes cannot be safely excavated in accordance with

Occupational Safety and Health Administration (OSHA) recommendations, shoring will be required. The depth of excavation and subsurface soils will influence the type of shoring system that may be used. A qualified shoring contractor should be contacted to design and install the shoring system.

The lateral earth pressure parameters provided in this report may be used for temporary shoring design; however, the use of theses parameters is at the discretion of the designer. It has been our experience that shoring designers have proprietary or various earth pressure diagrams to base the shoring design. It is up to the shoring designer to interpret the provided parameters.

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Existing Structures

An existing single-story building, associated aggregate-paved areas, existing foundations, and existing concrete pavements are present in the crypt areas. Aggregate-paved areas, existing foundations, and existing concrete pavements are present in the proposed roadway alignment.

The foundation system of the existing building is not known at this time but is assumed to be shallow spread footings. Existing foundation systems should be completely removed.

If drilled pier foundations are encountered, the existing piers should be truncated a minimum depth of 3 feet below areas of planned new construction. If piers are encountered, the contractor should consider surveying existing pier locations so new construction does not encounter abandoned pier locations.

Abandoned utilities associated with the existing structures should be completely removed or fully grouted in place.

Temporary Dewatering

Groundwater was measured in Boring No. 20 in the area of the proposed pump station at a depth of about 5.6 feet below existing ground during follow up groundwater measurements. Provided excavations for the construction of the proposed pump station do not exceed 3 feet, it is our opinion the presence of the shallow groundwater should not significantly influence the construction of the pump station. However, surface water infiltration into the pump station excavations may occur during or after large storm events which may require temporary dewatering.

Ground water was not encountered in Boring No. 4 in the area of the proposed culvert during exploration; however, during or after large storm events or other times when the Memorial Dam spillway is discharging water, surface water may infiltrate into the excavation for the proposed culvert which may require temporary dewatering during construction.

Based on the subsurface conditions encountered in the exploratory borings, a temporary dewatering system consisting of well points may not be very efficient. A more efficient dewatering system used in similar subsurface conditions could consist of shallow trenches in the bottom of the excavation sloped to a sump pit where the water could be removed by pumping. We recommend that a specialty dewatering contractor be contacted to consult on the most efficient temporary dewatering recommendations for the proposed project.

EARTHWORK

Earthwork is anticipated to include clearing and grubbing, excavations, and fill placement. The following sections provide recommendations for use in the preparation of specifications for the

Responsive ■ Resourceful ■ Reliable 11 work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations, floor slabs, and pavements.

Site Preparation

Strip and remove existing vegetation, organics, and other deleterious materials from proposed structure and pavement areas. All exposed surfaces should be free of mounds and depressions that could prevent uniform compaction.

Stripped materials consisting of vegetation, unsuitable fills, and organic materials should be wasted from the site or used to revegetate landscaped areas or exposed slopes after completion of grading operations.

Where possible, the site should be initially graded to create a relatively level surface to receive fill and to provide for a relatively uniform thickness of fill beneath the proposed structure and improvement areas. All exposed areas that will receive fill, once properly cleared, should be scarified to a minimum depth of 12 inches, conditioned to near optimum moisture content, and compacted. It is imperative the moisture content of prepared materials be protected from moisture loss.

Although evidence of underground facilities such as septic tanks and basements was not observed during our exploration, such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed and the excavation thoroughly cleaned prior to backfill placement and/or construction.

It is anticipated that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. However, heavy-duty construction equipment may be necessary when excavating into very hard claystone and sandstone bedrock.

The stability of subgrade soils may be affected by precipitation, repetitive construction traffic, or other factors. If unstable conditions are encountered or develop during construction, workability may be improved by overexcavation of wet zones and mixing these soils with crushed gravel.

Use of geotextiles could also be considered as a stabilization technique. Lightweight excavation equipment may be required to reduce subgrade pumping.

Material Types

Fill for this project should consist of engineered fill. Engineered fill is fill that meets the criteria presented in this report and has been properly documented.

Engineered fill should meet the following material property requirements:

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Fill Type 1,2

USCS Classification Acceptable location for placement

On-site clay soils CL, CH

On-site clay soils are considered suitable for reuse as compacted fill below foundation, slab, structures, and pavement areas, and as general fill for this project.

On-site sand soils mixed with clay soils 3,4

SP, SC, SM

On-site sand soils mixed with clay soils are considered suitable for reuse as compacted fill below foundation, slab, structures, and pavement areas and as general fill for this project.

Processed claystone and sandstone bedrock

N/A

Properly processed on-site claystone and sandstone bedrock is considered suitable for fill below foundation, slab, structures, and pavement areas.

Imported soils Varies

Imported soils meeting the gradation outlined herein can be considered acceptable for use as engineered fill beneath foundations, slabs, structures, and pavement areas.

1. Controlled, 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. A sample of each material type should be submitted to the geotechnical engineer for evaluation.

2. Care should be taken during the fill placement process to avoid zones of dis-similar fill. Improvements constructed over varying fill types are at a higher risk of differential movement compared to improvements over a uniform fill zone.

3. On-site sand soils should be mixed with on-site clay soils to meet the gradation requirements outlined below for imported soils.

4. Granular soils should not be used in the overexcavation zone below the structures, slabs, or pavement areas unless a drain is provided below granular materials.

5. On-site claystone and sandstone bedrock materials should be staged separately from excavated soils and processed to a soil-like consistency with a maximum particle size of 3 inches.

Imported soils for engineered fill (if required) should meet the following material property requirements:

Gradation Percent finer by weight (ASTM C136/AAHSTO

T 27)

3” 100

No. 4 Sieve 50-100

No. 200 Sieve >50

■ Liquid Limit .................................................. 30 (max)

■ Plasticity Index ............................................ 15 (max)

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■ Maximum Expansive Potential (%) .............. 1.0*

*Measured on a sample compacted to approximately 95 percent of the ASTM D698/AASHTO T 99 maximum dry density at optimum water content. The sample is confined under a 200-psf surcharge and submerged.

Compaction Requirements

Engineered fill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift.

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, plate compactor) is used

Compaction requirements 1,2

Minimum of 95% of the material’s standard Proctor maximum dry density (ASTM D698/AASHTO T 99) for clay soils (AASHTO A-6 and A-7-6 soils).

Minimum of 98% of the material’s standard Proctor maximum dry density (ASTM D698/AASHTO T 99) for sand soils (AASHTO A-1 and A-2-6 soils).

Moisture content cohesive soils

(AASHTO A-6, A-7-6 soils and properly processed claystone)

+1 to +3% of the optimum moisture content

Moisture content cohesionless soils

(AASHTO A-1, A-2-6 soils and properly processed sandstone)

-2 to +2% of the optimum moisture content

1. We recommend that engineered fill be tested for water content and compaction during placement. Should the results of the in-place density tests indicate the specified water or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified water and compaction requirements are achieved.

2. Water levels should be maintained low enough to allow for satisfactory compaction to be achieved without the compacted fill material pumping when proofrolled.

3. Moisture conditioned clay soils should not be allowed to dry out. A loss of moisture within these materials could result in an increase in the materials expansive potential. Subsequent wetting of these materials could result in undesirable movement.

Excavation

Excavations into the subsurface soils and bedrock will encounter a variety of conditions. The individual contractor(s) is responsible for designing and constructing stable, temporary

Responsive ■ Resourceful ■ Reliable 14 excavations as required to maintain stability of both the excavation sides and bottom. All excavations should be sloped or shored in the interest of safety following local and federal regulations, including current Occupational Safety and Health Administration (OSHA) excavation and trench safety standards.

Soils and bedrock penetrated by the proposed excavations may vary significantly across the site.

The soil and bedrock classifications are based solely on the materials encountered in the exploratory borings. The contractor should verify that similar conditions exist throughout the proposed area of excavation. If different subsurface conditions are encountered at the time of construction, the actual conditions should be evaluated to determine any excavation modifications necessary to maintain safe conditions.

Grading and Drainage

All grades must be adjusted to provide positive drainage away from the columbaria and pump station during construction and maintained throughout the life of the proposed project. Infiltration of water into utility or foundation excavations must be prevented during construction. Landscaped irrigation adjacent to the foundation systems should be minimized or eliminated. Water permitted to pond near or adjacent to the perimeter of the structures (either during or post-construction) can result in significantly higher soil movements than those discussed in this report. As a result, any estimations of potential movement described in this report cannot be relied upon if positive drainage is not obtained and maintained, and water is allowed to infiltrate the fill and/or subgrade.

We understand that grades surrounding the columbaria will be relatively flat, however, grades should be such that water is not allowed to pond near the columbaria during or post construction.

Permanent grades around the pump station should be sloped at a minimum of 10 percent grade for at least 10 feet beyond the perimeter of the pump station. Roof drains from the pump station should be extended away from the structure a minimum of 10 feet through the use of splash blocks or downspout extensions.

Concrete flatwork should be sloped at a minimum of 2 percent beyond the structure perimeters for the life of the structures. Where Americans with Disabilities Act (ADA) or other requirements or existing site features limit the gradient, slopes on the order of ½ to 1 percent minimum may be necessary to comply with the ADA but do increase the risk of unanticipated movement.

Backfill against footings, exterior walls, and in utility and sprinkler line trenches should be compacted in accordance with recommendations in this report and free of all construction debris to reduce the possibility of water infiltration. After construction and prior to project completion, we recommend that verification of final grading be performed to document that positive drainage, as described above, has been achieved.

Crypts should be drained as discussed in the Pre-placed Crypts section.

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Where paving or flatwork abuts the structures, care should be taken that joints are properly sealed and maintained to prevent the infiltration of surface water.

Consideration should be given to snow removal practices that will minimize the stockpiling of snow in landscaped areas adjacent to structural improvements. In addition care should be taken so that areas adjacent to movement sensitive structural improvements are not excessively irrigated.

Trees or other vegetation whose root systems have the ability to remove excessive moisture from the subgrade and foundation soils should not be planted next to the movement sensitive structures. Trees and shrubbery should be kept away from the exterior edges of foundations, a distance at least equal to their expected mature height.

Earthwork Construction Considerations

Upon completion of grading operations, care should be taken to maintain the moisture content of the subgrade prior to construction of slabs-on-grade, pavements, etc. Construction traffic over prepared subgrade should be minimized and avoided to the extent practical. Construction traffic over processed clay subgrade will eventually reduce the moisture content and increase the density of the subgrade. Subsequent wetting of these materials will result in undesirable movement.

The site should also be graded to prevent ponding of surface water on prepared subgrade or in excavations. In areas where water is allowed to pond over a period of time, the affected area should be removed and allowed to dry out; however, allowing the clay soils to dry out below the optimum moisture content is not recommended. If constraints do not allow for moisture conditioning of affected clays as recommended in this report, the affected area should be overexcavated and replaced with engineered fill. As an alternative, geotextiles could also be considered as a stabilization technique.

The geotechnical engineer should be retained during the construction phase of the project to observe earthwork and to perform necessary tests and observations during overexcavation operations, excavations, subgrade preparation; proof-rolling; placement and compaction of controlled compacted fills; backfilling of excavations into the completed subgrade, and just prior to construction of structure foundations.

UTILITY RECOMMENDATIONS

If utility trenches beneath the pump station are backfilled with relatively clean granular material, they should be capped with at least 18 inches of on-site clay soil to reduce the infiltration and conveyance of surface water through the trench backfill.

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Utility trenches are a common source of water infiltration and migration. All utility trenches that penetrate beneath the pump station should be effectively sealed to restrict water intrusion and flow through the trenches that could migrate below the structures. We recommend constructing an effective clay “trench plug” that extends at least 10 feet out from the structure exteriors. The clay plug material should consist of on-site clay compacted in accordance with the recommendations presented in the Compaction Requirements subsection of Earthwork. The clay fill should completely surround the utility line and be properly placed and compacted in accordance with recommendations in this report.

CORROSIVITY

The following table lists the results of laboratory water-soluble sulfate, pH, and electrical resistivity testing performed on samples obtained during our field exploration. These values may be used to estimate potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction.

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Boring No.

Sample

Depth

(feet)

Water-

Soluble

Sulfate

Water-

Soluble

Chlorides

Sulfides pH

Electrical

Resistivity

(ohm.cm)

1 0 – 5 0.007 0.0053 Trace 8.1 962

2 0 – 5 0.003 0.0032 Positive 7.8 1360

3 0 – 5 0.011 0.0066 Trace 8.0 1138

4 0 – 5 0.012 0.0072 Positive 7.7 1030

5 0 – 5 0.054 0.0155 Trace 8.0 657

6 0 – 5 <0.001 0.0004 Trace 8.0 3409

7 0 – 5 0.008 0.0004 Trace 8.0 1543

8 0 – 5 0.003 0.0004 Trace 8.3 2587

9 0 – 5 0.003 0.0003 Trace 8.0 1812

10 0 – 5 <0.001 0.0001 Negative 8.1 991

11 0 – 5 0.010 0.0028 Negative 8.1 3167

12 0 – 5 <0.001 0.0004 Trace 7.9 1589

13 0 – 5 0.006 0.0009 Positive 7.2 1231

14 0 – 5 0.004 0.0013 Trace 7.9 1789

16 0 – 5 <0.001 0.0002 Trace 8.0 2766

17 0 – 5 0.002 0.0016 Positive 7.7 1649

18 0 – 5 0.003 0.0006 Trace 8.5 1797

19 0 – 5 0.001 0.0003 Trace 7.9 1921

20 0 – 5 0.026 0.0130 Trace 7.9 835

1. Results of water-soluble sulfate testing indicate that samples of the on-site soils have an exposure class of S0 when classified in accordance with Table 19.3.1.1 of the American Concrete Institute (ACI) Design Manual.

The results of the testing indicate ASTM Type I Portland Cement is suitable for project concrete in contact with on-site soils. However, if there is no (or minimal) cost differential, use of ASTM Type II Portland Cement is recommended for additional sulfate resistance of construction concrete. Concrete should be designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 19.

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SOIL NUTRIENTS

Soil nutrient testing was conducted on shallow soil samples obtained from a majority of the borings following exploration. The results of the testing are presented in the Exploration Results section of this report.

COLUMBARIA AND PUMP STATION

Based upon the results of the field exploration and laboratory testing program for this exploration, the following foundation systems were evaluated for use in supporting the proposed columbaria and pump station:

■ Spread footings on new engineered fill.

■ Straight-shaft, cast-in-place piers/shafts constructed in bedrock.

Based on the subsurface conditions encountered in the exploratory borings and results of the laboratory testing, the proposed columbaria and pump station may be constructed on spread footing foundation systems bottomed on new engineered fill, provided the owner is willing to accept the associated risk of movement.

Alternatively, if the owner is not willing to accept the associated risk of movement for spread footings, we recommend the proposed structures be constructed on drilled pier foundation systems. If the owner chooses to construct the proposed structures on drilled piers, we should be contacted to provide drilled pier foundation design recommendations.

Spread Footing Foundation Recommendations

Design recommendations for spread footing foundation systems are presented in the following paragraphs.

Description Value

Proposed Structure Columbarium Pump Station

Foundation Subgrade Preparation

Minimum of 4 foot zone of new engineered fill and all existing fill must be overexcavated to native soils and replaced with properly moisture conditioned and compacted fill.

Foundation subgrade soils should be scarified a minimum of 12 inches, properly moisture conditioned and compacted

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Description Value

Lateral Extent of Foundation Subgrade

Preparation

Minimum of 5 feet outside foundation

Minimum of 12 inches outside foundation

Supporting Stratum New engineered fill Native soils or new engineered fill

Maximum Net Allowable Bearing

Pressure 1.2

2,500 psf

Minimum Dead Load Pressure 500 psf or what is practical

Coefficient of Friction (Sliding) 0.3

Minimum Footing Dimensions Isolated footings: 24 inches

Continuous footings: 18 inches

Minimum Embedment Below Finished

Grade for Frost Protection 3 feet

Approximate Total Movement 1 to 1-1/2 inches About 1 inch

Estimated Differential Movement 4,5,6

About ½ to ¾ of total movement

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

2. Maximum allowable soil bearing pressure can be increased by 1/3 for transient loading conditions.

3. A minimum dead load pressure is not applicable for mat foundations.

4. Foundation movement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth of the footings, the thickness of engineered fill, and the quality of the earthwork operations and footing construction.

5. Footings should be proportioned on the basis of equal total dead load pressure to reduce differential movement between adjacent footings.

6. Estimated differential movement may be larger on structures over 40 feet in length.

Additional foundation movements could occur if water from any source infiltrates the foundation soils; therefore, proper drainage should be provided in the final design and during construction and throughout the life of the structures. Failure to maintain the proper drainage as recommended in the Grading and Drainage section of Earthwork will nullify the movement estimates provided above.

The base of all foundation excavations should be free of water and loose soil prior to concrete placement. Concrete should be placed soon after excavating to reduce bearing soil disturbance.

Should the soils at bearing level become excessively dry, disturbed or saturated, or frozen, the affected soil should be removed prior to placing concrete.

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CULVERT DESIGN RECOMMENDATIONS

Based upon the results of the field exploration and laboratory testing program for this exploration, the proposed culvert may be constructed on native soils or new engineered fill, provided the owner is willing to accept the risk of movement.

We anticipate the culvert will be bottomed in the very soft silt soil encountered at about 8 feet in

Boring No. 4 and will most likely require stabilization. Stabilization of these soils may consist of incorporation of crushed gravel with the existing soil and or the use of geotextiles.