GLEN_15-4104_Geotech_Report.pdf

GEOTECHNICAL EVALUATION

GLEN 15-4104

ENOCH ROAD DESIGN

SCHRIEVER AIR FORCE BASE

COLORADO SPRINGS, COLORADO

PREPARED FOR:

Merrick & Company

5970 Greenwood Plaza Boulevard Greenwood Village, Colorado 80111

PREPARED BY:

Ninyo & Moore

Geotechnical and Environmental Sciences Consultants 6001 South Willow Drive, Suite 195 Greenwood Village, Colorado 80111

December 16, 2015 Project No. 501050001

December 16, 2015 Project No. 501050001

Merrick & Company Attention: Ms. Polly Crosby 5970 Greenwood Plaza Boulevard Greenwood Village, Colorado 80111

Subject: Geotechnical Evaluation

GLEN 15-4104

Enoch Road Design

Schriever Air Force Base Colorado Springs, Colorado

Dear Ms. Crosby:

In accordance with your authorization and our agreement dated August 26th, 2015, Ninyo & Moore has performed a geotechnical evaluation for the above-referenced site. The attached report presents our methodology, findings, and conclusions regarding the geotechnical conditions at the project site and provides geotechnical engineering recommendations for the proposed improvements.

We appreciate the opportunity to be of service to you during this phase of the project.

Sincerely, NINYO & MOORE

Kelley Lange, EI Staff Engineer

Brian F. Gisi, PE Principal Engineer

KL/BFG

Distribution: (1) Addressee (via e-mail)

12/16/2015

Enoch Road Design December 16, 2015 Schriever Air Force Base, Colorado Project No. 501050001

501050001 R i

TABLE OF CONTENTS

Page

1. INTRODUCTION

2. SCOPE OF SERVICES

3. SITE DESCRIPTION

4. PROPOSED CONSTRUCTION

5. FIELD EXPLORATION AND LABORATORY TESTING

6. GEOLOGY AND SUBSURFACE CONDITIONS

6.1. Geologic Setting

6.2. Subsurface Conditions

6.2.1. Fill

6.2.2. Alluvial Deposits

6.3. Groundwater

7. CONCLUSIONS

8. RECOMMENDATIONS

8.1. Earthwork

8.1.1. Excavations

8.1.2. Site Grading

8.1.3. Re-Use of Site Soils

8.1.4. Fill Placement and Compaction

8.1.5. Imported Soil

8.2. Pavements

8.2.1. Pavement Subgrade Support

8.2.2. Pavement Design

8.2.3. Pavement Section Recommendations

8.2.4. Pavement Materials

8.2.5. Pavement Subgrade Preparation

8.2.6. Pavement Maintenance

8.3. Corrosion Considerations

8.3.1. Concrete

8.3.2. Buried Metal Pipes

8.4. Scaling

8.5. Frost Heave

8.6. Construction in Cold or Wet Weather

8.7. Construction Observation and Testing

8.8. Plan Review

8.9. Pre-Construction Meeting

9. LIMITATIONS

10. REFERENCES

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Tables Table 1 – Recommended Pavement Structural Sections

Figures Figure 1 – Site Location Figure 2 – Boring Locations

Appendices Appendix A – Boring Logs Appendix B – Laboratory Testing Appendix C – Pavement Section Design Calculations

501050001 R 1

1. INTRODUCTION

In accordance with your request and authorization, we have performed a geotechnical evaluation for the proposed road improvements to be located along Enoch Road from Sputnik Street to the

Base-X Area located on Schriever Air Force Base in Colorado Springs, Colorado. The approximate location of the site is depicted on Figure 1.

The purpose of our study was to evaluate the subsurface conditions and to provide design and construction recommendations regarding geotechnical aspects of the proposed project. This report presents the findings of our subsurface exploration, results of our laboratory testing, conclusions regarding the subsurface conditions at the site, and geotechnical recommendations for design and construction of this project.

2. SCOPE OF SERVICES

The scope of our services for the project generally included:

Review of referenced background information, including aerial photographs, published geologic and soil maps, previous geotechnical evaluations, in-house geotechnical data, and available topographical information pertaining to the project site and vicinity.

Notification of Utility Notification Center of Colorado (UNCC) of the boring locations prior to drilling.

Drilling, logging, and sampling of seven small-diameter exploratory borings within the Enoch Road right-of-way to depths of approximately 5 to 10½ feet below ground surface (bgs). The boring logs are presented in Appendix A. Boring locations are presented on Figure 2.

Performance of laboratory tests on selected samples obtained from the borings to evaluate engineering properties including in-situ moisture content and dry density, Atterberg limits, No. 200 sieve, Proctor density, California bearing ratio (CBR), and soil corrosivity characteristics. The results of the laboratory testing are presented on the boring logs and in Appendix B.

Compilation and analysis of the data obtained.

Preparation of this report presenting our findings, conclusions, and geotechnical recommendations regarding design and construction of the project.

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3. SITE DESCRIPTION

The project site is located along Enoch Road between Sputnik Street and the Base-X Area within

Schriever Air Force Base in Colorado Springs, Colorado. At the time of our exploration, Enoch road was a two-lane, gravel road. The approximate location of the site is depicted on Figure 1.

4. PROPOSED CONSTRUCTION

The project includes improvement to the to the roadway to the Base-X Area which will be approximately 26 feet in width and will match the existing pavement section at Sputnik Street.

The new roadway will include two, 12-foot wide lanes delineated with white edge line stripping and a double yellow centerline strip. The roadway design will be designed using an Industrial

Street classification with a minimum 20-year design life 18-kip equivalent single-axel load

(ESAL) traffic loading value of 1,250,000.

5. FIELD EXPLORATION AND LABORATORY TESTING

On October 29, 2015, Ninyo & Moore conducted subsurface exploration at the site to evaluate the existing subsurface conditions and to collect soil samples for laboratory testing. The evaluation consisted of the drilling, logging, and sampling of seven small-diameter borings using a truck-mounted drill rig equipped with 4-inch diameter solid-stem continuous flight augers. The borings were advanced to depths of approximately 5 to 10½ feet bgs. The approximate locations of the borings are presented on Figure 2. Relatively undisturbed and disturbed soil samples were collected at selected intervals. The sampling methods used during the subsurface evaluation are presented in Appendix A.

Soil samples collected during the subsurface exploration were transported to the Ninyo & Moore laboratory for geotechnical laboratory analyses. Selected samples were analyzed to evaluate engineering in-situ moisture content and dry density, Atterberg limits, No. 200 sieve, Proctor density, California bearing ratio (CBR), and soil corrosivity characteristics. The results of the in-situ moisture content and dry density tests are presented on the boring logs in Appendix A.

Descriptions of the laboratory test methods and the remainder of the test results are presented in

Appendix B.

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6. GEOLOGY AND SUBSURFACE CONDITIONS

The geology and subsurface conditions at the site are described in the following sections.

6.1. Geologic Setting

The site is located within Schriever Air Force Base in Colorado Springs, approximately 18 miles east of the Rocky Mountains, within the Colorado Piedmont section of the Great

Plains Physiographic Province. The Laramide Orogeny uplifted the Rocky Mountains during the late Cretaceous and early Tertiary Periods. Subsequent erosion deposited sediments east of the Rocky Mountains, including the Denver Formation, Laramie Formation, and Pierre

Shale in the area. As a result of regional uplift approximately 5 to 10 million years ago, streams such as the South Platte River down-cut and excavated into the Great Plains forming the Colorado Piedmont section (Trimble, 1980). Surficial geology of the site is mapped by

Tweto (1979) as older gravels and alluvium consisting of gravel, sand, silt, and clay.

6.2. Subsurface Conditions

Our understanding of the subsurface conditions at the project site is based on our field exploration and laboratory testing, review of published geologic maps, historic aerial photographs, and our experience with the general geology of the area. The following sections provide a generalized description of the subsurface materials encountered. More detailed descriptions are presented on the boring logs in Appendix A.

6.2.1. Fill

The borings initially encountered approximately 2½ to 8 inches of road base gravel.

Below this, fill materials were encountered to depths between 2½ and 5 feet bgs. The fill is considered undocumented. The fill material encountered generally consisted of various shades of brown, dry to moist, clayey sand with gravel. The samples were classified as A-2-6 soils in accordance with the American Association of State Highway and Transportation Officials) AASHTO classification system.

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Laboratory testing of selected samples indicate that the fill materials have in-place moisture contents between approximately 6.0 and 11.4 percent and in-place dry densities between approximately 109.6 and 121.0 pounds per cubic foot (pcf).

6.2.2. Alluvial Deposits

Alluvial deposits were encountered below the fill material in Borings B-2 through B-7 and extended to the borings’ termination depths ranging between approximately 5 and

10½ feet bgs. The alluvium generally consisted of light brown to yellowish brown, moist, firm to very stiff, sandy lean clay and loose to medium dense sand with clay and clayey sand. The samples were generally classified as A-6 soils using the AASHTO classification system.

Based on the results of the laboratory testing, selected samples of the alluvium had in-place moisture contents between approximately 12.7 and 17.5 percent and dry densities between approximately 105.1 and 108.3 pcf. Selected samples of the alluvial materials were tested and exhibited swell potentials of less than 0.5 percent when inundated at surcharge pressure of 250 pounds per square inch (psf).

6.3. Groundwater

Groundwater was not encountered in our borings at the time of drilling. Groundwater levels can fluctuate due to seasonal variations, irrigation, groundwater withdrawal or injection, and other factors. Groundwater is not anticipated to be encountered during pavement construction.

7. CONCLUSIONS

Based on the results of the subsurface evaluation, laboratory testing, and data analyses, it is our opinion that the proposed project is feasible from a geotechnical standpoint, provided the recommendations presented herein are implemented and appropriate construction practices are followed. Geotechnical design and construction considerations for the proposed project include the following:

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Fill materials were encountered in each boring and extended to depths of up to approximately 5 feet bgs. The thickness of existing fill should be expected to vary across the site.

The thickness of the existing road base gravel is variable. As a result, paving directly on these materials is not recommended. However, the material could be incorporated into the aggregate base course below the proposed pavements.

Alluvial deposits were encountered beneath the fill materials in Borings B-2 through B-7 and extended to the boring termination depths of between approximately 5 and 10½ feet bgs.

Site soils generated from on-site excavation activities consisting of fill and alluvium that are free of deleterious materials, and do not contain particles larger than 3 inches in diameter, can generally be used as engineered fill during site grading provided they are moisture-conditioned and compacted as recommended in this report.

Groundwater was not encountered in our borings at the time of our subsurface exploration.

Groundwater levels will fluctuate due to seasonal variations from precipitation, irrigation, groundwater withdrawal or injection, and other factors.

Based on our laboratory data and our experience with similar materials at adjacent sites, the sulfate content of the tested soils presents a low risk of sulfate attack to concrete.

Notwithstanding the sulfate test results, we recommend the use of Type I/II cement for construction of concrete structures at this site.

8. RECOMMENDATIONS

Based on our understanding of the project, the following sections present our geotechnical recommendations for design and construction of the proposed improvements.

8.1. Earthwork

The following sections provide our earthwork recommendations for this project.

8.1.1. Excavations

Our evaluation of the excavation characteristics of the on-site materials is based on the results of the subsurface exploration, our site observations, and our experience with similar materials. The on-site surface and near surface soils (fill materials and alluvium) may generally be excavated with medium to heavy-duty earthmoving or excavation equipment in good operating condition. Bedrock was not encountered during our

501050001 R 6 subsurface exploration, and as a result, is not anticipated to be encountered during earthwork operations.

Equipment and procedures that do not cause significant disturbance to the excavation bottoms should be used. Excavators and backhoes with buckets having large claws to loosen the soil should be avoided when excavating the bottom 6 to 12 inches of excavations as such equipment may disturb the excavation bases.

The fill and alluvial deposits are susceptible to variations in moisture-content. As a result, and depending on the time of year construction occurs, wet or saturated soils may be encountered after periods of heavy or prolonged precipitation. These soils may soften under the action of light equipment and foot traffic. Where encountered, drying or overexcavation of these materials is recommended. If the subgrade becomes disturbed, it should be compacted or removed and replaced before placing additional backfill material.

Stabilization methods should be provided by the grading contractor, as needed, and may include the use of geogrids, geotextiles, pushing oversized rock into the subgrade, and/or chemical stabilization. The subgrade stabilization methods proposed should be discussed with the Geotechnical Engineer prior to implementation. The stabilization method selected should consider the effects of such stabilization on future utility installation and/or repair work.

Groundwater was not encountered in our borings at the time of our subsurface exploration. Groundwater levels can fluctuate due to sessional variations from precipitation, irrigation, groundwater withdrawal or injection, or other factors.

Groundwater is not expected to be a constraint to the construction of these improvements.

The contractor should provide safely sloped excavations or an adequately constructed and braced shoring system, in compliance with Occupational Safety and Health

Administration (OSHA, 2005) guidelines, for employees working in an excavation that

501050001 R 7 may expose employees to the danger of moving ground. If material is stored or equipment is operated near an excavation, stronger shoring should be used to resist the extra pressure due to superimposed loads.

8.1.2. Site Grading

Prior to grading, the ground surface in proposed structure and improvement areas should be cleared of any surface obstructions, debris, topsoil, organics (including vegetation), and other deleterious material.

Materials generated from clearing operations should be removed from the project site for disposal (e.g. at a legal landfill site). Obstructions that extend below finish grade, if present, should be removed and resulting voids filled with compacted, engineered fill or

Controlled Low Strength Material (CLSM).

Pavements and exterior flatwork should be placed on a zone of moisture-conditioned and compacted engineered fill extending 12 or more inches below the bottom of the pavement section or flatwork. This zone could be created by scarifying, moisture-conditioning (as needed), and recompacting the exposed subgrade materials.

The exposed subgrade materials should be firm and unyielding prior to fill placement.

The extent of and depths of any removal should be evaluated by our representative during the excavation work based on observation of the soils exposed. Additional recommendations specific to the site conditions encountered may be provided at the time of construction. The project budget should include additional cost associated with the removal and replacement of additional fill material. Subgrade materials that are disturbed during grading should be moisture conditioned and re-compacted according to the recommendations provided in this report.

8.1.3. Re-Use of Site Soils

Based on the laboratory test results and our general observations, it is our opinion the excavated fill and alluvial soils that are free of deleterious materials and organic matter, and do not contain particles larger than 3 inches in diameter, can generally be used as

501050001 R 8 engineered fill provided they are moisture-conditioned and compacted as recommended in this report.

Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) larger than 3 inches in diameter may be incorporated into the project fills in non-structural areas and below the anticipated utility installation depths. A Geotechnical

Engineer should be consulted regarding appropriate recommendations for usage of such materials on a case-by-case basis when such materials have been observed during earthwork. Care should be taken to avoid nesting of oversized materials during placement. Recommendations provided in Section 203 of the current CDOT Standard

Specifications for Road and Bridge Construction should be followed during the placement of oversized material.

The on-site road base gravel encountered in our borings may be incorporated into the aggregate base course below pavements or engineered fill. The thickness of the road base gravel encountered varied across the site. A uniform thickness of road base, if used, should be placed beneath the pavement.

8.1.4. Fill Placement and Compaction

Fine-grained soils (on-site soils that classify as CL) used as engineered fill should be moisture-conditioned to moisture contents between 1 percent below and 3 percent over optimum moisture content. Granular soils (on-site soils that classify as SC or import soils) used as engineered fill should be moisture-conditioned to moisture contents within 2 percent of optimum moisture content. Engineered fill should be compacted to a relative compaction of 95 percent, or more, as evaluated by ASTM D698.

Fill should be compacted by appropriate mechanical methods using vibratory compaction equipment. The optimal lift thickness of fill will depend on the type of soil and compaction equipment used, but should generally not exceed approximately

8 inches in loose thickness. Fill materials should not be placed, worked, or rolled while

501050001 R 9 they are frozen or thawing, and should not be placed during poor/inclement weather conditions.

Compaction areas should be kept separate, and no lift should be covered by another until relative compaction and moisture content within the recommended ranges are obtained.

Use of CLSM should be considered in lieu of compacted fill for areas with low tolerances for surface settlements, for excavations that extend below the groundwater table and in areas with difficult access for compaction equipment. CLSM should be placed in lifts of 5 feet or less with a 24-hour or more curing period between each lift.

8.1.5. Imported Soil

Imported soil for use as engineered fill should have 50 or less percent passing the

No. 200 sieve, a very low swell potential (approximately 1 percent or less when wetted against a surcharge pressure of 500 psf when remolded at optimum moisture content), a low plasticity index (approximately 10 to 20), and a CBR-value of 10 or greater.

Imported soil should not contain organic matter, clay lumps, bedrock (claystone, sandstone, etc.) fragments, debris, other deleterious matter, or rocks or hard chunks larger than approximately 3 inches nominal diameter.

Import material in contact with ferrous metals should have low corrosion potential.

Import material in contact with concrete should have soluble sulfate content less than

0.1 percent.

We further recommend that proposed import material be evaluated by the project’s geotechnical consultant at the borrow source for its suitability prior to importation to the project site. Import soil should be moisture-conditioned and placed and compacted in accordance with the recommendations set forth in Section 8.1.4.

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8.2. Pavements

The pavement sections recommended below were developed in general accordance with the guidelines and procedures of the American Association of State Highway and Transportation

Officials (AASHTO, 1993), the Colorado Department of Transportation (CDOT), and the

City of Colorado Springs Pavement Design Criteria Manual (CSPDCM).

8.2.1. Pavement Subgrade Support

The current subgrade soils encountered in our borings typically consisted of clayey sand to lean clay with sand that classify as A-2-6 and A-6 soils in accordance with the

AASHTO classification system. It is anticipated that fill imported to the site will classify as A-2-6 or better.

Laboratory testing performed on the on-site soils indicated a California bearing ratio

(CBR) of 10 or greater. For purposes of new construction, it is assumed that soils placed within 2 feet of the finished pavement subgrade will exhibit an average CBR or

10 or more. If during construction, the subgrade is found to vary from the expected soil conditions, we should be contacted so we may re-evaluate our recommended resilient modulus value.

8.2.2. Pavement Design

Ninyo & Moore used the provided equivalent 18-kip single axle load application

(ESALs) of 1,250,000 for a 20-year design life. If design traffic loadings differ significantly from the above values, we should be notified to re-evaluate the pavement recommendations below.

The subgrade soils encountered consisted of undocumented fill material that generally classified as clayey sand and sandy lean clay.

Pavement designs for the site were calculated based on the 1993 “Guidelines for

Design of Pavement Structures” by AASHTO. The design of flexible pavements was

501050001 R 11 based on the following input parameters from the Pavement Design Criteria Manual by the City of Colorado Springs:

Initial Serviceability: 4.5 Terminal Serviceability: 2.0 Reliability 95% Overall Standard Deviation: 0.44 Resilient Modulus (Mr) [Based on CBR = 10]: 15,000 psi

The design of rigid pavements was based on the following input parameters:

Initial Serviceability: 4.5 Terminal Serviceability: 2.0 Reliability 95% Overall Standard Deviation: 0.34 Load Transfer Coefficient (J): 4.2 Loss of Support (LS) [Natural Subgrade Materials] 2.0 Effective Modulus of Subgrade Reaction (k): 75 pci

8.2.3. Pavement Section Recommendations

Based on the above-mentioned design traffic and input parameters, and following the

AASHTO method of pavement design, the following structural sections were calculated for Enoch Road. Table 1 summarizes the recommended pavement sections.

Table 1 – Recommended Pavement Structural Sections

Street

Recommended Pavement Section

Full Depth AC

(inches)

Composite AC /

ABC

(inches)

PCCP

(inches)

Enoch Road 8.0 1 4.0/12.0 1 8.0 Notes: AC = Asphalt Concrete, ABC = Aggregate Base Course, PCCP = Portland Cement Concrete Pavement

1) Minimum thicknesses per City of Colorado Springs Pavement Design Criteria Manual.

8.2.4. Pavement Materials

The AC pavement shall consist of a bituminous plant mix composed of a mixture of high quality aggregate and bituminous material, which meets the requirements of a job-mix formula established by a qualified engineer. The asphalt material used should be

501050001 R 12 based on a SuperPave Gyratory Design Revolution (NDES) of 75. Lower lifts should be constructed using an asphalt mix Grading S and asphalt cement binder grade PG 64-

22. The top lift should be constructed using an asphalt mix Grading SX and asphalt cement binder grade PG 64-28. An unmodified asphalt cement binder grade of PG 64-

22 may be used for the top lift if allowed by the City of Colorado Springs. Pavement layer thickness should be between 2 and 4 inches for the lower lifts and 2 inches for the top lift. The geotechnical engineer should be retained to review the proposed pavement mix designs, grading, and lift thicknesses prior to construction.

The ABC material placed beneath pavements (if any) should meet the criteria of CDOT

Class 6 aggregate base. Requirements for CDOT Class 6 aggregate base can be found in Section 703 of the current CDOT Standards and Specifications for Road and Bridge

Construction.

Concrete pavements should consist of a plant mix composed of a mixture of aggregate, Portland cement, and appropriate admixtures meeting the requirements of the City of

Colorado Springs. Concrete should have a modulus of rupture of third point loading of

650 psi or more. The concrete should be air-entrained with approximately 6 percent air and should have a cement content of 6 or more sacks per cubic yard. Allowable slump should be 4 inches. Additional recommendations regarding concrete utilized in construction of proposed roadway are provided in Section 8.3.1 and 8.4.

Thickened edges should be used along outside edges of concrete pavements. Edge thickness should be 2 inches or more than the concrete pavement thickness and taper to the actual concrete pavement thickness 36 inches inward from the edge. Integral curbs may be used in lieu of thickened edges. Concrete pavements should have longitudinal and transverse joints that meet the applicable requirements of the City of Colorado

Springs.

Although the use of ABC is not integral for structural support in PCCP pavements, their use will develop a more stable subgrade for concrete truck traffic associated with the

501050001 R 13 pavement construction and help reduce potential slab curl, shrinkage cracking, and subgrade “pumping” through joints.

The use of a prime coat is not needed if the recommended full-depth asphalt section (8 inches of asphalt) is constructed. A prime coat should be applied between the aggregate base course and the asphalt pavement section, if the recommended composite pavement section (4 inches of asphalt over 12 inches of aggregate base course) is constructed. A tack coat should be placed between the asphalt pavement lifts. Prime coat and tack coat applications should be performed in general accordance with Colorado Department of

Transportation (CDOT) Standard Specifications for Road and Bridge Construction, 2011, Sections 407 and 702.

8.2.5. Pavement Subgrade Preparation

For the AC pavement sections recommended above, we recommend the underlying subgrade soils be prepared as described in Section 8.1.2 of this report. The contractor should be prepared either to dry the subgrade materials or moisten them, as needed, prior to compaction. Some site soils may pump or deflect during compaction if moisture levels are not carefully monitored. The contractor should be prepared to process and compact such soils to establish a stable platform for paving, including use of chemical stabilization or geotextiles, where needed.

The prepared subgrade should be protected from the elements prior to pavement placement. Subgrades that are exposed to the elements may need additional moisture conditioning and compaction, prior to pavement placements.

Immediately prior to paving, the subgrade should be proof rolled with a heavily loaded, pneumatic tired vehicle and checked for moisture. Areas that show excessive deflection during proof rolling should be excavated and replaced and/or stabilized. Areas allowed to pond prior to paving may need to be re-worked prior to proof rolling.

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8.2.6. Pavement Maintenance

The collection and diversion of surface drainage away from paved areas is vital to satisfactory performance of the pavements. The subsurface and surface drainage systems should be carefully designed to facilitate removal of the water from paved areas and subgrade soils. Allowing surface waters to pond on pavements will cause premature pavement deterioration. Where topography, site constraints or other factors limit or preclude adequate surface drainage, pavements should be provided with edge drains to reduce loss of subgrade support. The long-term performance of the pavement also can be improved greatly by backfilling and compaction behind curbs, gutters, and sidewalks so that ponding is not permitted and water infiltration is reduced.

The standard care of practice in pavement design describes the recommended flexible pavement section as a “20-year” design pavement; however, many pavements will not remain in satisfactory condition without routine, preventive maintenance and rehabilitation procedures performed during the life of the pavement. Preventive pavement treatments are surface rehabilitation and operations applied to improve or extend the functional life of a pavement. These treatments preserve, rather than improve, the structural capacity of the pavement structure. In the event the existing pavement is not structurally sound, the preventive maintenance will have no long-lasting effect. Therefore, a routine maintenance program to seal joints and cracks, and repair distressed areas is recommended.

8.3. Corrosion Considerations

The corrosion potential of on-site soils to concrete and buried metal was evaluated in the laboratory using selected samples obtained from the exploratory borings. Laboratory testing was performed to assess the effects of sulfate on concrete and the effects of soil resistivity on buried metal. Results of these tests are presented in Appendix B. Recommendations regarding concrete to be utilized in construction of proposed improvements and for buried metal pipes are provided in the following sections.

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8.3.1. Concrete

The test for water-soluble sulfate content of the soils was performed using CDOT Test

Method CP-L 2104. The laboratory test results are presented in Appendix B. The percentage of water-soluble sulfates in water measured was 0.007 percent, corresponding to 73 parts per million. Based on Table 601-2 of the CDOT 2011

Standard Specifications for Road and Bridge Construction, the on-site soils represent a

Class 0 severity of sulfate exposure to concrete on a scale that ranges between Class 0 and Class 3. Therefore, we recommend that the concrete used for this project should have a maximum water to cementitious material ratio of 0.45 and the cementitious materials should meet one of the below outlined requirements.

ASTM C 150 Type I, II or V

ASTM C 595 Type IP, IP(MS) or IP(HS)

ASTM C 1157 Type GU, MS or HS

ASTM C 150 Type III cement if it is allowed, as in Class E concrete

Notwithstanding the sulfate test results and due to the limited number of chemical tests performed, as well as our experience with similar soil conditions, we recommend the use of Type I/II cement for construction of concrete structures at this site. Due to potential uncertainties as to the use of reclaimed irrigation water, or topsoil that may contain higher sulfate contents, pozzolan or admixtures designed to increase sulfate resistance may be considered.

The Structural Engineer should ultimately select the concrete design strength based on the project specific loading conditions. However, higher strength concrete may be selected for increased durability, resistance to slab curling and shrinkage cracking. We recommend the use of concrete with a design 28-day compressive strength of 4,200 psi or more, for concrete slabs at this site. Concrete exposed to the elements should be air-entrained.

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8.3.2. Buried Metal Pipes

The corrosion potential of the on-site materials was analyzed to evaluate its potential effects on buried metals. Corrosion potential was evaluated using the results of laboratory testing of samples obtained during the subsurface evaluation that were considered representative of soils at the subject site.

The results of the laboratory testing indicate the on-site materials have low to moderate resistivity and could potentially be moderately to severely corrosive to ferrous metals.

Therefore, special consideration should be given to the use of heavy gauge, corrosion protected, underground steel pipe or culverts, if any are planned. As an alternative, plastic pipe or reinforced concrete pipe could be considered. A corrosion specialist should be consulted for further recommendations.

8.4. Scaling

Climatic conditions in the project area including relatively low humidity, large temperature changes and repeated freeze-thaw cycles, may cause surficial scaling and spalling of exterior concrete. Occurrence of surficial scaling and spalling can be aggravated by poor workmanship during construction, such as “over-finishing” concrete surfaces and the use of de-icing salts on pavements, particularly during the first winter after construction.

The measures below can be beneficial for reducing the concrete scaling. However, because of the other factors involved, including workmanship, surface damage to concrete can develop even though the measures provided below were followed. The mix design criteria should be coordinated with other project requirements including the criteria for soluble sulfate resistance presented in Section 8.3.1.

Curing concrete in accordance with applicable codes and guidelines.

Maintaining a water/cement ratio of 0.45 by weight for exterior concrete mixes.

Including Type F fly ash in exterior concrete mixes as 20 percent of the cementitious material.

501050001 R 17

Specifying a 28-day, compressive strength of 4,500 or more psi for exterior concrete that may be exposed to de-icing salts.

Avoiding the use of de-icing salts through the first winter after construction.

If colored concrete is being proposed for exterior use at this site, Ninyo & Moore should be contacted for additional consultation. Implementation of special design, construction, and maintenance precautions will be needed in these areas.

8.5. Frost Heave

Site soils are susceptible to frost heave if allowed to become saturated and exposed to freezing temperatures and repeated freeze/thaw cycling. The formation of ice in the underlying soils can result in two or more inches of heave of pavements, flatwork and other hardscaping in sustained cold weather. A portion of this movement may be recovered when the soils thaw, but due to loss of soil density some degree of displacement will remain.

8.6. Construction in Cold or Wet Weather

During construction, the site should be graded such that surface water can drain readily away from the pavement areas. Given the soil conditions, it is important to avoid ponding of water in or near excavations. Water that accumulates in excavations should be promptly pumped out or otherwise removed and these areas should be allowed to dry out before resuming construction. Berms, ditches, and similar means should be used to decrease stormwater entering the work area and to efficiently convey it off site.

Earthwork activities undertaken during the cold weather season may be difficult and should be done by an experienced contractor. Fill should not be placed on top of frozen soils. The frozen soils should be removed prior to the placement of fill or other construction material.

Frozen soil should not be used as engineered fill or backfill. The frozen soil may be reused

(provided it meets the selection criteria) once it has thawed completely. In addition, compaction of the soils may be more difficult due to the viscosity change in water at lower temperatures.

501050001 R 18

If construction proceeds during cold weather, concrete elements should not be placed on frozen subgrade soil. Frozen soil should either be removed from beneath concrete elements, or thawed and recompacted. To limit the potential for soil freezing, the time passing between excavation and construction should be minimized. Blankets, straw, soil cover, or heating may be used to discourage the soil from freezing.

8.7. Construction Observation and Testing

A qualified geotechnical consultant should perform appropriate observation and testing services during grading and construction operations. These services should include observation of any soft, loose, or otherwise unsuitable soils, evaluation of subgrade conditions where soil removals are performed, and performance of observation and testing services during placement and compaction of engineered fill and backfill soils.

The geotechnical consultant should also perform observation and testing services during placement of concrete, asphalt concrete, and steel reinforcement. If another geotechnical consultant is selected to perform observation and testing services for the project, we request that the selected consultant provide a letter to the owner, with a copy to Ninyo & Moore, indicating that they fully understand our recommendations and that they are in full agreement with the recommendations contained in this report. Qualified subcontractors utilizing appropriate techniques and construction materials should perform construction of the proposed improvements.

8.8. Plan Review

The recommendations presented in this report are based on preliminary design information for the proposed project and on the findings of our geotechnical evaluation. When finished, project plans and specifications should be reviewed by the geotechnical consultant prior to submitting the plans and specifications for bid. Additional field exploration and laboratory testing may be needed upon review of the project design plans.

501050001 R 19

8.9. Pre-Construction Meeting

We recommend a pre-construction meeting be held. The owner or the owner’s representa-tive, the architect, the contractor, and the geotechnical consultant should be in attendance to discuss the plans and the project.

9. LIMITATIONS

The field evaluation, laboratory testing, and geotechnical analyses presented in this geotechnical report have been conducted in general accordance with current practice and the standard of care exercised by geotechnical consultants performing similar tasks in the project area. No warranty, expressed or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be encountered during construction. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface evaluation will be performed upon request. Please also note that our evaluation was limited to assessment of the geotechnical aspects of the project, and did not include evaluation of structural issues, environmental concerns, or the presence of hazardous materials.

This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document.

This report is intended for design purposes only. It does not provide sufficient data to prepare an accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant perform an independent evaluation of the subsurface conditions in the project areas. The independent evaluations may include, but not be limited to, review of other geotechnical reports prepared for the adjacent areas, site reconnaissance, and additional exploration and laboratory testing.

501050001 R 20

Our conclusions, recommendations, and opinions are based on an analysis of the observed site conditions. If geotechnical conditions different from those described in this report are encountered, our office should be notified and additional recommendations, if warranted, will be provided upon request. It should be understood that the conditions of a site could change with time as a result of natural processes or the activities of man at the subject site or nearby sites. In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government action or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control.

This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk.

501050001 R

10. REFERENCES

American Association of State Highway and Transportation Officials (AASHTO), 1993, AASHTO Guide for Design of Pavement Structures.

American Association of State Highway and Transportation Officials (AASHTO), 2011, Standard Specifications for Transportation Materials and Methods of Sampling and Testing, 31st Edition, and Provisional Standards.

American Society for Testing and Materials (ASTM), 2015 Annual Book of ASTM Standards.

City of Colorado Springs Pavement Design Criteria Manual (CSPDCM), 2010, City of Colorado Springs Engineering Criteria Manual, dated July 1.

Colorado Department of Transportation (CDOT), 2011, Standard Specifications for Road and Bridge Construction.

Colorado Department of Transportation (CDOT), 2015, 2016 Pavement Design Manual.

Hart, Stephen S., 1973-1974, Potentially Swelling Soil and Rock in the Front Range Urban Corridor, Colorado: Colorado Geological Survey, Sheet 2 of 4.

Ninyo & Moore, In-house proprietary information.

Occupational Safety and Health Administration (OSHA), 2005, OSHA Standards for the Construction Industry, 29 CFR Part 1926: dated June.

Trimble, Donald E., 1980, The Geologic Story of the Great Plains, Geological Survey Bulletin 1493.

Tweto, Ogden, 1979, Geologic Map of Colorado: U.S. Geological Survey Special Geologic Map, scale 1:500,000.

SITE LOCATION

FIGURE

Ap p ro x i ma te Sca l e :

1 i n ch = 19 0 0 f e e t

Note: Dimensions, directions, and locations are approximate.

DATE:

12/15 file no: 1050vmap1115

PROJECT NO:

501050001

ENOCH ROAD DESIGN

SCHRIEVER AIR FORCE BASE

COLORADO SPRINGS, COLORADO

Source: MacVan, Denver Metro Edition, 2010.

APPROXIMATE

SITE LOCATION

APPROXIMATE

SITE LOCATION

N

APPROXIMATE

SITE LOCATION

fil e n o :1 b lm

Source: MERRICK & COMPANY.

Note: Dimensions, directions, and locations are approximate.

FIGURE

2DATE:

12/15

PROJECT NO:

501050001

ENOCH ROAD DESIGN

SCHRIEVER AIR FORCE BASE

COLORADO SPRINGS, COLORADO

BORING LOCATIONS0

Ap p ro x i ma te Sca l e :

1 i n ch = 32 0 f e e t

N

0 8040

LEGEND

Boring LocationB-7

B-1 B-2 B-3 B-4 B-5

B-7

B-6

APPENDIX A

BORING LOGS

Field Procedure for the Collection of Disturbed Samples Disturbed soil samples were obtained in the field using the following methods.

Bulk Samples Bulk samples of representative earth materials were obtained from the exploratory borings.

The samples were bagged and transported to the laboratory for testing.

Field Procedure for the Collection of Ring-lined Samples Ring-lined soil samples were obtained in the field using the following methods.

The Modified California Split-Barrel Drive Sampler The sampler, with an external diameter of 3.0 inches, was lined with thin brass rings with inside diameters of approximately 2.4 inches. The sample barrel was driven into the ground with the weight of a hammer in general accordance with ASTM D 3550. The driving weight was permitted to fall freely. The approximate length of the fall, the weight of the hammer or bar, and the number of blows per foot of driving are presented on the boring logs as an index to the relative resistance of the materials sampled. The samples were removed from the sample barrel in the brass rings, sealed, and transported to the laboratory for testing.

The California Drive Sampler The sampler, with an external diameter of 2.4 inches, was lined with four, 4-inch long, thin brass rings with inside diameters of approximately 1.9 inches. The sample barrel was driven into the ground with the weight of a hammer in general accordance with ASTM D 3550. The driving weight was permitted to fall freely. The approximate length of the fall, the weight of the hammer, and the number of blows per foot of driving are presented on the boring logs as an index to the relative resistance of the materials sampled. The samples were removed from the sample barrel in the brass liners, sealed, and transported to the laboratory for testing.

SOIL CLASSIFICATION CHART PER ASTM D 2488

PRIMARY DIVISIONS

SECONDARY DIVISIONS

GROUP SYMBOL GROUP NAME

COARSE-

GRAINED

SOILS

more than

50% retained on No. 200 sieve

GRAVEL

more than

50% of coarse fraction retained on No. 4 sieve

CLEAN GRAVEL

less than 5% fines

GW well-graded GRAVEL

GP poorly graded GRAVEL

GRAVEL with

DUAL

CLASSIFICATIONS

5% to 12% fines

GW-GM well-graded GRAVEL with silt

GP-GM poorly graded GRAVEL with silt

GW-GC well-graded GRAVEL with clay

GP-GC poorly graded GRAVEL with clay

GRAVEL with

FINES

more than 12% fines

GM silty GRAVEL

GC clayey GRAVEL

GC-GM silty, clayey GRAVEL

SAND

50% or more of coarse fraction passes

No. 4 sieve

CLEAN SAND

less than 5% fines

SW well-graded SAND

SP poorly graded SAND

SAND with

DUAL

CLASSIFICATIONS

5% to 12% fines

SW-SM well-graded SAND with silt

SP-SM poorly graded SAND with silt

SW-SC well-graded SAND with clay

SP-SC poorly graded SAND with clay

SAND with FINES more than 12% fines

SM silty SAND

SC clayey SAND

SC-SM silty, clayey SAND

FINE-

GRAINED

SOILS

50% or more passes No. 200 sieve

SILT and

CLAY

liquid limit less than 50%

INORGANIC

CL lean CLAY

ML SILT

CL-ML silty CLAY

ORGANIC

OL (PI > 4) organic CLAY

OL (PI < 4) organic SILT

SILT and

CLAY

liquid limit 50% or more

INORGANIC

CH fat CLAY

MH elastic SILT

ORGANIC

OH (plots on or above “A”-line) organic CLAY

OH (plots below “A”-line) organic SILT

Highly Organic Soils PT Peat

USCS METHOD OF SOIL CLASSIFICATION

Explanation of USCS Method of Soil Classification

PROJECT NO. DATE FIGURE

APPARENT DENSITY - COARSE-GRAINED SOIL

APPARENT

DENSITY

SPOOLING CABLE OR CATHEAD AUTOMATIC TRIP HAMMER

SPT

(blows/foot)

MODIFIED

SPLIT BARREL

(blows/foot)

SPT

(blows/foot)

MODIFIED

SPLIT BARREL

(blows/foot)

Very Loose < 4 < 8 < 3 < 5

Loose 5 - 10 9 - 21 4 - 7 6 - 14

Medium Dense 11 - 30 22 - 63 8 - 20 15 - 42

Dense 31 - 50 64 - 105 21 - 33 43 - 70

Very Dense > 50 > 105 > 33 > 70

CONSISTENCY - FINE-GRAINED SOIL

CONSIS-

TENCY

SPOOLING CABLE OR CATHEAD AUTOMATIC TRIP HAMMER

SPT

(blows/foot)

MODIFIED

SPLIT BARREL

(blows/foot)

SPT

(blows/foot)

MODIFIED

SPLIT BARREL

(blows/foot)

Very Soft < 2 < 3 < 1 < 2

Soft 2 - 4 3 - 5 1 - 3 2 - 3

Firm 5 - 8 6 - 10 4 - 5 4 - 6

Stiff 9 - 15 11 - 20 6 - 10 7 - 13

Very Stiff 16 - 30 21 - 39 11 - 20 14 - 26

Hard > 30 > 39 > 20 > 26

LIQUID LIMIT (LL), %

P

LA

S

TI

C

IT

Y

IN

D E

X

P I)

0 10

20 30 40 50 60 70 80 90 100

MH or OH

ML or OLCL - ML

PLASTICITY CHART

GRAIN SIZE

DESCRIPTION SIEVE

SIZE

GRAIN

SIZE

APPROXIMATE

SIZE

Boulders > 12” > 12” Larger than basketball-sized

Cobbles 3 - 12” 3 - 12” Fist-sized to basketball-sized

Gravel

Coarse 3/4 - 3” 3/4 - 3” Thumb-sized to fist-sized

Fine #4 - 3/4” 0.19 - 0.75” Pea-sized to thumb-sized

Sand

Coarse #10 - #4 0.079 - 0.19” Rock-salt-sized to pea-sized

Medium #40 - #10 0.017 - 0.079” Sugar-sized to rock-salt-sized

Fine #200 - #40 0.0029 - 0.017”

Flour-sized to sugar-sized

Fines Passing #200 < 0.0029” Flour-sized and smaller

CH or OH

CL or OL

BORING LOG EXPLANATION SHEET

XX/XX

Bulk sample.

Modified split-barrel drive sampler.

2-inch inner diameter split-barrel drive sampler.

No recovery with modified split-barrel drive sampler, or 2-inch inner diameter split-barrel drive sampler.

Sample retained by others.

Standard Penetration Test (SPT).

No recovery with a SPT.

Shelby tube sample. Distance pushed in inches/length of sample recovered in inches.

No recovery with Shelby tube sampler.

Continuous Push Sample.

Seepage.

Groundwater encountered during drilling.

Groundwater measured after drilling.

SM MAJOR MATERIAL TYPE (SOIL):

Solid line denotes unit change.

CL Dashed line denotes material change.

Attitudes: Strike/Dip b: Bedding c: Contact j: Joint f: Fracture F: Fault cs: Clay Seam s: Shear bss: Basal Slide Surface sf: Shear Fracture sz: Shear Zone sbs: Shear Bedding Surface

The total depth line is a solid line that is drawn at the bottom of the boring.

BORING LOG

Explanation of Boring Log Symbols

PROJECT NO. DATE FIGURE

D E

P T

H (f e e t)

B L O

W S

/F O

O T

M O

IS

T

U R

E

D R

Y D

E N

S

IT

Y (P

C F

C

LA

S S

IF

IC

A T

IO

N

U

.S .C

.S

6.0 121.0

SC

ROAD BASE GRAVEL:

Approximately 5-1/2 inches thick.

FILL:

Light brown, dry, clayey SAND.

(AASHTO A-2-6)

Reddish brown.

Total Depth = 5 feet.

Groundwater not encountered during drilling.

Backfilled with on-site soil shortly after drilling on 10/29/15.

Note: Groundwater, though not encountered at the time of drilling, may rise to a higher level due to seasonal variations in precipitation and several other factors as discussed in the report.

The ground elevation shown above is an estimation only. It is based on our interpretations of published maps and other documents reviewed for the purposes of this evaluation. It is not sufficiently accurate for preparing construction bids and design documents.

BORING LOG

ENOCH ROAD DESIGN

SCHRIEVER AIR FORCE BASE, COLORADO SPRINGS, COLORADO

PROJECT NO.

501050001

DATE

12/15

FIGURE

A-1

D E

P T

H fe e t)

B u lk S

A M

P L

E S

D ri ve n

B L

O W

S /F

O O

T

M O

IS

T

U R

E

D R

Y D

E N

S

IT

Y

P C

F

S Y

M B

O L

C L

A S

S

IF

IC

A

T

IO

N U

.S .C

.S

DESCRIPTION/INTERPRETATION

DATE DRILLED 10/29/15 BORING NO. B-1

GROUND ELEVATION 5,208' ± MSL SHEET 1 OF

METHOD OF DRILLING 6" Diameter Solid Stem Auger (CME-55) (Vine Labs)

DRIVE WEIGHT 140 lbs. (Auto-Hammer) DROP 30"

SAMPLED BY DLH LOGGED BY DLH REVIEWED BY BFG

17.5 108.3

SC

CL

SP-SC

ROAD BASE GRAVEL:

Approximately 8 inches thick.

FILL:

Brown, dry to moist, clayey fine to coarse SAND

(AASHTO A-2-6)

ALLUVIUM:

Light brown, moist, very stiff, sandy lean CLAY.

(AASHTO A-6)

Yellow to light brown, moist, medium dense, SAND with clay.

Fine to coarse.

Total Depth = 10 feet.

Groundwater not encountered during drilling.

Backfilled with on-site soil shortly after drilling on 10/29/15.

Note: Groundwater, though not encountered at the time of drilling, may rise to a higher level due to seasonal variations in precipitation and several other factors as discussed in the report.

The ground elevation shown above is an estimation only.