Atch_15_Geotech_Report-NBFFCC_2015-0416.pdf

800 Stockton Avenue Fort Collins, CO 80524 phone: (970) 916-9045 fax: (303) 742-9666 email: kaftcollins@kumarusa.com www.kumarusa.com

Office Locations: Denver (HQ), Colorado Springs, Fort Collins, and Frisco, Colorado

GEOTECHNICAL ENGINEERING STUDY

SOIL SWELL/COLLAPSE POTENTIAL

NATIONAL BLACK-FOOTED FERRET CONSERVATION CENTER

19180 FRONTAGE ROAD

CARR, COLORADO

RFQ: F15PS00305

ORDER NO.: F15PX00837

Prepared By: Reviewed By:

Joshua L. Barker, P.E

Wade Gilbert, P.E.

Prepared For:

U.S. Fish and Wildlife Service, Region 6 P.O. Box 25486

Denver Federal Center Denver, CO 80225

Attention: Mr. Steve Gess

Project No. 15-3-118 April 16, 2015 http://www.kumarusa.com/

TABLE OF CONTENTS

PURPOSE AND SCOPE OF STUDY

PROJECT UNDERSTANDING

SITE CONDITIONS

SUBSURFACE CONDITIONS

LABORATORY TESTING

FLOOR SLAB HEAVE CONSIDERATIONS

QUARANTINE AND HOLDING BUILDING CONSIDERATIONS

HOLDING PEN CONSIDERATIONS

LIMITATIONS

FIGS. 1 and 1A – LOCATIONS OF EXPLORATORY BORINGS

FIG. 2 – LOGS OF EXPLORATORY BORINGS

FIG. 3 – LEGEND AND NOTES

FIGS. 4 through 16 – SWELL-CONSOLIDATION TEST RESULTS

TABLE I – SUMMARY OF LABORATORY TEST RESULTS

Kumar & Associates, Inc.

PURPOSE AND SCOPE OF STUDY

This report presents the results of a geotechnical engineering study at the National Black-

Footed Ferret Conservation Center located at 19180 Frontage Road in Carr, Colorado. The study was conducted for the purpose of evaluating the swell potential of treated soils below the quarantine and holding buildings at the site as well as the collapse potential of untreated natural soils near the outdoor conditioning pens. This study was performed in general accordance with our Proposal No. P3-15-133 to the U.S. Fish and Wildlife Service, Region 6 dated March 31, 2015.

A field exploration program consisting of exploratory borings was conducted to obtain information on subsurface conditions. Samples of the soils and bedrock obtained during the field exploration program were tested in the laboratory to determine their classification and engineering characteristics. The results of the field exploration and laboratory testing programs were analyzed to develop geotechnical engineering considerations for use in evaluating the swell potential of the on-site soils and for the collapse potential of ferret burrows on the site.

This report has been prepared to summarize the data obtained during this study and to present our conclusions based on the subsurface conditions encountered. Discussions of geotechnical engineering considerations related to the project site are included in the report.

PROJECT UNDERSTANDING

Two existing buildings at the project site have experienced deformation of foundations and floor slabs after construction due to heave-related movement from underlying expansive soils. The soils underlying the buildings and around the perimeter of the buildings were subsequently treated with an ionized liquid (EcSS 3000) to stabilize the soils and prevent further deformation.

A purpose of this geotechnical engineering study is to evaluate the swell potential of the treated soils.

As part of the statement of work (SOW) for the project, an optional scope item was requested and subsequently approved. The optional scope item added evaluation of the soils at four locations in the area of the conditioning pens. Prior to release in the wild, ferrets are released into outdoor conditioning pens to learn to live in burrows and to hunt their prey. The collapse of burrows and subsequent loss of ferrets is a risk to the success of the breeding program, and information regarding the cohesiveness and resistance to collapse of the in-situ soil is necessary for reducing the risk of loss of ferrets. Soils in the conditioning pen areas have not been treated with ionized liquid.

If the project understanding varies significantly from that generally described above or depicted throughout this report, we should be notified to reevaluate the recommendations provided herein.

SITE CONDITIONS

At the time of our field exploration program, the site was developed with numerous single-story structures. The structures of concern in this study were the holding and quarantine buildings.

Also included in the study were the conditioning pens, which are located immediately east of the holding building. The two buildings are single-story structures with slab-on-grade concrete floors. The buildings appeared to consist of wood-framed structures supported on foundation stem-walls. We were not provided with information regarding the foundation system used to support the structures, although information provided in the SOW suggests that heave-related foundation movement has occurred, which would imply that the buildings are on shallow foundations.

The overall site slopes gently down to the south and west. Portions of the site not covered by buildings or gravel drive lanes were covered with low growing weeds and grasses. Areas away from the buildings and conditioning pens were occupied by Prairie Dog burrows.

Building Condition: Although not part of our scope of work, we performed a brief observation of the condition of the existing buildings while performing our study. The exterior of the buildings appeared to be generally intact with little sign of distress. The interior walls of the buildings were covered with drywall wall, which showed signs of relatively severe distress in the form of large cracks at the wall corners.

We also observed that the floor slabs had significant cracking. The holding building floor slab appeared to show signs of heave movement with the most movement appearing to have occurred near the center of the building. We did not perform a level survey to confirm that condition. Also, where the floor slabs adjoined the building foundation walls, it appeared that significant upward vertical movements have occurred. Much of the baseboard had been destroyed and/or removed.

SUBSURFACE CONDITIONS

Information on the subsurface conditions was obtained by drilling a total of eleven exploratory borings at the approximate locations shown on Figs. 1 and 1A. Graphic logs of the borings are presented on Fig. 2, and a legend and notes describing the soils encountered is presented on

Fig. 3.

Quarantine Building and Holding Building: The concrete floor slab was cored at two locations within each building for a total of four core locations. The concrete was cored using a 4-inch-diameter diamond-impregnated barrel. The floor slab thickness in the two buildings ranged from about 4.25 to 5.75 inches. A heavy duty vapor barrier was encountered below the concrete in both buildings. A thin layer of foam material was encountered between the floor slab and the vapor barrier in the quarantine building. The foam appeared to have a maximum thickness of about ¼-inch. We do not have the information on the type or purpose of the foam material.

Based on our observations, the foam had a consistency similar to a cured urethane product.

Borings were excavated at the four boring locations inside of the structures utilizing hand powered augering and sampling equipment. After sampling, the borings were backfilled and patched with concrete mixed on-site.

The interior borings (Borings 3, 4, 6 and 7) encountered about 4 to 7 feet of man-placed fill material overlying natural clay overburden soils. The natural soils continued to the explored depths of about 9 feet in Borings 3 and 4 (Holding Building). The natural soils were underlain by claystone bedrock in Borings 6 and 7 (Quarantine Building). The claystone bedrock was encountered at depths of about 7 feet in both borings and continued to the explored depths of about 9 feet.

The borings drilled adjacent to the existing buildings (Borings 1, 2, and 5) encountered a thin veneer of topsoil overlying nil to about 4 feet of man-placed fill material. The fill material was underlain by natural clay overburden soils. The natural soils continued to the explored depths of about 9 feet in Borings 1 and 2 (adjacent to the Holding Building) and to claystone bedrock in

Boring 5 (adjacent to the Quarantine Building). The claystone bedrock was encountered at a depth of about 7 feet and continued to the explored depth of about 9 feet.

Conditioning Pens: The four exploratory borings drilled within the conditioning pen area (Borings

8 through 11) encountered a thin veneer of topsoil overlying natural clay soils. The natural soils were underlain by claystone bedrock at depths ranging from about 3 to 6 feet below the ground surface. The bedrock continued to the explored depths of about 8 feet.

Material Description: The man-placed fill materials encountered on the site appeared to be reworked overburden materials either excavated on site or imported from a nearby source. The lateral and vertical extents of the fill or the compaction level was not determined as part of this study. It was difficult to distinguish between the natural overburden soils and the man-placed fill materials in some of the areas. The overburden soils were predominantly clayey with occasional sand and gravel. The natural overburden soils were fine to medium grained, slightly moist to moist, and brown. Occasional calcareous deposits were noted in the samples. The bedrock on the site varied from claystone to siltstone with occasional sandstone interbeds and was fine to medium grained, slightly moist to moist, and light brown to brown to yellowish brown.

Based on sampler penetration resistance the natural overburden soils had consistencies ranging from stiff to hard, and the bedrock was weathered to medium hard. The bedrock had nil to weak cementation.

Groundwater was not encountered in the borings at the time of drilling or when measured 3 to 4 days after drilling.

LABORATORY TESTING

Laboratory test results are presented adjacent to the boring logs on Fig. 2 and are summarized in Table I.

Swell-Consolidation Testing: The results of swell-consolidation tests, presented on Figs. 4 through 16, indicate that the samples of the fill materials exhibited relatively low swell potential.

The samples of natural clay overburden soils generally exhibited low to very high swell potential.

The claystone bedrock generally exhibited low consolidation potential to low swell potential. The swell potential of each sample was measured when that sample was wetted under a constant surcharge pressure of 1,000 psf.

Based on conditions encountered below the existing floor slabs in both the quarantine and holding buildings, it appears that the fill materials within 3 to 4 feet of the bottom of the floor slabs possess low swell potential with an average swell potential of 0.6%. Fill and natural clay soils below those depths and within the explored depths possess moderate swell potential with average swell potentials of about 2.4% for samples obtained at a depth of 5½ feet and 2.8% for samples obtained at a depth of 8 feet.

The on-site materials encountered in the borings drilled on the exterior of the quarantine and holding buildings exhibited variable swell potential. The materials within 3 to 4 feet of the ground surface exhibited high swell potential with an average swell potential of 4.1%. Materials below that depth and within the explored depths had moderate swell potential with average swell potentials of about 2.8% for samples obtained at a depth of 5½ feet and 3.5% for samples obtained at a depth of 8 feet.

The moisture contents of the samples were variable. The average moisture content of the samples within 3 to 4 feet of the bottom of the floor slabs inside the buildings was 21.8%. Below those depths, the moisture contents were 15.4% and 17.7% for samples from 5½ and 8 feet, respectively. Samples from the borings drilled outside of the buildings had average moisture contents ranging from 14.4% to 17.8%

A summary of the swell testing results is presented below:

Sample Depth (ft)

Average Dry Density (pcf)

Average Moisture Content (%)

Average Swell Potential

Interior Borings*

Exterior Borings**

Interior Borings*

Exterior Borings**

Interior Borings*

Exterior Borings**

3 99.0 109.9 21.8 14.4 0.6 4.1

5.5 111.8 106.9 15.4 17.8 2.4 2.8

8 102.9 109.3 17.7 14.9 2.8 3.5

* Interior Borings include Borings 3, 4, 6, and 7 ** Exterior Borings include Borings 1, 2, and 5

The swell potential for the on-site soils and bedrock appear to be generally related to the in-situ moisture content and dry density. The materials with relatively low moisture contents and high dry densities generally exhibit the highest swell potential.

Unconfined Compressive Strength Testing: Unconfined compressive strength testing was performed on selected samples taken from the borings located within the conditioning pen area

(Borings 8 through 11). Three samples of the natural overburden soils had unconfined compressive strengths ranging from about 8,500 to 19,000 psf. Five samples of the claystone bedrock indicated unconfined compressive strengths ranging from about 3,000 to 8,400 psf.

We used the commonly accepted correlation procedure of taking one-half of the unconfined compressive strength as approximately equal to the cohesive strength of the soil. Therefore, the natural overburden soils exhibited cohesive strengths between about 4,250 and 9,500 psf.

Similarly, the claystone bedrock exhibited cohesive strengths between about 1,500 and 4,750 psf.

Material Classification: Material classification was not part of the scope of work for this project.

Based on visual observations in the field and laboratory, we believed that classification of the materials on the site would provide valuable information for evaluating the subsurface conditions. The overburden soils (natural and man-placed fill) generally classified as lean clay with sand to sandy lean clay. Some materials classifying as lean to fat clay were encountered.

The index properties are presented adjacent to the boring logs and summarized in Table I along with the material classifications.

FLOOR SLAB HEAVE CONSIDERATIONS

Heave estimate calculations cannot address the uncertainty in the potential depth and degree of wetting that may occur under a floor slab, or the variability of swell potential across a site, which is frequently erratic. We have performed calculations to demonstrate the potential for slab movement if the underslab soils should be thoroughly wetted to a depth of about 10 feet below the floor slab. The following table presents estimates of potential heave based on the results of the swell-consolidation tests using test and analysis methods generally accepted in the

Colorado Front Range.

SLAB HEAVE IN INCHES

5 feet of wetting 10 feet of wetting

1.5 3.5

Heave estimates for the ground surface outside of the buildings varied from about 4 inches to more than 6 inches.

The heave estimate calculations demonstrate the approximate potential magnitude of heave that could occur if wetting of the underslab soils occurs. It should be noted that the heave estimates were limited to a maximum depth of wetting 10 feet, which is slightly deeper than our exploratory borings were excavated. Wetting depths can exceed 10 feet in some circumstances; however, we are not able to provide reasonably accurate estimates of heave for wetting greater than 10 feet without further subsurface data.

QUARANTINE AND HOLDING BUILDING CONSIDERATIONS

It has been our experience that buildings that exhibit slab heave movements frequently experience damage to buried utilities. The damage can be bent or broken pipes or drainpipes with joints that have become loose or separated. Damaged pipes can provide a direct source of water to subsurface soils, which can exacerbate the heaving movements of the floor slabs. We recommend that the sewer lines within the building be inspected using camera techniques to find potential damage to the pipes.

The unpaved exterior ground surface surrounding the Holding Building appeared to the sloping down and away from the sides of the structure. Additionally, the roof downspouts emptied into corrugated drainpipes that allowed rain water or snowmelt to be discharged well away from the structure.

The Quarantine Building was surrounded by bare soil on all four sides of the building, with the exception of a small concrete apron in front (south side) of the building. The ground surface in front of the apron sloped moderately down and away from the building. The east and west sides of the building had ground surfaces with very shallow slopes down and away from the building. The Quarantine Building site appeared to be cut into the natural hillside with the north side of the building at the upslope side of the site. The north side of the building had a near zero to a very shallow slope down and away from the building, which led to a moderate upward slope to the north. It appeared that surface runoff water from north of the building could flow toward the building foundation. The Quarantine Building roof downspouts were configured similar to the Holding Building downspouts in that the flows were taken from the downspout to discharge points away from the structure via black corrugated pipe.

We recommend re-grading the ground surface surrounding the Quarantine Building to provide more positive surface drainage away from the structure to help prevent ponding of water adjacent to the foundations. Additionally, consideration should be given to providing a low height berm or other water diversion feature on the upslope side of the Quarantine Building to prevent surface water from accumulating near the building.

HOLDING PEN CONSIDERATIONS

As discussed above, the four borings drilled within the area of the conditioning pens (Borings 8 through 11) encountered a thin veneer of topsoil overlying natural clayey soils. The natural soils were underlain by claystone bedrock at depths ranging from about 3 to 6 feet below the ground surface. The bedrock continued to the explored depths of about 8 feet. The estimated unconfined compressive strengths and cohesion values of the overburden soils and bedrock are discussed above.

The unconfined compressive strength testing was performed on samples of the materials in their in situ condition. The in situ moisture contents were relatively low. Depending on changes in the moisture content, the shear strengths can fluctuate significantly. When evaluating the strength data along with blow count data obtained from the field sampling, it appears that the in situ soils and bedrock represent a low likelihood of massive burrow collapse from natural conditions. The general area of the site is located within a low seismic activity zone; therefore, there is a low likelihood of collapse related to seismically induced ground motion. Vehicles or equipment operating on or immediately adjacent to the burrows could have the potential to apply a surcharge pressure or vibrations sufficient to induce collapse conditions. It is unlikely that vehicles or equipment operated more than about 15 feet away from the burrows will have a noticeable effect on the integrity of the burrows.

Periods of heavy precipitation that flood the burrows may temporarily reduce the shear strength of the soils and bedrock due to an increase in moisture content; however, it is considered unlikely that the reduction in shear strength would be sufficient to cause a burrow to completely collapse. It is more likely that there would be short-term localized sloughing of the burrow wall materials.

LIMITATIONS

This study has been conducted in accordance with generally accepted geotechnical engineering practices in this area for exclusive use by the client. The conclusions and discussions submitted in this report are based upon the data obtained from the exploratory borings at the locations indicated on Fig. 1 and from the laboratory test results. This report may not reflect subsurface variations that occur between the exploratory borings. Kumar & Associates, Inc. is not responsible for liability associated with interpretation of subsurface data by others.

JLB/ap cc: book, file

Project No.: 15-3-118

Project Name: United States Fish and Wildlife Black-footed Ferret Conservation Center; Carr, Colorado

Date Sampled: April 6 and 7, 2015

Date Received: April 8, 2015

Boring Depth (Feet)

Liquid Limit

Plasticity

1 3 4/8/15 13.5 116.9 Lean Clay with Sand (CL)

1 5.5 4/8/15 23.5 94.8 Lean Clay with Sand (CL)

1 8 4/8/15 18.6 109.1 92 50 27 Fat Clay (CH)

2 3 4/8/15 14.0 113.6 72 39 20 Lean Clay with Sand (CL)

2 5.5 4/8/15 12.1 118.2 Lean Clay with Sand (CL)

2 8 4/8/15 10.8 121.1 Lean Clay with Sand (CL)

3 3 4/8/15 22.7 98.3 Fill: Lean Clay with Sand (CL)

3 5.5 4/8/15 17.1 106.0 65 39 23 Fill: Sandy Lean Clay (CL)

3 8 4/8/15 24.9 97.6 Lean Clay with Sand (CL)

4 3 4/8/15 22.2 98.2 Fill: Lean Clay with Sand (CL)

4 5.5 4/8/15 18.2 109.5 69 43 26 Sandy Lean Clay (CL)

4 8 4/8/15 15.3 111.0 Lean Clay with Sand (CL)

5 3 4/8/15 15.6 110.9 86 48 31 Lean Clay (CL)

5 5.5 4/8/15 17.9 99.1 Lean Clay with Sand (CL)

5 8 4/8/15 15.4 107.7 42 39 18 Sandstone Bedrock

6 3 4/8/15 21.7 97.7 72 48 30 Fill: Lean Clay with Sand (CL)

6 5.5 4/8/15 12.9 117.5 Lean Clay with Sand (CL)

6 8 4/8/15 10.4 105.2 Claystone Bedrock

7 3 4/8/15 20.6 101.7 Fill: Lean Clay with Sand (CL)

7 5.5 4/8/15 13.5 114.2 70 43 25 Lean Clay with Sand (CL)

7 8 4/8/15 20.2 97.9 Claystone Bedrock

8 1 4/8/15 11.3 100.3 58 46 25 8,500 Sandy Lean Clay (CL)

8 5 4/8/15 14.4 111.5 85 51 28 19,000 Fat Clay with Sand (CL)

9 5 4/8/15 11.2 97.9 86 43 24 Lean Clay (CL)

9 7 4/8/15 12.4 109.2 97 48 26 5,200 Claystone Bedrock

10 1 4/8/15 17.1 105.6 51 42 21 Sandy Lean Clay (CL)

10 7 4/8/15 13.0 106.8 56 31 8 7,100 Claystone Bedrock

11 1 4/8/15 10.0 97.1 63 39 20 7,700 Sandy Lean Clay (CL)

11 3 4/8/15 21.8 91.7 81 36 15 3,000 Claystone Bedrock

11 5 4/8/15 13.2 106.5 90 50 29 8,400 Claystone Bedrock

11 7 4/8/15 12.6 105.7 89 38 21 5,600 Claystone Bedrock

Soil or Bedrock Type

Summary of Laboratory Test Results

Table I

Sample Location Atterberg Limits

Date Tested

Natural

Moisture

Content (%)

Natural Dry

Density (pcf)

Percent

Passing No.

200 Sieve

Unconfined

Compressive

Strength (psf)