58767GE LPC Detention Center Pavement_FINAL.pdf

Durango and Cortez, Colorado 970.259.5095

GEOTECHNICAL ENGINEERING STUDY

FOR PAVEMENT SECTION THICKNESS DESIGN

LA PLATA COUNTY DETENTION CENTER

742 TURNER DRIVE

DURANGO, COLORADO

April 10, 2025

PREPARED FOR:

Blaine Montgomery

Assistant Director

La Plata County General Services

235 Bodo Drive

Durango, Colorado 81303 bmontgomery@lpcgov.org

PROJECT NO. 58767GE

mailto:bmontgomery@lpcgov.org

Project No. 58767GE

Table of Contents

1.0 REPORT INTRODUCTION

1.1 Proposed Construction

2.0 FIELD STUDY

2.1 Site Description and Geomorphology

2.2 Subsurface Soil and Water Conditions

3.0 LABORATORY STUDY

4.0 PAVEMENT SECTION THICKNESS DESIGN RECOMMENDATIONS

4.1 Existing Asphalt Pavement Evaluation

4.2 Asphalt Pavement Design Recommendations

4.3 General Asphalt Pavement Recommendations

5.0 SUBGRADE STABILIZATION RECOMMENDATIONS

6.0 CONSTRUCTION CONSIDERATIONS

6.1 Fill Placement Recommendations

6.1.1 Natural Soil Fill

6.1.2 Granular Compacted Structural Fill

6.2 Excavation Considerations

6.3 Grading and Drainage Comments

7.0 CONSTRUCTION MONITORING AND TESTING

8.0 CONCLUSIONS AND CONSIDERATIONS

9.0 LIMITATIONS

LABORATORY TEST RESULTS ....................................................................................................... Appendix A

Sieve and Atterberg Limit Test Results

Moisture/Density Relationship Test Results

California Bearing Ratio Test Results

April 9, 2025

1.0 REPORT INTRODUCTION

This report presents our geotechnical engineering recommendations for the proposed drive lane pavement rehabilitation project at the existing La Plata County Detention Center in Durango, Colorado. This report was requested by Blaine Montgomery of the La Plata County General

Services Department and was prepared in accordance with our proposal dated March 10, 2025, Proposal No. 25073P.

As outlined within our proposal for services for this project, the client is responsible for appropriate distribution of this report to other design professionals and/or governmental agencies unless specific arrangements have been made with us for distribution.

This geotechnical engineering report is the beginning of a process involving the geotechnical engineering consultant on any project. It is imperative that the geotechnical engineer be consulted throughout the design and construction process to verify the implementation of the geotechnical engineering recommendations provided in this report. Often the design has not been started or has only been initiated at the time of the preparation of the geotechnical engineering study. Changes in the proposed design must be communicated to the geotechnical engineer so that we have the opportunity to tailor our recommendations as needed based on the proposed site development and structure design.

All recommendations provided within this report must be followed in order to achieve the intended performance of the foundation system and other components that are supported by the site soil.

1.1 Proposed Construction

The project consists of evaluation of the drive lane on the south, east and west side of the existing

Detention Center.

2.0 FIELD STUDY

2.1 Site Description and Geomorphology

The project site is located at the northwest corner of the Bodo area of Durango, Colorado. A site location schematic is provided below as Figure 1.

Figure 1: Site Location Schematic. Adapted from Google Earth (Imagery Date 8/1/2024).

The La Plata County Detention Center consists of two main structures that are connected via a narrow breezeway. The original structure was constructed in 1975 and the north wing addition was constructed in 2008. The site consists of an asphalt paved drive lane along the west, south and east sides of the site. There is also an asphalt paved parking lot west of the original structure.

Evaluation of the parking lot is not included in this study. The pavement can be generally characterized as being in poor condition with moderate to severe cracking of various types, pothole patching and rutting in some locations. Photographs of the existing pavement conditions are provided below.

Photograph 1: View of patched area near detention center entrance that showing continued signs of distress and rutting.

Photograph 2: View of drive lane just west of entrance showing signs of patching, potholing and transverse and longitudinal cracking.

2.2 Subsurface Soil and Water Conditions

We advanced five test borings along the drive lane study area. A schematic showing the approximate boring locations is provided below as Figure 1. The logs of the soils encountered in our test borings are presented in the table below.

Figure 2: Locations of Exploratory Borings. Adapted from Google Earth (Imagery Date 8/1/2024).

The schematic presented above was prepared using notes and field measurements obtained during our field exploration and is intended to show the approximate test boring locations for reference purposes only.

The subsurface conditions encountered in our test borings consisted of 3 to 4 inches of asphalt overlying 6 to 11 ½ inches of approximate 1 inch minus aggregate base course (ABC). Beneath the 1 inch minus ABC, 4½ to 7 inches of 3 inch minus ABC was encountered. The subgrade soils beneath the ABC consisted of medium stiff lean clay (CL) and dense to very dense clayey gravel with sand (GC).

We did not encounter free subsurface water in our test borings at the time of the advancement.

We suspect that the subsurface water elevation and soil moisture conditions will be influenced by snow melt and/or precipitation and local irrigation.

The logs of the subsurface soil conditions encountered in our test borings are presented in the table below. The logs present our interpretation of the subsurface conditions encountered in the test borings at the time of our field work. Subsurface soil and water conditions are often variable across relatively short distances. It is likely that variable subsurface soil and water conditions will be encountered during construction. Laboratory soil classifications of samples obtained may differ from field classifications.

TABLE 1 – SUBSURFACE CONDITIONS SUMMARY TABLE

3.0 LABORATORY STUDY

The laboratory study included tests to estimate the strength, swell and consolidation potential of the soils tested. We performed the following tests on select samples obtained from the test borings.

Test

Boring#

Asphalt

Depth

ABC

Depth

(1” minus)

ABC Thickness

(3” minus)

Subgrade Soil Type and

Thickness

Sample Type and Depth Comments

TB-1 0-4” 4-10” 10-17”

Lean Clay (CL); medium stiff, moist, brown to grey.

17-48”

Bag samples:

4-10”, 10-17”, 17-48”

Cal @ 48”

(4/6, 4/6)

TB-2 0-3.5” 3.5-12” 12-15”

Lean Clay (CL); medium stiff, moist, brown to grey.

12-51”

Bag samples:

3.5-12”, 15-

51”

TB-3 0-3” 3-12” 12-19”

Lean Clay (CL); medium stiff, moist, brown to grey.

19-51”

Bag samples:

3-12”, 12-19”, 19-51”

Cal @ 51” 5/6, 7/6

TB-4 0-3.5” 3.5-14” 14-21”

Clayey Gravel with

Sand; dense to very dense, moist to very moist, brown.

21-50”

Bag samples:

0-3.5”, 3.5-

14”, 14-21”, 21-50”

Cal @ 50”

28/6, 25/6

-Possible pit run fill from 21-

62”

TB-5 0-4” 4-12” 12-16.5”

Clayey Gravel with

Sand; dense, moist, brown to grey.

16.5-50”

Bag samples:

0-4”, 4-12”, 12-16.5”, 16.5-50”

Std @ 50”

19/6, 25/6, 19/6

-Possible pit run fill from 21-

68”

The laboratory test results are provided in Appendix A.

• Moisture Content and Dry Density

• Sieve Analysis (Gradation)

• Atterberg Limits, Liquid Limit, Plastic Limit and Plasticity Index

• Moisture Content Dry Density Relationship Test

• California Bearing Ratio Test

A synopsis of some of our laboratory data for some of the samples tested is tabulated below.

Sample

Designation

Percent

Passing

#200

Sieve

Atterberg

Limits

LL/PI

Moisture

Content

Maximum

Modified

Proctor Dry

Density

(pcf)

Optimum

Moisture

Content

California

Bearing

Ratio

TB-2 @ 3.5-

12”

17.6 22/8 3.9 - - -

TB-3 @ 3-12” 19.8 21/6 5.0 - - -

TB-5 @ 4-12” 20.1 20/5 5.1 - - -

Bulk Subgrade 66.3 37/21 6.2 129.5 9.9 2.1

Notes:

1. Modified Proctor Dry Density and Optimum Moisture based on rock corrected test results.

2. California Bearing Ratio based on 90% of the Maximum Proctor Dry Density.

4.0 PAVEMENT SECTION THICKNESS DESIGN RECOMMENDATIONS

Based on the subsurface information and surface observations, we do not feel a mill and overlay, or fabric with overlay are feasible while keeping the existing asphalt elevation the same. Milling of the existing asphalt would likely result in excessive breakdown. Further, the overlay would have an increased risk of reflection cracking and premature deterioration.

We have provided a general analysis of the existing condition and current structural number values of the existing pavement section in Section 4.1 below. Our asphalt pavement recommendations are presented in Section 4.2. General asphalt pavement recommendations are presented in Section 4.3.

4.1 Existing Asphalt Pavement Evaluation

This section of the report provides an analysis for the structural number of the existing asphalt pavement section. Our analysis is intended to be general in nature as it is based on limited field and laboratory data and is intended to provide a baseline structural number for the subsurface conditions encountered that can be utilized for the design recommendations provided in Section

4.2 below. The following analysis should be considered valid only for the portion of the project area outlined in Section 1.1 of this report.

Based on our observations of the existing asphalt pavement surface, we feel that the existing asphalt pavement in the project area may be considered as being in poor condition. We observed localized areas on the roadway surface where moderate to severe alligator cracking, potholing/patching, rutting and longitudinal and transverse cracking has occurred in the pavement surface. We suspect that the distressed area is related to the age of the pavement section, poor drainage, freeze-thaw, and structurally deficient sections of asphalt pavement for the existing traffic loading.

Due to the condition of the existing asphalt surface, we have assumed the existing asphalt will be removed and replaced with a new asphalt mat overlying the existing aggregate support materials.

Based on our subsurface exploration the ABC ranged in thickness from about 6 to 10½ inches thick with an average of about 8 inches. The aggregate sub-base ranged from about 3 to 7 inches thick with an average of about 5 inches. Assuming the existing asphalt will be removed, the existing support materials have a structural number (SN) of 1.33.

4.2 Asphalt Pavement Design Assumptions

Traffic projections and corresponding 18,000-pound (18k) equivalent single axel load (ESAL) factors were not available at the time of this report. We have provided conceptual pavement section thickness recommendations for an assumed 100,000 ESALs based on anticipated traffic loading. The estimated ESAL assumes a two-way average daily traffic count of 250 with a growth rate of 2 percent and 5 percent truck traffic (1.7 ESAL/truck) over a 20-year pavement design period. If higher ESAL values are anticipated or if alternative recommendations are required, the pavement sections presented in this report should be re-evaluated.

We performed a California Bearing Ratio (CBR) test on a composite sample of soil obtained from the project site. Based on the laboratory analysis, a CBR value of 2.1 was obtained for the on-site soils, which roughly correlates to an R-Value of 5 and an resilient modulus of 3,025 pounds per square inch. The CBR results are provided in Appendix A. Other assumptions made for our analysis are listed below.

• Reliability Factor R(%) = 85%

• Overall Standard Deviation, So = 0.44

• Estimated Total 18K-ESAL value(s) = 100,000

• Effective Roadbed Soils Resilient Modulus, Mr = 4,334

• Change is serviceability index, Delta PSI = 2.5

• Structural Coefficient of Asphalt Pavement = 0.44

• Structural Coefficient of Aggregate Base Course = 0.11

• Average Aggregate Base Course Thickness = 8 inches

• Structural Coefficient of Aggregate Sub-Base Course = 0.09

• Average Aggregate Sub-Base Thickness = 5 inches

• Modifying Structural Layer Coefficients for aggregate base course and aggregate sub-base course layers, mi = 1.0 (fair drainage conditions with 5%-25% saturation frequency)

We have estimated a pavement reliability factor (R) of 85 percent. The Federal Highway

Administration defines R as “the probability that a pavement section will perform satisfactorily over the design period. It must account for uncertainties in traffic loading, environmental conditions, and construction materials. The AASHTO design method accounts for these uncertainties by incorporating a reliability level R to provide a factor of safety into the pavement design and thereby increase the probability that the pavement will perform as intended over its design life.” A higher R will result in thicker pavement section materials; however, may lead to a greater reliability in the pavement performance. The designer or project civil engineer should evaluate the desired R factor for the intended use. We can provide alternate reliability factors for the proposed pavement section upon request.

4.3 Asphalt Pavement Design Recommendations

Based on the above assumptions and laboratory test data obtained for the native on-site soil materials, we obtained a structural number (SN) equal to 3.04 for an assumed 100,000 18k-ESAL.

The existing asphalt is proposed to be removed due to the deteriorated condition; however, the existing aggregate support materials will remain in place. As discussed above, the existing support materials have a SN of 1.33. We recommend scarification and recompaction of the upper approximately 6 inches of the existing ABC followed by placement of a new 4 inch asphalt surface which will equate to a total SN of 3.09, which is sufficient for the anticipated traffic loading. We do not recommend an asphalt mat of less than 4 inches as the thicker mats will be more resilient and able to withstand the rigors associated with exposure to heavy equipment or truck traffic and will allow for a mill and overlay for future maintenance.

4.4 General Asphalt Pavement Recommendations

The asphalt pavement used on this project should be mixed in accordance with a design prepared by a licensed professional engineer, or an asphalt pavement specialist. We should be contacted to review the mix design prior to placement at the project site. We recommend that the asphalt pavement be compacted to between 92 and 96 percent of the maximum theoretical density.

We suspect that the subgrade soils will be well above the optimum moisture content in many areas of the project. We anticipate that conventional scarification and drying of the subgrade soils will be sufficient for most areas of the roadway subgrade provided warm and preferably breezy weather conditions are present during the project construction, and there is adequate time to perform scarification and drying construction procedures. However, it is likely that some areas of the subgrade will require specialty stabilization techniques. We have provided cursory recommendations for stabilization of severely yielding soil materials in Section 5.0 below.

The existing support soils should be scarified to a depth of about 6 inches, moisture conditioned, and compacted to at least 90 percent of the maximum dry density as defined by ASTM D1557 or

AASHTO T180 (Modified Proctor). Proof rolling observations should then be performed over the prepared subgrade surface. Any areas of significant yielding should be stabilized as needed prior to placement of the overlying aggregate base course materials. The surface of the subgrade soil should be graded and contoured to be approximately parallel to the finished grade of the asphalt surface.

The aggregate materials used within the pavement section should conform to the requirements outlined in the current Specifications for Road and Bridge Construction, Colorado Department of

Transportation (CDOT). The aggregate base material should be a ¾ inch minus material that conforms to the CDOT Class 6 aggregate base course specifications and have an R-value of at least 78. The aggregate sub-base course should conform to the CDOT specifications for Class 2 material and should have a minimum R-value 70. Other material may be suitable for use in the pavement section, but materials different than those listed above should be tested and observed by us prior to inclusion in the project design or construction. Aggregate sub-base and base-course materials should be compacted to at least 95 percent of maximum dry density as defined by the modified Proctor test, ASTM D1557.

Thorough proof rolling with a fully loaded tandem axle water truck should be performed across the prepared aggregate surface prior to placement of the asphalt cement. Any areas that are observed to yield should be stabilized as necessary. We should be contacted to observe the proof rolling operations and provide recommendations for stabilization if necessary.

Water intrusion into the pavement section support materials will negatively influence the performance of the parking lot surface. Water from irrigation, water from natural sources that migrates into the soils beneath landscapes surface and water from any source that gains access to the support materials can all decrease the life of the parking lot surface. Care should be taken along curbs and any edge of the parking lot to develop an interface between the material that will reduce subsurface and surface water migration into the support soil and pavement section materials. Landscape islands and other irrigated features often promote water migration since no surface flow from these features typically occurs. The same can occur along perimeter cub areas.

Water will often migrate along the interface of concrete curbs and gutter areas early in the life of any parking area. The tendency for this type of migration often decreases with time but can be reduced by compaction of materials along the outside base of curb areas adjacent to the interface of the concrete curb and the underlying soil prior to placement of landscaping soil above this interface. The drainage characteristics of the roadway should be addressed by the project civil engineer.

5.0 SUBGRADE STABILIZATION RECOMMENDATIONS

We anticipate that stabilization of the subgrade materials may be required in some areas of the project. The actual stabilization design will need to be determined on a case-by-case basis as the design will be influenced on the degree of yielding at a particular area. We have provided a stabilization technique for subgrade soils that exhibit severe yielding below. This stabilization technique may be useful as a bid item for the project; however, we should provide continued consultation and observations during construction to provide site-specific recommendations.

A general construction concept for the stabilization of severely yielding subgrade soils is provided below.

• The subgrade soils should be over-excavated below the project subgrade elevation by one

1 foot. The soils should be proof-compacted with non-vibratory methods if excessive moisture is present.

• A layer of geogrid material such as Tensar BX 1100 or TX 140 should be placed in the bottom of the excavation.

• A 1-foot layer of crushed, relatively clean aggregate material should then be placed over the grid in at least two lifts. The crushed aggregate material should pass through a 2-inch sieve screen and have less than 5 percent passing the #4 sieve screen. The clean aggregate material should be compacted with non-vibratory methods.

• A geotextile fabric such as Mirafi 140N should then be placed over the clean crushed aggregate material to limit the potential for fines migration into the crushed aggregate layer.

• The initial approximate 6- to 8-inch-thick lift of the actual pavement design support section should then be placed and compacted per our recommendations.

We anticipate that less robust stabilization techniques may be applicable for many areas of the project. As discussed above, the actual stabilization technique will need to be based on a case-by-case basis.

6.0 CONSTRUCTION CONSIDERATIONS

The section of the report provides comments, considerations, and recommendations for aspects of the site construction which may influence, or be influenced by the geotechnical engineering considerations discussed above. The information presented below is not intended to discuss all aspects of the site construction conditions and considerations that may be encountered as the project progresses. If any questions arise as a result of our recommendations presented above, or if unexpected subsurface conditions are encountered during construction we should be contacted immediately.

6.1 Fill Placement Recommendations

There are several references throughout this report regarding both natural soil and compacted structural fill recommendations. The recommendations presented below are appropriate for the fill placement considerations discussed throughout the report above.

All areas adjacent to the existing asphalt roadway that will receive fill or other site improvements should be properly prepared and grubbed at the initiation of the project construction. The grubbing operations should include scarification and removal of organic material and other unsuitable materials.

We observed evidence of previous site use and existing man-placed fill during our field work.

Existing embankment fills or existing utility trench backfill material should be thoroughly proof rolled to ensure that the existing fill material is suitable to support the new roadway section.

6.1.1 Natural Soil Fill

Any natural soil used for any fill purpose should be free of all deleterious material, such as organic material and construction debris. Natural soil fill includes excavated and replaced material or in-place scarified material.

The natural soils should be moisture conditioned, either by addition of water to dry soils, or by processing to allow drying of wet soils. The proposed fill materials should be moisture conditioned to between about optimum and about 2 percent above optimum soil moisture content. This moisture content can be estimated in the field by squeezing a sample of the soil in the palm of the hand. If the material easily makes a cast of soil which remains in-tact, and a minor amount of surface moisture develops on the cast, the material is close to the desired moisture content.

Material testing during construction is the best means to assess the soil moisture content.

Moisture conditioning of clay or silt soils may require many hours of processing. If possible, water should be added and thoroughly mixed into fine grained soil such as clay or silt the day prior to use of the material. This technique will allow for development of a more uniform moisture content and will allow for better compaction of the moisture conditioned materials.

The moisture conditioned soil should be placed in lifts that do not exceed the capabilities of the compaction equipment used and compacted to at least 90 percent of maximum dry density as defined by ASTM D1557, modified Proctor test. We recommend a maximum fill lift thickness of

6 inches for hand operated equipment and 8 to 10 inches for larger equipment. Care should be exercised in placement of utility trench backfill so that the compaction operations do not damage the underlying utilities.

6.1.2 Granular Compacted Structural Fill

Granular compacted structural fill or aggregate base course is referenced in numerous locations throughout the text of this report. We recommend that aggregate base course materials conform to the Colorado Department of Transportation (CDOT) “Class 6” aggregate road base material, or

“Class 2” aggregate sub-base course material. This specification can include an option for testing and approval in the event the contractor’s desired material does not conform to the Class 6 or Class

2 aggregate specifications. All aggregate base course materials should be moisture conditioned and compacted to at least 95 percent of maximum dry density as defined by ASTM D1557, modified Proctor test.

6.2 Excavation Considerations

Unless a specific classification is performed, the site soils should be considered as an

Occupational Safety and Health Administration (OSHA) Type C soil and should be sloped and/or benched according to the current OSHA regulations. Excavations should be sloped and benched to prevent wall collapse. Daily observations of the excavations should be conducted by OSHA competent site personnel to assess safety considerations.

We did not encounter free subsurface water in our test borings. If water is encountered during construction, it may be necessary to dewater excavations to provide for suitable working conditions.

If possible, excavations should be constructed to allow for water flow from the excavation the event of precipitation during construction. If this is not possible it may be necessary to remove water from snowmelt or precipitation from the foundation excavations to help reduce the influence of this water on the soil support conditions and the site construction characteristics.

6.3 Grading and Drainage Comments

Many areas adjacent to the existing pavement alignment were observed to have relatively poor drainage characteristics and currently collect or pool water. The project civil engineering consultant should develop a drainage scheme for the project.

7.0 CONSTRUCTION MONITORING AND TESTING

Engineering observation of subgrade bearing conditions, compaction testing of fill material and testing of foundation concrete are equally important tasks that should be performed by the geotechnical engineering consultant during construction. We should be contacted during the construction phase of the project and/or if any questions or comments arise as a result of the information presented below. It is common for unforeseen, or otherwise variable subsurface soil and water conditions to be encountered during construction. As discussed in our proposal for our services, it is imperative that we be contacted to verify that the conditions encountered in our field exploration were representative of those encountered during construction. Our general recommendations for construction monitoring and testing are provided below.

• Consultation with design professionals during the design phases: This is important to ensure that the intentions of our recommendations are properly incorporated in the design, and that any changes in the design concept properly consider geotechnical aspects.

• Observation and monitoring during construction: A representative of the Geotechnical engineer from our firm should observe pavement subgrade to determine that subsurface conditions are compatible with those used in the analysis and design and our recommendations have been properly implemented. Placement of backfill should be observed and tested to judge whether the proper placement conditions have been achieved.

Compaction tests should be performed on each lift of material placed in areas proposed for support of structural components.

8.0 CONCLUSIONS AND CONSIDERATIONS

While we feel that it is feasible to improve and reconstruct the existing asphalt pavement as planned using relatively conventional techniques we feel that it is prudent for us to be part of the continuing design of this project to review and provide consultation in regard to the proposed development scheme as the project progresses to aid in the proper interpretation and implementation of the recommendations presented in this report. This consultation should be incorporated in the project development prior to construction at the site.

9.0 LIMITATIONS

This study has been conducted based on the geotechnical engineering standards of care in this area at the time this report was prepared. We make no warranty as to the recommendations contained in this report, either expressed or implied. The information presented in this report is based on our understanding of the proposed construction that was provided to us and on the data obtained from our field and laboratory studies. Our recommendations are based on limited field and laboratory sampling and testing. Unexpected subsurface conditions encountered during

04-10-25 construction may alter our recommendations. We should be contacted during construction to observe the exposed subsurface soil conditions to provide comments and verification of our recommendations.

The recommendations presented above are intended to be used only for this project site and the proposed construction which was provided to us. The recommendations presented above are not suitable for adjacent project sites, or for proposed construction that is different than that outlined for this study.

This report provides geotechnical engineering design parameters but does not provide asphalt pavement design. The civil engineering consultant must be contacted to provide a design based on the information presented in this report.

The findings of this report are valid as of the present date. However, changes in the conditions of the property can occur with the passage of time. The changes may be due to natural processes or to the works of man, on the project site or adjacent properties. In addition, changes in applicable or appropriate standards can occur, whether they result from legislation or the broadening of knowledge. Therefore, the recommendations presented in this report should not be relied upon after a period of two years from the issue date without our review.

We are available to review and tailor our recommendations as the project progresses and additional information which may influence our recommendations becomes available.

Please contact us if you have any questions, or if we may be of additional service.

Respectfully, Reviewed by, TRAUTNER GEOTECH

Jason A. Deem, P.G. Tom R. Harrison P.E.

Principal Geologist Principal Geotechnical Engineer

APPENDIX A

Laboratory Test Results

Tested By: N. Granda Checked By: G. Jadrych

3/12/2025

B.1

(no specification provided)

PL= LL= PI=

D90= D85= D60= D50= D30= D15= D10= Cu= Cc=

USCS= AASHTO=

GC - clayey gravel with sand 3/4" 1/2" 3/8" #4

#10 #40

#200

100.0 88.5 77.5 56.4 43.4 27.3 15.8

14 22 8

13.2920 11.5405 5.4837

3.3422 0.5765

GC A-2-4(0)

Blaine Montgomery, LaPlata County General Services

LaPlata County Detention Center

58767GE

Soil Description

Atterberg Limits

Coefficients

Classification

Remarks

Source of Sample: Test Boring #2 Depth: 3.5" - 12" Sample Number: 13369-E Date:

Client:

Project:

Project No: Figure

SIEVE PERCENT SPEC.* PASS?

SIZE FINER PERCENT (X=NO)

PE

R

C

EN

T

FI

N

ER

GRAIN SIZE - mm.

0.0010.010.1110100

% Stones % +3" Coarse Medium

% Gravel

Fine V. Crs. Crs. Med. Fine

% Sand

V. Fine Crs.

% Silt

Fine % Clay

0.0 0.0 0.0 43.6 13.0 8.0 6.7 5.4 5.7 17.6 in in in

½ in in

¾ in

½ in

3/ in

#4 #1

#2

#3

#4

#6

#1

#1

#2

Particle Size Distribution Report

B.2

(no specification provided)

PL= LL= PI=

D90= D85= D60= D50= D30= D15= D10= Cu= Cc=

USCS= AASHTO=

SC-SM - silty, clayey sand with gravel 3/4" 1/2" 3/8" #4

#10 #40

#200

100.0 90.0 82.7 64.8 51.2 32.4 17.4

15 21 6

12.6856 10.4269 3.6722

1.8313 0.3326

SC-SM A-1-b

Blaine Montgomery, LaPlata County General Services

LaPlata County Detention Center

58767GE

Soil Description

Atterberg Limits

Coefficients

Classification

Remarks

Source of Sample: Test Boring #3 Depth: 3" - 12" Sample Number: 13369-G Date:

Client:

Project:

Project No: Figure

SIEVE PERCENT SPEC.* PASS?

SIZE FINER PERCENT (X=NO)

PE

R

C

EN

T

FI

N

ER

GRAIN SIZE - mm.

0.0010.010.1110100

% Stones % +3" Coarse Medium

% Gravel

Fine V. Crs. Crs. Med. Fine

% Sand

V. Fine Crs.

% Silt

Fine % Clay

0.0 0.0 0.0 35.2 13.6 9.1 7.9 6.8 7.6 19.8 in in in

½ in in

¾ in

½ in

3/ in

#4 #1

#2

#3

#4

#6

#1

#1

#2

B.3

(no specification provided)

PL= LL= PI=

D90= D85= D60= D50= D30= D15= D10= Cu= Cc=

USCS= AASHTO=

SC-SM - silty, clayey sand with gravel 3/4" 1/2" 3/8" #4

#10 #40

#200

100.0 92.5 83.6 69.1 55.5 33.2 17.6

15 20 5

11.6335 9.9977 2.7004

1.3937 0.3175

SC-SM A-1-b

Blaine Montgomery, LaPlata County General Services

LaPlata County Detention Center

58767GE

Soil Description

Atterberg Limits

Coefficients

Classification

Remarks

Source of Sample: Test Boring #5 Depth: 4" - 12" Sample Number: 13369-Q Date:

Client:

Project:

Project No: Figure

SIEVE PERCENT SPEC.* PASS?

SIZE FINER PERCENT (X=NO)

PE

R

C

EN

T

FI

N

ER

GRAIN SIZE - mm.

0.0010.010.1110100

% Stones % +3" Coarse Medium

% Gravel

Fine V. Crs. Crs. Med. Fine

% Sand

V. Fine Crs.

% Silt

Fine % Clay

0.0 0.0 0.0 30.9 13.6 10.6 9.8 7.4 7.6 20.1 in in in

½ in in

¾ in

½ in

3/ in

#4 #1

#2

#3

#4

#6

#1

#1

#2

B.4

(no specification provided)

PL= LL= PI=

D90= D85= D60= D50= D30= D15= D10= Cu= Cc=

USCS= AASHTO=

CL - sandy lean clay 1.5" 1"

3/4" 1/2" 3/8" #4

#10 #40

#200

100.0 99.7 99.2 97.9 96.2 92.2 86.8 75.9 64.4

16 37 21

3.3224 1.5352

CL A-6(11)

Blaine Montgomery, LaPlata County General Services

LaPlata County Detention Center

58767GE

Soil Description

Atterberg Limits

Coefficients

Classification

Remarks

Location: Bulk subgrade Sample Number: 13369-U Date:

Client:

Project:

Project No: Figure

SIEVE PERCENT SPEC.* PASS?

SIZE FINER PERCENT (X=NO)

PE

R

C

EN

T

FI

N

ER

GRAIN SIZE - mm.

0.0010.010.1110100

% Stones % +3" Coarse Medium

% Gravel

Fine V. Crs. Crs. Med. Fine

% Sand

V. Fine Crs.

% Silt

Fine % Clay

0.0 0.0 0.8 7.0 5.4 4.8 4.9 4.7 6.1 66.3 in in in

½ in in

¾ in

½ in

3/ in

#4 #1

#2

#3

#4

#6

#1

#1

#2

Tested By: g. Jadrych Checked By: K. Moran

MOISTURE/DENSITY RELATIONSHIP

D ry d en si ty

, p cf

Water content, %

- Rock Corrected - Uncorrected

5 7.5 10 12.5 15 17.5 20

9.9%, 129.5 pcf

9.9%, 127.4 pcf

Test specification:

ASTM D4718-15 Oversize Corr. Applied to Each Test Point

ASTM D 1557-12 Method A Modified

CL A-6(11) 37 21 7.8 64.4

CL - sandy lean clay

58767GE Blaine Montgomery, LaPlata County General Services

SPG of rock:2.574 ABS of rock: 1.7% Rock corrected moisture:9.3%

B.5

Elev/ Classification Nat.

Sp.G. LL PI

Depth USCS AASHTO Moist. #4 No.200

ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION

Project No. Client: Remarks:

Project:

Date:

Location: Bulk subgrade Sample Number: 13369-U

Figure

127.4 pcf Maximum dry density = 129.5 pcf

9.9 % Optimum moisture = 9.9 %

LaPlata County Detention Center

California Bearing Ratio Test Results ASTM D-1883

Sample Date:

Start Soak: 3/24/2025

127.9 PCF End Soak: 3/28/2025

9.7 % Surcharge During Soak: 15 Lbs

Dry Density

(PCF)

Moisture

Content (%)

Relative

Compaction

Dry Density

(PCF)

Moisture Content of Top One (1)

Inch (%) Swell (%)

CBR (0.100"

penetration)

107.4 10.2 84.0% 100.8 23.8 4.3 0.9

115.0 8.8 89.9% 106.7 21.1 4.4 2.1

120.8 9.1 94.4% 112.1 19.0 4.5 3.1

2.1

LaPlata County Detention Center

3/12/202558767GE

Project Name:

Project Number:

California Bearing Ratio

@ 90% of Proctor Density:

Proctor Maximum Dry Density:

P. Terry

Bulk Subgrade

Pre-Soak: Post-Soak:

Optimum Moisure Content:

13369-U

Proctor Method:

Sample I.D.:

Sample Description:

Sample Source: Combined from all borings

D 1557 method A

Technician:

84.0%

89.9%

94.4% y = 0.1643x - 16.776 R² = 1

0.0

1.0

2.0

3.0

4.0

105.0 106.0 107.0 108.0 109.0 110.0 111.0 112.0 113.0 114.0 115.0 116.0 117.0 118.0 119.0 120.0 121.0 122.0 123.0

C a li fo rn ia B e a ri n g

R a ti o

C B

R

Dry Density (PCF)