MAP OF AREAS SUSCEPTIBLE TO

DIFFERENTIAL HEAVE IN STEEPLY DIPPING BEDROCK

DOUGLAS COUNTY, COLORADO

by

Marilyn D. Dodson ProQuest Number: 10781237

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A thesis submitted to the Faculty and the Board of Trustees of the Colorado School of

Mines in partial fulfillment of the requirements for the degree of Master of Engineering

(Geological Engineer).

Golden, Colorado

Date ~7J! 3- Jty b

Signed: Marilyn D. Qodson

Approved: DryJerry D. Higgins Tl/esis Advisor

Golden, Colorado

Date 7 / / $ / U

Dr. Roger M. Slatt Professor and Head, Department of Geology and Geological Engineering

11 ER-4645

ABSTRACT

Deformation of the ground surface caused by heaving bedrock has caused extensive damage to subdivisions and infrastructure along a narrow belt of steeply dipping sedimentary units that parallels the Front Range foothills west of Denver, Colorado. These units are dominated by thinly bedded claystones and shales. Each member of the rock sequence displays a different potential to expand due to varying clay mineralogy. Bedrock units are highly weathered near the ground surface and those containing expansive clays swell in the presence of water, which can result in differential movement at the surface at scales as small as a foot in width. The current state of practice for site investigations does not adequately determine where potential problems from differential bedrock heave may be encountered because of the high variability of bedrock composition. An engineering geologic map was constructed with the purpose of predicting areas susceptible to heaving bedrock hazards. Fourteen engineering units were identified on the basis of reconnaissance damage surveys of existing structures, engineering index properties established from geotechnical reports and laboratory testing, and the local and regional geology. Engineering units were ranked for potential for heaving bedrock hazards (low, moderate, or high) and then extrapolated into untested areas with the use of geologic and geomorphic interpretations. The resulting zonation of potentially heaving bedrock serves as an aid to engineers, developers, and planners involved in the design, construction, and regulation of development along the Front Range.

iii ER-4645

TABLE OF CONTENTS

Page

ABSTRACT...... iii

LIST OF FIGURES...... vii

LIST OF TABLES...... ix

LIST OF PLATES...... ix

ACKNOWLEDGMENTS...... x

1. INTRODUCTION...... 1

1.1 Problem Statement ...... 1 1.2 Purpose ...... 2 1.3 Objectives...... 2 1.4 Location ...... 3

2. BACKGROUND...... 5

2.1 Heaving Bedrock ...... 5

2.1.1 Steeply Dipping Bedrock ...... 8 2.1.2 Expansive Claystone or Bentonite ...... 9 2.1.3 Depth to Bedrock ...... 10 2.1.4 Fracturing, Weathering, and Water Infiltration ...... 11 2.1.5 Overconsolidation ...... 11

2.2 Geology and Engineering Geology ...... 13

2.2.1 Ralston Creek Formation ...... 16

iv ER-4645

2.2.2 Morrison Formation ...... 18 2.2.3 Lytle and South Platte Formations ...... 19 2.2.4 Graneros Shale, Greenhorn Limestone, and Carlile Shale ...... 20 2.2.5 Niobrara Formation ...... 27 2.2.6 Pierre Shale...... 31 2.2.7 Fox Hills Sandstone ...... 36 2.2.8 Laramie Formation ...... 36 2.2.9 Dawson Arkose ...... 37

3. METHODOLOGY...... 44

3.1 Criteria for Delineating Areas of Potentially Heaving Bedrock ...... 44 3.2 Bedrock Characteristics of Potentially Heaving Bedrock ...... 45 3.3 Survey of Damage Occurrence ...... 46

3.2.1 Selection of Survey Location ...... 47 3.2.2 Field Procedures...... 49 3.2.3 Damage Descriptions ...... 49 3.2.4 Damage Analysis ...... 54

3.4 Determining Engineering Properties of Geologic Units ...... 55

3.3.1 Selection of Sample Locations ...... 55 3.3.2 Sample Collection Procedures ...... 56 3.3.3 Field Descriptions ...... 57 3.3.4 Laboratory Testing Program ...... 57

3.5 Ranking Process ...... 64

4. RESULTS...... 66

4.1 Bedrock Characteristics of Potentially Heaving Bedrock ...... 66 4.2 Damage Survey Results ...... 69 4.3 Engineering Properties ...... 69

5. INTERPRETATION...... 74

5.1 Ranking Process ...... 74 5.2 Characteristics Common to Each Rank ...... 74

5.2.1 Low Heaving Bedrock Potential ...... 77 v ER-4645

5.2.2 Moderate Heaving Bedrock Potential ...... 79 5.2.3 High Heaving Bedrock Potential ...... 83

6. CONCLUSIONS...... 87

7. AREAS FOR ADDITIONAL STUDY...... 89

8. REFERENCES ...... 91

APPENDIX A - DESCRIPTION OF LABORATORY TESTS...... 107

APPENDIX B - FIELD DATA...... 112

APPENDIX C - DATA FROM GEOTECHNICAL REPORTS...... 122

APPENDIX D - LABORATORY TEST RESULTS...... 133

vi ER-4645

LIST OF FIGURES

Figure 1. Location of study area in Douglas County, Colorado ...... 4 Figure 2. Block diagram showing steeply dipping bedding and surficial heave features...... 6

Figure 3. Block diagram showing movement along fractures, faults, and bedding planes ...... 6

Figure 4. Block diagram showing a general model for swelling soils ...... 7

Figure 5. Percent of homes damaged on steeply dipping clay stone compared to flat lying claystone ...... 8

Figure 6. Damage versus depth to bedrock ...... 10

Figure 7. Schematic stratigraphic column of geologic units susceptible to heaving bedrock ...... 17

Figure 8. General size-distribution characteristics of a typical sample of Graneros Shale from north of Pueblo, Colorado ...... 21

Figure 9. Plasticity index versus liquid limit for shale units north of Pueblo, Colorado ...... 23

Figure 10. General size-distribution characteristics of typical shale samples of Lincoln Limestone and Hartland Shale members of the Greenhorn Limestone north of Pueblo, Colorado ...... 24

Figure 11. General size-distribution characteristics of typical samples of Fairport and Blue Hill Shale members of the Carlile Shale ...... 26

Figure 12. General size-distribution characteristics of typical samples of lower and middle shale units and upper chalky shale units of the Smoky Hill Shale member of the Niobrara Formation ...... 29

vii ER-4645

Figure 13. General size-distribution characteristics of typical samples of the Sharon Springs member, Rusty zone, and Tepee zone of the Pierre Shale north of Pueblo, Colorado ...... 32

Figure 14. General size-distribution characteristics of the Dawson Arkose 38

Figure 15. Plasticity index versus liquid limit for 59 samples of the Dawson Arkose ...... 39

Figure 16. Liquid limit versus ratio of percentage of material finer than 0.005mm to %passing No. 40 sieve for 49 samples of the Dawson Arkose ...... 41

Figure 17. Summary of physical tests of Dawson Arkose ...... 42 Figure 18. Void ratio plotted against load for a Dawson Arkose clay ...... 43 Figure 19. Location of damage survey in Jefferson and Douglas Counties 48 Figure 20. Photographs of road damage form zones of high swell forming “heave” ridges ...... 50

Figure 21. Photographs of parking lot damage form small-scale fractures or faults ...... 51

Figure 22. Photographs of sidewalk damage and driveway heave damage 52 Figure 23. Photographs of residential damage ...... 53 Figure 24. Summary of some criteria for identifying swell potential ...... 60 Figure 25. Relationship of swelling potential to plasticity index ...... 61 Figure 26. Classification of swelling under different pressures ...... 63 Figure 27. Schematic diagram illustrating which formations contain sections that are susceptible to heaving bedrock ...... 67 Figure 28. Example of damage survey trends ...... 71

viii ER-4645

LIST OF TABLES

Table 1. Chronological listing of geologic literature ...... 15 Table 2. Summary of characteristics used for heaving bedrock hazard ranking 65 Table 3. Summary of bedrock characteristics for each geologic zone ...... 68 Table 4. Summary of damage observed where bedrock is near the surface ...... 72 Table 5. Summary of selected engineering properties for each geologic zone ...... 73 Table 6. Summary of geologic zone characteristics and relative ranking ...... 75 Table 7. Characteristics of each heaving bedrock rank ...... 76

LIST OF PLATES

Plate 1: Map Showing Relative Potential for Heaving Bedrock Hazards, Map A: Roxborough Park Area, Douglas County, Colorado Map B: Perry Park Area, Douglas County, Colorado

ix ER-4645

ACKNOWLEDGMENTS

This research was supported in part by the Colorado Geological Survey. I would like to thank David Noe for introducing the problem of heaving bedrock to me and for his overall guidance. A very special thank you to Randy Phillips for compiling and printing the maps for this project. I am also indebted to Dr. W. Pat Rogers who provided valuable insights into the research, and Monica Pavlik who helped me acquire and prepare some of the data. I consulted Glenn Scott and Bill Cobban of the U.S. Geological Survey on the geology and biostratigraphic zones within my field area. I would like to thank both of these men for accompanying me in the field and contributing to this project. I also thank several individuals and departments at Douglas County who provided assistance in the collection of data and aided in the projects’ direction: Don Moore and Jennifer Drybread (Department of Planning and Community Development), Wayne Janish (Building Department), Grant Emery (Department of Public Works, Engineering Division), and Tom Miller (Information Systems Division). I would like to extend my thanks to my thesis committee. Dr. Jerry Higgins, my advisor, provided me with the opportunity to work on this project and guided me along the way. Dr. Karl Nelson, my committee chairperson, provided words of encouragement and challenge. Dr. Hal Olsen always showed enthusiasm and taught me to love and appreciate my work. My friends and family have all given me their complete support and encouragement along the way. I especially thank my husband Pete for his patience and belief in my abilities throughout the duration of this project.

x ER-4645 1

1. INTRODUCTION

1.1 Problem Statement

Deformation of the ground surface caused by heaving bedrock has caused extensive damage to subdivisions and infrastructure along a narrow belt of steeply dipping sedimentary units paralleling the Front Range of the Rocky Mountains west of Denver, Colorado. These units are dominated by thinly bedded claystones and shales that are highly weathered near the surface. Each member of the rock sequence displays various swell potentials due to changes in bedding composition and clay mineralogy. In addition, the bedrock dip ranges from 30 to 90 degrees, which allows several different units to be exposed in narrow outcrops along strike. As a result, differential movement occurs at the ground surface at scales as small as a foot in width. Until recently, damage from heaving bedrock has often been attributed to expansive soil. Expansive bedrock is not usually differentiated from expansive soils by engineers in the Denver area. This appears to be an adequate assumption if the bedrock is flay-lying and expansive soil designs are applicable. Heaving bedrock and expansive soils both undergo volume changes due to the influence of water, but heaving bedrock is a more complex geologic hazard. Expansive soils are usually associated with flat-lying deposits that swell uniformly in the vertical direction, whereas heaving bedrock occurs within steeply dipping units that swell differentially both perpendicular and parallel to bedding. Heaving bedrock problems are becoming more prevalent due to increased residential construction in the foothills area, where steeply dipping bedrock is often encountered near the ground surface. Existing subsurface investigation methods for expansive soils do not allow for adequate characterization of bedrock properties in areas with steeply ER-4645 2

dipping claystones and shales. This is because bedrock properties are extremely variable across a small distance (i.e., over the span of a house). Drilling perpendicular to the ground surface will not produce samples that can be used to construct a representative cross-section of the subsurface. Beds that may contain smectite or bentonite could be overlooked unless the entire range of bedding compositions across a site is sampled and evaluated. Trenching in potentially heaving bedrock areas can produce a representative cross-section of the subsurface and allows for selective sampling and testing of several different materials across a site. In some cases, beds with very high swell potential may need to be overexcavated and replaced with an engineered fill before residential structures and roads are built.

1.2 Purpose

The purpose of this study is to develop an engineering geologic map that delineates zones which may be affected by differential bedrock heave. The map is intended to identify areas where a thorough site and subsurface investigation is required that is specifically designed to evaluate potentially heaving bedrock problems rather than expansive soil problems.

1.3 Objectives

In order to develop a map to show heaving bedrock hazards, the following research objectives were completed: ER-4645 3

• Investigate geologic units that contain heaving bedrock properties, • Survey damage to roads, flatwork (driveways, sidewalks), and lightly loaded residential structures within each geologic unit, • Determine the engineering index properties of each geologic unit based on a local and regional literature review, subsurface investigations performed for subdivision filings, and collecting samples and performing laboratory tests, and • Rank the potential for differential bedrock heave occurring within each geologic unit based on the compilation of the previous objective activities.

1.4 Location

The study site for this research is in western Douglas County, Colorado. Douglas County is located approximately 15 miles south of the City and County of Denver, adjacent to Jefferson and Arapahoe Counties (Figure 1). In Douglas County, formations that contain lithologic intervals susceptible to heaving bedrock typically strike N22W to N60W and dip steeply (30 to 90 degrees) to the east. These geologic formations lay stratigraphically above the Lyons Formation up to, and including, parts of the Dawson Formation. This interval forms a thin band parallel to the Dakota hogback that extends from Chatfield Reservoir south 25 miles through Perry Park and crosses through the Littleton, Kassler, Devil’s Head, Dawson Butte, and Larkspur quadrangles (Figure 1). The width of this area ranges from 1/4 mile to 4 miles east-west, and covers approximately 28 square miles. ER-4645

Jefferson County DDBA

Golden

Colorado

[aiu

I. * Douglas County DBOD Cbatfiekl Reservoir V

Roxborough State Park

miles 0 5 10 15 20

Figure 1. Location of study area in Douglas County, Colorado. ER-4645 5

2. BACKGROUND

In order to understand the potential hazards associated with heaving bedrock, it is necessary to understand how heaving bedrock occurs and what the influencing factors are. The lack of recognition of heaving bedrock as a geologic hazard has resulted in a shortage of information available on the subject. There are few maps that distinguish areas with heaving bedrock problems or identify which bedrock units are susceptible to heaving bedrock. In this section, the geologic attributes and behavior of heaving bedrock will be discussed. Then, each geologic unit displaying these properties will be reviewed.

2.1 Heaving Bedrock

Heaving bedrock refers to steeply dipping bedrock that contains expansive clay minerals and undergoes near surface, differential movement along discontinuities. Differential movement can occur between different beds and along bedding planes, fractures, or faults (Figures 2 and 3). Heaving bedrock is generally associated with steeply dipping bedrock (inclined between 30 and 90 degrees from horizontal), but, in the case of movement along faults or fractures, bedrock could dip less than 30 degrees. The bedrock contains a heterogeneous composition of interbedded materials within each geologic formation. Movement results in highly localized, linear to curvilinear deformations at the ground surface that develop shortly after construction. Heaving bedrock deformation is different and more complex than that of expansive soil. A general model for expansive soil (Figure 4) assumes flat-lying beds of relatively homogeneous composition. Water penetrates the soil uniformly with depth and initiates ER-4645 6

Figure 2. Block diagram showing steeply dipping bedding and surficial heave features caused by the differential expansion of high-swelling beds. The heaves form linear trends along bedding strike (Noe and Dodson, 1995).

Figure 3. Block diagram showing surficial heave features caused by movement along curvilinear fault or fracture surfaces (F), and a linear heave feature caused by movement between bedding planes (BP) (Noe and Dodson, 1995). ER-4645 7

5°2son*1 i/SOtl5 g g S ;. CUV50 -

Figure 4. Block diagram showing a general model for swelling soils. Volume changes occur within the uppermost zone where moisture changes occur (Noe and Dodson, 1995). volumetric expansion of the soil. Heaving bedrock occurs in steeply dipping beds of heterogeneous composition (Figures 2 and 3). Heaving bedrock is also initiated by water, but the water does not infiltrate uniformly into the subsurface because of the steeply dipping bedrock and the chaotic and deep fracturing of the bedrock. These bedrock features allow water to have access to greater depths and to distribute more heterogeneously than in flat-lying materials. In steeply dipping bedrock, water penetrates horizontally and vertically to bedding in varying amounts, whereas in flat-lying materials, hydration is predominantly vertical to bedding. The mechanics behind heaving bedrock are not completely understood. Heaving bedrock could result from hydration swelling of expansive clay minerals and/or rebound of overconsolidated claystone. Several factors that contribute to heaving bedrock have been identified and are currently being studied to determine exactly how they each influence heaving bedrock. Noe and Dodson (1995) has observed that areas experiencing heaving bedrock damage share the following geologic attributes: steeply dipping bedrock, expansive claystone or bentonite, shallow bedrock, fracturing and weathering, ER-4645 8

non-uniform water infiltration, and overconsolidation. In the following sections, each of these attributes will be discussed in detail.

2.1.1 Steeply Dipping Bedrock

Steeply dipping bedding allows material with different swelling characteristics to be in close proximity to each other along or near the ground surface. This results in differential movement at the ground surface. Another effect is the development of higher than normal lateral swell pressures due to overconsolidation. Thompson (1992a) compared damage to foundation slabs built on flat-lying versus steeply dipping claystone bedrock. He found that for any given value of pre-construction swell percentage, that the damage rate incurred by houses on steeply dipping claystone was 30 to 50 percent higher than for houses built on flat-lying claystone with the same percent swell (Figure 5).

too — STOTVI OtPPMQCU rSTONO ■— FLAT Lin K> CLATSTO 10

< a o<

o x IL O ou> 40 2 5 o ...... 3 20

0 0 2 4 0 a to PERCENT SWEU. Figure 5. Percent of homes damaged on steeply dipping claystone compared to flat-lying claystone (Thompson, 1992a). ER-4645 9

2.1.2 Expansive Claystone or Bentonite

Certain kinds of clay minerals shrink on drying and expand on wetting. Heaving bedrock occurs in sedimentary rocks due to hydration of clay minerals which increases the volume of space that is necessary to accommodate the same material. Because the bedrock is dipping from 30 to 90 degrees, several expansive clay zones may be exposed to the surface. The units are confined laterally, resulting in vertical expansion at the ground surface. The change of volume may cause damage, especially to light structures, such as houses, concrete floors, and pavements. The amount of volume change that occurs depends not only on the kinds and amounts of clay minerals present, but also on the amount of water adsorbed and the amount of calcium carbonate in the material (Gardner et al., 1971). There are four kinds of swelling clay minerals; smectite (montmorillonite), mixed- layer (illite-smectite), illite, and kaolinite. Of these, smectite undergoes the greatest percentage change in volume and kaolinite the least. As more than one kind of clay mineral may occur in a deposit, the relative amounts of the different kinds of clay minerals present is important. Different proportions of smectite, illite, and kaolinite within each claystone unit affects the heaving character of the material. Intermixed with the claystones are several sandstone and siltstone units with varying heave characteristics and bentonite. Bentonite is ashfall deposit material primarily composed of smectite with extremely high swell potential. Bentonite is present as discrete beds or as a dispersed component of other beds. Gill et al. (1996) performed a series of tests on bedrock samples collected from a trench in Douglas County within the steeply dipping bedrock area. Laboratory tests (moisture content, liquid limit, plasticity index, clay fraction %, swell index test, cation exchange capacity, activity index, and x-ray defraction) confirmed that differential ER-4645 10

swelling behavior is stratigraphically controlled by bentonite beds. Discrete smectite beds correlated with linear heave features mapped across the adjacent subdivision.

2.1.3 Depth to Bedrock

Heave damage is greatest where bedrock is close to the surface. Kline (1983) mapped damage and several environmental, construction, and maintenance variables in a subdivision in Jefferson county. His work involved a statistical analysis that established single factors that influence residential damage. Kline found that bedrock within five feet of the surface was an important controlling factor with regard to damage. Thompson (1992b) similarly found a strong correlation between the percentage of houses needing repair and depth to claystone below the foundation slab (Figure 6).

30

25

20

15

10

0 2 4 6 S 10 12 DEPTH TO CLAYSTONE BELOW SLAB (FEET)

Figure 6. Damage versus depth to bedrock (Thompson, 1992b). ER-4645 11

2.1.4 Fracturing. Weathering, and Water Infiltration

Weathering and fracturing of the bedrock promotes deep and irregular water penetration. This creates a highly variable “active zone” in the subsurface where it difficult to predict the depth to competent bedrock. The claystones are weakened both at the particle level and as a fractured rock mass due to water infiltration (Noe and Dodson, 1995). As a result of the water infiltration, the bedrock behaves more like a soil within the “active zone”, but it still retains its bedding structures. Subsurface moisture distribution is heterogeneous due to fractures and bedding planes in contact with the ground surface that serve as conduits for water. Also, the variety of bedrock compositions allows for varying depth of moisture penetration. Sandstone units may also serve as conduits, whereas claystone or bentonite may inhibit moisture penetration. Increased post-development water from irrigation and reduced evaporation increases the likelihood of heaving bedrock. A higher quantity of water available for adsorption can increase the amount of clay mineral expansion.

2.1.5 Overconsolidation

A bedrock unit is overconsolidated when its preconsolidation pressure is greater than the existing overburden pressure. Overconsolidation is a result of the pressure of the maximum overburden thickness or loading that has since been removed by erosion. The rocks originally adjusted to the greater load by squeezing water from pore spaces and compacting, which resulted in a decrease in porosity. Overconsolidation is an expected ER-4645 12

characteristic of the claystone, clay-shale beds, and clayey siltstone beds (Simpson and Hart, 1980). For each sedimentary bedrock unit, the weight of the overlying sediments once consisted of the entire sequence of geologically younger strata. After the strata became tilted and raised along the mountain front, erosion removed most or all of this former load. Other younger deposits subsequently accumulated on the sedimentary bedrock units, but these younger deposits are now partially eroded. Their thickness and their weight is much less than what lay on the units at an earlier time. Therefore, the degree of overconsolidation generally is less in geologically younger units, and increases with increasing geologic age. The degree of overconsolidation may be expected to be lower for younger units that are at or near the ground surface in the eastern part of the study area, and to be greater for those older units near the mountain front (Simpson and Hart, 1980). An approximation of the former loading to present loading may be significant. For geologically younger strata such as beds in the upper part of the Pierre Shale or the Laramie Formation, there is a smaller difference in the former loading to the present loading than for the older strata such as beds in the lower part of the Pierre Shale, or the Morrison Formation. Rock that has been overconsolidated tends to rebound when the load causing the overconsolidation is removed. The rebound can be sufficient to cause heaving of a building foundation. Two factors can modify the amount of rebound (Simpson and Hart, 1980). One factor is the amount of swelling clay present. Swelling clay tends to magnify rebound, but because the amount and kind of clay can differ locally, its affect on rebound can differ locally. The other factor is the angle of dip of strata near the mountain front. Rebound tends to be greatest parallel to the loading stress, but in the opposite direction. As the strata were originally flat-lying, the tendency is for rebound to be perpendicular to their contacts and bedding surfaces. Because the strata have been tilted since ER-4645 13

overconsolidation, an excavation does not fully release the rebound stresses present (Simpson and Hart, 1980). Foundation problems related to heaving soils and weathered bedrock was investigated by Nichols et al. (1991) in the Harriman Park subdivision in Jefferson County. Trench and borehole samples were analyzed to determine the possible contribution of bedrock rebound to the structural damage in the area. The results were inconclusive.

2.2 Geology and Engineering Geology

In Douglas County, the geology has been mapped at two different scales: 1:24,000 by Scott (1963b) in the Kassler Quadrangle and 1:100,000 by Trimble and Machette (1979) in the central and southern portions of the county, including the Perry Park region (shown in Figure 1). Originally, the Perry Park area was mapped by graduate students at Colorado School of Mines and the University of Colorado at Boulder: Ballew (1957) mapped the geology of the Jarre Canyon area, Malek-Aslani (1950) mapped the geology of Southern Perry Park, Robb (1949) mapped the geology of Northern Perry Park, Ellis (1958) mapped the geology and Pennsylvanian paleontology of Perry Park, and Kinnaman (1954) mapped the geology of the foothills west of Sedalia. Trimble and Machette (1979) simplified and interpreted the previous work and published another map for the Castle Rock area at a smaller scale. Geology and biostratigraphic zones have been mapped by Scott and Cobban (1965, 1975, 1985, 1986) along the entire Front Range of Colorado from Loveland to Pueblo in four different map segments, with the exception of the Perry Park area, Douglas County. These maps include detailed stratigraphy, including faunal zones and bentonite layers and ER-4645 14

illustrate continuous bedding along strike. Preliminary geology and biostratigraphy of the Perry Park area were mapped for this study. Correlative formations to those in Douglas County are found across Colorado, Wyoming, South Dakota, and New Mexico. Information from these areas has provided general descriptions of rock and soil properties that may be present in Douglas County. During the early 1970’s, engineering geology maps were published for several quadrangles along the Front Range. Gardner (1968,1969) mapped the engineering geology of the Boulder quadrangle and Eldorado Springs quadrangle. Simpson and Hart (1980) mapped the engineering geology of the Morrison quadrangle. Miller and Bryant (1976) mapped the engineering geology of the Indian Hills quadrangle. Gardner and Simpson (1971) mapped the engineering geology of the Golden quadrangle. McGregor and McDonough (1980) mapped bedrock and surficial engineering geology of the Littleton quadrangle. Scott (1969) also mapped general and engineering geology of the northern part of Pueblo, which may be analogous to the setting in Douglas County. Potential swelling soils problems have been studied and mapped by Scott (1972) in the Morrison quadrangle and Hart (1974) along the Front Range. Both of these maps relate engineering properties to geologic units. The boundaries of potentially heaving bedrock been delineated (Noe and Dodson, 1995) for Douglas County and signified as the Dipping Bedrock Overlay District (DBOD). In Jefferson County, a similar overlay area is called the Designated Dipping Bedrock Area (DDBA) (Jefferson County, 1995). The sources of general geology, stratigraphy, biostratigraphy, and engineering geology information used for this study are summarized in Table 1. Various sedimentary formations with heaving bedrock characteristics outcrop east of the mountain front in Douglas County. These sedimentary formations include the Ralston Creek Formation, Morrison Formation, Lytle and South Platte Formations, Niobrara Formation, Carlile Shale, Graneros Shale, Greenhorn Limestone, Pierre Shale, ER-4645 15

Table 1. Chronological listing of geological literature.

General Geoloav: Griffitts (1949) Zones of the Pierre Formation, Colorado. Robb (1949) Geology of North Perry Park area, Colorado (1:12,000). Malek-Aslani (1950) Geology of South Perry Park area, Colorado (1:24,000). Keller (1953) Clay minerals in the Morrison Formation, Colorado. Kinnaman (1954) Geology of the Foothills west of Sedalia, Colorado (1:20,000). Waage (1955) Dakota Group in northern Front Range foothills, Colorado. Cobban (1956) Pierre Shale and older Cretaceous rocks in southeastern Colorado. Ballew (1957) Geology of the Jarre Canyon area, Colorado (1:24,000). Van Horn (1957) Geology of the Golden quadrangle, Colorado (1:24,000). Sheridan et al. (1958) Geology of Ralston Butte quadrangle (1:24,000). Dunn (1959) Sandstones of the Pierre Formation in the Denver Basin. Keller (1959) Clay Minerals in the mudstones of the ore-bearing formations. Kinney and Hail (1959) Upper Cretaceous rocks in North Park, Colorado. Scott and Cobban (1959) The Hygiene Group of northeastern Colorado. Treckman (1960) Petrography of the Terry and Hygiene Sandstones in the Denver Basin. Barnett (1961) Spectrographic analysis for minor elements in Pierre Shale. Rader and Grimaldi (1961) Chemical analysis for minor elements in Pierre Shale. Scott (1962) Map and geologic description of Littleton quadrangle (1:24,000). Tourelot (1962) Geologic setting and chemical composition of the Pierre Shale. Scott (1963a) Map and surficial-geologic description of Kassler quadrangle (1:24,000). Scott (1963b) Map and bedrock-geologic description of Kassler quadrangle (1:24,000). Scott and Cobban (1963) Apache Creek Sandstone member of the Pierre Shale. Schultz (1964) Interpretation of the mineratogical composition of the Pierre Shale. Scott (1964) Geology of the northwest and northeast Pueblo quadrangles. LeRoy (1965) Dakota Formation south of Golden, Colorado. Gill and Cobban (1966) Red Bird section of the Pierre Shale in Wyoming. Cadigan (1967) Morrison Formation in the Colorado Plateau Region. Sheridan et al. (1967) Map and geologic description of Ralston Buttes quadrangle (1:24,000). Varnes and Scott (1967) Map and geologic description of U.S. Air Force Academy (1:12,000). Wells (1967) Map of Eldorado Springs quadrangle (1:24,000). Waage (1968) Fox Hills Formation, South Dakota. Scott (1969) Map and geologic description of Pueblo quadrangle (1:24,000). Izettet al. (1971) Pierre Shale near Kremmiing, Colorado. Gill e t al. (1972) Composition of the Sharon Springs member of the Pierre Shale, Kansas. Scott (1972a) Map of Morrison quadrangle (1:24,000). Van Horn (1972) Map of Golden quadrangle (1:24,000). Bryant et al. (1973) Map of Indian Hills quadrangle (1:24,000). Scott and Wobus (1973) Map of Colorado Springs area (1:62,500). Van Horn (1976) Bedrock-geologic description of Golden quadrangle. Lindvall (1978) Map of Fort Logan quadrangle (1:24,000). Trimble and Machette (1979) Map of Colorado Springs-Castle Rock area (1:100,000). Schultz et al. (1980) Composition and properties of the Pierre Shale and Equivalent rocks.

Stratigraphy. Biostratiaraohv: Kittleman (1953) Post-Laramie sediments of the Denver-Colorado Springs region. Craig et al. (1955) Stratigraphy of the Morrison and related formations. Dunn (1955) Stratigraphy and forminifera of the Sandstones of the Pierre Formation. Ellis (1958) Pennsylvanian Paleontology and geology of Perry Park, Colorado. Katich (1959) Late Cretaceous Faunal Zones, Western Colorado. Reeside and Cobban (1960) Stratigraphic study of Mowry Shale, Upper Great Plains. Gill and Cobban (1961) Stratigraphy of the lower and middle parts of the Pierre Shale. Waage (1961) Statigraphy and Clayrocks of the Dakota Group along the Front Range. Scott and Cobban (1964) Stratigraphy of Niobrara Formation, Pueblo. Gill and Cobban (1965) Stratigraphy of the Pierre Shale, North Dakota. Scott and Cobban (1965) Biostratigraphic map of Pierre Shale, Jarre Creek-Loveland (1:48,000). Schultz (1965) Stratigraphy of the Pierre Shale, South Dakota and Nebraska. Sohl (1967) Upper Cretaceous Gastropods in the Pierre Shale, Red Bird, Wyoming. Camacho (1969) Stratigraphy of the Pierre Shale, Fox Hills Sandstone, and Laramie Formations. Mello (1969) Stratigraphy of the Pierre Shale and Fox Hills Sandstone, South Dakota. Cobban and Scott (1972) Biostratigraphy of Graneros Shale and Greenhorn Limestone, near Pueblo. Nwangwu (1974) Stratigraphy of the Pierre, Fox Hills, Laramie, and Arapaho Formations. Scott and Cobban (1975) Biostratigraphic map of Pierre Shale, Canon City-Florence (1:48,000). Grimm and Guven (1978) Bentonites and stratigraphy. Upper Great Plains. Scott and Cobban (1985) Biostratigraphic map of Pierre Shale, Colorado Springs-Pueblo (1:100,000). Elder et al. (1994) Stratigraphy of Greenhorn Limestone, Utah, Colorado, and Kansas.

Engineering Geoloav: Gardner (1968) EG map of Boulder quadrangle (1:24,000). Gardner (1969) EG map of Eldorado Springs quadrangle (1:24,000). Gardner et ai. (1971) EG map of Golden quadrangle (1:24,000). Scott (1972b) Map of swelling clay in Morrison quadrangle (1:24,000). Hart (1974) Map of expansive soils and bedrock, Front Range (1:100,000). Miller and Bryant (1976) EG map of Indian Hills quadrangle (1:24,000). McGregor and McDonough (1980) EG map of Littleton quadrangle (1:24,000). Simpson and Hart (1980) EG map of Morrison quadrangle (1:24,000). ER-4645 16

Fox Hills Sandstone, Laramie Formation, and Dawson Arkose (Figure 7). These units were tilted and faulted by the uplift of the Rocky Mountains and dip to the northeast, away from the mountain front. Several northwest trending faults cut these sedimentary rocks. Most of the faults are believed to have formed during Precambrian time and later reactivated during the formation of the ancestral Rockies and again during the Laramide orogeny (Kirkham and Rogers, 1981). In the following sections, each member or informal unit of each formation with heaving bedrock characteristics will be described. Stratigraphy, composition, typical thickness, and unusual features (such as concretions, markings, or characteristics resulting from weathering will be discussed. Also, engineering geologic characteristics, such as potential volume change or swelling potential of clayey materials, grain-size distribution of typical samples, and Atterberg limits will be described.

2.2.1 Ralston Creek Formation

The Ralston Creek Formation contains dense ridge-forming limestone beds separated by silty calcareous shale in the upper part (approximately 27 feet thick) and thin, fine­ grained sandstones separated by silty or sandy shale in the lower part (approximately 23 feet thick). Gypsum beds crop out between Bear Creek and Deer Creek and at Perry Park. The total thickness of the formation is 50 feet and contains more persistent beds than adjacent formations. In particular, a jasper horizon serves as a surface and subsurface marker bed in Colorado, New Mexico, Utah, and Arizona (Scott, 1963). The limestone contains nodules of black and red jasper as much as 4 inches in diameter, and some beds are composed almost entirely of small pellets and streaks of jasper. ER-4645 17

Dawson

1100’

Laramie 400-600’

Fox Hills 50-120’ I

Pierre 8000’

Smoky Hill 450’

FL Hays 35.50’ Codell 0-25’ 02022353000030910102230201 Carlile 200 ’

Graneros 360’

South Platte 275’

Momson 320-380’

Ralston Creek 45’

Figure 7. Schematic stratigraphic column of bedrock units with potentially heaving bedrock (modified from Hart, 1974). ER-4645 18

2.2.2 Morrison Formation

The Morrison Formation contains layers of sandstone, clay stone, and siltstone with intermittent bentonite beds. The formation is about 380 feet thick and consists of a lower thin sandstone unit and an upper thick claystone and siltstone unit. The lower 45-feet is the sandstone unit, which contains as many as four lenticular ridge-forming sandstone beds that are massive to thick bedded, crossbedded, and fine to medium grained. They are yellow-gray except for the basal, most persistent sandstone, which is gray, medium grained, calcareous, crossbedded, and locally contains grains of jasper from the underlying Ralston Creek Formation. At the base of most of the sandstone beds is a conglomerate containing clasts of limestone, shale, and jasper. The sandstone beds are separated by reddish gray, blocky calcareous siltstones. Above the lower lenticular sandstone unit is a unit of variegated siltstone and claystone with thin limestone and sandstone beds. This 45 foot thick zone is divided into three parts: a lower red and gray siltstone, a middle yellowish-gray claystone, and an upper red claystone. The middle part of the Morrison is a light- to yellow-gray siltstone and claystone about 165 feet thick that contains light-gray or gray massive hard crystalline limestone and yellowish-gray medium-grained sandstone with limy cement. The upper part of the formation is dominantly a red, variegated silty claystone, but locally contains many beds of reddish-brown or yellowish-gray fine- or medium-grained sandstone. A conglomerate bed containing quartzite and chert pebbles is often at the base of this unit. ER-4645 19

2.2.3 Lvtle and South Platte Formations

The Lytle and South Platte Formations form the Dakota Group hogback along the Front Range and contain mostly sandstones and siltstones with occasional beds of kaolinite (Waage, 1961). The Lytle Formation consists of about 40 feet of yellowish- gray conglomeratic sandstone. Locally it consists of a medium-grained sandstone with lenses of variegated claystone. The South Platte Formation is subdivided into the Plainview Sandstone (56 feet thick), an unnamed shaly unit (64 feet thick), the Kassler Sandstone (72 feet thick), the Van Bibber Shale (20 feet thick), and an unnamed sandstone unit at the top (85 feet thick). The Plainview Sandstone member contains thick beds of light gray, fine-grained, crossbedded sandstone with gray clayey siltstone beds. The unnamed middle shaly member is primarily gray and brown siltstone and fine-grained sandstone. Near the top it contains dark gray silty shale. The Kassler Sandstone member consists of thick beds of yellowish-gray, fine- to coarse-grained, cross-laminated, friable sandstone. The sandstone contains clay pellets and has a chert and quartzite pebble conglomerate at the base. The Van Bibber Shale member contains finely laminated clay beds interspersed with thin yellowish-gray sandstone beds. The unnamed sandstone unit at the top of the South Platte Formation contains at its base a 45 foot thick light-gray, tabular to massive, fine- to medium- grained, crossbedded sandstone that contains scattered clay pellets. Above this unit are thin, gray, fine-grained sandstone beds interlayered with thin beds of clayey siltstone and porcellanite. ER-4645 20

2.2.4 Graneros Shale. Greenhorn Limestone, and Carlile Shale

The Graneros Shale, Greenhorn Limestone, and the Carlile Shale (collectively known as the Benton Formation) contain similar rock types and cannot be distinguished within the study area. These formations consist of several dark gray, thinly bedded shale units that are separated by numerous thin beds of non-swelling limestone. They may also contain intervals of low-swell, chalky claystones. Bentonite beds (up to six inches thick) are present throughout (Hart, 1974). The following sections contain descriptions of these units.

2.2.4.1 Graneros Shale

The Graneros Shale is 225 feet thick and is marked by several layers of concretions and bentonite. The lower 15 feet is dark gray silty shale that contains light yellowish- orange bentonite layers near the top. Thin nodular sandstone beds lie in the lower part and platy sandstone beds in the upper part (Scott, 1963). The upper 210 feet of the Graneros Shale is composed of dark gray clayey shale that contains several layers of black, hard siltstone. Thin beds of light-gray or yellowish-orange bentonite are abundant in the upper part. More than 20 dark yellowish-orange to light gray bentonite beds Vz to 4 inches thick were measured in Pueblo (Scott, 1969). A bed near the base in Pueblo also contains abundant selenite crystals, which commonly occur with highly expansive bentonite (Noe and Dodson, 1995). A size-distribution curve (Figure 8) of a typical sample from Pueblo shows that the typical shale contains 64 percent clay-sized particles and 36 percent silt-sized particles ER-4645 21

100

UJ

Z < X »—

UJ _j < (/>2 z UJ CJ X UJ a .

UJ

0.001 0.01 NO. 0.1 NO. 100 200 SIZE OF PARTICLES. IN MILLIMETERS AND IN U.S. STANDARD SIEVES

Figure 8. General size-distribution characteristics of a typical sample of Graneros Shale north of Pueblo, Colorado (Scott, 1969).

(Scott, 1969). An X-ray analysis shows the Graneros Shale from Pueblo is composed of 70 percent clay minerals. Of the clay minerals, mixed-layer clay is more abundant than illite, which is about equal in abundance to kaolinite. The swelling pressure of a shale sample from 10 feet above the base of the Graneros Shale is 1,000 psf (Scott, 1969). According to Lambe (1960), the sample from the Graneros Shale is noncritical. Lambe (1960) categorizes swelling pressures and determines a potential volume change (PVC) rating as follows:

PVC rating Category Swell Pressure fpsfl

<2 Noncritical <1700 2-4 Marginal 1700-3200 4-6 Critical 3200-4700 >6 Very critical >4700 ER-4645 22

A typical sample from the Graneros Shale is classified as a CL by the Unified Soil Classification System (USCS) (U.S. Army Corps of Engineers, 1960). This classification corresponds to a liquid limit of approximately 38 and a plasticity index of approximately 12.5, which are shown in Figure 9.

2.2.4.2 Greenhorn Limestone

The Greenhorn Limestone consists of interbedded light gray limestones and dark gray shales with well-developed bentonite beds at the base. The Greenhorn Limestone contains the Lincoln Limestone member, the Hartland Shale member, and the Bridge Creek Limestone member. The Lincoln member is about 125 feet thick and contains many thin layers of pale yellowish-brown and dark-gray platy calcarenite that is composed mostly of shell fragments. At the base of the formation is an extensive 1-foot- thick dark yellowish-orange bentonite that has been traced in outcrops and in the subsurface for hundreds of miles. X-ray analysis of a sample of this bentonite from Pueblo shows that the bed contains 40 percent clay and 55 percent gypsum (Scott, 1969). Of the clay minerals, mixed-layer clay (composed of illite and smectite) is more abundant than kaolinite. The bentonite has a liquid limit of 61, plastic limit of 40, plasticity index of 21, and swelling pressure as high as 8,000 psf (Scott, 1969). The main part of the Lincoln is made up of olive-gray platy calcareous shale that weathers yellowish orange, and thin beds of very light gray and yellowish-orange bentonite. A size-distribution curve (Figure 10) shows that the noncalcareous fraction of a sample of shale north of Pueblo contains about 57 percent clay, 37 percent silt, and 6 percent sand-sized particles. X-ray analysis shows that the shale contains 55 percent clay ER-4645 23

20 25 35 40 4550 55 6030 LIQUID LIMIT

Figure 9. Plasticity index versus liquid limit for shale units north of Pueblo, Colorado: ■ Tepee zone of Pierre Shale; □ Rusty zone of Pierre Shale; O Sharon Springs Member of Pierre Shale; A upper chalky shale unit of Smoky Hill member of Niobrara Formation; 0 middle shale unit of Smoky Hill member of Niobrara Formation; © lower shale unit of Smoky Hill member of Niobrara Formation; ♦ Blue Hill Shale Member of Carlile Shale; x Fairport Chalky Shale Member of Carlile Shale; ☆ Hartland Shale Member of Greenhorn Limestone; ★ Lincoln Limestone Member of Greenhorn Limestone; + Graneros Shale (modified from Scott, 1969). ER-4645 24

100

90 _ Kartland Shale, Member ^ 80 Lincoln Limestone Member 70

60

50

40

30

20

10 0 — 0.001 0.01 NO. 0.1 NO. 1.0 NO. NO. 10 100 200 40 10 4 SIZE OF PARTICLES, IN MILLIMETERS AND IN U.S. STANDARD SIEVES

Figure 10. General size-distribution characteristics of typical shale samples of Lincoln Limestone and Hartland Shale members of the Greenhorn Limestone north of Pueblo, Colorado (Scott, 1969). minerals. Of the clay, illite is equal in abundance to kaolinite, which is more abundant than mixed-layer clay. The swelling pressure of one sample from the shale is 1,600 psf (noncritical) and the soil is classified by USCS as ML. This classification corresponds to a plasticity index of approximately 7 and liquid limit of approximately 39 illustrated in Figure 9 (Scott, 1969). The Hartland Shale member of the Greenhorn Limestone is composed of about 60 feet of gray, fissile, calcareous, fossiliferous shale that contains abundant paper-thin calcarenite layers, some thin yellowish-gray limestone beds, and some thin yellowish- orange bentonite beds. Twenty-four bentonite beds (1/4-6 inches thick) were measured north of Pueblo (Scott, 1969). A size-distribution curve (Figure 10) of the noncalcareous part of a sample of shale shows that it contains 69 percent clay and 31 percent silt-sized particles, which is classified as an ML by the USCS (Scott, 1969). X-ray analysis of the shale shows that clay minerals constitute 50 percent of the total sample. Of the clay, illite ER-4645 25

is equal in abundance to kaolinite, which is more abundant than mixed-layer clay (Scott, 1969). Swelling pressure of one sample from the shale is 1,700 psf (noncritical). A typical shale sample has a plasticity index of approximately 10 and liquid limit approximately 40 (Figure 9). The Bridge Creek Limestone member of the Greenhorn Limestone is about 130 feet thick and contains 7 or 8 beds of gray massive nodular, finely crystalline limestone about 6 inches to 2 feet thick, separated by bluish-gray nodular or thin-bedded calcareous shale. Eleven bentonite beds, ranging in thickness from J4 to 7 inches, were measured north of Pueblo (Scott, 1969). Overall, the Greenhorn Limestone has a low swell potential in the limestone components, a moderate to high swell potential in the shales, and a very high swell potential in the bentonites (Hart, 1974). These relative swell potential values were based on Holtz and Gibbs (1956) method of classification and were based on the criteria below:

Colloid Content Plasticity Shrinkage % swell Swell % < 0.001mm Index (%) Limit (%) (TJSBR1 Cateeorv >28 >35 >11 >30 Very high 20-31 25-41 7-12 20-30 High 13-23 15-28 10-16 10-20 Medium <15 <18 <15 <10 Low

2.2.4.3 Carlile Shale

The Carlile Shale consists of a dark gray shale that is sometimes silty with occasional calcareous concretions and thin layers of bentonite. The Carlile Shale contains the ER-4645 26

Fairport Chalky Shale member, the Blue Hill Shale member, and the Codell Sandstone member. The Fairport Chalky Shale member contains about 45 feet of grayish-yellow, thick- bedded, nodular, chalky marl. A size-distribution curve (Figure 11) shows the noncalcareous part of a sample of shale from Pueblo contains 53 percent clay, 42 percent silt, and 5 percent sand-sized particles (Scott, 1969). X-ray analysis indicates that 50 percent of the total sample are clay minerals (Scott, 1969). Of the clay minerals, illite is more abundant than kaolinite, which is more abundant than mixed-layer clay. Twenty- one light-gray or yellowish-orange plastic bentonite beds, ranging in thickness from 11/2 to 3 inches, were observed north of Pueblo (Scott, 1969). Several are limonitic, and some contain selenite crystals. Swelling pressure of a sample from the lower part of the shale is marginal at 3,000 psf. The USCS symbol is ML, with a plasticity index of approximately 16 and liquid limit approximately 47 (Figure 9).

z 100 o* z Blue Hill Shale Ui Member<«> co z < t—z

ui -Fairport Chalky Shale Member < oo2 H- Z Ui

UI a.

0.001 0.01 NO. 0.1 NO. NO. 100 200 Vi in SIZE OF PARTICLES. IN MILLIMETERS AND IN U.S. STAN0ARD SIEVES

Figure 11. General size-distribution characteristics of typical samples of Fairport Chalky Shale and Blue Hill Shale members of Carlile Shale (Scott, 1969). ER-4645 27

The Blue Hill Shale member includes about 8 feet of dark-gray, blocky, noncalcareous, silty shale with a thin olive-gray fine-grained sandstone at the base. Two bentonite beds, each one inch thick, were observed in the lower part of the formation north of Pueblo (Scott, 1969). Septarian limestone concretions are abundant in the upper part that are commonly 20-inch diameter and up to 4 feet in diameter (Scott, 1969). A size-distribution chart (Figure 11) shows that the noncalcareous fraction of a sample of shale north of Pueblo contains 68 percent clay, 29 percent silt, and 3 percent sand-sized particles (Scott, 1969). X-ray analysis of the shale shows that it contains 65 percent clay. Of this clay, illite is equal in abundance to kaolinite, which is more abundant than mixed- layer clay (Scott, 1969). Swelling pressure of one of the samples of the clayey lower part of the shale is noncritical at 2,400 psf and the USCS symbol is CL based on a plasticity index of approximately 13 and liquid limit approximately 35 (Figure 9) (Scott, 1969). Generally, the Fairport and Blue Hill Shale members of the Carlile Shale have a moderate to very high swell potential (Hart, 1974). The Codell Sandstone member is light gray, irregularly bedded to massive, fine to medium grained sandstone that is only 2 feet thick in this area. The sandstone contains abundant small phosphate pebbles, shark teeth, fish scales, and shell fragments. Hart (1974) describes the Codell Sandstone as having a low swell potential.

2.2.5 Niobrara Formation

The Niobrara Formation consists of the relatively thin Fort Hays Limestone member and the Smoky Hill Shale member. The following sections describe the characteristics of each of these members. ER-4645 28

2.2.5.1 Fort Hays Limestone Member

The Fort Hays Limestone member averages 35 feet in thickness and contains light gray, dense, thick, massive limestone beds at the base, and softer, thin, tabular limestone beds at the top (Scott, 1963). Thin calcareous silty shale beds and bentonite beds separate the limestone layers. This member consists of about 82 percent limestone and 18 percent shale north of Pueblo (Scott, 1969). One thin bentonite bed was observed by Scott (1969) north of Pueblo. The Fort Hays unit has a low swell potential (Hart, 1974).

2.2.5.2 Smoky Hill Shale Member

The Smoky Hill Shale averages 535 feet thick in the Kassler quadrangle and consists of dark gray chalky shale with several thick beds of chalky limestone (Scott, 1963b). A yellowish-gray soft calcareous shale in the lower 22 feet contains thin beds of limestone similar to those of the Fort Hays. North of Pueblo, this unit contains gypsum-bearing beds near the base and top as well as two bentonite beds (Scott, 1969). In this lower part, thin-bedded shale (beds averaging 7 inches thick) predominates over limestone (Scott, 1969). Above the lower unit is yellowish-gray, chalky, fissile shale that contains thin bentonite beds and a yellowish-gray, chalky, platy, speckled limestone. Selenite crystals and granular gypsum form limonite-stained lenses in this part north of Pueblo (Scott, 1969). Also, two bentonite beds were observed. A size-distribution curve (Figure 12) of the noncalcareous part of a sample of lower shale shows that it contains 50 percent clay, 47 percent silt, and 3 percent sand (Scott, 1969). X-ray analysis indicates that 40 percent ER-4645 29

z 100 5 Upper chalky Xo - shale unit / H Lower shale unit

z x< h-

UJ

< 2co *— z Middle shale unit ui - / o o . H- x u UJ

0.001 0.01 NO. 0.1 NO. 1.0 NO. NO. 10 100 200 40 10 4 SIZE OF PARTICLES. IN MILLIMETERS AND IN U.S. STANDARD SIEVES

Figure 12. General size-distribution characteristics of typical samples of lower and middle shale units and upper chalky shale unit of the Smoky Hill Shale member of the Niobrara Formation north of Pueblo, Colorado (Scott, 1969). is clay minerals. Of the clay minerals, mixed layer clay is more abundant than illite, which is more abundant than kaolinite (Scott, 1969). Swelling pressure of a sample from the lower part of the shale is noncritical at only 500 psf, but the bentonite would have higher swelling pressures (Scott, 1969). The soil is classified as ML (USCS), with a plasticity index of approximately 6 and liquid limit of approximately 28 (Figure 9) (Scott, 1969). The upper half of the Smoky Hill member contains grayish-orange fissile to thick- bedded chalky shale. In Pueblo County, Scott (1969) divides this section into three units; a middle shale unit, middle chalk unit, and upper chalky shale unit. In the middle shale unit, a size-distribution curve of the noncalcareous part of a sample of shale (Figure 12) shows that it contains 36 percent clay and 64 percent silt (Scott, 1969). X-ray analysis shows that the shale contains 40 percent clay minerals. Of the clay minerals, mixed-layer ER-4645 30

clay is more abundant than illite, which is more abundant than kaolinite (Scott, 1969). Swelling pressures of a weathered and a less weathered sample of the shale gave 2,500 and 1,250 psf. These samples were bentonitic, but would not have had as high swelling pressures as some of the bentonite beds observed in this unit. The Unified Soil Classification ranges between CL and ML. Plasticity index versus liquid limit is shown in Figure 9 for the two samples. One sample had a plasticity index of approximately 6 and liquid limit of approximately 34, while the other had a plasticity index of approximately 16 and liquid limit of approximately 39. The upper chalky shale unit observed by Scott (1969) in Pueblo County has an approximated size-distribution curve (Figure 12) that shows that the noncalcareous part of a sample of shale contains 80 percent clay-sized material and about 20 percent silt. X- ray analysis shows that the shale contains 21 percent clay minerals. Mixed-layer clay is more abundant than kaolinite (Scott, 1969). Swelling pressure of a sample of shale in the lower part of the unit is noncritical at 1,050 psf (Scott, 1969). Laboratory tests on the upper chalky shale show that in the laboratory modified AASHTO (1978) compaction test the maximum density is 114.4 pcf and the optimum moisture is 14.7 percent. The AASHTO classification is A-4, and the Unified Soil Classification symbol is ML. Plasticity index versus liquid limit is shown in Figure 9. The values for three samples are: PI = 4 and LL = 29; PI = 6 and LL s 32; PI = 5 and LL = 37 (Scott, 1969). At the top of the Smoky Hill member is a yellowish-orange, thick-bedded, speckled, chalky, ridge-forming limestone that weathers to large irregular flakes and slabs and then to calcareous clay. Chalk beds in the Smoky Hill are contorted and fractured. Generally, the Smoky Hill shale has a low swell potential, but some upper shales have moderate swell potential (Hart, 1974). ER-4645 31

2.2.6 Pierre Shale

The Pierre Shale consists of about 5,200 feet of marine sediments that are predominantly olive-gray claystone, shale, siltstone and sandstone. Limestone, ironstone concretions, and fossils are abundant and characteristic of the Pierre. Generally, the Pierre Shale has moderate to very high swell potential, but sandstones and some siltstones have a low swell potential (Hart, 1974). The Pierre Shale contains some smecitic shale and numerous white or yellow “bentonite” beds ranging in thickness from lA inch to one foot thick. Swell potential may range from low to very high, but the swell potential within specific parts of the formation is generally predictable (Hart, 1974). The Pierre Shale can be divided into four units based on biostratigraphy and composition; lower shale unit, Hygiene Sandstone member, upper shale unit, and transition unit. The following sections describe the characteristics of these units.

2.2.6.1 Lower shale unit

The basal part of the Pierre Shale consists of 1,200 feet of olive-gray, clayey, fissile shale. The lower 80 feet is calcareous clayey shale with thin bentonite interbeds. From 80-500 feet above the base the shale is iron-stained, noncalcareous, and silty with bentonite beds with selenite crystals. This bentonite bearing unit is the equivalent of the Sharon Springs member (Scott and Cobban, 1965). A sample of the Sharon Springs in Pueblo County contained 63 percent clay-sized material and 37 percent silt-sized material (Figure 13) (Scott, 1969). X-ray analysis shows that 30 percent is mixed-layer clay of unknown composition. Six bentonite beds were measured (1/2 to 5 inches thick) by Scott ER-4645 32

zs 100 x 90 Sharon Springs. £ 80 Member . tn z - Rusty zone, < x (median) > i—

Tepee zone

»— z UJ acCJ a.UI

u i

0.001 0.01 NO. 0.1 NO. 1.0 NO. NO. 10 100 200 40 10 4 1 SIZE OF PARTICLES. IN MILLIMETERS AND IN U.S. STANDARD SIEVES

Figure 13. General size-distribution characteristics of typical samples of Sharon Springs member, Rusty zone, and Tepee zone of Pierre Shale north of Pueblo, Colorado (Scott, 1969).

(1969) in the Sharon Springs. A typical shale sample was classified as MH (USCS) (Scott, 1969). Swelling pressures of two samples of Sharon Springs Shale is noncritical to critical at 2,450 - 4,500 psf. The plasticity index (~9) versus liquid limit (-57) for a typical shale sample is shown in Figure 9. A horizon between 500 and 600 feet above the base is distinguished by Baculites asperiformis Meek, and is characterized lithologically by large brown septarian limestone concretions, small gray limestone concretions, and hard fissile lenticular siltstone beds separated by shale. This zone corresponds to the middle and lower part of the Rusty zone in Pueblo (Scott and Cobban, 1965). According to a size-distribution curve (Figure 13), shale in the Rusty zone contains about 52 percent clay-size, 42 percent silt-size, and 6 percent sand-size particles (Scott, 1969). The portion of the clay material in the shale was estimated from X-ray analysis of two samples, one near the base and one near the ER-4645 33

middle of the Rusty member (Scott, 1969). In the sample near the base, 67 percent consists of clay minerals. Of the clay, mixed-layer clay equals illite, which equals kaolinite in abundance. In the sample near the middle of the Rusty member, 51 percent consists of clay minerals. Of the clay, mixed-layer clay is more abundant than illite, which is equal to kaolinite. X-ray analysis of a bentonite bed from the Rusty member shows 40 percent clay (mixed-layer clay of unknown composition is more abundant than kaolinite) (Scott, 1969). Swelling pressures for two samples of shale are marginal to very critical at 3,500 and 6,100 psf. A gypsum-bearing bentonite bed has a swelling pressure of 2,600 psf. The Unified Soil Classification from CL to CH. Plasticity index versus liquid limit is shown in Figure 9. The plasticity index for one sample is approximately 16, with a corresponding liquid limit of approximately 16. Another sample has a plasticity index of approximately 26 and liquid limit of approximately 52. At 600 feet above the base of the lower shale unit are large, rough, hard, gray, crystalline masses of limestone which are referred to as “tepee butte limestone”. Between 600 and 1200 feet above the base is a slightly calcareous, blocky shale that contains abundant clayey ironstone concretions. This part is equivalent to about the lower 190 feet of the Rusty zone at Pueblo (Scott and Cobban, 1965). Overall, the lower shale unit of the Pierre shale has a moderate high swell potential and contains interbedded bentonite units (Hart, 1974).

2.2.6.2 Hygiene Sandstone Member

Overlaying the lower shale unit is the Hygiene Sandstone which consists of a sandy siltstone and no bentonite beds. The medium-grained olive-brown Hygiene Sandstone member of the Pierre Shale is about 575 feet thick. It consists of thin bedded, friable, ER-4645 34

shaly sandstone or sandy siltstone with a few thick-bedded, hard, sandstone beds. Weathered concretions are light greenish gray and have fossils as centers. Baculites gregoryensis defines the lower boundary of the Hygiene Sandstone, while Baculites scotti defines the upper boundary. The Baculites scotti zone is characterized by hard, thin, sandy ironstone beds and ironstone concretions. The Hygiene Sandstone unit has a low swell potential (Hart, 1974).

2.2.6.3 Upper Shale Unit

The upper shale unit consists of about 700 feet of olive-gray clayey shale with several interbedded bentonites. In the lower part of this unit, the shale contains tepee butte limestone masses more than 15 feet in diameter, and small oval gray dense limestone concretions. In the middle of this shale zone, there is a thin belt of sandy shale. Moderate yellowish-brown clayey ironstone nodules and thin layers of brown fibrous aragonite and cone-in-cone are scattered on the slopes overlying this part of the section. This zone correlates with a bentonitic shale zone in the Tepee zone in Pueblo (Scott and Cobban, 1965). A size-distribution curve (Figure 13) shows that the shale in the Tepee zone in Pueblo contains 33 percent clay, 43 percent silt, and 24 percent sand-sized particles (Scott, 1969). Mineralogy determined by X-ray diffraction indicates that a sample from the bentonitic shale contains 55 percent clay minerals. Of the clay, mixed- layer clay is more abundant than kaolinite, which equals illite in abundance. Swelling pressure of the bentonitic shale is noncritical at 1,650 psf. Some beds of the Tepee will give much higher swelling pressures than those tested (Scott, 1969). A typical shale ER-4645 35

sample from this upper shale unit is classified ML (USCS). The plasticity index (~1) versus liquid limit (~32) is shown in Figure 9. A clayey shale constitutes the upper 415 feet of strata in the upper shale unit. The shale is olive gray and clayey, and contains cone-in-cone layers, aragonite layers, and reddish-brown and black ironstone concretions. Gray limestone concretions occur in three or four layers about in the middle of this shale unit. Overall, the upper shale unit of the Pierre Shale has a moderately high swell potential (Hart, 1974).

2.2.6.4 Transition Unit

The transition zone of the Pierre Shale is about 1200 feet thick with a lower segment that is an olive-brown shaly sandstone (700 feet thick) and an upper segment of olive- gray clayey or silty shale (500 feet thick) (Scott, 1963b). The lower boundary of the transition unit is marked by Baculites clinolobatus. Above the sandy beds, about 500 feet of blocky light olive-gray clayey shale contains ironstone nodules and layers. One of these layers is 27 feet thick and is composed of many yellowish-brown pea-sized limonite nodules and phosphatic pebbles. This layer lies about 290 feet below the top of the Pierre Shale and is an excellent marker bed. Above the limonite layer is light olive-gray silty shale and thin limestone interbeds. Phosphatic nodules are particularly abundant in the upper part of the Pierre. Hart (1974) made contrasting observations of the transition unit from his research across the Front Range. Hart (1974) notes that the upper transition unit grades into the Fox Hills Sandstone in a coarsening upward sequence, which leaves it with a moderate swell potential that is mainly concentrated in the lower portion. ER-4645 36

2.2.7 Fox Hills Sandstone

The Fox Hills Sandstone is a light tan, very fine-grained, arkosic, friable sandstone that is about 185 feet thick. The formation is divided into a lower sandy shale, a middle ridge-forming sandstone, and an upper soft sandstone (Scott, 1963b). The lower part is mostly soft, olive-brown sandy shale that contains thin limy sandstone layers. The middle part is 29 feet of olive-gray to yellow-gray, fine-grained massive to slabby sandstone. It is friable to hard and thin bedded with crossbedded thin laminae in some places. Cone-in-cone layers lie between some of the sandstone layers. The middle part also contains dark-brown hard calcareous sandstone concretions as large as 4 feet in diameter. The upper part is olive-brown or olive-gray soft sandstone. The Fox Hills Sandstone is a transitional deposit between the marine Pierre Shale and the continental Laramie Formation. The upper part grades laterally (east and west) into silty shales with boundaries that are gradational and interfingering. The sandstone has a low swell potential, but the silty shales have a moderate to high swell potential (Hart, 1974).

2.2.8 Laramie Formation

The Laramie Formation is about 660 feet thick and composed of thick, white to yellowish-gray sandstone beds alternating with greenish-gray claystone beds (Scott, 1963b). The sandstones are fine-grained, well-graded, white to tan, and compact. The claystones are dark gray and carbonaceous. There are black lignitic coal beds ranging in thickness up to six feet thick. The formation can be divided into two zones; a lower zone with low swelling silty claystone (approximately 1/3 of the thickness) and an upper zone ER-4645 37

with moderate to very high swelling claystones. There are many concretions and concretionary layers concentrically banded that range from V a inch to 4 feet across. The thin sandstone and conglomerate beds are lenticular, and the thick shale beds are persistent and regular in thickness. There is a low swell potential in the sandstones and a moderate to very high swell potential in the claystones (Hart, 1974). Some of these claystone beds are smectitic, particularly in the middle 1/3 of the unit. Other claystones in the Laramie, however, contain a high percentage of kaolinite.

2.2.9 Dawson Arkose

The Dawson Arkose is mainly crossbedded sandstones that occasionally contain lenses of moderate to high swelling clays. The clayey shale contains some lenses of brownish-black lignitic coal. The lower part of the Dawson is characterized by conglomerate, the upper part by shale. Bedding is irregular with most beds being curved and lenticular. Individual beds range in thickness from 0-200 feet with the conglomerate beds being the thickest (Scott, 1963b). Shale beds have been thinned and highly contorted by compression during lithification. The greater part of the material consists of pebbles V a to 1 inch in diameter. Lesser amounts of sand and cobbles, as much as 6 inches in maximum dimension are present. Because of the fluvial origin of the formation, vertical and lateral variations in grain size are extreme. Most of the grains are subrounded, unpolished, and are loosely compacted with much pore space. Some of the claystone lenses in the Dawson Arkose swell upon exposure and produce a loose-textured crust as much as 3 inches thick (Vames and Scott, 1967). There is a low ER-4645 38

to moderate swell potential in the sandstone and a moderate to very high swell potential in the siltstones and claystones (Hart, 1974). Two samples of fine-grained material washed from the samples of arkose was analyzed in an X-ray diffractometer and the mineral content showed abundant kaolinite and minor amounts of illite in one sample (Scott, 1969). Smectite was not detected. Two samples of fine-grained matrix of the greenish friable clayey sandstone (dominant material in the andesitic lens of the Dawson, notably different mineralogically from the normal white Dawson Arkose) were analyzed, and were found to both contain major amounts of smectite and a trace of illite (Vames and Scott, 1967). One sample contained major kaolinite and the other a trace. The general size-distribution characteristics of the Dawson Arkose at the United States Air Force Academy north of Colorado Springs are shown in Figure 14 (Vames and Scott, 1967). The suite includes 52 samples for which the percent smaller than the No. 4,10,

z o5 zOT Ui z

Ui <2 (A EXPLANATION H- z ui u K Ui OL

0.001 0.01 No. 0.1 No. 1.0 No. 100 200 4 0 10 SIZE OF PARTICLES. IN MILLIMETERS AND U.S. STANDARO SIEVES

Figure 14. General size-distribution characteristics of Dawson Arkose from the United States Air Force Academy (Vames and Scott, 1967). ER-4645 39

40, and 200 U.S. Standard sieves and 0.02 and 0.0005 mm were recorded. A median line is drawn through points at which 26 of the samples exceeded that percent passing at a particular size. Because most of the complete size analyses were made on materials of special interest in construction, the more troublesome siltstone and claystone are probably represented more frequently among these tests than the equally common sandstone. The extremes of a few partial analyses of coarser material are shown by crosses. The plasticity index versus the liquid limit for samples of Dawson Arkose at the Air Force Academy is plotted in Figure 15 (Vames and Scott, 1967). The liquid limit

30

25

20 x Ui za

o£ 15 VI Normal Dawson Arkoso < a. 10

5

0, 30 35 40 60 70 LIQUIO LIMIT

Figure 15. Plasticity index versus liquid limit for 59 samples of Dawson Arkose from the United States Air Force Academy (Vames and Scott, 1967). ER-4645 40

increases rather uniformly (as shown in Figure 16) as the ratio of percentage of material finer than 0.005 mm to percentage passing the No.40 sieve increases (Vames and Scott, 1967). This ratio is in effect the proportion of clay in the material upon which the liquid limit test is made. Other physical tests of the Dawson Arkose performed on samples from the Air Force Academy is given in Figure 17. Laboratory swell tests of a silty clay with some lenses of sandy clay or sand indicate that it is not a highly expansive material, but that it swelled a moderate amount upon saturation under reduced loads (Vames and Scott, 1967). The average in-place density was 119.4 pcf, or 95 percent of Modified AASHTO maximum at the airfield location. One sample of clay stone from the Dawson Arkose was subject to a consolidation test and the plot of void ratio against the load (Figure 18) shows that the clay stone is heavily preconsolidated (Vames and Scott, 1967). Even under a load of about 30 tons per square foot, consolidation is slight. Swelling pressures reached about 4 tons per square foot before consolidation began at greater loads. The sample swelled measurably beyond its original size upon release of load, as shown by the rebound curve. X-ray diffraction showed that kaolinite is abundant and illite is a minor constituent. Both smectite and smectite-illite mixed-layer clay were found in the clay-size fraction (Vames and Scott, 1967). ER-4645 41

0.60

0.50

0.40

c« 0.30

0.20

0.10

0 15 20 25 30 35 40 45 LIQUID LIMIT

Figure 16. Liquid limit versus ratio of percentage of material finer than 0.005 mm to percentage passing No. 40 sieve for 49 Dawson Arkose samples from the United States Air Force Academy (Vames and Scott, 1967). ER-4645

Tests Average Range

Specific gravity...... g per cc— 15 2.64 2.59-2.70 Dry field density...... lb per cu ft— 19 116.3 104.3-124.2 Maximum density. Am. Assoc. State Highway Officials modified compaction__ lb per cu ft.. 22 126.1 113.0-134.3 Optimum moisture...... percent.. 22 8.9 5.6-15.4 Laboratory California Bearing Ratio at— 90 percent of maximum density...... 5 19.4 8-29 95 percent of maximum density...... 10 32.2 5-60 100 percent of maximum density...... 10 71.3 20-135 Field California Bearing Ratio______3 18 7-27.5 Modulus of subgrade reaction...... lb per cu in .. 3 216 200-225

Figure 17. Summary of physical tests of Dawson Arkose from the United States Air Force Academy (Vames and Scott, 1967). iue1. Void ratio18.Figure plotted against load for a Dawson claystonesample at the United States Air Force Academy (Vames and Scott,1967). ER-4645

VOID RATIO 29 .2 0 0 .3 0 0.26 8 .2 0 27 .2 0 Jl O 0 3 100 OD I P NS E SUR FOOT SQUARE PER UNDS PO IN LOAD. 1000 umed iiil l ai us for d se u ratio eld v initial d e m su s A o i rce age o oi ation solid con e g ta en c er p g tin u p com de s equent odi g in load t n e u q se b su er nd u 10.000

100.000 43 ER-4645 44

3. METHODOLOGY

3.1 Criteria for Delineating Areas of Potentially Heaving Bedrock

The goal of this study is to delineate areas that are susceptible to the geologic hazard of heaving bedrock and rank relative potentials for heaving damage with respect to certain geologic units. The criteria used to establish ranks includes bedrock dip and composition, residential damage in potentially heaving bedrock areas, and engineering index properties of the bedrock. First, areas where heaving bedrock could occur within the study area were determined. Steeply dipping bedrock (inclined between 30 and 90 degrees from horizontal) was identified using geologic maps and field reconnaissance. The composition of the bedrock was evaluated from local and regional geologic publications. Heaving bedrock is known to occur in bedrock that has interbedded materials with different swell potentials or bedrock that has high swell potential. The presence of bentonite as well as the continuity of the bedding was also evaluated. A survey was conducted to inventory the type and amount of damage to roads, flatwork, and residential structures that were built directly on steeply dipping bedrock in certain areas of Douglas and Jefferson Counties. General relationships between bedrock composition and performance of residential structures were established from the information collected for the survey. Engineering properties were then determined for each geologic unit with the potential for heaving bedrock. Information was taken from a series of geotechnical reports for subdivisions in the Roxborough Park area in northern Douglas County. Where this ER-4645 45

information was not complete, sampling and testing was conducted as part of this investigation. All of this information was used to rank the potential for heaving bedrock across steeply dipping bedrock areas.

3.2 Bedrock Characteristics of Potentially Heaving Bedrock

An extensive review of the literature was conducted in order to determine several characteristics about each geologic unit of interest. Information used in this research was obtained from several sources, including USGS and Colorado Geological Survey bulletins, special publications, maps, and open file reports. Information also came from thesis work from Colorado School of Mines and the University of Colorado, Boulder. A field reconnaissance was conducted to check geologic boundaries and information provided. First, areas with steeply dipping bedrock (inclined 30 to 90 degrees from horizontal) were identified using geologic maps and field reconnaissance. Each member or informal unit of each geologic formation was identified within this area as a potentially heaving bedrock unit. The lateral extent of bedding was recorded so the accuracy of extrapolating information along bedding strike within a particular geologic unit would be known. Beds generally pinch out both along their strike and down their dip. Beds were classified as continuous if they extend for more than 2000 feet along strike or discontinuous if they extend for less than 2000 feet along strike. Transitional means that the unit contains some beds that are continuous and some that are discontinuous. The composition of each steeply dipping geologic unit was then evaluated. The variety of compositions within each geologic unit was determined as well as the dominant ER-4645 46

composition. These were categorized as bedrock with non- or low-swell potential (sandstone, siltstone, limestone) or bedrock with moderate- to very high- swell potential (claystone). The occurrences of these compositions were described as Major, Common, minor, ? (possible), or - (absent). A Major occurrence corresponds to references citing this material as the most abundant constituent of that geologic zone. A Common occurrence corresponds to the references citing this material as a component of that geologic unit, but not a major one. A minor occurrence corresponds to the references citing this material as occasionally occurring within this geologic unit. A ? (possible) occurrence corresponds to the references citing this material as a possible constituent of this geologic unit. An - (absent) occurrence corresponds to the references citing this material as not existing in this geologic unit. The presence and amount of specific types of clays were recorded where information was available to determine the potential for swelling within each geologic zone. Clay types include smectite, illite, mixed-layer and kaolinite. In addition, the presence of bentonites, either as intermittent stringers or as distinct marker beds was recorded.

3.3 Survey of Damage Occurrence

Once the geologic units with the potential for heaving bedrock were identified, correlations between these subsurface units and damage occurring at the surface from heaving bedrock were established. A survey of damage was conducted in specific areas of northwestern Douglas and southwestern Jefferson Counties where most of the houses were built directly on bedrock surfaces, and there is a history of heaving bedrock damage. Damage was recorded in the three broad categories of roads, flatwork (driveways and sidewalks), and residential structures. ER-4645 47

Not all of the geologic zones of interest have been developed. No damage information was collected from the following geologic units: Ralston Creek Formation, Morrison Formation, Lytle and South Platte Formations, Graneros Shale, Greenhorn Limestone, Carlile Shale, Fort Hays Limestone, and Smoky Hill Shale. Some construction sites in Jefferson County occur in the Denver and Arapahoe Formations, which correlate to the Dawson Formation to the south. Therefore, these values were assumed to represent the behavior of the Dawson Formation.

3.2.1 Selection of Survey Location

The survey was conducted in areas where bedrock is known to be at or near the ground surface and lightly loaded structures have been subjected to differential movement as a result of heaving bedrock. Because there is very little development on these geologic units in Douglas County, several locations in the adjacent Jefferson County were selected (Figure 19). Approximately 2000 houses were surveyed across the geologic zones of interest, which covered an area of approximately 5 square miles. This survey location is biased based on experience with residential problems associated with heaving bedrock recorded at the Colorado Geological Survey. ER-4645 48

Potentially Heaving Bedrock [ h D enver

Colorado

Scale

0 miles 4.5

285J ^ Damage Survey

Jefferson Castle Rock County

Douglas County

Figure 19. Location of damage survey in Jefferson and Douglas Counties. ER-4645 49

3.2.2 Field Procedures

Information was gathered by driving through the neighborhoods at low speeds observing obvious damage to structures, roads, and flatwork and recording the data on aerial photographs. Measurements were not made directly, but estimated from a distance of up to approximately 200 feet.

3.2.3 Damage Descriptions

Three categories of damage were recorded in the field: roads, flatwork, and residential structures. Road damage from zones of expansive bedrock or small-scale faulting results in continuous and discontinuous heave features, in the form of bumps or indentations on the subgrade (Figures 20 and 21). Heave features larger than approximately six inches are considered large. Asphalt patches or newly paved segments may indicate that past heave has caused road damage or damage to water lines or utility lines. Flatwork damage involves any of the following: newly replaced concrete driveways or sidewalks, heaved or cracked driveway slabs, open space along the bottoms of garage doors, deformed or broken garage doors and windows, or porches that are bowed, uplifted, or detached from stairways (Figure 22). Moderate to high damage is classified as anything with greater than approximately one inch of offset. Low to moderate damage is less than an inch of offset. Structural damage can be observed by crumbling, leaning, detached, or collapsed chimneys, leaning outside walls, crooked or jammed windows, diagonally cracked brick facings, or cracks in foundation concrete walls (Figure 23). If any of these are observed, then it is recorded as possible structural damage. ER-4645 50

Figure 20. Photographs of road damage from zones of high swell, forming linear heave features (arrows). ER-4645

Figure 21. Photograph of damage to a parking lot possibly from a small-scale fault (arrows). Aspalt patches indicate utility or water line damage, shown by arrows. ER-4645

i

&2j£fc‘ '

Figure 22b Figure 22. Photographs of sidewalk damage (Figure 22a) and driveway heave damage (Figure 22b), shown by arrows. ER-4645 53

Figure 23a

Figure 23 b Figure 23. Photographs of structural damage (Figure 23a) and a detached chimney (Figure 23b), shown by arrows. ER-4645 54

3.2.4 Damage Analysis

Damage observations may be symptoms of heaving bedrock, but some of the damage may be the result of something other than heaving bedrock. Because this information is not directly measured, there may be a significant amount of error in data collected at each specific residence. To keep this information in context, it has been categorized into zones that have the same general type and amount of damage. Where one damage observation may not prove that there is a heaving bedrock problem, collectively, there may be a more prominent link to a general trend in the subsurface. The results of the damage survey were categorized into clusters of damage according to the three categories of roads, flatwork, and residential structures. Then, these trends were examined across each geologic unit and categorized into frequency of occurrence. Infrequent designations indicate that very little or no damage was recorded in these areas that contained bedrock near the ground surface. Moderate indicates that there was some damage occurring, but not at all locations that were evaluated. Frequent means that a majority of the area that was surveyed displayed some kind of damage. These designations do not indicate the severity of damage. For example, a designation of Infrequent damage occurrence would mean that very few cases of any damage were observed, not that there was a low level of damage observed. ER-4645 55

3.4 Determining Engineering Properties of Geologic Units

Engineering properties were collected for each geologic unit capable of heaving bedrock from twenty-one different geotechnical reports submitted for subdivisions in the Roxborough Park area in northern Douglas County. Information taken from these reports include natural water content, natural dry density, USCS or AASHTO classification, material descriptions, grain-size distribution, Atterberg limits, percent swell (and test surcharge), swell pressure, resistance to penetration, and unconfined compressive strength. This information is summarized in Appendix C. The geotechnical reports do not include information on all of the geologic units capable of heaving bedrock. Where the reports were incomplete, sampling and testing was conducted to provide data from all of the units of interest.

3.3.1 Selection of Sample Locations

Sample locations were designed to sample each geologic zone at least three times and produce two cross-sections of the field area to assess whether engineering properties can be consistently extrapolated along strike. From the surficial geology map (Scott, 1963a), bedrock outcrop areas were determined for the Kassler quadrangle. Two transects were developed in easily accessible areas where permission could be obtained from land owners. The location of these test holes are shown on Plate 1. Other samples were collected from the southern extent of the field area (Perry Park area) because these lower geologic zones were not well exposed in the Kassler quadrangle. ER-4645 56

3.3.2 Sample Collection Procedures

Sample collection was conducted during August and September, 1995, during the driest part of the summer. This complicated collection procedures because the ground surface was unusually dry and hard. With the use of a shovel and sometimes a crow bar, the surface material was removed before sampling. Three types of samples were collected from the field. The first sample was for moisture content determination, which was collected in a small moisture container and the lid placed on securely. The container was wrapped with electrical tape and then placed inside a plastic bag that was secured air-tight. The sample was immediately taken to the lab at the end of the day and either stored 24 hours or tested immediately for moisture content. The second type of sample collected was for natural dry density determination. A clean surface was first cleared, typically 1 foot from the ground surface. A hammer and driver were used to push a 4-inch long brass sampler tube (with a diameter of 2 inches) into the soil. Plastic lids were placed on each end of the tube, which were wrapped with electrical tape and then placed in a plastic bag and secured air-tight. These samples were also taken immediately back to the laboratory and placed in a humidity room until testing took place (approximately 1-2 weeks). The third type of sample that was collected was for Atterberg limit testing or particle- size determination. These were disturbed samples, collected by digging material with a rock hammer or trowel. The sample material was placed in two zip-lock plastic bags and bound air-tight. These samples were immediately taken back to the laboratory and placed in a humidity room until testing took place (approximately 1-2 weeks). ER-4645 57

3.3.3 Field Descriptions

Samples were described in the field as they were collected and their locations were closely marked on a topographic map. Sample type (disturbed/ undisturbed), sample depth, material type, color, plasticity, grain-size, and general unit descriptions were recorded. This information is summarized in a series of tables in Appendix B.

3.3.4 Laboratory Testing Program

The objective of the laboratory testing program was to confirm and/or determine the engineering index properties of the materials within each geologic zone.

3.3.4.1 Selection of Laboratory Tests

Tests selected to be performed were based on standard geotechnical testing procedures for the Denver area. These tests were used to provide consistent results with local industry standards and to illustrate how these test results can indicate potentially heaving bedrock material. Standard tests that are normally conducted include: • natural water content (ASTM D 2216-92) • natural dry density (ASTM D 2937-94) • Atterberg limits (liquid limit, plastic limit, plasticity index) (ASTM D 4318-93) ER-4645 58

• particle-size analysis (ASTM D 422-63) • USCS classification (ASTM D 2487-93)

The procedures for conducting these tests are generally in accordance with ASTM standards and are outlined in Appendix A. Water content is one of the most significant index properties used in establishing a correlation between soil behavior and its properties. The natural water content of a soil reflects primarily recent storm events in this region. However, the natural water content controls the amount of swelling a soil may experience (Chen, 1975). Very dry clays with natural moisture content below 15 percent usually indicate danger. Clays with moisture content below 30 percent indicate that most of the expansion has already taken place and further expansion will be small. The natural dry density is directly related to natural moisture content and is another index of expansion. Soils with dry densities in excess of 110 pcf generally exhibit high swelling potential (Chen, 1975). In conjunction with other engineering properties, dry density can be used to estimate swell potential. Atterberg limits are important empirical limits that may be indicative of swelling behavior. They correlate with engineering properties and swelling behavior because both the Atterberg limits and the engineering properties are affected by the same things (clay minerals, ions in the pore water, the stress history of the soil deposit). Casagrande’s plasticity chart (liquid limit versus plasticity index) can be used to classify fine-grained material as well as qualitatively determining clay minerals (Holtz and Kovacs, 1981). Among clay-rich soils, liquid and plastic limits are generally higher for smectite clays than for kaolinites or illites (Mitchell, 1993). This is because smectites are able to disperse into very fine particles with large water-absorbing volume (Rahn, 1986). ER-4645 59

The plasticity index (PI) is useful in engineering classification of fine-grained soils, and many engineering properties have been found to empirically correlate with the plasticity index. A small plasticity index (5 percent) shows that small changes in moisture content will change the soil from a semisolid to a liquid condition. A large plasticity index (20 percent) shows that considerable water can be added before the soil becomes liquid. This would normally indicate that the material is a good foundation material. However, soils with very high plasticity indexes (>35 percent) may have a high swell capacity. The greater the plasticity index, the greater the swelling potential (Mitchell, 1993). Several different methods of determining swell potential have been proposed. Abduljauwad and Al-Sulaimani (1993) have summarized these methods (Figure 24). The method used by Chen (1975) was used for this study because it corresponds with the type of data available from geotechnical reports (Atterberg limit tests) and because Chen’s method is based on materials from the Denver metropolitan area. Chen (1975) compares his method of predicting swelling potential from plasticity index to other methods (Figure 25). All tests refer to a surcharge pressure of 1 ksi with moisture content between 15 and 20 percent and dry density between 100 and 110 pcf. Chen’s (1975) relationship between swell potential and plasticity index can be expressed as follows:

S = B eA(PI) in which A = 0.0838, and B = 0.2558

Chen (1975) has established the following relation between swelling potential of clays and plasticity index: ER-4645 60

Reference Criteria Remarks

Holtz ( 195V) CC > 28. PI > 35 and SL < 11 (verv hieh) Based on CC. PI. Jk SL 20 3 CC s 31. 25 s PI 3 41 and 7 3 sL £ 12 (hieh) 13 s CC s 23. 15 s PI s 28 and U) s SL £ 16 (medium) CC 3 15. PI s IX and SL a 15 (low) Seed et al. ( 1962) See Fig. 1 u Based on oedometer test using compacted specimen, percentage of clay < 2 pm and activity Altmeyer (1955) LS < 5. SL > 12. and PS < 0.5 (noncritical) Based on LS. SL. and PS 5 3 LS 3 8. 10 3 SL 3 12 and 0.5 3 PS 3 1.5 (marginal) Remolded sample (o—,-, and u*,^) LS > X. SL < 10 and PS > 1.5 (critical) Soaked under 6.9 kPa surcharge Dakshanamanthv and See Fig. lb Based on plasticity chart Raman (1973) Raman (1967) PI > 32 and SI > 40 (verv high) Based on PI and SI 23 3 PI 3 32 and 30 3 SI 3 40 (high) 12 3 PI 3 23 and 15 3 SI 3 30 (medium) PI < 12 and SI < 15 (low) Sowers (1970) SL < 10 and PI > 30 (high) Little swell will occur when »v„ results in 10 3 SL 3 12 and 15 s PI 3 30 (moderate) LI of 0.25 SL > 12 and PI < 15 (low) Van Der Merwe (1964) See Fig. Ic Based on PI. percentage of day < 2 pan. and activity Uniform Building El > 130 (very high): 91 3 El 3 130 (high) Based on oedometer test on compacted Code. 1968 51 3 El 3 90 (medium): 21 3 El 3 50 (low) specimen with degree of saturation 0 3 E l 3 20 (very low) dose to 505% and a surcharge of 6.9 kPa Snethen (1984) LL > 60. PI > 35. ? « > 4 and SP > 1.5 (hieh) PS is representative for field condition, 30 s LL s 60. 25 3 PI 3 35. 1.5 s 3 a'and 0.5 3 can be used without rw . but accuracy SP 3 1.5 (medium) will be reduced LL < 30. PI < 25. < 1 J and SP < 0.5 (low) Chen (1988) PI 2 35 (very high): 20 3 PI 3 55 (high) Based on PI • 10 3 PI 3 35 (medium): PI 3 15 (low) McKeen (1992) Fig. Id Based on measurements of soil water content, sucdon, and volume change on drying

Vijawergiva et al. Log SP - 1 /1 2 (0.44 LL - wo + 5.5) Empirical equations (1973) ’ Navak et al. (1974) SP - (0.002 29 PI) (1.45 c)/w„ + 6.38 Empirical equations Weston (1980) SP - 0.004 II (LLJ417 q 'iM wn~-u Empirical equations

N o t e : C - clay. q a surcharge CC a colloidal content. % SI a shrinkage index ■ LL - SL. El » Expansion index - 100 x percent swell x fraction passing No. 4 sieve SL a shrinkage limit. % Li ■ liquidity index % SP a swell potential. % LL * liquid limit % tv0 a natural soil moisture LL, a weighted liquid limit. % >*V “ optimum moisture content* % LS a linear shrinkage % rM a natural soil suction in tsf PI a plasticity index. % a max dry density PS a probable swell. %

Figure 24. Summary of some criteria for identifying swell potential (Abduljauwad and Al-Sulaimani, 1993). andGibbs, Seed, Woodard, and Lundgren,and Chen (Chen, 1975). Relationship Figure 25. of swelling potentialto plasticityindex as predicted byHoltz ER-4645

SWELLING POTENTIAL (% ) 10 8 9 4 7 6 5 2 0 3 0 10 s 15 LSIIY NE (%) INDEXPLASTICITY 20 25 30 33 40 61 ER-4645 62

Swelling Potential Plasticity Index

Low 0-15 Medium 10-35 High 20-55 Very high 35 and above

Seed, Woodard, and Lundgren (1962) established the following simplified relationship between swell potential and plasticity index based on soils with clay contents between 8 and 65 percent: S = 60K(PI)2 44 in which S = swell potential, and K = 3.6 x 10'5 The method established to correlate plasticity index to swell potential used by Holtz and Gibbs (1956) as well as the PVC method (Lambe, 1960) of determining swell potential have been previously discussed in the background chapter. A consolidation-swell test (commonly referred to as the “Denver swell test”) is often performed along with engineering index property tests. This test corresponds to the ASTM (1995a) standard test method D 4546-90. Even though the consolidation-swell test does not directly correlate with the other methods described above, it is more commonly used to indicate the amount of swelling that a material will undergo at a site. The standard criteria for swelling is shown for different pressures in Figure 26 (Fox, 1994). Particle-size analysis was performed on samples that were too coarse-grained for the Atterberg limits tests. The size of the soil particle, especially for granular soils, has some effect on engineering behavior. The ASTM classification can be derived from the Atterberg limits and particle-size distribution. The Unified Soil Classification System (USCS) is used as the ASTM standard and provides a systematic method of categorizing soils. iue2. ClassificationFigure 26. of swelling under different pressures based on valuesfrom consolidation-swell test results(Fox, 1994). ER-4645

MEASURED SWELL UNDER 500 PSf (7.) o * 2 o a w X Cd •< o X > w X >< o o x < 10 12 14 0 4 2 6 8 LOW ESRD WL UDR 00 S (%) PSF 1000 UNDER SWELL MEASURED MODERATE HIGH EY IH CRITICAL HIGH VERY 63 ER-4645 64

3.3.4.1 Laboratory Testing Procedures

Testing procedures were carried out in accordance to ASTM standards (1995a and 1995b), with minor exceptions. Some techniques were customized for this study following methods recommended by Bowles (1992). These procedures are detailed in Appendix A.

3.5 Ranking Process

A ranking process was developed based on bedrock composition, damage occurrence, and engineering index properties. Characteristics were compiled for each geologic zone and then relatively ranked based on ranges of data. There are three categories that increase in severity with increasing numbers. The specific cause of heaving bedrock may be different for each geologic zone, but they can still be grouped together in a ranking according to the severity of heaving anticipated. The general guidelines for each rank is described in Table 2. ER-4645 Table 2. Summary of characteristics used for heaving bedrock hazard ranking. 73 ■a X o> O X O) a a a ■D ® = "o .E «x ' S n i

o ■o in in in in in in in in to in o o - « cm n n in - * n i o o '3 a a o> o> n a a> a « « r o CL

■o x L Q O O' *o S •E o • a

.2 65 ER-4645 66

4. RESULTS

4.1 Bedrock Characteristics of Potentially Heaving Bedrock

Units that were identified as containing potentially heaving bedrock include the Ralston Creek Formation, Morrison Formation, Lytle and South Platte Formations, Graneros Shale, Greenhorn Limestone, Carlile Shale, Pierre Shale, Fox Hills Sandstone, Laramie Formation, and part of the Dawson Arkose. These formations are shown on Figure 27 and define the study area delineated in Plate 1. The western boundary of the study area corresponds to the base of the Ralston Creek Formation. Where the Ralston Creek Formation is faulted out between Jarre Canyon and Perry Park, the western boundary corresponds with the mapped location of the Jarre Creek Fault. The eastern boundary corresponds to the change in bedrock dip to less than 30 degrees within part of the Dawson Arkose. The northern boundary corresponds to the Douglas County line, which intersects Jefferson County at the South Platte River. The southern boundary represents the location where bedrock materials are buried beneath at least 25 feet of alluvial material and the steeply dipping bedrock may be completely faulted out by the Rampart Range Fault, so the possibility of encountering heaving bedrock during residential excavations is unlikely. Once the formations susceptible to heaving bedrock were identified, the bedrock properties from a detailed literature review were analyzed. The results of this geology literature review are summarized in Table 3. The occurrence of three different bedrock compositions was evaluated; bentonite (high to very high swell potential), claystone (moderate to very high swell potential), and low- to non-expansive bedrock. The lateral ER-4645 H Potential Bedrock Heave Area cn m m m &■■//////,/' ,'Mv/A km 101 I •I

!l £ d u cd ti* Sr Sr ti* 5 5 - v* L- r? C/3 67 ER-4645 Table 3: Summary of bedrock characteristics for each potentially heaving bedrock unit along the Front Range, Colorado. ■a © n es es >» W> ^ > . Q . O Q. a. . a. . a a. C l , TJ U U C/3 CO

Major = a majority of references cite this material as the most prominent constituent of this geologic unit; Common = a majority of references cite this material as a component of this geologic unit; minor = a majority of references cite this material as occasionally occurring within this geologic unit; ? ? = regional literature review shows that bentonite layers could exist within these units, but they have not been observed locally; - = no bentonite layers have been observed in these units; Continuous = beds laterally extend more than 2,000 feet along strike; Discontinuous = beds laterally extend less than 2,000 feet along strike; Transitional = some beds are continuous and some beds are discontinuous. 68 ER-4645 69

continuity along strike was denoted for each geologic unit and categorized as discontinuous, continuous, and transitional.

4.2 Damage Survey Results

The results of the damage survey were categorized into clusters of damage according to the three categories of roads, flatwork, and residential structures. These trends were examined across each geologic unit and categorized into frequency of occurrence, not severity of damage. An example of the data collected for one neighborhood is illustrated in Figure 28. The geology is overlaid on the damage trends to flatwork and residential structures. The flatwork and residential damage within the Dawson Arkose and upper zone of the Laramie Formation would be described as frequent, whereas the flatwork and residential damage in the lower zone of the Laramie Formation would be described as infrequent for this area. The results of the damage survey are summarized in Table 4.

4.3 Engineering Properties

A total of 83 field samples were collected. The sample descriptions and locations are summarized in Appendix B. The results of the Atterberg limits, USCS classification, swell potential (interpreted from plasticity index), and the number of samples that these values are based on are shown in Table 5. A total of 51 Atterberg limit tests, 14 dry density tests, 76 moisture content tests, and 5 grain-size distribution tests were completed, Some values in Table 5 were taken from previous geotechnical investigations in heaving ER-4645 70

bedrock areas (summarized in Appendix C) or from other previous work and used in conjunction with the laboratory test results performed as part of this study. Laboratory results are contained in Appendix D. ER-4645 71

TKda

Klu

‘{•i'riSTL Kll

Kfh

Figure 28. An example of damage survey trends covering an area of approximately one square mile. Dotted zones represent areas with flatwork damage and hatched zones represent areas with residential structural damage. The geologic units that are overlaid include the steeply dipping portion of the Dawson Arkose (TKda), the upper zone of the Laramie Formation (Klu), the lower zone of the Laramie Formation (Kll), and the Fox Hills Sandstone (Kfh). ER-4645 Table 4: Summary of damage observed where bedrock is near the ground surface in selected neighborhoods in Douglas and Jefferson Counties, Colorado. c n cr a" 3 T cr co CT1 r c « cr o> ST ^ , 5 w cr 3 T o“ cr

Infrequent = very little or no damage was recorded; Moderate = some damage was recorded, but not in a majority of locations that were evaluated; Frequent = a majority of the area that was surveyed displayed some kind of damage; - = areas that are undeveloped or newly developed where no observations were made about damage; * = observations were made in the Denver and Arapaho Formations, which are laterally equivalent to the Dawson Arkose. 72 ER-4645 Table 5: Summary of selected engineering properties for potentially heaving bedrock units in Douglas County, Colorado.

Number Atterberg

Formation Member of Samples Limits uses Swell n

(or informal unit) Examined (%) PI (%) Classification Potential* m Dawson Arkose 30-75 12-52 SP Low | m m Laramie (upper zone) 35-85 15-70 CH, CL Moderate - V. High (lower zone) 25-45 5-30 CL, ML Low - Moderate O * * Cu i Fox Hills Sandstone i Low | (upper transition zone) 2 35-90 15-50 CH, CL Moderate - V. High Pierre Shale (upper shale) 12 34-90 12-54 CH V. High Hygiene Sandstone 5 30-42 10-25 CL, ML Low (lower shale) 4 65-81 35-51 CH V. High Niobrara Smoky Hill Shale 45-55 20-32 CL, CH Moderate - High | o 1 Fort Hays Limestone I 1 Low | Carlile Shale o Greenhorn Limestone 30-100 15-52 CL, CH Low - Moderate Graneros Shale o 1

|Lytle/ South Platte I 1 Low | s 01 fc <£>o c o 41-145 19-114 CH,CL, SP-SM Low - V. High | o oo |Ralston Creek 1 26-54 CL, CH Moderate - High | * * Swell potentials based on plasticity index values (Chen, 1975). ** Based on literature review. - - No information 73 ER-4645 74

5. INTERPRETATION

5.1 Ranking Process

Based on the dominant bedrock characteristics, damage occurrences, and engineering properties (Tables 3, 4, and 5), each geologic zone was ranked for potentially heaving bedrock (Table 6). Each zone is ranked as either low, moderate, or high. These rankings indicate both the potential for heaving bedrock to occur within a particular zone as well as the amount of heave expected. This does not necessarily mean that units ranked the same have identical engineering properties. At boundaries between geologic units there is a high potential for heaving bedrock because of the markedly different engineering properties.

5.2 Characteristics Common to Each Rank

The characteristics that are common to each rank and the specific attributes of each geologic unit within each rank are summarized in Table 7. Plate 1 shows the location of each geologic zone and corresponding rank across the study area. The characteristics of each rank will be discussed in this section. ER-4645 Table 6: Summary of geologic unit characteristics and relative ranking with regard to heaving bedrock hazards, Douglas County, Colorado. u ' A C m £ m / -O C/3 I I I I ■“•5 u E-8 s ■a o 11 i JJ “ G 81

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drfE i i ■3* ■3§ 8 1 f « 'f 2 «§ s s § •§ « S f c S &l >;^ g* c « * * *8 ^ l s S=5 ■8 u .2 fr C JC ■2 -a § S I I S I2 i8 *f 1 1 E S§ *§ x> c SI 8 O

° s3 ■Si d E d O S >n a ^ « 1|1 1§ c E 2 * a 0 -O *

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_ 75 - - No information recorded. ER-4645

Table 7. Characteristics of each potentially heaving bedrock rank. U — T3 «- 3 03 .3 § s C «S t; & s 1 a 1 g is U J 2 © .2 *2 * f i i i g | J | 3 y •s i i dE u •§jr C9 3 " i i _ -i n ? £62 a £ A 11 ^ o ^ s - E -2 u ts ^ S Sjg e £ U g. 5 s U C -o « I/i i i c ^ cn * £2 m «■> o 5b £ b '5 E ’£ IE t'fi c U 4> C 2J

I 1 1 O o o *o u X CO , a .B 5 T i _ £> I I S E g Sf u E n i n i 5 g ^ S ^ g .52 H * 3 J5 E C■S 1j g *o 3 -H O J2 o uac *oO «*c -o ?P '=^ s u SC & 0 0 > UU U ___ CO S. £ S3 c£ . 'S >& H E g ‘E £ irf£ ! i S u S u o 'S 75 ^ s J u *.S 3*1 SS 7 * JS I ■«■C/3 o- 2 2 “ o -is •o S u as " B. — . B . "3 B / w w c/i O us E ■£ c 5 !2 o§ o«-) cC « 2 * 5 §1 S.a (U w g G 2 x £ ■2 6 w w 2 ■G JS 3 *o c 73 "O j l D 2 D fl> £ t h cj Q q> 73 4> ^2 0 T3 S <0

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X E S Si S E js t .E .5 « J3 J3 « w e .5 .2 O CQ CO C 1 S » 3 O »" u ° C 's g2 u u aa-c -a M .5 .5 M 3 C/5 •3 > 73 5 s > (+-« s>

USCS symbols represent the entire unit with the most prominent listed first. Liquid limit (LL) and plasticity index (PI) ranges represent only the claystone materials within each unit. 76 ER-4645 77

5.2.1 Low Heaving Bedrock Potential

Zones ranked as low heaving bedrock potential mainly consist of sandstones, non­ swelling siltstones, limestones, or shales with no significant occurrence of bentonite. Some interbedded units may contain finer-grained material with low swelling potential. Damage is rarely observed in these regions. Generally, the near surface weathered bedrock material is silt to sand-sized with low swelling characteristics. Atterberg limit values and ranges are low. These areas have a low potential for heaving bedrock, and if heaving bedrock does occur, differential movement is expected to be low. Geologic units that were ranked as low are described below.

5.2.1.1 Lytle and South Platte Formations

These formations consist of mostly sandstone with some siltstone and occasionally a kaolinitic claystone. Bentonite is neither observed intermixed with any units nor in distinct beds. Damage surveys were not conducted within this zone due to a lack of development. Discontinuous bedding, as well as the interbedded finer-grained materials with the sandstones provide this area with the potential for heaving bedrock. ER-4645 78

5.2.1.2 Fort Hays Limestone Member of the Niobrara Formation

The Fort Hays Limestone is a thin limestone unit with very thin beds of claystone with low swell potential. It contains numerous thin bentonite units, but not one of consequence. Damage surveys were not conducted in this area due to a lack of development. Heaving bedrock could occur within this unit due to the presence of thin, high-swelling units. However, most beds of potentially problematic material are so thin that it would be a low probability of them affecting structures built in this geologic zone.

5.2.1.3 Hygiene Sandstone Member ofthe Pierre Shale

The Hygiene Sandstone is composed of silty clays and clayey fine sandstones with low swell potentials. No bentonite layers have been observed. Damage has been infrequent in areas that have development across this unit. Most of the material is classified as low plasticity clay (CL) with some low plasticity silt (ML). The liquid limit for five samples tested in the Hygiene Sandstone ranges from 30-42 and plasticity index ranges from 10-25. Due to the variation of composition and swell potentials of interbedded material within this unit, there is a low potential for differential bedrock heave to occur. ER-4645 79

5.2.2 Moderate Heaving Bedrock Potential

Moderate ranked units contain materials with swell potentials ranging from low to high. Bentonite may be present. Damage is infrequently observed in developed areas with this rank and Atterberg limit values and ranges are highly variable. Heaving bedrock could occur within these areas. If heaving bedrock occurs, then moderate amounts of movement could be expected.

5.2.2.1 Ralston Creek Formation

The Ralston Creek Formation is primarily claystone with low swell potential, but some distinct beds of medium to high swell potential claystones occur. There is also interbedded non-swelling siltstone, gypsum, sandstone, and limestone within the claystones. No bentonite occurs here, but there are some high values of liquid limit and plasticity index recorded. Liquid limits for 3 samples ranged from 40-84 and plasticity index ranged from 26-54. Due to the variable composition as well as discontinuous bedding properties, moderate differential bedrock heave could occur within this formation. ER-4645 80

5.2.2.2 Graneros Shale, Greenhorn Limestone, and Carlile Shale

These formations contain interbedded high to low swell potential claystone with interspersed bentonite. The claystone varies from silty to sandy. Damage surveys were not conducted across this zone due to lack of development. Liquid limits from ten different samples have a very large range (30-100), as does the plasticity index (15-52). However, the majority of the material is low plasticity clay (CL). The highest values and ranges of Atterberg limits are in the Graneros Shale, but this formation cannot be distinguished from the others in the field area. The Greenhorn Limestone and the Carlile Shale seem to have similar characteristics as the Fort Hays Limestone and the Smoky Hill Shale of the Niobrara Formation. The variability of the beds within this zone makes it susceptible to differential bedrock movement. Also, where bentonite beds with high swell pressure do occur, they tend to be numerous and closely spaced and will be difficult to avoid beneath structures.

5.2.2.3 Smoky Hill Shale Member ofthe Niobrara Formation

The Smoky Hill Shale consists of low swell potential claystones, but, like the Ralston Creek Formation, there are some beds with high swell potential claystones. These claystones do not display Atterberg limit values as high as those in the Ralston Creek Formation, however bentonite is a common constituent. The claystone can also grade into non-swelling silty and sandy areas or contain occasional chalky limestone layers. Damage surveys were not conducted in the Smoky Hill Shale due to lack of development. Liquid limit values for seven samples ranged from 45-55 and plasticity index values ER-4645 81

ranged from 20-32. Most of the material is low swelling clay (CL), with some high swelling clay (CH). Due to the variability of the swelling characteristics of beds within this unit, there is a moderate potential for differential bedrock movement.

5.2.2.4 Upper Transition Zone of the Pierre Shale

This upper transition zone of the Pierre Shale has some moderate to high swell potential claystones as well as low swell potential material. This zone usually grades upward into the Fox Hills Sandstone, so most of the high swell potential materials are in the lower portion of the unit adjacent to the upper shale zone of the Pierre Shale. Damage is infrequent in existing developed areas. Two samples were tested within this unit, one in the lower portion, and one in the upper portion. The sample lower in the unit has a liquid limit of 90 and plasticity index of 50, while the upper sample has a liquid limit of 35 and plasticity index of 15. The majority of the material is low plasticity clay (CL), with some high plasticity clay (CH) prominent in the lower portion. There is a moderate potential for differential bedrock heave to occur within this unit, mainly in the lower portion due to the variability of the bedrock composition and engineering properties and existence of CH material. ER-4645 82

5.2.2.5 Fox Hills Sandstone

The Fox Hills Sandstone is a poorly sorted sandstone with minor amounts of low swell potential claystone, but no bentonite. Damage is infrequent where there is development across this zone. The claystones were not sampled and tested; however, previous work indicates that there may be some swelling materials within this unit and the beds are fairly discontinuous. Because of these properties, the Fox Hills Sandstone has a moderate potential for differential bedrock heave.

5.2.2.6 Lower Zone of the Laramie Formation

The lower third of the Laramie Formation is mostly a silty claystone with low liquid limits and plasticity index. Occasionally, a low to moderate swell potential claystone or non-swelling sandstone is encountered. Damage occurs infrequently in areas that are developed in the lower part of the Laramie. Liquid limit values for 5 samples ranged from 25-45 and the plasticity index ranged from 5-30. Most of the material is low swell potential clay (CL) with some low swell potential silt (ML). This zone is moderately susceptible to differential bedrock heave because of compositional heterogeneities and discontinuous bedding. ER-4645 83

5.2.2.7 Dawson Arkose

The Dawson generally contains cross-bedded sandstones, but an occasional lens or bed of moderate to very high swell potential claystone puts it into the moderate rank for heave potential. No bentonite has been recorded for this formation. Based on very limited damage surveys, damage occurs infrequently across areas that have been developed that correlate to the Dawson. Samples of the claystone material had liquid limit values ranging from 30-75 and plasticity index values ranging from 12-52. Grain- size distributions show that the sandstone consists of a poorly sorted sand (SP). Because of the possibility of encountering moderate to high swell potential claystones within the sandstones of the Dawson, there is a moderate potential for differential bedrock heave. If movement does occur, then it could be significant.

5.2.3 High Heaving Bedrock Potential

High ranked units are composed of primarily claystones with high swell potentials with beds of bentonite. Damage to structures is common. Atterberg limits generally range from low to very high. Heaving bedrock problems will most likely be encountered within these areas. ER-4645 84

5.2.3.1 Morrison Formation

The Morrison Formation is composed primarily of highly expansive claystones with interbedded silty sandstones as well as bentonite. The middle part of this formation is known to contain mostly smectite clay minerals, while the top and bottom parts contain kaolinite and illite. Because of these properties, the middle of the formation will most likely be the most problematic. Damage surveys were not conducted within the Morrison because of only recent development in this formation. Liquid limit values from 20 samples ranged from 41-145 and plasticity index values ranged from 19-114. Most of the material in this unit is a high plasticity clay (CH), with some low plasticity clay (CL) and poorly sorted silty sand (SP-SM). Because of the variety of compositions, very high swell potentials present, and discontinuous bedding, this formation has a high susceptibility to differential bedrock heave.

5.2.3.2 Lower Shale Unit of the Pierre Shale

This part of the Pierre Shale contains a majority of medium to very high swell potential material intermixed with silty sandstones, siltstones, and bentonite units with occasional selenite veins. Bedding is continuous, so problematic areas can be extrapolated along strike. Damage occurrence has been moderate to frequent in this unit in areas that have been developed. Liquid limit values from four samples range from 65- 81 and plasticity index values range from 35-51. Most of the material is a high plasticity clay (CH). This unit does not have as many compositional variations as the Morrison ER-4645 85

formation, but it does display a consistently high swell potential. Because of these properties, this zone has a high susceptibility to differential bedrock heave.

5.2.3.3 Upper Shale Unit of the Pierre Shale

The upper shale is similar in composition to the lower shale zone of the Pierre Shale. It contains a majority of medium to very high swell potential material intermixed with silty sandstones, siltstones, and bentonite units with well-developed selenite veins. The bedding is also continuous, so specific layers can be extrapolated along strike for a significant distance. Damage has been frequently observed in areas that have been developed across this zone. Historically, this zone has experienced severe differential bedrock movement. Liquid limit values for 12 samples range from 34-90 and plasticity index values range from 12-54. The majority of the material within this zone is high plasticity clay (CH). Bedrock composition and damage surveys make this unit one of the most susceptible to differential bedrock heave.

5.2.3.4 Upper Zone of the Laramie Formation

This zone contains mostly moderate to high swell potential claystone and some low swell potential claystone. No bentonite has been observed within the upper part of the Laramie, but there are some interbedded sandstones. Damage in this zone is moderate in frequency and the engineering properties have large ranges in values. Liquid limit values ER-4645 86

from five samples range from 35-85 and the plasticity index values range from 15-70. The majority of material is high plasticity clay (CH), with some low plasticity clay (CL). The presence of highly expansive claystone and the highly variable composition and engineering properties cause this unit to be ranked as highly susceptible to heaving bedrock. ER-4645 87

6. CONCLUSIONS

Three ranking categories are used to describe the potential for differential bedrock heave occurring within each geologic zone evaluated. Ranks are based on bedrock composition and dip, damage frequency, and engineering index properties. Geologic zones having a low ranking are the Lytle and South Platte Formations, Fort Hays Limestone member of the Niobrara Formation, and the Hygiene Sandstone member of the Pierre Shale. Heaving bedrock problems should not be expected within these areas. However, trenching may be needed to define the boundaries of these zones where they are in contact with potentially higher-swelling units. Moderate ranked areas include the Ralston Creek Formation, Carlile Shale, Greenhorn Limestone, Graneros Shale, Smoky Hill member of the Niobrara Formation, Upper Transition Zone of the Pierre Shale, Fox Hills Sandstone, lower zone of the Laramie Formation, and the Dawson Arkose. These units may be problematic. The distribution of heave-prone areas and the severity of differential heave may vary. Trenching is critical in order to quantify variability and identify zones where heaving bedrock may be a problem. Overexcavation and fill replacement may be necessary over certain zones to mitigate heaving bedrock hazards. Areas with high rankings are the Morrison Formation, lower shale unit of the Pierre Shale, upper shale unit of the Pierre Shale, and the upper zone of the Laramie Formation. All of these formations have moderate to highly expansive claystones as well as large variations between individual beds or bedding zones. Differential bedrock heave should be expected in these regions and overexcavation may be necessary in most cases unless otherwise indicated by trenching and other site-specific investigations. ER-4645 88

The map of these zones should be useful to developers, engineers, planners, or home buyers for identifying where a heaving bedrock problem is likely to occur, and therefore, where special site exploration and/or design may be required. This map is intended to be a broad based tool that can be used by those in the private sector for planning and real estate, as well as professionals dealing with utility installation, road construction, and foundation design, or as a valuable aid in the county or city planning process. ER-4645 89

7. AREAS FOR ADDITIONAL STUDY

Several research areas should be investigated to further define the engineering properties of the bedrock units delineated in this study so subsurface conditions can be predicted more accurately. More samples should be collected from each geologic unit and tested following the procedures for this study (summarized in Appendix A). Formations that particularly need more testing include the Ralston Creek Formation, Lytle and South Platte Formations, Greenhorn Limestone, Graneros Shale, Carlile Shale, and the Fox Hills Sandstone. The range in values listed in Table 3 should be further augmented to provide a complete range of values to represent each unit. With more information, it may be possible to define engineering units and heave potential more accurately. Additional testing methods could be used to supplement this set of data. Clay mineral analysis using x-ray diffraction could be used to determine the mineralogic components (percent smectite, illite, kaolinite) of each unit. The swelling behavior of some soils is strongly affected by the presence of clay minerals and knowledge of the specific constituents of each unit could assist in a more accurate prediction of its behavior. Hydrometer tests could be used to determine the percent clay fraction, so that activity values can be compared. This may be a more accurate way of predicting swell percentages than the methods employed in this study. As an alternative to estimating swell percents, suction tests could be performed to directly measure volume changes. Damage that has resulted from heaving bedrock should be further inventoried and studied to determine the contributing factors to the problem as well as design subsurface investigation techniques that are more effective. This has already been started with ER-4645 90

several homes with rebuilt foundations in Jefferson County by installing monitoring devices that indicate the direction and rate of ground movement around the foundation. ER-4645 91

8. REFERENCES

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American Association for State Highway and Transportation O fficials (AASHTO), 1978. Standard Specifications for Transportation Materials and Methods of Sampling and Testing: 12th Edition, Washington, DC, Part I, Specifications, 828 p.; Part II, Tests, 998 p.

American Society for Testing and M aterials (ASTM), 1995a, Annual Book o f ASTM Standards. Soil and Rock (D: D 420 - D 4914. Volume 4.08. Section 4: American Society for Testing and Materials, Philadelphia, PA, 984 p.

American Society for Testing and M aterials (ASTM), 1995b, Annual Book of ASTM Standards. Soil and Rock (II): D 4914 - latest; Geosvnthetics. Volume 4.09. Section 4: American Society for Testing and Materials, Philadelphia, PA, 628 p.

B a l l e w , W.H., 1957, The Geology of the Jarre Canyon Area. Douglas County, Colorado: Unpublished MS Thesis T-850, Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO, 86 p., scale 1:24,000.

B a r n e t t , P.R., 1961, Snectrographic Analysis for Selected Minor Elements in Pierre Shale. United States Geological Survey Professional Paper 391 -B: U.S. Government Printing Office, Washington, DC, 10 p.

B o w l e s , J.E., 1992, Engineering Properties of Soils and their Measurement: McGraw- Hill, Inc., New York, 241 p. ER-4645 92

Bryant, B., M iller, R.D., and Scott, G.R., 1973, Geologic Map of the Indian Hills Quadrangle. Jefferson County. Colorado. United States Geological Survey, Map GQ-1073: U.S. Government Printing Office, Washington, DC, 7 p., scale 1:24,000.

C a d ig a n , R.A., 1967. Petrology of the Morrison Formation in the Colorado Plateau Region. United States Geological Survey Professional Paper 556: U.S. Government Printing Office, Washington, DC, 113 p.

C a m a ch o , R., 1969, Stratigraphy of the Upper Pierre Shale. Fox Hills Sandstone, and Lower Laramie Formation (TJpper Cretaceous! Levden Gulch Area. Jefferson Countv. Colorado: Unpublished MS Thesis T-1242, Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO, 84 p.

C h en , F.H., 1975, Foundations on Expansive Soils: Elsevier, New York, 280 p.

Chen and Associates, Inc., 1972a, Preliminary Subsoil and Geological Reconnaissance. Southdown at Roxborough Subdivision. Roxborough Park. Douglas County. Colorado. Job No. 8432, August 24, 1972.

Chen and Associates, Inc., 1972b, Preliminary Subsoil and Geologic Investigation for Proposed Lake Roxborough Subdivision. Roxborough Park Development. Douglas County. Colorado. Job No. 8473, September 25, 1972.

Chen and Associates, Inc., 1973a, Soil and Foundation Investigation for Proposed Condominium Development. Project Area I. Roxborough Downs. Roxborough Park. Douglas County. Colorado. Job No. 9215, March 13, 1973.

Chen and Associates, Inc., 1973b, Investigation of Slides at Roxborough Park. Douglas County. Colorado. Job No. 9539, June 29,1973.

C o b b a n , W.A., 1956, The Pierre Shale and Older Cretaceous Rocks in Southeastern Colorado, In Guidebook to the Geology of the Raton Basin. Colorado: Rocky Mountain Association of Geologists, Denver, CO, pp. 25-27.

C ob b an , W.A. and Scott, G.R., 1972, Stratigraphy and Ammonite Fauna of the Graneros Shale and Greenhorn Limestone near Pueblo. Colorado. United States ER-4645 93

Geological Survey Professional Paper 645: U.S. Government Printing Office, Washington, DC, 108 p.

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APPENDIX A - DESCRIPTION OF LABORATORY TESTS ER-4645 107

APPENDIX A - DESCRIPTION OF LABORATORY TESTS

Several laboratory tests were conducted as part of this study. Test procedures generally followed ASTM standards with minor modifications, which are detailed below.

A.1 Natural Water Content

The water content test was performed immediately after return from the field and followed ASTM D 2216-92. Samples were stored prior to testing in air tight containers between approximately 3 and 30°C in an area that was not exposed to direct sunlight. Each sample of weathered bedrock weighed at least 20 grams to ensure that the material accurately represented the subsurface conditions.

A.2 Natural Dry Density

The natural dry density was determined by the drive-cylinder method described by ASTM D 2937-94. Samples were collected in 4 inch long brass tubes with an inside diameter of 2 inches. Modifications were made to the standard testing procedure because of the resources available to this study and the need for portable sampling equipment. The brass sample tubes were hand-driven into highly weathered bedrock near the ground surface using a steel drive head which attached to the brass sampling tube. The drive head was hammered with a 5 pound mallet, which forced the sample tube into the subsurface. ER-4645 108

The samples were stored in a humidity room until testing was conducted. The sample tubes were opened and the length of the sample that was collected in each tube was measured along with the diameter of the sample tube (inside diameter). The dimensions of the sample tube did not always correspond to the dimensions of the sample. Measurements of the length of soil sample in the brass sample tubes was approximate (±0.1 inches) due to irregular sample surfaces. Average values were assumed for irregular surfaces. The sample ends were trimmed flat at the ends of the sample tube. Then, the contents of each tube was emptied into a pan and weighed. The water content was then determined according to the procedure previously described in Section A.I. From the sample dimensions and the water content, the volume, wet density, and then dry density of each sample was determined by the following equations:

Sample volume: V = 7iD2/4*L where V = sample volume, ft3. D = sample diameter, ft. L = sample length, ft.

Wet density: pwet = mass of wet soil/ volume of wet soil where pwet = wet density, g/ft3.

Dry density: pdry = [pwet / (1 + w)] * (0.0022 lb/g) where p ^ = dry density, pcf. w = water content. ER-4645 109

These densities may not represent the properties of the bedrock at depth because these samples were collected less than 2 feet from the ground surface in bedrock that was highly weathered.

A.3 Atterberg Limits

The liquid limit, plastic limit, and plasticity index of samples were determined according to ASTM D 4318-93 with a few modifications. The first modification and the most significant is that the samples were air-dried before testing according to ASTM D 421-85. The liquid and plastic limits of some soils that have been allowed to dry before testing have shown considerably different values than those obtained on undried samples (Karlsson, 1977). ASTM recommends not permitting samples to dry before testing if the liquid and plastic limits of soils are going to be used to correlate or estimate the engineering behavior of soils in their natural moist state (ASTM D 2217-85). Because the samples used for this study were collected close to the surface, the material may have gone through several wetting and drying cycles so air-drying the sample probably would not make a difference in the laboratory test results. The sample preparation procedure for Atterberg Limit testing was conducted as follows:

1. Weigh out approximately 400 g of moist sample (500-600 g if there is a significant amount of >#40 sieve). 2. Air-dry the sample completely (generally takes 3-5 days). 3. Pulverize the sample using a ceramic ball mill. 4. Sieve through #40 sieve with an automated shaker (dry sieve) for 5-10 minutes. 5. Weigh out 250g ± lOg of air-dried, pulverized sample passing the #40 sieve. ER-4645 110

Another modification to the standard dry preparation method, ASTM 421-85, was the use of a ceramic ball mill rather than a mortar and pestle because it is less destructive and it is less likely to crush fine aggregates into unnaturally finer particles. A modification to ASTM D 4318-93 (liquid limit determination) was the use of the Casagrande grooving tool instead of the ASTM grooving tool. The ASTM grooving tool for the liquid limit test does not allow for any control of the height of the groove, and therefore will give inconsistent results.

A.4 Particle-Size Analysis - Mechanical Method

A variation of the mechanical analysis (ASTM D 421-85) was that the sample was not divided into two portions with the No. 10 (2.0 mm) sieve because very little material was greater than 2.0 mm. The same procedure that was used to prepare samples for Atterberg limits was used here, with the specification that the samples of material weigh at least 500 g. It was not necessary to pulverize the samples in the ceramic ball mill or with the mortar and pestle to separate the grains. The ASTM D 422-63 test method was used to determine the distribution of particle sizes in each sample. For this study, the distribution of particle sizes larger than 75 pm (retained on the No. 200 sieve) was determined by sieving. Particle sizes smaller than 75 pm were not determined. ASTM procedures require a sieve No. 140 (0.106 mm) be part of a full set of sieves, but it was not used for this study. Sieving was conducted by a mechanical device that kept the material moving across the sieve with lateral, vertical, and jarring motions. Each ER-4645 111

sample was run for 10-15 minutes or until no more than 1 mass % of the residue on a sieve passes that sieve during 1 minute of sieving.

A.5 Classification

The Unified Soil Classification System (USCS) (U.S. Army Corps of Engineers, 1960) was used to classify soils for engineering purposes, which corresponds to ASTM D 2487-93. This system is based on laboratory determination of particle-size characteristics, liquid limit, and plasticity index. When the laboratory test results indicated that the soil was close to another soil classification group, the borderline condition was indicated with two symbols separated by a slash. This was necessary when material was plotted on the plasticity chart within 2% of another classification group. The first symbol is the one based on the standard. For example, CL/CH would indicate that the sample plotted within the CL boundary, but was within 2% of being classified as a CH. ER-4645 112

APPENDIX B - FIELD DATA

This appendix contains a series of tables summarizing data collected in the field. Sample location, type, depth, and descriptions are detailed for the 83 samples collected as part of this investigation. Further explanation of the data presented in this appendix is given in Section3.3.3 of the text. ER-4645

FIELD DATA Date: August 24-1995 S m e i £ * 3 2 S £ Z ^oi q CO£ f CO I z I m a. UJ J _ j u LU

UJ m

co a: 5 CO 2 J C J T 00 CO z s CO co CO 12 CO _ro JS "E a . CO CJ) "w s * © c d (0 o E © . o tS o o , > o 5 © 0) c o C JT _© LU 3 t CL oo O O © TO N o c © © Q-| Q. © -

CO S J 0 CM CO TJ I "E 00 J3 s c Q. TO ' o I— I c co 0) E o o © © © c TJ I* UJ in z CM 1 00 3 o © c O) . Q © c CO Q.

J3 j _© J2 TO CO 00 CO -C Q. Q. -C ~ CM co o > © © TO© N o TO > © to TO © © .£ != C O to TO £ ° E 3 5 C l oZ © © C © . o

O JO C 3 J t L. .tc CO 3 ~ e 1 CO 00 CM CO © c to c 0 j ro N S © TO © O o s *5 CL « TO A) TO E V E o Q. ) to N . 8 a z

r _j3 _ro ‘c 00 co a: co JO CO TJ N J to © © © o £ c © c o c >• c c E o © © © 3 to © Q. Q. © CO CD m co J T ro © © TO « o ^ I w e TO>* C C TO>* © 3 ill E.E I-- in © Q. CL CO J .E TJ 00 CD O -r- CO CM -Q 0 3 J JO © c TO © © c ?> © CO S o ? C TO . > © CO CO 0 5 5 «*= •= 1 .*eg © o . a .E ® " g & « TJ O 3 J Q_ w' r j to z j '© ;g £ S £ 1 i s c TJ c © b ® © c © O T C . .52 .— © 0 ©o w © E o « o TO c © to a> ©

8 & 8 l © © © : : _ ^ to © o —

113 ER-4645 114

IDO) O) Jk TJ TJ CD ro CO to in' C c TJTJ c CM ro ro 'ro 'ro c c to" CO TJ TJ § ro to to to ro 'ro ro ro k_ a . 3 d) ro XJ XJ XJ Q. C to to 3 u . Li. © © c 3 ro ro < co ro co",® LL. ro 4 ro c ro 'E ro ro ro b i z ■* P 0 0 c ro E ro p co" E c o " ! E E E ro o> TJ 3 o ro kwa ro 2 k. ^ ro J wro E 2 u.ro TJ ro ro tj" I— ro ■*5 ro ro ro « ro ro ro a ro Q Q. to _ i co _ j _ i 2 - J >» _ i >> _ j c —t XJ k. TJ TJ >_ ro 3 ro >- to C C CO TJ o d ro ro « ® ro ro ro ro ro ro a . ro ro CL o c a . 1 s . ro a . co a CO CL ro r - a . a . Q. CL c a . W CO o 0 “ ■ ro to 3 r CP UJ x ) 3 XJ —1 c 3 c - J "ro 3 "ro 3 3 '3 0 La k. O) Q a> CD 3 CJ) ro CD ro b> b ) _c 8 c 8 ¥ - e c > c > c ro c —I ro ro ro > t j > ; i s 0 T3 1 l CO TJ co k— to o TJ TJ . TJ TJ TJ 0 TJ TJ CO o ro ■ 8 ^ 5k ro > , ro c* ro c ro CD c x j *3 -Q JC XJ JC XJ 5 XJ $ XJ XJ 3 in O 8 - TJ * TJ TJ S -D 2 TJ k.0 TJ k_ro TJ ro to ro ro ro ro c JZ JZ to ® .Q JC XJ £ .£ 5 to > .<0 c" CO c . a CO CO 0" CO CO o '3 ■5 £ '3 5 k. 2 3 $ 5 0 0 0 '5 to '3 X) o> XJ o> 0 o> 0 CJ) CD CD O) ro c . c c c 2 c ro c ro cro c ro XI XJ '■= > . >* a . CJ) CO . CO CO . CO CO CO CO E ro >» >> TO 2? ^ TJ ■5 3k TJ jk imm ro c iS c ro c 3 c ro c ro c ro c ro ro o 3 O 3 0 3 0 3 0 3 0 3 0 3 0

a d z UJ co CO CO CO N- 0 T— CO CO “ CO O 0 co CO O CO O 2 5 3 < Z h- < ) d i ( Q 1 1 d o w n DEPTH .8 .8 d o w n .75 .75 d o w n 0-1 d o w n 0-.8 inside 0-.3 inside 0-.3 inside 1 1 SA M PL E 1 Q I 1 down | .3 inside I | -J UJ c c c UJ XI XJ X) XJ XJ UJ 0 . ro ro ro a . rou. > .> 2 > rok. 2 kro LL S *i_ < CD Q a 0 Q 0 0 0 CO

UJ CC _J UJ CL m T- CM t— CM y— CM CO ■

8 5 o £> 0 0 N. r - ad Cd 0 d TJ ro E ro CO ro CO ro CO n CO c CO ■Q t - 1 - h - JC E Z TJ ro CO ro tr> ■e co o CM XJ CM ro CO 2 ro h - 6 E d d to < ro ro ro 0 ro ik o CO CO CO 0 k_ ro ro o to 2* ■g 5 i — Ik ▼* CO to 0 5 £ CO $ to CO ro CO ro z TJ ro ro CO ro T“ UJ CO UJ UJ ro CO ro CO z

UJ —I Dd O UJ ~ n CO CO TT CO P 5 1 - J - 1 - CO 3 UJ Z t - ER-4645

FIELD DATA Date: Auqust26-1995 2=iu tb - ifcfc E “ = I u u i= Z _ i s CO LU O !uOf CO t i O Z CO 3 < 1 S _1 Of UJ LU S x lu CO . Q uu o: O d) CO CO CO o I— = (0 ■= O JO CO T3 UJ CO CO d) ^ c 5 > o TO <5 O Q, CO CO • > 0 CO _ <0 6 o o >» 4? ^ = (0 ■= O (X CO >• co > » P I c —I <0 CO CO *D o CO o 3= *? •O O = CO CO CO 5 llj S ° ■S CO d) 0 d) CO o CD co >. ^ >. o> co ? 5 a >, co P >> o Ti « ) s e XI ■a o >N E 3 c ' XI !E — O —I o CO d) 0) c CO cu CO CO . > d) o * cu c > co > 5 >> v. CO l co c >. d) . 9?- —I —I I— CO E CD

3 £ .3 j t OC CO CO CO o Q 5 co ra o OT c d) c O o 3 t_ CO d) 5 c c o 12 E CO - r < = CO 0= @ 8 LU JO — 3 t O 5 JC Q CN JO T3 UJ CO CD co H CO Of CO o> CO o CO O CO LU 2 m CO CO H CM co cu d) >> N o c (0 ? CO o c O co d) o >. (0 w_ O) 2 >» CO d d> CO TJ JC Q CM 2 ■cf sz O CQ d co d> d> CO o c o CO CO c E 5 $ CO 3 E o CO d> O) l_ CO > 115 ER-4645

FIELD DATA Date: A uqust31- 1995

SAMPLE TESTHOLE SAMPLE SAMPLE DEPTH Mc TIN NUMBER LOCATION NUMBER TYPE (FT) NUMBER SOIL DESCRIPTION to T13 SW 1/4 NW1/4 Sec.20 T7S R68W GRAB .5 inside 132 clay, silty, fine sand, It. brown; layers of sand, clay, north of streambed on hillside and limonite bedding difficult to distinguish(N5W 35E); Dawson Arkose

ZS GRAB .5 inside 152 clay, silty, gray; Dawson Arkose

S3 GRAB .5 inside 124 clay, silty, gray; Dawson Arkose

S4 GRAB .5 inside 133 clay, silty, chocolate brown; Dawson Arkose

SS GRAB .5 inside 147 clay, plastic, gray, very hard; Dawson Arkose 9S eg GRAB .5 inside clay, very sandy, gray, very hard; Dawson Arkose CO T14 SW 1/4 NW1/4 Sec.20 T7S R68W GRAB 0-.5 137 sand, medium course, light gray, varying layers of north of streambed on hillside inside Fe-stained sand,clay,silt(N25W 90E); Dawson Arkose "I— S2 GRAB 0-.5 clay, silty, gray, shaley, varying layers of Fe-stained inside sand, clay, silt (N25W 80E);Dawson Arkose T- 0 S3 GRAB 0-.2 00 sand, medium course, light gray; Dawson Arkose inside CO T15 NW1/4SW1/4 Sec.20 T7S R68W DRIVEN 2 down 139 shale, silty with some clay and fine sand, light gray, by waterhole @ old mine site .5 inside undistinguished bedding; Lower Laramie S2 GRAB 2 down 130 shale, silty with some clay and fine sand, light gray, 0-1 inside undistinguished bedding; Lower Laramie S3 GRAB @ surface c 0 c a) coal, possibly high sulfate content; Lower Laramie 116 ER-4645

FIELD DATA Date: September 1.1995 • L - t CL CO Z O 3 CO ^ l- 1 0 _i UJ CO 3 < co . UJ a I - oc UJ J Z pJ UJ 5 ^ 5 Q CO CQ . UJ a: O « CO o ? CO uj c CO 5 0 - h = CO CO o: CO CO CO J ° UJ M W CM c « ^ -8 CO o ” co z o jz 12 ro 5 t: t: 5 5 * -P•* reS -o 3 (A —I 3 re w 2 5 re , 3 p cm in JZ o o JZ J2 re « o xi 3 CO —I re 3 re*re P >< E > p c X 5 0 a) h- CO CO llj c CO l"- a: (O oo - JO <- re re ° S — d CL M z s

o .E co £ 1 t t "to re d) re d o « co CO jo O) CO .ts II

§ *” 2 z. (0 c 0 : ) )

s q- Is ?.! o o 2 « O > JO W | o) CO re .t; a) II

o >, co CO CO re UJ £ CO ad co O J t CO ? 5 r-= CO -C ■C >. JU '®H 3 S a € s. "8 « ■S -o « ® '3 £ 5s P P 5s cd s d O CO CO co co >* o 2-D > 1 £•9» CO XI CO >> t> E 3 P OT Q_ ..S 5 £ CO 0 . k . CO . re re C o CO o E co CC = co C CO CD•S OC CO CO CO CM UJ P i $ 5 0 c h- co “ o co 2 o 1 c o c CD Z JZ JZ 1 ^ C ■Q p - ■— a -s s. 8 « -g -O J2 « ‘3 £ O CO CO co co >. p* o s* T5 e 3 P Q_TO .a S. 2 2 o 0 r c c r L- . CO . O "a CO

z j 1 ^ ■S' 8 c -C ■2 CU T3 a cl ■a t> 2 £ co co co co > 0) O COCO > 2 s?re .c c >* o . Q a) 2 § re O “ CO Q. re o . u • >, . : x CO IS < d

m o o m ° co 'S UJ cu CO 05 XJ r~ C ^ - t S'? J CL ■JZ CO ~ -c ^ re ^ E o p S c a. o o re 2 a>£ o aj •*- * £ CO*CL COIS13 z J § b> .2 a) >. re . . JC . re .£ S3 o re « - - « o c co 5 0 « K XJu- ? 1 •a S ■gE e *- re re c o co cu is re N o c o CO CO w >, £ IS o £ 2 . cn re c re re re t > re 2 CO re ■ re. 3 i s .

o CO .E LL. CO 2.2 b ^ S I g- •o S n i t ° § § ° re re c co re re P O) 2 to .2 5 0 .. C >ire -cz re e co re >* ‘S re t > re 2 CO I re ■ .P ; re . re % V

117 ER-4645

FIELD DATA Date: SePtem ber2-1995 Ui u lu z § F CO H- X O —I LU LU C 2 < X< LUQ. I - LU o t - t a- LU /5 Z 2 03 OC

Ll. 'c ■o 3 7 2 ~ To jO c C . > (0 5 CO0 _ (0 i > cu c cn (0 i_ cu co >

o CO T3 ) O I- CO (0 = 5 r-~ X CO 00 @8 Li- X "55 •e £ O 3 t! • CD E c o c CU co >- CD o n

8 C . JV JV — c .e -c co0 ' » > cu E c cn I 1 w « n o cn n cucn c co o> CO cn£ co P . . cu tr\ - c c - ^ cn cn CO cu \Z CO C CO CO 3 CD L— CN 05 ^ l— CO 3 7 § LU £ § tn ~ Is" ® IT X3 C/5 CN n i ^ •“ _ 3 7 CN jz N- CO^ 3 CO ^ S a: > o d> >*- o 2 >, >, 0 3 o C O - > i ) o cu

cn CO CU £ = c £ 'co as 2 # 3 Q >* -Q u- co ° £ £<55 i i cu> -I $ 2 £ E. co5 cncn,2 „ c > r* cu a *p co^ c x J CO CN 0 ) X CNCNfvj ^ — 3 7 in "3 in 05 o 5 CO O •- > i 3 CO 1 03 = Li. Li. -£* —_ o X -Q J= J2 T~ E ^ o> o ^ o co E CO® CU 8 3 O) O ^ C ° co « O) L. w I o to co Q. • c - - - >*

CO CO CD "co CN 5 ■“ 3 7 n JZ ■N- ~ c o "s i c o 2 2 3 cn > CN m CU o ~ 5 = •55 X •o 2 I £ I CO I c To E CO c CO © o "55 co 0 o CO CO o co P 3K 05 c CO cu CO cu > o

a * E CO N’ W_ £ CN sz "3 c o 5'co 3 7 C cn

CN CU CO CO . 2 - .c 2 CO 2 5 0 CO co * * x i x : : x i x 05 0) CO CO CO CO o °» «0"co CO CO cn CO UJ - u r- ES 05 X COCO ‘cn ■g CO IX) a cu

X : x : x To £ of 0) E cu c o o c cn CO CO CO CO o °> o cu c o o Q. 0 Q. ) '55 3 7 JO 3 7 CO CD £ CN "co 73 cn

m O) O) in CM "5 jy <5 .N (0 XI 13 -C= O X W T> o a} O >» '■£ — Oaj (0 Q o 4= O CM u. a) ©' c o E 3 "55 . o = 0 ? £ Koi S 2 2 < Q “ E ~ “■> UJ tc t O

liJ UJ UJ LL. a. a. if: CO

UJ K _ l UJ CL ffl 5< 3 2 CO CO 2

§ £ 0 0 ^ co W i t o >* CO c CO " 5 £ £ §1^0 CO 0 5 CO 0= co s P c o> a) 2 *“ $ ►- Q- — i n o m o m o T3 tO T - Q. O "C u -o' u a) ra (U 3 a> o CO o CO - CO c >* »- "2 s 9- ^ **r o - s 2 $ £ $ s 5 -2 z -c z o z = 5 o .c 3 ° ■c UJ UJ o CO CO c UJ_l CC _ O UJ x 1:0 a jjfzs i ER-4645

FIELD DATA Dale: ° ctober27-1995 t & | l c _ i r J i - a F m Z to UJ - H l U h* X O J _ Z CO 2 2 CO L CO UJ CL I t - C UJ < 13< r UJ =rl UJ £ l 0 UJ CO J T 5 " -Q JZ JD2 ; • a £ o $ c Q. g ” § > 4= co 5 ^ 05 l . CO O CQ CO CO Tf T - cd T in co I— X CO 5 3 * 05 co Q 2 .Q ■a 5 = 2 £ £ co 3 5 « 5 c o v = o> o5 ro

0 2 UJ O ~ CO CO UJ § 5 5 CM 05 O—' to Q t CO I— . — CO m oo oo m *3 p DC CO CO O) .O JQ "53 f £ CO j 3 = Uj ? o o 05 c c o 2 >* (0 c 05 05' ~ m CO i— to a: CO $ mft. o 05 CO Z J Z J * 1 ■O £ =!> * 2 - > > »-< 5 O 05 o w o o ® ® o « £ S O > a) a> c o . co T3 CO O) 5 « CO C (0 c 2 2 c CO z. S . . . (0

CO ~ T— «si- to a: $ mSo . — 05 CO CO > 2 5 I 5 1 4 * •2 CD 5 *J= a . Q ' S e a) co ■—co - . >C ° £ 0) . a | 3 3 m co

UJ co — DC o CO ^ £ - 4 _ 05 o t CO CO T3 T3 “ c c ■“ £ 2 c ? 3 ^ 5 w 05 CM O s i c c co o c o o c 5 3 0 ' 5 0 2 s * c g o E § § 2:- 05 > 05 n 2 ) a 5 0 c CO 05 I CO B T3 o a co

O T_ CO UJ o «i= co ■o 2 2 s • 5-s CO ^ £ 2 — ■o 05 3 S ~ o 05 O E o a - E c ° £ CD « O 05 05 5 O 05 S ' Q . . Q ' w S » 2 is s 2 ^ = (U CO 05 E 3 £ c CO 05 c . : > 3 05

0 i 2 : x 2 1 2 afco 5 CO C S to £ H CO DC CO co m 05 CO 2 S Z. CM UJ CO * 12 12 * * J 2 CO ■ >* 45 T5 « £ co o ! i 05 * 9 ® « T3 3 E CD 2 2 £ u r o CO E 05 E 3 05 -a 2 ) X x; TJ 05 c ^ J 3 UJ C 05 (0 05 05 05 c Q. 05 P c C5 CO c a. 2 o O 0) o 05 05 3 O 0 T3 T5 05 05 O O) 2 l_ L_ UJ CO — P * P CO DC CO i T_ •M’ JZ _>» S3 2 05 c S UJ 05 CO CJ CD o «* u. ' COS o COc 05 (0 c « O)

3 120 ER-4645

FIELD DATA Date Q ctober27- 1995

SAMPLE TESTHOLE SAMPLE SAMPLE DEPTH Mc TIN

NUMBER LOCATION NUMBER TYPE (FT) NUMBER SOIL DESCRIPTION 2 SO NE1/4 NE1/4 Sec 22 T9S R68W S14 Grab none claystone, shaly, light to medium gray, trace of silt, roadcut east of road plastic; Morrison

NE1/4 NE1/4 Sec 22 T9S R68W S15 Grab SO none claystone, bentonitic, very plastic, light gray, roadcut east of road oxidized; Morrison

NE1/4 NE1/4 Sec 22 T9S R68W S16 Grab SO none claystone, very plastic, medium gray, with silt;

roadcut east of road Morrison SO c 0 c 0 NE1/4 NE1/4 Sec 22 T9S R68W S17 Grab ) claystone, very plastic, medium gray, slightly silty; roadcut east of road Morrison

NE1/4 NE1/4 Sec 22 T9S R68W S18 Grab SO none claystone, very plastic, light to medium gray,

roadcut east of road trace of silt; Morrison SO c 0 c 0 NE1/4 NE1/4 Sec 22 T9S R68W S19 Grab ) claystone, bentonitic, very plastic, light gray, roadcut east of road slightly silty; Morrison

NE1/4 NE1/4 Sec 22 T9S R68W S20 Grab SO none claystone, very plastic, medium gray, trace silt; roadcut west of road Morrison

NE1/4 NE1/4 Sec 22 T9S R68W S21 Grab SO none claystone, bentonitic, very plastic, light gray, roadcut west of road trace of silt; Morrison 121 ER-4645 122

APPENDIX C - DATA FROM GEOTECHNICAL REPORTS

This appendix contains a table of engineering properties that were taken from previous geotechnical reports within the outcrop zone of sedimentary rocks that are capable of differential bedrock heave. Properties included on this table include natural water content, natural dry density, classification, material description, grain-size distribution, Atterberg limits, % swell (and surcharge), swell pressure, penetration, unconfined compressive strength, and the geologic unit that the sample was taken from. All of these reports were conducted in the northern part of Douglas County within the Kassler quadrangle. The location of the test holes that samples were taken from are indicated on Plates 1 and 2. ER-4645 123

5 5 1 i 1 i fi i E 1 1 E UNIT 1 5 i I s GEOLOGIC

| § 1 (P«*) 8 8 STRENGTH UNCON. UNCON. COMPR.

g c « § 1 3 i 8 Ii I § i § i 1 s 1 I 8 S S PENETRATION

I 1 I I 1 1 I f i 8 i i 8 8 a.(X '» o | § | § | i § i I § § § i | si f EXPANSION EXPANSION 0 | Z e ^ 0 tn O O p O pto e too p o n s s o.3 e o a

0 1a. s 8 5 8

? 0 0 d Ii s 8 * ATTERBERG ATTERBERG LIMITS

| 8 s & 8

<%) 3

§ GRN GRN SIZE DISTRIBUTION

i f ! ! 1 i i E f I i i i f l I £ I i i i f i i J A ( i I, i i i i « i i "E 1 A £ a a Si S; 1; 1; I 3 i t l l ff i i fj f! ft | i rs If I I 1 i If rf r| rl fji r| f I f| 1 *5 u 8 £* 8 l l I i **! i H I f f h i f I f I f f i f n MATERIAL MATERIAL DESCRIPTION i i h u u h % I i i | f i f I I i | | 8 * 8 I I f f o 5 H 11 I 15 ol l8 !£ § f 1 OI l> fU. i i i l l zo S S

CLASSIFICATION 3z 0 p p 0 p s 8 s = i (P*0 8 i I § i o 1 8 o S I 5 DRY 8 i DENSITY ■ 0 0 p a K« 0 S

WATER « CONTENT

0 0 0 0 0 0 s W 9 9 - 0 5 - - " • 5 5 ■ - • DEPTH SAMPLE K •" 3 £ -- - - 0 - ~ "" N. • 0 = 5 t 5 2 9 - - **!"

i e e § e 1 | e S e 8 8 8 | 8 8 i 8 8 I

REPORT 1 I i f i l I I I I 1 I i o ! I GEOTECHNICAL ER-4645 124

!l ft i a ll a i ER-4645 125

5 5 5 5 5 5 & 5 5 UNIT 5 5 5 5 5 5 5 5 f 5 5 GEOLOGIC (P*0 STRENGTH UNCON. UNCON. COMPR.

1 s 1 I i 1 § i i i i I S i (blowc/inch) PENETRATION a : 8 UJ§ t i 8 B 1 § B I 8 § I § 1 a.CE »' « i « > * «

a.O § 1 § 2 f 2 § 2 1 a§1 1 i 2 § 2 § 2 § 1 1 2 § § EXPANSION EXPANSION I Q p p 2 2 5 o p p O p p O 2 I s 2 d S S 2 2 <3 2 g £ £ ATTERBERG ATTERBERG UMITS s * (%) £ § GRN GRN SIZE DISTRIBUTION s £ 1 I 1 1 1 1 I ? I 1 i p P ”5 s i 1 £ I* I'fc I i s'i I 1 I a I i 5 i £ I 5 1 * If 1 | j f ! 11 I i (I l l s a1 f l l l II l l 11 | t: i •e• a a s a a « a a a a S 5 1^ | l 8 | f l | ! *1 1-1 I i II {* !> J i l i h ( i i i i fig f I | f I s f i i l i f MATERIAL MATERIAL DESCRIPTION i t 1 i i i i l l ! f 1 i 1 ! i !! i i h i l f h l l i ! i * 1 I f l i t I 1! MI I s ! II ii II II ii II II ii II ii i i II fit l i t i l l III ill I i ! 3 1 f *1o S " ois.I i l i t Xo 5 o iZ

CLASSIFICATION z

8 8 8 o o s 8 8 8 8 8 o 8 8 8 8 8 8 8 8 8 § (P*0 DRY DENSITY

O o p o p O o e o 0 e O O O O o d 01 a» d d d <%> n 8 a R N

«e at a a a (It) * * * 2 2 5 2 » 2 2 a 2 2 2 DEPTH * * SAMPLE

" - - - -- ” • ■ <0 ------

TEST HOLE " NUMBER

i | 1 i 1 1 i i 1 I 1 I 1 1 | 1 I t 1 1 I s 3 3 □ REPORT UJ 5 2 2 2 UJ UJ GEOTECHNICAL ER-4645 126

___ 5 UNIT 5 5 5 5 5 5 5 5 5 1 I 5 & & S 1 * & GEOLOGIC (psf) STRENGTH UNCON.COMPR.

O 9 « e i § 1 I § § g 5 § (blows/inch) PENETRATION

< : 2 c § i § I 1 i I § § | § 1 1 I 1 § 1 1 Qijs: a *

z j 0 J w aC 2 •&I 8 § § 1 2 § 8 § § §§ § § § § §§ §§ 1 t § i a 2 0) a C i n (0 « tf>

! £ •> 0. ) c c i a e 4i!I -*

u.1 :!

i GRN GRN SIZE DISTRIBUTION 1

s 1 £ 1 L 1 i ii si si 'B I ■5 i E •§ t! 5 1 5 1 ^ 1 •a"E ll fg s 2 ^ 2 ll la ■e ® 1 'E !* ii |> ll *E 2 il It ll ll Is I a II s a ll ll t i ll ll II |i il 9 B 9 B 9 * 9 B s a ■ <8 ! II II * f ?i !I *1 if ill ill in 1*1 ill i!i 2 i *1 *1 *1 ill !i I* i il. Ml l!i fit fit MATERIAL MATERIAL DESCRIPTION i • 1 Hi hi it i j 1 H-i *1 iilf I U* 1*1 ! ifi I «f III lit III III in ill ll lu fl! III il! till 1 ill ill o 9 II in 3 I # 5 I f m 2 0 C z F 4 1 1 L o X z (1 9 « * d d d d d o c ! o o

o O o 5 s s 8 o © 3 8 8 8 8 Si 8 8 6 8 o S (P»0 DRY DENSITY

© o O o © o to oi © « <0 Ok ai d “ d d § § R R R R s S a WATER CONTENT

jr a ak f* 8 8 2 R (9 («) s *** * a * * a DEPTH SAMPLE

* s <0 2 2 2 " - - "-- - - "" • TEST HOLE NUMBER

1 1 1 1 1 i i 1 i i i I | | I | I 1 I i I 3 1 s i S' 3 S' REPORT 2 2 d ui £ J f u. u. £ GEOTECHNICAL ER-4645 127

UNIT I 1 1 i $1 i i i I i I I i i I i 1 i 1 I GEOLOGIC

g t f*- CL 8 « 3

g 8 8 8 8 8 ATTERBERG ATTERBERG LIMITS n jj lb1 fc s ai ¥ K A <*) A a 3 ai s § 3 GRN GRN SIZE DISTRIBUTION

L J !| rj M rj r I 1 rj 1 * 1 4 a *! 1 i h£ z il il il I if i i i H o ii : I si fl I 1 I I si -8 I U II ii £ 1 1 1 1 i a jt £ * I I Si 1! ? j! ; 7? 71 7t a p ii 11 1 fl Hi p ii 1 1! II ii P i a a a a a a £ fij u i 111 £ 1 £ l i l l IIS i £ i i i i i l MATERIAL MATERIAL DESCRIPTION P fi Pi (1 i it I ill iri I 1 I ij II $Ip * M a a 1 5tt J!l I St IIIIII 1 II 5 1 h sis Ii!til a o O o Io ii II Ii o P g z § J9 j ! 3 ! < < <

2 X -J u § O - o o d o § o d o 5 * «* CLASSIFICATION s o o o 3 l

n (D 8 2 2 8 & § o at s 8 s 8 (prt) DRY DENSITY

• o • r*» a IO 2 o b « b b a A b (%) 5 3 3 s

WATER * CONTENT

r- A 9 a at A to (*> 2 - m 2 a 5 S 2 - - A " " - 2 DEPTH SAMPLE

IP o ID A a o 2 2 2 - - - 2 = 2 2 - = - 5 TEST HOLE NUMBER

| | i 8 i i i i i i i | | 1 | | | I i 1 i i | 8 i i 1 8 | i s' s' REPORT 1 £ i s i 1" 2 5 * GEOTECHNICAL ER-4645 128

e e e E E UNIT 1 I 1 1 I J 5 & s i I f s s s GEOLOGIC (P«0 STRENGTH UNCON. UNCON. COMPR.

Z O § i If 1 § § § e § | § 1 § § s 8 s § § a.UI2 3at !3: e uiJI t | I § § i a0LC 1 1 «» i i 010* |iIfl\ ii\ 1 1 § 8 § § § § § § s I i: i i5 ^ o o p. i: e V s 5 3 3 5 o 3 a o 1i £ 3 8 s 8 s i)‘ & Pi 3 s au Q 8 5 8 Pi 8 R f -* 3 p) 1 S Si | 5 8 8 ■ I - s * s GRN GRN SIZE DISTRIBUTION 1 ■E2 5“E i £ 3 i j 1 2 £ 1 . f!l r ffl fl! ill • 21i l K si ft- $ *§ i s II it It s i! | fi 5ii * |H s f If isfl isI1 1* *{l i 1 l)f li W fl [ll i ! H ll 11 jf ji fix ii f1 i | I i i i i

MATERIAL MATERIAL DESCRIPTION 1* ft it il if!, i! 111.!! 11*11 iifi If! I ii H □|i s 1 o|2 ° f iii JSli SI Hif g |j| giii n i l Hi III 111 31]if! 3! ll a oil hi o P £ PC X s s L s < a 6 I X X X « d d o d o o c 1 *

a a § 8 8 O R § (P»l) DRY g 3 Si 5 DENSITY

° K e <0 0 <%) R 5 8 2 3 a a = WATER CONTENT

DEPTH * SAMPLE

2 a o O o - •r - -- « TEST « HOLE " “ - - < i i NUMBER * 1 I 1 I 1 1 1 i i I 1 1 1 g i | g o o'

REPORT S' o o s i 1 I* i i i (0 if GEOTECHNICAL ]* ER-4645 129 ER-4645 130

E E 4 E 1 4 e 4 J I £ & § i I 1 I I 1 & GEOLOGIC GEOLOGIC H H " | UNIT UNCON.COMPR. UNCON.COMPR. ! STRENGTH ! STRENGTH ' (Prt) to I g 8 1 § S 8 8 i 1 i § 8 i 1 £ 8 I 8 g (biowsAnch) PENETRATION ft! 11 B i 1 i I 1 (Lct I i * i 3 i 1 i f i

czo i l i 1 i 1 i 1 I s § § § § § § § 8 EXPANSION I EXPANSION « oz q o o e» w) s o 3 2 d ° ? 5 3 d A 1a y A o sf s s 3 2 » S n e E s 8 ft 8 ATTERBERG LIMITS ATTERBERG 1 s 8 8 8 K 8 i 5 <%> -- - 3 - GRN SIZE DISTRIBUTION DISTRIBUTION SIZE GRN I 5 A f i f i !& H £ If I f i t | I t l ! i II i f l i f S £ ff f l I f I f i f i f 1 f | 4a £ I s "E £ t & §2 ! i i I f i f i l *4 H P H i f ! i n | j i i t i t n ii i i i f P I f i | i 1* s S a ! 1 131 *1* f h i* I n If i i f i 3 3 | J i f 11| f « i ! I f ! j ! ! i | | MATERIAL DESCRIPTION MATERIAL 1 HI 111 1 | f f l ‘1 i l l 1*1 £M 2fi i Pf l i f II I : i i t t*.3 i f la 111 o il i l i l l ko il i i o E ! i i i s i l i t o a a s ! i I f i I n 5 f l h i II ft I <0Xo z X X i 8Q. d d o 5 2 2 CLASSIFICATION 3z Ho * o o 0 5> 8 & 8 o 0 o 3 r d d (P»0 8 S

DRY 1 DENSITY

0 q o ; r-: «ri« 0 (%) 0 ft 1 3 ft ft 0 WATER CONTENT a o A 01 A (") - " 0 « j ft -- * 5 - - s - DEPTH SAMPLE o ft & £ s 8 & ft n * 3 5 ma TEST HOLE s i I i i a £ m NUMBER 1 1 1 I 1 1 i i 8 | | 1 I i i 1 i I 1 | i o'1 o' o’ o’ | ! | REPORT sU) 8 8 s 3 0s i s i s s GEOTECHNICAL ! I $ 2 I i i ! ER-4645 131

UNIT I i i i 1 5 & i 1 1 i 1 I § SI 5 % 2 I GEOLOGIC GEOLOGIC I

O z f i l Dz Z s * I s s 1 1 § s s s § 1 1 § 5 s ;S z 21 s (LUJ c. j < 1 1 i 1 1 I 1: « 1 1 i » I ■ i I ■ ! « 8 flL ' i 1 i § 1 § i i § 1 § § 1 i § i § i t EXPANSION > 7

:; g n q o oe q s 5 t s s ri o b 5 b ° >i

; ■* 1 a.£ s ic5 ti ^ Q3 £ s 4E: "* | 8

1 S § GRN SIZE DISTRIBUTION 1 DISTRIBUTION SIZE GRN - £ f i f § s-l 3 i s .£ f ! J 1 H M I 1 M ll Jls a I 1 i 1 S | 3 £ s . i |1 1 fJS fll *!f, c u M. i i f 11 i l f l j l l ff il 3 II j i& If ! l n P 1 III II lil i 1| i | i i l i l r ! r l 1 w ff rl fl §• I i * s f * si ! i s ! i | £ f Ii IIS] i i I i i II 1ii i i ! if ii II ii I MATERIAL DESCRIPTION MATERIAL M i r f ill \ \ h i i s' i i i l I f i i I f 11 n i l III H i i ! i i fill ulliU il H i sill< 1 5iss lii f ill 5l l|s£ P s i3 S 2 pc § 25 2g a o Z I u m u> 3D b § 8 l b s N (P*0 § 8 I i £ DRY i i I 1 DENSITY

oo 9 m q o q o a»e ai b KIA a o q piV 3 TO 2 5 s 2 R WATER CONTENT

9 9 a R? a» (") - s R - ** A R -- “ s DEPTH SAMPLE 0 0 O W 3 i § a5 i i TEST HOLE s 1 1 i i £ i i 1 1 s i i I NUMBER 1 I | s 5 1 i | S | I s 1 | S I I 1 1 s a a a' a 1 S | 2

REPORT 3 i 1 1 1 GEOTECHNICAL i i 1 i i 1 1 ER-4645 132

UNIT 1 f & 1 1 t GEOLOGIC

I I 2 1a.* s0 s £ 1 | £ |

W ft 1 GRN GRN SIZE DISTRIBUTION 1 1 t f * I Is 3 E. i i 3 . S I1 i i 3 | f|i u IjlK $ 1 w isV 1 if rf I1 1 1 rl; iifi *M 2 m f 1! II 11 1 II MATERIAL MATERIAL DESCRIPTION f-Sli t i l ! 1 Mi 111Mi IsMi 1 If I i oil 1 0 iii 1i/i Q d CLASSIFICATION 3z p 3 o» at

(psf) 3 DRY I DENSITY « A <%> «0 3 3 3 WATER CONTENT

(«) ai at - 2 2 2

DEPTH * SAMPLE 1 1 A TEST HOLE HOLE i l i i NUMBER 1 1 J 1 1 i ; I 1 1 1 1 j | REPORT

GEOTECHNICAL 1 1 I ! ER-4645 133

APPENDIX D - LABORATORY TEST RESULTS

This appendix contains a table and a series of charts summarizing data generated by laboratory analyses. Tests that were conducted include natural water content, natural dry density, grain-size distribution, Atterberg limits, and USCS classification. Material descriptions are also included along with the identification of each geologic unit that the samples were from. Further explanation of the data represented in this appendix is given in Section 4.3 of the text and in Appendix A. The location of the test holes that the samples were taken from are indicated on Plates 1 and 2. ER-4645 134 J 3 3 3 Klu Klu Klu Klu Klu Klu Kpu Kpu Kpu Kpu 1 Kpu Kpu Kpu 2 2 2 2 TKda TKda TKda | 2 TKda 2 2 TKda TKda TKda TKda TKda TKda TKda TKda Zone** Geologic Material Description sand, medium gray light course, medium sand, clay, very sandy, gray gray sandy, very clay, 1 clay, silty, fine brown light sand, fine silty, clay, gray silty, clay, gray silty, clay, brown chocolate silty, clay, gray plastic, very clay, sand, medium white gravel, with course, medium sand, clay, silty gray sandy, and silty clay, yellow-green light silty, clay, white course, medium sand, white course, medium sand, gray dark plastic, clay, clay, plastic, trace green-brown sand, v. fii. of trace plastic, clay, clay, silty, gray silty, clay, brown light silty, clay, brown light silty, clay, clay, brown clay, brown clay, yellow-brown sandy, and silty clay, clay, green-gray clay, gray light clay, plastic extremely bentonite, brown light clay, brown light clay, yellow-brown sandy, and silty clay, clay, green-gray clay, green-gray clay, clay, plastic, brown plastic, clay, brown plastic, clay,

&H X X X X J J 04 O- X £ X J cn CJ o cn

tn 30.5 52.0 25.9 68.8 28.5 42.5 43.8 33.3 30.0 54.3 29.0 Plasticity Index Index (%) 52.8 32.8 34.5 29.5 75.0 46.8 45.2 85.0 62.5 24.9 45.7 42.0 49.5 56.0 50.2 76.8 46.5 Atterberg Atterberg Limits Liquid Limit Limit (%) | | 89.5 OO e'­ OO

tn SO SO os OO »n OS o\ Os © oe OO Dry (Pel) Density Natural 9I 811 1 8 (9TI) (9 01) 001 OS OO 901 r-^ OS Os OO Os

13.3 12.0 OO 15.5 cn OO 15.7 11.3 14.4

17.4 OO 15.0 11.4 OO 19.9 9 6 30.8 (%) Water Natural 9.3 9.3 (9.8) Content* 16.7 16.7 (16.4) 16.4 16.4 (23.4) 28.5 28.5 (30.7) 19.0 19.0 (21.8) S I I I IS S 1 [ 61IS S 1 | 81IS S 1 | 91IS ZS S I I IS I | II T6S2 T5S1 T2 S3 T2 T2S2 T14S1 T13S5 T13S1 T12S1 T2S1A Sample Number | | S4 T13 | S6 T13 | | S3 T13 | | S2 T13 | | S2 T12 | | T5S4 | | T7S1 | | S3 T5 | | T4S2 | | T5S2 | | T4S1 | | T3S1 | T3S2 | | T2 SIB ER-4645 135

3 BO BO BO BO BO BO OBO BOU OBO UBO Kll Kpl Kpl Kpl Kpl Kns Kpt Kpt Kns Kns 1 Kns Kpu

5 5 Kpu 2 Kpu Kph Kpu S Kpu

TKda TKda 1 & U TKda TKda 1 £ U Zone** Geologic 1 Material Description Material clay, clay, occasionally silty, light brown clay, occasionally silty, light yellow-brown bentonite, It. gray, pure clay, clay, plastic, olive green-gray clay, some silt, light brown silt, clayey, yellow-brown clay, plastic, olive green-gray clay, plastic, olive green-gray, waxy clay, plastic, olive green-gray, waxy clay, silty, light brown-gray clay, clay, plastic, olive green-gray clay, silty, green-gray clay, plastic, olive green-gray clay, silty, gray clay, occasionally silty, light brown clay, plastic, olive green-gray bentonite, It. gray, very pure clay, clay, silty, sandy, gray clay, plastic, green-brown clay, plastic, green-brown clay, silty, light brown-gray clay, plastic, olive green-gray clay, silty, light gray silt, silt, clayey, fine sand, light gray silt, clayey, fine sand, light gray clay, silty, sandy, gray clay, plastic, green-gray clay, clay, silty, gray sand, medium course, white SP CL CL CL CL CL CH CH CH CH CH CH CH CH CL ML uses CH-CL CL-CH CH-CL Classification MH-ML/CH-CL

OO 00 C4 o 5.3 12.5 16.3 43.0 25.6 51.3 31.8 21.7 21.7 36.1 37.6 20.9 33.9 28.6 22.7 28.7 ■*r 25.8 Plasticity Index (%) Index

009 809 sec 75.0 60.5 50.2 54.5 50.2 63.5 45.2 50.2 33.6 40.5 55.5 28.0 47.0 48.5 41.9 00 Atterberg Limits Atterberg Liquid Limit (%) Limit

(%) tn Fines (%) 92.6 Sand Gradation 4.3 (%) Gravel 86 78

106 r-

103 OO Dry (pcf) Density Natural | | 97

hO 00 00 00 b0 00 b0 00 00 00 00 00 00 00 b0 00 00 bo oo 00 oo 00 2 2 2 2 2 2 2 o o o CJ CJ cj o cj o o M >—i fcC NS bd u £ Zone** Geologic nsC <-

£ bb 13 cj a* *3 s* S5* 2 *8 «* & 00 ■o (3 2) 00 & ob i o. ob X T3 jn ob bp £ § IS t £ 2 M i ra cn 13 *o •a op X b) X b) ‘53 '53 » c C .SP ■s US In 0 CS *53 •o i-ca £ IS ~ 2 *55 ‘53 W cn 00 ob T3 "O 00 cj ■S 6 6 cj «T £ 1o 2 £ w o o o u I E-s u u | § X O ’5 Material Description bb bb 00 bb bb s o o O > o IS op « •- E T3 —! !§> o ' J 0 o* J2 ft- 5 ‘55 ’53 33 *<2 *■*3 .2 £ i i 4>* o d cj £ V3 cn .¥ £ ¥ u O J a iS a 1 cq JS 2 '2 J* ‘2 ’53 G 2 o ’2 o "S. ■p. ‘cn CO P. CU *2. o o o 13 0 o *£ c c -f c c e u «j O 8? 1 V J* V j ? & J* J* § -S £ *■« 33 w m X x "ot X o x X 13 X o 13 13 13 o

(J W On o o o CN ON >n o ON ON *5 * 00 •n r^- r * cn r - 3 . i j | | Atterberg Limits

8 o . s ^ fa* w

■O / - s 68C O' v® (*2 w

Gradation " 3 __ > .Sifan

2 £ o Dry (pcf) Density Natural

© so •rf- NO NO NO On CO oo n; cn «o 00 m o p v i NO © on 00 © NO d o «o CN ON d o 00 vl

(%) (N m r r m CN m CN cn CN CN CN cn m cn ro cn

Water Jc ou Natural

Content* c3 . g

CN

tN Plasticity Chart for the Upper Shale Zone of the Pierre Shale o o o o O n 00 % -ClPilSEIJ (%) o m o CN oo O CN m o o o IT)o NO o r-- OO o o ON o O O CN o m o n IT)o o -

Liquid Limit (%) 137 ER-4645

CN © Plasticity Chart for the Lower Shale Zone and Hygiene Sandstone (+) of Pierre Shale a. o< © © O © n OO © (%) xapuf Ajpijseij xapuf (%) r-~ © VO © in © © © cn CN © CN © cn © © © VO © © oo o © © © o o cn o o in o

Liquid Limit (%) 138 ER-4645 O cn Plasticity Chart for the Smoky Hill Shale member of the Niobrara Formation o o o Os oo © (%) xapuj Xippstqj xapuj (%) o o VO o m Tj- o o cn o CN cn o CN o j t o m o vo o r" o oo o o ov o O CN o cn o o m o -

Liquid Limit (%) 139 ER-4645

CN Plasticity Chart for the Upper Transition Zone of the Pierre Shale o ON © 00 O (%) xapni XippsBidxapni (%) O VO o o m o - n ■ CN © ooo CN o m o o o VO o r"- o oo o ON o o O CN o m o o o

Liquid Limit (%) 140 ER-4645

CM Plasticity Chart for the Upper and Lower (+) Zones of the Laramie Formation Os oo («/„) K3pnj XjpiJSBIJ o o m o + u \ >■' v CM o O o o CM o o 00 OS CM

Liquid Limit (%) 141 ER-4645

CN Plasticity Chart for Clay Lenses in the Dawson Arkose jll. oo (%) xspni XipiiSBU xspni (%) o o in O O CO o CN o o © CO © CN © m © NO © © oo © O © © © CN © CO o o O m n

Liquid Limit (%) 142 ER-4645 143

ino

o

om t/5 o CN

O o

o ON

o OO

o

o Liquid Limit (%) VO

o in

o *a TT O cn

oCN

o O OO o o o o o CN ON 00 m cn CN (%) xapnj ER-4645 Plasticity Chart for Morrison Formation CN O o O ON o 0 0 o (% ) xapni ) (% O' o VO o o o T T o CO CN o o o VO CN o O C wo o o o o o CN ' O 00 o ON © o CO o o o

Liquid Limit (%) 144