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HomeMy WebLinkAbout1.07 Soils and GeologyMRI May 2012 Appendix r Soils and Geology Soil Report Geologic Site Assessment 6 Limited Impact Review Appendix F [This page was left blank intentionally.] USDA United States Department of Agr culture o\ RCS Natural Resources Conservation Service A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Aspen -Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Hydrologic Soil Groups February 27, 2012 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://soils.usda.gov/sqi/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (http://offices.sc.egov.usda.gov/locator/app? agency=nrcs) or your NRCS State Soil Scientist (http://soils.usda.gov/contact/ state_offices/). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Soil Data Mart Web site or the NRCS Web Soil Survey. The Soil Data Mart is the data storage site for the official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means 2 for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface 2 How Soil Surveys Are Made 5 Soil Map 7 Soil Map 8 Legend 9 Map Unit Legend 10 Map Unit Descriptions 10 Aspen -Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties 12 13—Atencio-Azeltine complex, 3 to 6 percent slopes 12 55—Gypsum land-Gypsiorthids complex, 12 to 65 percent slopes 13 92—Redrob loam, 1 to 6 percent slopes 14 106—Tridell-Brownsto stony sandy loams, 12 to 50 percent slopes, extremely stony 15 116—Yamo loam, 12 to 25 percent slopes 17 References 19 Glossary 21 4 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil -vegetation -landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil scientists classified and named the soils in the survey area, they compared the 5 Custom Soil Resource Report individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil - landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil -landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field -observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. 6 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 7 .47Z .01. °LOL ,.9£ .l l .LOI N 0 M 0099£4 0099£4 004£9£4 00££9£4 00Z£9£4 001-£9£4 000£9£4 00629£4 00979£4 00L9£4 00979£4 0099E4 M 009£9£4 'v 0) M 009£9£4 004£9£4 00££9£4 00Z 9C-17 001. 9£17 000£9£4 00629£4 OOLZ9E4 00929£4 00929£4 i0 N <+) N 0) M ..EZ.OL aLOL Map Scale: 1:8,440 if printed on A size (8.5" x 11") sheet. 0 0 0 N O O 0 0 0 0) O z ..9E dl .LOl Custom Soil Resource Report MAP INFORMATION MAP LEGEND 8,440 if printed on A size (8.5" x 11") sheet. Very Stony Spot The soil surveys that comprise your AOI were mapped at 1:24,000. / f § G � � Warning: Soil Map may not be valid at this scale. >0 ( /§®¥ 2 /« .0C= kee� 727 E,so • E - 2£ co 0 co f\\% =e_f \)c 2-C CD {»\« E'E2 /\/\E -moo E tr„ §7 E£ a- 3 /#7 Soil Map Units Special Line Features 4 Special Point Features Short Steep Slope 3 Political Features 0 e Closed Depression = t / co E§ / { a) o . % 0 / D ci) CO k \ CO CO § 9 ri ' o§ 8 a n \ / \ /< \ / / / 3 'a c § ~ z m < a §/2 m § 0 `22 ° G )f§ Eo COk c Q_2 /± 9&% 22 aj\.2� a« . co Z§@ a>- #e -c�/e/)k Ek E 00 /eco 2{ f2, /( 670', // ®@ '08 0> \02 ƒ2 u 0 (f 0 33 Water Features Streams and Canals Transportation Marsh or swamp Mine or Quarry Miscellaneous Water Local Roads Perennial Water Rock Outcrop / CO G CO E.' 1E 3a \{E \ko ©.co0 k0 00 %y 0) < +"/I E 2 co a E= . )=—a t]0 0222 oe // o 77±0 o . oEEE &S{o Severely Eroded Spot 8\ < \ F/). CO # / N » • + > + 2 111 #4,k m Custom Soil Resource Report Map Unit Legend Aspen -Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties (C0655) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 13 Atencio-Azeltine complex, 3 to 6 percent slopes 28.1 16.1% 55 Gypsum land-Gypsiorthids complex, 12 to 65 percent slopes 87.3 50.1% 92 Redrob loam, 1 to 6 percent slopes 2.8 1.6% 106 Tridell-Brownsto stony sandy loams, 12 to 50 percent slopes, extremely stony 23.8 13.7% 116 Yamo loam, 12 to 25 percent slopes 32.3 18.5% Totals for Area of Interest 174.2 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic 10 Custom Soil Resource Report classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha - Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. 11 Custom Soil Resource Report Aspen -Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties 13—Atencio-Azeltine complex, 3 to 6 percent slopes Map Unit Setting Elevation: 5,900 to 6,500 feet Mean annual precipitation: 15 to 18 inches Mean annual air temperature: 44 to 46 degrees F Frost -free period: 105 to 120 days Map Unit Composition Atencio and similar soils: 60 percent Azeltine and similar soils: 30 percent Description of Atencio Setting Landform: Terraces, alluvial fans Landform position (three-dimensional): Tread Down-slope shape: Linear Across -slope shape: Linear Parent material: Alluvium derived from sandstone and shale Properties and qualities Slope: 3 to 6 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum content: 10 percent Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm) Available water capacity: Low (about 4.9 inches) Interpretive groups Land capability classification (irrigated): 4s Land capability (nonirrigated): 4s Ecological site: Rolling Loam (R048AY298C0) Other vegetative classification: Rolling Loam (null_60) Typical profile 0 to 10 inches: Sandy loam 10 to 20 inches: Sandy clay loam 20 to 30 inches: Gravelly sandy loam 30 to 60 inches: Very gravelly sand Description of Azeltine Setting Landform: Alluvial fans, terraces Landform position (three-dimensional): Tread Down-slope shape: Linear 12 Custom Soil Resource Report Across -slope shape: Linear Parent material: Alluvium derived from sandstone and/or alluvium derived from shale Properties and qualities Slope: 3 to 6 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum content: 10 percent Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm) Available water capacity: Very low (about 2.4 inches) Interpretive groups Land capability classification (irrigated): 4s Land capability (nonirrigated): 4s Ecological site: Rolling Loam (R048AY298C0) Other vegetative classification: Rolling Loam (null_60) Typical profile 0 to 9 inches: Gravelly sandy loam 9 to 16 inches: Gravelly loam 16 to 60 inches: Extremely gravelly sand 55—Gypsum land-Gypsiorthids complex, 12 to 65 percent slopes Map Unit Setting Mean annual precipitation: 10 to 15 inches Mean annual air temperature: 39 to 46 degrees F Frost -free period: 80 to 105 days Map Unit Composition Gypsum land: 65 percent Gypsiorthids and similar soils: 20 percent Description of Gypsum Land Properties and qualities Slope: 12 to 65 percent Depth to restrictive feature: 0 inches to paralithic bedrock Capacity of the most limiting layer to transmit water (Ksat): Very low (0.00 to 0.00 in/ hr) Maximum salinity: Slightly saline to strongly saline (8.0 to 32.0 mmhos/cm) Available water capacity: Very low (about 0.0 inches) Interpretive groups Land capability (nonirrigated): 8s Custom Soil Resource Report Typical profile 0 to 60 inches: Gypsiferous material Description of Gypsiorthids Setting Landform: Mountains, drainageways, hills Landform position (two-dimensional): Shoulder Landform position (three-dimensional): Mountainflank, side slope Down-slope shape: Linear Across -slope shape: Linear Parent material: Mixed colluvium and/or mixed residuum Properties and qualities Slope: 12 to 50 percent Depth to restrictive feature: 10 to 40 inches to paralithic bedrock Drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately low to high (0.06 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum content: 10 percent Gypsum, maximum content: 12 percent Maximum salinity: Very slightly saline to slightly saline (4.0 to 8.0 mmhos/cm) Available water capacity: Low (about 5.5 inches) Interpretive groups Land capability (nonirrigated): 8s Typical profile 0 to 8 inches: Fine sandy loam 8 to 23 inches: Fine sandy loam 23 to 39 inches: Fine sandy loam 39 to 43 inches: Weathered bedrock 92—Redrob loam, 1 to 6 percent slopes Map Unit Setting Elevation: 5,800 to 7,200 feet Mean annual precipitation: 16 to 18 inches Mean annual air temperature: 40 to 44 degrees F Frost -free period: 85 to 105 days Map Unit Composition Redrob and similar soils: 85 percent Minor components: 10 percent Custom Soil Resource Report Description of Redrob Setting Landform: Flood plains, terraces, valley floors Landform position (three-dimensional): Tread Down-slope shape: Linear Across -slope shape: Linear Parent material: Mixed alluvium derived from sandstone and shale Properties and qualities Slope: 1 to 6 percent Depth to restrictive feature: More than 80 inches Drainage class: Somewhat poorly drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: About 18 to 48 inches Frequency of flooding: Rare Frequency of ponding: None Calcium carbonate, maximum content: 10 percent Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm) Available water capacity: Low (about 4.3 inches) Interpretive groups Land capability classification (irrigated): 4w Land capability (nonirrigated): 4w Ecological site: River Bottom (R048AY236C0) Other vegetative classification: riverbottom (null 19) Typical profile 0 to 14 inches: Loam 14 to 20 inches: Stratified loamy sand to stony loam 20 to 60 inches: Extremely cobbly loamy sand Minor Components Fluvaquents Percent of map unit: 10 percent Landform: Flood plains 106—Tridell-Brownsto stony sandy loams, 12 to 50 percent slopes, extremely stony Map Unit Setting Elevation: 6,400 to 7,700 feet Mean annual precipitation: 12 to 14 inches Mean annual air temperature: 42 to 44 degrees F Frost -free period: 85 to 105 days Map Unit Composition Tridell and similar soils: 45 percent Custom Soil Resource Report Brownsto and similar soils: 35 percent Description of Tridell Setting Landform: Mountains, terraces Landform position (three-dimensional): Lower third of mountainflank, tread Down-slope shape: Linear Across -slope shape: Linear Parent material: Alluvium derived from sandstone and/or colluvium derived from sandstone and/or alluvium derived from basalt and/or colluvium derived from basalt Properties and qualities Slope: 12 to 50 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 6.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum content: 25 percent Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm) Available water capacity: Low (about 4.0 inches) Interpretive groups Land capability (nonirrigated): 7s Other vegetative classification: Pinyon -Juniper (null_10) Typical profile 0 to 2 inches: Stony sandy loam 2 to 14 inches: Very cobbly fine sandy loam 14 to 25 inches: Cobbly sandy loam 25 to 37 inches: Very stony fine sandy loam 37 to 60 inches: Very stony loamy sand Description of Brownsto Setting Landform: Terraces Landform position (three-dimensional): Tread Down-slope shape: Linear Across -slope shape: Linear Parent material: Alluvium derived from basalt and/or coarse textured alluvium derived from calcareous sandstone Properties and qualities Slope: 12 to 50 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 6.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum content: 30 percent Custom Soil Resource Report Maximum salinity: Nonsaline (0.0 to 2.0 mmhos/cm) Available water capacity: Low (about 4.2 inches) Interpretive groups Land capability (nonirrigated): 7e Ecological site: Stony Foothills (R048AY287C0) Other vegetative classification: Stony Foothills (null_81) Typical profile 0 to 11 inches: Stony sandy loam 11 to 30 inches: Very gravelly sandy loam 30 to 42 inches: Very gravelly loamy sand 42 to 60 inches: Gravelly sandy loam 116—Yamo loam, 12 to 25 percent slopes Map Unit Setting Elevation: 6,200 to 7,500 feet Mean annual precipitation: 10 to 14 inches Mean annual air temperature: 40 to 44 degrees F Frost -free period: 85 to 105 days Map Unit Composition Yamo and similar soils: 80 percent Description of Yamo Setting Landform: Fans, mountains Landform position (three-dimensional): Lower third of mountainflank Down-slope shape: Concave Across -slope shape: Linear Parent material: Colluvium derived from sandstone and/or colluvium derived from shale and/or colluvium derived from gypsum Properties and qualities Slope: 12 to 25 percent Depth to restrictive feature: More than 80 inches Drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum content: 10 percent Available water capacity: High (about 9.5 inches) Interpretive groups Land capability classification (irrigated): 6e Land capability (nonirrigated): 6e Ecological site: Rolling Loam (R048AY298C0) Custom Soil Resource Report Other vegetative classification: Rolling Loam (null_60) Typical profile 0 to 8 inches: Loam 8 to 14 inches: Loam 14 to 60 inches: Loam 18 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep -water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://soils.usda.gov/ Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http://soils.usda.gov/ Soil Survey Staff. 2006. Keys to soil taxonomy. 10th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http://soils.usda.gov/ Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://soils.usda.gov/ United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.glti.nrcs.usda.gov/ United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430 -VI. http://soils.usda.gov/ United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://soils.usda.gov/ 19 Gtech HEPWORTH-PAWLAK GEOTECHNICAL GEOLOGIC SITE ASSESSMENT PROPOSED IRMW WASTE TRANSFER STATION AND RECYCLING PROCESSING FACILITY 1058 COUNTY ROAD 100, NEAR CARBONDALE GARFIELD COUNTY, COLORADO JOB NO. 112 021A FEBRUARY 23, 2012 PREPARED FOR: MRI ATTN: DON VAN DEVANDER 1800 MEDICINE BOW COURT SILT, COLORADO 81652 TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - 1 - SUMMARY OF FINDINGS - 1 - PROPOSED DEVELOPMENT - 2 - PROJECT SITE CONDITIONS - 2 - REGIONAL GEOLOGIC SETTING - 3 - CARBONDALE EVAPORITE COLLAPSE CENTER - 4 - GEOLOGICALLY YOUNG FAULTS - 4 - PROJECT AREA GEOLOGY - 5 - EAGLE VALLEY EVAPORITE (Qc/Pee and Pee) - 5 - SEDIMENTS OF SOPRIS BOWL (Qc/Tsb) - 6 - LANDFORMS AND SURFICIAL SOIL DEPOSITS - 6 - Man -Disturbed Ground (af)• - 7 - Youngest River Terrace (Qt1): - 7 - Older Fans (Qf2): - 8 - Younger Fans (Qfl): - 8 - Colluvium (Qc): - 9 - GEOLOGIC SITE ASSESSMENT - 9 - POTENTIAL HYPERCONCENTRATED FLOWS - 10 - POTENTIAL ROCKFALL - 10 - SINKHOLES - 11 - General Character of Evaporite Sinkholes: - 11 - Potential Sinkhole Risk: - 12 - EARTHQUAKE CONSIDERATIONS - 12 - LIMITATIONS - 13 - REFERENCES - 15 - FIGURE 1— PROJECT SITE LOCATION FIGURE 2 — REGIONAL GEOLOGY MAP FIGURE 3 — WESTERN COLORADO EVAPORITE REGION FIGURE 4 — GEOLOGICALLY YOUNG FAULTS AND LARGER HISTORIC EARTHQUAKES FIGURE 5 -- PROJECT SITE GEOLOGY MAP FIGURES 6 and 7 — LOGS OF GEOLOGIC UNITS IN THE EXPLORATORY BORINGS PURPOSE AND SCOPE OF STUDY This report presents the findings of a geologic site assessment for the proposed IRMW Waste Transfer Station and Recycling Processing Facility to be located at 1058 County Road 100, Garfield County, Colorado. The 35 acre project site is about 1 mile east of Carbondale as shown on Figure 1. The purpose of this study was to review the geology in the project area and assess if the geology could present constraints and potential hazards to the proposed waste transfer station and recycling facility. This study was performed according to our January 25, 2012 proposal to MRL A field reconnaissance of the property was performed on February 20, 2012 to observe the site conditions and collect field information needed to evaluate and map the project area geology. In addition, we have reviewed published regional geologic information, looked at aerial photographs and reviewed our previous nearby experience. Using this information, an assessment of potential geologic constraints and hazards to the proposed facility was performed. This report summarizes the information used in our evaluations, describes our assessments and presents our findings. SUMMARY OF FINDINGS This study shows that geologic conditions that could present an unusually high risk to the proposed waste transfer and recycling facility are not present at the locations of the proposed project components. Although the potential risks are not unusually high, the proposed project components are exposed to some geologic risks related to hyperconcentrated flows, rockfalls, sinkholes and earthquake strong ground shaking. The need for risk mitigation will depend on the degree of risk acceptable to the owner and governmental regulatory agencies. An assessment of potential geologic risks and the need for risk mitigation are discussed in the Geologic Site Assessment section of this report. Job No. 112 021A Gertech -2 - PROPOSED DEVELOPMENT The proposed waste transfer station and recycling facilities will be located on a 35 acre parcel in the northeastern part of the 94 acre IRMW property as shown on Figure 1. The 35 acre parcel essentially covers the old Mid -Continent coal loadout site. This 35 acre parcel is currently being used for a variety of industrial and commercial purposes. The proposed transfer station and recycling facilities will be limited to only a small part of the 35 acre project site. Waste transfer and recycling will occur in the existing main loadout building, see Figure 6. This building is a 500 -foot long, multistory, corrugated metal structure with reinforced concrete foundation walls. Only minor upgrades to the existing building are proposed. Waste arriving at the site will be presorted as part of the exiting curbside recycling program and no sorting of waste will occur on-site. Non -recyclable waste will be compacted and trucked to existing off-site landfills. Recyclables will be placed in containers for transport and sale. Fluid generated in the transfer and recycling process will be collected and stored in containment tanks. The collected fluids will then be disposed of in existing off-site landfIls. The facility will only operate during normal work day hours. At the end of the work day trash trucks will be parked overnight at the project site. Parking areas and on-site truck circulating roads will be paved or graveled. It is our understanding that little additional grading will be needed to build the proposed waste transfer and recycling facility. When grading plans for the on-site improvements are available, we should review the plans and perform additional geotechnical evaluations as needed for the design. PROJECT SITE CONDITIONS The project site covers about 35 acres in the northeastern part of the 94 acre IRMW property as shown on Figure 1. The 35 acre project site is essentially the old Mid - Continent coal loadout facility and several buildings associated with the old loadout are still present at the project site, see Figures 2 and 6. The 35 acre project site is currently being used for a variety of industrial purposes. The topography at the 35 acre project site and vicinity is shown by the contour lines on Figures 1 and 6. The 35 acre project site lies at the base of a prominent, 540 -foot high, west -trending escarpment. This escarpment Job No. 112 021A Ge Ptech -3 - forms the south Roaring Fork River valley side to the east of Carbondale. The escarpment has an average slope of about 70 percent and abruptly transitions to the nearly level river valley floor in the vicinity of the 35 acre project site. A strongly rolling upland with slopes between 10 and 15 percent lies to the south of the escarpment. Before construction of the Mid -Continent coal loadout the transition slope between the very steep escarpment and the river valley floor consisted of small, coalescing fans that formed a continuous depositional apron at the base of the escarpment. This apron had an average slope of around 25 percent down to the north towards the river valley floor. The original fan surfaces have been considerably modified by grading for the old Mid -Continent coal loadout. The drainage basins upslope of the small coalescing fans are typically less than 2 acres but the largest is about 6 acres. The streams in these basins are ephemeral and only have surface flow following heavy rainfall or snowpack melt. Runoff from the escarpment is currently diverted around most of the 35 acre project site in a shallow diversion ditch which in places is only about three feet deep. The fans that developed at the mouths of these ephemeral streams indicate that these small basins in the past have produced debris flows and floods (hyperconcentrated flows). At the time of this study the property was primarily an equipment storage site with some other industrial uses. A mini -storage facility is located on the adjacent property to the east, see Figure 2. Ranches and rural residential development is present on the river terrace to the north. The rolling upland to the south of the escarpment is undeveloped range land. Vegetation on the escarpment is an open juniper and pinyon forest with brush and grass understory. It appears that the forest on the escarpment directly to the south of the main loadout building has burned, see Figure 2. REGIONAL GEOLOGIC SETTING The regional geology in the project area is shown on Figure 3. The 35 acre project site is located on a structural platform with complex geology that lies between the White River Uplift to the north, the Piceance basin to the west and the Sawatch Range uplift to the east. These are first order geologic structures that developed during the Laramide orogeny about 40 to 72 million years ago. The project site is in the western Colorado evaporite region in the southern part of the Carbondale collapse center, see Figure 4. The Job No. 112 021A CUP'tech -4 - Carbondale collapse center and the Eagle collapse center to the east began to develop about 30 million years after the Laramide orogeny but the evaporite rocks (map unit Pze on Figure 3) in the western Colorado evaporite region were deposited much earlier than the Laramide orogeny. These evaporites were deposited in the northwest -trending central Colorado trough during the ancestral Rocky Mountain orogeny, about 280 to 320 million years ago. CARBONDALE EVAPORITE COLLAPSE CENTER The Carbondale evaporite collapse center is the western of two regional evaporite collapse centers present in western Colorado, see Figure 4. The Carbondale center covers about 460 square miles and as much as 4,000 feet of regional ground subsidence is believed to have occurred during the past 10 million years in the vicinity of Carbondale as a result of dissolution and flowage of evaporite from beneath the region (Kirkham and Others, 2002). Much of this subsidence appears to have occurred within the past 3 million years which also corresponds to high incision rates along the Colorado River and its principle tributaries that include the Roaring Fork and Crystal Rivers (Kunk and Others, 2002). It is uncertain if the regional subsidence is still an active geomorphic process or if evaporite subsidence has stopped. If still active, present deformations may be occurring at rates similar to past long-term rates of between 0.5 and 1.6 inches per 100 years. These slow deformation rates should not present a potential risk to the proposed waste transfer and recycling processing facilities. GEOLOGICALLY YOUNG FAULTS Geologically young faults related to evaporite tectonics are present in the Carbondale collapse center in the vicinity ofthe 35 acre project site but considering the nature of evaporite tectonics, these faults are not considered capable of generating large earthquakes. The closest geologically young faults that are less than about 15,000 years old, not related to evaporite tectonics and considered capable of generating large earthquakes, are located in the Rio Grande rift to the east of the project site, see Figure 5. The northern section ofthe Williams Fork Mountains fault zone Q50 is located about 61 Job No. I 12 021A Ge litech -5 - miles to the northeast and the southern section of the Sawatch fault zone Q56b is located about 61 miles to the southeast. At these distances, large earthquakes at the maximum probable level of around M6.5 on the two closest geologically young fault zones should not produce strong ground shaking at the project site that is greater than the ground shaking shown on the U. S. Geological Survey 2002 National Seismic Hazards Maps (Frankel and Others, 2002). PROJECT AREA GEOLOGY The main geologic features in the project area are shown on Figure 6. The project area geology map is based on our field observations, aerial photograph interpretations and our previous nearby work. The map is a modification of the regional geology map by Kirkham and Widmann (1997). Geologic map units shown on Figure 6 are discussed below. EAGLE VALLEY EVAPORITE (Qc/Pee and Pee) Formation rock below the surficial soil deposits in the project area is the middle Pennsylvanian -age, Eagle Valley Evaporite (map units Qc/Pee and Pee). It was deposited in the northwest -trending central Colorado trough during the ancestral Rocky Mountain orogeny, about 280 to 320 million years ago. The Eagle Valley Evaporite is usually covered by a thin colluvium (map unit Qc/Pee) but prominent outcrops (map unit Pee) are locally present on the escarpment. Outcrops that are potential start zones for rockfalls that have the potential to reach the 35 acre project site are labeled OC -1 through OC -4 on Figure 6. The Eagle Valley Evaporite is a sequence of evaporitic rocks consisting of massive to laminated gypsum, anhydrite and halite with interbeds of light colored mudstone, fine-grained sandstone, shale, limestone and dolomite (Kirkham and Widmann, 1997). The prominent outcrops that are potential rockfall start zones are cemented mudstone and limestone. An oil exploration well near Catherine Store about one and one-half miles to the northeast of the 35 acre project site shows that the Eagle Valley Evaporite is at least 2,700 feet thick at the well location (Kirkham and Widmann, 1997). The bedding in the Eagle Valley Evaporite is usually intensely folded and ductile Job No. 112 021A G Pfech -6 - deformed by past flowage, load metamorphism and anhydrite hydration. The evaporite minerals in the formation can locally be soluble in circulating groundwater and shallow subsurface, solution voids that can develop into surface sinkholes are locally present where the Eagle Valley Evaporite is near the surface in the western Colorado Evaporite region, see Figure 4. Evidence of sinkholes were not observed in the field or on the aerial photographs of the project area but sinkholes are locally present elsewhere in the Roaring Fork River valley between Basalt and Glenwood Springs. SEDIMENTS OF SOPRIS BOWL (Qc/Tsb) Sediments of Sopris Bowl below thin colluvium (map unit Qc/Tsb) are present near the top of the steep escarpment and upland to the south. These sediments may have a maximum preserved thickness of around 3,600 feet (based on seismic reflection data) and were deposited some time after the eruption of a volcanic tuff dated to be 35.21 ± 0.03 million years old (Kirkham and Others, 2002). A regional group of basalt flows that have been dated to be around 13.3 million years old occurs near the top of the sediments (Kirkham and Others, 2002). This indicates that most of the sediments in Sopris Bowl were deposited before the start of regional subsidence of the Carbondale collapse center about 10 million years ago. The sediments are gravelly and cobbly, clast-supported fluvial deposits and matrix -supported debris flow deposits. Clast litholologies indicate a Crystal River origin for the sediments in the western part of the bowl and a Roaring Fork River origin for the sediment in the eastern part of the bowl (Kirkham and Others, 2002). LANDFORMS AND SURFICIAL SOIL DEPOSITS The steep, 540 -foot high escarpment and the surficial soil deposits and related landforms in the project area are largely associated with cyclic erosion and deposition most likely related to glacial and interglacial climatic fluctuations during the Quaternary. The upland bench to the south of the steep escarpment is a relic landform that is older than the 620 thousand year old Lava Creek B volcanic ash (Kirkham and Widmann, 1997). The steep escarpment developed as a result of Roaring Fork River down cutting below the upland surface that started several hundreds of thousands of years ago and has continued to the Job No. 112 021A GecPtech -7 - present. The fans at the base of the escarpment likely formed during and after the last glaciation in the Rocky Mountains. The youngest landscape features in the project area are man -disturbed ground. Surficial soils and related landform map units are discussed below. Man -Disturbed Ground (af): Man -disturbed ground (map symbol af) is common in the project area and has modified the natural landscape. The disturbed ground is associated with grading for the old Mid -Continent coal loadout facility, grading along County Road 100 and grading for the mini storage buildings adjacent to the 35 acre project site to the east. As shown on Figure 6 the grading has considerably modified the younger fans (map unit Qfl). The only remnants of these fans are the fan heads in the central part of the 35 acre project site and the distal parts of the fans to the north of the county road. Grading for the old Mid -Continent loadout consists of several nearly level cut and fill benches with interbench slopes typically about 1.5:1 (horizontal to vertical). Interbench slope heights are typically between 10 and 30 feet. The highest interbench slope is located to the south of the existing main loadout building. This slope is about 50 feet high with an average slope between 1:1 and 2:1 (horizontal to vertical). Interbench slopes that are flatter than about 1.5:1 (horizontal to vertical) have mostly performed satisfactorily but steeper interbench slopes have undergone considerable post -construction raveling. This raveling will continue unless the raveling slopes are flattened or stabilized by other means. Youngest River Terrace (Qtl): The Roaring Fork River valley floor to the north of the 35 acre project site is the youngest fluvial terrace along the river (map unit Qtl). The surface of this terrace lies less than 12 feet above the modern river channel (Kirkham and Widmann, 1997). Pedogenic soil profiles that developed at the surface of this terrace are typically A/Ck and A/Cg profiles (National Resources Conservation Service, 2008). The youngest river terrace probably developed during post -glacial time and the near surface fluvial deposits are likely between about 5,000 to 9,600 years old. The fluvial deposits below the youngest river terrace are very rocky loamy sands and very rocky sands using the National Resources Conservation Service soil textural classification system. The Job No. 112 021A GcPtech -8 - rocks are well rounded to subangular and range from gravel- to boulder -size (Kirkham and Widmann, 1997). The fluvial deposits are clast-supported and stratified. Older Fans (Qf2): In places, remnants of older fans (map unit Qf2) are present along the escarpment/river valley floor transition. Low, 10- to 20 -foot high, escarpments separates the older fans from the surface of the youngest river terrace (map unit Qt1). This indicates that the older fans are older than the youngest river terrace. The fans probably developed during the late Pleistocene -age, Pinedale glaciation and the fans are likely greater than about 9,600 years old. Pedogenic soil profiles developed at the surface of the older fans are A/Bw/Bk profiles (National Resources Conservation Service, 2008). Our previous experience on the development just to the east of the 35 acre project site shows that the older fan deposits are rocky silt loams using the National Resources Conservation Service soil textural classification. The rocks are well rounded to angular and range from gravel- to boulder -size. The rounded rocks come from the sediments of Sopris Bowl (map unit Qc/Tsb) that are present near the top of the steep escarpment. The rocks are supported by the silt loam soil matrix. The older fans are largely the product of sediments deposited by infrequent debris flows and debris floods (hyperconcentrated flows). The older fans are no longer the sites of hyperconcentrated flow deposition. Younger Fans (Qf): Over twenty, small coalescing fans (map unit Qfl) that once formed a continuous deposition apron along the escarpment/river valley floor transition slope are present in the project area. The drainage basins tributary to the younger fans are very steep and small. The basin slopes are greater than 30 percent and the basin areas are typically less than 2 acres but the largest is about 6 acres. The younger fans grade smoothly to the youngest river terrace surface (map unit Qtl): Our previous experience with the development just to the east of the 35 acre project site shows that in the subsurface the younger fans overlie the youngest river terrace deposits. These two geologic relationships indicate that the younger fans are younger than the youngest river terrace deposits. The younger fans likely formed during the past 5,000 years following the post -glacial climatic optimum about 5,000 to 7,000 years ago. They may be associated with the three neoglacial cycles that occurred in the Colorado Rocky Job No. 112 021A Gtech -9 - Mountains during the past 5,000 years (Benedict, 1973). Like the older fans, the younger fans are also largely the product of sediments deposited by infrequent debris flows and debris floods (hyperconcentrated flows). The younger fans appear to still be active geomorphic features and areas within the 35 acre project site to the north of the younger fan heads should be considered potential sites of future hyperconcentrated flow deposition. The statistical recurrence probabilities and risks associated with future hyperconcentrated flow on the younger fans are discussed in the Geologic Site Assessment/Hyperconcentrated Flows section of this report. Cut slope exposures and our previous experience on the development just to the east of the 35 acre project site shows that the younger fan deposits are similar to the older fan deposits. The younger fan deposits are rocky silt loams using the National Resources Conservation Service soil textural classification. The rocks are well rounded to angular and range from gravel- to boulder -size. The rounded rocks come from the sediments of Sopris Bowl (map unit Qc/Tsb) that are present near the top ofthe steep escarpment. The rocks are supported by the silt loam soil matrix. Colluvium (Qc): Thin colluvium (map unit Qc) covers the Eagle Valley Evaporite (map unit Pee) and the sediments of Sopris Bowl (map unit Tsb) on the steep escarpment and upland to the south of the 35 acre project site. The colluvium appears to be similar to the younger and older fan deposits and is probably also a rocky silt loam using the National Resources Conservation Service soil textural classification. The rocks should be well rounded to angular and range from gravel- to boulder -size. The rounded rocks come from the sediments of Sopris Bowl (map unit Tsb) that are present near the top of the steep escarpment. The rocks are probably supported by the silt loam soil matrix. GEOLOGIC SITE ASSESSMENT This study shows that geologic conditions that could present an unusually high risk to the proposed waste transfer and recycling facility are not present at the locations ofthe proposed project components. The proposed project components evaluated by this study are the existing main loadout building, overnight truck parking and on-site truck Job No. 112 02IA Gtech -10 - circulation roads. Although the potential risks are not unusually high, the proposed facilities are exposed to some geologic risks related to hyperconcentrated flows, rockfalls, sinkholes and earthquake strong ground shaking. These geologic conditions, an assessment of their potential risks and the need for risk mitigation are discussed below. POTENTIAL HYPERCONCENTRATED FLOWS The younger fans (map unit Qfl) appear to still be active geomorphic features and areas within the 35 acre project site to the north of the younger fan heads should be considered potential sites of future debris flow and flood (hyperconcentrated flow) deposition triggered by extreme thunderstorms over the drainage basins. Historic thunderstorm triggered hyperconcentrated flows have occurred on similar fans in the lower Roaring Fork River valley but historic flows have probably not occurred at the 35 acre project site. Without long term observation or detailed fan specific stratigraphic studies it is not possible to evaluate the statistical recurrence probability of major hyperconcentrated flows at the 35 acre project site with a high level of confidence. In our opinion, the statistical recurrence probability of major hyperconcentrated flows at the 35 acre project site is likely long and may be around100 years and probably longer. A major hyperconcentrated flow event has the potential to damage the existing main ioadout building and deposition of mud and debris should be expected in the truck parking areas and on-site truck circulation roads. There appears to only be a small risk of harm to facility personnel. If these risks are not acceptable to the owner or governmental regulatory agencies then addition studies should be performed to further evaluate hyperconcentrated flow risk and mitigation. Risk mitigation would likely be direct protection ofthe exiting main loadout building by wall reinforcement. Considering the probable low risk, the cost of mitigation could be greater than the cost of building repair and the cleanup of mud and debris if a major hyperconcentrated flow event occurred during the service life of the facility. POTENTIAL ROCKFALL Prominent outcrops ofthe Eagle Valley Evaporite (map unit Pee) are present on the escarpment to the south of the 35 acre project site and some of these outcrops are Job No. 112021A Ge Gtech potential start areas for future rockfalls that could reach the 35 acre project site. These potential rockfall start zones are labeled OC -1 through OC -4 on Figure 6. Rockfall blocks were observed in the field down slope of OC -2 and OC -3 but snow cover may have obscured other rockfall blocks down slope of OC -1 and OC -4. Rockfall blocks could also have been removed during grading for the old Mid -Continent coal Ioadout facilities. The largest rockfall block observed in the field had dimensions of 6 -feet, by 4 - feet, by 3 -feet and an estimated weight of around six tons. One rockfall block stopped in the diversion ditch which indicates that rockfall has occurred since the coal loadout was constructed. Without long term observation it is not possible to evaluate the statistical recurrence probability of rockfalls at the 35 acre project site. It is possible that future rockfalls could reach the existing main loadout building, truck parking area and on-site truck circulation roads. Future rockfalls have the potential to damage the existing Ioadout building and trucks parked on-site. There is also some risk of harm to on-site personnel but this risk should be low and likely not greater than the risk to the traveling public on Colorado highways in infrequent rockfall areas. If these risks are not acceptable to the owner and governmental regulatory agencies then addition studies should be performed to further evaluate rockfall risk and mitigation. Risk mitigation would likely be a rockfall catching fence located up slope of the facilities requiring protection. SINKHOLES The evaporite mineral in the Eagle Valley Evaporite can locally be soluble in circulating ground water and solution of these minerals can result in local subsurface voids which can sometimes develop into surface sinkholes. Shallow subsurface solution voids and sinkholes are locally present in areas where the evaporite lies at a shallow depth throughout the western Colorado evaporite region, see Figure 4. The general character of evaporite sinkholes and the potential risk that sinkholes pose to the proposed waste transfer and recycling facilities are discussed below. General Character of Evaporite Sinkholes: Evaporite sinkholes in western Colorado are typically a 10- to 50 -foot diameter, circular depression at the ground surface. The sinkholes mostly result from upward caving of a soil rubble pipe to the ground surface. Job No. 112 021A G Piech - 12 - The soil rubble pipe is formed by piping and subsurface erosion of surficial soils into subsurface solution voids in the underlying evaporite. Direct caving of very large solution caves have also occurred in the region. New sinkholes can develop at the ground surface with little or no advanced warnings and existing sinkholes can be reactivated. New sinkholes and reactivated sinkholes have the potential for severe damage to buildings and other man-made facilities. Historic sinkholes have developed in the western Colorado evaporite region but have rarely damaged structures. This indicates that sinkhole development is still an active geomorphic process in the region but does not statistically present an unusually high risk to structures in the region as a whole. Potential Sinkhole Risk: Evidence of sinkholes was not observed in the field or on the aerial photographs of the 35 acre project site. In our opinion, the risk that a sinkhole will develop at the existing main Ioadout building, at the overnight truck parking and at the on-site truck circulation roads is low during a reasonable exposure time for these facilities. The sinkhole risk at the proposed waste transfer and recycling facility does not appear greater than the existing risk elsewhere in the lower Roaring Fork River valley or in western Colorado evaporite region with shallow evaporite as shown on Figure 4. The low risk in the region is inferred from the large extent of the sinkhole prone areas in comparison to the small number of new sinkholes that have developed during historic times in the region. The waste transfer and recycling facility owner should be aware of the low sinkhole risk and that the proposed facilities cannot be considered totally risk free. If evidence of a developing sinkhole is noted it may be possible to limit potential facility damage with ground improvement techniques such as structural backfill and compaction grouting. EARTHQUAKE CONSIDERATIONS Historic earthquakes within 150 miles of the 35 acre project site have typically been moderately strong with magnitudes of M 5.5 and less and maximum Modified Mercalli Intensities of VI and less, see Figure 5. The largest historic earthquake in the project region occurred in 1882 (Kirkham and Rogers, 1985). This earthquake was apparently Located in the northern Front Range about 117 miles to the northeast of the 35 project site Job No. 112 021A G d tech - 13 - and had an estimated magnitude of M 6.2 ± 0.3 and a maximum intensity of VII. Historic ground shaking at the 35 acre project site associated with the 1882 and the other larger historic earthquakes in the region does not appear to have exceeded Modified Mercalli Intensity VI (Kirkham and Rogers, 1985). Modified Mercalli Intensity VI ground shaking should be expected during a reasonable exposure time for the proposed project facilities, but the probability of stronger ground shaking is low. Intensity VI ground shaking is felt by most people and causes general alarm, but results in negligible damage to structures of good design and construction. We do not anticipate earthquake ground shaking problems with the existing main loadout building if the building was designed to withstand moderately strong ground shaking with little or no damage and not to collapse under stronger ground shaking. The U. S. Geological Survey 2002 National Seismic Hazard Maps indicate a peak ground acceleration of 0.06g has a 10% exceedence probability for a 50 year exposure time and a peak ground acceleration of 0.23g has a 2% exceedence probability for a 50 year exposure time at the 35 acre project site (Frankel and Others, 2002). This corresponds to a statistical recurrence time of about 500 years and 2,500 years, respectively. These accelerations are forfarm rock sites with shear wave velocities of 2,500 fps and higher in the upper 100 feet and should be modified for soil profile amplification at the 35 acre project site. The seismic soil profile at the existing main loadout building should be considered as Class D, stiff soil sites as described in the 2009 International Building Code unless site specific shear wave velocity studies show otherwise. LIMITATIONS This study was conducted according to generally accepted engineering geology principles and practices in this area, at this time. We make no warranty either express or implied. The information presented in this report is based on our field observations, aerial photograph interpretations, the proposed facilities described in this report, our previous experience on the adjacent parcel, and our experience in the area. This report has been prepared exclusively for our client. It is an assessment of potential geologic hazards and constraints to the proposed waste transfer and recycling facility. Facilities evaluated by Job No. 112 021A Gtech -14 - this study are limited to: (1) the existing main loadout building, (2) overnight truck parking and (3) on-site truck circulation roads. An assessment of potential geologic risks to other existing facilities or to future yet undetermined facilities on the 35 acre project site is not within the scope of this study. Also, possible geotechnical engineering considerations related to the proposed waste transfer and recycling facilities is not within the scope of this study. Additional evaluations will be needed if hyperconcentrated flow and rockfall mitigations are considered. We are not responsible for technical interpretations by others of our information presented in this report. Respectfully Submitted, HEPWORTH - PAWLAK GEOTECHNICAL, INC. Ralph G. Mock Engineering Geologist Reviewed by: Steven L. Pawlak, P. RGM/ksw r• #; 16222 ,S J>'+••/ONAt 0/4.••q ale Ebbe cc: Schmueser Gordon ' ` n: David Kotz, PE (davek rr,sgm-inc.com) Job No. 112 021A G Gtech -15 - REFERENCES Frankel, A. D. and Others, 2002, Documentation for the 2002 Update of the National Seismic Hazard Maps: U. S. Geological Survey Open File Report 02-420. Kirkham R. M. and Others, 2002, Evaporite Tectonism in the Lower Roaring Fork River Valley, West -Central Colorado, in Kirkham R. M., Scott, R. B. and Judkins, T. W. eds., Late Cenozoic Evaporite Tectonism and Volcanism in West -Central Colorado: Geological Society of America Special Paper 366, Boulder, Colorado. Kirkham, R. M. and Rogers, W. P., 1985, Colorado Earthquake Data and Interpretations 1867 to 1985: Colorado Geological Survey Bulletin 46. Kirkham, R. M. and Scott, R. B., 2002, Introduction to Late Cenozoic Evaporite Tectonism and Volcanism in West -Central, Colorado, in Kirkham R. M., Scott, R. B. and Judkins, T. W. eds., Late Cenozoic Evaporite Tectonism and Volcanism in West -Central Colorado: Geological Society of America Special Paper 366, Boulder, Colorado. Kirkham, R. M. and Widmann, B. L., 1997, Geology Map of the Carbondale Quadrangle, Garfield County, Colorado: Colorado Geological Survey Open File 97-3. Kunk, M. J., and Others, 2002, 40Ar139Ar Ages of Late Cenozoic Volcanic Rocks within and Around the Carbondale and Eagle Collapse Centers, Colorado: Constraints on the Timing of Evaporite-Related Collapse and Incision of the Colorado River, in Kirkham R. M., Scott, R. B. and Judkins, T. W. eds., Late Cenozoic Evaporite Tectonism and Volcanism in West -Central Colorado: Geological Society of America Special Paper 366, Boulder, Colorado. National Resources Conservation Service, 2008, Soil Survey of Aspen -Gypsum Area, Colorado: Version 5, June 9, 2008. Tweto, O., 1979, Geology Map of Colorado: U. S. Geological Survey. Tweto, O. and Others, 1978, Geology Map of the Leadville 1° X 2 ° Quadrangle, Northwestern Colorado: U.S. Geological Survey Map I-999. Widmann B. L. and Others, 1998, Preliminary Quaternary Fault and Fold Map and Data Base of Colorado: Colorado Geological Survey Open File Report 98-8. Job No. 112 021A Gtech Explanation: YA IRMW Property (94 ac.) Project Slte IRMW II. Old Mid -Continent Coal Loadout Facility (35 ac.) 0 2000 ft. I I 1 Scale: 1 in. = 2000 ft. Contour Interval = 40 ft_ February 2012 112 021A cec5roecr, HEPWORTHPAWLAK GEOTECHNICAL IRMW Waste Transfer Station and Recycling Processing Facility Project Site Location Figure 1 0 1000 ft. l 1 Scale: 1 in. =1000 ft. February 2012 112 021A Gggtech HE=WORTH -.FAV,L.A.K GEOTECHNICAL IRMW Waste Transfer Station and Recycling Processing Facility Project Area Aerial Photograph Figure 2 Ti Upli iiks Doisero Mz New Castle r-� Mountain ondaieg Project Tv Site T Rued Res. Site Pz Pze - Ti Aspen Snowiness Pluton Sro'irnass Range Marocn Pk Explanation: Ts TI TKs TKi Post-Laramide Sediments Post-Laramide Volcanics Post-Laramide Intrusives Laramide Basin Sediments Laramide Intrusives Mz Pze Pre-Laramide Mesozoic Sediments Paleozoic Sediments Pennsylvanian Evaporites Precambrian Crystalline Rocks Contact High -Angle Faults • • Thrust Faults Synclines Anticlines Highways 0 L_ { Scale 1 in. = 7 mi February 2012 Modified from: Tweto (1979) 7 mi. 112 021A G&ech HEFWORTH-FAWL4 IRMW Waste Transfer Station and Recycling Processing Facility Regional Geology Map Figure 3 m G m 0 CD CD 0 0 0 CTI 0 m tutu o0 • J. • LO CD .0 -ti o p ▪ (1) 0) J 0 pue Uogejs 9eisueJ1 aaseM MWHI Explanation: Shallow Evaporite in Eagle Valley Formation and Eagle Valley Evaporile. /Eagle Collapse Center (960 sq. mi.} 10 Miles February 2012 References: Twato and others (1078) Kirkham and Scott (2002) Basin Carbondale Collapse Center (460 sq. mi.) M:tib l�- Aspin eU!pgUV 8 ;Ll p eines Vaal • 1977 M 5.0 5.5 u Middle Rocky intermountain Seismic Belt Moab Rangely Boulder WY. NB. CO. Fad Great coffins Loveland ❑ Greeley Q Rocky Mtn. Arsenal 1962 to 1967 VI la VII M3.2'IoM5.3 • �0 Grand Jun @Sll, L•' @ Delta Stenos 9 3 porion) 5.7 Denver ❑ Parker Fort M 0 0 roKlowa Lir Cask Rock Colorado Sp. ❑ 4 Montrose ❑ Plateau Plains Puebla Watsenburg ❑ n Cortez UT. CO. Trinidad 2011 M 5.3 VII � 'Trinidad —� "'Trin€dad P.3ton Explanation: Post -Glacial Faults: Fault younger than about 15.000 years. Larger Historic Earthquakes: Earthquakes with maximum intensity greater than VI or magnitude greater than M 5.0 from 1867 to present. Nuclear Explosion: Large underground nuclear explosion for natural gas reservoir enhancement. Historic Seismic Zones: Areas with historically high seismic activity. M Local, surface wave or body wave magnitude VI Modified Mercalli intensity References: Widmann and Others (1998) U, S. Geological Survey Earthquake Catalogs 0 50 mi. 1 1 Scale: 1 in. = 50 mi. February 2012 112021A '"GecPtecn HEFWORTH-PAWLAK. GEOTECHNICAL IRMW Waste Transfer Station and Recycling Processing Facility Geologically Young Faults and Larger Historic Earthquakes Figure 5 J N 0 N D _ Qt1 Qt1 Qt1 • Qf1 o v I .•_ _ 1 ` _ .. un 4. 10I} Qt1 Qt1,4 -�� _ Q' Qf1�1, � .1.._ncr N_relb Y Qi Qee��"-�e - - of '. `��. f1 Qf1 w „1- [Pee --�• ee oC QMQf1 Qf1 a' " ;rig 1 oc� _- Qf1 ;; . __ — j1 fir- � �_# z IPe ��1e I . ;. oc-3 Ohir�)f- 1 a IRMW Waste Transfer Station and Recycling Processing Facility Project Area Geology Map IRMW Properly Line �- A `« Qci Tsb .�� �``�, Qc1Tsb - Explanation: Man-Disturbed Ground: Qsb Colluvium over Sediments of Sopris Bow of Cut and fill areas related to the old Mid-Continent coal loadout facility and adjacent development. Qc/Pee Colluvium over Eagle Valley Evaporite Younger Fans Pee Eagle Valley Evaporite: Qf1 Prominent outcrops of Eagle Valley Evaporite. Fans Labled outcrops (OC-1 through OC-4) have the Q2Older potential for rockfall that could reach the 35 ac. Youngest River Terrace project site. Qt1 Contact: Approximate boundary of map units. 0 1 1 650 ft. 1 Scale: 1 in. = 650 ft. Contour Interval: 20 ft. February 2012 Modified from Kirkham and Widmann (1997) Figure 6