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HomeMy WebLinkAbout4-203.G.4 Geohazards RptArticle 4-203.G.4 Geologic and Soils Hazard Report Encana Oil & Gas (USA) Inc K19NE Storage Facility (Laydown Yard) OAProject No. 014-2797 NATURAL AND GEOLOGIC HAZARDS ASSESSMENT REPORT ENCANA OIL & GAS (USA) INC. K19NE STORAGE YARD NE 1/4 SW 1/4 (Lor 3) SECTION 19, T6S, R92W, 6TH P.M. GARFIELD COUNTY, COLORADO PREPARED FOR ENCANA OIL & GAS (USA) INC. 143 DIAMOND AVENUE PARACHUTE, COLORADO 81635 PREPARED BY OLSSON ASSOCIATES 4690 TABLE MOUNTAIN DRIVE, SUITE 200 GOLDEN, COLORADO 80403 FEBRUARY 2015 PROJECT No. 014-2797 CAOLSSON ASSOCIATES Natural and Geologic Hazard Report Preface Garfield County, Colorado, finalized the Land Use and Development Code (LUDC) with an effective date of July 15, 2013, last amended December 16, 2013. According to Section 7-108 Use of Land Subject to Natural Hazards of the Garfield County LUDC "Land subject to identified Natural and Geologic Hazards, such as falling rock, landslides, snow slides, mud flows, radiation, flooding, or high water tables, shall not be developed unless it has been designed to eliminate or mitigate the potential effects of hazardous site conditions as designed by a qualified professional engineer and as approved by the County." The LUDC requires a Natural and Geologic Hazard Study be prepared by a qualified professional geologist and submitted with a development plan or plat. The LUDC defines a geologic hazard as "A geologic phenomenon that is so adverse to past, current, or foreseeable construction or land use as to constitute a significant hazard to public health and safety or to property. The LUDC defines a Hazard Area as "An area that contains oris directly affected by a geologic hazard, including but not limited to the following types of areas." A. Avalanche Area. "A mass of snow or ice and other material that may become incorporated therein as such mass moves rapidly down a slope." B. Landslide Area. "An area with demonstrably active mass movement of rock and soil where there is a distinct surface rupture or zone of weakness that separates the landslide material from more stable underlying material." C. Mudflow Debris Area. "An area subject to rapid mud and debris movement or deposit occurring after mobilization by heavy rainfall or snowmelt runoff. Such areas are formed by successive episodes of deposition of mud and debris." D. Radioactive Area. "An area subject to various types of radiation emission from radioactive minerals that occur in natural or manmade deposits of rock, soil, or water." E. Potentially Unstable Soils. "An area of land identified as having soils that may cause damage to structures, such as buildings and roadways, as a result of over saturation or some other outside influence." According to the Garfield County LUDC Section 4-203 Description of Submittal Requirements, the professional qualifications for preparation and certification of certain documents required by this Code are as follows: "Geologist: Geology reports shall be prepared by either a member of the American Institute of Professional Geologists, a member of the Association of Engineering Geologists, or a qualified geotechnical engineer licensed in the State of Colorado." Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado Olsson Associates Golden, Colorado February 2015 Currently, the State of Colorado does not require licensure or registration of geologists; however, Colorado Revised Statutes do require that geologic reports be prepared or authorized by a professional geologist, and the term "Professional Geologist" is defined in Colorado Statutes. The references for these Statutes are shown here: 34-1-201. Definitions. As used in this part 2, unless the context otherwise requires: (1) "Geologist" means a person engaged in the practice of geology. (2) "Geology" means the science which treats of the earth in general; the earth's processes and its history; investigation of the earth's crust and the rocks and other materials which compose it; and the applied science of utilizing knowledge of the earth's history, processes, constituent rocks, minerals, liquids, gases, and other materials for the use of mankind. (3) "Professional geologist" is a person who is a graduate of an institution of higher education which is accredited by a regional or national accrediting agency, with a minimum of thirty semester hours (forty-five quarter) hours of undergraduate or graduate work in a field of geology and whose post baccalaureate training has been in the field of geology with a specific record of an additional five years of geological experience to include no more than two years of graduate work. (4) 34-1-202. Reports containing geologic information. Any report required by law or by rule and regulation, and prepared as a result of or based on a geologic study or on geologic data, or which contains information relating to geology, as defined in Section 34-1-201 (2), and which is to be presented for any state agency, political subdivision of the state, or recognized state or local board or commission, shall be prepared or approved by a professional geologist as defined in Section 34-1-201(3). Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado ii Olsson Associates Golden, Colorado February 2015 Professional Geologist Certification By means of this certification, I attest that: - I am qualified to prepare a Natural and Geologic Hazard Study in accordance with the provisions of Section 7-207 of the Garfield County LUDC, and that I am a member of the American Institute of Professional Geologists per LUDC 4-203. - Although I have not visited the proposed Site, I am familiar with the geology and have performed field work in the area of the proposed Encana Oil & Gas (USA) Inc. Storage Yard located in the NE'/ SW'/, (Lot 3) Section 19 Township 6 South, Range 92 West, 6th Principal Meridian in Garfield County, Colorado. Although Colorado does not currently have a licensing board or registration program for professional geologists practicing in the state of Colorado, there are requirements within local and State statutes that require that geologic reports be prepared by a professional geologist. I attest that I meet the requirements of the Colorado Geological Survey's definition of a professional geologist having completed and met the educational requirements of the Colorado Geological Survey definition. I am a licensed Professional Geologist and Professional Geoscientist in other States, including Texas, Utah, and Wyoming which do have licensing programs for professional geologists. I have reviewed published geologic maps and reports applicable to this area and have considered the implications of these conditions in the context of the proposed development. This report has been prepared in accordance with good scientific principles and engineering practices including consideration of applicable industry standards, and with consideration of the requirements of the National Association of State Boards of Geology. The conclusions and recommendations contained in this report are based on information available and known to me at the time of this report. Good scientific principles and standard engineering practices were taken into consider -__a= ���� arriving at the conclusions and recommendations made in this repo „4k Reviewed 7J3O5 iia. �AIP�! SA Prepared by .44/ted— 40, /914x James W. Hix, PG Senior Geologist Date: 02/02/2015 Kevin J. Ta,'`` �; F� ; Cr_ Senior Geologis Date: 02/02/2015 Note: The PG's certification does not relieve the owner/operator of the facility of the duty to review this report or fully implementing the recommendations in accordance with all applicable Federal, State, and local requirements in order to achieve the desired goals or objectives. Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado Olsson Associates Golden, Colorado February 2015 TABLE OF CONTENTS Natural and Geologic Hazard Report Preface i Professional Geologist Certification iii TABLE OF CONTENTS iv FIGURES iv 1.0 EXECUTIVE SUMMARY 1 2.0 GENERAL SITE LOCATION AND BACKGROUND 3 2.1 Project and Site Description 3 2.2 Structural Geology 3 2.3 Site Geology 4 2.4 Soil 4 2.5 Hydrologic Setting 4 2.6 Aquifers 5 2.7 Permitted Water Wells 5 3.0 NATURAL AND GEOLOGIC HAZARD ASSESSMENT 6 3.1 Utilities 6 3.2 Avalanche Hazard Area 6 3.3 Landslide Areas or Potential Landslide Hazard Areas 6 3.4 Rockfall Areas 7 3.5 Alluvial Fan Hazard Areas 7 3.6 Unstable or Potentially Unstable Slopes 7 3.7 Corrosive or Expansive Soils and Rock 7 3.8 Mudflow and Debris Fan Areas 7 3.9 Development Over Faults and Risk of Seismic Activity 7 3.10 Flood Prone Areas 8 3.11 Collapsible Soils 8 3.12 Mining Activity 8 3.13 Radioactivity 8 4.0 CONCLUSIONS AND RECOMMENDATIONS 10 5.0 REFERENCES 11 FIGURES List of Figures V-1 Vicinity Map T-1 Topographic Map G-1 Geology Map S-1 Soils Map F-1 Floodplain Map Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado iv Olsson Associates Golden, Colorado February 2015 1.0 EXECUTIVE SUMMARY Olsson Associates (Olsson) was contracted by Encana Oil & Gas (USA) Inc. (Encana) to assess natural and geologic hazards potentially present in the area of the proposed Storage Yard (Site) located in the Lot 3 of Section 19, Township 6 South, Range 92 West, of the 6th Principal Meridian, in Garfield County, Colorado. The Site location is shown on the V-1 Vicinity Map. The Site is at an elevation of about 5,689 feet above mean sea level (amsl) as shown on the attached T-1 Topographic Map. The purpose of this report is to identify geologic conditions that may pose hazards to a land development project in order that appropriate mitigation or avoidance techniques may be implemented as described in the Garfield County LUDC. According to the Garfield County LUDC, Section 7-207, the types of natural and geologic hazards identified pertain to the following: A. Utilities; B. Development in Avalanche Hazard Areas; C. Development in Landslide Hazard Areas; D. Development in Rock -fall Hazard Areas; E. Development in Alluvial Fan Hazard Areas; F. Slope Development; G. Development on Corrosive or Expansive Soils and Rock; H. Development in Mudflow Areas; and I. Development Over Faults. This report presents Olsson findings following an evaluation of these and other geologic hazards potentially affecting the Site and proposed development. The Encana site was found to be suitable for the proposed development with consideration of the following identified geologic hazards. • No utilities are planned for the proposed Site development. • The Site is not in an Avalanche Hazard Area. • The Site is located on a gently sloping parcel of land south of the Mamm Creek drainage and bound to the west by the West Mamm Creek drainage and to the east by unnamed tributary drainages to Mamm Creek. Slopes do not appear to be a hazard affecting the Site since it is in an area of gentle slopes. • The soil beneath the Site is mapped as the Potts Loam (Map Unit # 55). These soils are found on three percent to six percent slopes; however, soil in adjacent areas along Mamm Creek and the tributary drainages are mapped as Rock outcrop —Torriothents complex and are found on steep slopes ranging from 12 percent to 25 percent to the west, and steep slopes to the north. • The Site is not located in an area of rock -fall or landslide hazards. • According to the Colorado Oil and Gas Conservation Commission (COGCC) GIS online map, the bedrock geology has been mapped (scale of 1:500,000) in the vicinity of the Site as the Tertiary age Wasatch Formation including the Fort Union equivalent at its Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 1 Olsson Associates Golden, Colorado February 2015 base and the Ohio Creek Formation. Quaternary gravels and alluviums of Pinedale and Bull Lake Age are shown to the south in Section 30, Township 6 South, Range 92 West. According to the Geologic Map of the Silt Quadrangle, Garfield County (1:24,000), the Site surficial geology consists of Quaternary age loess deposits overlying older terrace alluvium and bedrock consisting of the Eocene Shire Member of the Tertiary Wasatch Formation. • According to the Geologic Map of the Leadville Quadrangle, alluvial fan gravels are mapped on Grass Mesa to the west, but the site is not in an area mapped as having alluvial fan deposits; therefore, the site is not in an alluvial fan hazard area. • According to the Geologic Map of the Leadville 1° x 2° Quadrangle, Colorado (scale 1:250,000), and the Geologic Map of the Silt Quadrangle, there are no mapped faults in the area of the Site. The axis of the Rifle Syncline lies to the north of the Site subparallel to the Colorado River drainage. • The Eocene Shire Member bedrock dip angles in the vicinity of the Site have been measured and range from seven degrees to ten degrees to the west and northwest as plotted on the Geologic Map of the Silt Quadrangle. This compares to dip angles of nearly 90 degrees along the Grand Hogback north of the town of Rifle and areas where the bedrock strata is overturned. This is evidence of thrust faulting in the region. • The Silt topographic quadrangle map and the Geologic Map of the Silt Quadrangle do not show any mining operations in the immediate vicinity of the site. There are sand and gravel quarries located along the Colorado River drainage to the north. Natural gas wells and production facilities are present in the vicinity of the Site and surrounding areas. • The Site is not mapped within the FEMA 100-year flood plain. The Site is located at an elevation of approximately 5,689 feet approximately two miles south of the Colorado River which is at an elevation of approximately 5,368 feet above mean sea level (amsl). The bottom of the drainage to the west of the Site is at an elevation of approximately 5,581 feet amsl. These drainages and the Colorado River may experience flash floods, but the K19NE Site is located above the expected flood stage. There do not appear to be any significant natural or geologic hazards associated with the Site proposed for the Encana Site. This report should be read in its entirety, including but not limited to the conclusions and recommendations in Section 4.0. Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 2 Olsson Associates Golden, Colorado February 2015 2.0 GENERAL SITE LOCATION AND BACKGROUND Encana contracted Olsson Associates (Olsson) to conduct a natural and geologic hazards assessment as part of the proposed development of the K19NE storage yard (Site). The proposed facility will be used to store surplus equipment and materials used in the drilling and production of natural gas wells in the area. The following sections provide information about the proposed development and the Site geologic setting. 2.1 Project and Site Description The proposed Site is located southeast of the town of Rifle, Colorado off of Garfield County Road 333 south of the Garfield County Municipal Airport. The Site is located in the Lot 3 of Section 19, T6S, R92W, 6th P.M. (39.50956° N -107.70974°W) and is located on parcel #2179- 193-00-128. The surface land parcel encompasses approximately 88.42 acres and is owned by Encana; however the storage yard occupies approximately 2.7 acres in the south central part of the parcel. 2.2 Structural Geology The Site is located in the southeastern part of the Piceance Basin. The Piceance Basin is an irregularly-shaped elongated basin formed by tectonic forces associated with the Laramide orogeny. These forces down warped the earth's crust and formed the Piceance Basin as a result of the uplift of the surrounding Colorado Rocky Mountains and the Colorado Plateau. The area geology is shown on the G-1 Geologic Map. The Piceance Basin is the major structural geologic feature in the region. It is bound to the east by the Grand Hogback monocline, the White River Uplift to the northeast, the Gunnison Uplift to the south, the Uncompahgre Uplift to the south and southwest, the Douglas Creek Arch to the west-northwest, and the axial basin uplift to the north. Sedimentary rocks in the southwestern Piceance Basin gently dip to the north-northeast except where this regional dip is interrupted by low -amplitude folds. Numerous small sub -parallel northwest trending folds have been identified within the basin. The Divide Creek and Wolf Creek anticlines are two gentle, north-northwest trending, natural gas producing intrabasin folds located near the eastern margin of the Piceance basin. (Grout and Verbeek, 1992). These anticlines are located south-southeast of the Site. The bedrock in the vicinity of the Site dips at angles between seven degrees and ten degrees to the west-northwest. A fault is a fracture in rock along which movement has occurred. Mountains are bound by faults and are a visible indication of a structural weakness in the earth's crust. The Colorado Rocky Mountains are bound by faults; however, these faults are not always visible at the ground surface either because the fault trace is `blind', meaning that the fault does not have surface expression since it does not cut across overlying sedimentary bedrock units, or that it has been buried and concealed by unconsolidated sediments deposited over the area where the faults are present. There are no mapped faults shown in the immediate area of the Site on the Geologic Map of the Leadville 1° x 2° Quadrangle, Garfield County, Colorado (Tweto, Moench, and Reed, 1978) or on the Geologic Map of the Silt Quadrangle, Garfield County, Colorado (Shroba and Scott, Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 3 Olsson Associates Golden, Colorado February 2015 2001) (Scale 1:24,000). However, folds such as the intrabasinal Divide Creek anticline and Wolf Creek anticline, and the Grand Hogback monocline, which defines the eastern margin of the Piceance Basin, have been interpreted as the surface expression of thrust faulting in which a wedge of basement rock was moved west-southwest during the uplift of the Rocky Mountains during the Laramide orogeny. Movement along the thrust fault compressed the overlying sedimentary rock which formed these low amplitude folds and the Grand Hogback (Grout and Verbeek, 1992). 2.3 Site Geology The area geology is shown on the G-1 Geologic Map. According to the Geologic Map of the Silt Quadrangle ((Shroba and Scott, 2001), bedrock mapped in the area of the Site consists of the Eocene Shire Member of the Wasatch Formation which consists of variegated purple, lavender, red, gray, and brown claystone; some locally lenticular, fine- to coarse-grained sandstone and conglomerate, and thin limestone beds. The maximum exposed thickness of the Shire Member is approximately 1,600 feet, and reaches up to 3,900 feet thick in the Silt Quadrangle (Shroba and Scott, 2001). The Shire Member is the upper member of the Wasatch Formation and overlies the Molina Member and Atwell Gulch Member, which in turn lie above the Ohio Creek Formation. The Ohio Creek Formation marks the boundary between the Cretaceous and Tertiary sedimentary rocks in the Piceance Basin (Donnell, 1969). The bedrock at the site is mantled by Quaternary age terrace alluvium and loess deposits. Terrace deposits associated with Pinedale and Bull Lake age are mapped to the south in Section 30 and the SE 1/4 SE 1/4 Section 19, T6S, R92W. 2.4 Soil The Natural Resources Conservation Service (NRCS) S-1 Soils Map shows the area soil types. Soils, consisting of the following units, are within the study area around Site: Potts Loam, Map Symbol 55, is a moderately sloping soil found on mesas, benches, and the sides of valleys at elevations ranging from 5,000 feet to 7,000 feet amsl. The soil formed in alluvium derived from sandstone, shale, or basalt. Typically the surface layer is brown loam about four inches thick, the subsoil is reddish brown clay loam about 24 inches thick, and the substratum is pinkish white loam to a depth of 60 inches thick. Permeability is moderate, and the available water capacity is high. Surface runoff is slow and the erosion hazard is moderate. Community development and recreation are limited by low strength and the shrink -swell potential. Dwellings and roads can be designed to overcome these limitations. 2.5 Hydrologic Setting The Site is located at an elevation of approximately 5,689 feet, bound to the west by the West Fork of Mamm Creek and the main branch of Mamm Creek lies to the north. The surface water hydrology and shallow groundwater contained in the alluvium are controlled by Mamm Creek and its tributary drainages. Surface water flow is to the west — southwest toward the confluence Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 4 Olsson Associates Golden, Colorado February 2015 with the main branch of Mamm Creek. Shallow groundwater is expected to follow topography and flow toward and parallel the flow of the West Fork of Mamm Creek to the north toward the confluence with Mamm Creek and its confluence with the Colorado River approximately two miles north of the Site. These surface water features are shown on the H-1 Hydrography Map. 2.6 Aquifers The Wasatch Formation consists predominantly of very fine-grained claystone and mudstone with lenses of very fine-grained to coarse-grained sandstone and conglomerate. The matrix of these rock types generally exhibits low porosity, relatively low hydraulic conductivity, or the ability to transmit groundwater. Therefore the Wasatch Formation is generally considered a confining unit. Some lenticular sandstones yield water wells in some areas south of the town of Rifle; however, the quantity and quality of this water is variable. The most productive wells are those completed in areas with secondary porosity or interconnected bedrock fractures. Alluvial aquifers consist of unconsolidated sediments deposited along the Colorado River, Mamm Creek, and major tributaries to these streams. The thickness of the unconsolidated sediments must provide for sufficient volume and stream valley size to be capable of yielding groundwater to domestic wells to be of significance for domestic or use for livestock. 2.7 Permitted Water Wells Three groundwater monitoring holes were permitted by Encana in 2007 in anticipation of constructing a centralized E&P waste management facility per COGCC Rule 908 on the property. The E&P waste management facility was never constructed, and it does not appear that the monitoring wells were ever drilled as the last correspondence with the Colorado Division of Water Resources was to request an extension. There are permitted water wells located in the NW 1/4 NW % Section 19, Township 6 South, Range 92 West. Well permit #190496 MH 26571 was drilled in November 1995, and recorded in May 1996 by the Division of Water Resources. The total depth of the well is listed at 203 feet. The driller's log indicates that from the surface to 56 feet below ground surface (bgs) consisted of large river gravels, from 56 feet to 130 feet bgs consisted of hard red sandstone, from 130 feet to 135 feet consisted of fractured gray shale, from 135 feet to 180 feet bgs consisted of hard red sandstone, and from 180 feet to 203 feet bgs consisted of gray shale. Groundwater was reportedly encountered at 130 feet to 135 feet bgs with a yield of approximately one gallon per minute (gpm). Water well permit 26571 MH is a monitoring hole permitted in 1995. The notification for this well was for a second monitoring/observation well drilled since the first hole was drilled to 333 feet in depth, was dry, and was plugged and abandoned per state rules (see 25935 MH) to the Division of Water Resources. A water well was drilled in the NW % NW % of Section 19 in April 1998, and was advanced to 400 feet bgs. Lithologies consisted of sandstone, shale, mudstone to the total depth. Groundwater was reportedly encountered at 285 feet to 292 feet bgs with a yield of 1/2 gpm, and at 360 feet to 367 feet with a yield of 1 to 11/2 gpm. Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 5 Olsson Associates Golden, Colorado February 2015 3.0 NATURAL AND GEOLOGIC HAZARD ASSESSMENT The following sections present the assessment of geologic hazards in the vicinity of the Site. The T-1 Topographic Map shows the location of the Site in relation to the affected parcel and local roads. 3.1 Utilities Trenches for water pipelines, natural gas pipelines, and electrical lines are not expected to be associated with the proposed development of the Site. The slopes and rocky soil may pose technical challenges to the installation of utilities; however, it is expected that these limitations can be overcome with proper design and installation if utilities are installed. Aboveground utility facilities located in Hazard Areas are to be protected by barriers or diversion techniques approved by a qualified professional engineer. The determination to locate utility facilities aboveground will be based upon the recommendation and requirements of the utility service provider and approved by the County. Aboveground utilities, such as transformers and electrical lines, are not expected to be affected by geologic or other natural hazards. 3.2 Avalanche Hazard Area Winters are cold in the mountainous areas of Garfield County, and valleys are colder than the lower parts of adjacent mountains due to cold air drainage. Average seasonal snowfall in Garfield County is 50 inches. The greatest snow depth at any one time during the period of record from 1951 to 1974 was 29 inches recorded at Rifle, Colorado approximately 5 miles to the northwest of the proposed Site. Avalanches are not expected to affect the proposed Site, since it is located at an elevation of approximately 5,689 feet amsl. Areas in eastern Garfield County are at higher elevations, receive more snow pack, and are, therefore, more prone to avalanches in certain years. Avalanches are the most dangerous geologic hazard in Colorado resulting in injuries, loss of life, and about $100,000 in direct property damage, and indirect economic losses in the millions of dollars annually. However, the avalanche prone areas include the Park Range and Flat Tops in northeastern Garfield County, Colorado, to the north of Glenwood Springs. Glenwood Springs, near the east edge of the area, averages about one degree cooler than Rifle and receives about five inches more precipitation per year (Harman and Murray, 1985). 3.3 Landslide Areas or Potential Landslide Hazard Areas The Shire Member has been identified in areas of steeper slopes on the Rifle Quadrangle to the west as being a potential landslide hazard, but these conditions are not present in the vicinity of the Site. According to Map 24 — Surface Geology map, Geologic Hazards Identification Study (Lincoln Devore, 1975-1976), there are landslide areas shown to the southwest of the town of Rifle, but not in areas to the southeast of Rifle or County Road 333 (Garfield County, Surface Geology, 2007). Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 6 Olsson Associates Golden, Colorado February 2015 3.4 Rockfall Areas The Site is located in an area with moderate to gentle slopes ranging from three percent to six percent slopes. The underlying bedrock in the vicinity of the Site dips seven to ten degrees to the west-northwest. Rock fall is not a potential geologic hazard in the vicinity of the Site. Rockfall is a potential geologic hazard in areas along the West Mamm Creek and Mamm Creek drainages to the west and north of the Site. 3.5 Alluvial Fan Hazard Areas The Site is not located in an area that is mapped as being in an alluvial fan hazard area according to the Garfield County Surficial Geology, 2007. The Site is located on loess deposits and older alluvium mantling bedrock of the Wasatch Formation. There are alluvial fans to the west on Grass Mesa. 3.6 Unstable or Potentially Unstable Slopes According to the Garfield County Slope Hazard Study Areas 1, 2, & 3 Map 22, areas of moderate slope are depicted south of the Colorado River and Interstate 70 near the town of Rifle, Colorado, but have not been mapped as being areas of major slope hazard. The areas along County Road 333 are not mapped as a slope hazard area in the vicinity of the Site. Moderate slope hazard areas were identified along the West Mamm Creek and Mamm Creek drainages. 3.7 Corrosive or Expansive Soils and Rock According to the Soil Survey of the Rifle Area, the Potts Loam soils pose a high risk of corrosion to uncoated steel, but a low risk of corrosion to concrete. The Potts Loam soils have a low to moderate shrink -swell potential. These soil characteristics are not expected to pose a hazard to the proposed Site development as a storage yard. Some Tertiary and Cretaceous age sedimentary rocks with high clay content are capable of accepting water into their chemical structure and expanding many times their volume when dry. These sedimentary rocks and soils formed from these rock types, may expand or contract as they become wet and then dry out resulting in damage to structures built upon them. 3.8 Mudflow and Debris Fan Areas The Site is not located in an area of mapped mud flow and debris fan areas. Mudflows and debris flows have been mapped on the Rifle Quadrangle and Rulison Quadrangle further to the west of the Site. 3.9 Development Over Faults and Risk of Seismic Activity There are no major faults shown in the immediate area of the Site; however, the Site is located to the northwest of the Divide Creek anticline which trends to the northwest. The Divide Creek anticline and Wolf Creek anticline are the surface expression of compressional forces associated with movement along a blind thrust fault that occurred during the uplift of the Colorado Rocky Mountains. Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 7 Olsson Associates Golden, Colorado February 2015 Today, Colorado is considered a region of minor earthquake activity; however, there is uncertainty due to the relatively short historic record. According to the USGS Colorado Earthquake History online, newspaper accounts were the primary source of earthquake data in Colorado prior to 1962. Few earthquakes have been reported in this part of Colorado. A very minor earthquake occurred in the northwestern part of Colorado on November 22, 1982 at 3:09 a.m. MST. The magnitude 2.9 (Richter scale) earthquake was located about 18 miles northeast of the town of Rifle and was felt at a fish hatchery in the area. The largest quake in the area occurred on April 22, 1984 and had a magnitude of 3.1 on the Richter scale. The quake was felt in Carbondale and in Glenwood Springs. Of the hundreds of quakes that occurred in the Carbondale area during that time period, 12 were reported as felt. 3.10 Flood Prone Areas The facility is not shown within the FEMA 100 year flood hazard zone based on the Flood Plain Map in the Vicinity of the Town of Rifle, Garfield County, Colorado, or a Firmette Map generated from the FEMA data along the Colorado River. The Site is located approximately two miles south of the Colorado River. The Colorado River lies at an elevation of approximately 5,368 feet amsl, and the Site is located at an elevation of approximately 5,689 feet amsl. Areas along the West Fork of Mamm Creek are potentially prone to flash floods; however, the creek is located at an elevation of 5,589 feet, or 100 feet below the Site. The flood plain along the Colorado River is shown in relation to the Site on the attached F-1 Flood Plain Location Map. 3.11 Collapsible Soils According to the Soil Hazard Profile, Study Areas 1, 2, & 3, Garfield County, prepared by Lincoln-Devore Testing Laboratory in 1975-1976, the area southeast of Rifle was not identified as a soil hazard area. Collapsible soils are another type of subsidence that occurs in parts of western Colorado where unconsolidated sediments are present. This ground settlement can damage man-made structures such as foundations, pavements, concrete slabs, utilities, and irrigation works. Collapsible soils have not been mapped in the area and are not expected to be encountered in the vicinity of the Site. 3.12 Mining Activity There is no mining activity in the immediate area of the Site. There are sand and gravel operations located along the Colorado River, and there are natural gas exploration and production facilities in the area of the Site. 3.13 Radioactivity Naturally occurring radioactive materials are not expected to be an issue at the Site. Colorado oil and gas operations are not known to have a significant problem with naturally occurring radioactive materials (NORM) or technologically enhanced naturally occurring radioactive materials (TENORM); however, there have been some instances where pipe scale has contained radium and associated radon gas. A NORM survey including site specific testing Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 8 Olsson Associates Golden, Colorado February 2015 could be performed to further assess the radon potential at the Site to serve as a baseline assessment if used pipe or pipe scale is stored and is to be disposed offsite in the future. Olsson reviewed the Colorado Bulletin 40, Radioactive Mineral Occurrences of Colorado which states that nearly all of Garfield County's uranium production came before 1954, and most of that came from the Rifle and Garfield mines. Both of these mines were located along the same ore body northeast of the town of Rifle in Section 34 and Section 35, Township 4 South, Range 92 West, or approximately 10 miles to the north of the Site (Fischer, 1960). These occurrences were all hosted in the Jurassic Morrison and Entrada Formations, and the Triassic-Jurassic Navajo Sandstone, or the Triassic Chinle Formation which are known to contain uranium and vanadium deposits in the county and in the Colorado Plateau in general (Nelson-Moore, Collins, and Hornbaker, 1978). These formations lie at great depth in the vicinity of the Site and are stratigraphically below the depth of the Wasatch Formation. The Colorado Department of Public Health and Environment (CDPHE) has posted a statewide radon potential map on their website based on data collected by the EPA and the U.S. Geological Survey. Garfield County and most of Colorado has been mapped as being within Zone 1 — High Radon Potential, or having a high probability that indoor radon concentrations will exceed the EPA action level of 4 picocuries per liter (pCi/L). Radon is not expected to be a significant problem at the proposed Site, since the development will not include any occupied structures, personnel will not be onsite for extended periods, and the Site will not be developed with structures containing basements or substructures in which radon can accumulate. Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 9 Olsson Associates Golden, Colorado February 2015 4.0 CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations were made following a review of the available site data for natural and geologic hazards in the vicinity of Site located in Garfield County, Colorado. • The Site is not expected to have any buried or aboveground utilities. • Avalanche conditions are not expected to be a hazard in the area of the Site. • Rockfall areas are not a geological hazard in the area of the Site, but may exist in areas along Mamm Creek and its tributary drainages. • The Site is not in an area of landslides or potential landslides. • The Site is not in an area mapped as an alluvial fan hazard area. • Slope is not a geologic hazard in the vicinity of the site, but is in areas to the north and west along West Mamm Creek and Mamm Creek drainages. • The surface runoff is slow and the soil erosion hazard for the Potts Loam is moderate. • The Site is not located in an area of mapped mud flow or debris fan areas. • The Potts Loam soils are listed as a high risk of corrosion to uncoated steel and a low risk of corrosion to concrete. These soil characteristics are not expected to pose a geologic hazard for the proposed development at the Site. • The shrink -swell potential for the Potts Loam is low to moderate. Therefore, expansive soils are not a geologic hazard at the Site. • Collapsible soils are not present in the vicinity of the proposed Site. • No significant faults have been mapped or are known in the Site. The Site is located to the northwest of the Divide Creek anticline which was formed as a result of movement along a blind thrust fault associated with the uplift of the Colorado Rocky Mountains. • The Site is not mapped as being within the 100 -year flood plain. Flash flooding is a hazard for lower elevations along the West Fork of Mamm Creek, Mamm Creek and its tributaries, and areas along the Colorado River located approximately two miles to the north and at elevations that are 100 feet to 200 feet lower than the Site elevation. Therefore, flooding is not expected to be a natural hazard affecting the Site. • Uranium and Vanadium were mined to the northeast of the town of Rifle; and approximately ten miles north of the Site. However, these mines were developed in Jurassic age geologic formations that lie at great depth stratigraphically below the Wasatch Formation. There are no significant radioactive mineral deposits known in the immediate area of the Site. The presence of NORM may be an issue with exploration and production and could be an issue with used pipe scale or used equipment stored at the site. Radioactive materials are not expected to pose a significant hazard at the Site. Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 10 Olsson Associates Golden, Colorado February 2015 5.0 REFERENCES • Donnell, J.R., 1969, Paleocene and lower Ecoene Units in the Southern Part of the Piceance Creek Basin, Colorado, 21 p. • Fischer, R.P., 1960, Vanadium -Uranium Deposits of the Rifle Creek Area, Garfield County, Colorado, USGS Bulletin 1101, 52 p. • Grout, M. A. and Verbeek, E.R., 1992, USGS Bulletin 1787-Z, Fracture History of the Divide Creek and Wolf Creek Anticlines and Its Relation to Laramide Basin -Margin Tectonism, Southern Piceance Basin, Northwestern Colorado, 32 p. • Harman, J.B. and Murray, D. J., 1985, Soil Survey of Rifle Area, Colorado, Parts of Garfield and Mesa Counties, Colorado: U.S. Department of Agriculture, Soil Conservation Service, in cooperation with the Colorado Agricultural Experiment Station, 149 p. two plates, and 20 map sheets. • Nelson -Moore, J.L., Bishop Collins, D., Hornbaker, A.L., 2005, Colorado Geologic Survey, Bulletin 40, Radioactive Mineral Occurrences of Colorado, pp 154-158 (CD) • Robson, S.G. and Banta, E.R., 1995, USGS Hydrologic Investigations Atlas 730-C, Groundwater Atlas of the United States, Segment 2, Arizona, Colorado, New Mexico, Utah, 32 p. • Shroba R.R., and Scott, R.B., 2001, Geologic Map of the Silt Quadrangle, Garfield County, Colorado, scale 1:24,000, USGS Miscellaneous Field Studies Map MF -2331 Version 1.0, pamphlet accompanies map • Topper, R., Spray, K. L., Bellis, W.H., Hamilton, J.L., Barkman, P.E., Ground Water Atlas of Colorado, Colorado Geologic Survey, 2003, Special Publication 53, 210 p. • Tweto, 0., Moench, R.H., Reed, J.C., Jr., 1978, Geologic Map of the Leadville 1° x 2° Quadrangle, Northwestern Colorado, USGS 1-999 Online References • Colorado Oil and Gas Conservation Commission http://cogcc.state.co.us/ • Natural Resources Conservation Service - Soil Survey http://www.nrcs.usda.gov/ Slope Hazards: http://garfield-county.com/geographic-information- systems/documents/6439291200422slopehaz.pdf Tax Assessor parcel information http://garfieldco.mygisonline.com Soil Hazards: http://garfield-county.com/geographic-information- systems/documents/64335291200423soilhaz.pdf Surficial Geology of Garfield County: http://garfield-county.com/geographic-information- systems/documents/geologic-hazards/24surfgeo.pdf • Colorado Geological Survey: http://geosurvey.state.co.us/hazards • Colorado Geological Survey: http://geosurvey.state.us/land/Pages/Professional Geologist • Colorado Department of Public Health and Environment: http://co- radon.info/CO radon map.html Geologic Hazard Report Encana K19NE Storage Yard Garfield County, Colorado 11 Olsson Associates Golden, Colorado February 2015 FIGURES ENCANA OIL & GAS (USA) INC PARCEL NO. 217919300128 K1 9NE STORAGE YARD SITE LOCATION Encana Oil & Gas (USA) Inc. Wasatch Surveying Associates 906 Main Street Evanston, Wyoming 82930 Phone No. (307) 789-4545 Fax (307) 789-5722 v 0 N Scale in Feet K19NE Storage Yard Vicinity Map SECTION 19, T6S, R92W, 6th, P.M. GARFIELD COUNTY, COLORADO VICINITY MAP PROJECT No. 14-04-12 DATE: 8/22/2014 SCALE: 1:48,000 Subject Parcel 0 K19NE Storage Yard Parcels 3 Mile Buffer Perennial Stream PROJECT NO: 014-2797 DRAWN BY: DATE: JWH 11/25/2014 VICINITY MAP K19NE STORAGE YARD ENCANA OIL & GAS (USA) INC. GARFIELD COUNTY, COLORADO 0.‘ OLSSON ® ASSOCIATES 760 HORIZON DR., SUITE 102 GRAND JUNCTION, CO 81506 TEL 970.263.7800 FAX 970.263.7456 FIGURE V-1 O K19NE Storage Yard n K19NE Storage Yard Boundary Subject Parcel W Y E PROJECT NO: 014-2797 DRAWN BY: JWH DATE: 11/25/2014 TOPOGRAPHIC MAP K19NE STORAGE YARD ENCANA OIL & GAS (USA) INC. GARFIELD COUNTY, COLORADO 0/St' OLSSON ASSOCIATES 760 HORIZON DR., SUITE 102 GRAND JUNCTION, CO 81506 TEL 970.263.7800 FAX 970.263.7456 FIGURE T- 1 Qa Modern alluvium ,Qg Gravels and alluviums (Pinedale and Bull Lake age)4 INS Qg Gravels and alluviums (Pinedale and Bull Lake age) Two Wasatch Formation (including Fort II of Union equivalent at base) and Ohio Creek Formation Qg Gravels and - alluviums (Pinedale and Bull Lake age) 0 K19NE Storage Yard Subject Parcel T1 K19NE Storage Yard Boundary Perennial Stream W Y E s PROJECT NO: 014-2797 DRAWN BY: JWH DATE: 11/25/2014 GEOLOGY MAP K19NE STORAGE YARD ENCANA OIL & GAS (USA) INC. GARFIELD COUNTY, COLORADO O.‘ OLSSON ASSOCIATES 760 HORIZON DR., SUITE 102 GRAND JUNCTION, CO 81506 TEL 970.263.7800 FAX 970.263.7456 FIGURE G-1 0 K19NE Storage Yard Subject Parcel n K19NE Storage Yard Boundary Perennial Stream S E PROJECT NO: 014-2797 DRAWN BY: JWH DATE: 11/25/2014 SOILS MAP K19NE STORAGE YARD ENCANA OIL & GAS (USA) INC. GARFIELD COUNTY, COLORADO O.‘ OLSSON ASSOCIATES 760 HORIZON DR., SUITE 102 GRAND JUNCTION, CO 81506 TEL 970.263.7800 FAX 970.263.7456 FIGURE S-1 04 03 02 ' 01 06 fi 05 04 03 0c 10 11 Wil' 12 07 • .— r.. 09 10 14 6S93N 13 18 17 6S 16 92W 15 21 22 23 24 19 1111 0 20 21 22 28i 27 26 25 Subject 30 Parcel 29 28 . 27 3334 35 36 31 32 33 34 03 4 02 01 — 06 05 04 03 11 12 0710 7S 92W 09 1 q 1 0 K19NE Storage Yard Perennial Stream N r Subject Parcel - - Intermittent Stream W�E t _ e,,m 3 Mile Buffer Floodplain PROJECT NO: 014-2797 FLOODPLAIN MAP K19NE STORAGE YARD ENCANA OIL & GAS (USA) INC. GARFIELD COUNTY, COLORADO 760 HORIZON DR., 0.‘ OLSSON GRAND JUNCT® NDUN02 R ION, CO 81506 ASSOCIATES TEL 9702637800 FAX 970263.7456 FIGURE DRAWN BY: JWH F-1 DATE: 11/25/2014