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Home My WebLink About1.20 Encana South Middle Fork 0512Geohazards Report Encana Oil and Gas (USA) Inc South Middle Fork Water Facility OLSSON ASSOCIATES OA Project No. 012-0400 June 2012 826 21 1/2 Road 1 Grand Junction, CO 81505 1 TEL 970.263.7800 1 FAX 970.263.7456 la% OLSSON ASSOCIATES GEOLOGIC AND SOIL HAZARDS REPORT Introduction Encana Oil and Gas (USA) Inc. have proposed a South Middle Fork Water Facility that will be located approximately 4 miles north of Parachute, Garfield County, Colorado. Northwest of Interstate 70 and west of Parachute Creek and Parachute Creek Road (County Road 215), {'Yig. 2 . This proposed Water Facility will be located in the SE'/4NE'/4 of Section 33 and a small parcel of land located in the NW'/4 and in the SW 1/4 of section 34, Township 6 South, Range 96 West, of the Sixth Principal Meridian. The Encana Oil and Gas (USA) Inc., South Middle Fork Water Facility project is located basically in the center of the Piceance Basin. The proposed project lies adjacent to areas undergoing natural gas development by WPX Energy Rocky Mountain LLC. The natural gas resources that are being developed lie within the Quaternary: Pinedale and Bull Lake age gravels and alluvium deposits. Section 33 & 34, Township 6S, Range 96W, 6th P.M. Geology The proposed project is located basically in the center of the Piceance Basin, which is an irregularly-shaped elongated basin formed by tectonic forces that downwarped the earth's crust as a result of the uplift of the Colorado Rocky Mountains. Areas on all sides of the Piceance Basin have been uplifted by these same tectonic forces. The Picenace Basin is located in northwest Colorado and stretches across 6,000 square miles. The Piceance Basin is in the Green River Formation. Below the Green River Formation lies the Wasatch Formation and in turn is underlined by the Williams Fork Formation which is primarily a natural gas producer starting at approximately 4,000. Structural Geology Encana Oil and Gas (USA) Inc. South Middle Fork Water Facility February 2012 1 Olsson Associates Grand Junction, CO OA Project # 012-0400 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 southwest, the Douglas Creek Arch to the west- northwest and the axial basin uplift to the north (Grout and Verbeek, 1992). The Grand Hogback monocline is a sinuous feature comprised of Upper Cretaceous age bedrock of the Mesaverde Group, which includes the Williams Fork Formation and the underlying Mancos Shale. The Grand Hogback forms part of the boundary between two major physiographic provinces, the Colorado Plateau and the Rocky Mountain foreland. The Grand Hogback bends abruptly to the north of the Gibson Gulch Quadrangle and strata along the west - to southwest -facing, steep limb of the monocline typically dip basinward at an angle of 45° or are even overturned in some areas (Grout and Verbeek, 1992). A series of west-northwest trending, broad, gentle anticlines and synclines, are present within the Piceance Basin to the west of the Grand Hogback. There are a total of eight joint sets, or fracture -pattern trends, that have been mapped in the Wasatch and Mesaverde Group bedrock units in the area (Grout and Verbeek, 1992). These joint sets are the result of structural deformation of these sedimentary rock units through geologic time. Bedrock Geology Only two bedrock units crop out, or are exposed in the Gibson Gulch Quadrangle, the Tertiary age (Eocene and Paleocene) Wasatch Formation and the uppermost part of the upper Cretaceous age Mesaverde Group. The Wasatch Formation is at the surface or it underlies surficial deposits in most of the quadrangle. Rocks of the uppermost part of the Mesaverde Group are exposed only along the crest of the Divide Creek anticline, near the south boundary of the quadrangle, and as mentioned previously, within the Grand Hogback, located approximately three miles to the northeast on the adjoining New Castle Quadrangle. The location of the proposed facility lies next to and underlain by bedrock of the Tertiary age Wasatch Formation, including the lower Fort Union Equivalent at the base and the Ohio Creek Formation. The Wasatch Formation ranges from 3,400 feet to 5,200 feet thick in the eastern part of Piceance Basin and is more than 9,000 feet thick, according to geophysical logs of gas wells within the basin. The Wasatch Formation consists of claystone, mudstone, and siltstone interbedded with sandstone and conglomerate. Fine-grained sediments predominate the formation and range in color from very light gray, to brown, olive gray, reddish, and tan. Claystones and mudstones are poorly to moderately indurated and sandstones are generally discontinuous, commonly lenticular, and are yellowish gray to olive gray in color. Encana Oil and Gas (USA) Inc. South Middle Fork Water Facility February 2012 2 Olsson Associates Grand Junction, CO OA Project # 012-0400 Surficial Geology Gravels and alluviums of Pinedale and Bull Lake Age (Qg) (Fig 7) are found to be in the location of the proposed water facility. Within the Quaternary, it is identify as glacial deposits of the Pinedale and Bull Lake age gravels and alluvium. The Pinedale is equivalent to the Latest Glacial advancements and Bull Lake is the second -oldest glacial advance commonly interpreted in the Rocky Mountains. Erosion hazard is low in the vicinity of the proposed facility. Soils A copy of a NCRS Custom Soil Resource Report for the project site has been provided. According to information prepared by the Natural Resources Conservation Commission Soil Survey soils in these sections have been mapped as Arvada loam (3), Halaquepts (27), and the Olney loam, (50) (Fig.8). Arvada loam (3), soils are developed on 1 percent to 6 percent slopes, and consist of well drained soils on terraces, and fans. Elevations range from 5,100 feet to 6,200 feet above mean sea level. The parent material of this soil is highly saline alluvium derived from sandstone and shale. The Halaquepts (27) is developed on 0 percent to 6 percent slopes, at elevations of 5,400 to 7,400 feet. Found in landform setting of terraces, fans, and valleys. The parent material of this soil is alluvium. The Olney loam (50) soils are developed on 3 to 6 percent slopes, and consist of well drained soils on valley sides, and alluvial fans at elevations of 5,000 to 6,500 feet. These soils are alluvium derived from sandstone and shale. Alluvial and colluvial deposits consist of silt, sand, gravel, and clay found in debris fans, stream channels, flood plains, and adjacent hill slopes along tributary valleys. Depositional processes in stream channels and on floodplains are primarily alluvial, whereas colluvial and sheet -wash processes pre -dominate on debris fans, hillslopes, and along the hillslope/valley floor boundary. Undifferentiated deposits of older gravels and alluvium underlie terraces and hill slopes 10 feet to 40 feet above small perennial and intermittent streams. Geologic Hazards As depicted on the attached Slope Hazards Map (Fig. 9), the specific location for the proposed facility is not within any identified slope hazard areas. Slope hazard areas do exist surrounding the proposed site. As noted in the Geotechnical Report prepared by Yeh and Associates, the Encana Oil and Gas (USA) Inc. South Middle Fork Water Facility February 2012 3 Olsson Associates Grand Junction, CO OA Project # 012-0400 site slopes down to the west and southwest at grades of less than 2 percent. No significant faults or fissures have been identified proximate to the proposed location. The Geotechnical Report noted that "the site appeared suitable for the proposed construction." Conclusions and Summary According to the information provided by Garfield County, Colorado - GIS Department pertaining to the location of the proposed water facility, the overall geologic and soil hazards appear to be without slope hazard or soil hazards. Also, according to the Garfield County, Colorado - GIS Department the proposed water facility is out of flood plain vicinity. Stormwater controls and best management practices should take into consideration the geology and soil types present at this location. These engineering controls and practices should be used temporarily and permanently to divert stormwater away from the construction areas and to prevent additional weight which could trigger a debris flow or landslide. Pits are required to be lined by COGCC rules, but pit liners may also prevent water infiltration into unconsolidated sediments which could trigger slope failure. Pits and catchment basins should be sited and designed so as not to add weight to potentially unstable areas. Olsson appreciates the opportunity to provide this information to Encana Oil and Gas (USA) Inc. pertaining to the assessment of geologic and soil hazards associated with the proposed South Middle Fork Water Facility in Garfield County, Colorado. Olsson can conduct field work to assist with the site specific assessments of the proposed project, to determine the degree to which these hazards may affect the specific locations. Sincerely, Olsson Associates Tammie Lee Crossen Associate Geologist Attachments: Figure 2 — Vicinity Map Figure 7 — Geology Map Figure 8 —Soils Map Encana Oil and Gas (USA) Inc. South Middle Fork Water Facility February 2012 4 Olsson Associates Grand Junction, CO OA Project # 012-0400 Figure 9 — Slope Hazards Map References Grout, Marilyn A. and Verbeek, Earl R., 1992, U.S.G.S. 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. Online References Colorado Oil and Gas Conservation Commission http://cogcc.state.co.us/ Natural Resources Conservation Service - Soil Survey http://www.nrcs.usda.gov/ Garfield County, Colorado - GIS Department http://www.garfield-county.com/ http://www.garfield-county.com/oil-gas/documents/drilling_101.pdf http://oilshalegas.com/piceancebasin.html Encana Oil and Gas (USA) Inc. South Middle Fork Water Facility February 2012 5 Olsson Associates Grand Junction, CO OA Project # 012-0400