The URL can be used to link to this page

Home My WebLink About1.16 Geohazards Report.pdf826 21 ½ Road | Grand Junction, CO 81505 | TEL 970.263.7800 | FAX 970.263.7456 Geological Hazards Report Encana Oil & Gas (USA) Inc Divide Road Produced Water Treatment Facility OA Project No. 012-0400 Encana Oil and Gas (USA) Inc. Olsson Associates Divide Road Water Facility Grand Junction, CO August 2012 OA Project # 012-0400 1 GEOLOGIC AND SOIL HAZARDS REPORT Introduction Encana Oil and Gas (USA) Inc. has proposed a Divide Road Water Facility to be located approximately 20 miles northwest of the Town of Parachute, west of Middle Fork Parachute Creek and just south of local road 401, in Garfield County, Colorado. This proposed water facility will be located in Section 26, Township 4 South, Range 96 West, of the Sixth Principal Meridian. The vicinity of this proposed Divide Road Water Facility is shown on a map provided in Figure V-1. The proposed project lies adjacent to areas already undergoing natural gas development by Encana Oil and Gas (USA) Inc. The natural gas resources that are being developed are underlying the main body of the Eocene age Uinta Formation (Tu) shown in Figure G-1. Geology The proposed project is located centrally within the Piceance Basin; 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. Structural Geology 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 westnorthwest, 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. The strata along the west to southwest-facing, steep limb of the monocline typically dip basinward, dipping at an angle of 45° or 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. The Wolf Creek Anticline and the Divide Creek Anticline are the Encana Oil and Gas (USA) Inc. Olsson Associates Divide Road Water Facility Grand Junction, CO August 2012 OA Project # 012-0400 2 two closest of these structures. The axis of the Divide Creek anticline crosses the southwestern part of the Gibson Gulch Quadrangle. 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. Surficial Geology This part of the Uinta Formation consists of siltstone, marlstone and sandstone with some minor oil shale, limestone and conglomeratic sandstone. The majority of the plateau top in the central Roan Plateau area is underlain by this part of the Uinta Formation. The cliffs at the edges of the plateau to the east and west of the location are comprised of the Parachute Creek Member of the Green River Formation and consist of oil shale, sandstone and mudstone. The rocks of the Uintah Formation are the parent material for the soils that occur at this location. Soils According to information prepared by the Natural Resources Conservation Service (NRCS) Soil Survey, soils in these sections have been mapped as Irigul channery loam, (36), Northwater loam (48), and the Parachute-Rhone loams (53) (Fig.S-1). A copy of a NCRS Custom Soil Resource Report for the project site has been provided. Irigul channery loam (36), soils are developed on 9 to 50 percent slopes and consist of welldrained soil in land setting of mountainsides and ridges. Elevations range from 7,800 feet to 8,700 feet above mean sea level. The parent material of this soil is Marl and/or residuum weathered from sandstone. The Northwater loam (48) is developed on 15 to 65 percent slopes at elevations of 7,600 to 8,400 feet and found in landform settings of mountainsides. The parent material of this soil is residuum weathered from sedimentary rock. The Parachute-Rhone loams (53) soils are developed on 5 to 30 percent slopes and consist of well-drained soils on mountainsides and ridges at elevations of 7,600 to 8,600 feet. These soils are Marl and/or residuum weathered from sandstone. According to the soils map provided in figure S-1 shows that the proposed Divide Road Water Facility is located on the Parachute-Rhone loams (53). With this, and in reference to the Table -Corrosion of Concrete within the NRCS soils report, states that the corrosion of concrete is low for this area. As for the rate of corrosion of concrete it is based mainly on the sulfate and sodium content, texture, moisture content, and acidity of the soil. According to the Table-Corrosion of Steel within the NRCS soils report it states that the corrosion rate of steel is moderate. The rate of corrosion of uncoated steel is related to such factors as soil moisture, particle-size distribution, acidity, and electrical conductivity of the soil. Further investigation may be required on as needed basis. Encana Oil and Gas (USA) Inc. Olsson Associates Divide Road Water Facility Grand Junction, CO August 2012 OA Project # 012-0400 3 Geologic Hazards According to the information provided by Garfield County, Colorado -GIS Department on slope hazards the proposed facility is located outside the boundary of the geologic study. In Figure F-1, the floodplain data provided by Garfield County, Colorado -GIS Department shows that the proposed facility does not lie within a floodplain area. Conclusions and Summary 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 Associates 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 Divide Road 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 location. Sincerely, Olsson Associates, INC. Tammie Lee Crossen Associate Geologist Attachments: Figure V-1 – Vicinity Map Figure G-1 – Geology Map Figure S-1 – Soils Map References Encana Oil and Gas (USA) Inc. Olsson Associates Divide Road Water Facility Grand Junction, CO August 2012 OA Project # 012-0400 4 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/ Proposed Divide Road Water Facility Legend Proposed Divide Road Water Facility Local Roads Parcels 0 1 2 4Miles PROJECT NO: DRAWN BY: DATE: 012-0400 Jenna Muhlbach 2/22/12 PROPOSED DIVIDE ROAD WATER FACILITY VICINITY MAP GARFIELD COUNTY, COLORADO 826 21-1/2 ROAD GRAND JUNCTION, CO 81505 TEL 970.263.7800 FAX 970.263.7456 FIGURE V -1 3-mile radium indicated by dark red circle Proposed Divide Road Water Facility Tu LegendProposed Divide Road Water Facility Local Roads Geology Type Tu -Uinta Formation PROJECT NO: DRAWN BY: DATE: 012-0400 Jenna Muhlbach 3/5/12 PROPOSED DIVIDE ROAD WATER FACILITY GEOLOGIC MAP GARFIELD COUNTY, COLORADO 826 21-1/2 ROAD GRAND JUNCTION, CO 81505 TEL 970.263.7800 FAX 970.263.7456 FIGURE G -1 Geologic data obtained from USGS 0 250 500 1,000 Feet Proposed Divide Road Water Facility 53 61 48 48 36 52 61 63 36 61 63 36 63 36 Legend Proposed Divide Road Water Facility Local Roads Soil Types 36 -Irigul channery loam, 9-50% slopes 38 -Irigual-Starman channery loams, 5-50% slopes 48 -Northwater loam, 15-65% slopes 52 -Parachute loam, 25-65% slopes 53 -Parachute-Rhone loams, 50-30% slopes 61 -Rhone loam, 30-70% slopes 63 -Silas loam, 3-12% slopes PROJECT NO: DRAWN BY: DATE: 012-0400 Jenna Muhlbach 3/5/12 PROPOSED DIVIDE ROAD WATER FACILITY SOILS MAP GARFIELD COUNTY, COLORADO 826 21-1/2 ROAD GRAND JUNCTION, CO 81505 TEL 970.263.7800 FAX 970.263.7456 FIGURE S -1 Soil Data provided by NRCS Soil Survey 0 250 500 1,000 Feet