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HomeMy WebLinkAbout3.1 Grading and Drainage Plan Narrative FINALOXY USA WTP LP 697-16-16 and 604-12-13 Storage Sites Grading and Drainage Plan Section 4-203 (E) 1.0 Introduction The following section addresses the requirements for the Grading and Drainage Plan under Section 4-203 of the Garfield County Land Use and Development Code (LUDC). 2.0 Site Map. A site map showing locations of any existing structures, Waterbodies or hydrologic features on the site, including intermittent water features, Wetlands, and the 100 year Floodplain boundaries. Site Plans are located in the Maps and Plans Tab. Hydrologic Figures and Floodplain Figures are located in the Grading and Drainage Plan tab. 2.1 Drainage Structures. a. Locations of existing and proposed drainage structures or natural drainage features affecting site drainage on the parcel and within 10 feet adjacent to the site boundary, including street gutters, storm sewers, drainage channels, and other water conveyance structures; and Wetlands or other Waterbodies receiving storm runoff from the site. b. Preliminary engineering design and construction features for drainage structures to be constructed. Existing swales and sediment basin will allow for drainage of the site. The sites are located so that no water flows onto the locations from any direction. Proposed and existing drainage plans and structures are detailed in the Drainage Reports. Site Plans are located in the Maps and Plans tab. 2.2 Topography. Existing topography at reasonable contour intervals to provide necessary detail of the site. The map should extend a minimum of 10 feet beyond the property line and show the location of the property line. Topographic figures are detailed in the Drainage Report, located in the Grading and Drainage Plan tab. The site plans are located in the Maps and Plans Tab. 2.3 Grading Plan. A grading plan showing the proposed topography at reasonable contour intervals that provides necessary detail of the site. The plan shall show elevations, dimensions, location, extent and Slope of all proposed clearing, and Grading including building site and driveway grades. The sites were previously graded and will not require grading for storage use. Minor grading activities will be conducted to construct a graded less than 12% at the entrance of the 604-12-13 Access Road. Reducing the grade from 13.9% to 12% will allow the subject access road to remain within 7-107 Access and Roadway Design Standards. Grading figures for the proposed storage sites are located in the Drainage Reports. Contours, elevations, location, and all related features are included in the Site Plans and the Grading Figures. 2.4 Soil Stockpile and Snow Storage Areas. Probable locations of soil stockpiles and snow storage areas. Snow will be directed towards BMPs. Plowed snow will be placed near the outer boundary of the pad allowing pad swales to collect the snow melt and route it to the sediment traps. Details on snow Grading and Drainage Plan Narrative Garfield County Administrative Review, 2015 Page 1 of 5 OXY USA WTP LP 697-16-16 and 604-12-13 Storage Sites storage are located in the Drainage and Grading Reports (located in the Drainage and Grading tab) and Site Plans (located in the Maps and Plans tab). 2.5 Drainage Plan. Proposed drainage plan. OXY will utilize engineering and operational BMPs to limit runoff. The sites have been designed for stormwater to flow away from the site. Details for existing and proposed drainage plans and structures are located in the Drainage Report. 2.6 Equipment Storage Areas. Location of storage areas designated for equipment, fuel, lubricants, chemical, and waste storage with an explanation of spill containment structures. It is not anticipated that liquids will be stored at the proposed sites, however, in the event that liquids need to be stored OXY will implement the Cascade Creek Spill Prevention Control and Countermeasure Plan (SPCC) and BMPs to prevent spills of liquids. Any spill that occurs will be cleaned up immediately and disposed of properly. All liquids and semi-solids on-site will have secondary containment installed. Storage of fuels or any flammable materials will be stored on the gravel pad, approximately 25 feet by 25 feet, to reduce the impact in the event of a wildfire. A designated location for the gravel pad has not been identified. The location of fuel storage will depend on the storage of other materials. All stored combustible and/or flammable materials will comply with Garfield County Wildfire Hazards Standards, Section 7-206 in the Garfield County LUDC. The SPCC is located in the Maps and Plans tab. 2.7 Temporary Roads. Location of temporary roads designed for use during the construction period. A temporary road will not be required for the construction activities. Access roads were previously constructed for the developed site locations and for surrounding facilities. Site access roads will adhere to the Garfield County Roadway Standards, Section 7-107 in the Garfield County LUDC. Roadway standards are detailed in the Standards tab. 2.8 Areas of Steep Slope. Areas with Slope of20% or greater shall be identified by location and percentage of Slope, both for the existing site conditions and within the developed area. Areas with slope of 20% or greater are identified in the Slope Hazard Figures, located in the Grading and Drainage Plan tab. All storage will occur in the graded area with low to no slopes. Areas with slope of 20% or greater occur at the perimeter on the site boundary and outside the site boundary. The subject areas were previously disturbed and slopes indicated represent existing site conditions and the developed site. The Drainage Reports state if excessive erosion occurs on the steep slopes, erosion control blankets shall be installed. Erosion control blankets will be installed and maintained until vegetation is established. Slope stabilization efforts are detailed in the Proposed BMP's figure and the narrative of the Drainage Report. A Slope Stability report was prepared for both proposed site locations. The report determined that the two storage facilities have been designed and constructed to provide for safe access to and from Grading and Drainage Plan Narrative Garfield County Administrative Review, 2015 Page 2 of 5 OXY USA WTP LP 697-16-16 and 604-12-13 Storage Sites the pads as well as for use in drilling, operations and storage of materials. The Slope Stability Report, prepared by a Professional Engineer, is located in the Impact Analysis tab. 2.9. Construction Schedule. Construction schedule indicating the anticipated starting and completion time periods of the site grading and/or construction sequence, including the installation and removal of erosion and sediment control measures, and the estimated duration of exposure of each area prior to the completion of temporary erosion and sediment control measures. The sites were previously developed and graded. Two dump trucks per site will be required for the delivery of gravel. Minimal improvements to existing drainage features may occur. No soil removal is anticipated. Erosion control measures for the sites are detailed in the Drainage Reports. 2.10 Permanent Stabilization. A brief description of how the site will be stabilized after construction is completed. The proposed 604-12-13 Storage Site is designed to be approximately 4.59 acres for the storage pad and 10.66 acres for the Site Perimeter. The site location was previously graded. Areas around the site and access road with steep slope will be re -seeded for final stabilization. Erosion control mitigation efforts are detailed in the 604-12-13 Drainage Report. The proposed the 697-16-16 Storage Site is designed to be approximately 0.71 acres for the storage pad and 4.82 for the Site Perimeter. The site location was previously graded. Areas around the site and access road with steep slopes will be re -seeded for final stabilization. Erosion control mitigation efforts are detailed in the 697-16-16 Drainage Report. For both sites DRG stated while additional erosion mitigation measures are not expected, measures shall be taken if erosion occurs. If excessive erosion occurs on the steep slopes, erosion control blankets shall be installed and the area reseeded and mulched as needed until sufficient vegetation is reestablished to prevent erosion. 2.11 Erosion Control Measures. Plan view drawings of all erosion and sediment control measures showing approximate locations and site drainage patterns for construction phases and final design elements. Text may be necessary to accompany and explain the drawings. Typical erosion control measures should be depicted using standard map symbols. Erosion control measures are detailed in the Proposed BMP figure in the Drainage Report. Erosion control blankets will be installed and maintained until vegetation is established. 2.12 Estimated Cost. Estimated total Cost, including installation and maintenance. Construction costs, including gravel, are estimated at $20,000 per site. The annual maintenance cost for stormwater, vegetation management all inspections, additional maintenance, and operating costs is estimated at $8,000 per site. 2.13 Calculations. Any calculations made for determining rainfall, runoff sizing any sediment basins, diversions, conveyance, or detention/retention facilities. Calculations are detailed in the Drainage and Grading Report. Calculation tables for the proposed sites are located in Appendix B of the Drainage Plan. Site features are indicated in the Drainage Report, located in the Grading and Drainage Plan tab. Grading and Drainage Plan Narrative Garfield County Administrative Review, 2015 Page 3 of 5 OXY USA WTP LP 697-16-16 and 604-12-13 Storage Sites 2.14 Neighboring Areas. A description of neighboring areas with regard to land use and existing pertinent features such as lakes, streams, structures, roads, etc. The subject and adjacent parcels are zoned resource lands and public lands. According to the Garfield County Assessor's Office, surrounding land uses are listed as energy development, public lands, and agricultural. 2.15 Stormwater Management. A description of the stormwater management planning concept for the site, including both structural and nonstructural best management practices. Stormwater management plans specific to the proposed site are detailed in the Drainage Report. OXY's SWMP and BMP's will be implemented for the proposed site. A copy of the Oxy's Stormwater plan, permit, and extension letter are located in the Grading and Drainage Plan tab. 2.16 Stormwater Management Plan. Copy of the stormwater management plan application to CDPHE with date of submittal. OXY's SWMP and BMP's will be implemented for the proposed site. A copy of the Oxy's Stormwater plan, permit, and extension letter are located in the Grading and Drainage Plan tab. Stormwater management plans specific to the proposed site are detailed in the Drainage and Grading Report. 2.17 Reclamation Plan. A reclamation plan consistent with the standards in section 7-207. Oxy's Reclamation plan adheres to the standards in Section 7-207 of the Garfield County Land Use and Development Code. Proposed reclamation will be similar to or better than existing site conditions. Disturbed cut and fill slopes from the pads will be hydro -mulched and seeded with a seed mix consisting of a diversity of native or desirable nonnative species capable of supporting the post -disturbance land use. Vegetation will be established and growing within 2 growing seasons based on 70% coverage as compared to surrounding native vegetation coverage. The reclamation plan is located in the Impact Analysis tab. 2.18 Hydraulic Calculations. Hydrologic, hydraulic, and all other calculations used to size and design drainage facilities and/or structural BMPs. Hydrologic calculations were based on the proposed site size of approximately 10.66 acres (604- 12-13) and 4.82 acres (697-16-16). Calculations are detailed in of the Drainage Reports, including calculation tables. 2.18 Maintenance Requirements. Maintenance requirements for all proposed BMPs should be discussed including access, schedules, costs, and designation of a responsible party. Stormwater management plans specific to the proposed site are detailed in the Drainage Report. A copy of the Oxy's Stormwater plan, permit, and extension letter are located in the Grading and Drainage Plan tab. 2.19 Spill Prevention Control and Countermeasures Plan, if Applicable. A SPCC Plan will be required for any facility with the potential to discharge oil of any kind or in any form including, but not limited to, petroleum, fuel oil, sludge, oil refuse and oil mixed with wastes, in quantities that may be harmful to navigable water and adjoining shoreline, per EPA regulations. Grading and Drainage Plan Narrative Garfield County Administrative Review, 2015 Page 4 of 5 OXY USA WTP LP 697-16-16 and 604-12-13 Storage Sites Spill prevention details are provided in the SPCC plan, located in the Maps and Plans tab. In the event of liquids stored at the propose sites, all liquids will be contained in a secondary containment. OXY will adhere to the SPCC Plan. The SPCC Plan details unloading and loading, storage, and approved containers in the SPCC Plan. Grading and Drainage Plan Narrative Garfield County Administrative Review, 2015 Page 5 of 5