LARIMER COUNTY RURAL AREA ROAD STANDARDS

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Appendix G – Design and Construction Standards for Private Local Access RoadsSection G.7 Road Design Standardsii. Rock sizes greater than 12 inches in maximum dimensioniii. must be placed 2 feet or more below grade, measured vertically.well-iv. Rocks must be placed so as to assure filling of all voids withgraded soil.v. The upper 2 feet of fill must be compacted for stability inpreparation for placement of surfacing material.d. Slope. Fill slopes must be no steeper than 1 unit vertical in 2 units horizontal(50% slope) unless the fill is engineered and constructed in such a way as toestablish stability at a steeper slope. Design of such fills must be done by anindividual licensed by the state to do such work. Fill slopes must be seededto reestablish appropriate vegetative cover to maximize slope stability andminimize erosion. Whenever possible, existing topsoil on the site must besaved and stockpiled for dressing the slope prior to seeding.G.7.7.3 Slope SetbacksThese setback recommendations are included for general consideration to avoidconflicts and potential problems with other landowners. They should be followedwhen planning a road or other excavations.a. General. Cut and fill slopes should be set back from site boundaries inaccordance with this section. Setback dimensions are horizontal distancesmeasured perpendicular to the site boundary. Setback dimensions should beas shown in Figure 3.b. Top of Cut Slope. The top of cut slopes should not be made nearer to a siteboundary line than one fifth of the vertical height of cut with a minimum of 2feet and a maximum of 10 feet.c. Toe of Fill Slope. The toe of fill slope should be made not nearer to the siteboundary line than one half the height of the slope with a minimum of 2 feetand a maximum of 20 feet. Where a fill slope is to be located near the siteboundary and the adjacent off-site property is developed, special precautionsshould be incorporated in the work, as necessary, to protect the adjoiningproperty from damage as a result of such grading. These precautions mayinclude but are not limited to:1) Additional setbacks.2) Provision for retaining or slough walls.3) Mechanical or chemical treatment of the fill slope surface to minimizeerosion.4) Provisions for the control of surface waters.G.7.8 DrainagePlans for adequate site and roadway drainage are required for all road construction.Road design must contain provisions for stormwater drainage sufficient to achieve astandard of no ponding at all locations. Adequate design must insure the naturaldrainage system will be maintained and erosion is minimized.Larimer County Rural Area Road Standards Page G-7October 22, 2007
Appendix G – Design and Construction Standards for Private Local Access RoadsSection G.7 Road Design Standards1. Single Access Roads. Single-residence driveways should provide crossculverts or structures crossing natural drainages as needed to maintain naturaldrainage patterns and conduct stormwater away from the roadway. Theseculverts should, at a minimum, be sized to pass the flow generated by a 10-yearstorm. They should be at least 12 inches in diameter and have a minimumcross-sectional area of at least 0.78 square feet. When voluntary certification isdesired, all such structures must appear on the road grading plan and beaccepted by the Engineer before a permit can be issued.2. Multiple Access Roads. Road systems accessing multiple residences (e.g.rural subdivisions) must provide cross culverts, as needed, to maintain naturaldrainage patterns and distribute stormwater away from the roadway. Suchstructures must be sized to pass at least the flow generated by a 10-year storm.Culverts may not be smaller than 18 inches in diameter nor have cross-sectionalarea of less than 1.77 square feet. The Engineer may require more stringentdesign criteria as necessary for safety and protection of property and naturaldrainage patterns. Adequate sizing of such structures will be determined at theplanning and design stage for such road systems and must be accepted by theEngineer before a road construction grading permit is issued.3. Culvert Specification. Culverts must be either double-wall corrugated plastic orsingle wall corrugated metal pipe. Single-wall pipe may be acceptable if it can bedemonstrated that it meets the minimum requirements of this section. Aminimum of 12 inches of cover of material compacted to manufacturer’sspecifications is recommended unless manufacturers specifications indicate alesser amount is sufficient to achieve the required bearing capacity. The culvertmust be of sufficient strength and proper installation to assure a minimum of 10tons bearing capacity.4. Bridge Specification. Bridges must be constructed to comply with the generalspecifications of Chapter 7 of the Larimer County Rural Area Road Standards.G.7.9 Erosion Control and Site ReclamationErosion control and site reclamation improvements are required as part of everypermitted road construction and excavation project. A plan to control stormwater alongthe roadway to lessen the degree of concentration of stormwaters must be incorporatedin the erosion control plan. The plan must incorporate erosion control and siterestoration measures to 1) assure effective stabilization of soil materials so thatdisplacement and transport of soil materials is minimized and 2) affect restoration ofnatural vegetative ground cover to disturbed areas. In many cases the most effectivemeans of controlling erosion is reestablishment of vegetation on disturbed areas. It isrecommended that natural vegetation be left intact to the greatest extent possible.Recommendations for erosion control techniques and revegetation practices are outlinedin Larimer County Stormwater Design Standards, June 20, 2005, Addendum to Volume3 of the USDCM. If road construction will disturb one acre or greater, a StormwaterConstruction Permit is required from the Colorado Department of Public Health andEnvironment.G.7.10 Buffer Zones for Streams, Intermittent Streams and WetlandsFor roads which follow perennial stream corridors, a minimum 50-foot buffer zone ofundisturbed vegetation must be maintained between the roadway or from any fillLarimer County Rural Area Road Standards Page G-8October 22, 2007
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LARIMER COUNTYRURAL AREA ROAD STAND
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Table of Contents3.3.11 Typical Str
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Table of ContentsCHAPTER 8 - ENVIRO
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Table of Contents12.3.7.2 Conventio
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Table of ContentsG.7.12 Other Permi
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Chapter 1 - General InformationSect
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Chapter 2 - Submittal ProceduresSec
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Chapter 2 - Submittal ProceduresSec
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Chapter 3 - Submittal Requirements
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Chapter 4 - Road Design and Technic
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4.9.1.7 Design VehiclesChapter 4 -
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CHAPTER 5 - GEOTECHNICAL STANDARDS
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Chapter 5 - Geotechnical Standards
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Chapter 6 - STORMWATER MANAGEMENTSe
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Chapter 7 - Bridges and Major Drain
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Chapter 8 - Environmental and Agric
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Chapter 8 - Environmental and Agric
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9.1.3 DefinitionsChapter 9 - Roadwa
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CHAPTER 10 - ACCESS REQUIREMENTS AN
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Chapter 10 - Access Requirements an
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CHAPTER 11 - ACCESS AND UTILITY PER
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Chapter 12 - Right of Way Permittin
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Appendix A - Definitions and Abbrev
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Page 130 and 131: APPENDIX E - CONSTRUCTION TESTING F
Page 132 and 133: Appendix F - Guidelines for Traffic
Page 140 and 141: APPENDIX G - DESIGN AND CONSTRUCTIO
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Page 154 and 155: Appendix H - General NotesSection H
Page 162 and 163: APPENDIX I - VARIANCE REQUEST SUBMI
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LARIMER COUNTY RURAL AREA ROAD STANDARDS

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