(A) General Design Criteria:
(1) These design criteria are based upon the American Association of State Highway and Transportation Officials (AASHTO) Policy on Geometric Design of Highways and Streets, current edition; including guidance provided in the AASHTO publication Geometric Design Guidelines for Very Low-Volume Local Roads (ADT < 400). Where possible, all design shall be based on these guidelines and applicable design criteria set forth by AASHTO. In cases where the City of Menan road design standards are more restrictive, the City of Menan standards shall prevail. Any variation from these design guidelines shall be performed by an Idaho registered professional engineer and approved by the City of Menan.
(2) Prior to any construction of a roadway, design drawings shall be submitted to the City of Menan for review and approval. The design drawings shall address the design criteria set forth in this roadway standards document and shall include plan and profile views of the proposed roadway(s). The plans will be shown at a 1"=20 feet or 1"= 40 feet horizontal scale and will include minimum 2-foot contours. A typical section of the roadway showing, at a minimum, the roadway width, the depths of materials, the roadside drainage, and the location of the right-of- way will be required. Cross-sections of the roadway at 50-foot, or shorter, intervals may be required, at the discretion of the City. The City will have 30 days to review the design drawings and provide comment to the applicant.
(B) Roadway Classification: All roadways within the City of Menan are classified in accordance with the appropriate Federal Highway Administration legislation. All streets and highways are functionally classified as arterials, collectors, or local roads. A description of the functional classification categories is included in the City of Menan Comprehensive Plan, along with a Functional Classification System Map showing which roads carry such classifications.
(C) Public Roadway Right-of-Way:
(1) The recommended width of the public roadway right-of-way for each classification is as shown in Table 1.
Right of Way Width
120 - 210
100 - 180
42 - 55
(2) Cul-de-sacs shall have a minimum right-of-way of a 65-foot radius with additional highway right-of-way as needed to accommodate unusual cut and fill sections. The road surface (asphalt or gravel) within the cul-de-sac shall have a minimum 50-foot radius, with at least 15' of right-of-way beyond the edge of the road surface for drainage, signs, snow removal, maintenance activities and placement of utilities. A standard cul-de-sac layout is shown in Figure 1 below.
(3) All intersections of highway right-of-way lines at street and highway intersections and at cul-de-sac bulbs shall be connected by a curve having a minimum radius of twenty feet (20'). See Figure 2 below.
(4) Required Construction Permit: A right-of-way permit issued by the City of Menan is required for any construction activity within the public right-of-way of any roadway maintained by the City. This pertains to activities such as placement of utilities, service lines, private approaches or irrigation facilities. The City of Menan reserves the right to require boring of the roadway, rather than trenching through the existing pavement, when trenching may compromise the integrity of the road surface.
(5) When the right-of-way is at least 70 feet in width, utilities may be granted the following easements within the public right-of-way: Dry utilities may be granted a 5-foot easement adjacent to and within the right-of-way lines. The following will be considered a "dry" utility - electricity, gas, communications and other utilities that do not transport water. Power and gas utilities are not to be placed within the same 5-foot utility easement. Wet utilities will be granted a 3-foot easement adjacent to the outside edge of the shoulder. The following will be considered a "wet" utility - water, sanitary sewer, storm sewer and steam. Water and sewer utilities are not to be placed within the same 3-foot utility easement. Potable water and sewer lines must maintain a minimum separation of 10 feet.
(6) When the right-of-way is less than 80 feet in width, all new above ground utilities must be constructed at least 15 feet from the shoulder of the road or 24 feet from the centerline, whichever is greater and still within the right-of-way. Underground "dry" utilities should be placed near (within 4 feet of) the right-of-way line rather than along the shoulder, so the lines aren't disturbed or paved over if the road is widened. The minimum width of right-of-way of existing City roads is prescribed to be 60 feet, but some existing City road right-of-ways are 50 feet wide.
(7) The entire required right-of-way might not need to be cleared. Grading should be confined to the area necessary for construction of a properly drained road surface and to provide a clear zone for safety as outlined in the AASHTO Roadside Design Guide. Where a road passes through timber or brushy vegetation that creates a wildfire hazard, the entire right-of-way shall be treated as a fuel reduction area where trees or brush are thinned to a density where crowns do not overlap or touch and ladder fuels are removed. Construction slash shall be removed from the right-of- way along with other fuels.
(1) Table 2 shows the minimum and maximum values for various parameters used in alignment design criteria for the three functional classes of roadways.
*Roadways constructed using curb and gutter sections may have a minimum grade of 0.35%.
**Radius measured to centerline of roadway. 25 mph should be limited to 4% super-elevation.
***May be increased to 10% with special attention to maintenance consequences.
(2) All approaches shall be, for local roads, a minimum of 125 feet from any intersection, measured from the intersection right-of-way to the edge of the approach; 155 feet for collector roads; and 200 feet for arterial roads. These distances may be increased based on factors such as type of facility and amount of traffic expected to be generated. Private approaches may be a minimum of 50 feet apart. See the City of Menan Transportation Access Plan, as may be amended, for access spacing guidelines.
(3) The maximum length of a road ending in a cul-de-sac shall be 880 feet or as directed by the City Council. Dead-end streets shall be prohibited except where temporarily permitted by a subdivision-phasing plan or to provide for future connections between developments. A temporary cul-de-sac shall be provided when a temporary dead-end street serves four or more lots. The temporary cul-de-sac shall be constructed in accordance with the standards detailed in this document.
(4) One-way streets are not allowed by these roadway standards.
(5) Clear site triangles on approaches and intersections from a stop condition shall be unobstructed along both directions of the road in accordance with AASHTO Policy on Geometric Design of Highways and Streets.
(6) No solid fence or wall, planter, hedge, shrub, or other visual obstruction more than three feet in height above the grade of the adjoining roads shall be permitted within a clear sight triangle.
(7) No on- or off-street parking shall be permitted within a clear sight triangle.
(8) No trees will be permitted within a clear sight triangle. Tree branches that overhang into the clear sight triangle must be removed to a height of at least twelve (12) feet above the centerline grade of the adjoining roads.
(9) Clear zone distances shall be in accordance with the most recent edition of the AASHTO Roadside Design Guide.
(10) Mailbox turnouts shall be constructed in accordance with guidelines adopted by the City of Menan.
(E) STOPPING AND PASSING SIGHT DISTANCE
(1) The stopping and passing sight distances shall comply with the guidance provided in the current edition of the AASHTO Policy on Geometric Design of Highways and Streets. Any variation from the AASHTO design standards must consider the safety of the traveling public and be approved by the City of Menan.
(2) The eye and object heights used to determine stopping sight distance are shown in Figure 3.
(F) ROADWAY CROSS·SECTION
(1) The typical roadway details are shown in Figure 4, below, including the cross-section characteristics required for roadways within the city. The minimum width of the roadway surface for a two-lane road in a platted subdivision shall be 30 feet (a 24-foot wide traveled way with a 3-foot shoulder on each side). Additional lanes shall be a minimum of 12 feet wide, unless specifically approved by the City of Menan. Roadways that are or will be maintained by the City of Menan may be wider than 30 feet. The width of City maintained roadways will be determined by the City of Menan Public Works Director on a case-by-case basis.
(2) A minimum sub-base depth of 18 inches of pit run gravel at a width of 30 feet, compacted to 95% of standard density is required on all roads. The pit run gravel should be placed in layers not exceeding 9 inches and compacted between layers. A sub-base depth of less than 18 inches may be accepted if designed by an Idaho registered professional engineer and the design is accompanied by a geotechnical engineering report certifying the reduced depth. The City reserves the right to require more than 18 inches of sub-base depth based on knowledge of the soils at the location of the proposed project.
(3) A 4-inch depth of compacted 1/2 inch crushed gravel is required over the sub-base.
(4) If asphalt is required, the pavement shall be a minimum 24 feet wide with a minimum depth of 2.5 inches. New roads that intersect with an existing paved road will be required to be paved to the right'-of-way line of the existing road, with a minimum 30' radius at the intersection. An asphalt shall meet or exceed The City of Menan pavement mix requirements. A copy of the mix design can be obtained from the Menan Road and Bridge Department. A certified materials testing company shall conduct asphalt mix design, temperature, and compaction tests. Copies of the test results shall be sent to the City.
*If curb and gutter is installed, it shall be constructed according to the requirements of the current edition of the Idaho Standards of Public Works.
(5) Construction (ISPWC). The City of Menan shall review and approve of the type of curb to be used prior to construction. (See also sub-section 8-5-7(G)(7)).
(6) Grade at Intersections: The first 10 feet on all access approaches shall have a decline of 3% in slope (measured from the edge of pavement or the shoulder of a gravel road); the next 50 feet can be either an incline or a decline of no more than 3%.
(7) The roadway cross-section outside the traveled way and inside the public right-of-way shall follow the general guidelines of the Roadside Design Guide, published by AASHTO, current edition. This Guide shall be used to determine safety characteristics for any appurtenance such as signing, rock outcrops, or general hazards to the traveling public.
(1) All drainage facilities for new roadway construction shall be designed by an Idaho registered professional engineer and approved by the City of Menan in conjunction with the roadway plans, prior to commencing construction. The design storm return period shall be a ten (10) year, 6- hour storm and meet the winter and spring runoff needs. Any disruption of the normal drainage pattern of the area to be developed must have special consideration to accommodate future drainage.
(2) All roadside drainage ditches shall be a minimum depth of 30 inches, measured from the edge of the road surface shoulder. Drainage ditches shall be reseeded after construction with a seed mixture which is appropriate for the area, as recommended by the local Natural Resource Conservation Service (NRCS) office.
(3) Culverts used for drainage purposes should be of corrugated steel, aluminum, or concrete with the thickness and cover over the top of the pipe being in conformance with the following Table 3 (other types of materials must be approved by the City):
* Other classes of concrete pipe may be used if proper cover is provided in accordance with manufacturer's recommendations.
** Using corrugated metal pipe with 2 2/3" x 1/2" corrugations. Culverts or mutiplate installations larger than 36" in diameter, pipe-arch culverts, or any structure under extreme fills shall require special consideration to meet requirements for minimum cover and other parameters.
(4) Culverts across the roadways shall be a minimum of eighteen inches (18") diameter or the size necessary to convey the design volume of water, whichever is greater. Culverts under approach roads or driveways shall have a minimum diameter of 12" (or the size necessary), a minimum length of thirty feet (30'), and shall meet the requirements of sub-section 8-5-7(G)(3).
(5) All necessary drainage easements for accommodating drainage structures shall be shown and recorded on the plans or subdivision plat as a part of the approved plans or final plat. Drainage easements necessary for draining storm water across private property shall be shown on the plans or final plat and recorded with the City of Menan recorder, either on or with the final plat, or if there is no final plat then by a letter from the Applicant describing the areas containing the easements, such as lots or blocks, and recorded with the City of Menan.
(6) Disruption of natural drainage ditches and subsequent use of the roadway drainage ditch to convey the natural drainage is prohibited. Highway drainage ditches shall not be used for conveying irrigation water of any type. All new irrigation facilities shall be constructed and maintained outside the public road right-of-way, or outside of a private road easement.
(7) When a curb and gutter roadway section is proposed, a complete storm sewer system shall be designed and constructed under the review of an Idaho registered professional engineer. Storm water disposal and maintenance of the storm sewer system shall be the responsibility of the developer or a homeowner's association, not The City of Menan.
(8) Roadways having a centerline grade greater than 6%, and which are located in areas with erosive soils, (defined as moderate to very severe soil ratings in the Erosion Hazard (Road, Trail) portion of the National Cooperative Soil Survey published by the NRCS) shall require an hydraulic analysis be performed that addresses erosion potential within the drainage ditches or shall include additional culvert crossings (in the range of one every 300 ft. to 500 ft.) to reduce the distance of overland flow within the roadside ditches.
(1) Bridge structures shall be designed by an Idaho registered professional engineer in accordance with AASHTO Standard Specifications for Highway Bridges, latest edition, or AASHTO Load and Resistance Factor (LRFO) Bridge Design Specifications, latest edition.
(2) The minimum design vehicle for bridge and culvert design shall be an AASHTO HS-20 truck for local roads and an HS-25 truck for collector and arterial roads. Bridges may also be designed using the AASHTO Load and Resistance Factor (LRFD) Bridge Design Manual HL-93 loading.
(3) The minimum width of a bridge structure from the face-to-face of curb or the face-to-face of the guardrail or bridge rail shall be the full width of the approach roadway including pavement width and shoulder width, plus one foot 'eight inches (1'-8") on each side, for a total additional width of 3 feet 4 inches (3'-4").
(4) There shall be a minimum 50-foot long, 90 degree approach to all bridges.
(5) The vertical clearance above waterways shall be two feet above the 50 year flood, and the 100 year flood must pass beneath the bridge. The City will require a hydraulic analysis and drawings including slope and cross- sections of the waterway prior to approval of the bridge. The vertical clearance over other roadway surfaces shall be a minimum of sixteen feet (16'). Ice flow conditions can affect clearance and shall be taken into consideration by the bridge designer.
(6) Any crossing over a canal must be approved by the canal company as to type of structure, clearance and/or other criteria determined to be pertinent by the canal company.
(7) Only structures of steel, steel and concrete, or treated wood shall be used. Approval of structures using other materials will be considered and approved or disapproved by the City of Menan on a case-by-case basis.
(8) Retaining walls should be reinforced concrete, bin walls, reinforced earth, or concrete crib walls. Approval of retaining walls using other materials will be considered and approved or disapproved by the City of Menan on a case-by-case basis. All retaining wall structures shall be designed by an Idaho registered professional engineer and shall be approved by the City of Menan prior to their construction.
(9) A developer may be required to install a bridge rather than a culvert on any natural watercourse on the recommendation of the Idaho Fish and Game Department and approved by the City of Menan, where such action is required to protect the fishery.
(1) All traffic control devices (signing, pavement markings, and traffic signals) shall be shown on the design plans. The traffic control devices and their application shall conform to the Manual on Uniform Traffic Control Devices (MUTCD) as adopted in Idaho. All signs shall be installed by the Applicant prior to the acceptance of the project by the City of Menan.
(2) All temporary traffic control shall conform to the MUTCD, latest edition.
(1) Guardrail may be necessary in certain areas depending upon the need for protection of the traveling public. The City of Menan reserves the right to determine the need for guardrail under each separate circumstance. The guidelines of the AASHTO Roadside Design Guide, latest edition shall be used on developing appropriate and cost effective roadside safety provisions.
(2) The type of guardrail to be installed shall be determined for each project based on need, location and maintenance considerations.
(K) STRIPING OR PAVEMENT MARKINGS
(1) The City of Menan shall approve pavement-marking requirements subject to MUTCD requirements. The color, pattern and dimensions of marking shall be in conformance with the MUTCD, latest edition. Paint quality shall be the same as that used by the Idaho Transportation Department for their pavement markings.
(L) CATTLE GUARDS
(1) Cattle guards shall be constructed in conformance with Figure 5. Other types of cattle guards may be approved by the City of Menan on a case-by-case basis.
(2) Section 40-2310, 1daho Code, regulates the installation of cattle guards on local highways and shall be referenced when the question arises. Cattle guards shall be placed on private property when necessary for private approaches. Section 40-203(5), Idaho Code, discusses obstruction of the public right-of-way and the misdemeanor offense involved.
(M) DRAWING SUBMITTAL/APPROVALS
(1) All improvement drawings submitted for Public Works checking/approval shall include a copy of the proposed Final Plat and Development Agreement.
(2) Plats shall not be permitted to be signed/recorded until the improvement drawings have been approved and signed by all parties involved.
(3) Prior to The City of Menan issuing a letter of conditional acceptance for subdivisions, the Developer's Representative/Engineering Firm shall inspect in detail and amend the improvement drawings to "Drawings of Record". The Firm shall then submit said Drawings of Record with a letter stating the subdivision was constructed to the City of Menan Standards. Inspection reports may be required including compaction testing.
(4) Final Subdivision Guarantee - All materials and workmanship shall be warranted by the Developer/Contractor for a minimum period of one (1) year after the date the Letter of Substantial Completion has been officially entered into the City Commissioners Minutes. If repairs are required, the Contractor shall promptly repair said work, upon written notice from the City and without expense to the City.
(5) Final Bid Documents Guarantee - All materials and workmanship shall be warranted by the Developer/Contractor for a minimum period of one (1) year after the date the Letter of Substantial Completion has been officially entered into the City Council Minutes. If repairs are required, the Contractor shall promptly repair said work, upon written notice from the City and without expense to the City. If the Contractor fails to proceed with said repair after notice within a period of ten (10) days, the City will require the Contractor and his Surety be liable for all costs incurred. If emergency repairs are needed, the City may have to make said repairs and the Contractor/Developer shall pay the cost thereof.