The purpose of this appendix is to provide classifications and definitions of roads; to provide standards for the construction and design of new roads in subdivisions; to provide for the improvement and/or reconstruction of existing private roads in existing subdivisions; to provide for the improvement and or reconstruction of county roads used to access new subdivisions. All engineering and legal cost associated with the (including, but not limited to) review, approval, inspection, and certification shall be borne by the developer through reimbursement to the county.
(A) Definitions.
(1) Classifications of roads.
(a) Paved surface - a minimum of 12-foot travel lanes (arterial road).
(b) Paved surface - a minimum of 12-foot travel lanes (collector road).
(c) Paved surface - a minimum of 10-foot travel lanes (local road).
(d) Asphalt surface - various widths (asphalt and BST) year around maintained.
(e) Gravel roads - gravel surface - winter maintained.
(f) Gravel roads - gravel surface - seasonal/minimal maintained.
(g) Unimproved/primitive - two track, public right-of-way, not maintained.
(2) Definitions of roads.
ARTERIAL. A general term including expressways, interstates, and state or county highways having regional continuity.
COLLECTOR ROAD. A street that provides for traffic movement between neighborhoods of the Local Highway Jurisdiction (LHJ) and for direct access to abutting property.
LOCAL ROAD. A street that provides for direct access to residential, commercial, industrial, or other abutting land for local traffic movements and connects to collector and/or arterial streets.
(B) Construction standards.
(1) All construction shall be in compliance with the Idaho Standards for Public Works Construction (ISPWC) latest edition as modified by the county and as follows. If there is any discrepancy between this standard and the ISPWC, the most stringent standard shall apply.
(2) All new roads within subdivisions in the county must be designed and built to a minimum of a Class-C standards prior to County Road and Bridge Department accepting said roads for subsequent maintenance and upkeep. However, an alternate road cross-section may be considered if a geotechnical investigation is performed and/or ADT shows that the cross section within these standards could be altered. The alternate cross-section must be approved by the County Engineer prior to construction.
(3) All plans for new road construction must be presented to and approved by the County Engineer and County Road Department prior to preliminary plat approval.
(4) All roads must be completely built or bonded for prior to approval of final plat.
(5) Required right-of-way: local roads: 50 feet minimum; collector roads: 50 feet minimum; and arterial roads: 80 feet minimum.
(6) Slope easement must be sufficient to contain the extent of fill and cut slopes plus an additional five feet on each side.
(7) Three feet shoulder on each side.
(8) Subgrade must be compacted and tested to meet specifications as stated in the ISPWC.
(9) Twelve inch sub-base (pit run), compacted and tested to meet specifications as stated in the ISPWC.
(10) Five inch base compacted and tested to meet the ISPWC Type 1 crushed aggregate specifications, with 95% compaction.
(11) Three inches of compacted 3/4 Class 1 w/ PG 58-34 asphalt on arterial roads, two and one- half inches of compacted 3/4" Class 2 w/ PG 58-34 asphalt on collector roads, and two and one-half inches of l/2" Class 3 w/ PG 58-34 compacted asphalt on local roads in accordance with ISPWC (see section C-23).
(12) Paved roads must be chip sealed consisting of 1/2" chips Class 3 in accordance with ISPWC.
(13) The County Road and Bridge Department shall be notified a minimum of one week prior to commencement of construction so that verification testing and inspections may be scheduled. Inspections and testing costs incurred by the county shall be paid by the entity desiring the county to accept said road. Any portion of the road found not to meet minimum standards shall be improved and/or corrected until minimum standards are achieved before road construction can continue. Once the road construction has been completed and all standards have been verified by the County Engineer and Road and Bridge Department, the developer will be notified by a formal letter of acceptance one year after construction is completed.
(C) Design standards. The arrangements, character, extent, width, grade, and location of all roads shall conform to this Development Code, and any standard specifications and drawings adopted by the County Commissioners, and shall be constructed in relation to other planned roads, to topographical conditions, to public convenience and safety, and in their relation to the proposed uses of the land to be served by such roads.
(1) New developments shall be sited where roads and other public facilities are adequate. ROADWAY ADEQUACY means roads that are classified as A, B, C, or D serve the property.
(2) When a new development changes the definition or the demand on a county road by increasing the average daily traffic, the developer may be required to participate in the cost of upgrading said county road and the cost of obtaining easements. All construction on any county road must be done under the direction of the County Road Department.
(3) New developments accessed by existing private roads shall be required to participate in the cost of upgrading of said private road surface and the cost of obtaining easements.
(4) A traffic study may be required to show the level at which the developer must participate in improving and/or reconstructing the said road to the standard that will comply with the increase of traffic from the new development. The level of participation will be determined by the County Commissioners before the approval of the preliminary plat. The road upgrade design must be submitted to the county and approved by the County Engineer prior to construction. The developer must cover the expense of any traffic studies or consultation by the County Engineer.
(5) Any new development or new building sited on a road that has been upgraded by participation of a developer or individual within the past ten years, may be required to reimburse said developer or individual a percentage of the cost of upgrading. The percentage would be determined by the County Commissioners and based on the level of benefit to the new development.
(6) The Design Engineer shall specify the ADT and the traffic speed that is to be expected when the subdivision is fully developed.
(7) Local or minor residential roads within subdivisions shall be designed to discourage their use by through traffic.
(8) Where a subdivision abuts or contains an existing or proposed arterial road, or limited access highway, the county may require frontage roads, reverse frontage roads, or such other treatment for the appropriate use of the tract.
(9) Road intersection grades shall comply with Figure 2. Roads shall be planned to intersect at 90 degrees, plus or minus ten degrees.
(10) Stopping and sight distance will be maintained at all intersections and on all curves (horizontal and vertical) as specified in Table 1.
(11) Local roads shall be built with a minimum of two ten-foot travel lanes as shown in Figure l.
(12) Arterial/collector roads shall be built with a minimum of two 12-foot travel lanes as shown in Figure 1.
(13) Intersections of local/collector roads with arterial roads shall be kept at a minimum of 600 feet between centerlines.
(14) Maximum grades for all roads shall be 8%.
(15) Changes in grade shall be connected by vertical curves of sufficient radius to provide a smooth transition and proper sight and stopping distance. Small grade changes may be accepted without vertical curves if submitted and approved by the County Engineer and Road and Bridge Department.
(16) Culverts and bridges shall be sized to provide hydraulic capacity necessary for storm water runoff. The volume of storm water runoff shall be figured on the basis of a 25-year, 24-hour storm. Minimum culvert sizes shall be 18 inches underneath any county road, and 12 inches under any driveway approach. Culverts may be either corrugated metal pipe, reinforced concrete pipe, or other acceptable material. Bridge and culvert design shall eliminate excessive water buildup.
(17) Bridges shall be built to AASHTO standards.
(18) Placement of all utilities and culverts underneath the roadway shall be completed prior to the placement of any subbase gravel.
(19) All signs shall conform to the standards specified within the current edition of the Uniform Traffic Control Device Manual. All road or address signs shall match existing signs.
(20) The standards set out herein shall be considered minimum standards. Additional standards may be required where special conditions warrant.
(21) The specifications contained within the American Association of State Highway and Transportation Officials’ (AASHTO) Policy on Geometric Design of Highways and Streets shall be utilized where this chapter does not otherwise specify.
(22) It is acknowledged that most existing roads within the county do not meet the standards of A & B and that the County Road and Bridge Department’s budget precludes widespread upgrading. However, the standards are prudent and necessary in order to ensure the traveling public’s safety and welfare.
(23) BST:
(a) Roadway must be built to meet the county’s cross section;
(b) Using moist materials in finish grade avoiding holes, ruts, washboards, or any imperfections on surface;
(c) Compact the surface using water and rollers until the surface is tight;
(d) Remove any loose material prior to installing BST;
(e) Dampen surface and allow to soak in;
(f) First pass of BST, apply oil at a rate of 0.70 and immediately cover with five-eights inch rock. Rock must have 85% fracture on two sides. Three passes with a pneumatic roller followed by three passes with steel roller;
(g) Second pass of BST, apply oil at a rate of 0.65 using one-half inch rock;
(h) Third pass same as second;
(i) After one year, the county will accept or reject road; and
(j) Complete plans must be submitted to the county’s Road Department prior to construction.
(Ord. 2007-8-13, passed 3-11-2019)