The street design requirements in the city shall follow the minimum design standards within this chapter, NCDOT Standard Specifications for Roads and Structures, NCDOT Standard Drawings, NCDOT Subdivision Manual, and the AASHTO Manual, A Policy on Geometric Design of Highways and Streets. All street improvements shall require approval from the city prior to beginning construction of the improvement. The city shall be notified prior to beginning construction.
(A) Insofar as practical, streets shall intersect at an angle of 90 degrees, at a minimum of 50 feet from the roadway intersection.
(1) In no case shall the angle be less than 75 degrees.
(2) Intersections having more than four corners shall be prohibited.
(3) Proposed streets intersecting on opposite sides of another street (either existing or proposed) shall be laid out to intersect directly opposite of each other.
(4) Intersections that cannot be aligned shall be separated by a minimum length of 200 feet between survey center lines.
(B) The minimum radius at intersections shall be 30 feet. Depending upon the type of improvement, the radii may need to be adjusted to accommodate the traffic requirements of the improvement, and shall be evaluated on a case-by-case basis.
(C) Sight triangles shall be required at intersections.
(1) The minimum sight triangle shall be 35 feet, measured along the right-of-way lines.
(2) An additional, ten-feet-by-70-feet sight triangle shall be provided at intersections connecting to NCDOT-maintained roadways.
(3) Other sight distance requirements may be required for line-of-sight by NCDOT and/or the city, and shall be evaluated on a case-by-case basis.
(D) A sight triangle shall contain no fence, structure, earth bank, hedge, planting, wall or other obstruction of a height greater than two feet above the property line grade as established by the City Public Works Director or City Engineer.
(E) The minimum longitudinal slope on all streets shall be 1%. The maximum slope on all streets shall be 12%.
(F) The crown on all streets shall be one-fourth inch per foot, measured from the centerline of the street.
(G) Embankments.
(1) The maximum slope for cuts shall be two feet horizontal to one foot vertical (2:1), and for fill embankments, two feet horizontal to one foot vertical (2:1).
(2) Fill embankments shall be formed of suitable material placed in successive layers, not to exceed more than ten inches in depth, for the full width of the cross section, including the width of the slope area.
(3) No stumps, trees, brush, rubbish or other unsuitable materials or substances shall be placed in the embankment.
(4) Each successive, ten-inch layer shall be thoroughly compacted by appropriate equipment as required by the work being performed, or other methods approved by the City Engineer.
(5) Embankments over and around all pipe culverts shall be of select material, placed and thoroughly tamped and compacted as directed by the City Engineer or his or her representative.
(H) Aggregate base course (ABC) shall be a minimum compacted depth of eight inches. The ABC shall be placed and wet set to grade prior to placing pavement.
(I) Hot-mix asphalt shall be placed at minimum depths as follows: two and one-half inches I19.0C, two inches S9.5B, placed in two one-inch lifts. All asphalt placed shall conform to the latest edition of the NCDOT QMS SuperPave Manual.
(J) A proof roll shall be required prior to placing curb and gutter, ABC and asphalt.
(1) Equipment to be used for the proof roll are as follows:
(a) Curb and gutter: loaded tandem dump truck or loaded water truck;
(b) ABC, asphalt: loaded tandem dump truck or loaded water truck.
(2) Proof rolls will not be performed on frozen subgrades, and inclement weather will void any proof roll if the associated work has not been completed.
(3) Weight requirements for equipment:
(a) Motor grader: 30,000 pounds;
(b) Water truck: 30,000 pounds:
(c) Tandem truck: 45,000 pounds.
(4) A motor grader may be used in some circumstances for a proof roll on curb and gutter only. Prior approval by the City Engineer is required for use of a motor grader.
(K) Stone base course (ABC) shall be placed at a depth as required to adequately support the design of the improvement proposed. The ABC shall be wet set and graded to provide positive drainage by either crown or super-elevation as required by the construction drawings.
(L) The material for stone base course shall conform to the requirements of Section 1006 (Aggregate Quality Control/Quality Assurance), Section 1010 (Aggregate for Non-Asphalt Type Bases) and Section 520 (Aggregate Base Course) of the NCDOT Standard Specifications for Roads and Structures.
(M) When completed, the base course shall be smooth, hard, dense, unyielding and well-bonded.
(1) The stone base shall be compacted to 100% of that obtained by compacting a sample of the material in accordance with AASHTOT 180, as modified by NCDOT, when conventional density test number three is used.
(2) When nuclear density testing is performed, a nuclear target density of at least 98% shall be obtained.
(3) In addition, the nuclear density of any single test location shall be at least 95% of the nuclear target density.
(4) Compaction shall be obtained by rolling with ring or tamping roller, or with a pneumatic-tired roller with a minimum weight of ten tons.
(N) ABC will not be allowed within widening strips less than five feet in width.
(O) Prior to any asphalt being placed, a pre-pave meeting is required and shall be scheduled with the Public Works Director.
(P) Asphalt shall not be placed unless the minimum temperatures are met in NCDOT Specifications, Section 610.
(1) Do not place surface course material that is to be the final layer of pavement between December 15 and March 16 of the next year if it is one inch or greater in thickness, or between November 15 and April 1 of the next year if it is less than one inch in thickness, unless otherwise approved.
(2) Do not place plant mix base course that will not be covered with surface or intermediate course during the same calendar year, or within 15 days of placement if the plant mix is placed in January or February.
(Q) Drainage shall be maintained on the streets between the first lift of S9.5B and the second lift of S9.5B when the street is accepted.
(R) Surfaces shall be tacked when asphalt is being placed over existing asphalt streets or adjoining concrete, storm drain and sanitary sewer structures. In the event more than one lift of asphalt is placed in a single day, tack is still required between lifts.
(S) All asphalt cuts shall be made with a saw when preparing street surfaces for patching or
widening strips. Milling is an acceptable alternative to saw cuts when applicable.
(T) Paper joints shall be used to seal the ends of an asphalt pour so that future extensions can be made without causing rough joints.
(U) When placing asphalt against existing surfaces, a straight edge shall be used to provide a smooth and consistent transition between the two surfaces at that location.
(V) Plant-mixed asphalt shall conform in all respects to Section 610 (Asphalt Concrete Plant Mix Pavements) of the NCDOT Standard Specifications for Roads and Structures.
(W) An approved NCDOT job-mix formula shall be required to be submitted for each mix to be used prior to paving.
(X) The contractor shall have a QMS roadway technician on-site during the paving operation.
(Y) Quality control for density on the asphalt is the responsibility of the contractor per the NCDOT HMA/QMS SuperPave Manual.
(1) Cores or nuclear density may be used on base, intermediate and first lift of surface-course mixes.
(2) Cores will not be permitted on the final lift of surface course.
(3) Only nuclear density testing shall be used on the final lift of surface course.
(Z) Access must be maintained during the paving operation. Residents, emergency vehicles, solid waste collection and mail delivery will need to be addressed during the pre-pave meeting.
(AA) Failure to meet the above requirements may result in the delay or prevention of street acceptance by the city or NCDOT.
(BB) Proposed street rights-of-way shall be graded to their full width for ditch-type streets or to a minimum of 50 feet. Finished grade, cross section and profile of the roadway shall be designed by a professional engineer or registered land surveyor, and approved by the City Engineer.
(Ord. passed 8-8-2019)