(A) Street intersection layout. Street intersections shall not include more than four street approaches. Streets shall be designed to intersect at right angles whenever possible. Sight distance easements shall be shown and dedicated on the record drawings of the development, and should reflect a triangular area as determined by details in Article A.6. Within this triangle, there shall be no sight-obscuring or partial sight-obscuring wall, fence, sign, or full-grown foliage higher than 30" above the edge of pavement. In the case of trees, there shall be no foliage lower than 15' above the top of curb grade when foliage is saturated with rain. Vertical measurement shall be made by the Public Works Director from the top of the nearest curb or, if no curb exists, from the edge of the nearest traveled roadway finish-grade surface. Offsets of local streets shall have a minimum of 125' between centerlines.
(B) Traffic control and road name signs.
(1) All traffic control and road name signs shall be installed at no cost to the town as part of the development. The design professional shall show the location and type of signs to be installed on the construction plans and specifications. All traffic control signs shall conform to the requirements of the Manual on Uniform Traffic Control Devices for Streets and Highways. All road name signs in proposed publicly maintained rights-of-ways should be constructed as indicated by details in Article A.6.
(2) In the event a road name sign is request on a town non-standard road, approval must be obtained from the Town Public Works Department. Details and color-coding are indicated in Article A.6.
(C) ADA requirements. All pedestrian ways and curb construction shall be in accordance with the latest edition of the Americans with Disabilities Act Accessibility Guidelines (ADAAG).
(D) Specific right-of-way information.
(1) Causeways. Streets to be constructed on causeways shall meet all of the requirements contained within these specifications and the causeway shall also meet the following requirements:
(a) The minimum street centerline elevation at finish grade shall be 6.5' above mean sea level.
(b) The minimum side slopes shall be 2:1, preferably 3:1(horizontal/vertical).
(c) The minimum top width of the roadway shall be as defined by the road classification plus 6' wide shoulders (as measured from the edge of travel way to the face of the guide rail) if SCDOT standard guide rails are constructed. If no guide rails are constructed, 9' wide shoulders shall be required on each side of the travel way.
(d) The developer shall provide copies of the approved permits or application ID numbers from all applicable regulatory agencies should expanding the causeway roadbed beyond the toe of the original roadbed be required.
(2) Bridges. Bridges shall be designed in accordance with the AASHTO Standard Specifications for Highway Bridges, current edition and interims, as well as meet the following requirements:
(a) Live load: HS 20-44 loading or an alternate military loading, whichever produces the greatest stress.
(b) The minimum travel way centerline elevation shall be 6.5' above mean sea level.
(c) The minimum width of the bridge shall be 24' clear roadway width.
(d) The minimum clear width for all bridges on streets with curbed approaches should be the same as the curb to curb width of the approaches, but not less than 24' clear roadway width.
(e) For streets with shoulders and no curbs, the clear bridge width preferably should be the same as the roadway width. However, in no case should it be less than 24' or the travel way width plus 2' each side, whichever is greater.
(f) Pedestrian ways on the approaches shall be carried across all new structures.
(g) SCDOT standard guide rails shall be required.
(h) All bridges shall be concrete structures supported on concrete piles.
(i) The developer shall provide copies of approved permits from applicable regulatory agencies for the construction of bridges.
(j) The Public Works Director may consider design alternatives to the aforementioned standards. Any request for design alternatives must be submitted in writing and include details and justifications for each requested alternative. Written approval by the Public Works Director of the requested alternative is required prior to proceeding with construction.
(3) Stub streets. Stub streets extending to the boundary or property line of the subdivision shall be constructed simultaneously with the other streets in the development and shall be constructed in the same manner.
(4) Cul-de-sac streets. Cul-de-sacs shall be provided at the terminus of closed end streets with minimum dimensions as indicated below.
(a) Circular turnaround: See details in Article A.6.
(b) Y or T turnaround: Permissible only where a cul-de-sac street serves 20 dwelling units or less and upon approval by the Public Works Director. The design engineer must demonstrate that the road configuration will allow both emergency and service vehicles to turn around.
(5) Temporary cul-de-sacs. Temporary cul-de-sacs shall be provided when incremental road construction and/or phasing is requested by the developer. Temporary cul-de-sacs shall be constructed as required by this section. Unpaved temporary cul-de-sacs shall require an additional 2" (compacted depth) of base course.
(6) Construction access. The design professional shall identify the development's construction access routes and submit its proposed road section and surface course design for approval by the Public Works Director.
(7) Inverted crown roads. The use of inverted crown roads will require the written approval of the Public Works Director. Requests for the use of an inverted crown road shall be in writing and include an explanation of why a typical crown roadway section cannot be used. Inverted crown roads shall only be considered for paved road surfaces.
(E) Pedestrians ways within publicly dedicated right-of-way. When placed within the public right-of-way, pedestrian ways shall be constructed as specified below:
(1) Asphalt sidewalk:
(a) An asphalt sidewalk shall have a minimum asphalt thickness of 1-1/2" inches and a minimum base course thickness of 4". The minimum width for pedestrian ways shall be 4'. All work, materials, methods, and equipment, unless specified otherwise herein, shall be in accordance with the CTC (SS) or the SCDOT (SS).
(b) For additional ADA requirements see division (D)(2) above.
(2) Concrete sidewalk: A concrete sidewalk shall have a minimum thickness of 4" except at driveways where the minimum thickness shall be 6". Transverse expansion joints shall be placed at intervals of not more than 50'. The minimum width for pedestrian ways shall be 4'. All work, materials, methods, and equipment, unless specified otherwise herein, shall be in accordance with the CTC (SS) or the SCDOT (SS).
(F) Road surfaces types.
(1) Earth roads.
(a) The town standard earth roadway is identical in cross section to a town standard paved road except that roadbed stabilization may require that material be mixed into the existing soil material, as needed, to a depth of 6" to achieve suitable compaction. The crown shall be 6". Town Public Works' inspectors will determine whether the prepared subgrade material and earth road overlay soil are acceptable.
(b) A suitable soil is required for a minimum depth of 18" to provide a street that will serve the traffic needs in extremely dry, normal, and in wet weather. Where necessary, a stabilizing type soil shall be added and properly mixed with the soil in place for a depth of not less than .6".
(c) Earth roads, when intersecting with an existing paved road, shall have a paved apron extending to the paved road's right-of-way and when intersecting with a rocked road, shall have a rocked apron extending to the rocked road's right-of-way.
(2) Rock roads.
(a) The town standard rock roadway is also identical in cross section to a town standard paved road except that the subgrade is mixed with a 4" minimum aggregate base course worked into the top 2" of the existing subgrade, creating a 6" deep compacted rock surface, meeting the CTC (SS) or the SCDOT (SS). The road crown shall be a minimum of 6". The rock material shall be Crusher-Run granite aggregate unless otherwise approved by the Public Works Director.
(b) Rocked roads, when intersecting with an existing paved road, shall have a paved apron extending to the edge of the paved road's right-of-way.
(3) Paved roads. The town standard paved roadway is shown in detail in Article A.6. The town standard asphalt pavement is a minimum 2"compacted hot plant mix asphaltic concrete meeting the CTC (SS) or the SCDOT (SS) type one, or equal. Asphaltic concrete material is to be placed on a minimum compacted base course meeting the CTC (SS) or the SCDOT (SS), and an approved subgrade (see pavement design below).
(G) Pavement design.
(1) Pavement base and surface courses.
(a) The base course shall meet the CTC (SS) or the SCDOT (SS). The width of the base course shall be 12" greater than the width of the surface course; i.e., 6" on each side of the roadway. The compacted depth of the base course shall be 6" or greater as approved by the Public Works Director. After the base course has been properly blended, mixed, wetted, shaped, and compacted to the approved typical section and has been seasoned sufficiently and proof-rolled, the surface course shall be applied. Proof-rolling shall be accomplished as described in the CTC (SS) or the SCDOT (SS) for the proof-rolling of the subgrade except that the minimum total weight of the testing vehicle shall be in the 30-35 ton range.
(b) The surface course materials, placement, and protection shall meet the requirements of the SCDOT (SS) type C or equal. The compacted depth of the surface course shall be no less than 2" or greater as approved by the Public Works Director. Weather and seasonal restrictions to placement of the bituminous materials are described in the CTC (SS) or the SCDOT (SS).
(2) Pavement section for typical residential roadway.
(a) The town standard asphalt pavement section for use on residential roadways is a minimum 2" compacted hot plant mix asphaltic concrete meeting the CTC (SS) or the SCDOT (SS), type one or equal. This material is to be placed on a 6" minimum compacted base course meeting the CTC (SS) Section 306, and an approved subgrade. A prime coat meeting the CTC (SS) or the SCDOT (SS) is required when the base course will not be paved within two weeks.
(b) Roadways serving large residential areas or phased subdivisions may require pavement designs, exceeding the minimum requirements, as determined by the Public Works Director.
(3) Pavement design for commercial/ industrial use roadways. The design engineer shall provide a pavement design for all roadways that serve commercial and industrial uses. The design shall include at a minimum 2" of compacted hot plant mix asphaltic concrete meeting the CTC (SS) or the SCDOT (SS) type one, or equal, and a minimum 6" of compacted base course meeting the CTC (SS) or the SCDOT (SS), with an approved subgrade. The pavement design shall include information on anticipated traffic counts, traffic loadings, and site-specific soils. Further, the Public Works Director may require other pertinent information. A site-specific geotechnical report prepared by a geotechnical engineer shall be provided to substantiate/justify the proposed design for the entire length of the roadways to be constructed. A prime coat meeting the CTC (SS) or the SCDOT (SS) is required when the base course will not be paved within two weeks.
(4) Alternative pavement designs. The town will consider alternative pavement materials designs. The design professional should present appropriate design data including laboratory tests of foundation soils to substantiate/justify the proposal.
(H) Road construction.
(1) Soil testing.
(a) The Public Works Director will determine the quality of foundation soils by visual observations and adequate soil testing provided by the design professional. Without such testing, the Public Works Director will utilize judgment and experience to determine the quality of the foundation material and shall require appropriate action including, but not limited to, undercutting or mucking and replacing the excavated material with suitable earth materials. The soil-testing program shall be presented to, and approved by, the Public Works Director prior to the beginning of the testing. The testing program shall show the number and approximate locations of borings, sampling depths, and type of test to be made. Ample notice of testing schedules shall be given and a copy of all results, including recommendations, shall be provided upon completion of the tests.
(b) The testing program may establish levels or degrees of testing. For example, the testing program may call for a minimum number of tests for determination of general soil classifications and water table data for preliminary site evaluation. For the design of pavement, the testing program shall include, but is not limited to, the determination of the maximum elevation of the groundwater table, the soil classification according to the Unified Soil Classification System (laboratory test determination), and the California Bearing Ratio (CBR) (laboratory test determination utilizing 96-hour saturation). Proctor testing for determination of optimum moisture and maximum density using the modified Proctor-Test ASTM D l557 Method A, and field moisture and density tests may be required by the Public Works Director.
(2) Grading.
(a) Streets shall be graded to the designed typical section in accordance with the approved plans and profiles. Grade stakes shall be set on centerlines at intervals of not more than 100' on tangent grades and not more than 50' on vertical curves. Additional grade stakes may be required to ensure that the final grade matches the designed typical section in the profile.
(b) Grading work, materials, methods, and equipment, unless approved otherwise, shall be in accordance with the requirements of the CTC (SS) or the SCDOT (SS).
(c) No base or surfacing materials shall be placed before the subgrade is inspected and approved by the Public Works Director.
(d) In general, soils classified lower than "SC," according to the Unified Soil Classification System, are not acceptable for the upper 24" of the subgrade.
(e) The compacted subgrade shall be proof-rolled prior to placement of any base or surfacing materials. Testing shall be performed in the presence of the Public Works Director. The testing procedure shall consist of driving a loaded tandem truck (10 cubic yard minimum load capacity, 3,035 ton minimum total weight), or other equivalent vehicle (as determined by the Public Works Director) at slow-walking speed longitudinally along the length of the roadway test area. Any areas exhibiting pumping or breaking of the surface shall be stabilized or removed to appropriate depth and replaced with suitable material, recompacted, and retested.
(3) Subgrade.
(a) Work shall consist of the construction and preparation of the subgrade – that part of the roadway intended to receive the base course, pavement, pedestrian way, curb, curb and gutter, and/or shoulders.
(b) Roads shall be graded to the designed typical section in accordance with the approved plan and profile, and shall be free of roots, trash, and other unsuitable materials for a minimum depth of 24" below the finished subgrade.
(c) A suitable soil is required for a minimum depth of 18" immediately below the base course to provide a road that will serve the traffic needs in extremely dry, normal, and in wet weather. Where necessary, a stabilizing type soil shall be added and properly mixed with the soil in place for a depth of not less than 6".
(d) When unstable material is encountered and it is necessary to perform mucking work, the roadway shall be mucked for its entire width, ditch line to ditch line or extending 2' beyond the backs of curbs; backfilled with a suitable, stable-type soil; and properly compacted. All objectionable loose rock or boulders shall be removed or broken off to a depth of not less than 24" below the surface of the subgrade.
(e) The subgrade is to be sufficiently wetted and shall be compacted for a width extending 2' outside the edges of the proposed pavement before the base course is placed.
(f) The subgrade, from a distance of 24" outside the area to be occupied by the pavement or curb and gutter, shall be compacted to not less than 95% of maximum density. The compaction shall be accomplished by using suitable construction procedures with the subgrade at optimum construction moisture content. Sprinkling to secure proper compaction may wet the subgrade. ASTM D 1557 Method A will determine maximum densities.
(g) The subgrade shall be maintained in a smooth and compacted condition, free from ruts and depressions, and shall be adequately drained. In no case shall any base, surface course or pavement be placed on a frozen, muddy, or unstable subgrade. Storing or stockpiling of materials directly on the subgrade will not be permitted except with the approval of the Public Works Director.
(4) Seeding and mulching. All unpaved areas within the right-of-way shall be seeded and mulched. The developer shall be responsible for maintenance of such seeded and mulched areas as described in the CTC (SS) or the SCDOT (SS) until the street and/or drainage system is accepted into the town maintenance system.