(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.

         (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.

         (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.

         (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.

      (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).

         (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.

         (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.

         (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).

         (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.

         (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.

         (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.

         (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.

      (1)   All street and development drainage shall be discharged into either:

         (a)   A tidal stream of adequate size;

         (b)   A running stream with continuous flow (freshwater creek or river) of adequate size;

         (c)   An existing drainage way (pipe, ditch, or canal) of adequate size for which there is an adequate easement, and which is maintained by the Town of James Island or another responsible public agency; or

         (d)   A wetland or critical area capable of receiving the discharge without it negatively impacting any property adjacent thereto.

      (2)   The outlet or receiving area must be of sufficient size and grade, etc. to receive the anticipated quantity of runoff from each contributing drainage basin along the route of the outlet in addition to the anticipated increase in quantity of runoff from the subject development. Where the proposed outlet ends, or near the South Carolina DHEC-OCRM Critical Line, the construction plans shall clearly show that there is an outlet of adequate size and slope to the final point of discharge. The entire length of the outlet, except approved portions within the South Carolina DHEC-OCRM Critical Area, shall be constructed on dedicated drainage easements with cleared, stable maintenance shelves for continued maintenance of the drainage way. The entire development's outlet, from sources of collection of runoff to final point of discharge, shall be evaluated by the design professional and upgraded by the developer as deemed necessary by the Public Works Director at no cost to the town.

   (C)   Drainage and other work involving another public agency. When drainage is discharged into a drainage way maintained by, or intended for maintenance by, a public agency other than Town of James Island Public Works, or if work is to be done within the road right-of-way of a public agency other than the Town of James Island, written approval must be obtained from that public agency. A copy of this approval must be furnished to the Public Works Director prior to commencing work.

      (1)   The peak runoff rates shall be determined based on the storm time/rainfall rate following a pattern Type-III Rainfall Hydrograph as defined in the Soil Conservation Service Manual TR-55.

      (2)   The design recurrence interval shall be taken to be 10 years for the collector system within the subject development, 25 years for any channeled drainage flowing through the development, and 25 years for any primary outfall drainage way from the development.

      (3)   Average return frequencies (24 hour) are defined as:

         (a)   1-year: 3.8 inches;

         (b)   2-year: 4.6 inches;

         (c)   5-year: 5.9 inches;

         (d)   10-year: 7.0 inches;

         (e)   25-year: 8.0 inches;

         (f)   50-year: 8.9 inches;

         (g)   100-year: 10.2 inches; or

         (h)   As revised by the South Carolina State Climatology Office.

      (1)   The peak release rate of stormwater from all developments where detention is utilized shall not exceed the peak stormwater runoff rate from the area in its pre-developed state for all intensities, up to and including the 25-year frequency storm.

      (2)   The design professional shall provide information required to support the pond design shown. Calculations shall be signed and sealed by the design professional and shall include stage-storage volumes, areas, depths, summary information (to include pond crest information, outfall flow rates, and computer program information), etc. Pond design shall include the proposed static water level and the two-year, 10-year, and 25-year frequency storm crest elevations. These elevations shall be shown on the drainage plans, as well as the proposed 1' contour lines from the pond bottom to 1' above the 25-year frequency storm crest elevation.

      (3)   Static water elevation in ponds shall not be less than 3' below the finished centerline elevation of the road in the general area and ponds shall not encroach on the road right-of-way at any time.

      (4)   The design should provide outfall structures that are low maintenance in nature as approved by the Public Works Director.

      (5)   The design shall provide an emergency spillway. The location, structure, invert elevations, and outlet of the emergency spillway shall be shown on the construction plans. The design shall address the 50-year and 100-year frequency storm flow rates through the emergency spillway to an approved outfall (drainage easements will be required for the emergency outfall route). Projected flood limits on downstream properties for these storm flow rates are also to be shown on the drainage plan.

      (6)   All detention facilities that require public maintenance shall be provided with access for maintenance via a constructed 30' wide drainage right-of-way from the nearest road to the facility. Plans shall include a barrier structure at the primary road right-of-way to limit vehicular access. The detention facility or pond shall include a 20' wide cleared shelf with easement around the top perimeter of the facility for maintenance access.

      (7)   For all publicly maintained detention facilities, a public drainage easement shall be dedicated over the entire facility, including the outfall and emergency spillway. For privately-maintained detention facilities, a private drainage right-of-way must provide access to the pond, the pond's outfall, and all areas defined by the pond maintenance plan.

      (8)   Dry ponds shall be designed with 3:1 (horizontal: vertical) side slopes and shall drain dry within 72 hours.

      (9)   Retention or wet ponds shall be designed with 3:1 (horizontal: vertical) side slopes above the static water level and 2:1 (horizontal: vertical) side slopes below the static water level; shall have a minimum depth of 6'; and shall be stocked with mosquito larvae-eating fish. Town of James Island Mosquito Control should be consulted regarding fish stocking information.

      (1)   The Town of James Island will discourage any drainage system that is dependent solely upon infiltration/exfiltration of stormwater runoff for the proper functioning of the system.

      (2)   Any such system shall be approved only by specific authority of the Public Works Director shall approve any such system.

      (3)   The Town of James Island will not maintain or be responsible for any infiltration/exfiltration facilities. Any such facility shall be maintained by a responsible entity of, or for, the development, and arrangements for proper and perpetual maintenance shall be guaranteed to the Town of James Island prior to the approval of the development.

      (1)   The Public Works Director will independently evaluate any storm drainage piping (other than cross-line pipes) designed to be placed at a depth or location such that the repair of that culvert would adversely impact the flow of vehicular traffic. Culvert piping crossing under the street shall be at an angle of not more than 30 degrees from the perpendicular of the street.

      (2)   Pipeline discharge capacities shall exceed maximum peak runoff rates. Ponding or head pressure shall not be considered in pipeline size determination. Computations for all drainage way size determinations shall be provided to the Public Works Director. Drainage ways located laterally off of the street should be piped to the back lot line or for the first 150' from the street right-of-way line, whichever comes first.

      (3)   Where a drainage outlet pipe extends into a lake or other similar outlet, riprap shall be placed under and around the end joint or joints of pipe as needed and on slopes at the end of the pipe.

      (4)   Minimum longitudinal slope shall be 0.4% except where specifically approved in writing by the Public Works Director.

      (5)   Submerged piping or partially submerged piping shall not be used unless where specifically approved in writing by the Public Works Director. Submerged pipe systems shall require a means of accessing the submerged pipe for maintenance purposes.

      (6)   Catch basins or junction boxes shall not be located within the radius portion of street intersections. No manhole covers or water valves will be located within the curb or gutter area or within the paved area of the roadway.

      (7)   To allow for backfill and compaction operations, 2' minimum horizontal clearance between pipelines or structures shall be provided. Reinforced concrete or riprap of a material and gradation approved by the Public Works Director shall be placed at the ends of all culverts, bends, or junction points in drainage ways and/or other locations as determined by the Public Works Director (see details in Article A.6.).

      (1)   Where drainage is directed into an existing ditch, canal, or tidal stream by use of an open ditch or pipeline, the elevation at the bottom of the existing ditch, canal, or tidal stream at the point of entry, and approximately 100' upstream and downstream, shall be shown on the drainage plans. In addition, the elevation of the bottom of the inlet ditch or invert elevation of inlet pipe at the outlet end shall be shown along with the bottom width of the existing canal or tidal stream.

      (2)   Where drainage ways are piped, catch basins shall be provided as required to appropriately receive and discharge incoming drainage. In no case shall the catch basins be more than 300' apart.

      (3)   Junction boxes with stubs shall be constructed at both ends of cross-line pipes for cross-ditches, at the outlet end of cross line pipes at outlet ditches, and at other locations as appropriate. Reinforced concrete pipes of the required sizes shall be used for all inlet and outlet stubs. Stub pipes of the required sizes shall be used to convey the street ditch drainage into the junction boxes and the inlet invert of the stub shall normally be installed approximately 0.3' below the street ditch grade. Stub pipes shall be extended a minimum of 20' from the junction box to provide maintenance vehicle access to maintenance shelves along outfall ditches.

      (4)   For minor swale ditches of 1' depth or less along side or rear lot lines that only drain a small interior area and where street drainage is not involved, a drainage easement not less than 15' in width may be utilized.

      (1)   All work, materials, methods, and equipment, unless otherwise specified herein, shall be in accordance with the requirements of the CTC (SS).

      (2)   All concrete pipes shall conform to ASTM Specifications C-76, Class III, Wall B. Joints shall conform to ASTM, C-443. Jointing materials shall be all-weather preformed joint sealant.

      (3)   Metal pipes shall be approved by the Public Works Director and shall be installed as per the recommendations of the manufacturer for their intended use. For metal piping subject to saltwater exposure, only approved aluminum piping may be used.

      (4)   Other piping materials shall be considered. Specifications should be submitted to the Public Works Director along with the design data and construction plans showing the specific intended use. Materials and methods approved by the SCDOT will be considered upon submittal of SCDOT documentation and recommendations pertaining to the use of such materials.

      (5)   Ample cover shall be provided to properly protect pipelines during construction as well as for designed usage. Minimum allowable cover for pipe at subgrade shall be not less than 6" for paved areas, and 12" for unpaved areas and in no case less than that recommended by the manufacturer.

      (6)   Minimum cover for other materials and usages shall be considered at the time of submittal of construction plans to the Public Works Director.

      (7)   All structures shall be shown clearly on the construction plans with details to show all lines, grades, elevations, joints, reinforcing, materials of construction, etc. All appropriate specification data shall be shown on the construction plans.

      (8)   Junction boxes, curb inlets, outfall boxes, or any other enclosed drainage structure exceeding 4'6" in depth shall be constructed with interior step fixtures.

      (9)   Precast concrete structures will be considered. Design and specification data should be submitted to the Public Works Director along with the design and construction plans showing the specific intended use.

      (10)   A performance bond guaranteeing restoration work must be posted with the Town of James Island and remain in effect for a period of two years from the date of acceptance of the restoration work (date of release by the Director of the Department of Public Works). This bond must be in a format approved by the Town Attorney and in accordance with terms and conditions of §§ 153.300 et seq.

 

 

      (1)   Drainage easements shall be provided for all drainage facilities intended to be included in the maintenance program of the Town of James Island. The easement shall provide adequate space for access to the facility; adequate space for the operations involved in cleaning, repairing, reconstructing, material storage and dewatering, and hauling materials to or from the area; adequate space for turning and maneuvering of the equipment; and adequate space for the sloshing and splashing of the materials being handled.

      (2)   The portions of the easement intended for equipment operations shall have suitable foundations to support the maintenance equipment and shall be graded to drain the working area but not graded to slopes or elevations causing difficulty in the operation of the maintenance equipment. Maximum lateral grade for areas in which draglines may be used in the maintenance operations shall be 5%.

      (3)   Minimum drainage easement widths shall be no less than the following:

 

 

      (4)   For depths greater than shown, larger pipe sizes, or multiple lines of pipe, additional easement width, as required by the Public Works Director, shall be provided. Required drainage easement widths for open ditches shall be as shown on details in Article A.6. The side slope of an open ditch shall not exceed 2:1, and, subject to soil stability, may be required to be flatter.