(A) General design requirements.
(1) Required right-of-way:
(a) The minimum right-of-way width is 50'; however
(b) The road right-of-way must be of sufficient width to provide for the following:
1. Drainage;
2. Pavement and curb and gutter;
3. Shoulders;
4. Trees;
5. Signage;
6. Sidewalks where installed (or required); and
7. Utilities such as street lights and overhead/underground utility lines (electric, telephone, cable TV, gas, water, and sewer).
(2) Required minimum street section:
(a) Streets shall be constructed as paved streets and conform to details in Article A.6.
(b) Streets shall be constructed with curb and gutter; and
(c) Streets shall have a minimum travel way width of 24'.
(3) Required minimum street elevations: The minimum street centerline elevation at finish grade shall be 6.5' above mean sea level.
(4) Required minimum profile gradient:
(a) The minimum street profile centerline gradient shall be 0.4% except for causeways where land areas adjacent to the road embankment are jurisdictional wetlands or critical areas.
(b) Additionally, for streets using an asphalt gutter, a minimum centerline gradient of 0.5% is required.
(5) Street centerline minimum curve radius criteria:
(a) Street centerline curve radii shall meet AASHTO guidelines for the design speed limit.
(b) Where streets are designed for less than a 30 mph speed limit, the design professional shall provide supporting design data, including traffic control signage.
(c) All roads shall be designed with a minimum road centerline radius of 125'.
(d) Horizontal sight distances shall be considered in the design process.
(e) Vertical curves shall have a minimum length of 100'.
(B) Type of curb and gutter.
(1) Concrete curb and gutter:
(a) Either upright curb and gutter or roll curb and gutter may be used (see details in Article A.6). The minimum width for the upright curb and gutter shall be 1" and 2' for roll curb and gutter. The maximum If upright curb and gutter is utilized, driveway entrances for subdivision lots shall be shown on the construction plans and constructed as part of the development.
(b) The distance between expansion joints unless specified otherwise herein, shall be in accordance with the CTC (SS) or the SCDOT (SS).
(2) Asphalt curb and gutter: Asphalt curb and gutter sections shall be submitted for approval. All work, materials, methods, and equipment, unless specified otherwise herein, shall be in accordance with the CTC (SS) or the SCDOT (SS).
(C) General requirements for design of drainage systems.
(1) The design of drainage facilities for a development must be done with consideration being given to the entire drainage basin. Provisions must be made to receive and manage runoff from upstream areas and to ensure that downstream areas are not adversely impacted by discharges or runoff. The current zoning of upstream properties and associated runoff factors representing that land use, assumed to be fully developed, shall be used in determining design runoff rates and quantities. It is not to be assumed that existing developed properties without stormwater detention systems will have them in the future.
(2) Also, drainage design requirements for the entire development shall conform to § A.4.2.
(D) Roadway drainage design.
(1) Stormwater systems conveying flow to or from streets shall be piped unless otherwise approved by the Public Works Director.
(2) Curb inlet structures shall be located so that drainage shall not be carried in gutters for a distance exceeding 500' (accumulated distance). The five (5) year average return frequency storm shall not cause water to flow onto the road for a width greater than 5'. Culvert piping running longitudinally with the street shall not be located under the pavement or curb and gutter, nor shall it conflict with the normal location of under drains.
(E) Subsurface drainage.
(1) Where pipe under drains are required, their centerline shall be located 2.5', at a minimum, behind the back of the curb and they shall be properly connected to a permanent drainage outlet, such as a catch basin, junction box, or a manhole.
(2) Piped under drains shall conform to the under drain details in Article A.6. Under drain inverts shall be a minimum of 24" below the bottom of the curb and above any static lake/pond elevation.
(3) Suitable outlets for the pipe under drains shall be provided in the drainage system design.
(4) Pipe under drains shall be installed at low points in the grade on both sides of the street for a minimum distance of 100' in each direction along the street; except at locations where the design engineer can demonstrate to the satisfaction of the Public Works Director that the water table will not be within 24" of centerline subgrade elevation.
(5) Pipe under drains, where required, shall be installed before the base course is placed.
(6) Pipe under drains shall be placed in other locations as determined by the design professional or as required by the Public Works Director during construction.
(7) Pipe under drains shall be properly laid on grade and in accordance with these specifications and the CTC (SS) or the SCDOT (SS) and shall not be covered until they have been inspected and approved by the Town of James Island Public Works Department.
(8) Alternative under drain designs shall be presented to the Public Works Director for review and approval.
(F) Maintenance plan.
(1) When detention or retention facilities are required by local or state agencies or proposed by the design professional, a comprehensive stormwater management system maintenance plan must be submitted for approval by the Public Works Director. The maintenance plan shall address: frequency of maintenance, disposal of material, access to the facility, and other site specific data. The responsible entity shall acknowledge in writing their maintenance obligation and their assent to the maintenance plan. All stormwater runoff and maintenance requirements described herein shall be applicable.
(2) The Town of James Island will maintain public detention facilities to ensure that public drainage systems function as designed (stage-storage capacity of the ponds remain adequate). Any facility not maintained by the Town of James Island shall be maintained by another responsible entity. Acceptable arrangements for proper and perpetual maintenance shall be presented to the Town of James Island at the time of the project's final construction inspection. Detention ponds, lakes, or impoundments which function as a conveyance of stormwater downstream of the proposed development shall require dedicated drainage easements and maintenance shelves constructed along those systems in accordance with these regulations, unless otherwise approved by the Public Works Director.
(G) Construction plans and specifications.
(1) The construction plans shall clearly show all work to be performed in plan view, profile, cross section, details, and specifications. Specifications providing written descriptions of the work, workmanship, appearance, materials, etc., and/or special provisions may either be shown on the drawings or presented in booklet form separate from the drawings. Specifications shall comply with the CTC (SS) or the SCDOT (SS), unless otherwise directed by the Public Works Director.
(2) The following standards shall be observed and the information listed below shall be provided in the design and preparation of plans, profiles, details, drainage plans, and written specifications for construction:
(a) Include a copy of the approved preliminary plat.
(b) Plans and profiles shall be prepared on 24" x 36" or 22" x 34" sheets, having a profile at the bottom and a plan view at the top, with both the plan and profile stationing oriented in the same direction.
(c) All elevations shall be referenced to the mean sea level datum for NGVD 29).
(d) Scales shall be: vertical 1" = 2' and horizontal 1" = 50' or larger.
(e) The following must be shown in the plan view:
1. Names of the proposed roads and existing stations along the centerline of the proposed road with appropriate ties at intersecting streets.
2. The width of the right-of-way and roads.
3. Alignment information, including curve data with P.C., P.T., and P.I. angle points, as well as angles at intersections.
4. Arrows indicating the direction of drainage flow within the right-of-way, along drainage ways, through lots, and at intersections.
5. Existing and proposed utility lines and utility easements.
6. Size, type, and location of trees proposed to remain within a road right-of-way or drainage easement.
7. Road cross sections with pedestrian paths (when required).
8. Existing and proposed drainage structures and drainage easements along with rights-of-way and drainage way cross sections.
9. DHEC/OCRM Critical Line and USACOE jurisdictional wetlands.
10. Benchmarks with locations, descriptions, coordinates, and datum, etc.
11. Details shall show pond outfall structures, sight distances, traffic control devices, design speeds for roads, and other related information.
12. Other general construction details required to define the scope of work.
(f) Profiles shall show:
1. Existing street centerline elevations, showing all breaks in grade, but in no case more than 100' apart. Profiles shall include existing streets to which ties are being with elevations extending approximately 200' from intersections.
2. Proposed street centerline profile with centerline elevations every 50' on vertical curves and at every 100' along tangents and at intersections.
3. Vertical curve data.
4. Proposed and existing storm drains, sanitary sewers, water mains, pipe under drains, and cross line pipes.
5. Proposed grades of all ditches and swales on or off site. Show existing grades of incoming and outfall drainage ways for 200' upstream/downstream if no grade changes are proposed. An overall drainage plan shall be submitted along with the plans and profiles and detail sheets.
(g) An overall drainage plan shall be submitted along with the plans and profiles and detailed sheets.
1. The drainage plan sheet shall show the street layout and the entire drainage system to be constructed or improved, along with the sizes and invert elevations of drainage pipes, the widths of proposed and existing drainage easements, the direction of drainage flow (using arrows), detention ponds, outfall structures, lot drainage, and existing canals, tidal streams, etc.
2. The drainage plan shall include pertinent drainage data such as drainage areas, runoff coefficients, times of concentration (with computations), runoff volumes, soils data, detention pond routing, pond crest elevations, and other related information.
(h) Statement to be placed by design professionals on road and drainage plans: "ALL MATERIALS AND WORKMANSHIP SHALL BE IN ACCORDANCE WITH REQUIREMENTS OF THE TOWN OF JAMES ISLAND ZONING AND LAND DEVELOPMENT REGULATIONS."
(i) Statement to be signed by the owner or the authorized agent of the owner: "I certify as an agent for or as a record owner, lessee, or record easement holder, I have, or will have prior to undertaking the work the necessary approval or permission from all other persons with a legal interest in said property to conduct the work proposed in the approved subdivision construction plans."
(H) Piping and easements. Unless justification is provided, to the satisfaction of the Public Works Director, all drainage easements within the urban areas of the town shall be required to be piped except: a) swales with depths less than 24" having 5:1 side slopes and wholly contained within the easement, and b) canals (designed for a capacity exceeding that of an equivalent 36" diameter pipe).
(I) Clearing and grubbing.
(1) Except as otherwise stated herein, all primary town road rights-of-way shall be cleared and grubbed for the full width of the right-of-way. Any/all tree canopies shall be pruned to a minimum height of 15'. This work shall include the removal and disposal of trees, stumps, brush, rubbish, roots, and other objectionable materials.
(2) For streets constructed with upright or roll curb and gutter, selected specimen trees may be permitted to remain within the right-of-way when the following conditions are met:
(a) Trees are healthy, of aesthetic value, and are firmly rooted with the base of the tree being at or near the elevation of the curb or edge of pavement.
(b) The distance from the back of the curb to the nearest face of the tree is not less than 5'.
(c) Additional right-of-way is provided where necessary.
(3) Where under drains are required, the tree(s) shall be removed or the right-of-way shall be relocated.
(J) Clearing of drainage easements. The full width of all drainage easements shall be cleared of all trees, buildings, fences, stumps, brush, logs, rubbish, roots, overhanging tree limbs, overhanging utility wires or cables, or any other item that may, in the judgment of the Public Works Director, interfere with the drainage facility or the maintenance of the facility. Existing obstacles may be left in place upon approval of the Public Works Director provided that all of the following criteria are met: a) the drainage system or the obstacle cannot be easily relocated; b) adequate and safe operational easement space for maintenance by mechanized equipment is provided; c) the drainage way is not obstructed; and d) the drainage easement width is increased to accommodate the obstructions.