The land proposed for subdivision shall be of such character that it can be used safely for building purposes without danger to health or peril from fire, flood or other menace.
Streets in the subdivision shall be coordinated with each other and with the existing street system in a manner satisfactory to the City Planning Board, with due regard to securing safety and convenience in travel. Due consideration shall also be given by the subdivider to the attractiveness of the street layout in order to obtain the maximum livability and amenity of the subdivision.
Provision satisfactory to the City Planning Board shall be made for the proper projection of streets or for access to adjoining property which is not yet subdivided.
Reserve strips prohibiting access to streets or adjoining property shall not be permitted, except where, in the opinion of the City Planning Board, such strips shall be in the public interest.
Cross sections shall be in accordance with the standards as shown in Table 1 below:
Alignment, grade, dead ends and intersections shall be in accordance with the standards shown in Table 2 below:
Bridges shall be designed in accordance with Table 3 below:
For normal drainage design, peak runoff rates shall be estimated by the rational method. If another design procedure is used, certification by a professional engineer must be given that the proposed design will provide protection from a storm equal in severity to that specified in Subsection B below.
A design storm with a five-year return period shall be used for normal cases, a ten-year return period for high-valued areas and a fifty-year return period for sizing of bridge openings. The average rainfall intensity for a particular return period shall be selected from Figure 1B. Departure from this design criteria may be made, provided that evidence by a professional engineer is given to the economic advantage of this departure.
Editor's Note: Figure 1B is on file in the offices of the City Clerk and City Engineer.
Runoff coefficients for the various soils encountered and for impervious surfaces shall be selected from the latest edition of the Data Book for Civil Engineers, Design, by Elwyn E. Seelye.
The percentage of impervious surfaces shall be based on the expected development planned for 20 years from the date of construction of the drainage structure and, unless shown otherwise, shall be based on the following criteria:
The initial time of concentration selected shall be 15 minutes in highly developed central sections and 20 minutes for normal residential areas and Figure 1A should be used for areas where the distance to the upstream drainage structure is large.
Editor's Note: Figure 1A is on file in the offices of the City Clerk and City Engineer.
Pipe drains shall have a minimum diameter of 12 inches and a minimum slope of 0.5%. Unless special design provisions are made, the maximum permissible velocity shall be 15 feet per second. Pipes shall be sized to flow half full at maximum design flows. Departure from this may be made in long, flat areas where surcharge may be permitted to a maximum of two feet below the ground surface, provided that detailed calculations are submitted with the design. A friction coefficient for Manning's formula or its equivalent on n=0.015 shall be used for concrete pipe and n=0.021 for corrugated metal pipe or as recommended by the individual pipe manufacturer. No drain shall be located less than 10 feet from a water main nor less than 1.5 feet below it.
Manholes shall be located at all junctions with other drains or with drainage-inlet connections and at all changes in grade and/or direction. The maximum spacing of manholes shall be 500 feet.
Except for existing watercourses, all drainage shall be underground.
Stormwater shall not be permitted to cross any roadway upon the surface but must be piped underground. Stormwater runoff, except in already existing open stream channels, shall not be permitted to flow upon the surface for a longer distance than 400 feet before it enters the underground system. Catch basins shall be located on both sides of the roadway on continuous grades at intervals of not more than 400 feet, at all sags in the roadway and near the upstream corners of the roadway at intersecting streets.
No tidal or freshwater wetlands shall be filled.
[Amended 1-10-2011 by Ord. No. 3-2011]
No land subject to flooding shall be subdivided for human occupancy unless provision shall be made by filling, diking or other means to make such land no longer subject to flooding.
Public sewers shall be not less than eight inches in diameter and have a minimum velocity of 2.5 feet per second when flowing full. No sanitary sewer shall be located less than 10 feet from a water main nor less than 1.5 feet below it.
Manholes shall be located at every change in grade, alignment or size in pipe or not more than 300 feet apart.
Easements for storm drains, sanitary sewers or water mains across lots or centered on rear or side lot lines shall be provided, where necessary, and shall be at least 20 feet wide. No line shall be permitted across land of others unless an easement in proper form is obtained permitting such line.
Where a subdivision is traversed by a watercourse, drainageway, channel or stream, the City Planning Board may require that there be provided a stormwater easement of adequate width (20 feet to 100 feet) to conform substantially to the lines of such watercourse, drainageway, channel or stream and to provide for construction or other necessary purposes.
No building, except a sewage ejector station, shall be erected within an easement.
Blocks shall not exceed 1,000 feet in length nor be less than 400 feet in length.
Lots with double frontage should be avoided whenever possible. Corner lots should, whenever practical to do so, be at least 25 feet wider than adjoining interior lots to permit greater flexibility in locating the home or structure on the lot and for better layout of yards.
[Amended 1-10-2011 by Ord. No. 3-2011]
The Board may require the reservation of land for park, playground or other recreational purposes where it makes a finding that a proper case exists for such reservation on sites containing residential units. Such findings shall include an evaluation of the present and anticipated future needs for park and recreational facilities in the City based on projected population growth to which the particular subdivision plat will contribute. In the event that the Board makes such a finding, the Board may require dedication of 10% of the gross area or a minimum of three contiguous acres of open space, whichever is greater, or, where the Board finds that a suitable park or parks of adequate size to meet the requirement cannot be properly located on such subdivision plat, the Board may require a sum of money in lieu thereof in an amount as set forth in Chapter 163, Fees. In making such determination, the Board shall assess the size and suitability of land shown on the subdivision plat which could be possible locations for park or recreational facilities as well as practical factors, including whether there is a need for additional facilities in the immediate neighborhood. Any money required by the Board in lieu of land for park, playground or other recreational purposes, pursuant to the provisions of this section, shall be deposited into a trust fund to be used by the City exclusively for park, playground or other recreational purposes, including the acquisition of property.
Due regard shall be shown for all natural features such as large trees, watercourses, scenic points, historic spots and similar community assets which, if preserved, will add attractiveness and value to the subdivision. Trees located within areas filled more than one foot shall be welled to the depth of the original ground.