(a) Utility and street improvements shall be provided in each new subdivision in accordance with the following:
(1) Water supply and fire hydrants.
A. Public or Central Water Supply Available. If public or approved central water supply is utilized, the system shall be designed with adequate main sizes and fire hydrant water supply to meet the Association of Fire Underwriters specifications for a protected area. Such system shall be approved by the public agency or authority operating the central water system.
B. No Public Water.
1. In general. A project water system with a central well, adequately planned and protected, is often less expensive to install than an individual well serving each lot. It is also easier to protect against contamination. If contamination does occur, it is simpler and more efficient to purify the water from a central well than from numerous individual wells.
2. Project system. If a project system is planned, it shall be approved by the County Health Department and the central well drilled, tested and approved prior to filing the application for the subdivision. All land within 100 feet of a project well shall be suitably protected and restricted from development. All lines shall be six inch minimum in size, unless smaller sizes are permitted by the Planning Commission and shall be according to the standards of the nearest central or public water supply system if one exists within two miles of the development.
3. Individual wells. If the water supply is to be from individual wells, the developer shall provide at least one test well for each unit of ten or less lots in the subdivision, location of such well to be approved by the Planning Commission. Test wells shall be drilled, cased, and grout sealed into bedrock, shall be not less than twenty-five feet deep, and shall have a production capacity of not less than five gallons per minute of safe drinking water as certified by the County Health Department.
(2) Sanitary sewer facilities. No storm water shall be allowed to enter sanitary sewers. Proof shall be submitted showing that all plans of sewer extensions have been approved by the County Health Department.
A. On-the-lot sewage disposal systems are generally unsatisfactory even when carefully designed and constructed and given the best of maintenance. Poor design, inadequate construction, or poor maintenance can result in conditions dangerous to health and generally obnoxious to the senses. In view of the above, individual lot on site sewage disposal systems will not be approved within the limits of the Town.
B. Project systems shall be designed by a licensed engineer, shall provide a six inch minimum size connection to each lot, and shall have an adequate sewage disposal plant with suitable arrangements for the operation thereof. Plans shall be approved by the County Health Department.
(3) Storm drainage.
A. Capacity.
1. Storm drainage facilities shall provide a clear and protected channel fully adequate to handle runoff from a five-year storm. The developer should keep in mind that more severe storms occur at less frequent intervals and, where feasible, so design subdivisions that especially heavy runoff exceeding the capacity of the required channels can be handled with the least possible damage to improvements and structures.
2. The rational method shall ordinarily be used in computing runoff, using the formula Q = CIA wherein:
a. Q = water reaching channel, culvert, bridge, or storm sewer in cfs.
b. I = rainfall in inches per hour.
c. C = coefficient of runoff suggested is as follows:
i. Areas primarily paved or in building (such as shopping centers) - .85
ii. Primarily residential area with lots smaller than 7,500 square feet or apartment areas -
.55
iii. Primarily residential areas with lots 7,500 sq. ft, to ½ acre - .40
iv. Primarily residential areas with lots 20,000 sq. ft. or over - .35
v. Cemeteries, park land, and other permanent open areas - .30
d. A = Area in Acres.
3. Minimum pipe size shall be twelve inches.
4. In small drainage areas intended for residential development, the following rule of thumb may, if desired, be substituted where applicable.
a. For drainage areas less than one acre in area:
12" pipe
b. For drainage areas 1 to 2 acres in area: 15"pipe
c. For drainage areas 2 to 4 acres in area: 18" pipe
B. General Design.
1. Preferred runoff pattern. Preferred design of streets and grading in relation to storm drainage shall be such that runoff from roofs, driveways, and other impervious surfaces will be collected in the ditches and/or gutters along the street in short runs, (three or four hundred feet), and will then be diverted from the street surface into storm sewers or natural watercourses. Streets should be located away from watercourses unless storm sewers are to be installed.
2. Downstream disposal. Subdivision and development of an area increases and concentrates the runoff of storm water from the area. Subdividers are warned that such increase may cause flood or erosion damage to undeveloped properties lying downstream. Storm drainage channels opening on unimproved land shall empty into natural watercourses unless suitable agreement is reached with the owner of the downstream property for other method of handling. In any instance, the disposal of storm drainage downstream shall be satisfactory to the Planning Commission as advised by the Engineer.
C. Open Watercourses. The use of open watercourses for drainage may involve problems relating to safety, erosion control, stagnant water, protection of capacity, and appearance, all of which shall be given adequate attention by the developer as follows:
1. Safety. Broad, shallow courses shall be created wherever necessary to increase capacity or eliminate steep banks. Ditches shall, wherever feasible, be in the shape of a wide top V with rounded or squared invert.
2. Erosion control. Adequate measures shall be taken to prevent erosion, The Planning Commission shall require seeding, sodding, planting, riprap, or such other measures as may be necessary to prevent scouring.
3. Drainage. The developer shall guard against the creation or continuation of swampy areas or stagnant pools. The Planning Commission shall require fill and/or channel improvements in order to forestall such problems.
4. Protection of capacity. The developer shall provide adequate measures for the protection of open drainage channels by establishing drainage easements sufficiently wide (generally twenty feet) to enable the working of the channel by motorized equipment or alternately, where authorized by the Planning Commission, a center block park of a minimum width of fifty feet. All easements shall prohibit the erection of structures, the dumping of fill, or the alteration or obstruction of the watercourses without the written permission of the Planning Commission. Property lines shall be so designed as to allow drainage easements, except that drainage easements may be allowed to cross lots larger than one acre.
5. Appearance. The developer should keep in mind that natural watercourses can be an attractive asset to the subdivision as well as to the community and, where possible, should improve and beautify the watercourses to this end.
D. Design of Storm Sewers.
1. Size and grade. Storm sewers shall have a minimum diameter of twelve inches and a minimum grade of one-half per cent (0.5%).
2. Manholes. Manholes shall not be more than 300 feet apart where pipe sizes of twenty-four inches or less are used, and not more than 540 feet apart where larger sizes are installed.
3. Change in direction. Special sections of ten to fifteen feet radii shall be installed where abrupt changes are made in alignment.
E. Design of Ditches and Gutters.
1. Length of flow. Subdivisions should be so designed that length of flow or water in gutter or roadside ditch does not exceed 400 feet, except that in exceptional cases, runs up to 800 feet in length may be permitted by the Planning Commission. Runs exceeding the maximum shall be put in storm sewers or diverted to natural drainageways,
2. Minimum grade. All enclosed drainage courses shall be designed with sufficient grade to create a cleansing velocity of three feet per second. A lesser grade may be permitted by the Planning Board where a greater grade cannot be achieved.
3. Street crossing. Water in gutters and ditches shall not be allowed to flow over intersecting streets but shall be placed in adequate culverts.
4. Depth and shape of ditches.
a. Where roadside ditches are permitted for runs of more than 300 feet, or where subgrade drainage is necessary, the bottom of such ditch should be below the subgrade, and at a minimum, should be approximately eighteen inches below the crown of the road.
b. Ditches shall be V shaped or parabolic with sides sloping at approximately one inch vertical to three inches horizontal, except where other cross section plan is authorized.
F. Erosion Control. Suitable headwalls, endwalls, ditch seeding or sodding, and other procedures or devices to prevent erosion shall be used. (Passed 5-23-74.)