1. Whenever the evidence available to the Borough Council indicates that natural surface drainage is inadequate, the developer shall install storm sewers, culverts and related facilities as necessary to:
A. Permit the unimpeded flow of natural water courses.
B. Insure the drainage of all low points along the line of streets.
C. Intercept stormwater runoff along streets at intervals reasonable related to the extent and grade of the area drained.
D. Provide positive drainage away from on-site disposal facilities.
2. The Borough Council may require a primarily underground system to accommodate frequent floods and a secondary surface system to accommodate larger, less frequent floods. Drainage plans shall be consistent with local and regional drainage plans.
A. Accommodation for Upstream Drainage Areas.
(1) Design. Storm drainage facilities must be designed not only to handle the anticipated peak discharge from the property being developed but also from the anticipated increase in runoff that may occur when all the property at a higher elevation in the same drainage basin is fully developed.
(2) Construction.
(a) If any property at a higher elevation is the property of the developer, or if the developer has any interest in such property, drainage facilities shall be constructed to handle the anticipated peak discharge from such property.
(b) If the developer neither owns nor has any interest in any property at a higher elevation, the Borough may, at its option, participate finan cially in the construction of drainage facilities to upgrade any portion or portions of such facility necessary to meet design specifications in excess of those required of the developer, but necessary to handle the anticipated peak discharge from property at a higher elevation.
B. Downstream Drainage Areas.
(1) Adequate Existing Facilities. Where adequate existing storm sewers are readily accessible, the developer must connect his storm facilities to these existing storm sewers.
(2) Inadequate Existing Facilities. Where existing storm sewers at a lower elevation are inadequate to handle the peak discharge from a proposed development, the developer shall bear the cost of upgrading the drainage facilities at the lower elevation.
C. Abutting Properties.
(1) In the design of storm drainage facilities, special consideration must be given to preventing excess runoff on to adjacent developed or undeveloped properties. In no case may a change be made in the existing topography which would:
(a) Result in increasing any portion of the slope steeper than 1 foot of vertical measurement for 3 feet of horizontal measurement for fills, or 1 foot of vertical measurement for 2 feet of horizontal measurement for cuts within a distance of 20 feet from the property line unless an adequate retaining wall or other structure is provided.
(b) Result in a slope which exceeds the normal angle of slippage of the material involved.
(2) All slopes must be protected against erosion.
D. Drainage Upon and On Streets.
(1) Upon Streets. In order to give proper surface water drainage upon streets, a structure on a lot must be at a grade in satisfactory relationship:
(a) With established street grade.
(b) With the existing street grade where none is established.
(2) On Streets. A street must be designed so as to provide for the discharge of surface water from its right-of-way. The slope of a crown on a street shall not be less than of an inch per foot and not more than of an inch per foot. Adequate facilities must be provided at low points along the street and other points necessary to intercept runoff.
(Ord. 6/6/1977, §504)