(a) Any application for development in the slope impact area shall be reviewed by the Director, who will consider such application in light of the standards of this section relating to landscape planning, soil mechanics engineering, hydrology, geology, environmental design, and architecture. It is recognized, however, that each slope impact area has unique characteristics and encounters different dynamics affecting its stability and preservation. As a result, the Director may determine for any application that certain of the following standards may not apply in whole or in part to such application so long as the Director determines that the application for development in its totality satisfies the purposes of this article to a substantial degree without creating an economic hardship as provided in § 9-119 of this article.
(b) The standards applicable to development in a slope impact area are as follows:
(1) Safety control of steep slopes.
A. The development will not jeopardize slope stability on the subject site or neighboring properties.
B. Except as necessary for an approved development, no filling, grading, and earth moving shall be occur in a slope impact area.
C. Whenever there is construction upon any property that includes or is adjacent to a steep slope zone, a fence will be erected temporarily along the top edge of the steep slope zone, during any construction and/or demolition activity upon such property.
(2) Construction techniques. All proposed structures shall have foundations designed in a manner consistent with sound engineering and geological principles. In addition, the following techniques shall be employed to enhance stabilization of the ravine or bluff:
A. Planning the development to recognize and fit the natural topography, soils, geology, hydrology, and other existing conditions on the proposed sites;
B. Orienting development so that filling, grading, and earth moving, landscaping and other site preparation is kept to an absolute minimum;
C. Preserving and enhancing the landscape through minimized disruption of natural terrain and existing vegetation;
D. Minimizing disruption or alteration of natural drainage ways;
E. Minimizing the time during which areas are bare and exposed;
F. Designing and properly locating structures so that structure's weight does not negatively impact slope stability; and
G. Considering the effect of undercutting at the base of a slope impact area caused by wave action, storm water flow, erosion, and/or channel changes.
(3) Hydrological controls.
A. Natural channels. Natural drainage ways shall be preserved to the maximum extent possible.
B. Controlled runoff. Concentrated runoff from impervious surfaces shall be collected and transported in a pipe or other approved manner to a municipal storm sewer system, if available.
C. Water discharge into steep slope. Whenever stormwater is transported across a property for discharge into a sleep slope zone, the conveyance pipes shall be of non-segmented (continuous sections of minimum 100 ft.) pipe material, which shall be installed below ground by directional boring where possible.
D. Trenching. No pipe shall be installed within a steep slope zone by excavating a trench unless such trench is approved by the Director of Public Works.
E. Pipe materials. Flexible corrugated pipes shall not be used within a slope impact area unless directional boring is found to be infeasible in the sole determination of the Director.
F. Interceptor ditches. When required by the Director pursuant to sound professional engineering principles, interceptor ditches shall be established above steep slopes in order that soil shall not become saturated and the intercepted water shall be conveyed in a pipe or other approved manner to a municipal storm sewer system, if available, or to the bottom of ravine or bluff slopes in a manner designed to prevent erosion.
G. Discharge point stabilization. Natural drainage ways shall be stabilized by landscape integration and rip-rap or other means consistent with sound professional engineering practice, to a distance below drainage and culvert discharge points sufficient to convey the discharge without channel erosion and in such a manner as to dissipate the energy of the discharge as approved by the Director of Public Works.
H. Energy dissipater. All outflow from a stormwater conveyance pipe must discharge into an energy dissipater.
I. Early completion. The overall drainage system shall be completed and made operational at the earliest possible time during construction, the schedule of which shall be approved by the Director of Public Works.
J. Impact on adjacent property. The natural or usual flow of surface or subsurface water shall not be altered or obstructed in any way by grade changes that may adversely affect the property of another by contributing either to pooling or collection of waters or to the concentration or intensification of surface water discharge. However, development which might otherwise be prohibited hereinabove may be allowed if such waters are properly drained by a pipe or other approved manner to a municipal storm sewer system, if available, or to the bottom of ravine or bluff slopes. All grade changes shall comply with Chapter 9, Article XIII of the Village Code.
(4) Vegetation and revegetation.
A. Natural vegetation. Every effort shall be made to maintain natural vegetation in the slope impact area.
B. Smallest area. At all times, the smallest practical area of raw soil shall be exposed for as short a duration of time as practical. When required by the Director pursuant to sound professional engineering principles, temporary vegetation or other acceptable cover shall be used to protect areas of raw soil exposed during development and to prevent airborne or waterborne transportation of soil.
C. Revegetation. A mixed planting of perennial and woody species is recommended for use in the slope impact areas disturbed by development.
D. Erosion control mat. Temporary erosion control matting properly staked and trenched shall be provided over raw soil areas until new vegetation is established.
(5) Filling, grading, and earth moving.
A. Minimum alterations. Filling, grading, and earth moving shall be limited to the minimum required for building foundations, driveways, drainage control structures, and immediate yard areas. With the exception of restoration efforts, substantial filling, grading, and earth moving shall not be permitted and is prohibited.
B. Erosion control. All filling, grading, and earth moving shall be accomplished in a manner that will create the lowest possible potential for airborne or waterborne transportation of soil.
C. Soil fill in steep slope zone. All fill in steep slope zone is prohibited, other than back-fill which is determined by the Director of Public Works to be necessary for slope stabilization.
D. Soil fill on table land. In conformance with generally accepted engineering standards, all fill on table land shall be stabilized to at least 90% of maximum dry density as determined in ASTM procedure D-1557 or equivalent.
E. Prompt completion. All filling, grading, and earth moving shall be accomplished in the shortest practical period of time, the schedule of which shall be approved by the Director of Public Works. All excavated material shall be removed from the slope impact area and no temporary or permanent material storage shall be permitted within the slope impact area. No existing natural vegetation shall be destroyed, removed or disturbed prior to the initiation of development activities.
(Ord. No. 2013-13-3343)