25.247 Erosion control.

(a) Slopes. The faces of cut and fill slopes shall be prepared and maintained to control against erosion. This control may consist of effective planting. If planting is required by the city engineer or as a condition of approval of the tentative map, the planting plan shall be approved by the city’s architectural approval committee. The protection for the slopes shall be installed as soon as practicable and prior to calling for final approval. Where cut slopes are not subject to erosion due to the erosionresistant character of the materials, such protection may be omitted.

(b) Other devices. Where necessary, check dams, cribbing, riprap or other devices or methods shall be employed to control erosion and provide safety.

(c) The following basic design principles and standards shall serve as minimum guidelines to control erosion and reduce sedimentation:

(1) Stripping or burning of vegetation, grading, or other soil disturbance shall be done in a manner which will minimize soil erosion.

(2) Existing natural vegetation shall be retained, protected, and supplemented where necessary. Site development shall be accomplished so that existing trees can be preserved whenever possible and practical.

(3) Exposure of soil to erosion by removal of vegetation shall be limited to the smallest area practical and for the shortest time practical. Soil exposure shall not exceed an area in which development can be completed during a single construction season to ensure that soils are stabilized and vegetation is established well in advance of the rainy season (October 15 - April 15).

(4) Facilities shall be constructed to retain sediment produced on site.

(5) Sediment basins, sediment traps, diversions or similar required measures shall be installed well in advance of any clearing or grading, and maintained through any such operations until removal is authorized by the city engineer.

(6) Temporary seeding, mulching, or other suitable stabilization measures shall be used to protect exposed erodible areas during development and advance of the rainy season (October 15 - April 15).

(7) Permanent control structures and final vegetation should be installed as soon as practical in the development, and a longrange maintenance plan developed and adhered to.

(8) Provisions shall be made to accommodate the increased runoff caused by altered soil surface conditions during and after development.

(9) Surface runoff rates in excess of predevelopment levels shall be retarded where needed by appropriate structural and vegetative measures.

(10) Slopes, both cut and fill, shall not be steeper than two horizontal to one vertical (2:1), unless a thorough geological and engineering analysis indicates that steeper slopes are safe and appropriate erosion control measures are specified.

(11) Cuts and fills shall not encroach upon natural water courses, their flood plains, or constructed channels in a manner so as to adversely affect other properties.

(12) Disposal of cleared vegetation and excavated materials shall be done in a manner which reduces the risk of erosion and shall strictly conform to the provisions of the approved grading permit. Topsoil shall be conserved for reuse in revegetation of disturbed areas whenever possible.

(13) Proposed development and roadway alignments should be fitted to the topography and soils to minimize erosion.

(14) Waterways shall be designed to avoid erosion as much as practical. Wide channels should be constructed with flat slopes, and the channel and slopes should be lined with grassor other appropriate vegetation. Every effort must be made to preserve natural channels and drainage ways. (Ord. No. 80-31, § 2.)

(15) Runoff shall be diverted away from denuded slopes or other critical areas with barriers or ditches.

(16) Construction access routes should be limited and access points should be stabilized.

(17) Clearing limits, easements, setbacks, sensitive or critical areas and their buffers, trees and drainage courses shall be delineated by marking them in the field.

(18) A contingency plan shall be prepared in the event of unexpected rain or BMP failure including, but not limited to, an immediate response plan, storing extra or alternative control materials on-site, notifying the local agency, etc.

For specific information on erosion and sediment control measures, refer to the latest edition of the Manual of Standards for Erosion & Sediment Control Measures developed by the Association of Bay Area Governments.