A.   Purpose and intent.  The purpose of establishing water quality and storm runoff control standards is to ensure that developments within the Hillside Residential zone develop proper drainage and stormwater management systems that are functional, aesthetically pleasing, integrated into the overall project development as a functional landscape feature, facilitate recharge of groundwater, and conform to state and federal law regarding pollution and water quality.  Toward these ends, the use of bioswales and landscaped water quality basins represent the preferred approach to runoff and stormwater quality control, recognizing that such features add aesthetic character, have the appearance of naturally occurring drainage channels, and when located at project entries, serve as a functional element that allows for stormwater management.
Figure 20.206.130.A
Bioswales and similar natural landscaped runoff control facilities shall be used to enhance appearance and allow for groundwater recharge.
   B.   General.  Site and subdivision features required and designed to control and retain stormwater and other runoff pursuant to the requirements of city and county ordinances and the Regional Water Quality Control Board shall be fully integrated into the design of the subdivision.  Such features shall be designed and located to account for natural drainage patterns, integration of open space into overall subdivision design, location of trails and other mobility corridors, and placement of subdivision entry statements or other aesthetic features.
   C.   Materials and color. Water retention and detention features shall consist of natural earth and plant materials consistent with the plant palette for the Hillside Residential zone set forth in the appendix to this chapter.  Concrete or similar hardscape materials shall not be permitted unless determined by the City Engineer to be the only feasible method of containing runoff.  Wherever concrete or similar structures are necessary, per drainage and stormwater control plans approved by the City Engineer, such structures shall use integral color concrete to blend with surrounding color palette that blend with the natural environment.
   D.   Detention basins.
      1.   A detention basin area with gentle slopes and lined with turf may be used as an entry feature.  Detention basins shall not be eligible for open space, park credit, or any fee credit.
      2.   The maximum slope of a detention basin side slope shall be three (3) to one (1).
   E.   Bioswales.
      1.   Bioswales shall be used to collect surface runoff before it crosses pavement areas and to reduce ponding and damage to walkways.  Bioswales shall be graded to direct water away from paved areas into detention basins.
Figure 20.206.130.E
Bioswales planted with native rocks and vegetation shall be used to the maximum extent to serve as a hillside community’s drainage system.
      2.   Bioswales shall consist of primarily herbaceous plants whose stems and leaves retard water flow and help settle pollutants, and which, with the aid of the roots, decompose into the soil.
Figure 20.206.130.D
Detention basins can be landscaped with natural materials, presenting an infrastructure element that has a pleasant and natural appearance.
(Ord. 1079, passed 11-2-04)