810.0225 Runoff Control.

Runoff from activities subject to a development permit shall be properly controlled to prevent erosion. Erosion control and surface flow containment facilities shall be constructed and maintained to prevent discharge of sediment to surface waters or storm drainage systems. The following measures shall be used for runoff control, and shall be adequate to control runoff from a ten-year storm.

(a) Where soils having a permeability rate of more than two inches per hour, runoff in excess of predevelopment levels shall be retained on the site by methods and in quantities approved by the City Engineer. This may be accomplished through the use of infiltration basins, percolation pits or trenches, or other suitable means. This

requirement may be waived where the City Engineer determines that high groundwater, slope stability problems, etc. would inhibit or be aggravated by on-site retention, or where retention will provide no benefits for groundwater recharge or erosion control.

(b) Where soils have a permeability rate of two inches per hour or less and on-site percolation is not feasible, runoff should be detained or dispersed over nonerodible vegetated surfaces so that the runoff rate does not exceed the predevelopment level. When the runoff rate must exceed the predevelopment level, the runoff water shall be discharged over nonerodible surfaces or at a velocity that will not erode. On-site detention shall be required by the City Engineer unless the applicant shows that the runoff which is created will not contribute to downstream erosion, flooding, or sedimentation.

(c) Any concentrated runoff which cannot be effectively dispersed over nonerodible channels or conduits to the nearest drainage course shall be contained within on-site percolation devices. Where water will be discharged to

natural ground or channels, appropriate energy dissipators shall be installed to prevent erosion at the point of discharge.

• (d) Runoff from disturbed areas shall be detained or filtered by berms, vegetated filter strips, catch basins, or other means as necessary to prevent the escape of sediment from the disturbed area.

(e) No earth, organic, or construction material shall be deposited in or placed where it may be directly carried into a stream, lake, marsh, slough, lagoon, or body of water.

(f) Where land-disturbing activities are in proximity to lakes or natural watercourses, a buffer zone is required along the land-water margin of sufficient width to confine visible siltation within 25% of the buffer zone nearest the landdisturbing activities.