(a) A soil erosion control plan must be submitted for all proposed development within a geologically similar area. Except for items that are expressly waived by the director, the plan must:
(1) show the type of soil cover as mapped by the Soil Conservation Service and confirmed by representative field tests and samples;
(2) indicate the susceptibility to erosion of the mapped soils as confirmed by representative field tests and samples;
(3) show the location of existing and proposed development;
(4) include a timing schedule indicating starting and completion dates of the development activities sequence and the time of exposure of each area prior to completion of control measures;
(5) contain a complete description of all measures to be taken to prevent or control erosion and sedimentation of soils during and after construction;
(6) comply with best management practices standards for storm water pollution prevention plans; and
(7) be certified by a registered professional engineer.
(b) Development within a geologically similar area must conform to the following performance standards:
(1) Development must be fitted to the topography and soils to minimize cut and fill sections.
(2) Grading is not permitted within the one-percent annual chance flood plain boundaries of watercourses unless it is:
(A) in conjunction with the construction of approved drainage facilities; or
(B) authorized by a city council approved fill permit. All grading must comply with Section 51A-5.207 of this division.
(3) Indigenous vegetation must be retained and protected except in immediate areas of development so that a minimal amount of vegetation is removed or replaced. If vegetation is removed, it must be replaced with new vegetation of the same variety unless the building official approves an alternative variety as being less susceptible to disease or better suited for urban development.
(4) Development must be accomplished in a manner which assures that as small an area as possible is exposed to erosion at any one time. When land is exposed during development, the exposure must be kept to the shortest practical period of time not to exceed six months. In extraordinary cases, an extension of the six month time period may be granted in writing by the director. In such cases the director shall seek and consider the recommendation of the escarpment area review committee before making his decision.
(5) Areas where construction activities have ceased for more than 21 days must be stabilized by the developer to minimize erosion through the use of temporary or permanent vegetation, mulching, sod, geotextiles, or similar measures. In cases where permanent measures are not installed, the developer must maintain the temporary measures until the site is either fully developed or permanent vegetation with a density of at least 70 percent of the native background vegetative cover for the area has been installed.
(6) Sediment basins or other installations approved by the director must be installed and maintained to remove sediment from runoff waters accumulating on land undergoing development. These installations should be returned to natural conditions upon the substantial completion of improvements or when the director determines that the installations are no longer needed. In any event, the owner shall cause these installations to be returned to natural conditions within 90 days after written notice to do so is given by the director.
(7) Runoff caused by changed soil and surface conditions during and after development, both above and below the escarpment zone, must be controlled on each development site within approved drainage facilities so that the runoff velocity leaving the site is maintained at or below predevelopment rates. Site-specific erosion control is required below the escarpment zone where the erosion control plan shows detrimental erosion caused by runoff velocities.
(8) When additional storm water runoff is being discharged onto the face of the escarpment, the property owner’s engineer shall provide an analysis of whether the additional storm water runoff has a negative effect on the escarpment. If the additional storm water runoff has a negative effect, then detention is required.
(9) Stormwater drainage may not be discharged over the escarpment face at eroding velocities as those velocities are defined in the soil evaluation reports. In no event may the discharge exceed a velocity greater than three feet per second. Stormwater drainage discharge must comply with Section 51A-5.207 of this division.
(10) Temporary vegetation and mulching must be used to protect areas exposed during development. Permanent vegetation must be established on disturbed areas following development in accordance with the vegetation plan required under Section 51A-5.208 of this division.
(11) Channel velocities may not exceed five feet per second, except that velocities higher than five feet per second may be maintained at up to predevelopment rates in the escarpment and chalk zones if the developer establishes to the satisfaction of the director that these velocities do not produce detrimental erosion. If damaging erosion is occurring, site-specific erosion control measures are required. Energy dissipators, if required, must be approved by the director to maintain channel velocities at acceptable levels. (Ord. Nos. 19455; 26000; 30893; 31314)