It is the purpose of this section to quantify methods by which the overall shape, height and grade of any cut or fill slopes may be developed, such that they are responsive and suitable with respect to the existing natural terrain of a particular site. Interpretations of any standards herein will be subject to the review and final decision of the appropriate discretionary review body for concept plans.
(a)
General Design Standards. All cut and fill slopes shall conform to the following standards:
(1)
All cut and fill slopes in excess of five feet vertical height shall be rounded with vertical curves from the crest of the slope and from any surface drains constructed on the face or top of the slope and must keep concentrated water from roofs, drives or pads from going over slopes or onto properties;
(2)
Where two cut or fill slopes intersect, the ends of each slope shall be horizontally rounded and blended with a minimum radius of twenty-five feet. A smaller radius may be permissible for short slope lengths;
(3)
Where a cut or fill slope intersects a natural slope, the horizontal contours of the slope shall be curved so as to blend with the natural slope;
(4)
Where any cut or fill slopes exceed seventy feet in horizontal length, the horizontal contours of the slope shall be curved in a continuous undulating fashion with radii no greater than three hundred feet. Alternate designs may be considered with approval of the design review board;
(5)
The top and toe of each slope in excess of ten feet vertical height, excepting the toe of any slope within twenty-five feet of a dwelling, shall be vertically rounded with radii no less than five feet and designed in proportion to the total height of the slope. This shall not apply to the toe of any cut slope which is supported by a retaining wall;
(6)
Slope stabilization measures shall be prepared and approved for all slopes. These include, but are not limited to, professional identification, analysis and recommendations for cleanouts, keyways, benching, buttressing, subdrainage, blending of earth materials and identification of competent materials. Both gross and surficial stability shall be considered;
(7)
No cut for fill slope shall exceed twenty-five feet vertical height.
Exception. Grading for foundation retaining walls on structures or designs which incorporate alternate solutions such as retaining or crib walls may exceed the height limit if approved by the design review board; |
(8)
Remedial, reconstructive and repair grading may exceed the twenty-five foot slope height limit if the preexisting artificial slope likewise exceeded such height.
(b)
Design Standards For Cut Slopes.
(1)
Maximum Slope. No excavation shall be made with a cut face steeper in slope than two horizontal to one vertical, unless said cut face is to be immediately supported with a retaining wall or other approved support for which a building permit has been obtained. Said retaining walls shall not exceed five feet maximum height. The appearance of the retaining walls shall be subject to the approval of the design review board.
(2)
Exception.
(A)
Less Than Two to One (2:1) Slope. Where the city determines that a less steep slope is necessary in order to ensure the stability of the excavation and general safety, it may require a cut slope less steep than two horizontal to one vertical.
(B)
Greater Than Two to One (2:1) Slope. When the engineering geologist certifies in his report that the site has been investigated and in his opinion the material in cut areas will be stable, resistant to erosion and free from hazardous rock fall if cut to a steeper slope, the city may permit a cut slope steeper than two horizontal to one vertical subject to such conditions as it may require. The city may waive the requirement for an engineering geologic report in grading of individual building sites where conditions are favorable. Such slopes may not exceed five feet in vertical height.
(c)
Design Standards For Fills.
(1)
Maximum Slope. No fill shall be made which creates any surface steeper than two horizontal to one vertical.
(2)
Exception. Less than two to one (2:1) slope. Where the soil conditions are such that, in the opinion of the city, a less steep slope is necessary in order to ensure the stability of the fill, to prevent damaging erosion, or to ensure the general safety, it may require a fill slope less steep than two horizontal to one vertical.
(3)
Compaction Required. All fills shall be compacted to a minimum of ninety percent of maximum density as determined by the prevailing standards contained in Chapter 70 of the Uniform Building Code, latest edition. Where lower density and expansive types of soil exist, permission for lesser compaction may be granted by the city upon showing of good cause in a soils engineering report. Fill shall be placed in layers not exceeding 0.67 feet (eight inches) thick before compaction unless deviation is approved in writing by the soils engineer. Fill slopes placed for the purpose of landscaping which are not compacted shall not exceed four horizontal to one vertical.
(4)
Preparation of Ground. The natural ground surface shall be prepared to receive fill by removing vegetation, noncomplying fill, noncomplying top soil and, where natural slopes are five horizontal to one vertical or steeper, by bedding into sound bedrock or other competent material. All fill keys and cleanouts shall be inspected by a registered engineering geologist or registered soils engineer.
(5)
Fill Material. No organic material shall be permitted in fills. No rock or similar irreducible material with a maximum diameter greater than eight inches shall be buried or placed in fills without proper disposition and compaction as directed by the soils engineer.
(6)
Slopes to Receive Fill. Fills toeing out on natural slopes which are steeper than two horizontal to one vertical will not be permitted unless stability is substantiated by geological and soils engineering investigation and report.
(d)
Design Standards For Cut And Fill Setbacks. Cuts and fills shall generally be set back from property lines in accordance with Chapter 70 of the Uniform Building Code unless site-specific engineering design and evaluation justifies a lesser setback. Fill placed on or above the top of an existing or proposed cut or natural slope steeper than three horizontal to one vertical shall be set back from the edge of the slope a minimum of six feet unless stability is substantiated by a soils engineer.
(e)
Design Standards For Drainage.
(1)
Disposal. All drainage facilities shall be designed to carry surface waters to the nearest practical street, storm drain or natural watercourse approved by the city and/or other appropriate governmental agency, as a proper place to deposit such waters. Where disposal is into a natural watercourse, the city engineer shall determine if a dissipator is required. Whenever geotechnical, engineering and/or terrain considerations are favorable, on-site detention of storm runoff to predevelopment levels should be implemented.
All plans shall show adequate provisions for the conveyance of runoff from and through the project site.
(2)
Building Pad Drainage. Each building pad at or above street level shall drain directly to the street and shall be graded at a slope at least two percent perpendicular to the street from which the pad has its driveway access.
(3)
Erosion Prevention. Adequate provision shall be made to prevent any surface waters from damaging the face of an excavation or fill. All slopes shall be protected from surface runoff from above by berms or paved interceptor ditches according to city standards.
(4)
Storm Drains. Storm drains for conveying water which does not originate on the surface of the cut or fill slope shall not be constructed in any cut or fill slope where an alternate route for said storm drain is available.
(f)
Design Standards For Erosion and Sediment Control.
(1)
All construction projects, regardless of size, are required to implement an effective combination of best management practices (BMPs) to prevent a condition of accelerated erosion, a prohibited discharge or pollutant that causes a condition of contamination.
(2)
A construction project erosion and sediment control plan is required for all projects that will disturb more than twenty cubic yards of soil, or is required by the building official to provide adequate BMP protection.
(3)
At a minimum the following types of best management practices (BMPs), as defined in the city's jurisdictional urban runoff management plan (JURMP) and in Title 16—"Water Quality Control" Ordinance, or their equivalent, shall be required during all phases of construction project activity, as applicable:
Erosion prevention;
(i)
Seasonal restrictions on grading;
(ii)
Slope stabilization requirements;
(iii)
Phased grading;
(iv)
Revegetation as early as feasible;
(v)
Preservation of natural hydrological features;
(vi)
Preservation of riparian buffers and corridors;
(vii)
Maintenance of all source control and structural treatment BMPs; and
(viii)
Retention and proper management of sediment and other construction pollutants on site.
(4)
Construction projects that are covered under the state water resources control board's "general construction permit" shall comply with the conditions of such permit, including the storm water pollution prevention plan, and all applicable city BMP requirements as specified in the city's Municipal Code.
(Ord. 1237 § 1, 1992; Ord. 1442 § 2, 2004)