Alameda County Municipal Code Art. VI Design Standards

Excavations shall be constructed or protected so that they do not endanger life or property.

(Prior gen. code § 7-115.0)

The slope of cut surfaces of permanent excavations shall not be steeper than two horizontal to one vertical exclusive of terraces and exclusive of roundings described herein. Steeper slopes may be permitted in competent bedrock provided such slope inclinations are in accordance with recommendations contained in the geotechnical or geological report. The bedding planes or principal joint sets in any formation when dipping towards the cut face shall not be daylighted by the cut slope unless the soils and geologic investigations contain recommendations for steeper cut slopes. The director of public works may require the excavation to be made with a cut face flatter in slope than two horizontal to one vertical if necessary for stability and safety. Cut slopes shall be rounded into the existing terrain to produce a contoured transition from cut face to natural ground.

(Prior gen. code § 7-115.1)

Fills shall be constructed in layers. The loose thickness of each layer of fill material before compaction shall not exceed eight inches. Completed fills shall be stable masses of well integrated material bonded to adjacent materials and to the materials on which they rest. Fills shall be competent to support anticipated loads and be stable at the design slopes shown on the plans.

Proper drainage and other appropriate measures shall be taken to ensure the continuing integrity of fills. Earth materials shall be used which have no more than minor amounts of organic substances and have no rock or similar irreducible material with a maximum dimension greater than six inches.

(Prior gen. code § 7-115.2)

All fills shall be compacted throughout their full extent to a minimum of ninety (90) percent of maximum density as determined by appropriate ASTM standard method or other alternate methods approved by the director of public works. Tests to determine the density of compacted fills shall be made on the basis of not less than one test for each two foot vertical lift of the fill but not less than one test for each one thousand (1,000) cubic yards of material placed. Additional density tests at a point approximately one foot below the fill slope surface shall be made on the basis of not less than one test for each one thousand (1,000) square feet in slope surface but not less than one test for each ten (10) foot vertical increase of slope height. Additional tests may be required throughout the fill as determined by the inspector for the director of public works. All tests shall be reasonably uniformly distributed within the fill or fill slope surface. Results of such testing and location of tests shall be presented in the periodic and final reports. Compaction may be less than ninety (90) percent of maximum density, as determined by the above test, within six inches of the slope surface when such surface material is placed and compacted by a method acceptable to the director of public works for the planting of the slopes. Compaction of temporary storage fills, to be used for a period of not greater than six months, shall not be required, except where the director of public works determines that compaction is necessary as a safety measure to aid in preventing saturation, sliding, or erosion of the fill. Where compaction is required, it shall be done as specified by the director of public works.

(Prior gen. code § 7-115.3)

(Ord. No. 2010-19, § 1, 5-4-10)

The natural ground surface shall be prepared to receive fill by removing vegetation, noncomplying or undocumented fill, top soil, and other unsuitable material, and where slopes are five horizontal units to one vertical unit or steeper, by benching into competent material in a manner recommended by a geotechnical engineer or an engineering geologist and approved by the director of public works. If a bench or keyway is required under the toe of a fill slope, the said bench or keyway shall be at least ten (10) feet wide, unless otherwise recommended by the geotechnical engineer or engineering geologist.

(Prior gen. code § 7-115.4)

(Ord. No. 2010-19, § 1, 5-4-10)

The slope of permanent fills shall not be steeper than two horizontal to one vertical exclusive of terraces and exclusive of roundings described herein. The director of public works may require that the fill be constructed with an exposed surface flatter than two horizontal to one vertical or may require such other measures as he deems necessary for stability and safety. Fill slopes shall be rounded into existing terrain to produce a contoured transition from fill face to natural ground or to abutting cut or fill surfaces where conditions permit.

(Prior gen. code § 7-115.5)

Footings which may be affected by any excavation shall be underpinned or otherwise protected against settlement and shall be protected against lateral movement. Fills or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by such fill or surcharge. The rights of coterminous owners shall be as set forth in Section 832 of the Civil Code of the state.

(Prior gen. code § 7-115.6)

Existing utility service lines and other facilities on the premises shall be protected against settlement and lateral movement as necessary.

(Ord. No. 2010-19, § 1, 5-4-10)

Unless otherwise recommended in a geotechnical/geological investigation report, or as otherwise specified by the director of public works, the required setbacks of constructed slopes shall be as follows:

A. The setback of an ascending slope from the face of any building or structure, and the setback of a descending slope from the face of any footing or foundation, shall be in accordance with the requirements of Section 1805.3 of the California Building Code.

B. The setback of an ascending slope from a property line shall be equal to at least one-half the vertical height of the slope, but need not be more than fifteen (15) feet.

C. The setback of a descending slope from a property line shall be equal to at least one-fifth the vertical height of the slope, but need not be more than forty (40) feet.

(Prior gen. code § 7-115.7)

(Ord. No. 2010-19, § 1, 5-4-10)

The drainage structures and devices required by this chapter shall be designed and constructed in accordance with standards and criteria authorized by the director of public works.

(Prior gen. code § 7-115.8)

All drainage facilities shall be designed to carry surface and subsurface waters to the county stormdrain system or other juncture, subject to the approval of the director of public works and in accordance with the approved pollution prevention plan. Drainage areas shall conform to patterns established by the director of public works.

(Prior gen. code § 7-115.9)

(Ord. No. 2010-19, § 1, 5-4-10)

Unless otherwise specified by the director of public works, all areas shall be graded and drained so that water will not pond or accumulate. Drainage shall be effected in such a manner that it will not cause erosion or endanger the stability of any cut or fill slope or any building or structure.

(Prior gen. code § 7-115.10)

(Ord. No. 2010-19, § 1, 5-4-10)

When surface drainage is discharged onto any adjoining property, it shall be discharged in such a manner that it will not cause erosion or endanger any cut or fill slope or any building or structure.

(Prior gen. code § 7-115.11)

Terraces at least eight feet in width shall be established at not more than twenty-five (25) feet in height intervals for all cut and fill slopes exceeding thirty (30) feet in height. Where only one terrace is required, it shall be at approximately mid-height. Suitable access shall be provided to permit proper cleaning and maintenance of terraces and terrace drains. Swales or ditches on terraces must be connected by means of down-drains to drainage outlets or other discharge points.

Berms, interceptor drains, swales, or other protective devices shall be installed at the top of cut and fill slopes to protect the face of the slope from erosion caused by surface runoff.

The design of all such terrace drains, swales, ditches, down-drains, outlets, discharge points, berms, and other protective devices shall be subject to approval by the director of public works.

(Prior gen. code § 7-115.12)

(Ord. No. 2010-19, § 1, 5-4-10)

Cut and fill slopes shall be provided with subsurface drainage as necessary for stability.

(Prior gen. code § 7-115.13)

The following shall apply to the control of erosion and sediment from grading operations:

A. Grading plans shall be designed with long-term erosion and sediment control as a primary consideration.

B. No grading operations shall be conducted during the rainy season except upon a clear demonstration, to the satisfaction of the director of public works, that at no stage of the work will there be any substantial risk of increased sediment discharge from the site. In the event that rainy season grading is planned, the director shall have the authority to require the submittal of detailed erosion and sediment control plans covering each stage of the work.

C. Should grading be permitted during the rainy season, the smallest practicable area of erodible land shall be exposed at any one time during grading operations and the time of exposure shall be minimized.

D. Natural features, including vegetation, terrain, watercourses and similar resources shall be preserved wherever possible. Limits of grading shall be clearly defined and marked to prevent damage by construction equipment.

E. Permanent vegetation and structures for erosion and sediment control shall be installed as soon as possible after the completion of grading or construction activities.

F. Adequate provision shall be made for long-term maintenance of permanent erosion and sediment control structures and vegetation.

G. No topsoil shall be removed from the site unless otherwise directed or approved by the director of public works. Topsoil overburden shall be stockpiled and redistributed within the graded area after rough grading to provide a suitable base for seeding and planting. Runoff from the stockpiled area shall be controlled to prevent erosion and resultant sedimentation of receiving water.

H. Long-term post-grading stormwater runoff from the site may be subject to formal erosion and sedimentation control or other discharge controls in accordance with the provisions of Chapter 13.08 of the general ordinance code. In any case, post construction runoff shall not be discharged from the site in quantities or at velocities greater than the pre-grading volume or flow rate except into drainage facilities that are designed and constructed to receive such increased runoff, as approved by the director of public works.

I. Permittee shall take reasonable precautions to ensure that vehicles do not track or spill earth materials into public roadways and shall immediately remove such materials if this occurs.

J. The permittee shall ensure that erosion and sediment control best management practices (BMPs) as specified in the pollution prevention plan are applied throughout the project in order to control contamination of stormwater runoff and to capture any soil that is eroded.

(Prior gen. code § 7-115.14)

(Ord. No. 2010-19, § 1, 5-4-10)

Should increased sediment discharge occur or become imminent, permittee shall take all necessary steps to control such illicit discharge. Such steps may include construction of additional facilities or removal or alteration of facilities required by approved erosion and sediment control plans. Facilities removed or altered shall be restored as soon as possible afterward or appropriate changes in the plan shall be immediately requested pursuant to this chapter. Permittee shall take prompt action to resolve emergency problems; in the event that the permittee fails to respond, or the response is deemed inadequate, the director of public works shall have the authority to institute abatement proceedings or to take other enforcement actions in accordance with the provisions of Section 15.36.680 of this chapter.

(Prior gen. code § 7-115.15)

(Ord. No. 2010-19, § 1, 5-4-10)

Erosion and sediment control plans prepared pursuant to this chapter shall comply with all of the following:

A. The erosion and sediment control plan need not be a separate sheet if all facilities and measures can be shown on the grading sheets or included in the pollution prevention plan without obscuring the clarity of any of the plans.

B. An erosion and sediment control plan shall be required whenever:

1. The graded portion of the site includes more than ten thousand (10,000) square feet of area having a slope greater than five percent; or

2. There is a significant risk that more than two thousand five hundred (2,500) square feet will be unprotected or inadequately protected from erosion during any portion of the rainy season; or

3. Grading will occur within the watercourse setback, as defined in Section 13.12.320 of Chapter 13.12 of the general ordinance code; or

4. Grading will occur in proximity to the property line(s) in a location where there is a potential erosion or sediment discharge hazard to the adjacent property; or

5. The applicant is required to prepare and implement a Storm Water Pollution Prevention Plan (SWPPP) in accordance with the provisions of the State Construction General Permit.

6. The director of public works determines that the grading will or may pose a significant erosion or sediment discharge hazard because of the erosion potential of the particular soil type, the sensitivity of the receiving waterbody, the proximity of the receiving waterbody, the slope of the site, or for any other relevant reason.

C. The applicant shall submit, with his erosion and sediment control plans, a detailed cost estimate covering this work.

D. Erosion and sediment control plans shall include an effective revegetation program to stabilize all disturbed areas that will not be otherwise protected. All such areas where grading has been completed between May 1st and September 15th shall be planted by October 1st. Graded areas completed at other times of the year shall be planted within fifteen (15) days. If revegetation is infeasible or cannot be expected to stabilize an erodible area with assurance during any part of the rainy season and the unstable area exceeds two thousand five hundred (2,500) square feet, additional erosion and sediment control measures or irrigation of planted slopes may be required as appropriate to prevent increased sediment discharge.

E. Erosion and sediment control plans shall be designed to prevent increased discharge of sediment at all stages of grading and development from initial disturbance of the ground to project completion. Permanent post-grading control of erosion and sedimentation may also be required in accordance with the provisions of Chapter 13.08 of the general ordinance code. If grading occurs in distinct phases, or if the site will remain unstable through more than one rainy season, the plan must specifically cover each stage of the development. Plans shall indicate the implementation period and the corresponding state of construction where applicable.

F. Erosion and sediment control plans shall comply with the recommendations of any civil engineer, geotechnical engineer, geologist, engineering geologist, or landscape architect involved in preparation of the grading plans.

G. The structural and hydraulic adequacy of all stormwater containment or conveyance facilities shown on the erosion and sediment control plans shall be verified by a civil engineer, and he shall so attest on the plans. Sufficient calculations and supporting material to demonstrate such adequacy shall accompany the plans when submitted.

H. Erosion and sediment control plans shall be designed with sufficient flexibility to meet unanticipated field conditions.

I. Erosion and sediment control plans shall provide for inspection and repair of all erosion and sediment control facilities at the close of each working day during the rainy season and for specific sediment cleanout and vegetation maintenance criteria.

J. Erosion and sediment control plans shall comply with any and all standards and specifications adopted by the director of public works for the control of erosion and sedimentation on grading sites.

K. Erosion and sediment control plans prepared in conjunction with a formal stormwater pollution prevention plan (SWPPP) shall include detailed cross-reference to each element of the SWPPP, including the planned best management practices (BMP's) and descriptions of the required monitoring programs.

The director of public works may waive the requirement for a formal erosion and sediment control plan if, in his/her opinion, no significant erosion or sediment discharge hazard exists; however, all grading projects shall be required as a minimum to provide site and seasonally relevant erosion and sediment control best management practices (BMPs) as part of the pollution prevention plan required by the provisions of Section 15.36.230 of this Chapter 15.36.

(Prior gen. code § 7-115.16)

(Ord. No. 2010-19, § 1, 5-4-10)

A. Except as otherwise allowed under the provisions of Section 15.36.640 of this chapter, the grading of vehicular ways shall conform to the general grading requirements of this chapter.

B. All vehicular ways shall be graded in conformance with the slope, width, and turn radii limitations imposed by the county fire department or by the applicable fire district.

(Prior gen. code § 7-115.17)

(Ord. No. 2010-19, § 1, 5-4-10)

The director of public works may approve grading for a vehicular way where an adjacent cut slope is steeper than two horizontal units to one vertical units (fifty (50) percent slope) if all of the following are met:

A. The daylight line of a plane sloping at two horizontal units to one vertical unit from the toe of the said slope is more than twenty (20) feet from any property line and from the face of any building or structure; and

B. The steeper slope is necessary to avoid excessive grading; and

C. The proposed vehicular way and adjacent cut slopes are located outside of any designated landslide hazard zone, or they are deemed safe following a geotechnical/geologic investigation by a geotechnical engineer or an engineering geologist; and

D. If required by the director of public works, the property owner executes and records a hold harmless agreement, in a form approved by the director, relieving the county from any liability for this exception.

(Prior gen. code § 7-115.18)

(Ord. No. 2010-19, § 1, 5-4-10)

Vehicular ways shall be graded and drained in such a manner that the stormwater runoff from the finished construction will not cause erosion, endanger the stability of any adjacent slope, or damage any buildings, structures, or adjacent property. Moreover, the discharge of runoff from a vehicular way may be subject to the stormwater quality and flow/volume limitations imposed by Chapter 13.08 of the general ordinance code.

(Prior gen. code § 7-115.19)

(Ord. No. 2010-19, § 1, 5-4-10)

Grading work shall not be permitted within any area designated as a floodplain in accordance with the provisions of Chapter 15.40 of this title, except as approved by the director of public works in accordance with the provisions of that chapter.

(Ord. No. 2010-19, § 1, 5-4-10)