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City of San Mateo Municipal Code.


(a) Standards Generally. All grading and grading operations shall comply with the requirements set forth in this Section in addition to other requirements of this Code.

(b) Hours of Operation. All grading operations shall be restricted to weekdays between the hours of seven a.m. and seven p.m., unless the Director of Public Works finds evidence that an emergency exists which would imperil or inconvenience the public, in which case he or she may permit the work to proceed during such other hours as may be necessary.

(c) Slopes.

(1) Vacant Parcels. In evaluating the reasonableness of construction, the reviewing authority may consider, in addition to other factors set forth in this chapter, the amount of cut and fill, steepness of driveway, removal of major vegetation, height, bulk and visibility of proposed structures, preservation of natural topographic landforms, and compatibility with the pattern and scale of development within the surrounding neighborhood.

(2) Subdivisions. Subdivisions of sloped properties are limited by San Mateo Municipal Code Chapter 26.20—Lots (Subdivision Code).

(3) Limits of Hillside Grading. In R1 and R2 zones, grading on slopes of 25 percent or more shall be limited to site access (driveway) and to building foundations. In all other zoning districts, grading on slopes of 25 percent or more shall be limited to site access only. In all cases, grading shall be designed to limit alteration of the visual character and topography of the hillside while permitting creation of a reasonable building site.

(4) Finished Cuts of Slopes. The exposed or finished cuts or slopes of any fill or excavation shall be smoothly graded and blended with existing contours by rounding off cut or fill edges and shall be screened with vegetation, and no such fill, slope, cut or inclined graded surface shall exceed a vertical height of thirty feet unless intercepting drains or terraces are provided. Such drains or terraces shall be permanently lined or protected with materials approved by the Director of Public Works and accumulating surface waters shall be conducted to an approved point of discharge. Any such terrace or intercepting drain shall be designed to prevent overflow which may cause erosion. All exposed slopes of any cut or fill subject to erosion shall be protected by approved planting, crib walls, walls and planting, terracing, or a combination thereof. The use of visible retaining walls shall be minimized, and where visible, shall be screened with vegetation. Graded surfaces exceeding an area of five thousand square feet shall be treated as provided in Section 23.40.050(j). The Director of Public Works may require that corrective measures be taken if he or she finds the material being cut or used for fill is unusually subject to erosion, or if other conditions affect the stability of the slopes.

(5) Seasonal Grading. All grading shall be limited to the dry season (April 15 through October 15) unless the Director of Public Works determines adequate erosion control is provided. For commencement of grading during the wet season, the permittee shall demonstrate that grading is relatively minor and that erosion and sedimentation can be controlled. The Director of Public Works shall have the ability to grant or deny permission under this Section on the basis of weather forecasts, experience, and other pertinent factors.

(d) Dust and Dirt. All graded surfaces of any nature shall be wetted, or otherwise suitably contained to prevent nuisance from dust or spillage on city streets or adjacent properties. Equipment, materials and roadways on the site shall be used in a manner or treated as to prevent excessive dust conditions. Dust and dirt control activities shall not result in any material entering the storm drain system.

(e) Fill Material. All fill shall be earth, rock or other inert mineral materials free from organic material and free from metal, except that topsoil spread on cut and fill surfaces may incorporate humus for desirable moisture retention properties.

(f) Drainage. Adequate provision shall be made to prevent any surface waters from damaging the cut face of an excavation or any portion of a fill. All drainage ways and structures shall carry surface waters to the nearest street, storm drain or natural watercourse capable of receiving them without producing erosion as approved by the Director of Public Works as a safe place to deposit and receive such waters. Parcels shall not be graded so as to direct additional water, or to alter the existing pattern of drainage, onto adjacent properties. The Director of Public Works may require such drainage structures to be constructed, or installed, as are necessary to prevent erosion damage, or to prevent saturation of the fill or material behind cut slopes.

(g) Street and Driveway Grades.

(1) Maximum Grades. Maximum grades for new streets and driveways shall be as follows:

(A) Collector and Local Streets: 15%

(B) Intersections: 8%

(C) Private Roads, Driveways and Ramps that have no pedestrian access and are not emergency vehicle access easements: 18%

(2) Design. Streets and driveways shall be designed in accordance with standard engineering practices by a registered civil engineer. Design of any street or driveway shall demonstrate consideration of such factors as surrounding topography, drainage, pedestrian access, the presence of intersections, driveways, and/or bicycle lanes, vehicular volume and type, and vehicular operation. The flattest grade that reasonably fits the topography should be used and appropriate transitions (vertical curves) between changes in grade are required.

(h) Backfilling. Any pipe trench or other trenching or excavation made in any slope of an excavated or filled site shall be backfilled to the level of the surrounding grade. Such backfill shall be compacted to the original density of the excavated materials, but in no case less than ninety (90%) percent of the maximum density achieved by an AASHO soil compaction test method, selected by the Director of Public Works. Suitable check drains to control erosion shall be installed as directed by the Director of Public Works.

(i) Compaction of Fill. all fills intended to support buildings, structures, or where otherwise required to be compacted for stability of material, shall be compacted, inspected and tested in accordance with adopted specifications on file in the office of the Director of Public Works.

(j) Erosion Control—Landscaping. All cut and fill surfaces created by a grading process, agricultural processes excepted, shall be planted with a ground cover that is acceptable to a soils engineer and compatible with ground covers in general use in the area, and is one that will thrive with little or no maintenance once established. Topsoils are to be stockpiled during rough grading and used on cut and fill slopes to a depth sufficient to support the proposed plant materials in a manner acceptable to a soils engineer. On slopes likely to be extensively disturbed by later construction, an interim ground cover may be planted or emplaced to be supplemented by the permanent ground cover and/or shrubs and trees when the site is finally developed and landscaped. When slopes have been permitted too steep to support continuous ground cover, and in lieu thereof niches and ledges have been provided for planting, such slopes need not be planted with a continuous ground cover, but may instead be screened with vines and plantings. Cuts and fills along public roads may be required to be landscaped and graded so as to blend into the natural surroundings. All plant materials shall be satisfactory to the superintendent of parks and/or Director of Public Works.

(k) Special Precautions.

(1) If, at any stage of the grading, the Director of Public Works determines by inspection that the nature of the earth formation is such that further work as authorized by an existing permit is likely to imperil any property, public way, watercourse or drainage structure, he or she may require, as a condition to allowing the work to proceed, that such reasonable safety precautions be taken as he or she considers advisable to avoid likelihood of such peril. "Special precautions" may include, but shall not be limited to, specifying a flatter exposed slope, construction of additional drainage facilities, berms, terracing, compaction, or cribbing, installation of plant materials for erosion control, or implementation of other relevant BMPs: and reports of a registered soils engineer and/or of a registered engineering geologist whose recommendations may be made requirements for further work.

(2) Where it appears that storm damage may result because the grading is not complete, work may be stopped and the permittee required to install temporary planting or otherwise to control erosion, install temporary structures or take such other measures as may be required to protect adjoining property or the public safety. On large operations or where unusual site conditions prevail, the Director of Public Works may specify the time of starting grading and time of completion, or may require that the operation be conducted in specific stages so as to insure completion of protective measures or devices prior to the advent of seasonal rains.