19-6 HILLSIDE GRADING. — Danville Zoning Code

19-6.1 Location and Character of Development. ¶

a. Development in the Town should be concentrated on relatively level areas (Slope Zones 1 and 2). Visually prominent hillsides shall be developed in accordance with the Scenic Hillside and Major Ridgeline Development (Ordinance #29-84).[1]

Additionally, as slope steepness increases, architectural innovation shall be utilized rather than extensive grading so that the natural landform is disturbed to the least extent possible.

The following shall serve as a guide within a particular slope zone with the exception that, where approved by the Planning Commission or Town Council, the guidelines for one zone may be applied to limited portions of an adjacent zone to permit the extension or transition of a logical design concept. This guideline will not preclude satisfying requirements for fire apparatus access roads.

b. The “Percent Natural Slope” on a site will be calculated as the average gradient of the entire site unless one (1) of the following conditions exist:

The “Percent Natural Slope” existing on sixty (60%) percent or more of the entire site falls within a more restrictive slope zone, or
The “Percent Natural slope” existing within forty (40%) percent or more of the proposed pad area falls within a more restrictive slope zone, then the more restrictive guidelines will apply.

c. Development Guidelines for Natural Slopes .

*Slope* *Zone*	*Percent Natural Slope*	*Location Character Guideline*
1.	Less than 10% (10 horizontal to 1 vertical)	This is not a hillside condition. Mass grading with conventional fully padded lots and terracing are acceptable.
2.	10%-19.9% Hillside Grading (maximum 5 horizontal to 1 vertical)	Development with mass grading may occur in this zone, but existing landforms must retain their natural character. Padded building sites are permitted on these slopes, but split level architectural structures with stacking and clustering are preferred. A cut and fill map is required to verify maximum heights of cut and fill.
3.	20%-33% Hillside Grading (maximum 3 horizontal to 1 vertical)	Special hillside architectural and design techniques are required within Zone 3. Architectural designs are to conform to the natural landform. Mass grading is discouraged except on a case-by-case basis as permitted by the Planning Commission. Mass grading is particularly discouraged where development is proposed within a high risk landslide area. This guideline does not preclude any grading necessary to mitigate the slide hazard. A cut and fill map is required to verify maximum heights of cut and fill.

4.	34% or Greater Hillside Grading (greater than 3 horizontal to 1 vertical)	Development will not normally be approved within this zone, except for less visually prominent slopes as identified in the Town’s Scenic Hillside and Major Ridgeline Development Ordinance 29-84,1and then only in areas where it can be clearly demonstrated that safety, environmental and aesthetic impacts will be minimized. Only limited grading shall be allowed. This guideline does not preclude any grading necessary to mitigate the slide hazard. A Conditional Use Permit is required. A cut and fill map is required to verify maximum heights of cut and fill.

d. Precise identification of major and minor ridgelines is to be completed by the Planning Department during the development review process in accordance with the Scenic Hillside and Major Ridgeline Development Ordinance 29-84,[1] Where this chapter may conflict with Ordinance 29-84,[1] Ordinance 29-84[1] takes precedence, Hillside grading shall conform to Section 8-5011 (Map) in Ordinance 29-84.[1] Ridgeline areas of major significance should be left undisturbed or the development shall conform to Ordinance 29-84.[1] Development of ridgelines not addressed in Ordinance 29-84[1] and of minor significance is permitted where the natural profile can be retained with no abrupt changes in grade and where development and attendant improvements are least visible from other developments (existing and future) and roads below. Ridge-lines not identified as “significant” during the development review process may be developed as appropriate in accordance with other applicable development guidelines.

(Ord. #89-22, §92-8.40)

1 Editor’s Note: Ordinance #29-84, Scenic Hillside and Major Ridgeline Development, is codified as Section 32-25 of Chapter XXXII, Planning and Land Use.

Notes

1 1 Editor’s Note: Ord. #29-84 is codified as Section 32-35 of Chapter XXXII, Planning and Land Use.

19-6.2 Grading. ¶

Grading and its potentially adverse effects on hillside areas (Slope Zones 2-4) shall be minimized by:

a. Requiring revegetation of engineered slopes according to guidelines established by the Planning and Building Departments.

b. Requiring that manufactured slopes be graded no steeper than a slope of three (3’) feet horizontal to one (1’) foot vertical. Slopes less than ten (10’) feet in height may be graded to a slope of two (2’) feet horizontal to one (1’) foot vertical in accordance with recommendations provided in the approved soils report unless approved in writing by the Town Engineer.

c. Requiring that all engineered slopes within Slope Zones 2-4 be contour graded to achieve a natural appearance. Borders of cut slopes and fills are to be rounded to blend with the existing terrain.

d. Requiring road and utility construction in accordance with approved plans and prohibiting grading until improvement plans have been approved for the area.

e. Requiring grading plans to include mitigating measures in accordance with the approved soils report that will reduce underground water seepage problems which may occur because of increased irrigation or alteration of the natural contours to acceptable safety levels.

f. Requiring that grading plans be submitted for approval in accordance with the provisions of the Scenic Hillside and Major Ridgeline Development Ordinance 29.841 and this chapter.

(Ord. #89-22, §92-8.41)

19-6.3 Landscaping/Slope Stabilization. ¶

a. Grading shall preserve existing areas of vegetation identified as “significant” at the development review level. Trees identified as “significant” shall be preserved as required by the Tree Ordinance.

b. New landscape materials introduced as transition planting shall be used to integrate the manmade and natural environments, to screen and soften the visual impact of development and to provide privacy between project and existing adjacent developments. Landscape materials shall also provide diversity within the developed areas. Plan materials shall be chosen from “Water Conserving Plants and Landscapes for the Bay Area”, published by the East Bay Municipal Utility District. Temporary irrigation systems will be required only where necessary to establish plant materials.

c. All cut and fill slopes shall be planted in accordance with an erosion-control plan approved by the Town Engineer.

d. Landscape and irrigation plans shall be submitted for approval in accordance with the provisions of the Hillside Development Overlay District.

(Ord. #89-22, §92-8.42)

19-6.4 Drainage. ¶

a. Interceptor ditches shall be established above all cut or fill slopes, where required by the Town Engineer, and the intercepted water conveyed to a stable channel or natural drainage-way with adequate capacity.

b. Natural drainageways shall be protected from erosion caused by artificially concentrated flows introduced into the stream bed. Protection for inlet and outlet structures shall take the form of riprap with filter fabric or other stabilization measures as reviewed and approved by the Town Engineer.

(Ord. #89-22, §92-8.43)

19-6.5 Roadways. ¶

a. Grading for roadways in Slope Zones 2, 3 and 4 should have slopes rounded to blend with the natural topography. Manufactured slopes shall be landscaped in accordance with the Town’s landscape guidelines.

(Ord. #89-22, §92-8.46)