The following objective development and design standards shall apply to new development in the HRD overlay zone:
(A) Fire management. Projects must comply with the town’s Fire Code.
(B) Geologic hazards. Construction shall not be permitted on identified seismic or geologic hazard areas such as on slides, on natural springs, or on identified fault zones, without approval from the town engineer, based on acceptable soils and geologic reports. Development shall be prohibited in areas determined by the Town Engineer to be geotechnically unstable based on a report by a licensed soils engineer where the Planning Commission determines that the corrective work would be inconsistent with the purpose and the intent of this chapter.
(C) Topographical.
(1) Graded slopes shall be sculptured and contoured to blend with natural terrain. Cuts and fills shall not exceed one foot or rise for each one and one-half feet of run without the approval of the Town Engineer.
(2) The grading plan shall include preventative measures to reduce dust generation, protection of trees and other significant natural features.
(3) Retaining structures shall be shown in plan and elevation. Height of retaining structures shall be minimized. Planting and choice of materials shall be used to visually integrate the structures with natural surroundings.
(4) Grading plans shall include erosion control and revegetation programs. Where erosion potential exists, silt traps or other engineering solutions may be required. The timing of grading and construction shall be controlled by the Town Engineer or other staff designated by the Town Engineer to avoid failure during construction. No initial grading shall be done during the rainy season, from October 1 through April 1.
(D) Ecological. Projects shall be designed to minimize disruption of existing ecosystems. Removal,
changes or construction which will destroy important or rare vegetation and/or wildlife habitats shall be avoided.
(1) Removal of any tree, as the term is defined in § 8.28.020, shall be subject to issuance of a tree removal permit as required by Chapter 8.28 of this code.
(2) In areas of diverse wildlife habitat as delineated on the General Plan Wildlife Habitat and Diversity Map, disruption of trees, shrubs and natural vegetative cover shall be minimized.
(3) No development is permitted 50 feet either side of high water centerline measured perpendicular to the high-water mark away from the centerline. Water quality and natural conditions shall be maintained.
(E) Landscaping. Landscaping shall minimally disturb natural areas and shall be compatible with native plant settings. Where appropriate use is determined by the Planning Commission, fire-resistant and drought-resistant species shall be utilized. Planting shall not obstruct views or alter solar energy access of nearby properties.
(1) A landscape documentation package shall be provided with the development application that complies with the standards of the Model Water Efficient Landscape Ordinance which applies to all new residential development with 500 square feet or more of landscape area. If the total landscaped area is 2,500 square feet or less, an applicant may use the prescriptive compliance option provided in Appendix D of the Model Ordinance to streamline the review process. Under this option, turf shall not exceed 25 percent of the landscape area.
(2) No fill, grading, or construction shall be permitted within the dripline of any existing tree designated for preservation except as may be recommended by an arborist certified by the International Society of Arboriculture or a California-registered professional forester.
(F) Circulation.
(1) Roads shall be designed to meet the requirements of the Town Engineer, as set forth in the Subdivision Ordinance, and the Fire Department as set forth in the Fire Code.
(2) The Planning Commission may require parking areas to accommodate public and guest parking in addition to off-street parking for dwelling units.
(3) Off-street parking shall conform to the provisions of Chapter 17.052 of this title.
(G) Design. Projects shall be designed to meet the criteria set forth in § 17.020.040 of this title.
(H) Low impact clustered development option. In order to enable the creation of permanent open space that will connect or expand existing open space, create wildlife corridors,and preserve habitat for endangered species, the Planning Commission may approve a low impact clustered residential development in an HRD overlay zone on sites greater than one acre with an average slope greater than 15 percent that are identified in the General Plan Housing Element for housing development, subject to design review and the following standards:
(1) Maximum density. The maximum number of units (MN) shall be determined by a slope density formula as follows, unless a different density is set in the General Plan or the applicable base zone:
MN = Development site area (sg. ft.) divided by (10,000 plus 1,200 for each one percent increase in the average slope of the site above 15 percent).
(2) Minimum lot size. The Planning Commission may approve lots that are less than the minimum lot size and dimensions that otherwise would be required by the base zoning district or overlay zone, provided that the overall density does not exceed the General Plan maximum for the site.
(3) Gross building square footage. The maximum permitted gross building area for habitable space is limited to 3,500 sguare feet. Any garage space that exceeds 500 square feet shall be counted as habitable space.
(4) Street layout. All new public streets and private streets shall meet the standards of § 16.24.040, with the following modifications:
(a) New street and driveway grades shall not exceed 18 percent unless an exception has been approved by the Planning Director and the Director of Public Works to allow street and driveway grades up to 25 percent.
(b) Streets and driveways with slopes over 15 percent shall be a permanent, durable, non-asphalt hardscape surface. Streets and driveways with slopes over 18 percent shall have grooves/scoring for traction.
(c) A transition shall be provided at the street and driveway apron to allow vehicles to safely transition to/from roadways and parking areas.
(5) Emergency access. At least two means of emergency ingress and egress shall be provided to all clustered hillside developments with five or more lots. Existing fire roads providing access to open space areas shall be retained and maintained if this is determined necessary by the Fire Department.
(6) Site layout and building design. All clustered development shall:
(a) Locate development along the lowest portion of the property away from ridgelines, adjacent to existing streets and/or on already disturbed land, to the extent feasible, to protect undeveloped areas;
(b) Use split level building terraces, pier foundations and stepped footings, as appropriate for the proposed building, to reduce grading and visual impacts and break up building mass;
(c) Site buildings with different floor elevations to achieve height variation;
(d) Design roofs with an offset of at least 18 inches, a change in pitch, or a gable every 60 linear feet;
(e) Articulate facades to produce shadows through wall setbacks, recessed openings, porches, verandas, moderate overhangs, decks, balconies, and projecting windows;
(f) Not exceed the minimum roof slope standards of the International Residential Code, as adopted by the town and avoid extended horizontal rooflines exceeding 40 feet; and
(g) Provide at least 200 cubic feet of enclosed, lockable private storage space for each dwelling unit, separate from the space required for off-street parking, with a minimum horizontal dimension of four feet.
(7) Maximum building height. No part of a primary building shall exceed:
(a) Twenty-eight and one-half feet on the upslope of a lot;
(b) Thirty-five feet on the downslope of a lot;
(c) Twenty-four feet within 20 feet of a front property line on an upslope lot; and
(d) Twenty-four feet at a rear setback line, measured to the adjacent natural or finished grade, whichever is lower.
(e) One foot of additional building height in the front and the rear is allowed if the portion of the building above the 24-foot height limit is setback one foot.
(f) The maximum height for accessory dwelling units is established by Chapter 17.048.
(8) Setbacks. The Planning Commission may approve varied setbacks to preserve natural features, including zero-side yard setbacks provided a minimum ten-foot separation is maintained between buildings, front setbacks are at least ten feet, rear setbacks are at least 20 feet, and garage setbacks are at least 18 feet. Carports only have to meet the ten-foot front setback.
(a) The subdivision map shall specify the location of each zero-lot line house on a hillside cluster development lot.
(b) If the side wall of a house is five feet or less from the property line, windows or other openings for habitable rooms that allow visibility into adjacent yards are prohibited. However, windows and openings that do not allow visibility into adjacent yards, such as a translucent window, are allowed.
(c) To allow design flexibility, structures may encroach into a required setback for 25 percent of the building length a distance not more than one half of the reguired yard or setback, if approved by the Planning Commission through design review, provided there is a compensating increase in the opposing setback (a five-foot reduction in a front yard setback would increase the rear yard setback by five feet).
(9) Required permanent open space. At least 75 percent of the site must remain in its natural state and be preserved as permanent open space with a conservation easement, dedication or transfer to the town, another public agency, or an open space trust, or other development restriction, that runs with the land and is approved by the Town Attorney, and recorded in the Marin County Recorder's Office. None of this land can be used to meet the requirements for common and private open space established by this chapter.
(10) Allowable housing types. The Planning Commission may approve a variety of housing types, such as cluster cottage housing units, courtyard clusters, detached town homes, and tiny houses, as well as traditional single-family dwellings. Tiny houses shall meet the standards of § 17.138.520.
(11) Minimum private open space as outdoor living area. Each lot shall have a minimum 200 square foot usable yard with a minimum dimension of not less than ten feet.
(12) Common facilities. A clustered development may include shared amenities for residents' use that are designed to offer recreational opportunities and foster social interaction. These may include common open space and a common house with a kitchen and dining area for residents and guests at least 150 square feet in size, laundry, and/or recreational spaces, as well as work space for artist studios and galleries with minimum horizontal dimensions of 12 feet.
(13) A public access easement (or other development restriction that is approved by the Town Attorney) shall be used to establish new trails and trail connections to existing trails and public sidewalks to provide public access through open space parcels. The development restriction that runs with the land shall be recorded in the Marin County Recorder's Office.
(14) Parking. Parking shall be provided as required by Chapter 17.052 and the following additional requirements.
(a) One guest parking space conveniently placed relative to the dwelling unit shall be provided for every five units. The Planning Commission, may approve:
1. A reduction in order to minimize grading or avoid tree removal.
2. Allow for parking to be provided on-street in parking bays meeting the standards for parking on narrow streets set in § 10.04.060.
(b) The Planning Commission may allow one of the required resident parking spaces to be provided off-site in a common parking area that is within 200 feet of the main entrance to the dwelling unit.
(15) Landscaping. All low impact clustered residential development shall:
(a) Revegetate scarred or graded areas.
(b) On slopes of 2:1 or greater, select plant materials with deep rooting characteristics that will minimize erosion and reduce surface runoff. Subdividers also shall use a series of low retaining walls, with sub-drain lines, to increase planting areas, where feasible. This will reduce runoff and potential erosion.
(c) Use irregular spacing for new plants to achieve a natural appearance on graded slopes. Plant trees along contour lines in undulating groups to create grove effects which blur the distinctive line of the graded slopes, and plant shrubs of varying height between tree strands. Ground covers of native and introduced species are appropriate for slope erosion control.
(d) Submit a landscape documentation package that complies with the standards of the Model Water Efficient Landscape Ordinance which applies to all new residential development with 500 square feet or more of landscape area. If the total landscaped area is 2,500 square feet or less, an applicant may use the prescriptive compliance option provided in Appendix D of the Model Ordinance to streamline the review process. Under this option, turf shall not exceed 25 percent of the landscape area.
(Prior Code, § 17.38.090) (Ord. 352, passed - -1973; Am. Ord. 605, passed - -1991; Am. Ord. 886, passed 1-24-2024)