It is the purpose of the Development Standards for Hillside Lands to provide supplementary development regulations to underlying zones to ensure that development occurs in such a manner as to protect the natural and topographic character and identity of these areas, environmental resources, the aesthetic qualities and restorative value of lands, and the public health, safety, and general welfare by insuring that development does not create soil erosion, sedimentation of lower slopes, slide damage, flooding problems, and severe cutting or scarring. It is the intent of these development standards to encourage a sensitive form of development and to allow for a reasonable use that complements the natural and visual character of the City.
A. General Requirements. The following general requirements shall apply in Hillside Lands.
1. Buildable Area. All development shall occur on lands defined as having buildable area. Slopes greater than 35 percent shall be considered unbuildable except as allowed below. Exceptions may be granted to this requirement only as provided in subsection 18.3.10.090.H.
a. Existing parcels without adequate buildable area less than or equal to 35 percent shall be considered buildable for one unit.
b. Existing parcels without adequate buildable area less than or equal to 35 percent cannot be subdivided or partitioned.
2. Building Envelope. All newly created lots either by subdivision or partition shall contain a building envelope with a slope of 35 percent or less.
3. New Streets and Driveways. New streets, flag drives, and driveways shall be constructed on lands of less than or equal to 35 percent slope with the following exceptions.
a. The street is indicated on the Street Dedication map.
b. The portion of the street, flag drive, or driveway on land greater than 35 percent slope does not exceed a length of 100 feet.
4. Geotechnical Studies. For all applications on Hillside Lands involving subdivisions or partitions, the following additional information is required: A geotechnical study prepared by a geotechnical expert indicating that the site is stable for the proposed use and development. The study shall include the following information.
a. Index map.
b. Project description to include location, topography, drainage, vegetation, discussion of previous work and discussion of field exploration methods.
c. Site geology, based on a surficial survey, to include site geologic maps, description of bedrock and surficial materials, including artificial fill, locations of any faults, folds, etc., and structural data including bedding, jointing and shear zones, soil depth, and soil structure.
d. Discussion of any off-site geologic conditions that may pose a potential hazard to the site, or that may be affected by on-site development.
e. Suitability of site for proposed development from a geologic standpoint.
f. Specific recommendations for cut and fill slope stability, seepage and drainage control, or other design criteria to mitigate geologic hazards.
g. If deemed necessary by the engineer or geologist to establish whether an area to be affected by the proposed development is stable, additional studies and supportive data shall include cross-sections showing subsurface structure, graphic logs with subsurface exploration, results of laboratory test and references.
h. Signature and registration number of the engineer and/or geologist.
i. Additional information or analyses as necessary to evaluate the site.
j. Inspection schedule for the project as required in 18.3.10.090.B.9.
k. Location of all irrigation canals and major irrigation pipelines.
B. Hillside Grading and Erosion Control. All development on lands classified as Hillside shall provide plans conforming to the following items.
1. All grading, retaining wall design, drainage, and erosion control plans for development on Hillside Lands shall be designed by a geotechnical expert. All cuts, grading or fills shall conform to the International Building Code and be consistent with the provisions of this ordinance. Erosion control measures on the development site shall be required to minimize the solids in runoff from disturbed areas.
2. Timing of Improvements. For development other than single family homes on individual lots, all grading, drainage improvements, or other land disturbances shall only occur from May 1 to October 31. Excavation shall not occur during the remaining wet months of the year. Erosion control measures shall be installed and functional by October 31. Up to 30 day modifications to the October 31 date, and 45 day modification to the May 1 date may be made by the Planning Director, based upon weather conditions and in consultation with the project geotechnical expert. The modification of dates shall be the minimum necessary, based upon evidence provided by the applicant, to accomplish the necessary project goals.
3. Retention in natural state. On all projects on Hillside Lands involving partitions and subdivisions, and existing lots with an area greater than one-half acre, an area equal to 25 percent of the total project area, plus the percentage figure of the average slope of the total project area, shall be retained in a natural state. Lands to be retained in a natural state shall be protected from damage through the use of temporary construction fencing or the functional equivalent. For example, on a 25,000 square feet lot with an average slope of 29 percent, 25%+29%=54% of the total lot area shall be retained in a natural state. The retention in a natural state of areas greater than the minimum percentage required here is encouraged.
4. Grading - Cuts. On all cut slopes on areas classified as Hillside Lands, the following standards shall apply.
a. Cut slope angles shall be determined in relationship to the type of materials of which they are composed. Where the soil permits, limit the total area exposed to precipitation and erosion. Steep cut slopes shall be retained with stacked rock, retaining walls, or functional equivalent to control erosion and provide slope stability when necessary. Where cut slopes are required to be laid back (1:1 or less steep), the slope shall be protected with erosion control getting or structural equivalent installed per manufacturers specifications, and revegetated.
b. Exposed cut slopes, such as those for streets, driveway accesses, or yard areas, greater than seven feet in height shall be terraced. Cut faces on a terraced section shall not exceed a maximum height of five feet. Terrace widths shall be a minimum of three feet to allow for the introduction of vegetation for erosion control. Total cut slopes shall not exceed a maximum vertical height of 15 feet. The top of cut slopes not utilizing structural retaining walls shall be located a minimum setback of one-half the height of the cut slope from the nearest property line. See Figure 18.3.10.090.B.4.b.
c. Cut slopes for structure foundations which reduce the effective visual bulk, such as split pad or stepped footings, shall be exempted from the height limitations of this section. See Figure 18.3.10.090.B.c.
d. Revegetation of cut slope terraces shall include the provision of a planting plan, introduction of top soil where necessary, and the use of irrigation if necessary. The vegetation used for these areas shall be native, or species similar in resource value to native plants, which will survive, help reduce the visual impact of the cut slope, and assist in providing long term slope stabilization. Trees, bush-type plantings, and cascading vine-type plantings may be appropriate.
5. Grading - Fill. On all fill slopes on lands classified as Hillside Lands, the following standards shall apply.
a. Fill slopes shall not exceed a total vertical height of 20 feet. The toe of the fill slope area not utilizing structural retaining shall be a minimum of six feet from the nearest property line.
b. Fill slopes shall be protected with an erosion control netting, blanket or functional equivalent. Netting or blankets shall only be used in conjunction with an organic mulch such as straw or wood fiber. The blanket must be applied so that it is in complete contact with the soil so that erosion does not occur beneath it. Erosion netting or blankets shall be securely anchored to the slope in accordance with manufacturer's recommendations.
c. Whenever possible, utilities shall not be located or installed on or in fill slopes. When determined that it necessary to install utilities on fill slopes, all plans shall be designed by a geotechnical expert.
d. Revegetation of fill slopes shall utilize native vegetation or vegetation similar in resource value and which will survive and stabilize the surface. Irrigation may be provided to ensure growth if necessary. Evidence shall be required indicating long-term viability of the proposed vegetation for the purposes of erosion control on disturbed areas.
6. Revegetation Requirements. Where required by this chapter, all required revegetation of cut and fill slopes shall be installed prior to the issuance of a certificate of occupancy, signature of a required survey plat, or other time as determined by the hearing authority. Vegetation shall be installed in such a manner as to be substantially established within one year of installation.
7. Maintenance, Security, and Penalties for Erosion Control Measures.
a. Maintenance. All measures installed for the purposes of long-term erosion control, including but not limited to vegetative cover, rock walls, and landscaping, shall be maintained in perpetuity on all areas which have been disturbed, including public rights-of-way. The applicant shall provide evidence indicating the mechanisms in place to ensure maintenance of measures.
b. Security. Except for individual lots existing prior to January 1, 1998, after an Erosion Control Plan is approved by the hearing authority and prior to construction, the applicant shall provide a performance bond or other financial guarantees in the amount of 120 percent of the value of the erosion control measures necessary to stabilize the site. Any financial guarantee instrument proposed, other than a performance bond, shall be approved by the City Attorney. The financial guarantee instrument shall be in effect for a period of at least one year, and shall be released when the Community Development Director and Public Works Director determine, jointly, that the site has been stabilized. All or a portion of the security retained by the City may be withheld for a period up to five years beyond the one year maintenance period if it has been determined by the City that the site has not been sufficiently stabilized against erosion.
8. Site Grading. The grading of a site on Hillside Lands shall be reviewed considering the following factors.
a. No terracing shall be allowed except for the purposes of developing a level building pad and for providing vehicular access to the pad.
b. Avoid hazardous or unstable portions of the site.
c. Avoid hazardous or unstable portions of the site.
d. Building pads should be of minimum size to accommodate the structure and a reasonable amount of yard space. Pads for tennis courts, swimming pools and large lawns are discouraged. As much of the remaining lot area as possible should be kept in the natural state of the original slope.
9. Inspections and Final Report. Prior to the acceptance of a subdivision by the City, signature of the final survey plat on partitions, or issuance of a certificate of occupancy for individual structures, the project geotechnical expert shall provide a final report indicating that the approved grading, drainage, and erosion control measures were installed as per the approved plans, and that all scheduled inspections, as per 18.3.10.090.A.4.j were conducted by the project geotechnical expert periodically throughout the project.
C. Surface and Groundwater Drainage. All development on Hillside Lands shall conform to the following standards.
1. All facilities for the collection of stormwater runoff shall be constructed on the site and according to the following requirements:
a. Stormwater facilities shall include storm drain systems associated with street construction, facilities for accommodating drainage from driveways, parking areas and other impervious surfaces, and roof drainage systems.
b. Stormwater facilities, when part of the overall site improvements, shall be, to the greatest extent feasible, the first improvements constructed on the development site.
c. Stormwater facilities shall be designed to divert surface water away from cut faces or sloping surfaces of a fill.
d. Existing natural drainage systems shall be utilized, as much as possible, in their natural state, recognizing the erosion potential from increased storm drainage.
e. Flow-retarding devices, such as detention ponds and recharge berms, shall be used where practical to minimize increases in runoff volume and peak flow rate due to development. Each facility shall consider the needs for an emergency overflow system to safely carry any overflow water to an acceptable disposal point.
f. Stormwater facilities shall be designed, constructed and maintained in a manner that will avoid erosion on-site and to adjacent and downstream properties.
g. Alternate stormwater systems, such as dry well systems, detention ponds, and leach fields, shall be designed by a registered engineer or geotechnical expert and approved by the Public Works Department or Building Official.
D. Tree Conservation, Protection and Removal. All development on Hillside Lands shall conform to the following requirements.
1. Inventory of Existing Trees. A tree survey at the same scale as the project site plan shall be prepared, which locates all trees greater than six inches diameter at breast height (DBH) identified by DBH, species, approximate extent of tree canopy. In addition, for areas proposed to be disturbed, existing tree base elevations shall be provided. Dead or diseased trees shall be identified. Groups of trees in close proximity (i.e., those within five feet of each other) may be designated as a clump of trees, with the predominant species, estimated number and average diameter indicated. All tree surveys shall have an accuracy of plus or minus two feet. The name, signature, and address of the site surveyor responsible for the accuracy of the survey shall be provided on the tree survey. Portions of the lot or project area not to be disturbed by development need not be included in the inventory.
2. Evaluation of Suitability for Conservation. All trees indicated on the inventory of existing trees shall also be identified as to their suitability for conservation. When required by the hearing authority, the evaluation shall be conducted by a landscape professional. The following factors shall be included in this determination.
a. Tree Health. Healthy trees can better withstand the rigors of development than non-vigorous trees.
b. Tree Structure. Trees with severe decay or substantial defects are more likely to result in damage to people and property.
c. Species. Species vary in their ability to tolerate impacts and damage to their environment.
d. Longevity. Potential longevity.
e. Variety. A variety of native tree species and ages.
f. Size. Large trees provide a greater protection for erosion and shade than smaller trees.
3. Tree Conservation in Project Design. Significant trees (two feet DBH or greater conifers and one foot DBH or greater broadleaf) shall be protected and incorporated into the project design whenever possible.
a. Streets, driveways, buildings, utilities, parking areas, and other site disturbances shall be located such that the maximum number of existing trees on the site are preserved, while recognizing and following the standards for fuel reduction if the development is located in Wildfire Lands. See Figure 18.3.10.090.D.3.a.
b. Building envelopes shall be located and sized to preserve the maximum number of trees on site while recognizing and following the standards for fuel reduction if the development is located in Wildfire Lands.
c. Layout of the project site utility and grading plan shall avoid disturbance of tree protection areas.
4. Tree Protection. On all properties where trees are required to be preserved during the course of development, the developer shall follow the following tree protection standards.
a. All trees designated for conservation shall be clearly marked on the project site. Prior to the start of any clearing, stripping, stockpiling, trenching, grading, compaction, paving or change in ground elevation, the applicant shall install tree protection fencing in accordance with 18.4.5.030.C Prior to any construction activity, the shall be inspected pursuant to section 18.4.5.030.D.
b. Construction site activities, including but not limited to parking, material storage, soil compaction, and concrete washout, shall be arranged so as to prevent disturbances within tree protection areas.
c. No grading, stripping, compaction, or significant change in ground elevation shall be permitted within the drip line of trees designated for conservation unless indicated on the grading plans, as approved by the City, and landscape professional. If grading or construction is approved within the drip-line, a landscape professional may be required to be present during grading operations, and shall have authority to require protective measures to protect the roots.
d. Changes in soil hydrology and site drainage within tree protection areas shall be minimized. Excessive site run-off shall be directed to appropriate storm drain facilities and away from trees designated for conservation.
e. Should encroachment into a tree protection area occur which causes irreparable damage, as determined by a landscape professional, to trees, the project plan shall be revised to compensate for the loss. Under no circumstances shall the developer be relieved of responsibility for compliance with the provisions of this chapter.
5. Tree Removal. Development shall be designed to preserve the maximum number of trees on a site. The development shall follow the standards for fuel reduction if the development is located in Wildfire Lands. When justified by findings of fact, the hearing authority may approve the removal of trees for one or more of the following conditions.
a. The tree is located within the building envelope.
b. The tree is located within a proposed street, driveway, or parking area.
c. The tree is located within a water, sewer, or other public utility easement.
d. The tree is determined by a landscape professional to be dead or diseased, or it constitutes an unacceptable hazard to life or property when evaluated by the standards in 18.3.10.090.D.2.
e. The tree is located within or adjacent to areas of cuts or fills that are deemed threatening to the life of the tree, as determined by a landscape professional.
6. Tree Replacement. Trees approved for removal, with the exception of trees removed because they were determined to be diseased, dead, or a hazard, shall be replaced in compliance with the following standards.
a. Replacement trees shall be indicated on a tree replanting plan. The replanting plan shall include all locations for replacement trees, and shall also indicate tree planting details.
b. Replacement trees shall be planted such that the trees will in time result in canopy equal to or greater than the tree canopy present prior to development of the property. See Figure 18.3.10.090.D.6.b. The canopy shall be designed to mitigate of the impact of paved and developed areas, reduce surface erosion, and increase slope stability. Replacement tree locations shall consider impact on the wildfire prevention and control plan. The hearing authority shall have the discretion to adjust the proposed replacement tree canopy based upon site-specific evidence and testimony.
c. Maintenance of replacement trees shall be the responsibility of the property owner. Required replacement trees shall be continuously maintained in a healthy manner. Trees that die within the first five years after initial planting must be replaced in kind, after which a new five-year replacement period shall begin. Replanting must occur within 30 days of notification unless otherwise noted.
a. All tree removal shall be done in accord with the approved tree removal and replacement plan. No trees designated for conservation shall be removed without prior approval of the City.
b. Should the developer or developer's agent remove or destroy any tree that has been designated for conservation, the developer may be fined up to three times the current appraised value of the replacement trees and cost of replacement or up to three times the current market value, as established by a professional arborist, whichever is greater.
c. Should the developer or developer's agent damage any tree that has been designated for protection and conservation, the developer shall be penalized $50.00 per scar. If necessary, a professional arborist's report, prepared at the developer's expense, may be required to determine the extent of the damage. Should the damage result in loss of appraised value greater than determined above, the higher of the two values shall be used.
E. Building Location and Design Standards. All buildings and buildable areas proposed for Hillside Lands shall be designed and constructed in compliance with the following standards.
1. Building Envelopes. All newly created lots, either by subdivision or partition, shall contain building envelopes conforming to the following standards.
a. The building envelope shall contain a buildable area with a slope of 35 percent or less. See Figure 18.3.10.090.E.1.a.
b. Building envelopes and lot design shall address the retention of a percentage of the lot in a natural state as required in 18.3.10.090.B.3.
c. Building envelopes shall be designed and located to maximize tree conservation as required in 18.3.10.090.D.3 while recognizing and following the standards for fuel reduction if the development is located in Wildfire Lands.
d. It is recommended that building envelope locations should be located to avoid ridgeline exposures, and designed such that the roofline of a building within the envelope does not project above the ridgeline as illustrated in Figure 18.3.10.090.E.1.d.
2. Building Design. To reduce hillside disturbance through the use of slope responsive design techniques, buildings on Hillside Lands, excepting those lands within the designated Historic District, shall incorporate the following into the building design and indicate features on required building permits.
a. The height of all structures shall be measured vertically from the natural grade to the uppermost point of the roof edge or peak, wall, parapet, mansard, or other feature perpendicular to that grade. Maximum hillside building height shall be 35 feet. See Figure 18.3.10.090.E.2.a.i and Figure 18.3.10.090.E.2.a.ii
b. Cut buildings into hillsides to reduce effective visual bulk.
i. Split pad or stepped footings shall be incorporated into building design to allow the structure to more closely follow the slope.
ii. Reduce building mass by utilizing below grade rooms cut into the natural slope.
c. A building step back shall be required on all downhill building walls greater than 20 feet in height, as measured above natural grade. Step-backs shall be a minimum of six feet. Decks projecting out from the building wall and hillside shall not be considered a building step-back. No vertical walls on the downhill elevations of new buildings shall exceed a maximum height of 20 feet above natural grade. See Figure 18.3.10.090.E.2.c.
d. Continuous horizontal building planes shall not exceed a maximum length of 36 feet. Planes longer than 36 feet shall include a minimum offset of six feet. See Figure 18.3.10.090.E.2.d.
e. It is recommended that roof forms and roof lines for new structures be broken into a series of smaller building components to reflect the irregular forms of the surrounding hillside. Long, linear unbroken roof lines are discouraged. Large gable ends on downhill elevations should be avoided, however smaller gables may be permitted. See Figure 18.3.10.090.E.2.c.
f. It is recommended that roofs of lower floor levels be used to provide deck or outdoor space for upper floor levels. The use of overhanging decks with vertical supports in excess of 12 feet on downhill elevations should be avoided.
g. It is recommended that color selection for new structures be coordinated with the predominant colors of the surrounding landscape to minimize contrast between the structure and the natural environment.
F. All structures on Hillside Lands shall have foundations designed by an engineer or architect with demonstrable geotechnical design experience. A designer, as defined, shall not complete working drawings without having foundations designed by an engineer.
G. All newly created lots or lots modified by a lot line adjustment must include building envelopes containing a buildable area less than 35 percent slope of sufficient size to accommodate the uses permitted in the underlying zone, unless the division or lot line adjustment is for open space or conservation purposes.
H. Exception to the Development Standards for Hillside Lands. An exception under this section is not subject to the variance requirements of chapter 18.5.5 Variances. An application for an exception is subject to the Type I procedure in section 18.5.1.050 and may be granted with respect to the development standards for Hillside Lands if the proposal meets all of the following criteria.
1. There is demonstrable difficulty in meeting the specific requirements of this chapter due to a unique or unusual aspect of the site or proposed use of the site.
2. The exception will result in equal or greater protection of the resources protected under this chapter.
3. The exception is the minimum necessary to alleviate the difficulty.
4. The exception is consistent with the stated Purpose and Intent of chapter 18.3.10 Physical and Environmental Constraints Overlay chapter and section 18.3.10.090 Development Standards for Hillside Lands.