Proposed Hillside Protection (HP) Overlay Zoning District
This initiative addresses a key element of the FY 2007 non-routine work plan for the Planning & Codes Department. That work plan identified the need for new code amendments to better address and respond to hillside development in Brentwood. Our two-fold approach began with the land development revisions recently enacted via Ordinance 2007-12 (lot development standards) that address specific site problems associated with hillside lot development.
This second component of the effort is intended to better address the visual impacts and land disturbance on steep hillsides, protecting both the scenic vistas and natural terrain within the City along the higher ridges of the City through the proposed creation of a “hillside protection overlay district.” These standards are directed at minimizing the impact of building construction and land disturbance activities in steep hillside areas including but not limited to unsafe geologic disturbance; soil erosion and surface water runoff from excessive removal of trees and other vegetative cover; and severe cutting, physical scarring and visual modification of the natural terrain. While the proposed standards would make it more difficult to undertake hillside development than is currently possible, they do not prohibit such development entirely as long as such activity is carried out within the guidelines in the ordinance.
The “Hillside Protection (HP) Overlay District” would operate in a similar manner to the current floodway overlay district by covering properties within a designated area regardless of the primary zoning district classification for the property. As with the floodway overlay district, the requirements associated with the hillside overlay district shall be in addition to the requirements of the primary zoning district. Essentially, the hillside overlay district would cover all properties located at and above the 850-foot elevation within the City of Brentwood; however, land between 850-feet and 930-feet elevation which has slopes less than fifteen percent (15%) would be exempt from the additional requirements associated with new construction or development in the HP overlay district. These properties are clearly the most scenic, visible hillside locations in the City. In addition, steep areas located between elevations 850–910 feet is where colluvial soils (sliding soils) are typically present, thereby requiring special engineering for any site development. Note that the relatively flat areas between 850-930 feet elevation where development would be permitted are not among the visible hillside tracts and are not affected by unstable soil conditions. Therefore, there is no legitimate reason to exclude traditional development patterns within these areas under the intent and spirit of the ordinance. Please note that the proposed HP standards would only apply to the creation of new lots, construction of new dwellings or buildings, substantial expansion to an existing dwelling (more than 50% or 2,000 square feet, whichever is less), and land disturbance activity affecting more than 10,000 square feet.
Proposed Technical/Design Standards
Site Development Standards – The hillside protection overlay district reduces the density of residential development in such areas, setting a minimum lot area of three (3) acres. Within such hillside lots, the maximum allowable area of land disturbance is set at one (1) acre for the first three (3) acres, and one-fifth (1/5) acre for each additional one acre of the tract. No building structure can be placed in an area of steep grades (over 25 percent grade), thereby limiting development to the flatter areas with conventional or transitional grades (under 25 percent grade). In addition, structures must be placed a minimum of fifty (50) feet away from any steep grades that are visible from the lower elevations (typically the steep areas in front of a structure that is placed on flatter terrain at the top of the hill).
Streets/Driveway Standards - Public or private streets built to City standards in the hillside protection overlay district shall not exceed the maximum permitted grades in the subdivision regulations. Roadway design guidelines for the hillside protection overlay district prohibit retaining walls in excess of ten (10) feet in height as measured from final grade, and no cut and fill sections in the natural topography in excess of twenty (20) feet shall be permitted.
Private driveways shall meet the various construction and grade standards in place (20% maximum grade for hard surfaces and 10% for gravel). Retaining walls associated with driveway design are limited to six (6) feet in height as measured from final grade and must be constructed of durable materials with colors that visually blend into the natural terrain. Multiple retaining walls of terraced design with landscaping incorporated between to screen the walls are permitted under the new code. The color and composition of driveway surfaces must also visually blend into the site topography. Maximum allowable cut and fill sections for any driveway shall be 12 feet.
Note that the ordinance limits land disturbance in association with driveway construction to 20 percent of the visible steep grade area located between other properties and roadways at lower elevations and the hillside structure served by the driveway. Upon completion of a driveway, any disturbed slopes must be reestablished and replanted according to a plan approved by the Planning Commission.
Geotechnical Studies – In areas of potential soil instability, the engineering department shall require a formal geotechnical study to address site conditions and recommend appropriate design and construction methods. This ordinance language is broad enough to allow the engineering department to require a geotechnical study in any location with soil concerns.
Architectural and Landscape Standards - To the greatest extent feasible and practical, new structures shall be designed and constructed to blend into the natural terrain, and existing natural vegetation shall be preserved to the greatest extent possible. Lower profile homes are encouraged that do not extend the roof line of the dwelling above the natural tree line. Structures should be built of materials and colors that blend into the natural tree line. In addition, due to the relatively remote locations and difficulty in providing traditional fire protection, all new hillside structures intended for occupancy shall be protected by an automatic sprinkler system. In locations with open visibility to surrounding properties at lower elevations, additional evergreen trees and shrubs may be required to screen the structure better. To facilitate related landscape planning, a tree survey shall be produced for the proposed construction, identifying trees proposed for removal. This tree survey covers the proposed areas of disturbance, and extending fifty feet beyond the proposed areas of disturbance. A plan detailing additional landscape alterations and installations must be produced for Planning Commission review and approval. Note that the ordinance does allow limited removal of vegetation to open limited views from a hillside structure to the areas below, provided 75% of the structure is not visible from lower elevations during the winter season.
Non-Conforming Lots, Uses & Structures
Any existing lot of record and/or existing structure in the overlay district that was lawfully established prior to adoption of this division holds certain rights for continued use and development. However, when there are proposed improvements to expand the existing enclosed area by more than 50% or 2,000 square feet of finishable floor space, whichever is less, the site shall be brought into conformance with the new technical/design standards to the greatest extent feasible. Exceptions to the standards may be approved by the Planning Commission when it determines the proposed plan will better achieve the intent of the overlay district, or when compliance will pose an undue burden on the property owner.
Planning Commission Approval
As with proposed improvements within the Floodway Overlay District, the proposed regulations for the HP Overlay district will require review and approval of hillside development plans by the Planning Commission. Specific standards for submission of plans are outlined in the attached overlay district ordinance. Required plan details are similar to site plans presented for development in the commercial and service-institution zoning districts and include site grading, architectural elevations, landscaping, etc. In addition, computer generated graphics with a visual simulation of the proposed structure as it will appear on a photo of the hillside from the various locations, properties and roadways at lower elevations will be required.
Time Limitation/Certificate of Occupancy
Any site plan approved by the Planning Commission will expire after 24 months. If substantial construction has not begun within this time frame, the applicant must resubmit plans for consideration and re-approvals under current code standards. A certificate of occupancy will not be granted until the various requirements for approval of the plan have been completed correctly. Any violation of the plan identified during the construction process will result in the immediate issuance of a stop work order that will remain in effect until the issues are addressed and corrected to the satisfaction of the City.
Enforcement of Tree Preservation Standards
Legal restrictions are provided to ensure permanent preservation of trees within the HP areas and must be submitted to the City Attorney for review and approval. Additionally, the tree management provisions in the Zoning Ordinance would be amended to prohibit removal of trees within a designated tree protection area in the HP overlay district. Removal of any such trees would constitute a violation of the Municipal Code, with a potential penalty of $50 per tree. Exceptions would be allowed for removal of trees that pose a threat to public safety or that have been substantially harmed by disease, wind, ice or other act of God.
Ordinance Review Schedule
Prior to formal presentation of the ordinance, a draft of the hillside overlay district proposal was circulated among the members of the Board of Commissioners and the Planning Commission for review and comments, culminating in a May 29, 2007 workshop on the subject. Revisions to the draft ordinance resulting from comments from the workshop are highlighted in the attached copy. Additional wording changes proposed by staff since the ordinance was delivered to the City Commission on Thursday, June 7, 2007 are also separately identified in the attachment. Note that prior to the workshop, draft copies were also sent to the major engineering firms specializing in land development with the City of Brentwood so as to obtain technical opinions on the feasibility of the standards. Several modifications to the draft ordinance were incorporated as a result of related discussions during this review process. Staff is now recommending adoption of the revised ordinance as attached.
The draft ordinance will be presented for formal consideration by the Board of Commissioners on first reading at their regular meeting of June 14, 2007. If approved on first reading, the Planning Commission will formally review and provide recommendations on the proposal at their regular meeting of July 2, 2007, with a formal public hearing scheduled before the Board of Commissioners at their regular meeting of July 9, 2007. Second and final reading of the ordinance by the Board of Commissioners is tentatively scheduled at their regular meeting of July 23, 2007. Please feel free to contact the City Manager or me at your convenience should you have any preliminary questions or comments on this proposal.