Diamond Bar Municipal Code Ch. 21.30 Subdivision Design and Improvement Requirements

This chapter establishes standards for the design and layout of subdivisions, and the design, construction or installation of public improvements within subdivisions. The purpose of these standards is to ensure, through careful site evaluation and design, the creation of new parcels that are consistent with the general plan and any applicable specific plan.

(Ord. No. 01(1999), § B, 2-2-99)

The requirements of this chapter apply to subdivisions, and conditional certificates of compliance, in addition to all applicable requirements of the development code (title 22) and this title, as follows:

(1) Design standards. The standards in section 21.30.030 et seq. of this chapter apply to the design of all proposed subdivisions, in addition to all applicable requirements of the city engineer, and the Diamond Bar Development Improvement Standards, Requirements, and Guidelines.

(2) Subdivision improvement standards—Conditions of approval. The applicable subdivision improvement and dedication requirements of this chapter and any other improvements and dedications required by the review authority in compliance with section 21.20.080 (Tentative map approval or disapproval) shall be described in conditions of approval adopted for each approved tentative map (section 21.20.090). The design, construction or installation of all subdivision improvements shall comply with the requirements of the city engineer.

(3) Conflicting provisions. In the event of any conflict between the provisions of this chapter and other provisions of this title, or other provisions of the Municipal Code, the most restrictive provisions shall control. In the event of any conflict between the provisions of this chapter and the map act, the map act shall control.

(4) Extent of improvements required—Four or fewer parcels. As required by map act section 66411.1, improvements required for subdivisions of four or fewer parcels shall be limited to the dedication of rights-of-way, easements, and the construction of reasonable offsite and onsite improvements for the parcels being created.

(5) Oversizing of improvements. At the discretion of the review authority, improvements required to be installed by the subdivider for the benefit of the subdivision may also be required to provide supplemental size, capacity, number, or length for the benefit of property not within the subdivision, and may be required to be dedicated to the city, in compliance with article 6, chapter 4 of the map act. In the event that oversizing is required, the city shall comply with all applicable provisions of map act sections 66485 et seq., including the reimbursement provisions of map act section 66486.

(6) Exceptions. Exceptions to the provisions of this chapter may be requested and considered in compliance with section 21.03.050 (Exceptions to subdivision standards).

(Ord. No. 01(1999), § B, 2-2-99)

Proposed subdivisions shall be designed to provide adequate access from each new parcel to a city street, in compliance with this section.

(1) General access and circulation requirements. The subdivider shall provide a comprehensive street system, designed and constructed in compliance with this section, the Diamond Bar Development Improvement Standards, Requirements, and Guidelines, and with the circulation element of the general plan.

a. Street design shall provide for safe vehicular operation at a specified design speed.

b. Public streets shall be required when:

1. The street is shown as an arterial or collector in the circulation element of the general plan, or any other specific or precise plan;

2. The street will be used by the general public as a through access route; or

3. A public street is necessary for special needs including bus routes, public service access, bicycle routes and pedestrian access.

Private streets are allowed only in compliance with subsection (5), following.

(2) Access to subdivision. Every subdivision shall be designed to have access to a city street. Access shall be provided by:

a. The subdivision abutting a city street, where the length of the subdivision along the street, the street right-of-way, and the width of the right-of-way will accommodate the construction of all road improvements required by this section; or

b. The subdivision being connected to a city street by a nonexclusive right-of-way easement for street, utility, and appurtenant drainage facilities purposes, where the easement shall be:

1. Offered for dedication;

2. Unencumbered by any senior rights that might serve to restrict its proposed use; and

3. Of a width and location to accommodate the construction of all improvements required by this section and the city's Development Improvement Standards, Requirements and Guidelines.

(3) Access to new parcels. Parcels within a proposed subdivision shall be provided access as follows.

a. City street access required. Each parcel within a proposed subdivision shall be provided access by being located on an existing city street or a new city street designed and improved in compliance with subsection (2) of this section, or to a private street if allowed by subsection (5) of this section.

b. Access denial. When a state highway or a street classified as a major arterial in the circulation element of the general plan passes through or abuts a proposed subdivision, direct access to the highway or arterial shall not be permitted from proposed parcels. Reservation strips shall be dedicated to the state or city, as appropriate, where required to control access over certain lot lines over the ends of street stubs.

c. Frontage roads. When lots are proposed to front on a major arterial or state highway, the review authority may require the subdivider to dedicate and improve a service or frontage road separate from the arterial or highway.

d. Alleys. Alleys may be proposed as part of nonresidential subdivisions, but shall not be allowed in residential subdivisions. When a subdivision is proposed in an area zoned commercial or industrial, the subdivider may be required to dedicate and improve alleys at least 20 feet wide at the rear of the parcels.

(4) Design and improvement of proposed streets. New streets proposed or required within a new subdivision or adjacent to a new subdivision shall be located and designed as follows, and in compliance with the Diamond Bar Development Improvement Standards, Requirements and Guidelines:

a. Alignment. The alignment of streets shown on a tentative map shall be:

1. Consistent with the circulation element of the general plan, where applicable; and

2. Located to be in alignment with existing adjacent streets by continuation of their centerlines, or by adjustments by curves;

b. Right-of-way and surfaced width. The width of the right-of-way and improved surface of streets shown on a tentative map shall be as provided by the Diamond Bar Development Improvement Standards, Requirements and Guidelines.

c. Access to unsubdivided property. When a proposed subdivision abuts vacant land that is designated by the general plan for future subdivision and development, the review authority may require that streets to be constructed within the proposed subdivision be extended to the boundary of the property to provide access to the future development.

d. Improvements to existing streets. When an existing city street provides access to, passes through, or is contiguous with a proposed subdivision, the review authority may require dedication of additional right-of-way and/or improvements in compliance with the general plan, if it is determined that the proposed subdivision will create the need for the improvements.

e. Length of loop, cul-de-sac, and other dead-end streets. The maximum length of a loop street shall be 1,200 feet. A proposed subdivision shall not be designed with a dead-end street having a length greater than 500 feet from the first intersecting through street. Maximum length shall be measured from the edge of the roadway surface at the intersection that begins the road, to the end of the road surface at its farthest point.

(5) Private roads. Private roads are allowed as provided in this section. Private roads shall not be permitted except where the council determines that a private street system will adequately serve the proposed subdivision, will not be a substantial detriment to adjoining properties and will not disrupt or prevent the establishment of an orderly circulation system in the vicinity of the subdivision.

a. Maintenance requirements. Provisions satisfactory to the city attorney shall be made for lot owners association or other organization to assume responsibility for the maintenance of private roads and ownership of the street rights-of-way of any subdivision.

b. Design and improvement standards. Private roads shall be designed and improved as set forth in subsections (2) and (3).

c. Security and conditions. The commission and/or council may require any guarantees and conditions it deems necessary to carry out the provisions of this title pertaining to private roads. Private roads and easements providing access to parcels within a subdivision shall be located and shown on the parcel or final map.

d. Offer of dedication. All proposed private roads shall be subject to irrevocable offers of dedication to the city on the applicable parcel or final map, or separate instrument submitted to the city along with the parcel or final map.

(6) Alternative circulation systems. Proposed subdivisions shall be designed to provide rights-of-way for pedestrian paths, bikeways and multiple-use trails consistent with the circulation element of the general plan, and/or the city-wide comprehensive parks master plan, as applicable.

(7) Alternative standards. The review authority may consider and approve proposed access and street design solutions that differ from the provisions of this section, and the city's Development Improvement Standards, Requirements, and Guidelines where deemed necessary to properly address the characteristics of adjacent land uses and/or anticipated traffic volumes, or to maintain neighborhood character. The use of alternative standards shall be authorized through the exception procedure in section 21.03.050.

(Ord. No. 01(1999), § B, 2-2-99)

The design of a subdivision for which a tentative and final map are required by this title shall provide, to the extent feasible, for future passive or natural heating or cooling opportunities in the subdivisions, in compliance with map act section 66473.1.

(Ord. No. 01(1999), § B, 2-2-99)

(a) Installation, location, number. The subdivider shall install fire hydrants connected to a water supply capable of delivering the required fire flow, within the public right-of-way, along private streets, and/or on the site to be protected in compliance with this section.

(1) The number and location of fire hydrants shall be determined by the review authority based upon recommendations from the fire chief.

(2) Standard hydrant spacing shall be at 300-foot intervals in all areas except areas containing only single-story single-family or duplex dwellings, in which case standard hydrant spacing shall be at 500-foot intervals.

(3) The review authority may make minor modifications to the hydrant placement distances above based on recommendations from the fire chief, where the review authority determines that it would not be adverse to the city's fire protection capabilities. In no case shall fire hydrants be spaced closer than 300-foot intervals.

(b) Hydrant type. Proposed fire hydrants shall be a model approved by the fire chief.

(Ord. No. 01(1999), § B, 2-2-99)

New subdivisions shall be designed so that all proposed grading incorporates appropriate erosion and sediment control measures in compliance with section 18.108.190 of the Municipal Code.

(Ord. No. 01(1999), § B, 2-2-99)

(a) Landscaping requirements. Landscaping shall be provided as follows, and in compliance with chapter 22.24 (Landscaping Standards), and section 22.30.070(h) (Development standards for off-street parking—landscaping) of the development code, where applicable.

(1) Residential subdivision. The developer shall provide a residential subdivision with landscaping in the form of street trees on each proposed parcel that is not a flag lot, landscaping with irrigation facilities for any common areas or other open space areas within the subdivision, and any additional landscaping required by the review authority.

(2) Nonresidential subdivisions. The developer shall provide a nonresidential subdivision with landscaping as required by the review authority.

(b) Plant materials, irrigation. All proposed and/or required trees, shrubs, ground covers, vines, turf, and other plant materials shall be of a type approved by the director and, to the greatest extent practicable, shall be of drought-resistant and drought-tolerant types or varieties. Plant materials and irrigation systems shall comply with the requirements of chapter 22.24 (Landscaping Standards) of the development code. The subdivider shall provide a mechanism or system for the permanent maintenance of any common area or open space landscaping.

(c) Deferral of installation. The installation of required landscaping may be deferred until the development of the subdivided lots through the provisions of section 21.34.040 (Improvement agreements and security), provided that interim erosion and sediment control measures are first installed in compliance with section 21.30.060 above (Grading, erosion and sediment control).

(Ord. No. 01(1999), § B, 2-2-99)

The review authority may require the subdivider to provide major structures, including retaining walls, bridges or dams, based on the needs for these facilities created by the subdivision. Each structure shall be designed and approved on an individual basis. The subdivider shall provide the city with all drawings, specifications, and engineering calculations used in the design and construction of a major structure.

(Ord. No. 01(1999), § B, 2-2-99)

The subdivider shall install monuments in compliance with chapter 21.36 (Surveys and Monuments), and the map act.

(Ord. No. 01(1999), § B, 2-2-99)

The size, shape and arrangement of proposed parcels shall comply with this section, or with any general plan policy, applicable specific plan requirement, other development code provision, or other Municipal Code provision applicable to a proposed subdivision.

(1) Parcel area. The minimum area for new parcels shall be as required by article II (zoning districts and allowable land uses), except as otherwise provided by this section.

a. Calculation of area. When calculating the area of a parcel to determine compliance with this section, article II, or the general plan, the following shall be deducted from the gross area of any parcel, regardless of whether they may be used by the general public or are reserved for residents of the subdivision:

1. A vehicular or nonvehicular access easement through the parcel;

2. An easement for an open drainage course, whether a ditch, natural channel or floodway; or

3. The "flag pole" (access strip) of a flag lot. (See subsection (2)e., following.)

b. Minimum lot area requirements for common interest developments. The minimum lot area requirements of article II shall not apply to condominiums and condominium conversions, planned developments, townhouses, zero lot line, and similar common interest developments, but shall apply to the creation of the original parcel or parcels that are the location of the common interest development.

(2) Dimensions. The dimensions of new parcels shall be as follows.

a. Parcel width. New parcels shall be designed to have a minimum width of 50 feet; except that each parcel on a turnaround, cul-de-sac or curved street, where the side lot lines are diverging from the front to the rear of the parcel, shall have a minimum width of 60 feet, measured at the front setback line required for the primary structure by article II.

b. Parcel depth. No new parcel shall have a depth less than 80 feet, or a depth greater than three times the average width of the lot when the lot has a width of less than 250 feet.

c. Exceptions. The review authority may approve parcels with different dimensions than provided by this section within the PD (planned development) overlay zoning district, or where the review authority determines different dimensions are appropriate because of topographic constraints.

d. Location of lot lines.

1. Orientation to streets. The side lot lines of all parcels shall be at right angles to the centerline of the street, and radial to curved streets, to provide adequate street frontage for each parcel.

2. City limits. No parcel shall be designed so that it will be divided by the city's corporate boundary.

3. Relationship to easements. Parcels shall be designed so that lot lines conform to existing or planned easements unless the easements are relocated to conform with the proposed lot pattern.

e. Flag lots. Flag lots are generally discouraged unless they can improve the efficiency of land use, or protect natural features, and/or are desirable because of topographic constraints. Where determined to be appropriate by the review authority, flag lots shall comply with the following requirements.

1. Lot design, size. The main portion of the flag lot (not including the access strip, or "flag pole") shall satisfy the provisions of this section for length, depth, area and design. In no case shall the access strip be less than 20 feet in width, nor more than 200 feet in depth.

2. Number of housing units served. No tentative map shall be approved with more than four homes being provided access to a public street by means of a single flag access strip.

(3) Parcel and block configuration. The layout of proposed parcels and streets shall be designed to use land efficiently, mitigate environmental impacts, and minimize site disturbance in terms of cuts and fills, and the removal of significant vegetation.

a. Double-frontage lots. Parcels with streets along both the front and rear lot lines shall be prohibited, except when necessitated by topographical or other physical conditions or where access from one of the roads is prohibited.

b. Block length. Blocks shall be no longer than 1,200 feet unless existing conditions warrant an exception (section 21.03.050).

(4) Building pads on hillside lots. A tentative map proposing parcels with a slope of 20 percent or greater shall show proposed pad locations. Approved pad locations shall be shown on a supplemental information sheet in compliance with section 21.22.110 (Supplemental information sheets), recorded with an approved parcel or final map.

(5) Driveway standards. Proposed parcels shall be designed to accommodate driveways designed in compliance with section 22.30.080 (Driveways and site access) of the development code.

(Ord. No. 01(1999), § B, 2-2-99)

Public utilities, including electricity, gas, water, sewer, storm drains and telecommunications services, shall be installed as part of the improvements within all subdivisions as provided by this section, and by sections 21.30.130 (Sewage disposal) and 21.30.180 (Water supply). The installation of utilities may be waived by the review authority through an exception granted in compliance with section 21.03.050, if the review authority also finds that not installing the utilities as part of the subdivision improvements will be in the public interest.

(1) Underground utilities required. Utilities in new subdivisions shall be installed underground, as follows:

a. When undergrounding is required. All existing and proposed utility distribution facilities (including electric, telecommunications and cable television lines) installed in and for the purpose of supplying service to any subdivision shall be installed underground. Equipment appurtenant to underground facilities, including surface-mounted transformers, pedestal-mounted terminal boxes and meter cabinets, and concealed ducts, shall also be underground, unless otherwise approved by the review authority based on the recommendations of the city engineer.

The subdivider is responsible for complying with the requirements of this section and shall make the necessary arrangements with the affected utility companies for facility installation. The review authority may waive the requirements of this section if topographical, soil, or any other conditions make underground installation unreasonable or impractical.

b. Location of installation. Underground utility lines may be installed within street rights-of-way or along a lot line, subject to appropriate easements being provided if necessary. When installed within street rights-of-way, their location and method of installation, insofar as it affects other improvements within the street right-of-way, shall be subject to the approval of the city engineer.

(2) Utility easements.

a. Minimum width. The minimum width of easements for public or private utilities, sanitary sewers, or water distribution systems shall be determined by the review authority based on the recommendations of the city engineer for city facilities, and the recommendations of the applicable utility company, for public or private utilities.

b. Overhead lines. When overhead utility lines are approved by the review authority, easements shall be located at the rear of lots where practical, and along the side of lots where necessary. Where practical, the poles supporting overhead lines shall not be installed within any street, alley, or easement designated exclusively for drainage purposes.

(3) Timing of installation. All underground utilities, water lines, sanitary sewers, and storm drains installed in streets shall be constructed before the streets are surfaced. Connections to all underground utilities, waterlines, and sanitary sewers shall be laid to sufficient lengths to avoid the need for disturbing the street improvements when service connections are made.

(Ord. No. 01(1999), § B, 2-2-99)

The maximum number of dwelling units permitted within a proposed subdivision shall not exceed the density established by the general plan for the site or the maximum number of dwelling units permitted by the applicable zoning district, and may be further restricted by considerations of safety, traffic access or circulation, the slope of the natural terrain, the physical suitability of the site, the nature or extent of existing development, the availability of public facilities, utilities, or open spaces or any other provision of this title.

(Ord. No. 01(1999), § B, 2-2-99)

(a) System design. A proposed subdivision shall be designed to provide for connection to the city's sewage collection system, except in areas previously approved for the use of on-site sewage disposal systems.

(b) Agreement for on-site systems required. Where on-site systems are allowed, the tentative map applicant shall be required to execute and record an agreement with the city committing to not protest the formation of an improvement district that may be formed for the installation of a sewage collection system.

(c) City engineer approval. Where any part of a sewage collection system is proposed to be installed within a street right-of-way, the system location and construction specifications shall be subject to the approval of the city engineer.

(d) Timing of construction. A sewage collection system shall be installed as part of the improvements within all subdivisions.

(Ord. No. 01(1999), § B, 2-2-99)

A proposed subdivision shall incorporate street lighting facilities determined by the review authority to be consistent with the character of the area, and the needs of public safety, and designed and constructed to the standards established by the city engineer.

(Ord. No. 01(1999), § B, 2-2-99)

All streets within a proposed subdivision shall be named, and the names shall be approved by the review authority. Duplication of existing names within the same area shall not be allowed in a new subdivision unless the street is an obvious extension of an existing street.

(Ord. No. 01(1999), § B, 2-2-99)

(a) Drainage systems required. The developer shall provide a subdivision with storm drainage facilities as required by this section, and section 21.30.160 (storm drainage and runoff).

(1) Performance and capacity. Subdivisions shall be designed to provide drainage systems to carry storm runoff both tributary to and originating within the subdivision to approved points of discharge, determined to be necessary by the city engineer on the basis of information and recommendations provided by the engineer for the subdivider. Drainage facilities shall be designed for a flood frequency of 50 years, unless otherwise approved by the city engineer. Drainage system design shall avoid unnatural concentrations of stormwater runoff and retain existing drainage courses wherever possible.

(2) Culverts. The minimum diameter of a storm drain pipe placed beneath a public street shall be 18 inches. Pipe materials shall be approved by the city engineer, and placed at the grade of the drainage channel whenever practical. Minimum allowable culvert grade shall be 1.0 percent under normal circumstances. Minimum allowable open ditch grade shall be 2.0 percent.

(3) Location of facilities. Drainage facilities shall be located within a street right-of-way or within public drainage easements.

(4) Timing of installation. Any drainage structures required for the individual parcels of a subdivision shall be installed at the same time as drainage structures within street rights-of-way and other subdivision improvements.

(5) Interim maintenance. All subdivision drainage facilities shall be maintained by the developer until accepted by the city or Los Angeles County Flood Control District.

(b) Drainage easements. Required drainage systems shall be located within drainage easements delineated on the final map or parcel map, and the easements shall satisfy the following standards. Drainage easements shall be dedicated to the city and designed to Los Angeles County Flood Control District standards.

(1) Offer of dedication. Drainage easements shall be offered for dedication.

(2) Alignment of easements. The alignment of drainage easements should conform to the natural watercourse or to the alignment approved for the drainage system.

(3) Width of easements.

a. Natural channels. A drainage easement for a natural channel is required where determined to be necessary by the city engineer. The width of drainage easements for natural channels shall be sufficient to include the 100-year flood high water marks, plus five feet on either side, but in no case less than 20 feet.

b. Constructed channels. The minimum width of any drainage easement for a closed drainage conduit system shall be ten feet and the minimum width for any open system shall be 20 feet.

c. Service roads. For any drainage conduit exceeding 30 inches in diameter, or any open ditch with a top width exceeding 12 feet, a 12-foot service road shall be improved within the drainage easement and dedicated to the city.

(4) Downstream property. Where a subdivision causes an increase in and the unnatural concentration of surface waters onto adjacent private or public property, the subdivider shall design the system to mitigate the anticipated increases, or shall obtain an easement for drainage purposes across the property of sufficient width and shall improve the easement in a manner adequate to convey the runoff to a point of disposal approved by the review authority based on the recommendation of the city engineer.

(Ord. No. 01(1999), § B, 2-2-99)

Traffic control and safety devices shall be installed by the subdivider during subdivision construction as required by the review authority, to promote traffic control and safety both during construction, and after occupancy of the subdivision. Traffic control and safety devices shall include regulatory signs, warning signs, guide markers, construction signs, pavement markings, lane delineations, and traffic signals, as determined to be necessary by the review authority. Street name signs shall be installed at all public, private and public/private intersections in compliance with section 21.30.150 (street names).

(Ord. No. 01(1999), § B, 2-2-99)

Water mains and services shall be installed to serve each lot in a proposed subdivision and connected to the facilities of the Walnut Valley Municipal Water District. If any part of the water system is to be installed within a street right-of-way, the system location, including valve boxes, meter boxes, and fire hydrants and the system construction specifications shall be subject to the approval of the city engineer, and the location of fire hydrants shall also be approved by the fire chief.

(Ord. No. 01(1999), § B, 2-2-99)