Columbia Subdivision standards ordinance (§ 29-5.1)

(a) Applicability.

(1) The standards in this article 5 shall apply to land in all districts except the M-DT district whenever land is subdivided or re-subdivided to create, change, or establish the boundaries of parcels for development or redevelopment, unless this chapter provides an exception.

(2) In the M-DT district, all subdivisions shall comply with the requirements of the regulating plan and other applicable standards in section 29-5.1, including but not limited to requirements for blocks, through connectivity, intersections, terminating streets, alleys, and sidewalks, and shall also comply with the M-DT district recommended street cross-sections in appendix A to the greatest degree practicable. If the requirements of section 29-4.2 conflict with the provisions of this section 29-5.1, the provisions of section 29-4.2 shall apply. If the provisions of section 29-4.2 are silent on a topic addressed by this section 29-5.1, the provisions of this section 29-5.1 shall apply.

(b) Avoidance of sensitive areas. Except under approved special safeguards, land shall be neither subdivided nor developed, where there is a finding by the council that a proposed subdivision or development poses a threat to the safety, health and general welfare of inhabitants of the land or surrounding areas due to flooding, improper drainage, steep slopes, rock formations, adverse earth formations, topography, utility easements or other adverse conditions. Portions of the proposed subdivision or development that cannot be developed without damage to sensitive areas shall be set aside for such use as shall not pose an undue hazard to life and property.

(1) Land analysis map.

(i) Each application for subdivision or re-subdivision of a land area of five (5) acres or more, either alone or contiguous with another subdivision by the same applicant, shall prepare and submit a land analysis map identifying sensitive lands to be protected from development. Such map shall

be provided at the time of concept review for property proposed to be preliminarily platted regardless of the parcel size. In preparing such land analysis map, those areas shown on the future land use map of the city's comprehensive plan as "sensitive" shall be identified as well as other areas which through reasonable investigation should be known to be sensitive areas.

(ii) The land analysis map shall identify, as sensitive lands to be protected from development, all of the following:

(A) Stream corridors, which shall include all land from top-of-bank to top-of-bank of any waterway, shown as a solid blue or dashed blue line on the corresponding USGS 7.5 minute quadrangle map and further defined within chapter 12A of the City Code;

(B) Steep slopes, which shall include all land with a natural undisturbed average vertical slope of twenty-five (25) percent or more and height of ten (10) feet or greater, measured from top-ofslope to foot-of-slope, plus an additional ten (10) feet or additional setback as required by chapter 12A as it relates to stream buffers; and

(C) Any lands designated as floodway on the Flood Insurance Rate Maps (FIRMs) for the City of Columbia or FIRMs for unincorporated Boone County if the subject subdivision or resubdivision is not inside the city's boundary. In instances where the designated floodway has been modified or amended by action of the Federal Emergency Management Agency (FEMA) and is not reflected on the adopted FIRM Maps, proof of such modification or amendment shall be provided at the time of land analysis map submission and shall be recognized as the official boundary of the floodway.

(iii) The land analysis map shall further identify that portion of a site located within the flood plain (i.e. flood fringe) shown on the Flood Insurance Rate Maps (FIRMs) for the City of Columbia or FIRMs for unincorporated Boone County if the subject subdivision or resubdivision is not inside the city's boundary. Such areas shall not be considered restricted from development; however, they are subject to the development standards of the FP-O (floodplain overlay) district. Preservation and avoidance of such areas in the course of site development may qualify for a "preservation bonus" in accordance with the provisions provided below.

(2) Avoidance of sensitive lands. The applicant shall lay out the subdivision or re-subdivision so that:

(i) To the greatest degree practicable, no lot intended for development shall include land features designated as sensitive lands, as indicated in section 29-5.1(b)(ii), unless such inclusion is supported by:

(A) Written and graphical documentation that avoidance was not possible and the corresponding code provision(s) requiring such inclusion, to meet the regulatory requirements of this chapter, are cited, and

(B) Written certification by a Missouri Licensed Professional Engineer that such inclusion will not pose a threat to the health, safety, and welfare of the inhabitants of the surrounding land. (ii)

If any lot intended for development includes designated sensitive lands, construction of permanent structures shall be restricted to a designated building envelope that does not include any designated sensitive land areas. The sensitive lands on the lot shall be permanently protected by designation within a preservation easement or located on a separate common lot; and

(iii) Street crossings of sensitive land areas are minimized to the maximum extent practicable.

(3) Adjustment of minimum lot sizes. If the avoidance of designated sensitive lands except floodways results in a subdivision containing fewer buildable parcels than would have been allowed if sensitive lands were not avoided, the applicant may adjust the minimum lot size and/or lot width in the subdivision by up to fifteen (15) percent to recapture as many lots as would have been possible if sensitive lands were not avoided. This reduction shall not be combined with any other lot area or width reduction permitted elsewhere within this chapter.

(4) Preservation bonus—Floodplain/flood fringe avoidance. If a property owner or developer chooses to voluntarily restrict subdivision development from those areas shown on the land analysis map as floodplain/flood fringe, in addition to those areas identified as "sensitive features", the following shall be permitted:

(i) For developments zoned R-1, R-2, R-MF, M-OF, and M-N, where single- or two-family lots are created, minimum lot size and/or lot width may be reduced up to twenty-five (25) percent of that required by this chapter. This reduction shall not be combined with any other lot area or lot width reduction permitted elsewhere within this chapter.

(ii) For developments zoned R-MF, M-OF, M-N, M-C, or IG parking may be reduced by a maximum of ten (10) percent from that required by Table 4.3-1, unless otherwise restricted within this chapter.

(c) Streets.

(1) Street improvements generally.

(i) Streets, curbs and gutters shall be improved to comply with the standards in this chapter, the adopted city street and storm sewer specifications and design standards, and all design standards and specifications promulgated by the director of public works or adopted by the council, and in accordance with the final construction plans required to be approved prior to final plat approval.

(ii) Notwithstanding any provisions of this chapter or standards listed in subsection (i), if land is subdivided in the R-1 district or subdivided for single-family residential development in a PD district, and the minimum size of each lot is two (2) acres or more in size:

(A) The subdivision shall not be required to install sidewalks along roadways classified below collector status, or curbs or gutters, but may manage street-related stormwater through the use of bioswales or natural areas designed to allow infiltration of stormwater into the soil, rather than transmitting it to a piped stormwater system.

(B)

The director of public works may approve alternative construction standards for road surfaces and lane widths to reflect anticipated low traffic volumes and preserve rural character while protecting traffic safety and emergency service access.

(2) Responsibility for improvements costs. Except as otherwise provided herein, the costs of construction of required public improvements shall be paid by the applicant. It is the policy of the city to participate in or contribute only to certain additional costs of construction of major thoroughfares over and above the normal costs of local standard streets, when streets are designated at higher standards by the city. Such participation, and its timing, is not mandated and is solely at the discretion of the council, according to the needs of the community.

(3) Connectivity.

(i) Streets. Streets shall comply with the following standards:

(A) Local streets shall be designed to provide convenient and safe access for all modes of transportation, including bicycles and pedestrians, to all properties and to permit efficient drainage and utility systems.

(B) Through streets shall be designed as shown in Figure 5.1-1. The street alignment shall be determined at the time of platting, but the plat shall include at least the number of direct connections between arterials or collectors as shown in Figure 5.1-1. If the provisions of section 29-5(c)(1)(ii) regarding large lot residential development apply, then only the provisions of Figure 5.1-1 applicable to arterial and collector streets apply.

Figure 5.1-1. Required street layouts

(C) As an alternative to complying with the through street requirements of subsection (B) above, the applicant may prepare a connectivity index calculation that divides the number of street segments within the plat (i.e. sections of streets between intersecting streets) by the number of intersections within and at the boundaries of the plat to achieve a connectivity index of 1.65 or more. An example of a connectivity index calculation is shown in Figure 5.1-2 below.

(D) Straight streets more than eight hundred (800) feet long shall be avoided to discourage speeding, but may be approved by the director in the event a shorter street is impracticable due to terrain or other unique site constraints.

(E)

Individual local residential street segments should serve no more than thirty (30) dwelling units without additional street connections unless otherwise permitted for by this chapter.

(F) Cul-de-sacs and loop (U-shaped) streets should not exceed three hundred (300) feet in length but may be approved in unique circumstances to avoid steep slopes, major creeks, floodplains, wetlands and other sensitive environmental areas.

Figure 5.1-2: Connectivity Index

(G) Where a subdivision abuts or contains an existing arterial street or highway having limited access, lots abutting such roadways shall be arranged such that the rear yards abut the arterial street or highway, or access to such lots is provided from an adjacent frontage road or other street design which provides for adequate protection of residential properties, affords separation of through and local traffic, provides a safe route for all modes of transportation, and provides for suitable access to the property involved.

(H) When a new subdivision adjoins unplatted or undeveloped land, the new streets shall be carried to the boundaries of such land unless vehicular access is unnecessary or inappropriate due to existing or proposed development with incompatible traffic generation on the adjacent platted or unplatted lands or designation of sensitive areas. A temporary turnaround approved by the director of public works shall be installed at the point where the properties connect, except when the terminus of the street is less than one hundred fifty

(150) feet from an intersecting street right-of-way.

(I) Where street connections to adjoining land are not provided and there is a need for nonvehicular public access to a school, park, trail or other area or use, the city may require the dedication and improvement of a green space access easement or trail easement to serve the needs of the proposed development. Whenever such public improvements are required, the city shall accept ownership and maintenance in the form of fee title or an easement, as determined in the best interest of the public.

(J) Permanent terminal streets shall not be longer than seven hundred fifty (750) feet, measured from the center of any cul-de-sac to the right-of-way line of the nearest through street from which it derives.

(K) Four-way intersections of local streets will be platted and constructed according to the standards set forth in appendix A unless otherwise approved by the director of public works.

(ii) Blocks. Streets shall intersect at intervals not exceeding six hundred (600) feet or less than two hundred fifty (250) feet. Blocks shall have sufficient depth to provide for two (2) tiers of lots of appropriate depth. The director may approve exceptions to block depth when blocks are adjacent to major streets, railroads, waterways, or other sensitive environmental areas (e.g., steep slopes, waterways).

(4) Widths.

(i) The right-of-way width required to be dedicated and the pavement width required to be constructed for streets shall comply with the standards in appendix A for each street classification.

(ii) Proposed subdivisions that include existing street right-of-way narrower than required by appendix A shall provide for dedication of additional right-of-way width along one or both sides of the street. Proposed subdivisions abutting only one side of such streets shall provide for dedication of additional right-of-way width to constitute one-half (½) of the right-of-way width required.

(5) Grades.

(i) The grades of streets shall comply with the standards and design criteria in appendix A.

(ii) Where it is impracticable to comply with the standards set forth in appendix A, written approval to deviate from the specific standards which cannot be met must be obtained from the director of public works, who shall make a determination as to whether the requested deviation is necessary and consistent with protection of the public and traffic safety.

(6) Curves. Curves shall comply with the design criteria in appendix A unless the director of public works determines that a more restrictive requirement is necessary to safeguard the public health, safety and general welfare from potentially hazardous street design.

(7) Alleys.

(i) Residential alleys shall be permitted in all residential districts.

(ii) Nonresidential alleys shall be provided in mixed use and special districts when off-street loading and parking are not otherwise provided.

(iii) The right-of-way width of an alley shall be twenty (20) feet and the pavement width shall be sixteen (16) feet, except in the M-DT district, where alley improvements and new alleys should be designed in accordance with the M-DT district alley cross-section in appendix A, when feasible.

(iv) When alleys intersect, the intersection right-of-way lines shall be rounded by a curve with a radius of at least five (5) feet in length.

(8) Transportation impact analysis. The city may require that a transportation impact analysis (TIA) be prepared as part of the approval process for any new development. An estimate of the trips generated by a proposed development will be completed to determine if a TIA is required. Any

proposed development that would produce one hundred (100) or more trips in and out of the development site at peak hour shall be required to submit a TIA in accordance with the provisions contained in the UDC Administrative Manual. The purpose of the TIA is to estimate the traffic impacts created by the new development on the surrounding street system. Any significantly adverse traffic impacts identified in the TIA must be mitigated by the applicant.

(d) Sidewalks.

(1) Applicability.

(i) The following standards apply to any subdivision that receives final plat approval after the effective date of this chapter and any subdivision platted before 2001 that is less than twenty-five

(25) percent built-out. Any subdivision platted before 2001 and built-out by twenty-five (25) percent or more shall complete construction in accordance with the sidewalk standards in place at the time of final plat approval.

(ii) Undeveloped lots shown on subdivision plats that received final approval before January 1, 2001 shall install sidewalks in compliance with the city street and storm sewer specifications and design standards now applicable or later issued by the director of public works or adopted by the council, along their respective street frontage(s), unless otherwise specified in this chapter.

(2) Standard requirements.

(i) No permit shall be issued for the construction of a new building or additions to buildings on property located on an arterial or collector street unless:

(A) A sidewalk exists adjacent to the property along the arterial or collector street; or

(B) The plans for the building provide for the construction of such a sidewalk; or

(C) Otherwise specified as a note on the plat or in a performance contract between the developer and the city.

(ii) The requirements of subsection (i) do not apply to construction of accessory buildings.

(iii) No certificate of occupancy shall be issued for any building described in subsection (i) if the building plans provide for construction of a sidewalk along an arterial or collector street unless the sidewalk has been constructed or the property owner has provided a bond, letter of credit or other instrument acceptable to the director of public works guaranteeing construction of the sidewalk within six (6) months of issuance of the certificate of occupancy.

(iv) Sidewalks are not required along streets classified as freeways.

(v) Sidewalks shall be required on both sides of expressways and frontage roads unless the council determines that potential or existing pedestrian volumes do not necessitate sidewalks to safeguard the public health, safety and general welfare.

(vi) Sidewalks shall be constructed within all pedestrian easements and on both sides of all internal streets and on the abutting side of any adjacent street unless otherwise specified in this UDC. (vii)

A sidewalk shall not be required along a residential access street that is less than two hundred fifty (250) feet in length and terminates in a cul-de-sac. Sidewalks shall be a minimum of five (5) feet in width along all other streets.

(viii) Where a final plat creates a common lot or a non-buildable lot, a sidewalk shall be constructed along the portion of each street abutting the lot at the same time the abutting street is constructed or within three (3) years of such lot being created when such lots abut an existing street. No street shall be accepted for public maintenance upon which a common lot or nonbuildable lot fronts without first having such sidewalk located adjacent to such lot being installed. This subsection shall not apply to any subdivision that received final plat approval before January 1, 2006.

(ix) Sidewalks shall be constructed to comply with the standards contained in this section 29-5.3(d)(2) and with the city design standards and specifications established by the director of public works or adopted by the council.

(x) Whenever a permit is issued to construct, reconstruct, repair, alter or grade any sidewalk curb, curb cut, driveway or street, handicapped ramps shall be required to be installed in accordance with design standards included in the city's standard plan and specifications at all curb and driveway crossings to be constructed, reconstructed, repaired or altered; provided, that the director of public works may waive said requirement if he determines that requirement of handicapped ramps is impractical under all the circumstances.

(xi) The council may require a sidewalk to be constructed to standards higher than the minimum standards of this section 29-5.1(d)(2) provided that the city compensate the property owner for the additional cost of constructing the sidewalk.

(e) Bike lanes and pedways. Bicycle lanes and pedways shall be designed and constructed in accordance with appendix A and all applicable design standards and specifications promulgated by the director of public works or adopted by council.

(f) Lots.

(1) Lot arrangement. Lots shall be arranged to comply with building permit requirements of this chapter as to minimum size and width in the zone district where the property is located, as well as access, relation to topography, provision of utility service, or other conditions specified in this chapter or in other standards and specifications adopted by the city. Lots in subdivisions that qualify for the solar access density bonus in section 29-4.1(b)(2) or the cluster subdivision density bonus in section 29- 4.1(b)(3), and lots that are organized to avoid sensitive lands as described in section 29-5.1(b) shall comply with the minimum lot size and width in the zone districts where the lots are located, as adjusted by the provisions of those sections of this chapter.

(i) Corner lots. Corner lots shall have sufficient width for compliance with front and side yard building setback requirements set forth in this chapter.

(ii) Side lot lines. Side lot lines should generally be at right angles to straight streets and radial to curved streets.

(iii) Tier lots (aka flag lot or stem lot). The commission may allow tier lots on previously unplatted land when the following criteria are met:

(A) Tier lot design is the only feasible means to access lots due to extreme topographic conditions;

(B) The stem of a tier lot, that is, the portion of the lot which connects its required yard area and its buildable area with its public access, shall not be less than twenty (20) feet nor more than fifty-nine (59) feet in width and not shorter than twenty-five (25) feet nor longer than two hundred fifty (250) feet in length and may not be included within any required yard area set forth in this chapter; and

(C) The allowance of tier lots will not endanger the public health, safety and general welfare.

(iv) Frontage.

(A) Except as otherwise provided and specifically authorized under this chapter, all lots, tracts or parcels shall have actual frontage upon a street, which provides direct vehicular access to the lot. In context sensitive situations (e.g., topography, existing or proposed development patterns) where actual street frontage is not feasible, the director may permit a lot with an irrevocable access easement suitable to the city counselor, or designee, rather than actual street frontage, if the public health, safety, and general welfare is not compromised.

(B) Common lots for the purposes of storm water management features may be created without having actual street frontage provided that such lots have an established means of ingress/egress by an irrevocable access easement suitable to the city counselor, or designee.

(C) Common lots created for recreational purposes (active or passive) shall have a minimum of twenty (20) feet of street frontage. Such frontage may be actual lot frontage or provided through an irrevocable access easement suitable to the city counselor, or designee.

(D) Newly platted or re-subdivided non-residential lots that propose direct driveway connection to an arterial or collector street shall have a minimum of three hundred (300) feet of frontage along the street right-of-way. Shared access for parking and driveways may be required to promote internal development connectivity.

(v) Shape. Lots in mixed use or special zone districts shall not be created with protrusions, extensions or stems of less than thirty (30) feet in width.

(2) Lot access.

(i) Each lot shall have access allowing vehicles, pedestrians, and bicycles to pass from a public street directly onto the lot, or from a public street to the lot over an irrevocable access easement approved by the city counselor, or designee.

(ii) A maximum of thirty (30) lots or units shall be permitted to be accessed from a single point of ingress/egress unless otherwise specified by the most current adopted edition of the International Fire Code or authorized by the City of Columbia Fire Department. (iii)

Private residential driveways are prohibited on arterial or collector streets unless the director determines that no alternative access is practicable.

(iv) Non-residential driveway spacing shall conform to the provision of the most current edition of the Missouri Department of Transportation Access Management Guidelines or access management standards promulgated by the city.

(v) Streets that dead-end or "stub" into property that is adjacent to the property being subdivided shall not count as a second access until such time as the dead-end or "stub" street is connected to a through street and constructed to city standards.

(3) Lot lines. No building or structure shall be constructed across an existing lot line, except surface parking areas when such surface parking area is not prohibited from being constructed across an existing lot line by any other section of the city code.

(4) Lot combination. No lot in any existing subdivision may be combined with another lot without complying with the requirements of section 29-5.2.

(g) Public improvements.

(1) Standards and specifications. All required public improvements, including but not limited to streets and utilities, shall be installed or constructed in accordance with the procedural requirements in section 29-5.2, or in related public improvements standard specifications or policies established by the city department or other entity responsible for the design, operation, or maintenance of that type of improvement.

Upon notice that the improvements have been completed in accordance with the city's requirements, the designing engineer shall, under his seal and signature, submit as-built tracings for the street, storm sewer and sanitary sewer construction.

(2) Drainage and storm sewers.

(i) Flood-prone areas. Any portion of land being subdivided that is located within the limits of maximum flooding of the one hundred (100) year flood, as determined by the Boone County Digital Flood Insurance Rate Map (DFIRM), released March 17, 2011, and amendments to that map on file with the director, shall be developed so as not to endanger the health, safety and general welfare of the inhabitants of the city, and in compliance with the provisions of this chapter.

(ii) Storm sewers. Storm sewers with curbs and gutters shall be provided for lots unless the director of public works approves open channels with design features, such as vegetated swales and check dams to reduce runoff velocity and allow infiltration. Sidewalks and pedways shall not be located between the street and open channel. Improvements shall conform to standards contained in the city street and storm sewer specifications and design standards, and the city storm drainage standards, and all applicable design standards and specifications promulgated by the director of public works or adopted by the council.

(iii)

Driveways across drainage features. Driveways that cross drainageways or ditches, to connect to public streets, shall be constructed as required by the director of public works to protect traffic safety and avoid traffic congestion.

(iv) Streets crossing streams. Streets that cross streams shall be designed and constructed to minimize the disruption to the stream channel and buffer zone. Streams should be crossed only when necessary to connect the street network.

(3) Street trees. Notwithstanding the provisions of section 29-4.4(b), installation of street trees shall comply with the provisions of section 29-4.4(d)(2).

(4) Utilities. Utilities, including but not limited to water, sewer, natural gas, electric and telephone lines, and fire hydrants, shall be provided to lots in accordance with standards and specifications governing the construction and installation of such utilities adopted by council or promulgated by the city departments or utility companies responsible for those utilities.

(5) Easements.

(i) Generally. Easements for public and private utilities shall be provided abutting all street right-ofway and in other locations in accordance with facility requirements and design standards. To the maximum extent feasible, utilities shall be located in designated easements and not in the street right-of-way.

(ii) M-DT district easements. The dedication of easements abutting rights-of-way in the M-DT district may conflict with buildings constructed at the required building line (RBL). For property in the M- DT district, the dedication of a ten (10) foot utility easement along right-of-way is not mandatory; however, may be required by the city if it is found that there is insufficient area within existing street or alley rights-of-way to allow for the adequate provision of current and future city services and facilities.