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The Planning Commission shall impose the following general requirements and compel all subdividers to comply with the following principles of design in the layout of subdivision.
(A) Suitability of the land.
(1) Public agency approval. The Planning Commission shall not approve the subdivision of land, if, from adequate investigations conducted by all public agencies concerned it has been determined that the best interest of the public that the site is not suitable for platting and development purposes of the kind proposed.
(2) Land subject to flooding.
(a) Land subject to flooding and land deemed to be topographically unsuitable shall not be platted for residential occupancy, nor for other uses as may not be platted for residential occupancy, nor for the other uses as may increase danger to health, life or property or aggravate erosion or flood hazard. The land within the plat shall be set aside for the uses as shall not be endangered by periodical or occasional inundation or shall not produce unsatisfactory living conditions.
(b) If a stream flows through or adjacent to the proposed subdivision, the plat plan shall provide for an easement or right-of-way along the stream for a floodway. For the smaller stream the plan shall also provide for channel improvement to enable them to carry all reasonable floods within banks. The lowest floor elevations of houses shall be high enough to be free from the danger of flooding. The floodway easement shall be wide enough to provide for future enlargement of the stream channel as adjacent areas become more highly developed and runoff rates are increased.
(c) Fill may not be used to raise land within areas subject to flood unless the fill proposed does not restrict the flow of water or unduly increase flood heights.
(3) Safety and adequacy. The Planning Commission shall require the developer to obtain an opinion from a state licensed engineer as to safety and adequacy of any fill to be placed on land subject to flood. In applying these provisions, land subject to flood and floodways shall be described as follows.
(a) Floodway is the channel of the watercourse and these portions of the adjoining floodplains which are reasonably required to carry and discharge the flood waters.
(b) Land subject to flood is of two types. One type is the area along streams, watercourse, and low areas identified as having special flood hazard by the Federal Emergency Management Agency (FEMA). Second, land lying within 15 feet of the top of the bank of the channel (measured horizontally) along small streams and drainage channels unless the developer demonstrates adequately that the property is free from danger of inundation by the 100-year flood, or that adequate remedial measures have been taken to safely accommodate the 100-year flood.
(B) Drainage system standards. The following standards shall be addressed in designing and constructing subdivision drainage systems:
(1) Curb and gutter system:
(a) Curb and gutter drainage systems shall be allowed;
(b) The curb and gutter system shall be designed to handle a 25-year storm.
1. The systems shall be designed so that there will be no water in roadway, six feet on either side of the center line, with a 25-year storm.
2. The design engineer shall show on his or her drainage plan that the water cross-sectional area of the curb and gutter street at all points of evacuation is not in violation of the water no closer than six feet from center line standard for a 25-year design storm.
(c) The curb and gutter system shall be contained within the right-of-way. The drop boxes and other required infrastructure will be contained either in the right-of-way or easements designated for this purpose;
(d) The curb and gutter system shall consist of rolled or vertical-face curb. However, rolled curb is normally more desirable;
(e) The curb and gutter system may be constructed of either concrete or asphalt. However, both types must be back-filled so that the shoulders are flush with the back top edge of the curbing; and
(f) Curb and guttering system shall have the following dimensions:
1. Approximately two feet from front of curb to back of curb (both types);
2. Approximate depth (at deepest point) six inches, (both types);
3. Approximately six inches thick where it abuts the roadway (front of curb), and 12 inches thick where it abuts the earthen shoulder (rear of curb); and
4. The curb and gutter system shall blend smoothly into the roadway.
(2) Ditch lines:
(a) Ditch lines shall be allowed as drainage systems;
(b) All ditches and driveway tiles shall be designed to handle a 25-year storm;
(c) The ditch line shall be cut so that it is deep enough to have the required driveway tile plus six inches of cover;
(d) All ditches along local streets shall be contained in an 11-foot area of right-of-way which starts at the back of the shoulder and ends at the front of the sidewalk. Ditch lines along collector streets shall be contained in a 14-foot area of the right-of-way;
(e) The sides of a ditch shall have a maximum slope of two to one unless they are paved or covered with rock or stone or stabilized in some manner approved by the City Engineer.
1. Ditch lines with side slopes of three to one or less may be vegetated by normal seeding procedures.
2. Ditch lines with side slopes between three to one and two to one shall be vegetated by sodding.
(f) All ditch lines which will have a water velocity of over five feet per second with a 25- year storm, shall be covered with a hard surface, or stabilized in some manner approved by the City Engineer;
(g) All vegetated ditches shall have the type of vegetation and the method of planting approved by the City Engineer. Note: the type and method of vegetation will change with the side slope grade and weather conditions;
(h) The city shall not release the financial security of a development until the ditch has been properly cut and vegetated; and
(i) Standardized flared head walls shall be required where two or more ditch lines are channeled into a culvert or when a ditch line deflects at an angle of 135 degrees or less.
(3) Driveway culverts:
(a) If ditches are being used then the developer's engineer shall size the driveway culverts for all lots. The tiles shall be designed to handle a 25-year storm;
(b) All driveway tiles shall have a minimum of eight inches of total cover (earth plus pavement);
(c) The flow-line of all driveway tiles shall be placed at the same grade as the ditch line;
(d) If head walls are used then the driveway culvert shall be total of five feet (two and five tenths foot on either side) wider than the apron pavement, and shall have six inches of cover. The culvert shall be flush with the head wall. The head wall material and construction design shall be approved by the City Engineer;
(e) If head walls are not used then the driveway culvert shall be eight feet longer four feet on either side than the apron pavement. The first two feet of pipe on both sides of the apron shall have six inches of fill on top of it, after this point the pipe shall be covered with fill to at least a three to one slope;
(f) The type of driveway culvert shall be approved by the City Engineer. The diameter of the drainage tile shall be large enough to allow for the unrestrictive flow of storm water run-off (minimum diameter of 12 inches required); and
(g) Before driveway swales are incorporated into any drainage plan, prior approval of the City Engineer will be obtained. Driveway swales shall not exceed six inches in maximum depth nor drastically vary from the contour of the ditch line. A connecting three feet wide surfaced channel may be required between driveway swales to facilitate the movement of run-off water.
(4) Sidewalk culverts:
(a) When a sidewalk crosses a ditch line, a culvert or other appropriate water channel shall be required;
(b) Sidewalk culverts shall have at least the same water carrying capacity as the driveway culverts;
(c) The culvert shall be set in the bottom of the ditch line and shall have at least six inches of cover (fill plus pavement);
(d) The ends of the culvert shall be protected in a manner approved by the City Engineer;
(e) The culvert shall be long enough to clear both ends of the sidewalk. The exact length will depend on the type of end covering or protection that will be used; and
(f) Any time the tip of the sidewalk is greater than 24 inches from the bottom of the ditch line, a railing or some other type of protective device shall be installed.
(5) Roadway culverts:
(a) All culverts shall be designed to handle a 25-year storm;
(b) All culverts over 15 inches in diameter shall have both ends protected with a hard surface: head walls or concrete collars may be used.
1. Head walls may have a vertical face, the culvert shall be flush with the head wall. The material and design of the head wall shall be approved by the City Engineer.
2. Concrete collars shall have end slopes of a minimum of two to one. The collar shall be back filled with earth, and the earth stabilized and vegetated. The collars shall have a footer which is below the grade of the bed of the stream or ditch. The material and design of the collar shall be approved by the City Engineer.
(c) All culverts shall have a minimum of 12 inches of total cover, to be measured from the top of the culvert to the top of the pavement;
(d) The bottom of the culvert shall be at the same grade as the bottom of the ditch line; and
(e) All culverts over 24 inches shall have protective end grates. The grates shall be so designed so that they allow the smooth flow of water but will stop the flow of debris or other large objects through the culvert.
(6) Retention of storm water: all developments shall provide for the retention of 100% of excessive storm water run-off resulting from the development. Retain storm water at 100-year storm and release at 15-year storm (see Chapters 154 and 155 for calculation methods). Any proposed development that the ultimate receiver is a flood prone area shall not be permitted unless the proposed development can store 100% of a four-inch storm with a 100% run-off factor.
(a) The retention may be either on-site or off-site.
(b) The retention shall insure that no downstream property owners, water courses or sinkholes will receive storm water run-off at a higher peak flow rate than they were prior to the development.
(c) Excessive storm water run-off shall include the increase in storm water resulting from:
1. An increase in the impervious surface;
2. Changes in soil absorption due to the development; and/or
3. Filling of existing drainage, sinkhole or storage areas.
(d) The retention area shall be calculated for the total development. A development may have as many or as few retention areas as is necessary to retain the required amount of water.
(e) The retention areas may be designed as either semi-dry or wet retention areas. The Commission may require a protecting barrier and/or safety devices for any retention area they feel will be a threat to the health or safety of citizens.
(f) If the retention areas are to be vegetated then they shall have side slopes not steeper than two to one. Covered areas may have steeper slopes.
(g) All retention basins as well as the inflow and outflow channels shall be contained within drainage easements and clearly illustrated on both the preliminary and final plats.
(h) The city shall not release a developer's final security until the storm water retention system is found to be in compliance with these standards by the City Engineer. A developer may request that the Planning and Zoning Commission approve a variance to this standard. The Planning and Zoning Commission may consider granting variances to retain less than 100% of the storm water created by the development if one or more of the following conditions exist:
1. It is found that the increase in water flow will in no way be injurious or detrimental to the downstream property owners, water courses and/or sinkhole basins;
2. The developer has the expressed written and legal consent from the ultimate downstream property owner, who will receive the discharge, to channel the total storm water flow onto their property. The flow shall be contained in a recorded drainage easement; and/or
3. The increase in storm water will not significantly impact or adversely affect the downstream receivers.
(7) Drainage easements and grading: following are the standards for the development of drainage easements.
(a) All developments shall provide adequate areas to house the flow of the surface water, the areas shall be contained within a drainage easement.
(b) All drainage easements shall be graded so that they will carry the intended water flow. No partial grading shall be allowed. If the design of a drainage system calls for an easement to be partially housed on adjacent property the easement shall be recorded and graded prior to the city's acceptance of the subdivision.
(c) All lots shall be graded so that they will drain toward the platted drainage easements.
(d) The city shall not release a developer's financial security until the drainage easements have been found to be in compliance with these standards by the City Engineer.
(e) Builders shall be responsible for keeping drainage ways open or for creating ones the developer has given them responsibility for.
(8) Sinkhole drainage: sinkholes may be used as a means of on-site disposal of storm water if the Commission and Council find that this will not significantly increase the chance or frequency of subsidence or flooding in the general area. However, sinkhole drainage systems shall be designed and constructed in accordance with the following standards.
(a) The drainage and storage area shall be contained within an easement.
(b) The storm water has direct access to an underground passageway or stream via a rock, crevice or a pipe.
(c) Any exposed crevice or pipe shall have a grated end.
(d) Provisions are provided for the maintenance of the sinkhole drainage/storage area. Responsibility for maintenance shall be clearly indicated.
(C) (1) Streets.
(a) The widths and locations of all streets in a proposed subdivision shall conform to state standards and local plans.
(b) Street extensions:
1. The street layout of the proposed subdivision shall provide for the continuation of projection of streets already existing in areas adjacent to the area being subdivided unless the Planning Commission deems the continuation or extension undesirable for specific reasons of topography or design;
2. Where, in the opinion of the Planning commission, it is desirable to provide street access to adjoining properties, proposed streets shall be extended by dedication to the boundaries of the properties. Where the Planning Commission deems it necessary, the dead-end streets shall be provided with a temporary turnaround having a radius of at least 40 feet; and
3. The street system for the proposed subdivision shall provide for extending existing streets at the same or greater width, but in no case shall a street extension be of less width than the minimum width required in these regulations for a street in its category.
(c) The minimum width of right-of-way, measured from lot line to lot line, shall be as shown on local street plans, or if not shown on the plans, shall not be less than follows:
1. Arterial streets and highways: 80 feet as may be required. Arterial streets and highways are those to be used primarily for fast or heavy traffic. Minimum pavement: 22 feet or as required by KDOT;
2. Collector streets: 60 feet. Collector streets are those which carry traffic from minor streets to the major system of arterial streets and highways and include the principal entrance streets of a residential development and street for major circulation within such a development. Minimum pavement: 22 feet;
3. Minor residential streets: 40 feet. Minor streets are those which are used primarily for access to the abutting residential properties and designed to discourage their use by through traffic. Minimum pavement: 18 feet;
4. Marginal access streets: 40 feet. Marginal access streets are minor streets which are parallel to and adjacent to arterial streets and highways; and which provide access to abutting properties and protection from through traffic. Minimum pavement: 18 feet;
5. Dead-end streets (cul-de-sac): 100 feet. Culs-de-sac are permanent dead-end streets or courts not to exceed 600 feet or 15 dwelling units, designed to have one end permanently closed. At the closed end, the turnaround radius must be at least twice the right-of-way leading into the cul-de-sac. Minimum pavement: 18 feet;
6. Loop streets: 40 feet. Loop streets are streets open at both ends and connected to only one residential street with a maximum length of 1,200 feet or 25 dwelling units. Minimum pavement: 18 feet;
7. Alleys (if approved): 20 feet. Alleys are minor public ways used primarily for service access to the back or side properties otherwise abutting on a street. Minimum pavement: 18 feet;
8. Through proposed business areas, street widths shall be increased ten feet on each side if needed to provide parking without interfering with normal traffic movements; and
9. In cases where topography or other physical conditions make a street of the required minimum width impractical, the Planning Commission may modify the above requirements.
(d) Additional width on existing streets: subdivisions that adjoin existing streets shall dedicate additional right-of-way to meet the above minimum street width requirements.
1. The entire minimum right-of-way width shall be dedicated where the subdivision is on both sides of an existing street.
2. When the subdivision is located on only one side of an existing street, one-half of the required right-of-way width, measured from the center line of the existing roadway, shall be dedicated.
3. Dedication of one-half of the rights-of-way for proposed streets along the boundaries of land proposed for subdivision shall be prohibited.
1. Streets shall intersect as nearly as possible at right angles;
2. Street curb intersections shall be rounded by radii of at least 20 feet. When the smallest angles of street intersection are less than 60 degrees, the Planning Commission shall require curb radii of greater length. Wherever necessary to permit the construction of a curb having a desirable radius without reducing the sidewalk at a street corner to less than normal width, the property line at the street corner shall be round or otherwise set back sufficiently to permit the curb construction; and
3. No lot or other parcel of land which abuts on and has access to either a collector or a minor street shall have a service drive, 75 feet of the right-of-way of any street which intersects the arterial street on the side on which the lot or parcel is located.
(f) Street curvatures.
1. Tangent. A tangent at least 100 feet long shall be introduced between reverse curves on arterial and collector streets.
2. Horizontal. Where a deflection angle of more than ten degrees in the alignment of a street occurs, a curve of reasonably long radius shall be introduced. On streets 60 feet or more in width, the centerline radius of curvature shall be not less than 300 feet; on other streets, not less than 100 feet.
3. Vertical curves. Every change in grade shall be connected by a vertical curve constructed so as to afford a minimum sight distance of 200 feet, the sight distance being measured from the driver's eyes, which are assumed to be four and one-half feet above the pavement. Profiles of all streets showing natural and finished grades drawn to a scale of not less than one inch equals 100 feet horizontal, and one inch equals 20 feet vertical, may be required by the Planning Commission.
(g) 1. Street grades, elevations and drainage.
2. Street grades shall not exceed the following.
a. The Planning Commission shall not approve streets which will be subject to inundation or flooding. All streets must be located at elevations which will make them flood free in order that portions of the subdivisions will not be isolated by floods. Where flood conditions exist, the Planning Commission shall require profiles and elevations of streets in order to determine the advisability of permitting the proposed subdivision activity.
b. All streets shall be designed so as to provide for the discharge of surface water from the pavement and from the right-of-way by grading and drainage. For adequate drainage, the minimum street grade shall not be less than one-half of 1%.
c. Where it is the opinion of the Planning Commission that water cannot be adequately discharged by surface drainage, the Planning Commission may require the installation of a storm sewer system. Fill may be used in areas subject to flooding in order to provide flood-free street if the fill does not unduly increase flood heights. Drainage opening shall be designed so as not to restrict the flow of water and thereby unduly increase flood heights.
(h) Marginal access streets: where the proposed subdivision abuts upon or contains an existing or proposed arterial street or highway on which traffic volumes and vehicular speeds warrant special safety considerations, the Planning Commission may require that marginal access streets be provided in order that no lots will front on the existing or proposed arterial street highway.
(i) Street jogs with center line offsets of less than 125 feet shall not be permitted.
(j) Dead-end streets (culs-de-sac): minor terminal or dead-end streets or courts which are designed so as to have one end permanently closed shall not be longer than 500 feet and shall be provided at the closed end with a turnaround having a radius at the outside of the pavement of at least 40 feet and a radius at the outside of the right-of-way of at least 50 feet.
(k) Street names:
1. Proposed streets which are obviously in alignment with others already existing named, shall bear the names of existing streets; and
2. In no case shall the name for proposed streets duplicate existing street names, irrespective of the use of the suffix street, avenue, boulevard, driveway, place or court. Through its index list of street names on file the Planning Commission can assist the subdivider in avoiding duplication.
(l) Private streets and reserve strips:
1. There shall be no private streets platted within a subdivision unless it shall be clearly shown that a road is intended to be reserved and that no dedication is intended by the developer; and
2. There shall be no reserve strips in a subdivision except where their control is definitely vested in the city or county under conditions approved by the Planning Commission as authorized in these regulations.
(m) Alleys shall be provided to give access to the rear of all lots used for business and industrial purposes. Alleys shall not be provided in residential blocks except in cases where the subdivider produces evidence of the need for alleys which is satisfactory to the Planning Commission.
(a) Length. Blocks shall not be less than 400 feet nor more than 1,200 feet in length, except as the Planning Commission consider necessary to secure efficient use of land or desired features of street pattern. In blocks over 800 feet in length, the Planning Commission may require one or more public crosswalks of not less than ten feet in width to extend entirely across the block and at locations deemed necessary.
(b) Width. Blocks shall be wide enough to allow two tiers of lots of minimum depth. However, where this would require lots to front on an arterial street or highway or where topographical conditions or the size of the property prevent two tiers or lots, the Planning Commission may approve a single tier of lots of minimum depth.
(1) Relationship to streets. All lots shall front on a public street or road for a minimum distance of 75 feet except that lots which front on the turnarounds of permanent dead-end streets shall front on the turnarounds for a minimum distance of 40 feet.
(2) Arrangement. Each lot in a subdivision shall contain a building site determined to be free from the danger of flooding. Wherever practical, side lot lines shall be at right angles to straight street lines and radical to curved street lines.
(3) Dimensions. The size, shape and orientation of lots shall be such as the Planning Commission deems appropriate for the type of development and use contemplated.
(a) Lot dimensions within the corporate limits of the city shall conform to the requirements of the City Zoning Ordinance, except that residential lots not served by public sewer shall be at least 75 feet wide at the building setback line and 15,000 square feet in area or the minimum lot width and area determined by the City (or County) Health Officer, whichever width and area are larger.
(b) In areas where no zoning ordinance is in effect, residential lots served by public sewer shall be at least 75 feet wide at the building setback line and 7,500 square feet in area.
(c) In areas where no zoning ordinance is in effect, residential lots not served by public sewer shall be at least 75 feet wide at the building setback line and 7,500 square feet in area.
(d) In areas where no zoning is in effect, residential lots not served by public sewer shall a have a minimum lot width at the building setback line and a minimum lot area as determined by the County Health Officer. However, in no case shall a lot not served by public sewer be less than 75 feet in width at the building setback line and less than 15,000 square feet in area.
(e) The minimum width and minimum area of residential lots to be served by individual private wells shall be determined by the County Health Officer after investigation of soil conditions, the proposed sewerage system, and the depth of ground water.
(f) When property is to be developed for commercial uses, it is usually most desirable that the design or layout scheme provide for an over-all or unified development such as a planned commercial or shopping center and that the platting of individual and separate lots for each business establishment be avoided.
(g) In industrial subdivisions, it is generally desirable that very rigid lot sizes and a very rigid arrangement of minor streets, railroad service tracks and service lines for utilities be avoided in order that the special needs of particular industries may more easily be met.
(h) Greater lot widths and lot areas than those specified above may be required for residential lots if, in the opinion of the City (or County) Health Officer, there are factors of drainage, soil conditions or other conditions to cause potential health problems.
(4) Building set back line. All the requirements shall conform to the City Zoning Ordinance. The building setback line shall not be located closer to the street right-of-way than a distance equal to one-half of the total width of the street right-of-way on which the building will front.
(5) Corner lots. Corner lots shall have sufficient extra width to meet the building setback lines established on both the front street and side street.
(6) Yard requirements. Yard requirements for residential subdivisions shall be in accordance with applicable requirements set forth in the City Zoning Ordinance.
(7) Flood hazards. Note: refer to earlier statements on land suitability, division (A) above.
(E) Off-street loading and parking facilities. In commercial and industrial subdivisions and in the portions of residential subdivisions reserved for commercial or industrial uses, the lots or parcels platted for commercial or industrial sites shall be large enough to provide for the off-street loading and unloading facilities and the off-street parking facilities required by the City Zoning Ordinance.
(F) Utility and drainage easements.
(1) Except where alleys are permitted for the purpose, the Planning Commission shall require easements at least 12 feet in width centered along all lines for poles, wires, conduits, storm sewers, sanitary sewers, gas mains, water mains, heat mains and other utility facilities. Where necessary or advisable in the opinion of the Planning Commission, similar easements shall be provided along side lot lines or across lots.
(2) If the Planning Commission deems it necessary for proper drainage within or through a subdivision, it shall require that a storm water easement or drainage right-of-way be provided.
(G) Community assets. In all subdivisions, due regard shall be shown for natural features such as large trees, unusual rock formations, and water courses; for sites which have historical significance; and for similar assets which if preserved will add attractiveness and value to the subdivision and to the community. The Planning Commission may prepare a list of all the features within its area of subdivision jurisdiction which it deems worthy of preservation.
(H) Conformance with zoning and other regulations. No final plat of land within the area of force and effect of an existing zoning ordinance will be approved unless it conforms with the ordinance. Whenever there is a discrepancy between the minimum standards set forth in these regulations and those contained in the Zoning Ordinance, Building Code or other official regulations, the highest standard shall apply.
(I) Public open spaces. Due consideration shall be given to the allocation of areas suitably located and of adequate size for playgrounds and parks for local and neighborhood use as well as for use as public service areas. Where a school, neighborhood park or recreation area or public access to water frontage, shown on an official map or in a plan made and adopted by the Planning Commission, is located in whole or in part in the applicant's subdivision, the Planning Commission may require the dedication or reservation of the open space within the subdivision up to a total of 10% of the gross area or water frontage of the plot, for park, school or recreation purposes.
(J) Large tracts or parcels. When land is subdivided into larger parcels than ordinary building lots, the parcels shall be arranged so as to allow for the opening of future streets and logical resubdivision.
(K) Storm sewers. See division (B) above.
(L) Water supply and sewerage connections. Where a development of a subdivision lies within the current service area of the community's water utility district, but immediate connection is not possible, the subdivider shall extend the appropriate size water and sewer lines to the development.
(2000 Code, App. A, Art. III)