CHAPTER 5
DESIGN STANDARDS
DESIGN STANDARDS
SECTION:
11-5-1: General Improvements
11-5-2: Lot Improvements
11-5-3: Roads
11-5-4: Drainage And Storm Sewers
11-5-5: Water Facilities
11-5-6: Sewerage Facilities
11-5-7: Sidewalks
11-5-8: Utilities
11-5-9: Public Uses
11-5-10: Preservation Of Natural Features And Amenities
11-5-11: Nonresidential Subdivisions
A. Conformance To Applicable Rules And Regulations: In addition to the requirements established herein, all subdivision plats shall comply with the following laws, rules and regulations:
1. All applicable statutory provisions;
2. The city zoning ordinance, building and housing codes, and all other applicable laws of the appropriate jurisdictions;
3. The comprehensive plan and capital improvements program of the city including all streets, drainage, systems and parks shown on the comprehensive plan as adopted;
4. The special requirements of these regulations and any rules of the health department and/or appropriate state agencies;
5. The rules of the Iowa department of transportation if the subdivision or any lot contained therein abuts a state highway;
6. The pertinent standards and regulations adopted by the city engineer and all boards, commissions, agencies and officials of the city;
7. Plat approval may be withheld if a subdivision is not in conformity with the guidelines, policies and purposes of these regulations established in section 11-1-4 of this title.
B. Self-Imposed Restrictions: If the owner places restrictions on any of the land contained in the subdivision greater than those required by the zoning ordinance or these regulations, such restrictions or reference thereto shall be required to be indicated on the subdivision plat and restrictive covenants which will be recorded with the county recorder.
C. Plats Near Municipal Boundaries: Whenever access to the subdivision is required across land in another local government, the city council shall require assurance from the city attorney that access is legally established and from the city engineer that the access road is adequately improved, or that a performance bond has been duly executed and is sufficient in amount to assure the construction of the access road. In general, plats should be laid out so as not to cross municipal boundary lines.
D. Monuments: The applicant shall place permanent reference monuments in the subdivision as required herein and as approved by a registered land surveyor in accordance with Iowa Code chapter 354.
E. Character Of The Land: Land which the city finds to be unsuitable for subdivision or development due to flooding, improper drainage, steep slopes, rock formations, adverse earth formations or topography, utility easements or other features which will reasonably be harmful to the health, safety and general welfare of the present or future inhabitants of the subdivision and/or its surrounding areas, shall not be subdivided or developed unless adequate methods are formulated by the developer and approved by the city council, upon recommendation of the planning, programming and zoning commission and city engineer, to solve the problems created by the unsuitable land conditions. Such land shall be set aside for other uses.
F. Subdivision Name: The proposed name of the subdivision shall not duplicate, or too closely approximate phonetically, the name of any other subdivision in the area covered by these regulations. The planning, programming and zoning commission shall have final authority to designate the name of the subdivision which shall be determined at the time of preliminary plat approval. (Ord. 2997, 11-20-1978)
A. Lot Arrangement: The lot arrangement shall be such that there will be no foreseeable difficulties, for reasons of topography or other conditions, in securing building permits to build on all lots in compliance with the zoning ordinance and health regulations and in providing driveway access to buildings on such lots from an approved street.
B. Lot Dimensions: Lot dimensions shall comply with the minimum standards of the zoning ordinance. Where lots are more than double the minimum required area for the zoning district, the planning, programming and zoning commission may require that such lots be arranged so as to allow further subdivision and the opening of future streets where they would be necessary to serve such potential lots, all in compliance with the zoning ordinance and these regulations. Dimensions of corner lots should be large enough to allow for erection of buildings, observing the minimum front yard setback from both streets. Depth and width of properties reserved or laid out for business, commercial or industrial purposes shall be adequate to provide for the off-street parking and loading facilities required for the type of use and development contemplated, as established in the zoning ordinance.
C. Double-Frontage Lots And Access To Lots:
1. Double-Frontage Lots: Double-frontage lots and reversed-frontage lots shall be avoided except where necessary to provide separation of residential development from traffic arterials or to overcome specific disadvantages of topography and orientation.
2. Access From Major And Secondary Arterials: Lots shall not derive access from a major or secondary arterial. Where driveway access from a major or secondary arterial may be necessary for several adjoining lots, the planning, programming and zoning commission may require that such lots be served by a combined access drive in order to limit possible traffic hazard on such street. Where possible, driveways should be designed and arranged so as to avoid requiring vehicles to back into traffic on major or secondary arterials.
D. Soil Preservation, Grading And Seeding:
1. Soil Preservation And Final Grading: In grading platted lots at least six inches (6") of topsoil shall be maintained on the lots.
2. Lot Drainage: Lots shall be laid out so as to provide positive drainage away from all buildings, and individual lot drainage shall be coordinated with the general storm drainage pattern for the area. Drainage shall be designed so as to avoid concentration of storm drainage water from each lot to adjacent lots.
E. Debris And Waste: No cut trees, timber, debris, junk, rubbish or other waste materials of any kind shall be buried in any land, or left or deposited on any lot or street at the time of issuance of a certificate of occupancy, and removal of same shall be required prior to issuance of any certificate of occupancy in a subdivision; nor shall any be left or deposited in any area of the subdivision at the time of expiration of the performance bond or dedication of public improvements, whichever is sooner.
F. Water Bodies And Watercourses: If a tract being subdivided contains a water body, or portion thereof, lot lines shall be so drawn as to distribute the entire ownership of the water body among the fees of adjacent lots. The city council may approve an alternative plan whereby the ownership of and responsibility for safe maintenance of the water body is so placed that it will not become a responsibility of the city. Where a watercourse separates the buildable portion of a lot from the street by which it has access, provisions shall be made for installation of a culvert or other structure, of design approved by the city engineer. (Ord. 2997, 11-20-1978)
A. General Requirements:
1. Frontage On Improved Streets: No subdivision shall be approved unless the area to be subdivided shall have frontage on and access from an existing street or a street shown upon a plat approved by the planning, programming and zoning commission and recorded in the county recorder of deeds' office. Such street or highway must be suitably improved as required by the highways rules, regulations, specifications or orders, or be secured by a contract required under these subdivision regulations, with the width and right-of-way required under these subdivision regulations or the official street plan. Wherever the area to be subdivided is to utilize existing street frontage, such street shall be suitably improved as provided hereinabove.
2. Grading And Improvement Plan: Streets shall be graded and improved and conform to the city construction standards and specifications and shall be approved as to design and specifications by the city engineer, in accordance with the construction plans.
3. Topography And Arrangement:
a. Streets shall be related appropriately to the topography. Local roads should be curved wherever possible to avoid conformity of lot appearance. All streets shall be arranged so as to obtain as many as possible of the building sites at, or above, the grades of the streets. Grades of streets should conform as closely as possible to the original topography. A combination of steep grades and curves shall be avoided. Specific standards are contained in the design standards in subsection B of this section.
b. All streets shall be properly integrated with the existing and proposed system of thoroughfares and dedicated rights of way as established in the comprehensive plan.
c. The design of thoroughfares should be properly related to special traffic generators such as industries, business districts, schools, churches, and shopping centers; to population densities; and to the pattern of existing and proposed land uses.
d. Minor or local streets should be laid out to conform as much as possible to the topography, to discourage use by through traffic, to permit efficient drainage and utility systems, and to require the minimum number of streets necessary to provide convenient and safe access to property.
e. The rigid rectangular gridiron street pattern need not necessarily be adhered to, and the use of curvilinear streets, cul-de-sacs, or U-shaped streets should be encouraged where such use will result in a more desirable layout.
f. Proposed streets shall be extended to the boundary lines of the tract to be subdivided, unless prevented by topography or other physical conditions, or unless in the opinion of the planning, programming and zoning commission such extension is not necessary or desirable for the coordination of the layout of the subdivision with the existing layout or the most advantageous future development or adjacent tracts.
g. In business and industrial developments, the streets and other accessways shall be planned in connection with the grouping of buildings, location of rail facilities, and the provision of alleys, truck loading and maneuvering areas and walk and parking areas so as to minimize conflict of movement between the various types of traffic, including pedestrian.
4. Blocks:
a. Blocks shall have sufficient width to provide for two (2) tiers of lots of appropriate depths. Exceptions to this prescribed block width shall be permitted in blocks adjacent to major streets, railroads or waterways.
b. The lengths, widths and shapes of blocks shall be such as are appropriate for the locality and the type of development contemplated, but block lengths in residential areas shall not exceed one thousand two hundred feet (1,200') nor be less than four hundred feet (400') in length. Wherever practicable, blocks along major arterials and collector streets shall not be less than eight hundred feet (800') in length.
c. In long blocks the planning, programming and zoning commission may require the reservation of an easement not less than ten feet (10') wide through the block to accommodate utilities, drainage facilities, or pedestrian traffic. Pedestrianways may be required by the planning, programming and zoning commission through the center of blocks more than eight hundred feet (800') long where deemed essential to provide circulation or access to schools, playgrounds, shopping centers, transportation or other community facilities. Blocks designed for industrial uses shall be of such length and width as may be determined suitable by the planning, programming and zoning commission for prospective use.
5. Access To Primary Arterials: Where a subdivision borders on or contains an existing or proposed major or secondary arterial, the planning, programming and zoning commission shall require that access to such streets be limited by one of the following means:
a. The subdivision of lots so as to back onto the primary arterial and front onto a parallel local street; no access shall be provided from the primary arterial.
b. A series of cul-de-sacs, U-shaped streets or short loops entered from and designed generally at right angles to such parallel streets, with the rear lines or their terminal lots backing onto the major arterial.
c. A marginal access or service road (separated from the primary arterial).
6. Street Names: The preliminary plat as submitted shall indicate names of proposed streets. Names shall be sufficiently different in sound and in spelling from other road names in the metropolitan area so as not to cause confusion. A road which is or is planned as a continuation of an existing road shall be the same name.
7. Street Lights: Installation of street lights shall be required in accordance with design and specification standards approved by the city engineer.
8. Reserve Strips: Installation of street lights shall not be permitted adjacent to a proposed street in such a manner as to deny access from adjacent property to such street.
9. Construction Of Roads And Dead-End Roads:
a. Construction Of Roads: The arrangement of streets shall provide for the continuation of principal streets between adjacent properties when such continuation is necessary for convenient movement of traffic, effective fire protection, for efficient provision of utilities, and where such continuation is in accordance with the comprehensive plan. If the adjacent property is undeveloped and the street must be a dead-end street temporarily, the right of way shall be extended to the property line. A temporary T- or L-shaped or circular turnabout shall be provided on all temporary dead-end streets serving more than two (2) lots, with the notation on the subdivision plat that land outside the normal street right of way shall revert to abuttors whenever the street is continued. The planning, programming and zoning commission may limit the length of temporary dead-end streets in accordance with the design standards in subsection B of this section.
b. Dead-End Roads (Permanent): Where a road does not extend beyond the boundary of the subdivision and its continuation is not required by the planning, programming and zoning commission for access to adjoining property, its terminus shall normally not be nearer to such boundary than fifty feet (50'). However, the planning, programming and zoning commission may require the reservation of an appropriate easement to accommodate drainage facilities, pedestrian traffic, or utilities. A cul-de-sac turnaround shall be provided at the end of a permanent dead-end street in accordance with city construction standards and specifications. For greater convenience to traffic and more effective police and fire protection, permanent dead-end streets shall, in general, be limited in length in accordance with the design standards regulations.
c. Adjacent Properties: When a street or street right of way is required to ensure access to an abutting property outside the subdivision, but is not required to be improved, the developer of the adjacent property shall be responsible for the improvements of said street at such time as the adjacent property is developed.
B. Design Standards:
1. General: In order to provide for roads of suitable location, width and improvement to accommodate prospective traffic and afford satisfactory access to police, firefighting, snow removal, sanitation and road maintenance equipment, and to coordinate roads so as to compose a convenient system and avoid undue hardships to adjoining properties, the following design standards for roads are hereby required (road classification may be indicated on the comprehensive plan or official map; otherwise, it shall be determined by the planning, programming and zoning commission).
2. Road Surfacing And Improvements: After sewer and water utilities have been installed by the developer, the applicant shall construct curbs and gutters or integral curbs, and shall surface or cause to be surfaced roadways to the widths prescribed in these regulations. Said surfacing shall be of such character as is suitable for the expected traffic and in harmony with similar improvements in the surrounding areas. Types of pavement shall be as determined by the city engineer and city council in accordance with the use of the street which is anticipated. Adequate provision shall be made for culverts, drains and bridges. All road pavements, shoulders, drainage improvements and structures, curbs, turnarounds and sidewalks shall conform to all construction standards and specifications adopted by the planning, programming and zoning commission, city engineer and city council and shall be incorporated into the construction plans required to be submitted by the developer.
3. Excess Right Of Way: Right-of-way widths in excess of the standards designated in these regulations shall be required whenever, due to topography, additional width is necessary to provide adequate earth slopes. Such slopes should not be in excess of three to one ratio (3:1).
4. Railroads And Limited-Access Highways: Railroad rights of way and limited-access highways where so located as to affect the subdivision of adjoining lands shall be treated as follows:
a. In residential districts a buffer strip at least twenty five feet (25') in depth in addition to the normal depth of the lot required in the district shall be provided adjacent to the railroad right of way or limited-access highway. This strip shall be part of the platted lots and shall be designated on the plat: This strip is reserved for screening. The placement of structure hereon is prohibited.
b. In districts zoned for business, commercial, or industrial uses the nearest street extending parallel or approximately parallel to the railroad shall, wherever practicable, be at a sufficient distance therefrom to ensure suitable depth for commercial or industrial sites.
c. Streets parallel to the railroad when intersecting a street which crosses the railroad at grade shall, to the extent practicable, be at a distance of at least one hundred fifty feet (150') from the railroad right of way. Such distance shall be determined with due consideration of the minimum distance required for future separation of grades by means of appropriate approach gradients.
5. Intersections:
a. Streets shall be laid out so as to intersect as nearly as possible at right angles. A proposed intersection of two (2) new streets at an angle of less than seventy five degrees (75°) shall not be acceptable. An oblique street should be curved approaching an intersection and should be approximately at right angles for at least one hundred feet (100') therefrom. Not more than two (2) streets shall intersect at any one point unless specifically approved by the city council.
b. Proposed new intersections along one side of an existing street shall, wherever practicable, coincide with any existing intersections on the opposite side of such street. Street jogs with center line offsets of less than one hundred fifty feet (150') shall not be permitted, except where the intersected street has separated dual drives without median breaks at either intersection. Where streets intersect major streets, their alignment shall be continuous. Intersection of major streets shall be at least eight hundred feet (800') apart.
c. Minimum curb radius at the intersection of two (2) local streets shall be at least twenty feet (20'); and a minimum curb radius at an intersection involving a collector street shall be at least twenty five feet (25'). Alley intersections and abrupt changes in alignment within a block shall have the corners cut off in accordance with standards of the city engineer.
d. Intersections shall be designed with a flat grade wherever practical. In hilly or rolling areas a nearly horizontal approach shall be provided at the intersection.
e. Where any street intersection will involve earth banks or existing vegetation inside any lot corner that would create a traffic hazard by limiting visibility, the developer shall cut such ground and/or vegetation (including trees) in connection with the grading of the public right of way to the extent deemed necessary to provide an adequate sight distance.
f. The cross-slopes on all streets should normally be two percent (2%).
6. Bridges And Box Culverts: Bridges or box culverts of primary benefit to the applicant, as determined by the planning, programming and zoning commission, shall be constructed at the sole expense of the applicant without reimbursement from the local government. The sharing expense for the construction of bridges and box culverts not of primary benefit to the applicant, as determined by the city engineer and the city council, will be fixed by a special agreement between the city and the applicant.
TABLE 1
DESIGN STANDARDS FOR ROADS
Development Density | Nonresidential Business Industrial
| |||
Low
| Residential Medium
| High
| ||
Development Density | Nonresidential Business Industrial
| |||
Low
| Residential Medium
| High
| ||
Minimum Width | ||||
Right-Of-Way (In Feet) | ||||
Local road | 50 | 60 | 60 | 60 |
Collector road | 60 | 60 | 70 | 60 |
Secondary arterial | 60 | 80 | 80 | 80 |
Primary arterial | 100 | 100 | 100 | 100 |
Minimum Width | ||||
Traveled Route (In Feet) | ||||
Local road | 25 W/S* | 28 W/C** | 31 W/C | 30 W/C |
Collector road | 28 W/S | 31 W/C | 40 W/C | 40 W/C |
Secondary arterial | 28 W/S | 40 W/C | 44 W/C | 44 W/C |
Primary arterial | 44 W/S | 48 W/C | 48 W/C | 48 W/C |
Maximum Grade (Percent) | ||||
Local road | 10 | 10 | 8 | 6 |
Collector road | 8 | 8 | 8 | 6 |
Secondary arterial | 6 | 6 | 6 | 5 |
Primary arterial | 6 | 6 | 6 | 5 |
Minimum Grade (Percent) | 0.5 | 0.5 | 0.5 | 0.5 |
Minimum Turn-Around (In Feet) | ||||
Local roads | ||||
R-O-W diameter | 100 | 100 | 120 | 120 |
Pavement diameter | 70 | 70 | 90 | 90 |
Center Island Diameter (if required) | 0 | 0 | 20 | 20 |
Design Speed (Miles Per Hour) | ||||
Local roads | 25 | 30 | 30 | 30 |
Collector roads | 30 | 35 | 35 | 35 |
Secondary arterial | 40 | 40 | 40 | 40 |
Primary arterial | 40 | 40 | 40 | 50 |
Length Of Cul-De-Sacs | ||||
Maximum | 12 times minimum lot width serving no more than 25 families and not exceeding 720 feet in length. | |||
*W/S = With shoulders (roll-type curb)
**W/C = With curbs (integral curbs)
C. Road Dedications And Reservations:
1. New Perimeter Street: Street systems in new subdivisions shall be laid out so as to eliminate or avoid new perimeter half streets. Where an existing half street is adjacent to a new subdivision, the other half of the street shall be improved and dedicated by the subdivider. The planning, programming and zoning commission may authorize a new perimeter street where the subdivider improves and dedicates the entire required street right-of-way width within his own subdivision boundaries.
2. Widening And Realignment Of Existing Roads: Where a subdivision borders an existing narrow road or when the comprehensive plan, official map or zoning setback regulations indicate plans for realignment or widening a road that would require use of some of the land in the subdivision, the applicant shall be required to improve and/or dedicate at his expense such areas for widening or realignment of such roads. Such frontage roads and streets shall be improved and dedicated by the applicant at his own expense to the full width as required by these subdivision regulations. Any paving requirement over thirty one feet (31') will be paid for by the city in an amount equal to the additional costs over the thirty one foot (31') width. Land reserved for any road purpose may not be counted in satisfying yard or area requirements of the zoning ordinance whether the land is to be dedicated to the city in fee simple or an easement is granted to the city. (Ord. 2997, 11-20-1978)
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