(A) General requirements.
(1) Access. No subdivision shall be approved unless the area to be subdivided has access to one of the following:
(a) An existing federal, state, county, city, road district highway, or township highway; or
(b) Rights-of-way shown upon a plat as a platted private drive or dedicated public rights-of-way approved by the county and recorded in the County Register of Deeds office. Such rights-of-way, private drives, or highways must be improved as required under these subdivision regulations.
(2) Access easements. The county shall not approve a plat with an existing or proposed easement to provide access to a proposed subdivision unless the following requirements are met.
(a) The width of the access easement is a minimum of 40 feet in width and shall serve a maximum of two lots.
(b) Roadways within easements that serve greater than two lots shall be improved to the standards defined for a local/collector road and said easements shall comply with the minimum right-of-way widths for local/collector roads as specified in the tables in division (D) below.
(c) Proposed easements shall be shown on the final plat and/or copies of the existing easements documents or previously platted easements shall be provided and recording information shall be referenced on the final plat.
(d) If existing, platted, or miscellaneous easements specifically restrict or limit the use and terms of any easement intended for use to the proposed subdivision, the written consent of the underlying property owner(s) shall be provided.
(e) The number of lots served by a dead-end road shall comply with division (B) below.
(3) Road improvements. Roads shall be improved per construction plans as approved by the Highway Superintendent or their designee. Acceptance of the final plat and approval of street design does not guarantee that the completed street will be maintained by the County Highway Department or recognized as a part of the County Highway System.
(4) Topography and arrangement.
(a) A combination of steep grades and curves should be avoided. Specific standards are contained in the design standards of these regulations. (See the tables in division (D) below.)
(b) All streets should be properly integrated with the existing and proposed systems of roads and dedicated rights-of-way as required by county ordinance.
(c) All roads shall be properly classified for the pattern of existing and proposed land uses.
(d) The use of curvilinear streets, cul-de-sacs, or U-shaped streets are encouraged where such use will result in a more desirable layout.
(e) Roads shall be extended to the boundary lines of the tract to be subdivided, unless prevented by topography, other physical conditions, or unless such extension is not necessary or desirable to/for future development of adjoining/adjacent properties.
(f) Maximum length and number of lots served by a dead-end road shall comply with division (B) below.
(5) Access to major arterials. Where a subdivision borders on or contains an existing or proposed major arterial, access to such streets shall be limited by one of the following means:
(a) The configuration of lots, so as to establish rear lot lines adjoining major arterials and front lot lines adjoining parallel local streets. No access shall be provided from the major arterial, and screening may be required in a strip of land along the rear property line of such lots;
(b) A series of cul-de-sacs, U-shaped streets, or short loops entered from and designed generally at right angles to such a parallel street, with the rear lines of their terminal lots backing onto the major arterial; and
(c) A marginal access or service road (separated from the major arterial by a planting or grass strip and having access thereto at suitable points).
(6) Road 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 county jurisdiction so as not to cause confusion. A road which is, or is planned as, a continuation of an existing road shall bear the same name. The Planning and Zoning Office shall review proposed street names with the appropriate agencies and/or departments and provide a recommendation to the County Commission.
(7) Road regulatory signs. The applicant shall install, in accordance with the standards of the County Highway Department, all road and street name signs, the type and location of which shall be approved by the County Commission, prior to the release of surety.
(8) Street lights. The applicant may be required to furnish and install street lights.
(B) Construction of roads, dead-end roads, and cul-de-sacs.
(1) Construction of roads. The arrangement of roads shall provide for the continuation of principal roads between adjoining properties when such continuation is necessary for convenient movement of traffic, effective fire protection, and for efficient extension of utilities.
(2) Temporary dead-end roads.
(a) Any road with only one means of vehicular ingress/egress. A dead-end road may be permitted provided that it does not provide access to no more than two lots and does not exceed 500 feet in length (as measured along the centerline from intersection of the adjoining roadway to the center of the terminus) unless a longer length is deemed appropriate.
(b) If a dead-end road abuts adjoining undeveloped property, such dead-end road may only be allowed temporarily and the developer may be required to dedicate the right-of-way on the plat and show it as extending to the adjoining property line. All temporary dead-end roads shall be designed per the standards set out in the tables in division (D) below, and Figure 1 in division (D) below.
(3) Cul-de-sac. A local street with only one outlet and having an appropriate terminal for the safe and convenient reversal of traffic movement. Unless indicated otherwise for reasons of grade, vegetation and/or topography, the following apply.
(a) The maximum length for a cul-de-sac serving lot(s) with an acreage of two acres or less shall be no more than 500 feet.
(b) The maximum length for a cul-de-sac serving lot(s) with an acreage of more than three acres and less than ten acres shall be no more than 800 feet.
(c) The maximum length for a cul-de-sac serving lot(s) with the an acreage of more than 11 acres and less than 40 acres shall be no more than 1,000 feet.
(C) Design standards. 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 in a convenient system and avoid undue hardships to adjoining properties, the following design standards for roads are hereby required.
(1) Road surfacing and improvements. When sewer and water utilities have been installed by the developer, the applicant shall construct curbs and gutters, where required, and shall surface roadways to the widths prescribed in these regulations. Types and thickness of surfacing shall be at a minimum of four inches for asphalt and six inches for concrete or in each case greater as determined to be necessary by a state registered professional engineer. Adequate provision shall be made for culverts, drains, and bridges. All road surfacing, shoulders, drainage improvements and structures, curbs, turnarounds, and sidewalks shall conform to all design and construction standards and specifications of these ordinances.
(2) Additional rights-of-way. Additional rights-of-way or construction and maintenance easements shall be provided to maintain adequate slopes.
(3) Railroads and limited access highways. In residential districts a buffer strip at least 25 feet in depth, in addition to required setbacks, shall be provided adjoining 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 structures hereon is prohibited.”
(4) Intersections.
(a) Streets shall be laid out to intersect as nearly as possible at right angles. Intersections shall not be less than a 75-degree angle. A 100-foot tangent shall be provided from the intersection to the first horizontal curve. Not more than two streets shall intersect at any one point.
(b) 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 centerline offsets of less than 150 feet shall not be permitted unless specifically approved by the County Commission. Intersections with arterial roads shall have a minimum 800-foot separation. Intersections separation of all other road classifications shall be at least equal to AASHTO stopping sight distance.
(c) Minimum driving surface radius at any intersection will be 25 feet. Adequate right-of-way or easement shall be provided at intersections to accommodate the 25-foot radius.
(d) Wherever practical, intersections shall be designed with minimum grades of 1% and a maximum grade of 3%. A leveling or landing area shall be provided at the approach to the intersection. The grade at the landing area shall not be greater than 5% for a distance of 50 feet, as measured from the nearest right-of-way line of the intersection.
(e) Adequate sight distances shall be provided and maintained at all intersections.
(f) The cross-slopes on all streets, including intersections, shall be 2% or more.
(5) Bridges. Bridges of primary benefit to the applicant, as determined by the Planning and Zoning Board, shall be constructed at the full expense of the applicant. The sharing of expense for the construction of bridges not of primary benefit to the applicant, as determined by the County Commission, will be fixed by special agreement. Bridges shall be constructed to the same width as the roadway, at a standard appropriate to traffic and loading requirements. Plans for such bridges shall be designed and sealed by a registered professional engineer. All bridges shall be posted with the weight limit if less than state standards.
(6) Culverts. Culverts under roadways and driveways shall be C.M.P. flared end sections or slopes and concrete headwalls are required on all culverts within the right-of-way. The size of culverts shall be determined by a drainage study for the entire subdivision. The minimum culvert diameter shall be 15 inches.
(7) Driveway. Driveway spacing and sight distance requirements shall be in accordance with SDDOT standards.
(D) Road dedications and reservations.
(1) Section line right-of-way. Where an existing section line right-of-way or portion of a section line right-of-way is located within a new subdivision or adjoining any portion of a new subdivision, the entire 66 feet of section line right-of-way shall be dedicated and improved by the developer, except in such instances where an adjoining landowner may decline to participate in the right-of-way dedication, or if it is not practical or not desirable to construct the street within the existing section line right-of-way, the County Commission may authorize a new right-of-way where the developer will improve and dedicate the entire required street right-of-way within the boundaries of the developing property.
(2) Widening and realignment of existing roads.
(a) Where a subdivision borders an existing narrow road or when the Comprehensive Plan, Major Street Plan, or Capital Improvements Program, if any, 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 dedicate, at his or her expense, such areas for widening or realignment of such roads.
(b) Such frontage roads and streets shall be improved and dedicated by the applicant at his or her own expense to the full width as required by the subdivision regulations.
(c) Land reserved for any road purposes may not be counted in satisfying yard or area requirements of Title II of this code whether the land is to be dedicated in fee simple or an easement is granted to the public.
(3) Design standards. The standards required in the tables below may not fully comply with the minimum standards established by the County Highway Department for roads to be considered for acceptance on the County Highway System for maintenance and snow removal.
Design Standards for Roads and Development Density | |||||
Min. Lot Size: District: | 40 ac A-1 | 8 ac A-2 | 2 ac PF RR SRD No Improvements | 7,500 sf SRD with Improvements | Nonresidential GC RC HSC C/LI I-1 |
Design Standards for Roads and Development Density | |||||
Min. Lot Size: District: | 40 ac A-1 | 8 ac A-2 | 2 ac PF RR SRD No Improvements | 7,500 sf SRD with Improvements | Nonresidential GC RC HSC C/LI I-1 |
Minimum Width Right-of-Way (In Feet) | |||||
Local/collector road | * | 66 | 66 | 66 | 66 |
Minor arterial | - | 66 | 80 | 80 | 80 |
Major arterial | - | 100 | 100 | 100 | 100 |
Minimum Width Travel Route (In Feet) and Surface | |||||
Local/collector road | * | 241 | 241 | 243,4,6,7 | 323 |
Local/collector road with parking | - | 241 | 241 | 323,4,5,7 | 323 |
Minor arterial | - | 322 | 322 | 323,4,6,7 | 423 |
Major arterial | - | 483 | 483 | 483,4,6,7 | 483 |
Maximum Grade (Percent) | |||||
Local | - | 10** | 10** | 9 | 8 |
Collector | - | 10 | 10 | 8 | 6 |
Minor arterial | - | 7 | 7 | 6 | 5 |
Major arterial | - | 7 | 7 | 6 | 5 |
Minimum grade | - | 1 | 1 | 0.5 | 0.5 |
Table notes: *: A 40-foot easement for access is allowed for a maximum of two lots. Minimum driving surface width is not specified. **: In areas of steep topography for grades greater than 10% and less than 14% in straight lengths of 200 feet or less and subject to straight lengths before curves or intersections that have grades less than 7% or as deemed reasonable may be allowed. 1: 4” gravel surface, compacted 2: 6” gravel surface, compacted 3: Paved surface: asphalt - minimum of 4”; concrete - minimum of 6” 4: With curbs state DOT Type B-66 and/or Type D 5: On-street, parallel parking permitted 6: On-street, parallel parking prohibited 7: Sidewalks (5’-wide lot line) | |||||
Design Standards for Roads and Development Density
| ||||
A-1/A-2 | PF RR SRD Unless Improvements | SRD with Improvements | Non-Residential GC RC HSC C/LI I-1 | |
Design Standards for Roads and Development Density
| ||||
A-1/A-2 | PF RR SRD Unless Improvements | SRD with Improvements | Non-Residential GC RC HSC C/LI I-1 | |
Minimum Centerline Radius of Curve (In Feet) | ||||
Local | 100 | 100 | 100 | 200 |
Collector | 100 | 100 | 100 | 200 |
Minor arterial | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards |
Major arterial | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards |
Minimum Length of Vertical Curve | ||||
Local collector | 100 feet, but not less than 20 feet for each 1% change in algebraic difference in grade | |||
Minor arterial | Per AASHTO Standards | |||
Major arterial | Per AASHTO Standards | |||
Minimum Length of Tangents Between Reverse Curves (In Feet) | ||||
Local | 100 | 100 | 150 | 200 |
Collector | 100 | 100 | 150 | 200 |
Minor arterial | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards |
Major arterial | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards | Per AASHTO standards |
Side Slope and Ditch Depth | ||||
Inslopes shall be 4:1 or flatter | ||||
Backslopes shall be 3:1 or flatter* | ||||
Road ditches shall have a minimum depth of two feet | ||||
Minimum Stopping Sight Distance (In Feet): Per AASHTO standards | ||||
Design Speed (Miles Per Hour) | ||||
Local road | 25 | 25 | 25 | 25 |
Collector | 30 | 35 | 35 | 35 |
Minor arterial | 40 | 40 | 40 | 40 |
Major arterial | 40 | 40 | 40 | 50 |
Minimum Diameter Turnaround (In Feet) for Cul-De-Sac and Intermediate Turnaround | ||||
ROW diameter | 140 | 140 | 140 | 160 |
Surfacing | 110 | 110 | 110 | 140 |
Table notes: *Special consideration may be given in areas of steep topography or in areas of stable material that can not support vegetation. Under no condition shall backslopes be steeper than 1:1. | ||||
(Ord. 14-04, passed 6-30-2015, Ch. 7, Art. 6; Ord. 19-01, passed 4-9- 2019)