A. Major: Wherever a subdivision includes a major street, such street shall be platted in the location indicated on the major street plan.
B. Secondary Or Collector: Secondary or collector streets shall be included when it is apparent that sufficient traffic will flow from minor streets within the subdivision.
C. Layout: The street layout shall conform to the official plans, as well as providing proper circulation for fire department, protection for pedestrian travel, and access to schools, parks, playgrounds, and shopping areas.
D. Marginal Access: Where a subdivision has frontage on a major street and where it is not feasible to have the lots back to such street, provision may be required for marginal access streets. These marginal access streets shall be approximately parallel to the major street right of way and separated therefrom by a strip of land at least twenty feet (20') wide. The plan commission may require that separation strips be planted, but such planting shall be so placed that it does not create a traffic hazard.
E. Alleys: In general, alleys will be approved for new residential districts in a subdivision only if a homeowners' association owns and maintains them in perpetuity, and a recorded special service area (SSA) agreement is in place to support them. An alley will have a minimum pavement width of twenty feet (20') and all horizontal and vertical geometry shall meet all applicable police and fire department public safety requirements.
F. Culs-De-Sac: Culs-de-sac shall not exceed five hundred feet (500') in length and shall terminate in:
1. A bulb not less than one hundred twenty feet (120') in diameter of right of way and pavement diameter of ninety feet (90') at the closed end.
2. A T-shaped turnaround with forty foot (40') extension to either side of the main stem shall be used where a temporary turnaround is recommended by the fire department.
G. Roundabouts: Shall be designed in accordance with the most current edition of the U.S. department of transportation federal highway administration publication entitled "Roundabouts: An Informational Guide".
H. Existing Streets: Where a development abuts an existing street, the city engineer may direct the developer to:
1. Widen and add curb and gutter to the existing street.
2. Pave the existing street with a two inch (2") thick bituminous concrete surface course overlay using a Superpave bituminous mixture with the appropriate performance grade asphalt cement binder.
3. Reconstruct the road if unsatisfactory base, subbase, or subgrade conditions exist.
I. Street Grades: Street grades shall conform in general to the terrain and shall not be less than one-half percent (0.5%) nor more than seven percent (7%). Street grades shall be such as to provide natural surface drainage of storm water regardless of the presence or absence of storm sewers. Unusual circumstances will be considered for variation of these grade requirements.
J. Right Of Way And Street Widths: (All streets to be measured back to back of curb.)
Dedicated Type Of Street
|
Improved Street Width
|
Street Width
|
Primary streets | 100 feet divided by a medial strip | Two 24-foot roadways |
Secondary streets | 80 feet | 40 feet |
Minor streets | 66 feet | 28 feet |
Cul-de-sac bulb | 62 foot radius | 45.5 foot radius |
K. Soil Survey: Prior to beginning the street or parking lot design, the developer's engineer shall meet with the city engineer to determine if a soil survey and/or soil borings will be required and, if required, the extent thereof.
L. Street Pavement Design: All streets within the subdivision shall be improved with a durable hard surface bituminous or Portland cement concrete pavement. The pavement shall meet or exceed the requirements, materials, equipment, and methods documented in the latest editions of the Illinois department of transportation (IDOT) "Standard Specifications For Road And Bridge Construction", and the IDOT "Supplemental Specifications And Recurring Special Provisions".
Subgrade earth excavation in accordance with approved engineering plans to provide a stable subgrade having an IBR value of no less than 3.0. IBR tests will be required if, in the opinion of the city engineer, they are necessary to evaluate the subgrade material. A proof roll in the presence of a city inspector is required of all street and parking lot subgrades.
1. Type Of Pavement: The following are all minimum pavement sections. All materials classifications are IDOT nomenclature. All flexible pavements will conform to the IDOT "Bureau Of Design And Environment Special Provision For Superpave Bituminous Concrete Mixtures", revised date April 1, 2004, or the latest revision thereto, unless modified below. All dimensions are minimum compacted thickness. Friction aggregate for the bituminous surface course may be required as directed by the city engineer.
a. Public and private streets in commercial and industrial areas: Following the approved subgrade proof roll, geotextile fabric, twelve (12) ounces per square yard, and otherwise meeting the requirements for ground stabilization found in section 210 of the IDOT standard specifications, shall be placed over the compacted subgrade prior to placement of the subbase or base course unless the subgrade has been lime stabilized.
6 inches crushed coarse aggregate subbase, type B, gradation CA-6
Bituminous materials prime coat, 0.5 gallons per square yard
9 inches bituminous base course, CA-10 aggregate, PG64-22 asphalt cement
21/4 inches bituminous concrete binder course, Superpave mixture, SBR or SBS PG76-28 asphalt cement
11/2 inches bituminous concrete surface course, Superpave mixture, SBR or SBS PG76-28 asphalt cement
b. All other public and private streets: Following the approved subgrade proof roll, geotextile fabric, twelve (12) ounces per square yard, and otherwise meeting the requirements for ground stabilization found in section 210 of the IDOT standard specifications, shall be placed over the compacted subgrade prior to placement of the subbase or base course unless the subgrade has been lime stabilized.
6 inches crushed coarse aggregate subbase, type B, gradation CA-6
Bituminous materials prime coat, 0.5 gallons per square yard
5 inches bituminous base course, CA-10 aggregate, PG64-22 asphalt cement
21/4 inches bituminous concrete binder course, Superpave mixture, SBR or SBS PG64-28 asphalt cement
11/2 inches bituminous concrete surface course, Superpave mixture, SBR or SBS PG64-28 asphalt cement
c. Off street private parking lots:
121/2 inches crushed coarse aggregate subbase, type B, gradation CA-6
Bituminous materials prime coat, 0.5 gallons per square yard
21/4 inches bituminous concrete binder course, Superpave mixture, SBR or SBS PG64-28 asphalt cement
11/2 inches bituminous concrete surface course, Superpave mixture, SBR or SBS PG64-28 asphalt cement
The city engineer may require Portland cement concrete or composite pavements if site conditions and/or usage warrant. These pavements shall be designed in accordance with the requirements provided in the IDOT "Bureau Of Design And Environment Manual".
Before any paving work commences, the city engineer, or engineers retained by the city, shall approve all plans, profiles and specifications.
All underground work such as sewers, water and gas mains, house service connections, etc., for service to both sides of the street, shall be installed and approved by the city engineer prior to the construction of the street pavement.
Controlled backfilling will be required for all trenches excavated for conduits located under existing or proposed roadway and parking lot pavement areas. Said controlled backfilling shall consist of crushed coarse aggregate, IDOT gradation CA-6 or CA-7, or as directed by the city engineer or his/her authorized representative.
2. Unsuitable Subgrade Material: When unsuitable material is encountered in the subgrade, it shall be:
a. Removed and replaced with an approved granular material, or
b. Stabilized by lime application in accordance with section 310 of the IDOT standard specifications, or
c. Spanned with an approved engineering fabric.
The city engineer shall approve the method of subgrade stabilization used.
3. Subdrainage System: In areas where there are poorly drained soils and/or a high water table, an approved subdrainage system shall be installed consisting of a six inch (6") diameter perforated pipe system and granular filter material enclosed in a geotextile fabric envelope. The subdrainage system shall discharge into the storm sewer system.
4. Placement Of Base Course: No base course material shall be placed before the subgrade has been inspected, proof rolled, and approved for grade and compaction by the city engineer or his/her authorized representative.
After approval of the subbase and subgrade, no vehicular or construction traffic, except for road construction equipment necessary to place the base course, shall be permitted on the streets before the base course and bituminous binder course have been completed.
5. Placement Of Surface Course: All roadways with binder course in place shall experience one winter season prior to placement of the surface course. However, in no instance shall the surface course be placed until ninety percent (90%) of the homes have been completed, or as directed by the city engineer. All defects in the roadway shall be repaired as directed by the city engineer prior to the placement of the surface course.
M. Horizontal Street Curvature: The minimum radii of curvature of streets on the centerline shall be:
Major streets | 600 feet |
Secondary streets | 300 feet |
All other streets | 150 feet |
N. Street Intersections:
1. 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 eighty degrees (80o) shall not be acceptable unless adequate circular radii or angular cutouts are provided. Not more than two (2) streets shall intersect at any one point unless specifically approved by the plan commission.
2. Proposed new intersections along one side of any 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 one hundred twenty five feet (125') shall not be permitted. Where streets intersect major streets, their alignment shall be continuous.
3. The corner lots at a major or secondary intersection shall be truncated by straight lines joining points twenty five feet (25') back from the property line intersection in each quadrant. Road or street dedications at intersections shall take this form, and in cases involving major highways, angular intersections, or in any case where more dedications are deemed necessary to provide safe sight distance or for traffic channelization, the plan commission may specify a greater cutoff than the normal cited above. Other intersections and abrupt changes in alignment within a block shall have the corners cut off in accordance with standard engineering practice, to permit safe vehicular movement.
4. 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 adequate sight distance.
O. Curb Radii: Curb radii shall not be less than twenty five feet (25').
P. Curb And Gutter: A Portland cement concrete combination curb and gutter, type B6.12, or concrete gutter shall be constructed along street and parking lot pavement edges. The combination curb and gutter or gutter shall conform to current requirements of the city and shall be approved by the city engineer.
A roll type curb and gutter section may be used in developments only by written permission of the city engineer.
Q. Vertical Curves: Vertical curves shall be used at all changes in street grade. Minimum length of crest vertical curves shall be eighty feet (80') and minimum length of sag vertical curves shall be fifty feet (50').
R. Half Streets: Street systems in new subdivisions shall be laid out so as to eliminate or avoid half streets. Where a half street is adjacent to a new subdivision, the subdivider shall dedicate the other half of the street. Where a new subdivision abuts an existing street of inadequate right of way width, additional right of way width may be required to be dedicated by the subdivider to meet the requirements of this section.
S. Temporary Street Signs:
1. The developer of any subdivision shall provide temporary street signs on at least one corner of each intersection in said subdivision, said temporary street signs to be installed no later than two (2) working days after completion of curb and gutter construction at said intersection, and shall be maintained in a condition conforming with the standards hereinafter described until permanent signs have been erected.
2. Said temporary street signs shall be mounted on a four inch by four inch (4" x 4") post and set a minimum of thirty inches (30") into the ground.
3. Said street signs shall be stenciled and/or painted vertically on the four by four (4 x 4) post, and in a contrasting color to the background in order to be readable from a reasonable distance.
4. That the bottom of any such sign shall be a minimum of six feet six inches (6'6") above the top of the curb.
5. Said signs and post shall remain the property of the developer, and may be removed once permanent signs have been placed.
6. The developer shall provide type III barricades at dead end streets in accordance with IDOT standard 702001-05 or the latest revision thereto as directed by the city engineer or his/her authorized representative. At least one "Road Closed" sign, R11-2, shall be provided meeting the requirements of the most current edition of the "Manual On Uniform Traffic Control Devices". (Ord. 04-72, 12-20-2004)