Chapter 16.16
DESIGN STANDARDS FOR NONARTERIAL STREETS
Sections:
16.16.020 Street and block layout.
16.16.030 Street design standards for nonarterial streets.
16.16.070 Arterial street standards.
16.16.080 Street design standard modification process.
16.16.010 General statements.
A. Land which the community and economic development department, hearing examiner or city council finds unsuitable or inappropriate for development due to flooding, inadequate drainage, inadequate sanitary sewer service, excessive slope, rock formations, high ground water, or other features likely to be harmful to the safety and general health and welfare of the future residents shall not be subdivided, unless adequate corrective measures can be provided and are approved by the community and economic development and public works directors.
B. Before any land disturbing work is begun, the subdivider shall submit to the community and economic development department, plans and profiles of all proposed streets, drainage plans and profiles, sewer plans and profiles, and right-of-way section drawings, including utility line placement for approval. All design drawings shall be prepared under the supervision of, and stamped by a Washington State licensed professional civil engineer. (Ord. 3428 § 44, 2008).
16.16.020 Street and block layout.
A. The street layout of all subdivisions shall provide for the following:
1. Continuity of adjoining streets and arterials.
2. Access shall be extended to the boundaries of the tract unless extenuating circumstances exist that make this impossible; and in which case the applicant shall be solely responsible for presenting indisputable evidence to support not extending the access, that shall be accepted by the community and economic development department.
3. Streets intersecting at right angles, or as nearly as possible and “T” intersection design shall be utilized insofar as practical.
4. All streets dedicated “right-of-way” shall be full width except along the boundary lines of the plat. Partial-width streets may be accepted where the community and economic development and public works directors approve the street location and boundaries of the subdivision.
5. Roads within a residential development shall not extend more than 500 feet without an intersection except if constrained by critical area limitations and/or significant topographic variation. In the absence of a functional intersection, an open space area of similar dimension to a right-of-way shall be provided.
B. Lots shall back onto arterials and front onto a parallel residential street; unless extenuating circumstances exist that make this impossible; and in which case the applicant shall be solely responsible for presenting indisputable evidence to support being allowed to front onto an arterial that shall be accepted by the community and economic development department.
C. Reserve Strips. The creation of reserve strips shall not be permitted adjacent to a proposed street in such a manner as to deny access from adjacent property to the street. Reserve strips shall also not be permitted to deny the extension of utilities to a neighboring property. (Ord. 3530 § 3, 2011).
16.16.030 Street design standards for nonarterial streets.
A. For all nonarterial streets within any zone, street standards shall be determined on the basis of the average p.m. peak hour vehicular trips to be expected on the applicable street, due to all potential traffic, as set forth in Table 1 and according to the following requirements:
1. P.m. peak hour vehicular trips shall be determined by a registered engineer licensed to provide traffic engineering study and design services.
2. Residential developments may calculate one vehicular peak hour trip for each residential unit.
3. Non-arterial street design standard selection shall be approved by the community and economic development and public works departments.
4. Developments shall be required to complete a concurrency review by the city.
5. Traffic study information as required by the city of Mount Vernon concurrency management code (Chapter 14.10 MVMC) shall require approval by the public works and community and economic development directors.
B. The following table contains minimum street design standards for nonarterial streets. The pavement width for each street type is the typical width of the street. Each street “type,” except alleys, requires a landscaped planter strip between the curb and sidewalk. The community and economic development director may require additional width as deemed necessary to facilitate additional parking, traffic calming features, bike lanes, etc.
|
P.M. Peak Hour Traffic Volume = |
< 20 |
21 to 60 |
61 to 100 |
101 to 250 |
> 250 |
|---|---|---|---|---|---|
|
Residential Zones |
3 |
3 |
3 |
3 |
4 |
|
Professional Office |
3 |
3 |
3 |
4 |
4 |
|
Public Zones |
3 |
3 |
3 |
4 |
4 |
|
Central Business District |
3 |
3 |
3 |
4 |
4 |
|
Commercial |
3 |
3 |
4 |
4 |
4 |
|
Industrial |
3 |
3 |
4 |
4 |
4 |
|
Manufacturing |
3 |
3 |
4 |
4 |
4 |
C. Following are the dimensional requirements for the road types described within Table 1:
1. Street Type 3: A 51-foot right-of-way with a 32-foot paved travel width, 0.5-foot concrete curbs, four-foot planter strips and five-foot-wide concrete sidewalks on both sides.
a. A seven-foot minimum slope and utility easement is required abutting all right-of-way lines.
b. No parking shall be allowed on turnarounds for this street type.
2. Street Type 4: A 55-foot right-of-way with a 36-foot paved travel width, 0.5-foot concrete curbs, four-foot planter strips and five-foot-wide concrete sidewalks on both sides.
a. A seven-foot minimum slope and utility easement is required abutting all right-of-way lines.
b. No parking shall be allowed on turnarounds for this street type.
D. Other Street Standards.
1. Street Type 2: a 47-foot right-of-way with a 28-foot paved travel width, 0.5-foot concrete curbs, four-foot planter strips and five-foot-wide concrete sidewalks on both sides. Type 2 streets may be used only when approved through a street design standard modification process on a case-by-case basis dependent on the applicant’s ability to demonstrate that the plat design provides the ability to accommodate all of the needs of the street; including but not limited to:
a. Provide minimum 20-foot clear zone.
b. Provide a minimum of one on-street parking opportunity per single-family residence, adjacent to and/or across the street from lots that have a minimum of 75 feet of frontage.
c. Bulb-outs or other similar design features shall be installed on the side of the road that allows parking and the parking restricted side of the road shall have “no parking” signage or other means of clearly restricting the parking such as painting of curbs completed at the discretion of the community and economic development department and fire chief.
d. A seven-foot minimum slope and utility easement is required abutting all right-of-way lines.
e. No parking shall be allowed on one side of this street type or on turnarounds.
2. Alleys: a 24-foot right-of-way with a 20-foot paved travel surface. Alleys may be required in residential areas and properties abutting arterials. Alleys may be required in all commercial areas and industrial areas. No parking is allowed within the right-of-way of alleys. “No parking” signs shall be required.
E. Residential streets serving 30 or more residential units and intersecting an arterial street shall be at least 36 feet wide at the intersection with the arterial and be tapered to the standard street width as required by the public works director. (Ord. 3530 § 4, 2011).
16.16.035 Street design standard modification process.
Repealed by Ord. 3428. (Ord. 3235 § 4, 2005).
16.16.040 Private streets.
A. The purpose of private street standards is to provide an option that reduces the cost of serving infill lots, and provide flexibility when public streets are not needed for public circulation. Following are the minimum requirements for private streets:
1. Private streets may be approved for four or fewer lots if any of the lots are less than 10,000 square feet in size. Private streets can be approved for up to nine lots when all of the lots are greater than 10,000 square feet in size.
2. A private access easement that is at a minimum of 26 feet wide with a 20-foot-wide paved surface shall be the minimum standard for private streets.
3. Private streets shall be constructed of a minimum of two inches of asphalt pavement, three inches of crushed rock, and six inches of gravel base.
4. Curbs, gutters, and sidewalks are required when more than four lots are being accessed, or when deemed necessary by the community and economic development director.
5. Streets providing fire hydrant access shall provide an all weather driving surface not less than 26 feet in width.
a. No parking shall be allowed within the 26-foot easement; however, parking may be allowed in portions of easements exceeding 26 feet in width.
6. Private streets shall be no longer than 150 feet in length, or serve more than four lots without an approved turnaround.
7. All lots accessing the private street shall be equally liable for its maintenance.
8. The grade shall not be more than 10 percent unless approved by the fire chief.
9. Internal traffic calming devices or traffic circles may be required at the discretion of the community and economic development department and fire chief.
B. Approval Criteria – General. The community and economic development director in consultation with the public works director shall determine when private streets are appropriate based on the following approval criteria:
Private streets are not allowed:
1. When they conflict with the comprehensive plan; or
2. When they are needed for public circulation; or
3. When they connect two public roads, except for commercial or industrial uses; or when they serve more than nine potential residential lots; provided, that where expansion of a public street is not presently feasible, the limitations of this subsection shall not apply if the affected internal and frontage streets are improved to public standards and dedicated to the city, with the acceptance of such dedication(s) being deferred until extension of a public street allows connection.
4. When the private street could be extended in the future to serve more than nine lots.
C. The following statement is required on the face of any plat, short plat, site plan, or binding site plan containing a private street:
The City of Mount Vernon has no responsibility to improve or maintain private streets contained within or providing access to the property described in this document. Any private street shall remain a private street unless it is upgraded to public street standards at the expense of the developer or adjoining lot owners. No private street will be accepted as a City street until such time that it meets current City standards to the satisfaction of the City Engineer and Fire Chief.
(Ord. 3530 § 5, 2011).
16.16.050 Partial streets.
A partial street shall be implemented to allow existing streets to be adjusted to current requirements and may be allowed to facilitate roadway construction along unimproved project boundaries (the adjacent off-site property must be reasonably able to support completion of the ultimate street design). The street system shall consist of sidewalk, curb, gutter, all utilities, and appurtenances, one-half of the ultimate pavement width on the development side of the right-of-way, and a two-foot gravel shoulder, on the opposite side of the street. However, the minimum pavement width shall be 20 feet. The constructed improvements may be offset from the ultimate right-of-way centerline. Other utilities and appurtenances shall be constructed to meet standards and comprehensive plans concurrent with the street construction as stated in the project requirements. Each partial street shall meet minimum access requirements and be approved by the community and economic development department. (Ord. 3428 § 48, 2008).
16.16.060 Fire/safety access.
A. Residential streets serving 30 or more residential units shall provide at least two vehicular access routes. An emergency only route may suffice for one route.
B. Access roads shall provide a driving surface capable of supporting the imposed load of fire apparatus weighing at least 75,000 pounds.
C. Access roads with fire hydrants shall be at least 26 feet wide to an approved turnaround. This condition applies to all street types including partial streets and private streets.
D. Fire apparatus access roads may not exceed 10 percent in grade. Grades steeper than 10 percent shall require approval by the fire chief.
E. Access road minimum turning radii shall be determined by the fire chief.
F. Parking restrictions along access roads shall be determined by the fire chief.
G. Access road turnaround facilities shall comply with the following table and drawings.
|
LENGTH* |
WIDTH |
TURNAROUNDS REQUIRED |
|---|---|---|
|
(feet) |
(feet) |
|
|
0 – 150 |
20 |
None required |
|
150 – 500 |
20 |
90-foot diameter cul-de-sac, or through an engineering level modification a 120-foot hammerhead or 60-foot Y might be approved. |
|
501 – 750 |
26 |
90-foot diameter cul-de-sac, or through an engineering level modification a 120-foot hammerhead or 60-foot Y might be approved. |
|
Over 750 |
|
Special approval required |
* The lengths listed within this table shall be measured from the edge of the travel lane, or as determined by the fire chief to ensure that the intent of these requirements is met.
(Ord. 3530 § 6, 2011).
16.16.070 Arterial street standards.
A. The minimum requirements for right-of-way, curb-to-curb pavement widths, curve radii, curve tangent lengths, sidewalk widths, sight distance and maximum grades of all right-of-way improvements shall be determined by the following table, unless otherwise approved by the city engineer.
|
Conditions and Capacity |
Traffic Lanes |
Parking |
Bike Lane |
Street Width |
Minimum Right-of-Way |
Minimum Curvature (Ft. Radius) |
Minimum Tangent (Btwn. Curves Length Ft.) |
Sidewalk Width |
Sight Distance (Stopping) |
Maximum Grades |
|---|---|---|---|---|---|---|---|---|---|---|
|
PRINCIPAL ARTERIAL |
||||||||||
|
5-Lane w/ Bike Lane ADT 43,530 Peak Hr. 3,480 |
2-12', 2-11', 1-12' |
N/A |
2-5' |
68' |
80' |
300' |
200' |
6' |
500' |
6% |
|
5-Lane ADT 37,040 Peak Hr. 2,960 |
2-14', 2-11', 1-12' |
N/A |
Shared Lane |
62' |
80' |
300' |
200' |
6' |
500' |
6% |
|
3-Lane w/ Bike Lane ADT 28,050 Peak Hr. 2,240 |
2-14', 1-12' |
N/A |
2-5' |
50' |
80' |
300' |
200' |
6' |
500' |
6% |
|
2-Lane w/ Parking ADT 20,730 Peak Hr. 1,660 |
2-14' |
2-8' |
Shared Lane |
44' |
60' |
300' |
200' |
6' |
500' |
6% |
|
MINOR ARTERIAL |
||||||||||
|
3-Lane w/ Bike Lane ADT 22,590 Peak Hr. 1,810 |
1-12', 2-11' |
N/A |
2-5' |
44' |
60' |
200' |
150' |
6' |
400' |
8% |
|
2-Lane w/ Parking ADT 20,730 Peak Hr. 1,660 |
2-14' |
2-8' |
Shared Lane |
44' |
60' |
200' |
150' |
6' |
400' |
8% |
|
URBAN COLLECTOR |
||||||||||
|
3-Lane w/ Bike Lane ADT 15,870 Peak Hr. 1,270 |
1-12', 2-11' |
N/A |
2-5' |
44' |
60' |
200' |
150' |
6' |
400' |
8% |
|
3-Lane ADT 14,540 Peak Hr. 1,160 |
1-12', 2-14' |
N/A |
Shared Lane |
40' |
60' |
200' |
150' |
6' |
400' |
8% |
|
2-Lane w/ Parking ADT 14,540 Peak Hr. 1,160 |
2-14' |
2-8' |
Shared Lane |
44' |
60' |
200' |
150' |
6' |
400' |
8% |
|
2-Lane w/ Parking ADT 12,900 Peak Hr. 1,030 |
2-12' |
2-8' |
None |
40' |
60' |
200' |
150' |
6' |
400' |
8% |
Note: Shared bike lane pavement width is included in 14-foot traffic lane.
(Ord. 3530 § 7, 2011).
16.16.080 Street design standard modification process.
A. There are two types of administrative street design standards modifications:
1. Planning level modifications that are approved by the community and economic development director; and
2. Engineering level modifications that are approved by the community and economic development director in consultation with the public works director.
3. Planning and engineering level modifications will be approved in limited circumstances; and only when the applicant demonstrates that a unique and unusual circumstance exists that warrants a modification from the standard code requirement.
a. Unique and unusual circumstances could include the location of critical areas and their associated buffers, unusual topographic features, the geometry of a lot, or other similar items.
b. Modifications from standard requirements will not be approved in circumstances where the applicant is seeking a modification for primarily financial reasons; i.e., the cost of certain infrastructure or the loss of a building lot are not the type of items that will be taken into consideration when determining whether or not a planning or engineering level modification will be granted.
B. Planning level modifications may address the suitability of a particular street type or feature, for a particular purpose, including but not limited to:
1. Sidewalk location or deletion, location or deletion of planter strips and landscape features;
2. Adjusted driveway locations, widths, and provisions for joint use driveways;
3. Adjusted right-of-way width of a street type, when appropriate, and required provisions are made for pedestrians, utilities and emergency services;
4. The community and economic development director may allow an applicant to use current approved standards and codes rather than those with which the project may have been vested.
C. Planning level modifications shall be proposed in conjunction with an underlying development proposal. Developer requested modification applications are to be filed with the community and economic development department, and shall:
1. Include a written request stating the reasons for the request and the factors which would make approval of the request reasonable;
2. Be accompanied by a map or drawing showing the applicable existing conditions and proposed construction features such as contours, wetlands, significant trees, lakes, streams and rivers, utilities, property lines, existing and proposed roads and driveways, existing and proposed traffic patterns, and any unusual or unique conditions not generally found in other developments;
3. Include sufficient technical analysis to enable a reasoned decision. The community and economic development department shall provide a written decision on the application. No fee is applicable to the planning level administrative modification.
D. The community and economic development director may pre-approve planning modifications and provide documentation to accompany, and be filed with, a specific application.
E. Engineering level modifications address revisions to design and construction requirements. Procedures for applying for a deviation from standard are contained in the city’s engineering standards. Developers may request pre-approval of a deviation from engineering standards to assess project viability. Deviations from engineering standards are approved by the community and economic development director, with concurrence of the public works director. Documentation of pre-approval shall accompany and be filed with a specific application. Deviations affecting emergency service access, including turnarounds, shall be approved by the fire chief.
F. Engineering level modifications may involve, but are not limited to, the following:
1. Surfacing for roads or pedestrian facilities within road rights-of-way;
2. Asphalt and/or base rock thickness;
3. Channelization;
4. Maximum street grade (grades in excess of 10 percent require concurrence of the fire chief);
5. Design speed;
6. Sight distances;
7. Type and/or location of signage. Signage for fire and emergency services shall require concurrence of the fire chief;
8. Vertical and horizontal geometry;
9. Intersection interior angles and curb radii;
10. Access related modifications onto arterial and state routes;
11. The community and economic development director, with concurrence of the public works director, may approve alternate designs that will provide an improvement equal, or superior to, a standard design.
G. Engineering level modification requests may be requested at any time by filing a written application with the community and economic development department. The application shall include sufficient technical analysis to enable a reasoned decision. The community and economic development director, or his/her designee, shall provide a written decision on the application. No fee is applicable to the administrative modification. (Ord. 3530 § 8, 2011).