17B.20.040 Minimum Existing Offsite Private Road Requirements.
A. When required by Tables 17B.20.005-1 and 17B.20.005-2, proposed developments must improve offsite existing private roads to meet the requirements contained in this Section. Reference PCC 17B.10.050 for the definition of "offsite existing private road."
B. Existing offsite private roads and easements must meet the following minimum standards:
1. Minimum Geometric Criteria. (see Table 17B.20.040-3).
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Table 17B.20.040-3. Minimum Existing Offsite Private Road Geometric Criteria by Average Daily Traffic |
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|---|---|---|---|
|
ADT (3) |
Traveled Surface Width |
Minimum Surfacing (5)(6) |
Shoulder |
|
<60 (Rural Area) |
20 ft |
Gravel (1) |
not required |
|
<60 (Urban Area) |
20 ft |
Paved (2)(4) |
not required |
|
60 - 500 |
20 ft |
Paved (2)(4) |
not required |
|
>500 |
24 ft |
Paved (2)(4) |
not required |
|
Notes: (1) "Gravel surface" is defined as two inches minimum of crushed surfacing top course over suitable gravel base or matching the existing gravel thickness, whichever is greater. Gravel surfacing shall be in accordance with Washington State Department of Transportation specifications. Must be able to support the imposed loads of fire apparatus and must provide all-weather driving capabilities. (2) "Paved surface" is defined as two inches of hot mix asphalt Class 1/2 inch over suitable gravel base or six inches of Portland cement concrete over suitable gravel base or matching the existing pavement section, whichever is greater. Pavement and subgrade materials shall be in accordance with Washington State Department of Transportation specifications. (3) "Average daily traffic or ADT" for the purposes of this Table is equivalent to 10 vehicle trips per day for each dwelling unit or each existing or proposed lot that accesses onto the private road or access easement. Traffic generation for other uses (commercial, non-residential, etc.) will be in accordance with the latest publication of "Trip Generation," by the Institute of Traffic Engineers or other County-approved sources. The ADT figure shall include the existing ADT, the ADT from the proposed development, as well as the ADT from other proposed projects. Other proposed projects will only be included in the ADT figure if they submitted a complete application prior to the proposed development being reviewed. ADT can vary along certain segments for any given roadway. For purposes of the above table, the highest ADT for any given segment on a private road shall be utilized as the basis for determining the necessary improvements for the entire roadway. There shall be no variation in improvement requirements along the entire roadway due to changes in ADT along the roadway. (4) A subdivision that proposes two lots and limits each lot to one primary dwelling unit and one accessory dwelling unit is not required to pave the existing off-site private road except when the grade exceeds 12 percent. (5) For roadways that require complete new surfaces, the minimum surfacing shall be permeable pavement, if feasible. If all new surfacing is not required, the surfacing identified above is acceptable. (6) Permeable pavement shall be designed in accordance with the Pierce County Stormwater Management and Site Development Manual and the Pierce County Road Standards. |
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2. Vertical Clearance. The private road or easement must have an unobstructed vertical clearance of not less than 13 feet 6 inches. The County, after conferring with the local fire chief, may allow a reduction in the vertical clearance, provided such reduction does not impair access by emergency vehicles, and approved signs are installed and maintained indicating the established vertical clearance.
3. Bridges and Structures. All bridges and structures, including drainage structures, must be capable of carrying a minimum design load of HS-25 per "Standard Specifications for Highway Bridges," as published by the American Association of State Highway and Transportation Officials. The County may require that the capacity of bridges and structures be certified by a licensed structural engineer.
4. Easements or Tracts. Private road easements or tracts must be of sufficient width so as to completely contain the minimum required traveled way, minimum shoulder and any associated drainage features. The County may require survey information to verify that the traveled way, shoulder area and associated drainage features are located within the documented easement or tract.
5. Obstructions. Obstructions, including, but not limited to, street lighting, poles, power poles, utility boxes, telephone boxes, street trees, small wireless facilities, equipment cabinets, retaining walls, fire hydrants and/or landscaping material, shall not be located so as to interfere with the required minimum traveled way, pedestrian area, or minimum shoulder area. Sight obscuring objects must be removed or relocated to provide sight distance as required in Table 17B.20.040-4.
6. Traffic Signs.
a. Road Signs and Road Names. All private roads must have private road name signs that meet the requirements outlined in this Title and the "Manual on Design Guidelines and Specifications for Road and Bridge Construction in Pierce County." All private roads shall be named and/or numbered in accordance with Chapter 10.44 PCC.
b. Stop Signs. All private road approaches to County arterial roads shall have a stop sign installed and maintained by the property owners, in accordance with the requirements of this Title and the "Manual on Design Guidelines and Specifications for Road and Bridge Construction in Pierce County."
c. Speed Limit Signs. Speed limit signs are required and must be maintained by the property owners. Speed limit signs must meet and must be installed according to the engineer’s recommendation. The posted speed limit must be consistent with the available entering sight distance and stopping sight distance.
7. Grades. Road grades in excess of 12 percent must have a paved surface meeting the requirements of Table 17B.20.040-3.
8. Medians. A road separated by a median shall have a minimum traveled surface width of 15 feet on each side of the median. Fire hydrants must be located on both sides of the median or accessible from both sides.
9. Turnarounds. Cul-de-sacs or intersections are required at a minimum of 1,500 feet measured along the road centerline from intersection/cul-de-sac to intersection/cul-de-sac.
C. Entering sight distance, stopping sight distance, and maximum grade shall meet the minimum requirement of the Manual on Design Guidelines and Specifications for Road and Bridge Construction in Pierce County.