18J.15.050 Street Trees | Pierce County Code

18J.15.050 Street Trees.

The purpose of installing street trees is to enhance the environment by using plant material as a unifying element and to protect the health, safety, and welfare of the public by using street trees to mitigate the negative effects of impervious surfaces and vehicular traffic including increased temperatures, airborne particulates, carbon dioxide, noise, and stormwater runoff. Street trees also provide shade and visual interest for pedestrians.

A. Applicability. Street trees shall be installed along both sides of all urban roads in urban areas only. Flexibility may be allowed when requirements for low impact development (LID) best management practices (BMPs) preclude street trees on both sides of a road.

B. Design Objective. Provide buffers along street corridors to increase privacy and minimize noise impacts.

1. Street trees located within public or private rights-of-way shall be installed consistent with the requirements of Title 17B PCC, Road and Bridge Design and Construction Standards.

2. Street trees shall be installed along each side of streets at a rate of 1 per 30 lineal feet of roadway, excluding intersections. Clustering is permitted to allow for driveways. Spacing shall be the minimum required by the selected species pursuant to the street tree plan, but in no case shall spacing be greater than 30 feet for individual trees or 100 feet between clusters.

3. As an alternative to street tree requirements in subsection C.2 above, street tree species with large mature canopies in single-family residential subdivisions shall be installed as each lot develops at the following rate:

a. Lots less than 60 feet in width shall install a minimum of one large canopy street tree;

b. Lots 60-100 feet in width shall install a minimum of two large canopy street trees;

c. Corner lots shall be subject to street tree installation on each road frontage at the rates in subsections C.3.a and b of this Section;

d. The Director shall determine appropriate street tree installation rates for lots greater than 100 feet in width or for areas outside of individual lots, such as common areas.

4. Placement. Street trees shall be placed within the public or private road right-of-way unless there is a safety reason not to as determined by the County Engineer. In that event, the street tree requirement shall be met by placing trees on private property within 15 linear feet of the road right-of-way.

5. Minimum mature height shall be 20 feet.

6. Refer to PCC 18J.15.100, Plant Lists, for a list of appropriate street tree species.

7. When permitted, any tree installed within 5 feet of public or private road pavement edge, curbing, or sidewalk, or within required parking areas shall include a root control barrier. Root control barriers shall consist of galvanized metal or plastic sheets extending a minimum of two feet below the finished grade of the surrounding surface or as directed by the County Engineer within public road rights-of-way.

8. Within the Employment Corridor (ECOR), Neighborhood Corridor (NCOR), Towne Center (TCTR), and Urban Corridor (UCOR) zones, street trees shall be located within the right-of-way, with approval by the appropriate agency. When approval is not granted, trees shall be installed as close to the right-of-way as possible.

9. Street Tree Approval Inspection. The following are options for final approval of street trees:

a. Install all street trees prior to final plat approval;

b. Place a financial guarantee for all trees prior to final plat approval;

c. Single-Family and Two-Family. Show all the street trees on the single-family site plans. Trees shown will be required to be installed prior to building permit final inspection;

d. Non-Residential and Multi-Family. Show all the street trees on the commercial site development plans. Trees shown will be required to be installed prior to commercial site development permit final inspection.

D. Guidelines. Within the Employment Corridor (ECOR), Neighborhood Corridor (NCOR), Towne Center (TCTR), and Urban Corridor (UCOR) zones, potted trees or similar tree installation methods are allowed. The size of the container shall be determined by the landscape architect, forester, or other qualified expert, subject to approval by the Planning and Public Works Department, and shall ensure long-term viability of the street tree.