18J.15.030 Tree Conservation | Pierce County Code

18J.15.030 Tree Conservation.

The purpose of this Section is to retain and/or restore the overall tree canopy in the County by using plant materials as a unifying element and tool to protect the health, safety, and welfare of the public. Trees mitigate the negative effects of loss to native wildlife biodiversity, impervious surfaces, and vehicular traffic, such as increased temperatures, airborne particulates, carbon dioxide, noise, and stormwater runoff.

A. Applicability. The standards of this Section apply to:

1. New uses and divisions of land proposed on vacant or redeveloping parcels;

2. Expansions of existing civic, utility, commercial, industrial, and multi-family uses exceeding 10 percent of the existing building footprint or associated impervious areas (parking lots, storage areas, etc.) that do not have an existing approved tree conservation plan; and

3. Class IV Forest Practices.

B. Exemptions. The following uses shall not be subject to the standards of this Section. The exemptions herein shall not preclude compliance with the Pierce County Stormwater Management and Site Development Manual or other applicable regulations outside of this Section:

1. Development occurring within any designated airport safety area or object-free area.

2. Land utilized for agricultural activities, except for Agricultural Product Sales, Agricultural Supply Sales, and Agricultural Services Use Types, that meets one of the following requirements:

a. The land is located within the Agricultural Resource Lands (ARL) or Rural Farm (RF) zones;

b. The land is subject to an approved Hobby Farm Agreement;

c. The land meets the definition of Farm and Agricultural Land pursuant to RCW 84.34 and is being taxed as such; or

d. The land is existing pasture land and is utilized for agricultural purposes, such as livestock production.

3. Silvicultural activities occurring within the Forest Land (FL) zone and/or active forest land that is being treated as a harvestable crop.

4. Surface mining conducted within a designated Mineral Resource Overlay.

5. Urban short subdivisions of 4 lots or less on project sites of 1 acre or less, except that the significant tree retention provisions specified in PCC 18J.15.030.F.3 shall apply, unless otherwise exempted herein. The significant trees shall be shown on the site plan and can be reviewed in conjunction with the short plat.

6. Expansion, remodeling, or maintenance of structures, provided that the existing building footprint is not increased by more than 30 percent.

7. Construction, reconstruction, or maintenance of public roads, paths, bicycle ways, trails, bridges, sewer lines, storm drainage facilities, related critical area mitigation activities, and other similar public infrastructure, excluding public buildings.

8. Significant tree retention shall be waived within the first 100 feet of lot depth for mixed-use buildings located within a Residential Targeted Area designated by the Pierce County Council pursuant to Chapter 84.14 RCW when the streetscape standards of PCC 18J.30.110.B * are met.

* Code Revisor's Note: PCC 18J.30.110 was repealed in its entirety by Ordinance No. 2020-102s. Please refer to PCC 18J.30.100.A.

9. Cell tower lease area of up to 1,000 square feet.

C. Tree Conservation Plan. A tree conservation plan, meeting standards as specified in PCC 18J.10.055, is required for any project that is subject to the standards of this Chapter, unless PPW staff determine that one or more of the following applies:

1. Trees, as required by Table 18J.15.030-2, exist in a current protected area, such as a steep slope or wetland/buffer.

2. Existing trees are not significant and are not proposed to be retained to satisfy tree unit requirements.

3. The project does not require a landscape plan, and no more than 20 tree units are required for the project. In such case, photos may be submitted in lieu of a tree conservation plan and the applicant must clearly identify the species, diameter, and location of trees on the project site plan.

D. Credits. All trees on-site that meet the standards of this Section and are required, provided, or are retained for residential street trees, perimeter buffering or otherwise, may be counted toward the minimum tree unit requirements.

E. Design Objective. To promote tree conservation by establishing minimum tree density requirements, expressed as tree units per acre, for new or expanding uses proposed on vacant and redeveloping parcels. It is intended that the tree density requirements will be met primarily through the conservation of existing trees. However, in order to provide for continued flexibility in the design of new development, in those situations where an applicant's design would preclude the retention of the required number of trees, the use of replacement or supplemental tree planting is authorized. It is also recognized that some sites may not contain enough existing trees to meet the tree density standards. In those situations, additional trees are to be planted as necessary to achieve the minimum tree density requirements.

1. Construction Buffer. No construction shall occur within the anticipated mature critical root zone of a tree planted or retained to meet tree unit density requirements. (See PCC 18J.15.130, Plant Protection and Maintenance, for additional standards and PCC 18J.15.100, Plant Lists, for tree species and canopy sizes.)

2. Residential Lot Location. To minimize development-related conflicts and foster long-term success of tree conservation in residential spaces, the following standards shall apply to tree conservation on residential lots:

a. Lots must be at least 8,000 square feet in size to include trees that count toward tree unit density requirements.

b. Replacement coniferous and broadleaf evergreen trees shall not be less than 4 feet in height at time of planting. Deciduous trees shall be fully branched, have a minimum caliper of 1 1/2 inches and a minimum height of 8 feet at time of planting. Seedlings are not permitted.

c. All retained trees located on lots shall be identified with a permanent tree tag at breast height.

3. Significant Trees. At a minimum, 30 percent of significant trees on site shall be retained, preferably reflective of the diversity of species and age within the stand, up to the minimum tree density requirements. All retained significant trees shall be shown to be windfirm. Where a sampling method is proposed for treed project sites, standards shall follow accepted industry methods as determined by a Professional Forester or licensed Landscape Architect.

Table 18J.15.030-1. Significant Trees
Tree Species	Size
Garry (Oregon White) Oak (1)	8" d.b.h. or greater
Pacific Yew	5" d.b.h. or greater
Pacific Madrone	10" d.b.h. or greater
Ponderosa Pine, Grand Fir, Big Leaf Maple, Western Hemlock, Western Red Cedar, Shore Pine, Western White Pine	15" d.b.h. or greater
Douglas Fir, Sitka Spruce	24" d.b.h. or greater
Legacy Tree (any species)	40" d.b.h. or greater

Footnote:

1See also habitat protection standards for Oregon White Oak trees/stands in 18E.40.020 D. and 18E.40.040 C.

1. General. The following minimum tree unit densities apply to new development activities. Use net developable acreage of the project site to calculate density:

Table 18J.15.030-2. General Minimum Tree Unit Density (1)
Classifications per PCC 18A.10.080	Tree units per acre
Employment Centers	5 tree units/acre
Urban Centers and Districts, Rural Centers	20 tree units/acre
Urban Residential (2)	30 tree units/acre
Rural Residential (3)	40 tree units/acre
Resource Lands and other zones	Not Applicable

Footnotes:

1If the calculation results in a fractional quantity, it shall be rounded to the nearest whole number (greater than or equal to 0.5 is rounded up; less than 0.5 is rounded down).

2Non-residential uses, other than schools, permitted within Urban Residential zones shall be subject to a required tree unit density of 20 tree units/acre.

3Non-residential uses, other than schools, permitted within Rural Residential zones shall be subject to a required tree unit density of 20 tree units/acre.

a. For expansion on legally established civic, utility, commercial, industrial, and multi-family properties that do not conform to the tree density requirements, the following tree conservation requirements shall apply:

(1) A minimum of 1 tree unit shall be provided for each 500 square feet of building or use area expansion; and

(2) A minimum of 3 tree units shall replace each tree unit removed, up to a maximum of 25 tree units per acre.

b. For properties with an approved Tree Retention Plan, the applicant shall provide:

(1) Information to explain how the removal of tree conservation trees cannot be avoided;

(2) Replacement trees for each tree unit lost, based upon tree size at the time of removal; and

(3) A revised plan demonstrating that no net loss of tree units will occur.

3. Schools. Schools shall be subject to a required tree unit density of 10 tree units per acre in all zones.

4. Rural Residential Land Division. Rural land divisions that result in the creation of residential lots each having a minimum lot size of 5 acres or 1/128th of a Section or larger; or residential lots of less than 5 acres where the density of the land division is 0.2 dwelling units per acre or less, shall have the following special standards:

a. For project sites containing forest, at least 50 percent of forested area shall be retained. If the retained forest area does not achieve 50 percent forest site coverage within the division, additional tree plantings shall be provided to achieve such coverage. Forested areas shall meet a minimum tree unit density of 40 tree units per acre. Additional tree planting shall be provided as necessary to achieve this tree density.

b. In order to preserve agricultural opportunities, where a project site is historically non-forested or pasture, and has been for over 20 years, as documented by aerial or ortho photography, tree unit density requirements shall not be required.

H. Standards – Tree Unit Credits. Tree unit credits for the retention and planting of trees shall be awarded as follows:

Table 18J.15.030-3. Tree Unit Credits
Tree Category	Tree Unit Credit
Existing Tree 1" to 6" d.b.h.	1.0 tree unit per tree retained
Existing Tree > 6" ≤ 12" d.b.h.	1.5 tree units per tree retained
Existing Tree > 12" ≤ 18" d.b.h.	2.0 tree units per tree retained
Existing Tree > 18" ≤ 24" d.b.h.	2.5 tree units per tree retained
Existing Tree > 24" d.b.h.	3.0 tree units per tree retained
Significant Tree < 24" d.b.h.	2.5 tree units per tree retained
Significant Tree ≥ 24" d.b.h.	3.0 tree units per tree retained
Legacy Tree	10 tree units per tree retained
Replacement Tree – 2-1 Seedling (1)	0.25 tree units per tree planted
Replacement Tree – Coniferous ≥ 4' in height, Deciduous ≥ 1.5" caliper	0.75 tree units per tree planted

Footnote:

1Seedlings shall not be credited toward tree unit density requirements if placed on lots. (See PCC 18J.15.030.F.2, Standards – General – Residential Lot Location.)

a. Trees to be retained on site must meet the following minimum standards to be credited toward the tree density requirements of this Section.

(1) Post-development life expectancy of greater than 10 years;

(2) Relatively sound and solid trunk with no extensive decay or hollow and no significant trunk damage;

(3) No major insect or pathological problem;

(4) No significant crown damage;

(5) Full branching and general proportionality in height and breadth for the tree age; and

(6) Individual trees and groupings of trees proposed for retention must be wind-firm in their post-development state.

b. Trees identified as having significant habitat value (i.e., Legacy Trees, snags, or nesting trees) and those located within a critical area or its buffer may be credited toward the tree density requirements, regardless of the health or state of the tree.

c. Trees should be selected for retention based upon a consideration of windthrow potential, wildlife value, aesthetics, and compatibility with future development.

d. Narrow strips of trees along a parcel's perimeter boundaries should be avoided due to windthrow potential, consistent with applicable standards as prescribed in the Pierce County Code.

e. An evaluation of individual tree health is required for trees that will be within 1.5 tree lengths of proposed structures, improvements, or roads.

2. Replacement Trees. Each tree proposed for planting must meet the following minimum standards to be credited toward satisfying the tree density requirements of this Section.

a. Developments shall locate a minimum of 25 percent of the required trees in protected tracts, such as tree conservation tracts, recreation tracts, stormwater tracts, and critical area tracts;

b. Trees shall be free from injury, pests, diseases, and nutritional disorders and must be fully branched and have a healthy root system;

c. Trees utilized for planting shall be a minimum 2-1 seedling size, unless a larger size is specified;

d. Trees planted shall include a mix of coniferous and deciduous trees, with a minimum of 30 percent coniferous, unless the area is deemed to have been Oregon white oak habitat, in which case the standards in Title 18E PCC, Development Regulations – Critical Areas, shall apply;

e. Replacement trees proposed to be planted within open space, greenbelts, native buffer areas, and landscape areas, such as street trees, must be compatible with the intended growing location;

f. Individual species of replacement trees planted shall not exceed 25 percent of the total number of all replacement trees;

g. Irrigation shall be provided until the tree is established; and

h. Trees may be planted on a solitary basis or within clusters to form stands.

1. When lots or building sites are located next to protective tracts (such as park, stormwater, or critical area tracts), the preferred location of the trees is the area adjacent to these tracts.