5.4.9 Tree Retention and Tree Planting

5.4.9.1 BMP Description

Tree retention and tree planting (BMP T5.16 in Volume V, Chapter 11 of the Ecology Manual) entails the planting of new trees and/or protection of existing trees and retaining them on a project site to achieve on-site stormwater management and/or flow control credits. See Title 17 KCC for discussion of tree retention.

5.4.9.2 Performance Mechanism

Trees provide flow control via interception, transpiration, and increased infiltration. Additional environmental benefits include improved air quality, carbon sequestration, reduced heat island effect, pollutant removal, and habitat preservation or formation.

5.4.9.3 Application and Limitations

Retained and newly planted trees can be used to help meet the LID Performance Standard for on-site stormwater management and flow control requirements (Table II-5.13). The degree of flow control that can be provided depends on the tree type (i.e., evergreen or deciduous), maturity, canopy area, and whether or not the tree canopy overhangs hard surfaces. This BMP can be applied to meet or partially meet the requirements listed below.

Table II-5.13. Tree Retention and Tree Planting Applicability.

BMP	MR #5: On-site Stormwater Management		MR #6: Runoff Treatment				MR #7: Flow Control
	List	LID Performance Standard	Basic	Enhanced	Oil Control	Phosphorus
Tree Retention and Planting		X					X

5.4.9.4 Site Considerations

Setbacks of proposed infrastructure from existing trees are critical considerations. Tree protection requirements limit grading and other disturbances in proximity to the tree.

Existing tree species and location shall be clearly shown on submittal drawings.

Trees shall be viable for long-term retention (i.e., in good health and compatible with proposed construction).

See BMP T5.16 in Volume V, Chapter 11 of the Ecology Manual for additional site considerations.

5.4.9.5 Design Information

A recommended street tree list is included in Appendix B of the Kitsap County Low Impact Guidance Manual (Kitsap Home Builders 2009).

See BMP T5.16 in Volume V, Chapter 11 of the Ecology Manual for design guidance, requirements, hydrologic modeling credits, and guidance for Runoff Model Representation for retained trees and newly planted trees.