21-100017_Calculating Tree Units -LOT 9087_1-4-21_V1Bulletin #073 – June 8, 2016 Page 1 of 1 k:\Handouts\Calculating Tree Units
CALCULATING TREE UNITS
This form can be used to demonstrate how you will meet the minimum tree unit requirement for
your site and should accompany your submittal. Trees to be retained or planted must also be
shown on your submitted site plan, or a separate tree plan.
________________ ÷ 43,560 (sf/acre) = ___________ x 25 (units/acre) = ________________
(lot size in square feet) (lot size in acres) (minimum tree units)
Existing Trees
Includes all trees except invasive species and hazard trees
Tree Size (diameter at breast height /4.5′) # of Trees
to Remain Tree Units Total Units
1″ to 6″ dbh x 1.0 =
> 6″ to 12″ dbh x 1.5 =
> 12″ to 18″ dbh x 2.0 =
> 18″ to 24″ dbh x 2.5 =
> 24″ dbh x 3.0 =
Total Existing Tree Units to Remain
Replacement/Additional Trees
Evergreen Trees – minimum 6′ in height at planting
Deciduous Trees – minimum 2″ caliper at planting
Large Canopy = 1.5 Tree Units Medium Canopy = 1 Tree Unit Small Canopy = .5 Tree Units
Tree Species Canopy
(Sm/Med/Lg)
Tree
Units # of Trees Total Units
=
=
=
=
=
=
Total Proposed Tree Units to be Added
Total Existing and Proposed Tree Units
DEPARTMENT OF COMMUNITY DEVELOPMENT
33325 8th Avenue South
Federal Way, WA 98003
253-835-2607; Fax 253-835-2609
www.cityoffederalway.com