HomeMy WebLinkAbout23_Tree-Retention-WorksheetDEPARTMENT OF COMMUNITY
AND ECONOMIC DEVELOPMENT
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TREE RETENTION WORKSHEET
Planning Division
1055 South Grady Way‐Renton, WA 98057
Phone: 425‐430‐7200 | www.rentonwa.gov
1. Total number of trees over 6” diameter1, or alder or cottonwood
trees at least 8” in diameter on project site 69 trees
2. Deductions: Certain trees are excluded from the retention calculation:
Trees that are dangerous2 trees
Trees in proposed public streets 11 trees
Trees in proposed private access easements/tracts 31 trees
Trees in critical areas3 and buffers trees
Total number of excluded trees: 42 trees
3. Subtract line 2 from line 1: 27 trees
4. Next, to determine the number of trees that must be retained4, multiply line 3 by:
0.3 in zones RC, R‐1, R‐4, R‐6 or R‐8
0.2 in all other residential zones
0.1 in all commercial and industrial zones 9 trees
5. List the number of 6” in diameter, or alder or cottonwood trees
over 8” in diameter that you are proposing5 to retain4: 27 trees
6. Subtract line 5 from line 4 for trees to be replaced:
(if line 6 is zero or less, stop here. No replacement trees are required) 0 trees
7. Multiply line 6 by 12” for number of required replacement inches: 0 inches
8. Proposed size of trees to meet additional planting requirement:
(Minimum 2” caliper trees required) 0 inches per tree
9. Divide line 7 by line 8 for number of replacement trees6:
(If remainder is .5 or greater, round up to the next whole number) 0 trees
1 Measured at 4.5’ above grade.
2 A tree certified, in a written report, as dead, terminally diseased, damaged, or otherwise dangerous to persons or property by a licensed
landscape architect, or certified arborist, and approved by the City.
3 Critical areas, such as wetlands, streams, floodplains and protected slopes, are defined in RMC 4‐3‐050.
4 Count only those trees to be retained outside of critical areas and buffers.
5 The City may require modification of the tree retention plan to ensure retention of the maximum number of trees per RMC 4‐4‐130H7a.
6 When the required number of protected trees cannot be retained, replacement trees, with at least a two‐inch (2") caliper or an evergreen at least
six feet (6') tall, shall be planted. See RMC 4‐4‐130.H.1.e.(ii) for prohibited types of replacement trees.
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Minimum Tree Density
A minimum tree density shall be maintained on each residentially zoned lot (exempting single‐family
dwellings in R‐10 and R‐14). The tree density may consist of existing trees, replacement trees, or a
combination.
Detached single‐family development7: Two (2) significant trees8 for every five thousand (5,000) sq. ft. of lot
area. For example, a lot with 9,600 square feet and a detached single‐family house is required to have four (4)
significant trees or their equivalent in caliper inches (one or more trees with a combined diameter of 24”). This
is determined with the following formula:
Multi‐family development (attached dwellings): Four (4) significant trees8 for every five thousand (5,000) sq.
ft. of lot area.
Example Tree Density Table:
Lot Lot size Min significant
trees required
New Trees Retained Trees Compliant
1 5,000 2 2 @ 2” caliper 0 Yes
2 10,000 4 0 1 tree (24 caliper
inches)
Yes
3 15,000 6 2 @ 2” caliper 1 Maple – 15
caliper inches
1 Fir – 9 caliper
inches.
Yes
7 Lots developed with detached dwellings in the R‐10 and R‐14 zoned are exempt from maintaining a minimum number of significant trees onsite,
however they are not exempt from the annual tree removal limits.
8 Or the gross equivalent of caliper inches provided by one (1) or more trees.