Environmental Services
Tree Replacement Guidelines
As approved in July 1993 by:
Alice Foster, Director, PRCR
Sam Kem, Director, DPW
Dan Boring, Acting Director, DES
Joan Linderman, Acting Director, CPHD
Hank Leavitt, Acting Director, OSS
1. GENERAL STATEMENT
Trees are routinely lost from publicly owned and maintained areas for many reasons including infrastructure maintenance and new construction by the County. This document provides guidelines for the replacement of trees affected by these types of projects. Removal or replacement of trees within rights of way associated with private development are governed by provisions within the County Code, site plan conditions, or other County policies and/or procedures.
2. STREET TREES
Statement: A number of street trees will be designed into each County street improvement project to reforest or afforest the appropriate sections of the right-of- way based on spacing and other conditions, regardless of the number of trees removed. Appropriate species, quantities and sizes will be suggested by DPRCR in accordance with Administrative Regulation 4.3 or its addenda.
An evaluation of potential tree loss will be made prior to removals to determine if this reforestation or afforestation represents reasonable compensation for the total value of the lost resource. To assist in that evaluation the following criteria shall be used:
As a minimum, trees of 10" caliper or less that are removed from the rights-of-way will be replaced on a one-for-one basis.
Significant trees (caliper greater than 10") will be replaced at a rate derived from a formula of the International Society of Arboriculture (see attached).
Where there is not adequate room in the rights-of-way to replace the required number of trees within the project limits, the excess trees will be "banked" and planted during the following fall planting season at locations which are mutually agreeable to the originating agency, DPRCR and citizens. Attempts will be made to plant trees as close to the original project site as possible. Trees will be replaced preferably onto street rights-of-way in the same neighborhood (civic association), in a park or on other public property if spaces are not available along streets. Trees lost from public rights-of-way will not be replaced onto private property.
3. PARKS, OPEN SPACES, OTHER PUBLIC PROPERTIES
Statement: The guidelines are identical to the ones above, with the exception that shrubs and ground cover will also be designed into the reforestation, and replacement trees which cannot be placed at the project site will go back into parks, open spaces or other public properties (as opposed to rights-of-way) from a DPRCR priority list.
4. PRIVATE PROPERTY
Statement: Trees removed from private property as part of a project will be replaced onto the same property using the same formula as above.
5. TREE REPLACEMENT FORMULA
A. Definitions
Diameter | Trunk diameter at four and one half feet above the ground. |
Species | All tree species given a value from 1 to 100 which is expressed as a percentage of 100 (e.g. 40 = 40% = .4). This is a value assigned to a species according to a number of factors including longevity, durability and appropriateness to the growing zone. |
Condition | Rating from 0 (dead) to 100% (perfect) and is expressed as a percentage of 100 (e.g. 100% = 1, 60% = .6, etc.). |
B. Procedure
Scoring is determined by the multiplication of Diameter X Species X Condition. Shown below are three applications of the formula.
1. A 10" American Holly is automatically replaced with one tree, according to category 1, A. of the above policy.
2. A 40" Silver Maple (species rating of 40), rated at 60% condition
is scored as 40 X .4 X .6 for a total score of 9.6.
3. A 36" White Oak (species rating of 80), rated at 70% condition
is scored as 36 X .8 X .7 for a total score of 20.16.
C. Application to Replacement Policy
Trees are replaced at the following rates, based on the overall scores:
Rating: | 1 – 4.9 | = | 1 tree |
| 5 – 9.9 | = | 2 trees |
| 10 – 14.9 | = | 3 trees |
| 15 – 19.9 | = | 4 trees |
| 20 – 24.5 | = | 5 trees |
| 25+ | = | 6 trees |
In the examples above, the American Holly is replaced with one tree, the Silver Maple with two trees, and the White Oak with five trees.
The formula should only be used by qualified individuals, i.e. professional arborists, with the knowledge of tree condition determinations and species factors.
Example #1 | ||||||
Species | Number | Dia. (") | Condition | Species Rating | Total Score | Replacements |
Maple | 1 | 4 | 1 | |||
Oak | 1 | 12 | .8 | .7 | 6.72 | 2 |
Dogwood | 1 | 6* | 1 | |||
Sycamore | 1 | 8* |
| 1 | ||
Sycamore | 1 | 30 | .4 | .7 | 8.40 | 2 |
Locust | 2 | 6* |
|
| 1(x2) | |
Locust | 5 | 8* |
|
| 1(x5) | |
Locust | 1 | 10* |
|
| 1 | |
Locust | 1 | 12 | .4 | .6 | 2.88 | 1(x2) |
Locust | 1 | 15 | .4 | .6 | 3.60 | 1 |
Ash | 1 | 8* |
| 1 | ||
Mulberry | 1 | 4 |
| 1 | ||
In this example, 18 trees are lost 1173 caliper inches) and 20 trees replaced, since two of the trees being removed warrant greater than one-for-one replacements. However, a 36" Sycamore is also at risk; if it dies, it would be replaced with four trees:
Sycamore | 1 | 36 | .7 | .7 | 17.64 | 4 |
* - Trees 10" DBH and smaller are automatically replaced at a rate of one for one, according to the policy.
Example #2 | ||||||
Species | Number | Dia. (") | Condition | Species Rating | Total Score | Replacements |
Cedar | 1 | 20 | .5 | .4 | 4.00 | 1 |
Cherry | 1 | 18 | .5 | .4 | 3.60 | 1 |
Holly | 1 | 4* | 1 | |||
Linden | 1 | 27 | .8 | .6 | 12.96 | 3 |
Ash | 1 | 18 | .7 | .6 | 7.56 | 2 |
Ash | 1 | 24 | .7 | .4 | 6.72 | 2 |
Am. Elm | 1 | 15 | .4 | .6 | 3.60 | 1 |
Am. Elm | 1 | 27 | .4 | .3 | 3.24 | 1 |
Am. Elm | 1 | 27 | .4 | .3 | 3.24 | 1 |
Am. Elm | 1 | 8* | 1 | |||
Linden | 1 | 21 | .8 | .6 | 10.08 | 3 |
In this example, 11 trees are lost (209 caliper inches) and 17 trees replaced, since four of the trees being removed warrant greater than one-for-one replacements. However, the trees listed below are also in the project area and considered to be at risk; if they die before construction is completed they would be replaced as follows:
White Pine | 1 | 24 | .4 | .6 | 5.76 | 2 |
Holly | 1 | 16 | .4 | .6 | 3.84 | 1 |
Magnolia | 1 | 20 | .8 | .8 | 12.80 | 3 |
Maple | 1 | 10* | 1 | |||
Magnolia | 1 | 24 | .7 | .8 | 13.44 | 3 |
Crab | 1 | 16 | .7 | .8 | 8.96 | 2 |
* - Trees 10" DBH and smaller are automatically replaced at a rate of one for one, according to the policy.
Note: The above examples are for illustrating the application of the formula and do not necessarily represent an actual project.
